Full Spectrum White Light Emitting Devices

Abstract

A full spectrum white light emitting device may include a broadband solid-state excitation source for generating broadband excitation light with a dominant wavelength from about 420 nm to about 480 nm and a full width at half maximum intensity greater than about 25 nm; and a narrowband red photoluminescence material with an emission peak wavelength from about 620 nm to about 640 nm and a full width at half maximum emission intensity of less than about 30 nm; where the device has an efficacy of at least 130 lm / W and generates white light with a CRI Ra≥90, and where over a wavelength range from about 430 nm to about 520 nm, a maximum percentage intensity deviation of the white light from the intensity of light of a black-body curve or CIE Standard Illuminant D of the same Correlated Color Temperature is less than about 50%.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is (1) a continuation-in-part of U.S. patent application Ser. No. 16 / 954,925, filed Jun. 17, 2020, which is a national phase application of PCT / US2019 / 38903 (also identified as PCT / IB2019 / 001003), filed Jun. 25, 2019, which in turn claims priority to U.S. patent application Ser. No. 16 / 212,687, filed Dec. 7, 2018, which in turn claims priority to U.S. patent application Ser. No. 16 / 207,039, filed Nov. 30, 2018, which in turn claims priority to U.S. provisional patent application Ser. No. 62 / 689,538, filed Jun. 25, 2018; and (2) a continuation-in-part of U.S. patent application Ser. No. 16 / 903,251, filed Jun. 16, 2020, which is a continuation of U.S. patent application Ser. No. 16 / 517,524, filed Jul. 19, 2019, and which claims priority to U.S. provisional patent application Ser. No. 62 / 872,277, filed Jul. 9, 2019; additionally, this application claims priority to U.S. provisional patent application Ser. 62 / 931,180, filed N...

AI Technical Summary

Benefits of technology

[0016]In particular, although not exclusively, at least some embodiments of the invention are directed to white light emitting devices whose light intensity at wavelengths corresponding to the red region of the spectrum have been optimized to improve efficacy. In such embodiments, white light emitting devices can comprise a narrowband red photoluminescence material, for example a phosphor, with an emission peak having a full width at half maximum (FWHM) emission intensity of the main peak emission that is less than about 30 nm. The emission peak wavelength is selected such as to reduce light intensity (photon count) at wavelengths corresponding the red region (range) of the wavelength spectrum for wavelengths longer than about 650 nm, at which the photopic response of the eye (i.e. photopic luminosity function) is generally low (about 0.1). The emission peak wavelength can be in a range from about 620 nm to about 640 nm. Due to the sharp drop-off in photoluminescence intensity of a narrowband red photoluminescence material compared with a broadband red photoluminescence (FWHM>75 nm) this reduces the light intensity in the red wavelength region of the spectrum for wavelengths longer than about 650 nm thereby improving efficacy while still closely resembling the natural light spectrum over the region of the spectrum from about 430 nm to about 650 nm, which can be detected by the eye.

Problems solved by technology

However, for white LEDs whose spectrum is composed of peaks the General CRI Ra is proving to be inadequate as it is an average measure of color rendition over a limited range of colors and gives no information of the lighting source's performance for particular colors or highly saturated colors.

Since Rf is measured over a greater number of color samples, it will be more difficult to achieve high scores compared with the General CRI Ra.

Moreover, due to the different testing procedures, General CRI Ra and Fidelity Index Rf values are not comparable against each other.

Since Fidelity and Gamut indices are based on averages, it is not possible to tell which colors are saturated or dull.

There is growing concern that artificial light disrupts the normal regulation of human physiology and psychology, such as hormone synthesis, sleep-wake cycle, and level of alertness.

It is believed that exposure to blue light late in the evening and at night can be detrimental to health.

A further potential concern with LED lighting is the possibility of photoretinitis—photochemical damage to the retina—which can result from over exposure to violet to blue light.

The risk of BLH is sometimes associated with LEDs, even though LEDs that emit white light do not contain significantly more blue than other types of source at the same color temperature.

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