There is a trade-off between color rendering and luminous efficacy.
For example, the reference light source equivalent to sunlight (Figure 1) can yield higher color rendering with its flattened spectrum. Which means, however, it requires many types of phosphors to do so. The more the phosphor types are used, the less the light conversion efficiency becomes, thus resulting in lower luminous efficacy.

To improve this trade-off, we have developed the following technologies:

• By adding the algorithms of the color-matching functions (Figure 2) that represent human color perception to our simulator, we optimized excitation lights and the compositions of phosphors. This allowed us to improve the trade-off between color rendering and luminous efficacy.
        Ultra-high color rendering that brings in excellent CRI scores including Ri and comes in wide-range color temperatures
        CCT of 5000 K: Ra ≥ 95, Ri ≥ 90
         CCT of other values: Ra = 90 (typ.), Ri = 90 (typ.)
  
• By using blue LED chips with long wavelengths for excitation lights, we finally raised the light conversion efficiency in the phosphors used. We also utilized the transmitted lights to yield higher luminous efficacy.
        141 lm/W　(SEP2AQ1L92)
  

Color rendering describes how a light source can render colors appear when it illuminates an object.
A color rendering index (CRI) is the metric to measure this color rendering performance.
A CRI score represents the color appearance when an object is lit by sunlight (i.e., reference light source) on a scale of up to 100. And there are two types of CRI: Ra, average color rendering index, determined by the average value of neutral-color-based test color samples (R1 to R8); Ri, special color rendering index, determined by each value of test color samples including primary colors (R9 to R15).

In general, the CRI score is expressed by a Ra value; however, even with high Ra values, most light sources have less color reproducibility due to their low Ri values (the primary-color-based metric). For this reason, we sought the way to bring out higher Ri values in the SEP1A/SEP2A series.
Our efforts on the SEP1A/SEP2A series then turned out to be extremely great—Ra of 95 (typ.) and Ri of 90 (typ.)—high color rendering.

Especially when it comes to our LED devices with 5000 K (the SEP1A series and SEP2AQ1L92), they satisfied the standards recommended by the Japanese Society of Printing Science and Technology and got high enough levels as well as color rendering AAA fluorescent lamps (see the table below), which are commonly used for color evaluation.
So, our LED devices will best suit a light source for color inspection as they faithfully reproduces a wide range of colors, including primary colors.

In recent years, human-friendly lighting dedicated to better light qualities has become widespread from a standpoint of wellness⁽⁵⁾ and HCL⁽⁶⁾.

[Lighting Application Examples]

• Lighting that changes its color and brightness along with the time-course changes of natural sunlight
• Lighting equipment that can adjust tones and tints unlimitedly
• Lighting that sets a healthy circadian rhythm by exploiting the nature of biological body-to-light synchronization

⁽⁵⁾ Wellness: A lifestyle that people seek to live better; the term interpreted in a broader sense than the term “health” defined by WHO.
⁽⁶⁾HCL (Human Centric Lighting): A type of lighting that supports people’s health with its safety, comfort, and convenience.
(Source page available only in Japanese: Japan Lighting Manufacturers Association, https://www.jlma.or.jp/led-navi/contents/cont43_cslandhcl.htm）