Packaging Printing Ink Technology Development and Prospects (2)

Second, waterless offset ink: to achieve the ink balance
The hardest part of offset printing is to achieve the correct ink-water balance. Too much water can wrinkle the paper and thin the ink film transferred to the paper. Too little water can make the ink uncontrollable and transfer to the non-graphic area. The ink-to-ink ratio also affects the viscosity of the ink. In the case of multi-color printing, there is also a problem of how to control the post-printing ink to superimpose the previously printed ink. It is not easy to achieve the correct ink-water balance. The balance of ink and ink is influenced by various factors such as temperature, humidity, paper type, and printing speed. Waterless offset printing brings many benefits because there is no ink-ink balance.
One of the major problems with waterless offset printing is humidity control. The viscosity of the ink varies with temperature and is only rejected by silicon in a narrow range of viscosity. During the printing process, the ink will heat up due to the friction between the ink rollers. When the temperature rises to a certain degree, the ink viscosity will become thin and the printing plate will become dirty. If there is no self-cooling effect, perhaps the same problem will occur on a conventional offset press. The self-cooling effect causes the ink roller to pick up fine water droplets from the plate. The water droplets float on the ink film and return to the ink roller. When the water evaporates, the ink is cooled. To stabilize the ink viscosity, one solution is to use a special ink, which can maintain a constant viscosity over a wide temperature range; another trick is to use a thicker ink during the long live printing process. The real solution, however, is to pump coolant through internal tubes on some of the rollers to stabilize the ink temperature. This method will add considerable cost to the new press, which is a purely expensive modification to the old press. In any case, this method can use the same ink and the same operating technology for the short live and long live.
Since no water weakens the ink film, waterless offset printing can have higher ink density on the printed page, so the printed image has a larger color gamut, and a four-color waterless offset proof looks like on a conventional offset printing press. Printed six-color print job. Other advantages of waterless offset printing include shorter print setup time and less paper waste (this is especially important for digital short-range digital imaging on the fly), there is no problem with the removal of excess fountain solution addenda, and printing There is only a small amount of volatile organic compounds in the air of the workshop. In order to be able to use waterless offset printing, even the fact that the aforementioned chill roll is equipped even on conventional printing presses becomes more and more common. This fact shows that even though waterborne offset printing has increased its operating costs, it can still be accepted by users.
When most successful waterless offset systems use special plates. There are 3 companies developing special inks. In fact, only one type is a true waterless offset ink, but all three ink products have the advantage of eliminating the need to adjust the ink balance when printing.
1、Single-Fluid (single fluid) ink
Gauss has demonstrated Single-Fluid inks at Print 97, and the technical details have remained confidential. The concept is that traditional oil-based inks are emulsified with water and the emulsification process is achieved by a device that is mounted on a printing press and resembles a stirrer. The emulsified emulsion (Pigmented mayonnaise) is then added to the ink roller of the printing press. When it reaches the printing plate, the emulsion separates into components of water and oil. Goss did not demonstrate its single-fluid ink technology at Drupa 2000, but it is said that the technology is still under development and tested in a newspaper in the autumn of 2000. Gauss has already registered "Single-Fluid" as a registered trademark.
2. Water based ink
Heidelberg cooperates with Sun Chemical to develop a water ink. Technically speaking, this product does not belong to waterless ink but is an oil-less ink. However, like waterless inks, this ink avoids ink balance problems and it also has environmental benefits.
Heidelberg's inks require a silicon-containing plate to allow the non-imaged areas to repel ink. In addition, it also requires the printer to have a temperature control roll, but not a chill roll. This ink needs to heat the roll to 35°C, collecting heat to evaporate excess water from the ink, and when the ink is attached to the plate, the final The total water content is 1%-2%. Although this temperature value is not very strict, it can be varied within the range of 10°C but it must be controlled. If the water evaporates too much, the ink hall will dry on the ink roller; if the water evaporates too little, the printing plate will be dirty when printed. It is said that the ink will be heated to dry at 40°C, and if dried, it will have water resistance. When the ink is heated and immediately becomes dry enough, no need to spray (Printer usually removes talcum powder from the newly printed sheet to prevent the ink from reaching the surface of the next sheet and the back of the sheet from being stained. ). After 5 minutes, the ink was dry to the extent that the printer and the sheet were hand-carried; after 15 minutes, the ink was dry enough to allow the printer to fold the sheet. In addition to the benefits of environmental protection, the performance of the water-tomb ink has the same viscosity and viscosity as conventional inks, as expected by the printer, and produces the same maximum solid ink density on the page. At first, its price may be twice that of waterless offset inks now, but in the future its price will depend on the amount of ink produced.
3, Flint Single Fluid ink
Flint Ink's deepest impression is Flint Single Fluid ink. It can be used on conventional uncooled presses for traditional lead plates and polyester plates. Such inks are similar to conventional printer inks in terms of odor, appearance and printing. Except that the bucket is empty, it is operated completely according to the traditional offset printing method. On the DruPa 2000, Flint printed samples on a small Ryobi four-color field brush machine. According to Flint, its ink (trademark “SF1”) can achieve a high density on paper, with each color being about 10% higher, but if more than 10%, the ink is loose and easy to make the plate dirty . About 15 minutes later, the ink can be felt dry by hand, but as with conventional inks, it takes several hours to completely dry (up to folding or double-sided printing). Some people, after taking samples for a few days, used rubber, eraser spirits, alcohol, acetone, gasoline, and other solvents to test on proofs to prove that the ink would not be rubbed off. The formulation of this ink is confidential and it is said that it is not an emulsion but a true waterless offset ink. It has also been heard that its composition makes its price not more expensive than conventional inks. Despite this, SF1 inks are still commercially sold in about one year. Flint will conduct a full field test at several selected printing plants. It will also develop and test a set of spot color inks. Now they have only CMYK primary inks and a special black ink for heat-curing journal printers.
Third, the development of ink high-tech direction
1, security ink: to achieve special printing needs
At present, many of the anti-counterfeiting inks used in China's tobacco and alcoholic products include the following two: First, the invisible anti-counterfeit labels are printed on paper or plastic film using fluorescent anti-counterfeiting inks, including green, red, yellow and other fluorescent invisible Ink; The second is the use of temperature change security ink, can be blue, purple red, black colorless.
In order to meet the needs of the market, a daylight-type color-changing fluorescent anti-counterfeiting ink and a hand-type color-colored fluorescent anti-counterfeiting ink that can be used for tobacco and wine packaging are introduced to the market. The following are the main features: First, the use of daylight-type color and hand temperature-type color-changing Science and technology materials have controllability of raw materials. The second is that the ink has many components, many production equipments, large investment, complicated process, and difficult processing, and it is difficult for most people to copy. The third is to have multiple anti-counterfeiting features, such as intuitive, daylight discoloration, hand temperature discoloration; concealed, fluorescent discoloration. The fourth is the convenience of identification. It can be identified by sunlight or hand temperature heating, and a common UV lighter can also be used.
This new type of anti-counterfeit ink has the following technical characteristics: First, it adopts the principle of chemiluminescence and buys the uniqueness of fluorescent detection. According to the customer's needs, special patented fluorescent compounds are used, and the unique fingerprint identification function and unique spectrally characterized inks are used to protect the product from false alarms. Second, the stability of white-light discoloration and hand-warming color fluorescent materials is high, which overcomes the common aging-resistant characteristics of existing anti-counterfeiting inks. The third is the specificity of the proprietary anti-counterfeiting ink formulation lock for commodity brands, that is, according to the needs of customers, the purpose of product protection is to use unique anti-counterfeit ink products that can be characterized. Fourth, a new type of security ink can directly print invisible or colored anti-counterfeit graphics on coated paper such as alcoholic drinks and tobacco, cardboard, plastic films and other materials.
2, electronic ink: to achieve digital offset
Indigo's color digital offset presses provide a unique combination of features based on its color digital offset press technology and operation. In digo presses use electronic inks unique to Indigo's unique liquid inks. The electronic ink contains charged liquid ink particles, which makes it possible to electronically control the placement of printed particles in the digital four brushes. The electronic ink can reach extremely small particles (1-2 micron), so that small particles can be printed with higher resolution and smoothness, sharpening the edges of the image, and forming an image layer of pole Pu.
(1) Standard basic color CMYK (cyan, magenta, yellow, black);
(2) The wide color gamut six-color setting increases orange red and purple, so that the color reproduction capability is much higher than the color reproduction ability on the basis of the original four colors;
(3) PANTONE compatible IN DIGO spot color system;
(4) The opaque white coating of the colorless printing material;
(5) Fluorescent ink.
This digital offset technology, with its advantages such as electronic ink, has achieved many advantages:
(1) Edge sharpness and sharpness. It can be clearly seen from the high-magnification results that the image formed by the electronic ink has a sharper degree of sharpness than the image formed by the electrostatic copying powder, and this advantage is more obvious in the continuous adjustment of the image. The sharpness of the electronic ink image is sharper at the edges of the continuous faded image of the intermediate color or the finely printed text image. Electronic ink images are also worth noting in a clean, non-polluting background. This advantage comes from the fact that electronic ink particles and electronic ink particles are transferred during printing.
(2) Dot gains and color consistency. Dot enlargement refers to the tendency of printed continuous blended line images to spread under embossing. Indigo digital color offset printers can control dot gain. Indigo presses have a calibration function that allows printed dots to be within the required range. In addition, Indigo's printing machine automatically adjusts the optimal density (such as the darkness of the appearance) and the dot size so that each print has the same appearance.
(3) Image smoothness. Many people think that the quality of offset printing lies in the degree of smoothness of the image. This is actually not the case. The key to quality lies in the uniformity of the image. Indigo presses, unlike electrostatic dry powder printers or copiers, can only output images with the same smoothness regardless of the material of the paper. This results in varying degrees of smoothness (such as solid dry powder coverage) and highlighted areas (not covered) in dark areas. Dry powder covered area). The electronic ink image matches the smoothness of the substrate and, like a conventional offset press, produces effects ranging from rough to light to high brightness. According to different figures and the smoothness characteristics of the offset press, the actual operation shows that the ideal smoothness of the electronic ink can basically meet the requirements of various papers other than super-glossy paper. For moderately smooth paper, electronic ink is more advantageous than lithographic ink, but lithographic ink is more advantageous in the field of smooth paper.
(4) color difference. Electronic ink can be printed according to international color standards. These standards are based on the four-color standard basic color CMYK (cyan, magenta, yellow, black). Lithography uses different ink formulations according to different standards, while electronic ink uses only one set of colors for different standards. The electronic ink adjusts the density of ink (color concentration) through electrons to suit different needs. The special properties of electronic ink and the charging characteristics of its ink determine its unique features on a four-color basis. In addition to printing the four-color basic color, the electronic ink of the spot color system expands the color gamut to a color gamut that cannot be achieved by the four-color basic color. The spot color ink system is capable of six-color printing, and imaging uses a primary transfer technology.
(5) Instant drying. Because of electronic ink