Recently I was invited by “Modern Packaging & Design Magazine” which is published by Infomedia 18 Limited to write an article on the role of advance screen printing in packaging as a guest columnist.
Many of you might have read my article if you are receiving their magazine, but if you have not read till now then here’s it…
TECHNICAL ARTICLE, By Bhargav Mistry, MD, Grafica Flextronica & DMI
Published in Magazine “Modern Packaging & Design” Vol. 6, No. 1 | Jul-Aug 2010
(Copyrights remains with the publisher)
Screen printing process evolved over the years. Today, it offers ample innovation & creativity, thus playing a major role in packaging because of the availability of advanced screen printing machines, UV technology coupled with availability of innovative special effects inks.
Screen printing is a simple yet attractive process. The main reason is that in screen printing, the purpose and the art is to transfer something, almost anything more or less liquid through a screen!
It harnesses the natural phenomena of mechanical movement, flow and the interaction of liquids and solids. In screen printing, it is possible to attain controlled film thickness up to 300 micron. Besides, the printing medium – ink – can be almost any material that can be suspended in a fluid and which has a particle size that is ideally one third of a mesh opening.
Also, the visual impact that screen printing process can create is simply marvelous. The durability of the inks, the vibrancy of the colours, especially considering the harsh outdoor weather conditions for outdoor applications (sunlight, rain, snow, wind, etc) and its vast flexibility, all contribute to its unique capability. Screen printing is possible with any ‘semi-liquid’ product (various inks and dyes) on a number of rigid, semi rigid or soft substrates. Thus, these characteristics make it the most versatile printing process available.
Advantages of screen printing process
* High rub and scratch resistance, which is mainly required in industrial printing
* Vibrant colour
* Due to availability of high quality screen printing inks with better light fast pigments, 3-5 years of outdoor life for any kind of applications can be achieved
* Wide range of substrates of various thickness, size and shapes can be printed easily
* Good ink film and mechanical stability allows to screen print on complicated and rigid substrates.
* Knowledge and process calibration provides high dimensional stability
* Screen printing enables to achieve a degree of flexibility that is unavailable in other printing process
* Flexibility of short runs to large industrial volumes
* Inks are available as per application
* Possible to print on fragile matters
Advanced printing technology
Quality in screen printing seems to have come a long way. Today, with automatic precision machines, it is possible to get a result that years ago would have been a dream. In the last decade, from a predominantly manual printing process there has been a big shift from manual operations to semi-automatic and NOW fully automatic printing machines. There are more numbers of screen printing machines sold today than it was five to ten years ago because it not only involves low investment which is a big advantage for those wanting to join the screen printing business, there is also scope for creativity. The screen printing technology today is faster, better and cleaner.
Despite any type of screen printing press can be used (including manual and semi-automatic), the best press for that kind of work remains for me the cylinder press with automatic feeding, for reason quite often combination with offset, of speed, productivity and quality of result. And, for the same above reasons, the UV technology is also the best available one in the present and the future, both for technical and environmental reasons.
UV Curing depends upon the type of UV ink of varnish and of the thickness of the deposit: it is useful to know that in UV systems, a varnish even thick of several mm, will cure easily and instantly. For example, for metallic inks or some other printed chemicals, it have to be tested and set at very different speed and UV light intensity.
Screen-printing is a fantastic technology that is used by many industries with so many old, new and not yet discovered applications – both flat (plastics, cloth, metal, thin to thick papers, sunpack/sunboard, rubber, leather, wood, glass, ceramics, etc) and non-flat substrates, by using appropriate machinery and inks. Further, this process is also widely used for printing packaging boxes, duplex and sapphire mono cartons, labels and cards, UV effect on packaging materials for cosmetics, toothpaste, jewellery … the list is endless.
In this world of shopping and mall culture, buyers are attracted by the packaging they can see and/or touch. Before that tryst with packaging, they also carry the memories of advertising (both print and electronic), outdoor posters, etc. As they walk into the shop, first they are also confronted with eye catching POPs and POS posters, placards and other marketing gimmicks. Ultimately, the packaging in a shelf carries its look, its power of attraction for the consumers, and eventually the feeling of touch, or we can rightly say, today packaging is all about sensation – look, touch, feel, smell.
So, special effect screen printing is a great way to excite consumers. The range and variety of effect is extensive and it provides the marketer, print buyer and designer with a number of exciting possibilities they may never have thought were viable. This is because of the latest developments – machines and inks.
The most promising is the use of a wide range of ‘special effects’ thanks to the think tanks in the screen printing industry driven by FESPA, an international association of various national printing associations including India. FESPA spent a lot of resources to make a special book named “SENSATIONS” that shows many of those screen printed special effects.
The packaging can be printed through many techniques: offset, flexography, screen and digital printing or other. However, only screen printing allows to add those “special effects” enhancing the final product due to its versatility. These possibilities, combined with off set, digital, flexo or classical screen graphic, open a huge niche to many screen printers who will be able to offer customers truly enhanced and unique products and images to increase sales.
This is obtained by the addition of some surface effects that will catch one or several senses of consumers: The view or look of packaging which makes a initial difference – it is like first impression is the last impression … but now consumers want to touch by the feel of it and sometimes, why not rub and smell it. Amazing though, several of these effects can be used on the same item (multiple special effects, like we try at DMI institute). It can also replace, often at a lower cost, some other technologies such as hot stamping, doming, silvering under vacuum.
Specialty Inks & Varnish
The print buyers these days want something different from their competitors and are prepared to pay a fair price for that. They will accept a much higher price if the printers bring a very special enhancement of their product packaging image. So, one of the most interesting niches in the graphic screen printing fields is the printing of special effects, using UV special effect inks.
The inks available in the market range from luminescent to tactile, from glitter to mirror. The impact they can add to designs is breathtaking. Screen printing effect can enhance any marketing campaign and may give it that extra competitive advantage. One may also enhance the effect with ink or an overprinted varnish. Varnishes have become a popular finish on wise labels especially because it gives the graphics a much greater richness of colour.
A gloss varnish over a matte surface is a more subtle approach that inspires curiosity. One sees a shape under the light or notices a smoother feel against a more resistant matte solid area. Similarly, coarse, high luster effects are created with thick coatings of varnishes that have large particle sizes. It is a striking way of printing reversed out images of icons or logos, an ice effect or extremely fine line patterns. A wrinkle effect can be created when a UV varnish is cured under UV-A light.
There are thermo-chromic inks. These are sensitive to temperature change and can be used for time temperature indicator labels. Irreversible ink types, which do not change back to the original colour, indicate if perishable goods have been stored for too long or at to warm a temperature.
Packaging for the blind
For blind people, the “Braille” texts on labels or packaging are printed. Here, a thick varnish screen printed is widely cheaper than micro-embossing through die-cutting or embossing technologies. Embossing is a slow and expensive technique (for the tool itself). It can be easily replaced by screen printing of thick UV varnishes.
The security feature of screen printing is immense. This feature can be used to protect the brand against counterfeiting or tampering. RFID labels are used to provide security and efficient tracking and tracing of products, cases through the supply chain.
I have a customer of mine in Mumbai who is into packaging (with offset and screen printing unit) whose clients are happy that he offers something different every time because of UV special effects which they feel a luxury value addition especially in case of cosmetic, and such luxury product packaging. He strongly feels that UV special effects are not only luxury value addition for customers but a ‘safety net’ as well. Because of the very nature of special effects, it will help the companies in protecting their brands from duplication.
One fantastic application of screen printing is the printing of both antennas and transmitter/receiver in RFIDS : Radio Frequency Identification. This is beginning to replace at short and medium term the classical barcodes that need to be caught at very short distance. The printing of those items, both on or inside of the packaging itself or on a special label to stick on or in, is ideally suited for screen printing in that sense that it is the best technology to print the conductive silver, carbon or nano-particle inks for the antennas or receptors.
Continuous advancements and developments in polymer technology, expertise and cost-effective manufacturing, plastics is replacing traditional materials in many fields (environmental conditions apply!). These include : PVC, Polypropylene, HIPS, Lenticular Films, Polycarbonate etc. Polypropylene Sheets are extensively used for blister packaging, cardboard boxes etc. Polypropylene finds application in Disposable Containers, Embossing, Gift Box Making out of clear sheets, Freight Packaging, etc. The trend these days is to use a substrate with a low density which also makes it affordable. PVC Sheets and Polypropylene Sheets are the best suited for screen printing. Polypropylene as a material is very eco-friendly and can be easily recycled. It is accepted and widely used all over the world for different applications. It is preferred by screen printers because of its low density and very economical cost. Similarly, PVC for screen printing purpose is a very good option. A good quality PVC sheet makes a good surface for a screen print because it has a pre-coating on it; even if the material gets old the coating is never hampered.
Perfect expertise needed
The main problem is of course the adjustments of registers, knowing, for example, in offset if each sheet printed simultaneously in four or six colours is perfectly registered, it can be some differences from one pallet to another. In case of UV spot effects, the register problem is crucial and requires a perfect control of the different elements of the image.
Some special effects will have to be entirely designed or separated from parts of the original image: this means that either a studio or an individual that created the image and/or yourself are able to prepare the needed proper part of the file: this is of course very important. In PDF, the problem of layers and transparencies can be difficult to solve: it also depends upon the quality of the files received from the customer or its studio.
As those effect will quite often have to be overprinted on inks and/or substrates printed with other technologies (offset, digital printing, flexo, hot-stamping, foils, etc.) a huge care must be taken. For example, even, for a simple high gloss spot varnish above a classical offset print on paper or board, be sure that the offset inks are over-printable: this means that they must not contains any wax, or worth, silicones, or of course that the so classical automatic powdering has been eliminated by the offset printer through a careful automatic brushing.
Screen printing is now quicker, cheaper, produces better quality images and offers a number of special applications. But advanced screen printing with high level of automation is not everybody’s cup of tea. Having advanced machines in place is not sufficient to run a profitable screen printing business. There is no profit “from the press of a button” like in digital printing arena. There is no short cut. Because not only does the set-up process take considerably longer than other techniques, but being able to truly master printing high quality images using the screen printing process also takes much longer, because there are a number of variables involved.
Today, there exist different systems designed to help the screen printers to achieve better result. But it revolves around the simple concept or standardisation of the entire screen printing process.
I hope you must have enjoyed reading…