May 06, 2021
HISTORY OF REFLECTIVE TAPE – WHO INVENTED RETRO REFLECTIVE TAPE?
History of Reflective Tape – Who Invented it? (Summary – 3m invented glass bead reflective tape in the 1930’s and Reflexite invented micro-prismatic reflective in the 1960’s.) Lets start with the basics. Reflectivity was not invented. It has always been present in nature. Light bouncing off of objects is why we are able to see those objects. Retro-Reflectivity has also always been present in nature. A cats eye is an example of this phenomenon. (parabolic lens creates a retro reflective surface) So retro reflectivity was discovered, not invented. What was invented was an artificial way to reproduce these characteristics in a usable form. There have been two breakthroughs in the technology of retro-reflectivity. The first is the perfectly spherical glass bead and the second is the man made prism. Both of these discoveries play a big part in the history of reflective surfaces and tape. Lets start with the glass bead. At first, glass beads were applied to the surface of signs and left exposed. The reflectivity achieved was low and in rain it was even lower. Also, over time, dirt would build up between the beads and further limit visibility. This experimentation was a start, but further improvements were needed. In 1937, 3m began developing a film that utilized glass beads bonded to a flexible surface. Their intention was to use this tape on road surfaces but after some durability issues they switched their focus to road signs. To create a brighter tape, 3m created a base layer or film that was a silver color like what is on the back of a mirror. They then applied glass beads to this surface so that about half the bead was embedded in the silver and half was exposed. The silver backing turned the back of the bead into a mirror and the shape of the bead provided for the return of light back to the source. To protect the reflecting beads, a clear layer was applied. This resulted in a much brighter product. The clear layer kept the beads protected and made the tape visible even when it rained. (Note – by tinting the top coat, different colors were created) In 1939, 3m introduced what was known then and today as “engineer grade” reflective sheeting. It was first used in trials in Minneapolis and then in the UK. Later, improvements in engineer grade tape would be made by using advanced mirroring techniques and higher index beads. Also, variations in the top layer allowed some versions to stretch and conform and others to be stiffer. The type that conforms is used for vehicle applications, traffic cones, and road barrels, while the type that is more rigid is used for signs. Engineer grade is also known as an enclosed bead sheeting. This simply means that the beads are immersed in the top coat so that each bead is sealed and protected. There are pros and cons to this type of construction. On the plus side, you can cut the tape and make letters or shapes and the integrity of the glass beads are unharmed. It is for this reason that engineer g...