About Chemical Innovation - Subscription Information
February 2001
Vol. 31, No. 2, pp. 42–51.
Learning from the Past

Table of Contents

David Haas
Times-up! The color-changing self-expiring badge

Opening artHow do you prevent visitors’ badges and day passes from becoming universal access cards? How can you track medication schedules and expiration dates? One company has an answer.

Has this ever happened to you? You walk into your office one morning to find a sales rep, holding a sample case and wearing a valid security badge, already waiting for you. Wasn’t he here just the other day? Why didn’t the receptionist tell you he was back?

You’re on a medication regimen that requires you to take the blue pill once every 4 hours on an empty stomach and the red pill once every 6 hours on a full stomach. Or was that the blue pill every 4 hours on a full stomach?

Your conference attendees visit the exhibition hall just long enough to grab some free munchies and beer, but they don’t spend any time looking at the exhibits. If you could get them to stay around until after the door prize drawing, they would be more likely to look at the vendors’ displays (and your vendors would be more likely to sponsor you next year).

Identifying an opportunity

This story began back in 1976, when I worked for Philips Electronic Instruments (a division of North American Philips). During the 1970s, Philips had become the major supplier of airport security X-ray screening units throughout the world. As the principal X-ray scientist for security systems, I had designed these original Philips airport X-ray scanners.

In retrospect, I suppose that I had the right combination of opportunity, aptitude, and personality traits to come up with the concept of a self-expiring badge. Technical innovation was my job, so conceiving novel products was all in a day’s work. More importantly—as was typical of many technical people—I had great disdain for company security procedures, particularly having to wear ID badges. It was considered a substantial nuisance. Many of us failed to return visitors’ badges when visiting other facilities; it was a challenge to get away with this and also a minor means of getting back at “the system”.

X-ray screening equipment was coming into its own in the early 1970s, when Philips was awarded a contract from the U.S. Secret Service to supply this equipment to the Republican and Democratic National Conventions. As part of the contract, a technical expert would accompany the equipment to train the contract guards who were to operate the equipment.

On the first day of the Republican convention in Kansas City, MO, contractors were required to obtain security ID badges from the Secret Service. These badges were issued for all contractors, whether they were to be on site for one day or throughout the event. I knew that once the badges were issued, it would be impossible to control their use after recipients completed their assigned tasks. It was well known that any ID badge that looked professional and resembled the real thing could “pass” and allow access into the facility. Because the ID badges were strictly visual, once badges were issued, they could be used for the entire event. More importantly, if a badge were lost or transferred to another person, it could still be used for the entire event.

I was surprised at the limited technology available to this most sophisticated of government agencies for one of the most visible national events, where absolute ID control should have been essential. I would have expected the Secret Service to produce a super-sophisticated ID badge. In fact, it was a Polaroid photo with the individual photographed in front of a Secret Service backdrop; the name and date were in small type. Although such a badge met the highest standards of the day, there was no way to limit use of this ID once it was issued.

At that moment, I recognized a real need for a badge that could not be used once the contractor left the site at the end of the assignment. What an idea—a self-destructing ID badge!

Existing technologies

Beginning in 1978, I made numerous efforts to figure out how to make a self-destructing time badge. A self-timing badge could not be put on the shelf as a finished product, because it would immediately time out and be of no value to the end user; the issuer of the badge had to perform some physical act to initiate the timing process. I wrote many long lists trying to identify the most practical initiation process: for example, mechanical pressure, heat, light, exposure to water (humidity), oxygen, or chemical spray. The possible initiation processes were almost limitless, but only a few were practical enough to be used at a company’s reception desk or at the check-in area of a coliseum or construction area. Many of the processes would have required hermetically sealing each badge in its own pouch, which would have made the product impractical. Chemical odors and large, noisy, or complicated equipment were also unacceptable. The problem was more difficult than I had first imagined.

In 1980, after 2 years of trying to produce a self-expiring time badge, I was convinced it was impossible. The only product I had found that could conceivably be the basis for self- expiration was a form of photographic paper called “printout paper”. Printout paper self-develops when exposed to light, changing color with no wet chemical processing. By producing a light-sensitive badge, we could offer a white ID badge that turned dark indoors very slowly but turned dark instantly when exposed to outdoor light, for example, once a visitor left the building. Light-sensitive badges were much like paper labels: one-part, self-adhesive, and easy to write on. They were largely tamper-resistant once issued, and it seemed only a minor problem that they did not work at night.

Photos courtesy of TEMTEC Inc.
Figure 1. Light-sensitive badge before (white) and after (blue) expiration by exposure to outdoor light.

In 1981, my wife Sandra and I started TEMTEC Inc. I continued working at Philips, and Sandra ran the fledgling business from the basement of our home. We began producing and shipping our first light-sensitive self-destructing badges to the security market that year (Figure 1). These badges were white when issued but turned dark after they were exposed to outdoor light (1). The concept of ID badges that controlled themselves automatically was an idea whose time had come, and product sales increased exponentially each year. Clearly we had done something significant to solve the problem of minimizing and controlling the security risk of lost temporary IDs.

The human factors

Any time you develop a new product, it’s critical to identify the features and benefits that are important to the user. And users never cease to surprise. We had assumed that the highest priority for security professionals would be security, that they would not object to purchasing hardware, and that some additional labor would not be a problem for a front desk staff. These assumptions were all incorrect. In fact, when it came to visitors’ badges, security ranked fifth on the list: Cost, ease of issuing, appearance, and the specific color change were all deemed more important than security.

We learned that the loss of visitors’ badges was primarily a human factor problem. People just forgot to return their badges, and even when visitors inadvertently walked out wearing temporary badges, they were not sufficiently motivated to return them. It was not unusual for companies to lose up to 30–50% of their visitors’ badges each year, creating a gaping hole in their access control security. In general, the only people who deliberately took visitors’ badges were salespeople, who could use them to make return calls without clearance from the front desk. Salespeople provided us with the best example of the usefulness of self-expiring badges.

By 1986 I had long since left Philips, and TEMTEC was a small but thriving business. Our sales of light-sensitive badges and other identification products had grown substantially, but our customers were still asking for a time-expiring badge. There were two major problems with light-sensitive badges: A visitor who left a facility during the day would need a new badge upon returning. Conversely, light-sensitive badges could be shielded from light and not self-expire. Security managers wanted a “guaranteed-to-expire” visitors’ badge—not just for enhanced security but to help convince management that the product was worth spending money on.

Wanted: Brighter colors

Thus, in 1986, I resumed the work on developing the time badge. As fate would have it, Herculite Protective Fabrics, a specialty fabric company, had patented a “paper” time indicator in 1980 (2), which I realized might be just the technology for making a time badge. That company saw no value in the patent, but TEMTEC did, and ultimately, this patent would be the missing link we needed. The patent described a two-part system in which a vinyl film with pressure-sensitive adhesive was placed onto an ink-printed backer (we eventually called this the BackPart) to cause a timed color change. The self- adhesive vinyl (the FrontPart) dissolved the ink, and it slowly migrated into the vinyl. After a period of time, the white vinyl film changed to a pastel shade of the dye color (Figure 2).

Figure 2
Figure 2. Simple VCP construction with only a pressure-sensitive adhesive on an opaque vinyl film. Adapted with permission from TEMTEC Inc.
Figure 3
Figure 3. Multiple-layer VCP FrontPart construction. Dye from the BackPart migrates through the opaque timing layer and concentrates in the enhancement layer, producing an intense image. Adapted with permission from TEMTEC Inc.
After reviewing the patent and its related work, we decided to license the patent even though the product did not work well. In fact, many samples did not work at all! Two major problems with the patented construction had to be solved: The white pigment in the vinyl layer limited the intensity of color change, always producing a light pastel color, even months later; and there was no real time control in the product. The color change was so gradual that one could not tell when it had actually occurred. We called this the “gray-time” problem. We attacked each problem separately.

More intense dyes did not solve the pastel problem. Increasing the dye concentration in the vinyl was impractical because it changed the timing parameters. Serendipity provided a solution to the problem. After our first pilot coating runs with the original two-layer construction, we realized that the FrontPart support film was much too flimsy and thus difficult to handle. We added a transparent film that was adhesively bonded to the front of the two-layer construction to make it more rigid. This adhesive layer happened to be very dye-receptive, and it concentrated the dye in front of the whiting agent after it passed through the timing layer, making the color appear much more intense (Figure 3). This construction solved the color intensity problem without affecting the timing control (3).

The timing control was the second problem to solve. Commercially available vinyl films could include numerous components depending on price and market availability. As long as a manufacturer achieved a product with the desired opacity, flexibility, and adhesive tack, it was acceptable for specific components to vary. Any variation in these components, however, could affect dye migration time. Because the licensor of the patent had no experience with these matters, we had to initiate all reformulation work. This ultimately resulted in several customized multilayer films, rather than the two-layer film-plus-adhesive constructions with which we had begun.

Figure 4
Figure 4. A TIMEbadge is assembled when it is issued (top). The assembled badge changes from a plain background (center) to a patterned background (bottom) when it expires.
In 1988, after 2 years of mixing combinations of resins, TEMTEC introduced the Self-Expiring Time-Dependent Badge (Figure 4) with four time intervals, dictated by the needs of the security market: 2 hours, 1 day, 1 week, and 1 month. The 1-month material actually proved to be our outer limit. We never could produce a longer time interval with the original construction method, even though we were regularly asked for 3-month and 1-year self-expiring badges.

These time badges were an immediate success with new customers, particularly those with several buildings laid out on a campus. Our regular customers began switching from light-sensitive badges because of the improved security and effectiveness of the time-dependent badge.

The time-dependent badge changed our business in more ways than we had anticipated: We printed most of the light-sensitive badges with light on our custom-made “Flash Printing” machines (1, 4, 5). We now discovered that we needed real printing presses because time badges had to be printed in ink. And so we purchased our first web press and found ourselves in the printing business.

Phase II: Another way to do things

All of the initial self-expiring badges had opaque white FrontParts. Because the dye is absorbed by the adhesive and film structure of the FrontPart, it does not become visible until it is displayed on the white background of the opaque FrontPart. One cannot “see” dyes absorbed in transparent films because the migrating dye is indistinguishable from the under lying printed ink dye.

When our customers began requesting self-expiring parking permits, we had to find another way to do things. The original time-dependent badge could not perform properly when exposed to the wide temperature changes inside an automobile. The transparent film technology was developed in 1990 to solve this problem.

With opaque FrontParts, the dye was either visible or not visible, a strictly binary display. We needed a display that could show progressive time, and if the temperature were slightly higher or lower, the analog time would appear a little faster or slower. After months of work, we came upon the idea of using ink dot patterns with different numbers of dots per inch (dpi) to hide the image.

Remarkably, once the FrontPart is placed over the BackPart printing, the migrating ink moves forward very rapidly (perpendicular to the paper) through the 1 mil (0.001-in.) of adhesive, yet this movement is not visible to the naked eye. For the migrating dye to be visible in the transparent film, it must move laterally, parallel to the paper; and this, in effect, causes the dots to grow. Thus, a 10% tint dot pattern will grow to a 15, 20, and 25% tint, and so forth, as time passes. The lateral linear growth of all dot sizes will be the same, whether they are a low or high dpi pattern. Optically, however, the fine dot patterns (those having a high dpi) will increase proportionally much faster than coarser (low dpi) patterns. Because the dots coalesce and form a continuous image faster with higher dpi than lower dpi, the eye can see their images faster, and they become a “chemical clock” based on the dot pattern. Thus, the dye migrates laterally over the white background area between the dots of the printed patterns, forming images based solely on the dpi of the printed patterns.

Figure 5
Figure 5. Self-expiring parking permit before and after expiration, using the transparent film VCP construction.

Characteristics of VCP products
  • They are made from inexpensive label-like materials.
  • They have a shelf life of 2–5 years prior to activation.
  • They are two-component systems.
  • They need some form of activation to initiate the timing sequence.
  • They provide a specific time interval after activation.
  • They develop a change in color or image appearance after the specified time (the color or image may contain information or a message.)
By printing hidden text with nonmigrating permanent ink (exactly the same color as the migrating ink), it is possible to make numbers, letters, or images appear from a camouflaged pattern (Figure 5). In other words, we can create a latent image, completely hidden within a background texture, that can be made to appear by simply applying a transparent pressure-sensitive label over the background (6, 7).

Until 1998, the applications for our new product did not grow much beyond security identification, which continued to be the largest part of our sales and company identity. This was not too bad though because by 1999, TEMTEC was shipping between 1 and 2 million self-expiring ID badges a week, and production of time-sensitive materials exceeded 100 million MSI (1011 sq. in.) a year.

The VCP technology evolves

Like all scientists, we had a propensity to categorize and define, and now that we had two ways to create timed color– image change, we started to look at what we had developed as a technology rather than as two novel products. Hence we coined the term “visually changing paper” (VCP) to denote any two-part paperlike product that changes color after a specific time interval (see box, “Characteristics of VCP products”). The FrontPart (activation cover), a pressure-sensitive adhesive, is placed on top of the BackPart (imager) to activate the product. After a predesignated time, there is a color change revealing images or messages. The time interval can be designed for several minutes, several hours, or days.

Thus, a VCP product has the ability to tell time within limits; to hide information within limits; to prompt or alert you after an elapsed time interval; to entertain you; and to change the status of a document from valid to void, from void to valid, or from one sale price to another (Figures 6–8). Just as the simple scratch-off technology, which was originally invented for lottery-type games, has evolved into numerous new applications, VCP products can now be designed to meet a diverse spectrum of specifications.

We realized that the developed image potentially had a multitude of applications. First, the information in the image itself could be the entire purpose of the VCP. Alternatively, the passage of the specific time interval shown by the developed image could serve a practical use. This timing process could, for example, be a reminder to perform a task or an alert of a passed deadline. The image could be a solid color, words displaying a message like “10% Off Your Purchase”, a corporate logo, or status such as “EXPIRED”.

Each product and market application of VCP has its own technical requirements. When creating a VCP product, the designer must consider the various factors involved in the uses of the product:

  • What kind of printing press and level of printing expertise are needed for production?
  • How long is the interval between activation and image or color change?
  • Is the BackPart image visible or hidden before activation?
  • Is it necessary for the developed image to be permanent or nonblurring?
  • Is a short color change time (short gray-time) important?
  • Is the FrontPart construction transparent or opaque?
  • How many developed colors are in the image?
  • Is a specific BackPart substrate required?
  • Will this be a tamper-evident, secure product?
  • Will this product be temperature-sensitive or used at constant temperature?

Here are a few examples of VCP applications that are currently in use.

Self-expiring security badges. Over the past few years, the primary use of VCP technology has been the self-expiring visitors’ badge. Whereas conventional badges can be reused by anyone, at any time, self-expiring badges prevent reuse by changing color (showing “expired”), thus eliminating the problem of lost valid badges.

This core product line, enhanced over the past 12 years by product and process improvements (which have resulted in more than a dozen VCP patents), has provided the momentum and revenue to develop the VCP technology for other market applications.

Self-expiring wristbands and passes for event control. Identifying people and preventing them from transferring their tickets or passes are perennial problems for event managers. Because these kinds of tags and passes are often highly prized as souvenirs, they are even more likely to be saved, thus presenting a unique security problem. The VCP products that have proven successful in these situations are self-expiring tags for dugouts, golf courses, backstage areas, and other strictly controlled sites.

Venues that present a difficult environment for people control are what we can call “open door” locations. These can be fairgrounds, racetracks, casinos, and other people-gathering locations where transfer of IDs is common. TEMTEC addressed this application with a self-expiring wristband (called a TIMEband) several years ago, because wristbands have traditionally been used where nontransferability of an ID was of particular importance. Casinos with completely open doors and legal penalties for underage gambling have found the TIMEband particularly effective.

Medical TIMEalerts. Medical alerts have provided a unique set of challenges: For 1-, 2-, or 3-day medical applications, the timing must be controlled much more accurately than for security badges, and the color-changing rate (gray-time) must be more rapid than security badge technology permits. These two parameters had to be resolved before VCP products could successfully be used in most medical applications. With the “second-generation” VCP construction, more accurate daily TIMEalert products with shorter gray times are now possible (8).

One medical product has already successfully incorporated a first-generation VCP TIMEalert: A cardiac electrode adhesively attached to a patient’s skin, which must be replaced every 24 hours, incorporates a VCP TIMEalert with a pull-tab on the electrode. After 24 hours, the TIMEalert turns red to alert the nurses that the electrode needs to be replaced. This innovative medical application offers an excellent visual task management tool for nursing staff.

More about the NTTC partnership
VCP is available for commercialization and is being marketed to potential licensees by the Robert C. Byrd National Technology Transfer Center (NTTC), at Wheeling Jesuit University in Wheeling, WV. In addition to its assessment services, NTTC provides federal technology information, technology commercialization training, technology assessment services, assistance in finding strategic business partners, and electronic business development services.

For more information on VCP opportunities, call NTTC at 800-678-6882. A VCP Technology Information Piece is available at www.nttc.edu/products.

Recently TEMTEC contracted with the Robert C. Byrd National Technology Transfer Center (NTTC) in Wheeling, WV, to find new medical applications for VCP technology (see box, “More about the NTTC partnership”). NTTC has identified more than half a dozen applications, ranging from wound management to 1-, 2-, and 3-day periodic task alerts to aid nurses and medical personnel. Basic patient rotation functions can be prompted by VCP TIMEalerts incorporated into patients’ charts and bedside tags.

NTTC has determined that human factor problems associated with efficiently performing short-term periodic medical tasks could be significantly minimized by the use of VCP. VCP could even be helpful in outpatient management, with possibly substantial savings to health care providers, if out patients were issued VCP alerts as prompts in the performance of self-help procedures, such as taking prescribed medication or exercises.

Hidden image promotional products. VCP offers a novel alternative to scratch-off promotional systems. The development of scratch-off promotions in the 1970s was a remarkable means of hiding an image or message: Its manufacturing cost was relatively low, it was secure, and it could be printed on most conventional presses. VCP offers the potential for a competing technology with several additional benefits. First, by delaying the presentation of the message or image after activation, it can prolong user “activity time” with the promotion or game, thus increasing consumer interaction with the advertising message. The user reads the brand name over a period of minutes rather than just the seconds it takes to uncover scratch-off promotions (Figure 9).

Figure 9
Figure 9. VCP wristbands used as pub and bar promotions. The 1 in. x 8 in. wristband (four examples are shown here) is nontransferable, and the attachment adhesive also activates the VCP ink to produce the image.

Second, if the promotion is to be redeemed on-site, the user is forced to remain on the premises the 10, 20, or 30 minutes it takes to develop the message. This proved a highly effective means of keeping patrons at a drinking establishment in the United Kingdom: A VCP promotion in the form of a wristband was issued (and activated) after the customer purchased a drink. The adhesive tab used to attach the wristband to the wrist of the customer not only prevented transfer, it also initiated the development of the VCP message. In about 30 minutes, the patron knew whether he or she had won a free trip to some exotic vacation resort. This was a creative combination of chemical, physical, and psychological principles!

Solving the VCP blurring problem

Unfortunately, the original VCP technology could not be used in most promotional applications because of the tendency of the developed image to blur over time. This had not been a problem in prior applications, primarily in the security field, because the expired badges were not meant to be usable. However, in the case of promotional products involving redeemable prizes, the developed image was the most important part, and it had to remain clear and readable. In fact, there were legal requirements that images be legible for a specific number of weeks or months. Because blurring of the image invalidated the game piece, promotion printers could not use VCP as it existed at that time.

At first, the blurring problem appeared to have no solution, but in 1996, a patent was issued to TEMTEC for a means of retarding the lateral dye migration by making the adhesive as discrete dots (9). The dots of adhesive that touched the migrating dyes would change color, and because they were separated by air gaps from the adjacent adhesive dots, the dye was trapped and would not bleed laterally. However, after 3 years of attempting to manufacture high-dpi adhesive patterns, TEMTEC was forced to abandon this solution as being impractical.

During this time, we worked on developing other ways to prevent blurring of the image. Some involved complicated chemical reactions; others used physical chemical adsorption by the adhesive components. None were totally successful in blur prevention, and many were difficult to manufacture. In 1998, we informed our VCP printers that there was no solution and stopped further marketing of VCP to the promotion-printing industry.

In September 1999, one of those rare, serendipitous events that can occur in scientists’ lives happened to us: Robert Holt, TEMTEC’s director of technical operations, was cleaning up and organizing the hundreds of early VCP samples that were the fruit of our somewhat successful experiments. One by one he sorted through the VCP samples that had been tested years earlier, when suddenly one sample appeared that had not blurred to a uniform color. In fact, it had exactly the same perfectly sharp image that had developed several years earlier. This did not make sense! This could not be! What was different?

He walked into my office and showed me this “nonsense”. I agreed that it should have blurred to a uniform color years ago like the others, but it clearly had not. I told him that although I did not understand how, it must be a solution to the blurring problem, so let’s figure it out. It only took us a few hours.

Figure 10
Figure 10. The non-blurring VCP construction for promotion products shows the two-step process that produces the image and makes the image permanent. Dye from the BackPart (A) moves rapidly into the adhesive layer. The accelerator agent (B) is gradually absorbed into the substrate. When the adhesive layer is depleted of accelerator agent, the permanent dye stops spreading, and the image remains sharp. Adapted with permission from TEMTEC Inc.

The difference, we realized, was that in this sample, a second competing process had occurred that caused the dye to stop diffusing in the adhesive. We determined that the dye does not diffuse in the adhesive without one of the additives and that this liquid additive was being absorbed by the paper substrate of the BackPart. When the additive was completely removed by the paper, the dye stopped diffusing in the adhesive, essentially “freezing” the image and preventing the image from blurring (Figure 10). A patent on this process is pending. I reminded Rob of my favorite quote from Louis Pasteur: “Chance favors the prepared mind.”

The future of VCP

More than a dozen patents have been issued on VCP technology products since 1990. If this is any indication of the application and growth potential of the technology, VCP has a bright future indeed.

One of the great advantages of VCP is that it requires no special equipment; it can be produced on almost any conventional printing press. This feature means mass production potential completely independent of specialized printing processes.

For more information
Lilly, R. TIME-Sensitive Security Badges Display Expiration. Adhesives Age, July 1995, pp 34–38.

Haas, D. J. Self-Expiring ID’s and Security Indicators. Cowise Conference on Advances in Security Printing, Amsterdam, The Netherlands, March 18–19, 1998.
www.tempbadge.com (accessed Dec 7, 2000)

Imagine digital printing presses producing game pieces, with each rotation of the press producing an entirely different hidden message or game answer because two inks, visually identical yet one containing migrating dyes as image-producing moieties, can print an infinite number of different latent image products. Imagine TIMEalerts that can be programmed by the day, a kind of nonelectronic calendar.

Of course, hundreds of people have needed, imagined, and asked for 6-month and 12-month TIMEalerts for showing expiration of products or passes, shelf life, calibration of electronic equipment, ID badges, parking permits, and school and membership IDs. The list goes on. TEMTEC’s current VCP technology allows us to create images that appear within time frames as long as a month. We are currently developing VCPs that will appear in time frames of 6–12 months. These third-generation VCPs should be available within the next year or so.


  1. Haas, D. J. U.S. Patent 4,432,630, 1984.
  2. Kydonieus, A. F.; Smith, I. K.; Conroy, R. A.; Pedicano E. A. U.S. Patent 4,212,153, 1980.
  3. Haas, D. J. U.S. Patent 4,903,254, 1990.
  4. Haas, D. J. U.S. Patent 4,542,982, 1985.
  5. Haas, D. J. U.S. Patent 4,779,120, 1988.
  6. Haas, S. F.; Haas, D. J. U.S. Patent 5,058,088, 1991.
  7. Haas, D. J.; Holt, R. U.S. Patent 5,957,458, 1999.
  8. Haas, D. J.; Haas, S. F. U.S. Patent 5,633,835, 1997.
  9. Haas, D. J.; Haas, S. F. U.S. Patent 5,446,705, 1995.

David Haas is president of TEMTEC Inc. (david@tempbadge.com). He has a B.A. degree in physics and a Ph.D. in biophysics and X-ray crystallography from the State University of New York, Buffalo. He holds more than 30 patents on security-related products spanning numerous scientific disciplines, and he has written and lectured extensively on the potential security applications of a wide range of technologies. He spent 13 years as the principal scientist for Industrial and Security X-ray Systems at North American Philips. He founded TEMTEC in 1981, after developing a working prototype and filing for the first patent on self-expiring ID credentials.

"They caught me sneaking back to the buffet table after my ID badge expired."
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