Note: This is the third article of a four-part series covering electrical and electronic (E/E) device (1) trends, (2) material advances, (3) process technologies and (4) applications.

Stated simply, 20 percent of global electricity is consumed for lighting. The advent of light emitting diodes (LED) — only the fourth lighting technology in the history of humankind — is transforming the lighting industry. Plastics are playing a key role in lighting alternatives as global requirements for energy efficient alternatives to incandescent light bulbs continue to tighten.

Although incandescent is today’s key light source on a unit basis, it has the lowest energy efficiency. Compact fluorescent bulbs (40-70 lumen/watt) use about one-third as much electricity as incandescent (10-19 lumen/watt). LED bulbs (at 60-120 lumen/watt) use about one-tenth as much, and over their 50,000- to 100,000-hour lifetime are cheaper than compact fluorescents.

A heavy focus on climate change issues is now driving lighting regulation. Governments around the world have passed measures to phase out or prohibit the sale of incandescent light bulbs for general lighting and to encourage the use of more energy-efficient lighting alternatives. Phase-out regulations effectively ban the manufacture, importation or sale of current incandescent light bulbs for general lighting. The regulations would allow sale of future versions of incandescent bulbs if they are sufficiently energy efficient.

Brazil and Venezuela started the phase-out in 2005, and the European Union, Switzerland and Australia started to phase them out in 2009. Likewise, other nations are implementing new energy standards or have scheduled phase-outs: Argentina, Russia and Canada in 2012.

The United States, though not phasing out incandescent light bulbs, has set minimum efficiency standards for lighting to be phased in between 2012 and 2014 which effectively precludes most legacy incandescent designs.

McKinsey & Company
Global incandescent light bulb phaseout.

Compact fluorescent lights (CFLs) remain the most affordable option for efficient home lighting. But LED quality is rising, and the price is rapidly dropping. According to the U.S. Department of Energy, the prices of LED original equipment manufactured (OEM) lamps and LED packages have already or will drop by around 30 percent yearly from 2010 to 2015, and by 10 percent to 15 percent yearly from 2015 to 2020, or roughly one-fifth of their 2010 price by 2015, and a tenth of the 2010 price by 2020.

As prices come down, LED will dominate the lighting market during the next decade. LED’s market share is expected to accelerate over the next decade, with revenue growth of 30 percent yearly. Global revenues from the LED lighting market will amount to almost 65 billion euro by 2020 or close to 60 percent of the overall lighting market.

Beyond legislation, the main drivers for LEDs in the consumer market are less energy consumption, longer life and increased design freedom. Once limited to low-power, low-lumen applications like down light replacements, emerging high-brightness LEDs are now challenging conventional sources in more demanding applications like street lights, industry lighting, office lighting and even illumination of sports venues.

Organic LEDs (OLEDs) are also in development but are currently limited to display panels and backlights. It could be some time before OLEDs can reach the necessary brightness levels to be an efficient, long-life general-lighting option.

Plastics Institute of America
Light bulb cost comparison.

While LED products are currently available to consumers, the lighting market has a strong need for LED light bulbs that have the same appearance and light output as the bulbs they are replacing. PolyBrite International's award-winning, innovative incandescent-like light bulb can be used in any lighting fixture that accepts standard Edison screw-based bulbs. Their Borealis A19-40 light bulb uses an LED light source with the glass replaced with Bayer MaterialScience's Makrolon 6717 polycarbonate.

Polycarbonate was chosen for the following advantages:

  • Clarity
  • Durability
  • High heat resistance
  • UL (Underwriter's Laboratories) 94 V-0 rating at 2 millimeters thickness. By comparison, most traditional flame-retardant polycarbonates meet this key flammability rating at a thicker 3 mm.
  • Ability to be matched into a translucent white/diffused color by not blocking as much light as other materials. The higher light transmittance also allows the PolyBrite technology to use fewer LEDs. With polycarbonate for the covers, the bulbs are impact resistant and virtually unbreakable.

PolyBrite International
Borealis A19-40 LED light bulb.

Designed for indoor use in residential/commercial applications, the light bulb uses a patented thermal dissipation scheme that allows elimination of the bulky heat sink to create a bulb that looks and performs like its incandescent predecessor. The Borealis A19-40 LED lamp consumes 90 percent less energy than traditional incandescent lighting and provides at least 50,000 hours of operation. This is equivalent to 23 years of use — compared with three years of useful life for CFLs and nearly twice the life span of equivalent competing bulbs.

Continuing, advanced LED light sources are fueling rapid global demand for innovative new materials that perform under very harsh conditions, especially high temperatures and power densities. Silicone-based materials have a long history of excellent performance in demanding applications, such as protective materials for semiconductor devices. Their high optical clarity and stable properties upon exposure to heat and humidity make silicones an excellent choice for use in new demanding applications, such as protective encapsulants and lenses for high-brightness LEDs (HBLEDs).

Key attributes for silicones in optical applications include the following:

  • High optical transmittance in the ultraviolet visible region
  • Can be synthesized to cover a wide range of refractive indices from 1.38-1.58
  • Excellent photothermal stability
  • A variety of cure chemistries for easy processing
  • High purity
  • A wide range of cured moduli from gels to hard resins

Heat is the enemy of LED performance, reliability and lifetime. Dow Corning was recognized for innovation and LED product technology with two prestigious awards from LIGHTFAIR International. Conventional LED materials — epoxies, polycarbonates and acrylics — can yellow and physically degrade after prolonged exposure to temperatures of 150 degrees C and high lumen density. But Dow Corning MS-1002and MS-1003 Moldable Silicones retain superb clarity and mechanical performance over the course of a lamp or luminaire's lifetime.

This quality is becoming increasingly attractive as LED sources are increasingly expected to deliver more intense white light from comparatively smaller package sizes, and as customers seek smaller designs with higher luminous flux, which will also drive up temperatures at the device level.

Dow Corning
Advanced silicones in high-temperature LED environments.

Dow Corning announced earlier this year it is introducing an innovative new thermal management silicone technology for LED lamps and luminaires as part of their growing family of LED lighting solutions.

Dow Corning
Thermal management silicone technology for LED lamps.

Finally, DSM's new thermally conductive thermoplastic polyester Arnite PET XL T, based on proprietary filler, provides auto electronics designers with an innovative solution in overcoming heat management issues in components such as fog lamp housings, as well as lens holders and adaptive forward lighting (AFL) frames, while minimizing addition to vehicle weight.

It is also suitable for numerous other types of automotive electronic components. In addition, as future LED lighting systems get more efficient and consume less power, this material will offer weight- and cost-saving potential for these electronics-driven systems with its unique combination of heat management, mechanics and high-dimensional stability.

DSM Automotive
Automotive fog lamp housing.

Arnite PET XL T combines high heat resistance with low outgassing, offering a new alternative to metals and shows performance approaching those of more expensive polyphenylene sulfide (PPS) and polyetherimide (PEI) material counterparts. Also, it does not suffer from moisture absorption issues that commonly arise with polyphthalamide (PPA). The material has an inplane thermal conductivity of 1.65 W/mK (Watts per meter Kelvin) and also features a low coefficient of linear thermal expansion (CLT).

DSM Automotive
Thermal load infrared scan in Arnite PET XL-T (left) vs. PPA GF30 (right) at similar conditions, Showing a better thermal distribution and reduced thermal peak level by 25 C.