High Brightness LEDs Shine On
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SignLab from CADlink


High Brightness LEDs Shine On

Light Emiting Diodes (LEDs) have distinguished themselves as a highly unique and significant lighting source that has both immediate and far reaching consequences for the sign industry.

By Louis M Brill

LEDs immediate effect upon signage has been in the areas of electronic text and graphic message centers and video displays for some indoor and mostly outdoor advertising signage.

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  • LEDs have been effective for both electronic billboards and as an illumination source for channel letters where it performs as an alternative lighting medium to neon lighting. Its features have been bandied about forever including its small size, its low voltage efficiencies, and its robustness in lasting upwards of 60,000 - 70,000 hours before they have to be replaced. It’s performance efficiency is a moving target as its overall cost is continually descending and new technological improvements are resulting in LEDs constantly getting brighter as an illumination source.

    It is that last factoid that is of particular interest to the sign community as LED lighting is a critical component of signage and as its luminosity output continues to increase, has come into its own market niche known as High Brightness LEDs (HB LEDs). There are several ways to identify HB LEDs, one is very simple and visceral, that the LEDs are so bright that viewers cannot look directly at them without irritating their eyes. The second, more technical definition is based on HB LEDs manufacturing process. HB LEDs come in two forms which have evolved from a series of semiconducting materials; AllnGaP, (pronounced alan-gap), which is composed of aluminum, indium, gallium and phosphide which create HB orange-red, orange, yellow and green lighting units. The second solid state offering is InGaN (pronounced as n-gan), which includes indium and a Gallium-Nitrade compound, and creates blue, blue-green, true-green and when combined with a yellow phosphor, white. HB LEDs can usually be found in a standard 5mm, 1 amp LED package which provide at least several hundred millicandela in light intensity.

    HB LED state of the industry
    Dr. Robert Steele, director of optoelectronics for Strategies Unlimited (Mountaiview, CA), a company that produces "Strategies in Light" the annual HB LED conference noted that in 2005 the HB LED industry had grown 8 % from last year (2004 - $3.7 billion) and is now benchmarked with an overall revenue of $4.0 billion. It was noted at the conference that HB LEDs ultimate success will be in transforming from a technology driven market to an applications-driven market. Dr. Steele observed the HB LED marketshare leading segments included mobille appliances (52%), and as was last year, a tie for second place between signage (14%) and automotive (14%) (see chart for full breakout). In another catagory application as HB LEDs continue to improve in their development of white LEDs in terms of price/performance, it will open up a retrofit market of replacing existing incandescent and flurescent lighting sources with their LED counterparts. This retrofit will not only apply to home use, but to the sign community as well, once the appropriate LED lighting sources show up.

    High Brightness LEDs, signs, displays and general illumination applications are all big consumers of HB LEDs.
    chart credit: Strategies Unlimited

    As HB LEDs continue to make their way into the sign community, it is generally considered that electronic billboards will become a killer application, both for the LED manufacturing community and for outdoor signage as more outdoor advertising companies seek out LED-based billboards as a preferred advertising medium. Steele note that other potential areas where HB LEDs will influence electronic signage are with large LCD displays where RGB LEDs are being used as a replacement back light to illuminate the screens (some which become various EDS systems). In another display application, HB LEDs are just begining to be used as a light source for rear projection televisions.

    Currently, several LED manufacturers produce HB LEDs including Lumileds, Cree, Osram Opto Semi Conductor, Nichia and COTCO. To gain a better understanding of HB LEDs evolution, Sign Industry.com interviewed Nichia and Osram Opto Semiconductor, both who discussed their HB LED product lines in regard to increased market demands for LED-based sign products.

    How it works - an inside diagram of the major components of a Luxeon high powered LED.
    chart credit: Lumileds

    Nichia corporation
    Nichia (Anan, Japan) is the world's largest provider of GaN-based LED products and acknowledged as the inventing company of both blue and white LEDs. In 1993 the company developed and commercialized the first super high brightness blue LED and since then, has become a world-wide provider of a full spectral range of LEDs in different sizes and brightness levels. Sales manager, Dan Doxsee described Nichia's overall involvement in lighting up the sign industry with high brightness LEDs. "The display and signage business was one of the first market segments for Nichia LED products and for sheer volume, display is still one of Nichia's top markets. Nichia's LED technology is defined by the company's customers' needs, thus, the company manufactures products based upon market segment requirements. Consequentially Nichia LEDs are used for both channel letter illumination and as an RGB matrix source for full color video display boards. The company offers various types of HB LEDs at different illumination ranges and colors depending on the sign application it is sourcing."

    To meet the needs of outdoor signage, Nichia HB LEDs are very robust and able to handle extremes in temperature and moisture with an estimated use between 60,000 to 70,000 hours, depending on the package type. Nichia product brands Doxsee stated include the Raiko series (5.1 lumens at an output of up to 2200 millicandelas) which are available in both white and all the major colors and used mostly for standard sized channel letters. For low profile channel letters with a more shallow depth, Nichia offers the NSSW100B series (2 lumens at about 750 millicandelas). These are surface mounted units which have a 110 degree angle of illumination giving an even lighting spread on the channel letter sign faces. For large sign products that require greater levels of high brightness there is the Rigel series (20 lumen at 8250 millicandelas).

    The 2005 High Brightness LED market saw a total revenue of $4.0 billion, of which sign displays tied for second place (with automotive) with a 14% market share.
    chart credit: Strategies Unlimited

    Billboards and signs on tall buildings where people look up to see LED video displays are also an increasing market for Nichia where they've designed their LEDs accordingly. "To meet the video display design criteria," Doxsee noted, "Nichia developed the Super Oval LED, which is made in 3mm and 5mm sizes and available in red (880 millicandelas), blue (500 millicandelas) and green (1750 millicandelas). The Super Oval offers a horizontal angle of view at 100o and at 40o in the vertical direction. The unique feature of the Super Oval is created with an flattened optical pattern that directs the light of the LED to the viewing area, (aimed towards the street), rather than upward. This allows for a much higher luminance than classic round packages. Super Ovals can be used for either video displays or message reader boards."


    RENOLIT Calendered Vinyl - Top performance for various applications

    Osram Opto semiconductor
    OSRAM Opto Semiconductors is one of the largest manufacturers of optical semiconductors in the world of illumination, visualization and sensing sectors. The company has more than thirty years of experience in the development and manufacture of light-emitting diode (LED) and optical semiconductor components. According to Brian Terao, senior product marketing manager for OSRAM Opto Semiconductors’ High-brightness light-emitting diodes (HB LEDs) products, “OSRAM is building the bridge from traditional lighting to solid-state-lighting, by offering our products to as many relevant emerging markets as we can.” OSRAM offers a broad portfolio of LED products, many of which can be applied to backlighting a cell phone or PDA, to channel letters or a stop light, to a jumbotron in a stadium or on a freeway.

    To date the OSRAM HB LED portfolio includes:

    • Power TOPLED®
      A 4-lead LED, with a robust design, emits 3 to 9 lumens at up to 70milliamps (mA).
    • Advanced Power TOPLED®
      A medium range LED offering an illumination range from 7.5 to 24 lumens at a power output of 140 mA.
    • Golden DRAGON™ LED
      OSRAM's maximum HB surface mount LED device, which is available in a full range of colors including: red, amber, blue and white. These units produce a range from 20 to 70 lumens at power outputs up to 400 mA.
    • MULTILED®
      A red-green-blue (RGB) device usable for all full color LED video screen applications, with 3-chips to offer more brightness and a long life time up to 50,000 hours, and an optical efficiency of 26 lumens per watt (lm/W).
    • OSTAR LED
      OSRAM’s newest LED is a tiny 3x1 centimeter (cm), 6-chip design white LED with an operating current of only 700 milliamps (mA), emits 420 lumens.

    Terao noted that OSRAM’s LEDs are ideal for the signage marketplace because they are scalable and are available in many formats. However it is best to select a LED depending on the brightness, color and life requirements of the intended sign application. Most of OSRAM Opto Semiconductors’ LEDs can be applied to channel letter illumination (both front and backlit), yet are usable for both deep channel letter formats and narrow channel letters where one-half watt (at about 15 lumens) lighting brightness levels are needed. OSRAM can also provide Advanced Power TOPLEDs and OSTAR LEDs for illuminating those same signs.

    “For monochromatic LED text message centers, OSRAM’s red and amber Power TOPLEDs are the best choice. However, OSRAM’s MULTILED (RGB) component is suitable for populating video or full color graphic displays screens,” said Terao. “OSRAM is also beginning to offer LED products as a replacement back lighting source for LCD display manufacturers, whose screens, among their many applications, are used in indoor digital signage” He added.

    In a nod toward the demand for HB LEDs with greater light efficiencies, Osram has developed a Thin-Film technology, which in effect, harnesses and re-channels the previously lost energy and light output of a standard LED (known as side emission losses) during its transmission process. The immediate benefit of the technology is that the light emission now radiates from one direction ­the top of the chip.

    The Thin-Film manufacturing process at the die level (where the LED core component is 'grown' to completion) begins by developing an InGaN or InGaAlP (Indium Galium Nitride) structure on a base substrate. As the die is processed, its upper surface (which is the bottom of the die) is then metallized to take on a highly reflective surface. The metallized reflector at the bottom of the active layer reflects all the downward-emitted light through the top surface. This process also prevents the absorption of light by the carrier substrate, as is the case in conventional LED volume emitters. The thin active layer increases light extraction efficiency, minimizes internal absorption, thus making Thin-Film-based dies nearly pure surface light emitters. Other benefits of OSRAM’s Thin-Film technology are its scalability, which allows for higher light intensities at lower voltage levels to a point of achieving output powers as high as 500 mW for a 1-A drive current. Furthermore it offers a wide viewing angle of 120 degrees. OSRAM first applied its proprietary Thin-Film technology to the development of its Golden DRAGON LED series. The experiment was so successful that OSRAM is incorporating the technology into the redesign and manufacture of its entire HB LED portfolio.

    HB LEDs has become a solution, waiting for its challenge. The intensity of that solution is equal parts lumens/watt and lumens/watt per dollar. At the end of the day, HB LEDs must not only shed light on its subject, but do so at an affordable cost for its intended user. For the sign industry it is an illumninating thought as more of HB LEDs come forth, just how much more of a role it is playing in determining where the future of electronic signage will go.

    Louis M. Brill is a journalist and consultant for high-tech entertainment and media communications. He can reached at (415) 664-0694 or louisbrill@sbcglobal.net

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