Retro reflective tape is defined as a film that through the use of glass spheres or man made prisms, reflects light or radiation back to its source. Glass bead tapes reflect using microscopic glass beads that act as parabolas and direct light back to where it came from. Prismatic tapes use man made prisms or mirrors to collect light and send it back to its source. When a transparent color is applied to the surface of either tape the light that is reflected is colored.
Reflective and Retro-Reflective surfaces are often confused with each other. A surface that is Retro-reflective is always reflective but a surface that is reflective is not always retro-reflective. For example, a mirror is reflective but not retro-reflective.
(Note – retro-reflective tape is normally shortened to simply “reflective tape”.)
One of the most important features of retro reflective tape is its ability to collect light, change the color of that light and send it back to its source. That is why stops signs are visible at night in a red color. Yield signs are visible at night in a yellow color. And so on. Without this feature, night time driving would be different than it is now.
The types and colors of reflective tapes are mind boggling. The huge variety of applications are what create the need for all the different intensities, types and colors. For example, trucks need a bright red and white alternating dot tape that can be seen from thousands of feet away. Life vests need a super bright white tape that can be seen from even farther away. The life vest needs a sewable reflective tape whereas the truck does not. Stop signs in neighborhoods can utilize basic affordable reflective tape that uses glass beads for reflectivity. However, street signs on interstates need a more expensive prismatic film. Distance is what dictates this necessity.
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By definition, retro reflective tape is a film that either through the use of glass spheres or man made prisms, reflects light or radiation back to its source. (Source – Cambridge English Dictionary)
This seems like a simple task but in fact it is quite complicated. Just like a portrait that stares at you no matter where you are in the room, reflective tape reflects light back to the source and the source only no matter where that source is positioned. Think of it this way. If you were in the correct position in front of a parabolic shape like a satellite dish and threw a ball into the dish it would always bounce back and hit you. If you throw a ball into the corner of a racquetball court it will hit one wall, then the other, and then come back to you. (In both examples you need to be in the right spot.) Glass bead retro reflective tape (original technology) would be like the satellite dish and prismatic retro reflective tape (newest technology) would be like the racquetball court.
The picture below shows 4 types of tape side by side photographed at different distances with a flash camera. The two tapes on the left are glass bead tapes (engineer and high intensity). The two tapes on the right are prismatic (V92 and SOLAS) As you can see the prismatic tapes are visible from much farther away.
Oftentimes, reflective and retro-reflective are confused with each other. All retro-reflective surfaces are reflective but not all reflective surfaces are retro-reflective. Consider a mirror. It is reflective. However, if you shine a light on it at an angle the light will bounce and hit somewhere else. That is because it is reflective but not retro-reflective. If the mirror was retro-reflective the light would always come back to you.
Here is a diagram that will visually show you how these films work. The first diagram is of a glass bead type reflective film. This is the original technology. The tapes are about 30% efficient and tend to disperse light back in a wider spread. For close up applications this is actually a good thing but for distance applications it is not. The pattern is similar to a flood light. Bright up close but not as bright at a distance.
The diagram below shows how prismatic tape works. Prismatic tape is much more efficient (80%) and reflects light back in a tighter pattern. The reflecting beam would be much like a spot light. The beam stays tight and together out over a longer distance. (example – lighthouse beam which is concentrated via the use of a lens into a tight beam that reaches out to ships.)
Lastly, it is important to remember that the tighter the beam, the more your eyes need to be in line with the source of the light for you to see it when it is reflected back. Car headlights and the drivers eyes are in this basic configuration which is why the driver and passenger see the street signs light up and a by-stander off to one side will see no reflection at all.
You see reflective tape every day and every night. But have you ever stopped to think how it works?
Reflective tape (also known as retro-reflective tape) works by reflecting light back to the light source only. In other words, the tape only lights up for the person with the light source or in line with it.
For example, lets say two people were walking down a street with one person on each side of the street. If person “A” has a flashlight and shines it down the street at some reflective tape on a trailer the tape will light up for them. However, the person on the other side of the street will probably not see the tape light up. If both shined a light down the street they would both see the tape. This happens because the tape contains either glass beads or prisms that collect light, focus it and bounce it back to the source.
How does it do this? Imagine that you are in a round room and you are in the center of the room. If you throw a ball towards the wall it is always going to come back to you. Reflective tape works in a similar manner. The diagram below shows how the glass beads or prisms do this.
As you can see from the diagrams above, the tapes refract or bend light in such a way that it always goes out the way it came in. That brings up another amazing capability of the reflective tape. In the first diagram one person had a light an the other did not. If both had lights, both would see the tape light up. What is amazing about this is that the tape does not have to be horizontal to the viewer for it to reflect light back. It can also shine multiple beams back in multiple directions. Flat against the light is best but even at sharp angles you will get a good return of light.
Another thing to remember about reflectivity is that your eyes have to be in line with the light for you to see the tape reflect. Next time you are out driving at night and are behind a tractor trailer truck notice how you can see the reflective tape light up when you are far back. As you get close at a stop light you will notice that the tape no longer lights up. This is because the angle from the light to the tape and then to your eyes has become too great. In other words, it makes a big difference where the light is in relation to your eyes. If you were holding the light close to your head then the reflectivity would not change as you moved closer. In our article on the difference between glass bead tape and prismatic tape we will cover the geometry of reflective tape in more detail. We have a complete line of products at our main store website www.tapedealer.com .
I have people contact me all the time asking the question “Which reflective tape is the brightest?”. The quick and easy answer to this question would be a white or silver colored micro prismatic retro-reflective tape. Oralite SOLAS would be an example of this grade and color of tape. It is used for marine applications to help rescuers find people or lifeboats. SOLAS by Oralite reflects at up to 1000 candelas and can be seen for thousands of feet away. A colored version of this tape would be Oralite V82 (AP1000). But brightness is not all that a user should look for in a reflective film.
The better question would be “Which reflective tape is best suited for my application?”. In other words brightness is only one factor to consider when choosing a reflective tape. There are other very important factors to consider as well. These are color, flexibility, price, longevity, adhesion, contrast, competitive lighting and light dispersion. It is because of these other factors that so many different types and colors of reflective tape are manufactured. In this article I want to go through the different types of reflective tapes and list their basic characteristics. The main focus will be on brightness but I want to summarize the other factors at the same time.
In each section below you will see that the brightness or reflectivity of a particular tape is affected by type (construction of the tape) and color. The brightest tape in each class is always white (silver). I also want to mention that all tapes are bright close up. It is as you get farther away that you begin to notice a difference.
Note – The picture below shows our white/silver reflective tapes in order of brightness. The least bright on the left and the most bright on the right. Keep in mind that brightness is not always the only consideration. For example, if you wanted to wrap a bike frame in reflective material you would use the tape on the left. (engineer grade) That is because it has other properties that outweigh brightness. In this case, conformability. The good news is that the price also goes up from left to right. Engineer grade is very affordable and SOLAS is very expensive.
Flexible Engineer Grade Type 1
Engineer grade retro reflective tape is a type 1 material with glass beads providing the retro-reflectivity. It is a thin, flexible material and is molded in a single layer which prevents delamination. It comes in the widest variety of colors and is also the least expensive and most popular of all the tapes. It is used in a variety of applications where viewers will be fairly close to the tape itself. Engineer grade comes in a standard and flexible grade. The flexible grade will stretch and is used in applications where conform-ability is important. If you have a rough uneven surface to mark then this is the tape you need. (example – bicycle wrap) This material can be computer cut into letters, shapes and numbers and is widely used on emergency vehicles and signs for this reason. It is often combined with a brighter background so that both colors are reflective but a contrast is still achieved. Because it is a glass bead tape it disperses light in a wide angle. Recommended for applications where the viewer is within 50 yards of the tape.
The estimated brightness of this grade in the different colors measured in candelas is as follows:
White – 108 candelas
Yellow – 88 candelas
Gold – 78 candelas
Orange – 54 candelas
Green – 28 candelas
Red – 21 candelas
Blue – 12 candelas
Black – 10 candelas
Note – there are a variety of other colors in this grade. The main ones are listed above.
Flexible High Intensity Grade Type 3 Reflective Tape
Flexible High Intensity Type 3 Tape is a flexible, stretchable version of our standard high intensity tape. It only comes in three colors, white, yellow and orange. This tape is designed to be used on traffic cones and road barrels, however, it is also great for a variety of other applications where a bright, stretchable tape is needed. For example, hard hats have an uneven convex surface and most tapes will not conform. But flexible high intensity will.
High intensity type 3 tape is made by laminating layers together. The high index glass beads are contained in little honeycomb chambers with an air space above them. This arrangement makes for a brighter tape. Although still thin, this tape is a little stiffer than engineer grade. It is excellent for smooth surfaces and is about 2.5 times brighter than engineer grade. This tape is used in applications that require a viewer to see the tape from medium distances away. It is more expensive than engineer grade but less expensive than prismatic films. This tape also disperses light in a wide angle. This combined with the tapes increased reflectivity makes it light up quicker to the viewer than other tapes. CAD cutting into letters and shapes is not recommended with high intensity. It is very popular for creating sign backgrounds, wrapping bollards, marking loading docks, making gates reflective and other similar applications. Recommended for applications where the viewer is within 100 yards of the tape or in areas where there is competitive lighting.
White – 250 candelas
Yellow – 170 candelas
Orange – 100 candelas
Green – 45 candelas
Red – 45 candelas
Blue – 20 candelas
Non Metalized Micro-Prismatic Reflective Tape – Type 4 (also known as high intensity prismatic HIP) Oralite 5900
Non Metalized micro-prismatic tape is made by laminating a layer of prismatic film onto a honeycomb grid and white backing. It is similar in construction to high intensity glass bead tape but with the air chamber below the prisms. (air backed micro-prisms) The white backing makes the tape color more vivid. It is a little more expensive than high intensity but less expensive than metalized micro-prismatic. Best if applied to a smooth surface. This film is visible from much farther away than high intensity or engineer grades and is great for applications where the viewer is far away from the tape.
White – 360 candelas
Yellow – 270 candelas
Orange – 145 candelas
Green – 50 candelas
Red – 65 candelas
Blue – 30 candelas
Metalized Micro-Prismatic Reflective Tape – Type 5 – Oralite/Reflexite V82
Metalized micro-prismatic reflective tape is the top of the line when it comes to durability and reflectivity. It is molded into one layer which means you never need to worry about delamination. This is especially good when using the tape in a dynamic environment where it may be abused. You can beat it up and it still reflects. It is made by coating the back of a micro-prismatic layer with a mirror coating and then applying adhesive and a release liner to the back. It is more expensive to make but well worth the effort. Because it is a single layer film it can be CAD cut into letters and shapes. This material can be used for all applications as well as those where the viewer is in excess of 100 yards from the tape. In most cases, this reflective tape can be seen from over 1000 feet away. This makes it excellent for highway applications or applications where the tape will be shining through snow or rain.
White – 750 candelas
Yellow – 525 candelas
Green – 130 candelas
Red – 130 candelas
Blue – 55 candelas
V92 Metalized Prismatic Reflective Tape – (comparable to type 5)
V92 Reflective Tape by Orafol/Reflexite is very similar to V82 only it is a little less expensive and slightly less bright when it reflects.
V98 Conformable Reflective Tape by Orafol/Reflexite – Metalized Prismatic – (comparable to type 5)
V98 is designed for vehicle graphics and is also cuttable on a plotter. I have found it to be the easier to cut than the V82 or V92 films. It is a little thicker and has a slightly more rubbery texture. It reflects at 750 candelas for white. It is very popular for striping emergency and utility vehicles.
Lastly, Reflexite SOLAS reflects at over 1000 candelas. It is available only in white/silver. It has a greyish silver look in the daytime but is bright white at night. It can be seen from over a thousand feet away in good and bad weather conditions.
Technical data sheets on retro reflective tape often reference the terms “Entrance Angle” and “Observation Angle”. Normally something to the effect of – (Observation Angle : .20 / Entrance Angle : -4) or (Observation Angle – .50 / Entrance Angle : 30), where the observation metric is normally very small, and the entrance metric being much larger. Most readers gloss over these metrics without understanding what they are, or their importance. The purpose of this article is to explain what these two terms mean, and to explain why they are important when it comes to retro reflective sheeting and photo-metrics.
Entrance Angles for Reflective Sheeting
An Entrance Angle is referring to the angle at which a beam of light enters a sheet of retro reflective sheeting. It is calculated with a perpendicular line from the sheeting being “0” degrees. As an example, light entering a sign at a perfect right angle like a T would be a “0” degree entrance angle. From a long distance, the headlights of an automobile would strike a post mounted sign almost perpendicular with a low entrance angle. Then when the vehicle got closer to the sign, and it was off to one side, the angle of entry would increase. As you can see from the diagram below, an entrance angle is measured by the number of degrees from the perpendicular, to the beam of light.
Typical retro reflective sheeting can reflect up to an approximate 60 degree entrance angle from the perpendicular. If the angle is above that, the glass beads or micro prisms in the sheeting begin to be ineffective. To test this, walk around a sign, continuously shining a light on the surface. When your beam is hitting the sign squarely, it will be bright. However, as you get closer to your beam becoming parallel (off to one side) to the reflective sheeting, you will see less return of light and then no reflection. That is due to the entrance angle being too sharp.
Observation Angles for Reflective Sheeting
The Observation Angle is always quoted along with the entrance angle when describing the reflectivity of a sheeting product. It is normally a very small number. It refers to the difference between the entrance angle and the eyes of the person viewing the sign or retro reflective sheeting. So basically it is the difference in angle between the beam of light going from headlights into the film, and the beam of light returning to the eyes of the driver. To be clear, observation angle is NOT measured from the perpendicular. As an example, the observation angle for a person in a sports car would be narrow, however, for a person in a large truck, the observation would be much greater. This is because their eyes are a greater distance from their headlights.
The diagram below shows how observation angles differ in different vehicles. It has everything to do with how far the viewer or drivers eyes are from the headlights of the car or whatever the light source may be. If you look carefully at the diagram, you can see that for trucks, the observation angle is generally much more, which creates a reduction in the amount of returned light they can see. This is because the greater distance is putting their eyes at the outer edge of the cone of reflectivity.
Wider observation angles present a challenge for highway departments of transportation responsible for road signage, because in traffic, every vehicle, both small and large, needs to clearly see signage. Many reflective tape manufacturers, in an effort to offset this issue and keep signage bright at night, have developed wide observation retro reflective sheeting. Oralite 7900 Wide Observation and Oralite 9900 All Observation films are two examples. These reflective tapes are brighter overall, and spread out light a little more so that viewers at greater angles can still see the film. With this technology, the cone of reflectivity is brighter and broader.
So the question is, why don’t all tapes spread out the light like wide observation films. The reason is that for some applications, tapes need to be seen from a very long way away, like in marine environments. For that situation, tapes with tighter observation angles and longer sight distance are used. Oralite M82 FD1403 or 1404 SOLAS tapes would be an example of this. These types of films are generally not used for sign sheeting.
So in summary, the entrance angle is the angle that light strikes the surface of the sign, with zero being the perpendicular or straight on. The observation angle is the angle that the viewers line of sight is from the entrance angle, or beam of car light. The farther the viewers eyes are from the light source, the greater the observation angle. If a person held a light on their nose, the observation angle would effectively be zero.
If you have any questions about reflective tape, and which sheeting is best for your application, use the contact button above to send me a message.
The Science of Color as it Pertains to Retro Reflective Signs
Color is a universal language. At traffic lights across the country and around the world, drivers understand to stop on red and to go on green. For signs, drivers recognize yellow as caution, red as stop, white as the speed limit, and green as information. These colors and the shape of the sign convey a message before we see what is written on the sign and keep us safe as we drive on American highways.
In the field of retro reflective sheeting on road signage, color consistency is very important. It is for this reason that in the US, sheeting used on signs must meet ASTM standards. This is because a yellow yield sign in Montana needs to be the same color as a yellow yield sign in Florida, and a red stop sign in New York needs to match the color of one in California.
Note – Sign shapes are specified by the MUTCD (manual for uniform traffic control devices) Color, reflectivity and other attributes are specified by ASTM (American society for testing and materials) ASTM sets standards, and other organizations such as state DOT’s require adherence to those standards. This is all done for safety and uniformity.
So why the stringent color requirements? Humans respond to color, and since the eye is so sensitive to it, even slight differences are noticeable. So if a yellow on one yield sign is different from another, a person will notice. And if the differences are substantial enough, one sign may be disregarded by the human brain. This is because much of color recognition in traffic is subliminal or automatic. So color is important.
Note – to test your color sensitivity, look for cars that have been wrecked and repainted. If only a door was damaged and repainted, you will most likely be able to sense a slight difference in color, even though the body shop made great efforts to match. Or in your home, when you have colors matched at Lowes and go to touch up a room, you will see a difference and often have to paint and entire wall to get a match.
The colors of sign sheeting are measured in terms of Chromaticity. Chromaticity is defined as an objective, numerical indicator of the quality of a color that stays constant without regard to the light that illuminates it. In other words, it is the quality of color of an object, independent of brightness. Color science uses chromaticity to explain and quantify how we determine different colors. It breaks down colors into metrics, or numbers. Chromaticity measurements and metrics also make colors reproducible with consistency. Consistent chromaticity confirms that an object emits the color you need to see, which for things like sign sheeting, are very specific.
For retro reflective sign sheeting to be approved for use on highways, certain specifications must be met. Weatherability, Reflectivity, Daytime Chromaticity (color), Nighttime Chromaticity (color) Adhesion, Shrinkage, Solvent Resistance and Specular Gloss are some of the specs. Of these, Chromaticity is one of the more important metrics, as is reflectivity. So sign sheeting must be tested for compliance before it is approved. This assures that all sign sheetings, regardless of the manufacturer, fall within certain parameters. So whether a sign is sheeted with Retro Reflective film from Avery, Orafol, Nikkalite, or 3m, they will look almost exactly the same.
How Chromaticity is Measured
Chromaticity is a combination of two measurements. One is hue, which is formally described as the property of colors by which they can be perceived as ranging from red through yellow, green, and blue, as determined by the dominant wavelength of the light. These colors can be described in terms of the wavelengths that create them, and for uniformity, wavelength can be objectively measured and quantified.
The other measurement that goes into chromaticity is “colorfulness”. Colorfulness is the attribute of a visual perception according to which the perceived color of an area appears to be more or less chromatic. This just means that color is dependent on more than the wavelengths of light that are being reflected to the human eye, it also depends on the intensity of the light falling on the surface that is reflecting them. During tests for chromaticity for sign sheeting, a constant level of a certain kind of light is maintained for uniformity.
When testing for Chromaticity, a “CIE D65 Standard Illuminant” compliant light source is used. It simulates the color of sunlight on a slightly hazy day. 4 tests must be done and the results of each recorded to qualify a material to meet ASTM color specification standards.
Eye Sensitivity
The perception of color by the human eye is the one factor that engineers have no control over. The perception or recognition of color begins when light hits the retina, which contains photoreceptors called rods and cones. Rods are more sensitive and are responsible for our low-light or night time vision. Cones are less sensitive and are responsible for our day time and color vision. As light strikes the photoreceptors in the human eye, a nerve impulse is sent to the brain, which interprets the light according to its color.
Note – Numerous tests have shown that Fluorescent Lime is seen by the human eye more prevalently than other colors. Lime and Red together provide the best contrast and the quickest recognition. This is why you see lime and red used on the backs of fire apparatus.
Summary
In summation, color chromaticity standards assure that people recognize the intention of a sign both day and night, prior to being able to read what it says. Both the shape and color of the sign assist in making this happen. It is for this reason that all 50 states require conformance to ASTM color and reflectivity standards when it comes to retro reflective sign sheeting.
Not all retro reflective tape has to meet these standards. Only sign sheeting. Other tapes are used for a variety of other purposes such as vehicle conspicuity and marine safety. For these tapes and applications, other regulations often apply.
Difference Between Glass Bead & Prismatic Reflective Tape – (www.tapedealer.com)
There are two types of reflective tape, glass bead and prismatic. Glass bead tapes were the first reflective tapes and then in the 1960’s prismatic tape was invented by Reflexite. It is interesting that prismatic tapes have not replaced glass bead tapes. Even after 50 years. This is because both have characteristics that make them desirable in certain situations.
Glass Bead Reflective Tapes
Glass bead tapes use microscopic glass spheres to bend and reflect light back to the light source. Because of the imperfections and curved surfaces in glass beads, tapes made with beads are less reflective than tapes made with prisms. Glass bead tapes are about 30% efficient. This is a disadvantage. However, there are three advantages that glass bead tape has over most prismatic tapes. First, glass bead reflective tapes are much more affordable. This is because they are simpler to manufacture. Second, most glass bead tapes are CAD cuttable meaning that you can cut letters, number and designs out of the tape and create reflective signs or graphics. Third, glass bead tapes reflect light back at wider angles. In other words, glass bead tapes are sort of like flood lamps whereas prismatic tapes are more light spot lights. The diagram below shows this.
As you will notice from the diagram above, the glass bead tape disperses light more than prismatic tape. That is why it is not as bright at farther distances. However, at close distances the wider angle of dispersion can be an advantage. Let say for example that a fireman is wearing a high intensity glass bead tape on his equipment. When someone shines a light towards him the tape will light up for the person with the light and, if you are fairly close, it will light up for you as well. Also, as the beam nears the fireman, his tape lights up quickly. Again, this is because of the dispersion of the light. Many people prefer the high intensity glass bead tape for close up applications. For long distance applications the prismatic is always better. This is because the glass bead tapes completely disappear at a distance of a few hundred yards whereas a prismatic tape is still visible for over a thousand yards or more.
There are two basic types of glass bead reflective tapes. The first is a standard engineer grade or type 1 tape. White engineer grade tape reflects at about 75 candlepower. This is the most popular tape and is found on car tags, stop signs, speed limit signs, emergency vehicle striping and graphics, etc.. The second type is high intensity or type 3 tape. This tape has higher index beads and encapsulates them in a honeycomb pattern. White high intensity tape reflects at about 250 candlepower. You will find this type of tape on traffic cones and road barrels.
Prismatic Reflective Tape
Prismatic is more efficient and returns about 80% of the light sent to it. Therefore it is brighter than glass bead tapes. Prismatic tape reflects light via man made prisms. Since the mirrors are flat and not curved they are more efficient. The light sent from the tape is more focused and can therefore travel farther still be seen. For long distance applications like DOT regulated trucks or coast guard search and rescue a prismatic tape is a must. There are several grades of prismatic tape starting with a type 4 and going up to a type 8. Because they are all so bright, to the human eye there is very little noticeable difference in the various prismatic types. It is when you get far away from the tape that you notice a difference. The farther away you need to see the tape the higher the type needs to be. The brightest tape that I know of is SOLAS coast guard approved tape. It is used for offshore applications and is vital for search and rescue operations where the victim may be a thousand or so yards away.
Many prismatic tapes are too thick to CAD cut. The exception would be Oralite metallized prismatic tapes. Oralite (formerly Reflexite) invented prismatic tapes and makes their metallized tapes in a thin single layer. This has two advantages. Number one, the tape will not delaminate like the thicker tapes. Number two, it can be CAD cut with a vinyl cutter/plotter. This is a huge advantage. Prismatic graphics show up several times farther than standard glass bead graphics. The advantages of this are obvioius.
Some different types of prismatic tapes are DOT C2 Tape, FRA Railcar Tape, SOLAS coast guard tape, School Bus Tape, Chevron Reflective Striping, and Sign Sheeting.
In summary, both glass bead and prismatic tapes have their purpose and will continue to keep people safe and visible for years to come.
When it comes to retro-reflective films, a common misunderstanding is that Type 1 through Type 11 designations represent the brightness of the tape from lowest to highest. While this is true to an extent, the type, (1-11) actually applies to the application of each tape in road way signs and traffic situations. In other words, each ASTM D4956 Type, 1-11 has a different purpose in traffic. Brightness or Luminous Intensity is only one characteristic, and as you will see from the metrics below, an increase in reflective brightness does not always correspond with an increase in Type.
Type 1 (Engineer Grade) – Road way Signs, Construction Zone Devices, and Traffic Delineators
Type I Retro-reflective films – Medium intensity retro-reflective films normally referred to as an “engineering grade”. This is a very common and popular film, and is available in a multitude of colors. Type 1 tapes are used in both commercial and consumer applications. In commercial applications it is use for permanent road way signs, construction zones, and traffic delineators. Normally an enclosed lens film which refers to glass beads that are completely surrounded by the flexible polymer. These types of films can be cut without effecting reflectivity at the edges since all beads are surrounded by polymer. Type 1 engineer grade and Type 2 super engineer grade are the only two films considered to be enclosed lens films. This is the most common film for cutting letters, logos, and graphics. After cutting, edges DO NOT have to be sealed.
Light characteristics for Type 1 Sheeting (mimimum coefficient of reflection)
Type 2 (Super Engineer Grade) – Road way Signs, Construction Zone Devices, and Traffic Delineators
Type 2 Retro-reflective films – Medium High Intensity retroreflective sheeting often referred to as “super engineer grade”. Common commercial applications for this reflective film are permanent road way signs, construction zone devices, and traffic delineators. Type 2 reflective is typically an enclosed lens glass-bead sheeting like engineering grade. Easily CAD cuttable like engineering grade, only brighter. Twice as bright as type 1. After cutting, edges DO NOT have to be sealed.
Ligh characteristics for Type 2 Sheeting (mimimum coefficient of reflection)
Type 3 (High Intensity Glass Bead) – Road way Signs, Construction Zone Devices, and Traffic Delineators
Type 3 Retro-reflective films – A high-intensity glass bead retroreflective sheeting used for permanent road way signs, construction zone devices, and traffic delineators. Rough Typically an “Encapsulated Lens” glass bead retroreflective material meaning that individual glass beads are encapsulated in cells and more exposed to incoming light. About double the brightness of Type 2 films. While this material can be CAD cut, it is normally not used this way since cutting the film exposed the edges of the cells that are filled with glass beads. After cutting, edges SHOULD be sealed to protect the edges.
Light characteristics for Type 3 Sheeting (mimimum coefficient of reflection)
Type 4 (High Intensity Prismatic) – Road way Signs, Construction Zone devices, and Traffic Delineators
Type 4 Sheeting —A high intensity prismatic retroreflective sheeting. This sheeting is normally an Unmetallized Microprismatic retroreflective element (aka Air Backed) material. Typical applications for this material are permanent road way signing, construction zone devices, and delineators.
Light characteristics for Type 4 Sheeting (mimimum coefficient of reflection)
Type 5 Retro-reflective films – A super-high intensity prismatic retro-reflective sheeting. This sheeting is typically a metallized microprismatic retroreflective element material and is commonly used for traffic delineators and channelizers. The term metallized refers to a silver aluminized backing much like a mirror has. (versus a white backing for non metallized air backed films) This mirror backing allows the tape to reflect very brightly and maintain an ultra thin construction. The tape can also be CAD or scissor cut without the need for edge sealing since it is constructed in a single layer. Type 5 is the only metallized prismatic film in the list of Type 1 – 10 films listed in this article. It is often used in non traffic applications due to its brightness, ability to be CAD cut, and its ultra thin rugged design.
Light characteristics for Type 5 Sheeting (mimimum coefficient of reflection)
Type 6 – Temporary Roll Up Signs, Warning Signs, Traffic Cone Collars, and Post Bands
Type 6 Retro-reflective films – A flexible elastomeric high-intensity prismatic retro-reflective sheeting without adhesive. This sheeting is typically a vinyl based micro-prismatic retro-reflective material. It is designed to be rolled up and stored, without damaging reflective components within the film. The sheeting is typically lettered and used when roadwork is in progress or an emergency situation necessitates temporary signs. Commonly used for lime or orange temporary roll-up warning signs, white traffic cone collars, and post bands.
Light characteristics for Type 6 Sheeting (mimimum coefficient of reflection)
Type 7 – Road way Signs, Construction Zone Devices, and Traffic Delineators (not commonly used – Type 8 being more popular)
Type 7 Retro-reflective films – A super high intensity prismatic retro-reflective sheeting having the highest retro-reflectivity characteristics at LONG and medium road distances. (brightest film, along with Type 8) as seen by the reflectivity values of Table 1 at 0.1° and 0.2° observation angles) This sheeting is typically an unmetallized air backed micro-prismatic retroreflective material. Common applications for this material are permanent road way signs, construction zone devices, and traffic delineators.
Light characteristics for Type 7 Sheeting (mimimum coefficient of reflection)
Type 8 – Road way Signs, Construction Zone Devices, and Traffic Delineators (more commonly available sheeting)
Type 8 Retro-reflective films – Super high intensity prismatic retro-reflective sheeting having the highest retro-reflectivity characteristics (along with Type 7) at LONG and medium road distances. (see RA values of Table 2 at 0.1° and 0.2° observation angles) This sheeting is commonly an unmetallized air backed microprismatic retro-reflective material. Common applications for this material are permanent road way signs, construction zone devices, and traffic delineators.
Light characteristics for Type 8 Sheeting (mimimum coefficient of reflection)
Type 9 – Road way Signs, Construction Zone devices, and Traffic Delineators
Type 9 Retro-reflective films – Very-high-intensity retroreflective material having highest retro-reflectivity characteristics at SHORT road distances as determined by the RA values of Table 3 at 1° observation angle. This sheeting is typically an unmetallized microprismatic air backed retroreflective material. Typical applications for this material are permanent road way signing, construction zone devices, and delineators.
Light characteristics for Type 9 Sheeting (mimimum coefficient of reflection)
Type 10 – Road way Signs, Construction Zone devices, and Traffic Delineators
Type 10 Retro-reflective films – A super-high intensity retro-reflective material having highest retroreflective characteristics at medium road distances as determined by the RA values of Table 4 at 0.1° and 0.2° observation angles. This sheeting is typically an unmetallized microprismatic air backed material. Typical appli- cations for this material are permanent road way signing, construction zone devices, and delineators.
Light characteristics for Type 10 Sheeting (mimimum coefficient of reflection)
Type 11 – Super High Efficiency Road way Signs – Overhead Signs
Type XI — is a reflective sheeting manufactured as an unmetallized cube corner micro-prismatic air backed retro-reflective material. This super-high efficiency sheeting is designed to perform best at both medium and short sight distances. This makes Type XI a very adaptable sheeting that agencies can use to improve road safety. A typical use for Type 11 sheeting would be overhead signs on interstates. Its high performance eliminates the need for external lighting which results in asubstantial cost savings on maintenance and energy costs.
Light characteristics for Type 11 Sheeting (mimimum coefficient of reflection)
(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.
Potters Glass Beads
Potters Beads
Potters, an American company, began producing tiny glass beads or spheres in the early 1930’s. The beads that Potters created were very round or spherical which was important. Only a perfectly round and clear bead would send light back to where it came from. These very small and very round glass beads were used on cinema screens to make them brighter and also on road stripes to make them more reflective. To this day glass beads made by Potters are still used on road stripes. The paint is applied and while still wet the beads are sprinkled on top. That is why at night the painted lines show up so well. This is all because the round beads sit up from the paint surface just a little, take in light from your headlight, and bounce it right back to you. Sort of like a parabolic mirror.
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 grade tape is so popular in the graphics industry for letters, shapes and designs cut in the material. On the negative side, this type of construction reduces the overall reflectivity of the beads. Engineer grade or type 1 film reflects at a rate of about 75 candelas for white and less for the colored films. The same as your car tag. For applications within 100-150 feet, this is more than sufficient.
High Intensity Grade Glass Bead Reflective Tape – ASTM D4956 Type 3
In 1971, 3m introduced their “high intensity” reflective sheeting. This tape or sheeting is different from engineer grade in that the beads are enclosed in cells but not completely encapsulated. They sit in a honeycomb type hexagon cell and are sealed in by a clear or colored top coat. Also, instead of sitting in a metalized layer, the actual beads themselves are metalized. Being metalized themselves and not being encapsulated makes the beads much more reflective. In fact, high intensity sheeting is about three times more reflective than engineer grade sheeting. High intensity sheeting is very popular for sign backgrounds. Since cutting the tape opens up the cells and allows water to intrude it is not often used for letters or shapes. (NOTE- only the cells that are cut are affected. All other cells remain sealed. Plus the cells are very small) High intensity or type 3 sheeting represents the brightest tape that can be created using glass bead technology. Roughly 250 candelas for white. High intensity sheeting was and is used extensively in sign making. Since signs are static the material performs well. And the extra reflectivity allows vehicles to see it much farther away.
Competition Enters the Glass Bead Reflective Tape Market
In the 1970’s several companies also entered the glass bead reflective tape market. Avery Products launched a line of engineer grade reflective tape in the United States. Avery merged with Dennison and became Avery-Dennison in 1990. Seibu International, a Japanese company, launched a similar line overseas. Their sheeting was known as Seibulite. In 1991 Seibu was purchased by Nippon Carbide (also a Japanese company) and the product was renamed Nikkalite.
Prismatic Reflective Tape – ASTM D4956 Type 4 and above
In 1963 the American Rowland brothers, of Rowland Products Inc, began developing micro-prismatic retro-reflective sheeting. This was done in cooperation with Luce Reflexite and later with Fresnel Optics. These companies were later merged together. This product was patented in 1970 and a company called Reflexite was created to produce and market the new product. Reflexite began selling micro-prismatic sheeting in 1973. Just as 3m is credited with the invention of reflective glass bead tape, Reflexite is credited with the invention of prismatic reflective tape. (Reflexite has since been purchased by Orafol)
Prismatic sheeting reflects light back to the source just like glass bead tape does. The only difference is that prismatic retro reflective sheeting does this much more efficiently. Instead of light entering a glass sphere it enters a triangular prism. Micro prisms have straight sides that allow more light to enter and exit the prism. Prismatic tapes are about 80% efficient while glass bead tapes are about 30% efficient. Also, prisms are man made and are placed side by side in a tight array while glass beads will have some dead space between the beads. Just like glass bead tape the microprisms are also mirrored on the back. The front of the prism allows light in and the back reflects it and sends it back out. Like glass bead tapes, micro-prismatic or cubed cornered tape comes in two types, metalized micro-prismatic and encapsulated lens.
Metalized film is popular in the graphics industry because it is made in one thin layer and will not delaminate. It has the same positive features that engineer grade has but is 10 times brighter.
Encapsulated or non metalized prismatics are thicker and are more prone to delamination. However, the colors are a little more vivid due to the absense of the silver mirror coating. Because of this, for sign sheeting, non metalized films are preferred.
In the 1980’s Stimsonite, a major manufacturer of road reflectors launched their own prismatic sheeting. They were subsequently purchased in 1999 by Avery-Dennison who was then able to add Stimsonite micro-prismatic sheeting to their glass bead line.
Nippon Carbide, the company that acquired Seibu, developed their own line of micro-prismatic films and were then able to offer a full line of reflective products from engineer grade glass bead tape to prismatic sheeting.
In 1989 3m launched a prismatic product known as diamond grade sheeting thus completing their line of reflective sheeting products.
In 2012, Reflexite Americas merged with Orafol. Orafol is a German company and has an impressive global presence. Before the merger, Orafol had a large line of reflective films. (mostly glass bead technology) This line more than doubled with the addition of the Reflexite prismatic reflective products.
At the present time, there are four major competitors in the reflective tape business. These are 3m, Orafol/Reflexite, Avery Dennison and Nikkalite. All four companies have a glass bead and prismatic line. 3m is actually the least competitive in the glass bead market now. Their strategy has been to focus on prismatic tapes and slowly discontinue the glass bead line. Whether this is a good move on their part is yet to be seen.
The history of reflective elements on signage began with the creation of the Cataphote or glass cats eye by an inventor named Percy Shaw. The little glass cataphotes were used in the center of roadways, and also on signs themselves. Up until this time, signs were painted in different contrasting colors, but with no reflective qualities whatsoever. So often they were invisible at night when they needed to be seen the most. Percy Shaws invention changed that, and for the first time, you could actually see the word stop on a stop sign at night. In 1927 Percy Shaw applied for and was granted a patent for his invention. His Cataphotes became a big hit and sparked a race to find a better way to light up road signs at night.
A little earlier, in 1914, Rudolph Potters began experimenting with ways of mass producing tiny perfectly round retro reflective spheres. These round glass spheres would reflect like a Cataphote, but would be much smaller, the size of a ball in the tip of a ball point pin. Also, these beads would not be used one at a time like Cataphotes. Instead they would be used in mass quantities to make large areas retro reflective. Mr. Potters invention was successful, and much later in 1941 he applied for and received a patent for the process and the equipment needed to produce glass beads. This invention is the pivotable discovery that ties early reflective signs that were primitive and used cataphotes, to modern day signs that use true retro reflectivity across the entire surface of the sign.
In the beginning, retro reflective micro beads were used in conjunction with a binder or paint to create reflective surfaces. Movie screens are one example, and road striping is another. Just like a Cataphote, light enters the glass beads, is bent, bounced, and returned to the source, wherever that may be. The spherical and parabolic shape of the bead is what makes this possible. So in contrast to the Cataphote, which covered maybe a square inch each, large areas could be made reflective by binding the beads with a coating and covering the surface. To work, all that is necessary is for the tops of the beads to be exposed so light can enter and exit. (Note – a fully encapsulated bead will not reflect since light cannot reach it) So when beads are on top of a surface, they make the surface retro reflective. This is important, because these applications are what led to further discoveries which are described below.
The Beginning of Modern Reflective Traffic Signs (From Road Stripes to Reflective Signs)
Before there were reflective signs, there were reflective road stripes. Glass beads from Potters were distributed on wet paint to make them reflective at night. At night, a stop sign could not be seen, however, the stop bar, if it had glass beads on it, could be.
The history of modern day reflective traffic signs began in 1937, when a 3m laborer was tasked with the job of creating a new method for making reflective center lines on roads in Minnesota. The goal was to make a tape that gave the same effect as the method at the time of dropping glass beads on wet paint. Basically a roll of road striping. The laborers name was Harry Heltzer. In any event, Heltzer accepted the job of developing this new product and set about trying to determine how to make it work.
A highway official suggested that he embed glass beads into a stripe, giving him the idea of a glass bead based reflective tape for pavement. His first mission was to source glass beads that were retro reflective and small enough to be imbedded into a carrier such as a tape. Mr. Heltzer used double-sided tape with an adhesive top and bottom and embedded the beads on one side. The other side would be used to adhere the stripe to a road. What Heltzer created did in fact reflect, and did create a reflective stripe on pavement. The issue however, was keeping the stripe adhered to a cold Minnesota roadway and keeping it reflective for a long period of time. Basically, for the product to be commercially viable, it had to work as well as reflective paint. So the invention worked, but not well enough to be used commercially. But all was not lost, while this first attempt at making reflective road striping on a roll did not pan out, it did lead to another amazing invention that changed night time safety forever.
(Note – 3m did not give up on reflective road striping and later on in 1974, patented a product that we now know as Stamark. Reflective road stripes on a roll.)
Harry Heltzer and his team, with the knowledge and experience gained from reflective road striping in hand, began development of a new invention that would soon evolve into a product known as engineer grade reflective sign sheeting. A product used to this day. The idea was to take the road stripe idea that did not work so well, and transfer it to a sign where road wear was not so much of an issue. In any event, the invention began as a fairly crude product that was functional, but with drawbacks. Three of which were, wet reflectivity, dirt and grime on the beads, and an overall reflectivity deficit.
In the first iterations of the new product, glass beads were simply embedded into the surface of a film and left exposed so they could reflect light. This was much like the road striping product where the beads were exposed on top of double stick tape. The film was then placed on a sign. The reflective sheeting worked somewhat, however, when dirt got between the beads, or when it rained, the beads stopped returning light in amounts sufficient to see. And overall, even without these issues, the brightness was disappointing.
So in summary, in early iterations, reflectivity achieved was low and in rain or when the sheeting accumulated dirt and grime, it was even lower. This experimentation was a good beginning, but further improvements were definitely needed before it was commercially viable. So Heltzer and his team went back to the drawing board so to speak, and worked on solving these issues. They needed the tape to be brighter, it needed to reflect in all weather conditions, and lastly, the beads needed a way to stay clean.
Note – A single glass bead will reflect by itself on pretty much any surface. When applied in a large area, the apparent reflectivity greatly increases since all the beads are returning light together. When on a light colored background they do even better. But on a mirrored background, like metallic silver, they reflect the best. And this is what the team discovered.
To increase the return of light, 3m created a base layer or background on a film that was a silver color like what what you would find on the back of a mirror. Perfectly round glass beads were applied to this silver surface with half the bead embedded and half exposed. In essence, the silver backing transformed the back of the glass bead into a mirror. And not just any mirror, because the shape of the bead also provided for the return of light back to the source. So what was invented was a retro reflective glass bead, with a mirror finish on the back only. An innovation that increased reflectivity substantially. This took care of the issue with brightness and offset the other issues as well. But more work needed to be done.
After brightening up the film, the issue of not reflecting when dirty or wet needed to be addressed. The beads needed to be protected, while still being allowed to reflect. To protect the beads, a very thin clear layer of polymer was applied over the top of the film that sealed the beads without hindering reflectivity. This was tricky, but they figured it out. The clear layer kept the beads from accumulating dirt and also made the tape visible even in rain. (Note – by tinting the top coat, it was discovered that different colors could be created)
In 1939, 3m introduced what was known then and today as “engineer grade” reflective sheeting. The invention was filed with the patent office in 1941, and officially patented in 1943. The patent was titled, “Reflex Light Reflector“. The new product was first used in trials in Minneapolis and then in the UK. After a short time, and plenty of marketing, reflective signs made with 3m’s new product took off.
Of note is that the film was CAD or plotter cuttable, so creating letters was an easy task and very convenient for the industry. Engineer grade films by 3m could be used for sign backgrounds and lettered on top with non reflective material for contrast. Or letters could be cut from the material itself so that the letters or numbers were reflective on a non reflective background. The former is most popular, but either way works. For over two decades, 3m’s engineer grade films, and later their high intensity sheeting, dominated the industry. The inventions went through many improvements, and other similar reflective films were also created using the same glass bead technology. In any event, across the country, and around the world, signs began to light up at night as this new and innovative film was adopted.
The Introduction of Micro Prismatic Sign Sheeting
3m was not the only inventor or company pursuing patents in the field of retro reflectivity. All over the world, inventors were experimenting with retro reflective devices using glass beads, as well as prisms made of glass or plastic. In fact, 3 months prior to 3m receiving their patent for engineer grade tape, in late 1941, an inventor named Richard Luce of South Port Connecticut, filed for a patent on a retro reflective device that did not use glass beads. Instead, he used molded plastic reflectors that emulated what a glass bead could do, only with angled prisms. Think of your cars rear tail light reflectors, or the reflector on your bike and you’ll have an idea of what Mr. Luce was creating. In any event, this was just the beginning of his experimentation into man made prisms and reflectors. Luce’s patent was granted in 1947 and he continued to innovate and invent new and better ways to reflect light. He later formed a company called Luce Reflexite in the state of Connecticut.
In 1963, brothers Hugh and Bill Rowland, who were also experimenting with prisms and retro reflective devices, bought the rights to develop a new retro-reflective technology from Luce Reflexite. You see, the Rowland brothers were working on something very innovative that would also change the world of night time safety, just as much as 3m’s reflective tape had.
Note – Bill and Hugh Rowland are two Yale Educated engineers and also brothers. Reflexite was the 19th company they had formed. After turning down an offer from 3m to buy the small company, the Rowland brothers decided to sell it over time to the employees using an ESOP. Orafol merged with Reflexite in 2011. A transaction that netted the employee stock holders 40 million dollars.
In any event, after securing all the rights , the Reflexite company was formed. They quickly created and patented the worlds first micro-prismatic sheeting or tape, a product that is as much as 20 times brighter than engineer grade films. This meant that signs that were formerly visible at say 300 feet away, could now be seen from over 3000 feet away. So as traffic moved faster, this was a huge step forward in night time safety on the road.
Reflexite’s first patent was labeled “Retro Reflective Material“, and was filed for in September of 1970, and was granted in 1972. This new invention would revolutionize the highway sign industry as well as vehicle conspicuity. Their new product was not only much brighter, it was also incredibly tough and rugged. This made it perfect for both sign applications which were static, and also vehicle conspicuity applications which were much more dynamic. In other words, Reflexite’s new retro reflective film was bright and tough, unlike anything the industry had ever seen.
Reflexite patented many more retro reflective films, with improvement in reflectivity, vividness, daytime visibility, and adhesion. Because 3m still had the sign sheeting market locked up tight, Reflexite focused on vehicle conspicuity and quickly became the number one manufacturer of conspicuity tapes in the world. Their product was bright, thin, CAD cuttable, and did not delaminate due to it’s single layer design.
3m, seeing what Reflexite had invented, waited until the patent expired, and introduced their Diamond Grade reflective sign sheeting. They applied for a patent for their DG sheeting in 1993, and received it in 1996. Because Reflexite had focused on vehicle conspicuity, and because of 3m’s marketing power, they were able to get the sign industry to switch over to their new prismatic films fairly easily. So although Reflexite sheeting never replaced the sheeting used on signs throughout the world, their invention made it possible.
Of note is the fact that after decades in the retro reflective sheeting industry, around 2010, Reflexite created a line of retro reflective films made just for signs. This was just prior to their merger with Orafol. The product was called High Intensity Prismatic or Oralite 5900. It is a vivid air back prismatic that exceeds all ASTM D4956 Specifications for Type 4 sign sheeting. They followed this product up with their 5930 and 5935 High Intensity Prismatic work zone reflective films, also Type 4 rated tapes. About a year later, Orafol in Europe began offering Type 9 Wide Observation Sheeting, and Type 11 Brilliant Grade Sheeting. Those two products, along with the 5900 series, are now marketed in the United States.
The timing for the addition of sign sheeting to Orafol’s extensive line of reflective films is appropriate, given that sign regulations have been changing and brighter films are now being mandated all over the country. As an example, the MUTCD eliminated engineer grade type 1 as an option for street signs and for all practical purposes, increased reflectivity requirements to a Type 4 Prismatic sheeting or better. Technically a Type 2 or Type 3 film can be used for certain applications, however, it is not likely that very many municipalities or road agencies will use older technology glass bead sheeting such as type 2 or 3 for new signs.
As it stands right now, 3m is the leader in sign sheeting with their Diamond Grade films. However, they are not without competition. Avery, Nikkalite, and of course Oralite are also in the race and are actively competing for their part of a nearly 3.5 billion dollar market for sign sheeting alone. The key will be in the development and marketing of new Type 9 and Type 11 retro reflective films.
