One common question I always face when talking to officials handling national ID is, “Could you guarantee the colors printed on the ID cards would last for 10 years at least?” Then, more controversies arise when comparing the printing methods and the ink to be used. This article is to challenge how much you really know about the truth of ID Card Printing. Is retransfer printing better than direct-to-card printing? Is pigment ink better than dye-sublimation ink? Is color laser engraving better than printing? Well, the answer is, it all depends! Besides, costs count.
There are three common false assumptions people make before really looking into the matter.
- Believing that the longevity of an ID card is purely dependent upon the ink or laser.
- Believing that color fading is only caused by UV light, so all cards are more or less the same.
- Believing technologies and vendors have more say on ID project, thus people cannot exert much control in the process.
On top of these, we, sometimes, may forget to weigh benefits against cost, too. That is, the efficiency issue.
Dye-Sublimation Ink, Pigment Ink and Color Laser
In terms of card materials, there is already a consensus in the industry that PC (polycarbonate) card has a better longevity than PVC (polyvinyl chloride) card. A PC card can last for 10 years while a PVC card will remain intact for around 3 to 5 years. To print color IDs, the traditional way is to choose between dye-sublimation and pigment inks, plus the appropriate printing method such as direct-to-card or retransfer technologies. In recent years, there is a newer choice to print color IDs, i.e. via laser engraving. By laser engraving, it means different layers of color ink are first embedded and sandwiched into a PC card during card production process. Then, an appropriate laser is used to engrave and activate those color inks to produce a desired image. In this article, let’s focus more on the first two ink technologies which are quite mature in the market, yet have more arguments over.
First thing first, the technologies used in the card printing industry actually come from photo and paper printing industry. Particularly, those ink technologies being used in card printing are not much different.
The printing world starts with three different kind of inks with different physical characteristics:
- Dyes, which are water soluble. Due to its small molecule size which ranges from 1.5 to 4 nanometers (1 nanometer=1/1000 of a micrometer), it is easy for dyes to obtain saturated and brilliant colors. The small particle size enables refracting or scattering very little light, thus providing a large color gamut and allowing dyes to “seep” into most media, too.
- Sublimation Inks are a kind of heat-sensitive dye. The sublimation process turns these inks into gas under the influence of heat and combines 100% with the media (usually polyester, acetate rayon, poly-Lycra and acrylics). Since the ink becomes part of the structure of the printed material, the images on the printed media do not fade or crack even after multiple washings.
- Pigment inks consist of tiny particles of colored material. A pigment is made up of numerous molecules bonded together by extremely stable chemical bonds, creating a significantly larger particle measuring 0.05 – 0.20 micrometers, that is, 50 nanometers to 200 nanometers. Pigment inks are not water soluble. Therefore, they are carefully displaced throughout the carrier most commonly by micro encapsulation into polymer or resin.
The table below summarizes some major physical characteristics of the three inks.
|Dye Ink||Pigment Ink||Sublimation Ink|
|Use||Most commonly used in office and paper work||Designed specifically for fade resistance and long print life||Specially used for sublimation and used in non-office applications, e.g. textile, hardware, ceramics, etc|
|Advantage||• Wide color gamut for best color image printing;
• Bright & refined images
|• More UV resistant;
• Washing standing, waterproof
|• Waterproof, washing standing
• Allows for very high quality printing using a heat press, substrates that are polymer based or coated or polyester material.
• Given the correct amount of heat, pressure and time, colors don’t easily fade or be washed away.
|• Water soluble and give a poor performance in lightfastness;
• A ph neutral media is recommended for use with dye-based inks because of their tendency to oxidize in an unbalanced ph environment
|• Its larger particle size resulting in a smaller gamut making some colors look muted or dull;
• Printed image is not so clear as dye ink and sub ink;
• More susceptible to metamerism, which means the shifting of color under different lighting; doesn’t look the same shade from all angles;
• More costly to produce because pigmented inks cannot simply “seep” into media but require something to “attach”.
Since dye inks are water soluble, they permeate into media in a very short time while pigment inks will stay on top of the printed media.
When applying in the card printing industry, these inks are modified into two groups, the dye-sublimation inks (applying the heat transfer characteristics of sublimation) and the pigment inks. In view of their physical characteristics, dye-sublimation inks are able to produce an image fused into the printed materials. As for pigment inks, a protective layer covering pigment color particles may be desirable as it is helpful against attrition off the printed surface.
Generally speaking, cost of producing pigment inks is higher than those dye-sublimation inks; but pigments inks have better lightfastness if no protective layer is added on top of an ID card.
Lightfastness and Color Fading
Lightfastness is a critical element that any ID card issuer has to consider. It is because color fading occurs when an ID card is exposed to sunlight. Universal research findings show that pigment inks have an outstanding performance on lightfastness. According to Wilhelm Imaging Research, Inc. (WIR), a leading image permanence test lab on digital printing materials, paper prints by pigment printers using appropriate media (paper) could survive up to 200 years in dark storage. In contrast, dye-sublimation prints offer a slightly lower lifespan; in dark storage, they offer a little more than 100 years of longevity.
If exposed to sunlight, both dye-sublimation and pigment prints survive for shorter periods than their rated lifespan. WIR testing methodology requires color prints to be exposed under a light source of 450 lux for a continuous 12 hours. It is found that prints made with pigment inks retain their fade resistance advantage, with typical lightfastness times in excess of 100 years for prints framed behind glass. As for prints made with dye inks, they can resist fading for 20 to 60 years when framed behind glass.
Unfortunately, there has no research ever been done on prints with PVC or any cards by WIR until now. Whether both dye-sublimation and pigment inks would be able to pass the 10 years lightfastness threshold required by most of ID government officials, there is not a definite answer. Yet, a wild guess based on the paper photo print findings, it may be an affirmative yes. Besides, adding a protective transparent overlay or holographic laminate on top of the print images will demonstrate good lightfastness according to the tests done by WIR on prints framed behind glass.
Table 2: Guide for recommended light level in different workspaces:
Plasticizers and Color Fading
Sometimes, we would find that colors of an ID card just fade only months after card issuance even if they are not exposed to sunlight or UV for years. Such incident is caused by another important contributor, i.e. plasticizers.
According to Wikipedia, plasticizers or dispersants are additives that increase the plasticity or decrease the viscosity of a material. These are the substances which are added in order to alter their physical properties… the dominant applications are for plastics, especially polyvinyl chloride (PVC). In the card industry, plasticizers are added during PVC or PVH card production process in order to keep the cards softer and make it more flexible. Yet, they will be not added in the production of Polycarbonate (PC) & PET cards.
In recent years, it is found that adding excessive plasticizers would have a critical side effect to prints on PVC / PVH cards, that is color fading. As an PVC card ages and warms up to higher ambient temperatures, plasticizers will start to evaporate or move to the outer printable surface of the card. They vaporize and become acidic, attacking any dyes inks printed on the card, yet not so much the K resin. It is also found that quite many “made-in-China” cards are using excessive plasticizers in card construction.
Just like the sample card shown here – it was printed on a card supplied by a China source and dyes are obviously been “eaten”. No such phenomenon has been recorded if it was printed on cards from other sources as told by the affected party.
To Regulate – INCITS 322-2015
By all means, color fading can be avoided but not just from technology improvement by vendors. Instead, institutional buyers such as government departments, who are the biggest issuers of ID cards, should adopt stringent standard for the ID card industry to follow.
One of the examples is the standard introduced by The InterNational Committee for Information Technology Standards (INCITS), who is the primary U.S. focus of standardization in the field of ICT. Vendors who want to tender in certain government ID card project are required to prove themselves physical characteristics of their cards they claim by adopting standard of INCITS 322-2015. Different standard testing procedures are introduced to find all qualities of card durability. Vendors must submit lab test reports to show all findings instead of a general claim of card or print durability.
Among these procedures, section 5.13 of INCITS 322-2015 is about testing on plasticizers. Nowadays, 70% of plasticizers being used are primarily diisononyl phthalate (DINP), diisodecyl phthalate (DIDP) and di-ethylhexyl phthalate (DEHP, sometimes also referred to as DOP).
The purpose of this test is to determine a card’s resistance to plasticizer attack. Cards with inadequate resistance can have printed dye degradation, especially if stored in plasticized vinyl sleeves. DOP has historically been used as a common plasticizer for vinyl sleeves and has been observed to cause degradation of print on cards. Although other plasticizers are now in use (such as DINP), DOP is judged to be a representative plasticizer. Use of DOP also allows comparison with earlier testing.
Well Balanced Thought
Therefore, in order to get a durable card with long lasting color, a well balanced thought of using the right kind of card materials and right inks are very important, not to mention the consideration of the right printing technology and protection preference such as putting a laminate on top. Finally, the cost per print is what the government or institution would consider most.
To summarize, do consider the following factors on assessing the ID card printing options
|Card||PC / PET Card||No plasticizer but may need UV protection|
|PVC, PVH Cards||Plasticizer & Lightfastness|
|Ink||Dye-Sublimation||Wider color gamut with sharper image
Weak against plasticizers on PVC cards
Better image fusion with card materials
|Pigment||Good acceptable color
Best against plasticizer (if any or printing is on PVC cards)
Weak scratch resistance
|Color Laser||Best against lightfastness and plasticizer
Improving image quality as technology develops over time
|Printing Method||Direct-to-Card||Desktop or central issuance|
|Retransfer Printing||Desktop or central issuance|
|Color Laser Engraving||Central issuance|
|Added Protection||Clear Overlay||Protection against UV and abrasion|
|Holographic Overlaminate||Protection against UV, abrasion and production of fake ID|
|Precautionary||Implementing Proactive Standard||Introducing INCITS 322-2015 or lab test report from third party to prove card durability|
About the author
Kenneth Cheung was one of the founders of IDM magazine back in 2013 and the Executive Editor there. Currently Kenneth is the Consulting Editor of the new IDM Media Platform and is also the Director of Sincerely Yours Techno Point Ltd., which is dedicated to turn smart technologies developed in the industrial field to more life-style applications in the commercial and consumer sectors.
Previously, Kenneth worked in Matica Technologies and HID Global, where he was the Asian team leader responsible for identity and card personalization equipment sales in APAC. He has tremendous experience in electronic security and smart card industries. Kenneth has been highly involved in devising product solutions of integrated security, intelligent transport management, national ID, secure printing, retail and banking applications of smart card for over 20 years.
On top of his career in the technology supply chain, Kenneth was the Event Director of the Asia Pacific Smart Card Association. Prior to that, Kenneth was one of the byline editors of Automation & Security (A&S) magazine for seven years, contributing to its China, Asia and international editions. During his engagement with A&S, Kenneth also found and developed one of the largest security trade shows in APAC, SecuTech Taipei.