Standards Development

Scope

This part of IEC TS 62607 establishes a standardized method to determine the key control characteristic: light conversion efficiency of quantum dot enabled light conversion films in the field of nano -photoelectric display, this standard can apply to other relevant optical conversion devices.

Details of the criteria procedures is provided in this document

Purpose

Quantum dots (QDs) are known for having broad absorption spectra and narrow emission spectra. Using the same excitation source, commonly blue light-emitting diode, to excite quantum dots of different particle sizes.
QDs can emit spectra with different peak wavelengths which are larger than the excitation wavelength. Based on the above unique characteristics, Q-LCFs having quantum dots inside the films are used in display products, greatly improving the colour gamut. Currently Q-LCFs are widely adopted by TV makers to add new feature to liquid crystal display.
Though having such advantageous feature, quantum dots are sensible to water, oxygen, light, high
temperature and so on. During the manufacturing process of Q-LCFs, various chemicals are used to form solid matrix in which quantum dots are dispersed. After the quantum dots being encapsulated in the films, the water and oxygen still can pass through polymer matrix and reach to quantum dots at a certain degree, depending on the barrier property of matrix and encapsulation layer. During manufacturing and after manufacturing, adverse effects, such as lowering quantum efficiency and stability of quantum dots, will occur.
It is critical to measure quantum efficiency of quantum dots in Q-LCFs, however, measurement of this
characteristic by integrating sphere is relatively complicated and of low test efficiency, the integrating sphere test has limitations, such as the sample size must be smaller than the size of the integrating sphere, and the luminance range of backlight is narrow. The light conversion efficiency (LCE) parameter is more meaningful than the quantum efficiency (QE) parameter in practical industrial applications , as the LED backlight usually has higher luminance. For measuring LCE, we use a luminance meter as the test tool which only measures the number of photons within 2π steradian directly in front of the backlight after excitation of the sample, which is significantly less than the number of photons collected by the integrating sphere. So the light conversion efficiency (LCE) by this standard is directly related to the luminance actually detected in the display industry, while the quantum efficiency does not. Therefore, light conversion efficiency, a more straightforward characteristic, is measured instead. The brighter of the Q-LCFs indicates higher quantum efficiency of the quantum dots inside the film. These characteristics will enable supplier and purchaser of Q-LCFs to fast determine whether the quantum dots are stable and of high quantum efficiency in the matrix, or whether the quantum dots and matrix are matched, or whether the Q-LCFs satisfy the luminance and lifetime requirements, by using common equipment to test.
For predictable and reproducible results to be used in diversified situations, it is essential for characteristics to be described and assessed in a standardized manner and to standardize the methods for quality control of the manufacturing processes. In the future, this standard may also apply to other quantum dot conversion members such as quantum dot light guiding plate, quantum dot diffusing plate.