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Microstructured plastic inner lenses enable even illumination and design freedom in rear tail lamps, while reducing the number of LEDs required and part complexity in lamp. The first such inner lens thermoformed from polycarbonate (PC) has debuted in the 2013 Buick Enclave.

December 20, 2012

2 Min Read
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Microstructured plastic inner lenses enable even illumination and design freedom in rear tail lamps, while reducing the number of LEDs required and part complexity in lamp. The first such inner lens thermoformed from polycarbonate (PC) has debuted in the 2013 Buick Enclave.

Developed by 3M (Minneapolis, MN) and known as Uniform Lighting Lens (ULL) technology, the precision engineered inner lens incorporates two types of microstructure with detail of less than 100 micrometers. These structures are designed to balance the optical properties of uniform illumination from all angles and luminous intensity.

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Close-up of the lighted cavity shows consistency of light as it wraps around a tight corner, enabling design flexibility of tail lamps.

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Thermoformed and micro-structured inner lens realizes uniform lighting.

Production of the lenses involves extrusion of a 1-mm-thick PC film with micro-replicated features using Makrolon 2447 from Bayer Material Science (Leverkusen, Germany), followed by forming of the lens itself in a multicavity thermoforming tool. Tool making process innovations have enabled the combination of micro-structure and macrostructure features in the finished tool. Post-process trimming is carried out in a metal die. A micro structure size of 100 micrometers on an inner lens is not possible with the injection molded part process according to 3M.

The lenses are shipped to Tier 1 Magna International (Troy, MI), which worked with 3M on the development of the lens, in optimized packaging to ensure moisture control, for integration into the lamp assembly.

The ULL lamp employing the new lens with two LEDs weighs 620g versus 1134g for the original Enclave bulb lamp whose inner lens was injection-molded. The minimal thickness achieved by thermoformed microstructured lens also has potential to reduce number of LEDs needed to execute lamp design, contributing to reduced energy consumption and weight reduction in rear lamps. Power requirement has been reduced to 3.5W versus 35W for the stop function. A further bonus is that lamp lifetime has been extended from 5000 hours to 30,000 hours.

"Our Uniform Lighting Lens technology is a solution to several challenges our customers face," said Jeff Boettcher, new business development manager, 3M Automotive. "It can be used not only to create new, modern lighting designs, but also allows for manufacturers to create signature images to generate brand differentiation."

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