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US-12628476-B2 - Light emitting device and electronic apparatus using same

US12628476B2US 12628476 B2US12628476 B2US 12628476B2US-12628476-B2

Abstract

Provided is a light emitting device that is characterized by at least combining a solid-state light emitting element, a first wavelength converter, and a second wavelength converter, and emits output light. The solid-state light emitting element emits primary light. The first wavelength converter absorbs at least part of the primary light and converts this part of the primary light to first wavelength-converted light. The second wavelength converter absorbs at least part of first mixed light including first transmitted primary light, which is the primary light that has passed through the first wavelength converter, and the first wavelength-converted light, and converts the light to second wavelength-converted light. The output light includes at least transmitted first wavelength-converted light, which is a light component obtained by the first wavelength-converted light having passed through the second wavelength converter, and a light component of the second wavelength-converted light.

Inventors

  • Ryosuke Shigitani
  • Mitsuru Nitta
  • Shozo Oshio

Assignees

  • PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.

Dates

Publication Date
20260512
Application Date
20220214
Priority Date
20210224

Claims (17)

  1. 1 . A light emitting device comprising: a solid-state light emitting element; a first wavelength converter including a first phosphor; and a second wavelength converter including a second phosphor, and emitting output light, wherein the first wavelength converter is interposed between the solid-state light emitting element and the second wavelength converter, wherein the solid-state light emitting element emits primary light having a maximum intensity within a wavelength range of 440 nm or more and less than 480 nm, wherein the first wavelength converter absorbs at least part of the primary light and converts this part of the primary light to first wavelength-converted light having a fluorescence peak in a visible wavelength range of 380 nm or more and less than 780 nm, wherein the second wavelength converter absorbs at least part of first mixed light including first transmitted primary light, which is the primary light that has passed through the first wavelength converter, and the first wavelength-converted light, and converts the first mixed light to second wavelength-converted light having a fluorescence peak in a wavelength region exceeding 750 nm and having a near-infrared component in a wavelength range of 780 nm or more and less than 2500 nm, wherein the first mixed light is light of a light color with a correlated color temperature of 2500 K or more and less than 40,000 K, and wherein the output light includes at least transmitted first wavelength-converted light, which is a light component obtained by the first wavelength-converted light having passed through the second wavelength converter, and a light component of the second wavelength-converted light.
  2. 2 . The light emitting device according to claim 1 , wherein the solid-state light emitting element and the first wavelength converter are combined to form a wavelength-conversion light emitting element.
  3. 3 . The light emitting device according to claim 1 , wherein the output light is light of a light color with a correlated color temperature of 2600 K or more and less than 12000 K.
  4. 4 . The light emitting device according to claim 1 , further comprising: a control mechanism for controlling an output ratio of the light component of the second wavelength-converted light.
  5. 5 . The light emitting device according to claim 1 , which alternately outputs output light including the light component of the second wavelength-converted light and output light not including the light component of the second wavelength-converted light.
  6. 6 . The light emitting device according to claim 1 , wherein the first wavelength converter includes a red phosphor that emits light having a fluorescence peak in a red wavelength region of 600 nm or more and less than 660 nm.
  7. 7 . The light emitting device according to claim 1 , wherein the first phosphor included in the first wavelength converter is only a phosphor activated with Ce 3+ .
  8. 8 . The light emitting device according to claim 1 , wherein at least the second wavelength converter has a characteristic of allowing at least the second wavelength-converted light to pass therethrough.
  9. 9 . The light emitting device according to claim 1 , wherein the second phosphor contains Cr 3+ as a fluorescent ion.
  10. 10 . The light emitting device according to claim 1 , which is a light source for a sensing system or a lighting system for a sensing system.
  11. 11 . An electronic apparatus comprising the light emitting device according to claim 1 .
  12. 12 . The light emitting device according to claim 1 , wherein the primary light does not irradiate the second wavelength converter without passing through the first wavelength converter.
  13. 13 . The light emitting device according to claim 1 , wherein the first transmitted primary light has a special distribution derived from the primary light and a lower light intensity than the primary light.
  14. 14 . The light emitting device according to claim 1 , wherein the second wavelength converter is not directly irradiated with the primary light.
  15. 15 . The light emitting device according to claim 1 , wherein the first mixed light has a larger irradiation area than the primary light.
  16. 16 . The light emitting device according to claim 1 , wherein the second phosphor is not directly excited by the primary light.
  17. 17 . The light emitting device according to claim 1 , wherein an intensity of the second wavelength-converted light starts at a wavelength of 850 nm and decreases as the wavelength becomes longer, and wherein a fluorescence intensity at a wavelength of 1000 nm is less than 10% of the fluorescence intensity at a wavelength of 850 nm.

Description

TECHNICAL FIELD The present invention relates to a light emitting device and an electronic apparatus using the light emitting device. BACKGROUND ART Conventionally, light emitting devices have been known which are characterized by at least combining a solid-state light emitting element and a phosphor, and emit output light having a near-infrared light component. Patent Literature 1 discloses a light emitting device with a simple structure including a wavelength converter having a phosphor which takes Cr3+ and/or Ni2+ as a light emission center, and a semiconductor chip that emits excitation light. Near-infrared light is generated by subjecting blue or red light emitted by the semiconductor chip of the light emitting device to wavelength conversion by means of a wavelength converter. The light emitting device disclosed in Patent Literature 1 is mainly related to an optoelectronic element to replace conventional light sources for applications in compact and portable analyzers and spectrometers, sensor applications in industrial machinery, smartphones, endoscopes, and the like. As conventional light sources, halogen lamps, infrared lasers, infrared LEDs, and the like are known. In the example of Patent Literature 1, it is disclosed that the near-infrared light output of the light emitting device (the optoelectronic element) is less than 50 mW. Patent Literature 2 discloses a light emitting device for industrial equipment used as an alternative to halogen lamps and the like, for example. This light emitting device is characterized by combining a light emitting element that emits light with a maximum intensity in an ultraviolet to blue wavelength region of 480 nm or less with a phosphor that at least includes a phosphor that converts light to near-infrared light, and accordingly light having a near-infrared light component with a wide fluorescence spectrum half width is obtained. The example in Patent Literature 2 discloses that the near-infrared light output of the light emitting device using an LED chip that emits 600-mW ultraviolet light exceeds 10 mW. CITATION LIST Patent Literature Patent Literature 1: Japanese Patent No. 6570653Patent Literature 2: International Publication No. WO 2019/240150 SUMMARY OF INVENTION Conventional light emitting devices that are characterized by at least combining a solid-state light emitting element and a phosphor and emit both near-infrared and visible light components simultaneously have a problem in that it is difficult to achieve both high output and a large area. This is because the primary light emitted by the solid-state light emitting element is used to directly irradiate a wavelength converter that emits a near-infrared light-emitting component, making it particularly difficult to achieve an increase in the area and output of the near-infrared light component. Specifically, the primary light emitted by the solid-state light emitting element usually has directivity, and therefore, in the conventional light emitting devices described above, the primary light having directivity is used exclusively to irradiate the irradiated surface of the wavelength converter locally. Therefore, the area of the irradiated surface irradiated with the strong primary light becomes smaller, and in-plane variation is likely to occur in the intensity of the primary light with which the irradiated surface is irradiated. The portion irradiated with the strong light tends to generate heat due to Stokes loss associated with the wavelength conversion of the phosphor included in the wavelength converter. Since this heat generation induces thermal quenching of the phosphor, if the primary light has high directivity, this leads to a local decrease in the wavelength conversion efficiency of the wavelength converter, and the average wavelength conversion efficiency thereof is likely to decrease. In addition, Stokes loss increases as the wavelength difference between the wavelength at which light absorption is performed by the wavelength converter and the wavelength at which fluorescence emission is performed by the wavelength converter increases. Therefore, under the condition that the primary light is the same, a phosphor which converts primary light to near-infrared light generates more heat than a phosphor which converts primary light to visible light, and the decrease in efficiency due to thermal quenching is easily induced. In addition, primary light having high directivity enters the wavelength converter obliquely as the distance increases from the irradiation center of the irradiated surface of the wavelength converter. Therefore, if primary light having high directivity is used, the penetration depth of the primary light into the wavelength converter or the optical path length of light that passes through the wavelength converter becomes longer, resulting in a distribution angle dependence in which the color tone of the output light becomes inhomogeneous. The present invention has been devised