Prismatic retro-reflective tapes are extremely bright, extending visibility to thousands of feet, surpassing the few hundred feet that older glass bead reflective films are capable of. They were invented by Reflexite in the 1960s by incorporating a cube corner prismatic array with sheeting made of polyester or acrylic. The result was an ultra-bright retro-reflective tape that outshined all existing reflective tape at the time.
These ultra-bright prismatic films are manufactured by large machines in a factory setting. The machines utilize a stainless steel embossing roller with the negative of a prismatic cube corner array pattern on its surface to emboss a prismatic design onto the back of an acrylic or polyester film. This roller is the key component in the production of this product and is normally proprietary in its design.
During production, films are heated and rolled over this special roller under pressure. A smooth roller is on top, and the embossing roller is on bottom. This process results in a film that is transparent on the front so light can pass through, with prisms embossed onto the back for reflectivity. While the back of the film might look matte, the interior side of each prism is highly reflective. Thus, when light hits the film’s transparent top surface and enters the prism array, it is reflected back. The embossed films are then colored through inking or screen printing and prepared for the final stage, which involves adding a backing.
Prismatic films come in two varieties, metalized and air-backed. Both films use the same prismatic array, however, the back side of the prisms are treated in two distinctly different ways. The first method is called metalizing. This is a process by which the backs of the prisms are coated with a metal mirror finish, very similar to what you would find backing a mirror in your home. Metalized retro-reflective films are thin and flexible (bend easily). They are used in more dynamic applications where they may be subject to rougher treatment. One such application is a DOT regulated tractor-trailer rig.
The second method of backing an embossed prismatic film is fusing a white film to the back and leaving air space between the film and the backing using various shaped cells. This is called an air-backed prismatic film. These types of films are more vivid in the daytime due to the absence of a silver metalized backing. They are very bright, but not as bright as some of the brighter metalized films. Air-backed retro-reflective sheeting is very popular on highway and road signs due to its long outdoor life and wide angle of reflectivity.
After the prismatic top layer is backed with either a metalized coating or a white film with an air layer, an adhesive layer is applied. The adhesive will have a release liner that is pulled away when the reflective tape is installed. Different tapes use different types of adhesives, but generally, they are all similar. Some are for cold climate applications, some are repositionable, some are thick for rougher marine surfaces, and some are standard.
Once the adhesive layer is applied, the sheeting is rolled from master logs onto cores in smaller amounts. At this point it can be slit into different widths. Widths range from 1 inch up to 54 inches. Narrow rolls are for striping vehicles, bollards, boats, ships, and other objects that need to be seen at night. Wider rolls are for signs.
Note – Prior to applying the adhesive layer, some rolls are screen or ink jet printed with stripes. An example would be DOT C2 tape for trucks, RGA gate arm tape for railroad crossing arms, and diagonally striped tape for barricades and the backs of fire trucks.
In Summary, here are the basic steps to making retro reflective prismatic sheeting –
- A sheet of acrylic or polyester is created.
- A prismatic array is embossed onto the back of the film.
- The back is either metalized or covered with a white film.
- An adhesive layer is applied to the back.
- Any needed stripes or patterns are applied. (this step can also take place before the adhesive layer is applied)
Steven Cole (Economics, MBA – University of West Florida , Business & Innovation – Stanford University) 25 years of experience in the reflective safety business. Specializing in vehicle accident and rear end collision reduction through increased visibility.