SMI Labels and Packaging Materials

Friday, November 1, 2019

Selecting Digital Label Printing technology

Change is the only constant in life.” This is an age old saying and it is so true! As we look back in

time that has gone by, the evolution in technologies that impact our life is amazing and for the new generations it is difficult to imagine the path traversed by elders. For example, look at the development in telephony and communications; there was a time when, to get a telephone we had to make a lengthy application with documents plus a hefty deposit and then wait for 3 years to get a telephone. For dialing national or international numbers one had to book a call and experience endless wait to be connected for a 3 minute call. Those who did not have telephone connections had to visit a post office to call relatives in other cities, book a call and wait for their turn until the operator tried to connect them for a call that they had to pre-declare the duration as 3 minutes or 6 minutes. Mobiles have transformed life and we have instant voice and video communication capabilities 24X7 with multiple phones in our pockets. The mobile is perhaps the most impactful technology experienced by us in life so far. In a somewhat similar manner, printing technologies have evolved over hundreds of years to bring changes enabling perfection and colourful meaning to all printed products. A technology that began with carving stone blocks, apply colours and transferring images, evolved to using wooden blocks, metal type sets, letterpress printing, screen Printing to offset printing, a technology that was widely adopted and spread across the world as the most preferred print process. Also evolved flexographic and rotogravure printing. All these technologies had a costly pre-press and make-ready process as also the cost of artworks, plates, print cylinders, etc.

The 1970s saw the beginning of an era that would continue to impact the print industry in a totally different tangent, the digital printing! The technology enabled printing with a command from a computer with press of a button without much of processes that were needed in conventional printing. It is so much like the changes in mobile phone technology coming about. By 1993 the digital printing technology developed such that the first commercial digital printing press named “Indigo” was produced by Benny Landa in his company with the same name. This transformed the printing world; one could now print personalized short run jobs straight from computer. In 2000-2001, the company Indigo was acquired by Hewlett Packard (HP) and at the time of acquisition Landa had said, “Our vision has always been to lead the printing industry into the digital era and to see Indigo technology pervade the commercial market. Now, a part of HP, that goal is in sight." Rightly so, the market of digital printing has been registering robust growth. Digital printing technology has been developed by various press manufacturers and is being widely adopted with innovative indulgence.  Label manufacturing is an integral part of print and has also been witnessing growth both in terms of total market as well as in Digital printing of labels. The global market for label printing has been growing steadily in recent times, valuing at $36.98 billion in 2017. As per Smithers Pira the total market of labels is likely to cross 49.9 Billion USD by 2024. According to Finat; 2017 was the first year that, with nearly 300 digital press installations, the volume of newly added digital label presses surpassed that of new conventional label press installed volumes.

While label printers in the western world have been early investors in digital label printing presses yet the Indian printers have been skeptical about the need for this investment in the Indian label production scenario. For this reason, until about 2015 most of the established label printers adopted the wait and watch stance toward digital printing of labels. However, in recent times we see the interest and investment towards this technology growing slowly and steadily, though the rate of growth in digitally printed labels is still small. Increasing number of printers have been seen studying the digital label printing technologies at labelexpos. Advantages of digital printing include speed, flexibility and low prepress costs, not requiring expensive plates shorter times to make ready. It is especially useful when printing variable data (numbering, bar- or QR codes, content variations, etc.).

The different types of technologies available leave the printers in a confusion as to what is the most appropriate technology that they should invest in. Unlike other conventional printing processes evolution of digital printing has moved into different technical ways of achieving the same goal which is computer to print.

Largely available technologies offered by various manufacturers of digital equipment are as follows;

1.       Dry toner based
2.       Liquid toner based
3.       Inkjet
4.       UV Inkjet

While looking at the selection of digital print process one also needs to decide the finishing of the labels whether they wish to do this inline or offline. Every different short run job maybe of varying shape requiring frequent stops and change of cutting dies. This substantially reduces press running time and impacts profitability adversely. In such a case it is advisable to finish the labels offline, one offline equipment can free up printing time of multiple presses. Laser die cutting is another option whereby it can handle multiple and frequent job changes without the need for additional dies and machine stoppages, but this calls for a much higher investment in the finishing equipment.  Additionally, one needs to decide with digital, what dpi resolution to go for; does the work need a white ink in one of the printing heads; does the press have an extended color gamut. Press running speeds of all the digital label press technologies vary quite considerably. The printing speed with many short-run job changes is also an important factor for consideration.

Dry Toner based process:

Chester Carlson inventor of Xerography
This process is an evolution of the earliest photocopying process known as Xerography invented by Chester Carlson founder of Xerox and converted as Laser printer by Gary Keith Starkweather in 1970s which transformed to digital printing with laser printers also called electrostatic digital printing as we have seen in our offices. In a laser printer a laser beam runs over an electrically charged drum preparing an electrical image carrying charged areas.  The drum is a cylinder coated with a material that becomes conductive when exposed to light or laser beam. Areas that are not exposed have a high resistance which allows these areas to hold the electrostatic charge necessary for the process. The image then collects the toner and transfers the image to a paper or substrate that is then heated to fuse the image on to it. In traditional xerography the image is formed by reflecting light off an existing document onto the exposed drum which then picks up the toner and transfers the image. Dry toners consist of pigments embedded inside polymer beads. The fusing phase of the electrophotographic process melts the polymer beads to the surface of the paper. These can print on both coated and noncoated papers. Image quality is a complex issue, determined by a combination of hardware, software, consumables and processes. Dry toner is not absorbed by the substrate, it always achieves an optimal optical density as all the ink transferred is adhering on surface. The particle size of the toner has been reduced over the years to achieve fine print results and most equipment are offering prints of 1200 DPI for solids and blends with good color depth and subtle contrasts, ideal to reproduce vibrant images.

Major brands offering dry toner based digital label presses are Xeikon and Konica Minolta.

Liquid Toner based process

Liquid toners also use pigments in polymer beads, but they are dispersed in oil that evaporates during fusing process. Liquid toners are used in digital presses that are typically used for commercial printing on a wide range of coated papers. Benny Landa an Israeli inventor mentioned above, having to his credit 800 patents produced the first Indigo digital printing press in the early 1990s using liquid toners in a process that was called liquid electrophotography or LEP in his company established in 1977. Landa came to be known as the father of digital printing. The liquid toner used by HP came to be known as ElectroInk, that combines the advantages of electronic printing with the qualities of liquid ink. ElectroInk contains charged pigmented particles in a liquid carrier. The image is created with electrophotographic process on the drum directly from digital data, avoiding the use of any analogue intermediate media. It starts with digitally created pages or print elements containing text, layouts or images. HP Indigo uses a blanket in between to transfer ink from the drum to media. The blanket is heated, melting and blending the ElectroInk particles into a smooth film. This produces an image that is completely defined on the blanket and transferred to the substrate by direct contact. For this reason, it is also referred to as offset digital printing.

Major brand using liquid toner based digital printing process: HP

Inkjet Printing

Inkjet printing is the oldest of technologies in non-contact printing evolving into digital colour printing commercially. Existing together there are two main inkjet technologies i.e. Continuous Inkjet (CIJ) and drop-on-demand (DOD). The CIJ method has been in use for ages in which a high-pressure pump directs liquid ink from a reservoir through a gun body and a microscopic nozzle, creating a continuous stream of ink droplets. These droplets are subjected to a varying electrostatic field and then these charged droplets pass through another electrostatic field to deflect them and form characters. The process can be understood by the image reproduced from Wikipedia. The Drop-on-demand (DOD) is divided into thermal DOD and piezoelectric DOD. Most commercial printers use the DOD to print. The large format ones use solvent or water-based inks depending on the equipment and the product. The inks used in digital inkjet label printing presses are water based and formulated with either dyes or pigments. Aqueous inks provide the broadest color gamut and most vivid colors. The water-based inks are inexpensive and may ultimately spell out as the lowest cost print, but some substrates may require specialized coatings as there is an imperative need for the ink droplet to sink straight in and not to smudge or smear. With growing volumes, increased environmental and consumer friendly nature of inks the coated stock prices are likely to become largely affordable making this technology to watch as wider acceptance is envisaged. Such inkjet printers can achieve high resolution of 1600 DPI. Since the start of a new millennium another water-based inkjet technology called Memjet has been evolving. Memjet is used in high speed, full colour printers to give a high-quality print at a very low cost. It uses a fixed print head unlike conventional inkjet printers where the cartridges or head moves back and forth during printing. The Memjet print head is fixed and is of the width of the material it’s printing on enabling edge to edge printing. This way it’s only the material that moves underneath the head as it’s printed.

Major brands using water based digital inkjet printing: Trojan from Astronova, Afina, Colordyne

UV Inkjet Printing

UV inkjet Digital printing is an extension of the inkjet printing that uses ultra-violet light to dry or cure ink. The inks consist mainly of acrylic monomers together with a photo initiator and after printing when exposed to strong UV lamps or in case of specially formulated inks to LED-UV light, the ink is cured by crosslinking. The ink due to this chemical reaction becomes instantly dried leading to increased printing speeds. The curing process with high power UV exposure for short periods of time (microseconds) allows printing on thermally sensitive substrates like BOPP and PE. Since the ink sits on top of the substrates and neither is dried by evaporation nor by absorption resulting a robust image on a wide range of uncoated substrates. It is the fastest growing sector of digital inkjet printing and more sustainable than conventional printing.

Major brand using digital UV inkjet printing: Canon, Domino, Durst, Epson, Screen, Xeikon

Short run labels with variable data
Selecting digital printing equipment for label printing is a complex task depending on the printer’s customer portfolio. It varies on many parameters, like the equipment price, ink price, media cost, media to be printed, consumables cost, speed of machine, resolution required, space and finishing required. Time is not far when printers will invest in multiple technologies to attain the best of each process and to service a wide array of customers. However to start with the print on demand feature is so very attractive and for short runs it seems to be becoming an absolute necessary at least in case of established printers whose large investments in high end flexo or combination presses gets held up doing shorter runs and taking away valuable production time. Since short run demands from brand owners continue to swell along with need for variable data, it becomes necessary to opt for an offline finishing equipment which does not slow down their printing capabilities.

Hybrid digital-flexo label press
Most of the leading label press manufacturers have started offering Hybrid machines with combination of Digital and flexo printing capabilities along with decorating and finishing inline. It is not a simple decision to opt for the hybrids. As mentioned earlier here, it all depends on the portfolio and requirements of individual label printers. It is interesting to note that all hybrid presses with digital capabilities displayed at Labelexpo Europe in September 2019 were fitted with UV inkjet digital presses. Leading press manufacturer who are offering Hybrids of flexo, digital and inline finishing include Gallus, Omet, Mark Andy, Nilpeter and MPS. With environmental concerns, migration of inks and other food or Pharma safety needs, non-waterbased inkjet systems may see more development in future. As of now due to the speed and versatility offered by UV Inkjet coupled with the ability to add additional white and other colours, UV inkjet is the predominantly used technology however investment is high. Therefore, selection of the best suited technology for digital in labels must be as per individual printer’s need and that of their diverse customer mix. It is a competitive time and cost of equipment, cost of consumables and the nature of output is very important to ponder over before finally selecting the first entry into digital.

Written by Harveer Sahni Chairman Weldon Celloplast Limited New Delhi November 2019