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New International Standards for Methods of Evaluating the Optical Properties of Ceramic Phosphors for White LEDs Issued Aiming at further popularization of quality, highly-reliable, Japanese-made phosphors

Japanese manufacturers can boast their outstanding techniques for manufacturing ceramic phosphors for white light emitting diodes (LEDs) which lead the rest of the world. Nevertheless, no international standards for methods of evaluating the optical properties of such phosphors have been stipulated, and this causes challenges for Japan in international competition in related fields. Against this background, Japan has proposed the establishment of new international standards for methods of evaluating the optical properties of ceramic phosphors for white LEDs based on existing Japanese Industrial Standards (JIS), to the International Organization for Standardization (ISO). In response, the ISO finally issued new standards based on the proposal. Japan expects that the new international standards will encourage Japanese manufacturers to further popularize quality, highly-reliable ceramic phosphors and to bolster their international competitiveness, as well as achieving an energy conservation effect brought about by making white LEDs highly efficient.

1. Background

White LEDs bring about dramatic reduction of energy consumed by lighting in households, offices and other locations, and it is expected that this reduction will contribute to achieving a clean and economic energy society, this expectation has been propelling a dramatic popularization of white LEDs both inside and outside Japan, as seen the designation of bulb-type LED lamps as a subject to the Top Runner Program under the Energy Saving Act in 2013
Improvement of the energy-conversion efficiency in white LEDs lies in ceramic phosphors as a key device that highly-efficiently converts the light emitted from chips into white light, in addition to the light-emitting efficiency of LED chips. Despite this situation, no international standards for methods of evaluating the optical properties of ceramic phosphors have been stipulated, and this causes bottlenecks for Japanese manufacturers in developing business involving their quality, highly-reliable ceramic phosphors overseas.


Figure: Pictures of ceramic phosphors for white LEDs
(Source: National Institute for Materials Science, etc.)

2. Outline of new ISO standards and background to the issuance

Against this backdrop, in October 2014, Japan drafted a proposal of new international standards for methods of evaluating the optical properties of ceramic phosphors for white LEDs, based on the existing domestic standard of JIS R1697 (absolute measurement of internal quantum efficiency of phosphors for white light emitting diodes using an integrating sphere), and submitted the proposal to the ISO/TC206 (fine ceramics) / WG11 (electrical and optical applications). ISO/TC206 is a technical committee engaging in Japan-led activities, the Secretariat of which has been served by Japan.

For approximately three years, the technical committee held meetings to discuss the development of new standards. In these meetings, Japanese members from the manufacturers of ceramic phosphors and measuring machines, universities, national institutes, and other entities proactively participated in these and held repeated discussions and coordination with experts from other member countries. As a result, in September 2017, the ISO officially issued new international standards based on the proposal.

Note: The term “internal quantum efficiency” refers to the ratio of the number of fluorescence photons irradiated from phosphors to free space in the number of excitation photons absorbed by the phosphors, which is one of the major optical properties representing the function of phosphors.

Key points of the newly-issued international standards (ISO 20351: Fine ceramics   Absolute measurement of internal quantum efficiency of phosphors for white light emitting diodes using an integrating sphere) are as follows:

  • The new standards stipulate methods of evaluating the optical properties of ceramic phosphors, the world’s first achievement in stipulating such in this field.
  • The standards are stipulated taking into consideration that operators will continue to utilize the existing multiple types of measuring machines broadly used among industries.
  • The standards provide a variety of instructions for measuring procedures in an explicit manner, so as to allow operators to further curb variability in measured values of optical properties than those by ordinary methods, thereby improving the comparative precision between measuring organizations or machines.

3. Future actions

This issuance of the new standards is expected to contribute to encouraging Japanese manufacturers to research and develop quality, highly-reliable domestic ceramic phosphors, thereby boosting Japan’s international competitiveness in this field.

In addition to this issuance of new ISO standards, Japan will continue efforts for establishing other new standards for methods of evaluating the optical properties of ceramic phosphors for white LEDs, and will strive to engage in such efforts for international standardization leading the rest of the world. Through these efforts, Japan will promote initiative for making white LEDs highly efficient and aim to further contribute to achieving an energy-saving society.

Note:This successful standardization of ceramic phosphors is partly due to the achievements under the Strategic Development of International Standards Project (international standardization for methods of evaluating the optical properties of ceramic phosphors for white LEDs) and other projects, which METI has commissioned to a private entity.

Release date

October 10, 2017

Division in Charge

International Standardization Division, Industrial Science and Technology Policy and Environment Bureau

Related website

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