Retroreflective appliques have the ability to return a substantial portion of incident light back towards the light source. This unique ability has promoted widespread use of retroreflective appliques on clothing. Persons who work or exercise near motor vehicle traffic need to be conspicuously visible so that they do not get struck by passing motor vehicles. When placed on clothing, the retroreflective appliques highlight a person's presence by retroreflecting light from motor vehicle headlamps.
A retroreflective applique typically comprises an optical lens element layer, a polymeric binder layer, and a reflective layer. The optical lens elements commonly are microspheres that are partially embedded in the polymeric binder layer. The reflective layer typically comprises aluminum, silver, or a dielectric mirror that usually is disposed on the embedded portions of the microspheres. Light striking the front surface of the retroreflective applique passes through the microspheres and is reflected by the reflective layer to re-enter the microspheres where the light's direction is then altered to travel back towards the light source.
Retroreflective appliques have been made by partially embedding a microsphere layer in a thermoplastic carrier web, applying a reflective material over the microspheres' protruding portions, and then forming a binder layer over the coated microspheres. Often a pressure-sensitive adhesive is applied on the binder layer's back surface, and a release liner is placed over the adhesive until the applique is secured to a substrate. The completed applique (also referred to as a transfer sheet) is supplied to a garment assembler in this form, and the garment assembler secures the applique to an article of clothing by removing the release liner and adhering the applique to an outer surface of the article of clothing. The carrier is then separated from the applique to expose the microspheres so that the applique can retroreflect light. Although known retroreflective appliques demonstrate very good retroreflective performance and are very effective in highlighting a wearer's presence when light strikes the clothing at nighttime, the known appliques possess some drawbacks.
A first drawback is that the applique requires use of a carrier web that becomes discarded as waste by the garment assembler. The carrier web is not separated from the applique before the manufacturer supplies the applique to the garment assembler because the applique is not yet secured to a substrate. If the applique was separated from the carrier beforehand, the applique's binder layer and the reflective layer can become irreversibly stretched when the carrier is pulled away from the applique. This irreversible stretching can harm the applique's retroreflective performance.
A second drawback is that when the applique is secured to the substrate with heat, residual carrier web material can remain on the exposed surface of the microspheres, causing a reduction in retroreflective performance. Also, the thermoplastic carrier limits the quantity of heat that can be applied to the applique because, if too much heat is applied to the carrier, the carrier can stick to the microspheres and can become very difficult to remove. Limiting the heat supplied to the applique can cause a poor bond between the applique and the substrate.
Another drawback is that known transfer sheets are supplied to the garment assembler with a release liner that, like the carrier web, also becomes discarded as waste. Of course, it is not beneficial from an economic or environmental standpoint to discard the release liner or the carrier web as waste.