[FPDI] Next-generation Lighting Featured at Display Exhibition

Lighting equipment was featured at the FPD International for the first time.

At a special exhibition booth called "Green Devices to Change Homes & Towns," Panasonic Electric Works Co Ltd (former Matsushita Electric Works Co Ltd), Toyoda Gosei Co Ltd, Asahi Rubber Inc, Osram Ltd, Coolermaster and the Japan LED Association (JLEDS) had presentations relating to LED lighting (Fig 1). And Lumiotec Inc exhibited organic EL lighting equipment.

The FPD International is a display-related exhibition. Still, the booths of those companies were crowded with visitors because people in the display industry are highly interested in OLED panels, LED backlights and other novel light sources.

The LED lighting equipment exhibited by Panasonic is capable of changing the color temperature from 2,500K (incandescent color) to 7,000K (fluorescent lamp color) (Fig 2). Users can select a color temperature from various choices including the incandescent color, the color of office lighting and the color of the sky on a bright day, depending on the occasion such as dining and work.

The company did not explain the technical information in detail because it was only exhibited for reference. But the equipment has white LEDs with different color temperatures and generates a desired color temperature by separately controlling the LEDs to mix the emission colors, the company said. The LED module used in the equipment was designed in consideration of heat dissipation and ensures a life of 40,000 hours, the company said.

Toyoda Gosei exhibited a panel that illustrates the production flow of its LED lighting equipment. By using actual workpieces, it presented the production steps such as the fabrication of LED chip, packaging of the chip, mounting of the package on a printed circuit board, and assembling the LED equipment with the board.

Asahi Rubber showed the effect of its LED caps, which can correct subtle variations in LED colors to provide a desired emission color. The effect was obtained by using the company's proprietary technology to cover blue and other color LEDs with silicone resin containing phosphors.

Recent LEDs are said to have lower variations in emission wavelength and luminance. But, when a large number of LEDs are arranged in an array for lighting applications, for example, it is often said that those variations are still problems. Therefore, Asahi Rubber prepared dozens of different kinds of caps in accordance with emission wavelength and luminance.

At the exhibition, the company demonstrated light emission by using blue LEDs with slightly different emission wavelengths, showing a comparison between two setups, one using the same caps and the other using caps separately optimized for each LED (Fig 3). The company also prepared a sheet type cap for surface-mount LED packages, which are increasingly being used (Fig 4).

Osram and Coolermaster exhibited an outdoor LED lighting module targeted for streetlamps, etc. The companies assembled outdoor lighting equipment by using eight modules (Fig 5). Each module uses 16 white LEDs manufactured by Osram. The maximum input power per module is approximately 23W, and the luminous flux is 960lm. The power consumption per module excluding the power circuit, or the power consumption of the light source unit, is 18W.

A heat dissipation unit composed of a heatsink and a heatpipe is attached to the back side of the module so that it can be cooled with ambient air.

The white LED used in the module is called "Golden Dragon," and it is attached with a lens. The input power is slightly higher than 1W. The emission efficiency is 55lm/W. The lens is optimized for use in outdoor lighting equipment. Specifically, it is designed so that the light emitted from the bottom of the LED becomes weak and the light emitted from the sides of the LED becomes strong. The lens has an elliptic irradiation surface.

JLEDS had panel and video presentations on the overview and exemplary applications of LED lighting equipment. What was especially striking was the panel presentation explaining about the life of LEDs. LEDs are said to have a long life, but their life may be shorter than that described in the specifications if they are used in harsh temperature conditions, according to the panel.

The life of an LED is often said to be 40,000 hours, but this has not been confirmed by actually using the LED for 40,000 hours under real use conditions. In reality, the life of an LED is measured by an accelerated test where it is turned on at a temperature higher than that in actual use conditions to obtain a luminance reduction rate. The life in the normal temperature is calculated based on the test result.

Lumiotec exhibited organic EL lighting equipment, highlighting the features that can only be offered by organic EL equipment such as a 2.3mm thickness and surface emission (Fig 6). The equipment has high color rendering properties and a broad spectrum with peaks in red (R), green (G) and blue (B) regions, according to Lumiotec.

The company employed a technology called "multi-photon emission (MPE)," which uses several emission layers stacked vertically. The product on display had vertically stacked three emission layers with different emission wavelengths for RGB colors.

In addition, it is technically possible to stack more layers with different emission wavelengths and cover the emission lengths that can't be covered with the original three layers, Lumiotec said.

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