04. Sep 2017

Seoul Semiconductor and Toshiba surprise the lighting world with a new development that looks like it could mark the beginning of a revolution.

Text: Joachim Ritter,
Photos: Seoul Semiconduc,

For some it was purely a question of time, for others a seemingly unattainable goal: an artificial light source that is as perfect as daylight – or at least almost as perfect. Seoul Semiconductor are currently practically overwhelmed with queries and “applause”. In June, they introduced the SunLike TRI-R LED onto the market, a product that has even taken critics of LEDs by surprise.

The new SunLike LEDs emit light with virtually the same spectral composition as sunlight. It remains a copy, but according to state-of-the-art facts and findings it is so convincing that it is even leaving the incandescent lamp in the shade, the artificial light source that in the past was always deemed second only to daylight. The light spectrum, which is closer to that of the sun than even deemed possible, is achieved through the combination of LED chip technology from Seoul Semiconductor and TRI-R phosphor technology from Toshiba Materials. The result: a Purple LED with special qualities.

Fig. A shows how the SunLike spectrum is created from a purple LED source.

White light used in everyday lighting is created by mixing red, green and blue light. In today’s LED lighting applications this is achieved using only blue LEDs, with the red and green light created by passing the blue light through phosphors made from inorganic compounds. This results in the blue light having a higher intensity than the red and green light, so the white light that is produced has a more prominent blue region in the spectrum.

Fig. B shows how the existing LED lighting spectrum is created from a blue LED source.

A great deal of research has suggested that this blue light heavy spectrum is not friendly to human biology. Scientists indicate that exposure to blue light at night can negatively affect the human biological clock and therefore result in poor-quality sleep and other related health issues. Furthermore, the prominence of blue light within indoor LED lighting applications affects the way that objects appear to the human eye. Blue light tends to diffuse heavily within a surface so the reflected light wavelengths which enable humans to see are different than if the surface was viewed using sunlight.

The new technology, SunLike TRI-R, fundamentally transforms LED lighting technology by removing the blue LED light source and replacing it with a purple light LED chip. This is because the only way to ensure that an LED lighting application has a continuous spectrum distribution is to use a light source that is not an element of white light. New phosphor technology has been developed to ensure that none of the red, green and blue lights have any wavelength deficiencies, therefore enabling a spectrum that matches that of sunlight.

This fundamental redesign of LED technology required particular attention to be paid to developing new phosphor technology. Phosphors are ceramics-like inorganic compounds that come from rare earth elements, such as phosphate, silicate and oxonitrido-aluminosilicate. Depending on the makeup of the phosphor, purple light can be a variety of coloured lights from blue to red. To create the optimal solution for the white LED light, every phosphor used went through significant engineering development.

Due to all light elements being emitted via a phosphor, there was some potential for energy loss. To deal with this issue, a new phosphor paste coating process was developed using a mixture of organic resin to minimize the energy loss.

Now, thanks to many years of R&D ito recreating the sun’s spectrum, Seoul Semiconductor is bringing the closest light to the sun to the market. An ordinary LED spectrum is very different to sunlight, whereas SunLike TRI-R’s spectrum is almost the same. Objects lit by SunLike TRI-R appear as they would in sunlight. After humans have lived under the sun for thousands of years, human organs and biorhythms have evolved to respond most appropriately to natural sunlight. As the SunLike LED closely matches the spectrum of natural sunlight, it maximizes the advantage of natural light and minimizes the shortcomings of artificial light source.

Because the amount of blue light that our eyes can accept is limited, blue light above the limit entering the eye is scattered. When this scattering phenomenon occurs, the light is diffused, and as a result, the texture and color of objects are distorted. Also, excess blue light can over-stimulate these retinal cells in the eye, and may cause eyestrain and loss of concentration. However, since SunLike Series LEDs implement the spectrum closest to the sunlight, they more accurately represent the color and texture of the object in natural light without the negative effects of excessive blue light on the eye or human biorhythms.

SunLike will primarily be applied in commercial facilities that need to distinguish or show the exact color of the product as seen under sunlight, such as department stores and marts, in the field of horticulture, in exhibition facilities such as museums and exhibition halls, but also in health and beauty environments. In fact, everywhere where light can contribute to a better and healthier life for human beings.

Bottom line: Respect for this development, which is likely to cause quite a stir on the market. There will always be some who will not regard the biological effectiveness of specific spectral elements as being something new, but you cannot help but admit: this development is a surprising coup, a response to existing knowledge using new technology. After the invention of the blue LED in the nineties, which also won Shuji Nakamura a Nobel prize, it is once again an Asian company and not, as many may perhaps have wished, a European manufacturer who came up with this radical development. But as history has shown, learning, copying, and better marketing and promotion has not always only been an Asian art.


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