Flexographic printing is a widely used process and it is used for longer times. This technique used to maintain the printing and it provides amazing graphics and it is one of the best printing methods.
The flexo technology is developed to print small highlight dots and to achieve better solid ink density. Also, the broadest color gamut, tonal range, and image contrast are evaded in the quest for offset and gravure class printing. It is very hard to print with the above characteristics at high speed and with minimal stoppage.
One solution is effective ink transfer with minimal print impression. The effective transfer is achieve by bringing a sufficient amount of ink to density and opacity. With minimum anilox volume and use ink where it is required. With this solution there is less dot gain and plates will run longer without cleaning.
What is the Obstacle?
The better ink transfer does not mean getting as much ink on the substrate. The stronger density and cleaner print make the broader color gamut. But remember, too much density reduces the range of colors and too much ink reduces the tonal range which will be printed. This reduces the contrast and appearance of the work. There should be print with target levels of high density or opacity for the broadest color gamut and tonal range.
To implement this on the machine the entire mechanism of ink transfer, ink pulling from anilox roller, and transferring needs to be optimized.
There are many factors which are influences like:
- Properties of the plate surface
- Plate material
- Shape and condition of the anilox roller
- Environmental conditions
- Ink and substrate dyne levels
There are many technological developments to improve and refine the process. The ink manufacturers play an important role by optimized pigment load, viscosity, pH, and others. Also, the anilox manufacturers offer a wide range of cell shape and size, ceramic materials and continuously develops new lasers and engraving. There are new substrates and coatings are available. The new converters utilize flame and treating to improve the laydown of ink and adhesion.
The important factor for improved ink transfer is flexographic plate technology. Various plate suppliers offer plate surface texturization through imaging or mechanical by designing to spread ink more efficiently than to build a thicker film. Each of these improvements makes density or opacity better but has not able to drive expanded gamut, tonal range, and contrast. These have maximum press throughput or better ability to cover the substrate with ink.
What is the Ink Transfer Problem?
It is the solid black ink patch print on the clear film and shows gaps, pinholes, or voids. The cause behind this is the dyne levels of material and properties of the ink. The primary reason for this is the separation of the anilox cells by cell walls. As the cell contents are deposited onto the plate surface, the ink runs into machine direction due to rotation of the press. This can be solve by adding more ink volume and press harder on the plate.
What is the Solution?
The solution is digitally apply the micro-surface texturization of the plate. There are advance plate pattering options which include six patterns that play an important role in controlling the ink flow at the edge of objects.
This is digitally controlled and unlike plates with fixed surfaces, it has large target areas and it is applied where needed. The patterns are engineer with increasing anilox volumes. This is select on the basis of ink/anilox/substrate/tape for sufficient ink transfer. To process the print the finest surface patterns are select with a lower volume of the anilox roll. For spot colors, it advised selecting larger patterns where anilox volumes carry twice the amount of ink required for process work. Also, there are larger patterns for whites, coatings, and adhesive which can be used two to three times or more.
This specific plate can create for spot colors, whites, adhesives, metallics, etc. using only one polymer type. With this, specific plates can combine on one sheet. Less number of plate materials eliminates the possibility of the wrong type. Also, it utilizes and reduces the processing time require for creating plate types.
The digital image feature uses the carrying and spreading of ink for producing string density in halftones, solids, and text areas and applies a smaller pattern on all edges to apply ink only where required. This is very beneficial as it keeps the print edges sharp and clear and also prevents reverse text.
The technology allows the ink to apply where it needed and stop were not. This results in superior ink coverage with maximum color gamut and tonal range. It opens the mid-tones and three-quarter tones which gives a realistic, continuous tome that truly enhances shelf impact.
Conclusion
Effective ink barrier technology requires advance imaging and reproduction capabilities. It can operate at 2400 dpi but create each pixel in 4 by 4 matrix and consists of 16 laser spots. When it is the couple for plate making process, it enables 1:1 reproduction of image files. And also it ensures the image pattern will be fully accurate on the plate every time.
In conclusion, effective ink transfer with minimum impression is the main for offset and gravure class flexo printing. It is only possible by using a minimum amount of ink to fully cover the surface without filling the non-print area or it causes excess dot gain.
