Method of Manufacturing Tooling with Retro Reflective Truncated Cube Corners
Publication Date: 2015-Nov-23
The IP.com Prior Art Database
John D. Peck: INVENTOR [+4]
Disclosed is a metallized retro reflective prismatic sheeting with truncated cube corner having higher Cap Y and enhanced brightness
Retro-Reflective, Truncated Cube Corners
Inventors(s): John D. Peck; Feng Wu; Steven R. Champman; Ethelbert Galicia
Disclosed is a metallized retro-reflective prismatic sheeting with truncated cube corner having higher Cap-Y and enhanced brightness.
PROBLEM AND OPPORTUNITY
It has been found that many of the retro-reflective prismatic sheetings such as metallized retro-reflective sheeting and air celled retro-reflective sheeting suffer from the problem of low daytime brightness and/or reduced retro-reflectivity.
Metallized retro-reflective prismatic sheeting often has lower daytime brightness compared to any air celled prismatic sheeting of similar structure and cube corner geometry. The daytime brightness of an object is sometimes described in terms of the second of the tri-stimulus coordinates (X, Y, Z) for the object, and thus is referred to as "Cap-Y." The Cap-Y scale ranges from 0 for a perfectly black object to 100 for a perfectly white object. When measured on a typical colorimeter, such as a HunterLab ColorFlex® Colorimeter, metallized prismatic sheeting often has a lower Cap-Y value than a similar air celled prismatic sheet. For example, Avery Dennison’s T-6500 White, an air celled prismatic sheeting, typically has a Cap-Y value greater than 40. In contrast, Avery Dennison’s 4510 typically have a Cap-Y value of 13-15. 4510 is metallized prismatic sheeting with the same cube corner geometry and similar structure to T-6500. Many metallized retro-reflective prismatic sheetings have a thin coating on the backside of the cube corners. The thin coating is typically comprised of aluminum, silver, gold, or other reflecting material and is applied via vacuum deposition or other method. The reflective coating allows incident light to specularly reflect off the faces of the cube corner, thus achieving retro-reflection. However, this coating also contributes to lower Cap-Y values compared to air celled products.
Air celled retro-reflective prismatic sheeting does not have a metallized reflective coating on the backside of the cube corners. Instead, a backing film is sealed in a continuous pattern. The resulting air cells allow incident light to retro-reflect via total internal reflection. Perhaps, the refractive index of the polymer used in the cube corner is important and is often chosen such that it creates a desirable critical angle between the polymer and air. Typical polymers used are acrylic, polycarbonate, vinyl, and epoxy resins. Since this type of structure does not have a metallized reflective coating, some light that is not retroreflected is able to transmit through the cube corner to the backing film. The backing film is typically white, and contributes to higher Cap-Y values. The sealing process also destroys or deforms cube corners at o...