Paper substrates in Self Adhesive Labels!

Self adhesive labels originated in India around 1965 when a screen printer in Mumbai used a PVC film as face paper and a polyethylene film as the release liner. The hard to wet polyethylene or PE film performed as a release liner because the pressure sensitive adhesives available at that time were not designed to anchor on to PE. The label or sticker so produced would open with a crackling sound as it would be a little difficult to peel it from the PE backing liner. For the same reason paper could not be used on face as it did not have the adequate strength and would tear off while separating from the PE liner. The force required to peel was too high and thus the usage of PVC film was justified. That was the beginning! Soon special base papers and silicon release coatings were available in India. Siliconised glassine or “Silicon Paper” as it came to be known became the preferred backing liner for all self adhesive label materials. This also made it possible for paper to be used as face material. Silicone coating on these base papers provided for an “Easy Release” making it possible to peel off these self adhesive labels effortlessly from their backing release papers. Adhesive chemistries developed such that adhesives could permanently bond even to PE and silicon chemistries also experienced continuous development, such that they can now be applied to PE film for achieving excellent release properties. Since the silicone and adhesive chemistries are beyond the purview of this article, we shall dwell primarily on the various papers used in this industry.

Labelstock essentially consists of three main components, Release paper, Pressure sensitive adhesive (PSA) and Face paper. We will dwell on the various types of papers used to form the release paper and the face paper. It will be appropriate to mention here that the self adhesive labelstock technology has technologically advanced to a level whereby a substantial portion of the output has seen a definite shift to filmic substrates both as face papers and as release liner. Paper however remains the major and important part of the labelstock production. We discuss the two components separately.

Release papers: These are papers that are highly calendered, non-absorbent and with a smooth surface so that silicone can be coated on it for imparting release properties. The papers need to be densified and have uniform caliper for good die-cutting. The various types of papers used in production of release papers are as follows;

1.       Glassine

2.       SCK or Super Calendered Paper

3.       CCK or Clay coated paper using bleached Kraft as base paper.

4.       Polycoated papers.

5.       Saturated papers

Filmic liners have also steadily found acceptability due to their uniform caliper, smoothness and specific character, still paper based liners constitute almost 90%of all the release liner used. While SCK was the preferred substrates in North America due to lower price yet the European market was always largely using Glassine due to performance and aesthetic reasons in auto dispensed labels. India for long years followed the European model. Labelstock producers and label printers opted for labels with glassine as release paper. To have a good die-cut label, that would dispense with ease and speed on an automatic labeler, it is necessary to have a good release liner. Any variations in caliper of the liner may result in nicks in the release paper that would result in web breaks at the end user level. While die-cutting is done by the label printer, the end user of labels is the one who is dispensing them. The two processes are complimentary to each other. The functionality of the self adhesive label is highly dependent on the liner. Any web breaks would lead to increase in downtime and create problems for the users.  Auto dispensed labels and barcode labels drove the demand for glassine liners. This is due to the transparency of the paper through which the label is sensed by the sensor and dispensed or printed by a barcode printer. Things started to change but very slowly such that in the last decade, SCK which has very similar construction and properties to glassine started to be used sparingly. Since the bulk of the demand was for glassine, Indian stock manufacturers stayed away from promoting other varieties of paper. However in small manner some stock manufacturers were experimenting with SCK, CCK and Polycoated papers. The effort was extremely limited until stock lots of laminates and base papers from North America started to land in India in large quantities. Some printers under extreme pressure for cost reduction from customers started to use these stock lots. It was only a matter of time that the larger printers also started to consider these materials for customers who were not very fussy or rigid about the liners. This exercise created a definite segment of labelstocks with different release liners. While the auto-dispensed labels and barcode label segment partially started to accept SCK which had similarities to glassine, it was the sheeted product market that went in for a paradigm shift to CCK as liner. This is so because the laminate produced with CCK as backing and sheeted for Offset printing would have excellent lay flat nature. This would enable it to be printed on offset presses with speed, as curl in sheets was a printer’s nightmare. The siliconising operation involves taking the paper through high heat for thermal curing. This process depletes the moisture content of the paper and makes it unstable. Due to the highly calendered construction of glassine the paper cannot regain moisture quickly and evenly despite being subjected to re-humidification process. The uneven absorption of moisture when the labelstock is sheeted and exposed to atmosphere tends to make the release liner to expand and make the sheets to curl. CCK or clay coated paper has one side coated for imparting a good silicon hold out and the other side is left as it is, so that it can breath and regain moisture during the gumming process when emulsion adhesive are used and the heating chamber has high moisture content that helps the paper to rehumidify to a level of stability. Other segments of label printers who were now richer in their experience from using imported stockpots of labelstocks started accepting the stocks from local manufacturers with these non glassine liners for cost reasons.

Polycoated papers also have found usage in a limited quantity for the past two decades. These consist of normal maplitho variety of paper over which a layer of polyethylene or polypropylene has been extruded. Due to frequent defects in polycoating and lack of consistency in the earlier years, the growth of these papers was restricted. However in recent times imports from China and other East Asian countries with polycoated release papers made many people in the industry to rethink and improve upon the technology. So much so, that these papers have also found continued and specific usage in the computer label segment. Another paper that has started to find foothold in some segments is the saturated paper. This is very similar to polycoated paper, the only difference being that the plastic (PE or PP) is replaced by a proprietary chemical coating which provides a good silicon hold out.

Going by personal knowledge of the market over the years and assessment, I have tried to estimate the tonnage of paper used for release liners in all the labelstock consumed in India. The basis of my estimate are made on figures of total consumption of labelstock that I mention in the last Para of this article. I estimate that 45000 to 50000 tons of base papers form a part of all the labelstock sold in India solely for the purpose of self adhesive labels. The demand for other applications like tapes, Hygiene, medical, food, etc. is all separate and extra. The way this industry has evolved and due to cost pressures most of the base papers for labels are silicon coated captively by the labelstock manufacturers.

Face Papers: Face paper in labelstock is what actually and finally becomes the label. It carries the branding, product information and decoration along with the adhesive. The release paper only protects the adhesive so long as the label is not used. As soon as the label finds its application, the release paper comes to the end of its limited lifespan and ends up in a waste bin or a landfill or incinerated to dispose off. Efforts are being made to recycle them. Demand for face papers are according to the application they are needed for.  The list is exhaustive and keeps on extending as per the imagination of the designers. I list below some of the commonly used papers;

1.       C1S or Semi-gloss paper and commonly known as Chromo Art Paper.

2.       Uncoated Matt or Maplitho Paper

3.       Cast coated or Mirror Coated Paper

4.       Thermal Transfer Paper

5.       Direct Thermal Paper

6.       Fluorescent Paper

7.       Colored Papers

8.       Metalized Paper

9.       Foil Laminated paper

10.   Textured paper

11.   Security Papers

12.   Papers for Digital Printing

The semi Gloss or chromo art paper and Maplitho paper together account for the biggest chunk of labelstocks sold in India. According to my assessment between the two, they account for nearly 70% of the total stock used, over 15% is filmic and 15% is others. Filmic should have been more but the shrink sleeve has taken away substantial market share. This would amount to about 55000 tons of paper used annually, both chromo and maplitho put together for self adhesive labels. The chromo art paper labels are mostly used for pharma labels, cosmetic/product labels, lube oil labels, and also barcode label. Maplitho finds extensive application in  price marking labels for handheld labelers, computer labels, logistic and other EDP labels.  Cast coated paper, popularly known as mirror coated paper is used for high-end retail labels with lot of decoration on them. These have lost much of market since printers have started to use semi gloss paper with UV Varnish to get high Gloss. Moreover labels for smaller diameter pharma bottles faced problem with cast coated paper as due to their stiff nature they would get an edge lift leading to rejection of labels. Thermal transfer paper is a special matt finish smooth paper used for producing barcode labels in barcode printers with thermal transfer ribbons. The heated print head presses the ribbon against the paper to neatly transfer the image on to the paper resulting in a barcode. Barcodes help in retail selling, inventory control, logistics, accounting and a host of other applications. The volumes of this paper which is mostly imported, grew at a fast pace due to widespread usage of barcodes. However due to rising cost and availability problems much of this business has shifted to chromo art paper which has found a high level of acceptability from label printers and users. Everyone recognizes direct thermal paper popularly known as fax paper. It changes color when a heated print head touches it. With the advent of internet connectivity, emails becoming the mode of communication and faxes being phased out, this paper was heading towards a slow death. It suddenly got a new lease of life with new applications arising in labels with a shorter lifespan. It can print barcode without the need of a thermal transfer ribbon. Barcode labels for grocery in malls, petrol pump sale bills, toll tickets, retail vends, courier co’s, etc. started to be made on direct thermal paper. The product consumption is now growing at a fast pace prompting many companies to initiate manufacturing this product locally. Colored papers, fluorescent papers, metalized paper and foil laminated paper are used for their eye catching appearance and for attracting the consumer attention. With growth of packaged foods, gourmet foods and wines, the need for textured and designer paper for label applications has become imperative. At this time these papers are not produced in India. They are supplied by specialized paper producing companies like Fedrigoni of Spain. These papers are not produced in India and smaller volumes along with the diverse nature of designs, makes importing these, a costly proposition. Some innovative printers have started to indulge in getting the embossed effect on papers by using special flexible dies supplied by companies like Lartec also of Spain. These dies actually do not emboss but deboss and yet produce a textured effect on the paper. I am sure this will create market for textured papers in India. With increased incidents of pilferage, counterfeiting and duplication, there is a growing need for tamper evident and security labels. Some mills even in India have started to offer papers with UV fibres that glow in dark when exposed to UV light for verification. Others offer papers with water mark. There is also need for paper that would be weak and fragment into pieces on tried to be removed but this property is against the target specification of the mills who try to achieve high strength in the papers they produce.

As the digital printing industry continues to evolve and pose threat to the conventional printing, the paper mills in India cannot ignore this segment which is growing at a very fast pace. As quality and speeds pickup in digital printing, I am sure that it will be difficult to match the versatility of this technology even for label printing. Tambola tickets, lottery tickets, short run product labels, security and sequentially numbered labels are some of the applications that have already shifted over to digital printing. At this point of time special papers with top coating are required and some label printers do a primer coating on labelstocks themselves to achieve perfecting standards in digital printing. Label stock manufacturers also offer stocks top coated by them. It may just be a matter of time that paper mills offer pre-coated papers. The possibility of the technology upgrading further cannot be ruled out when all digital printers will print normal papers that are available without any additional primer coat.

India with its 1.12 billion strong populations is fast becoming a global economic powerhouse. It is estimated that this year the country will have the highest number of English speaking people in the world. Almost 30 percent of the country’s population is between the ages of 10-24 years, while the average age is 26 years. 70% of these young people are literate. A Young and literate workforce are growing up to work more, earn more and spend more. With higher disposable income they are becoming a part of a bulging middle class, larger then the entire population of United States. For this reason the world’s largest retailers are making a beeline to India to be a part of this growth.  If the number of mobile connections is an indicator, it is interesting to note that in July 2010 alone 17 million subscribers were added taking the total number of mobile users in the country to over 652 million. The demand for consumer products, packaged foods, pharmaceuticals and all packaged products is slated to see a quantum jump. With this will also increase the demand of labels. The self adhesive label industry is presently estimated to be growing by excess of 15% per annum. According to published data, 16 billion square meters of self adhesive labelstock is converted into labels in the world every year. By my own estimate total annual consumption of self adhesive labelstock in India is about 750 million square meters. This translates into a per capita consumption of almost 0.75 square meters. Compare this almost 3 square meters in China, between 13-15 square meters in Europe and a little more in the US.  Based on the above estimation of total consumption of labelstock, I calculated the quantity of paper used for release paper and that of face paper for label stock consumed in India. I conclude that over 1,00,000 tons of paper is used for the entire quantity of self adhesive labels used in India!

Written by Harveer Sahni, Managing Director, Weldon Celloplast Limited, New Delhi-110008 1^st November, 2010. The article was published in October-November 2010 issue of the magazine "Paper Mart"