Light-emitting device, lighting appliance, and street light
Provided is a light-emitting device, a lighting appliance, and a street light that emit light with minimal negative effects on the behavior of sea turtles and which makes irradiated objects easily visible to humans. The light-emitting device includes a light-emitting element having an emission peak wavelength within a range from 400 nm to 490 nm; and a first phosphor having an emission peak wavelength within a range from 570 nm to 680 nm, wherein the light-emitting device, lighting appliance, and street light emit light that has a correlated color temperature of 1950 K or less, an average color rendering index Ra of 40 or greater, a full width at half maximum of an emission spectrum indicating a maximum emission intensity in an emission spectrum of the light-emitting device of 110 nm or less, and a sea turtle light attraction index T derived from Equation (1) of 0.416 or less.
1. A light-emitting device comprising:
a light-emitting element having an emission peak wavelength within a range from 400 nm to 490 nm; and
a first phosphor having an emission peak wavelength within a range from 570 nm to 680 nm, wherein
the light-emitting device emits light that has a correlated color temperature of 1950 K or less, an average color rendering index Ra of 40 or greater, a full width at half maximum of an emission spectrum indicating a maximum emission intensity in an emission spectrum of the light-emitting device of 110 nm or less, and a sea turtle light attraction index T derived from Equation (1) of 0.416 or less,
T
=
∫
360
700
S
(
λ
)
×
R
t
(
λ
)
d
λ
∫
380
730
S
(
λ
)
×
V
(
λ
)
d
λ
(
1
)
where S(λ) is a spectral radiance of light emitted by the light-emitting device, V(λ) is a spectral luminous efficiency function for human photopic vision specified by the Commission Internationale de l'Eclairage (CIE), and R t (λ) is a sea turtle light response curve.
2. A light-emitting device comprising:
a light-emitting element having an emission peak wavelength within a range from 400 nm to 490 nm; and
a first phosphor having an emission peak wavelength within a range from 570 nm to 680 nm, wherein
the first phosphor includes a first nitride phosphor having a composition represented by Formula (1A), and
the light-emitting device emits light that has a correlated color temperature of 1950 K or less, a full width at half maximum of an emission spectrum indicating a maximum emission intensity in an emission spectrum of the light-emitting device of 110 nm or less, and a sea turtle light attraction index T derived from Equation (1) of 0.416 or less,
M 1 2 Si 5 N 8 :Eu (1A)
where M 1 is an alkaline earth metal element including at least one selected from the group consisting of Ca, Sr, and Ba, and
T
=
∫
360
700
S
(
λ
)
×
R
t
(
λ
)
d
λ
∫
380
730
S
(
λ
)
×
V
(
λ
)
d
λ
(
1
)
where S(λ) is a spectral radiance of light emitted by the light-emitting device, V(λ) is a spectral luminous efficiency function for human photopic vision specified by the Commission Internationale de l'Eclairage (CIE), and R t (λ) is a sea turtle light response curve.
3. The light-emitting device according to claim 1 , wherein
the first phosphor includes at least one selected from the group consisting of a first nitride phosphor having a composition represented by Formula (1A), a second nitride phosphor having a composition represented by Formula (1B), a first fluoride phosphor having a composition represented by Formula (1C), and a second fluoride phosphor having a composition represented by Formula (1C′) with a different composition to that represented by Formula (1C),
M 1 2 Si 5 N 8 :Eu (1A)
where M 1 is an alkaline earth metal element including at least one selected from the group consisting of Ca, Sr, and Ba, and
Sr q Ca s Al t Si u N v :Eu (1B)
where q, s, t, u, and v satisfy 0≤q<1, 0<s≤1, q+s≤1, 0.9≤t≤1.1, 0.9≤u≤1.1, and 2.5≤v≤3.5,
A c [M 2 1-b Mn 4+ b F a ] (1C)
where A includes at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + , and NH 4 + , M 2 includes at least one element selected from the group consisting of Group 4 elements and Group 14 elements, b satisfies 0<b<0.2, c is an absolute value of electric charge of [M 2 1-b Mn 4+ b′ F d′ ] ion, and d satisfies 5<d<7,
A′ c′ [M 2′ 1-b′ Mn 4+ b′ F d′ ] (1C′)
where A′ includes at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + , and NH 4 + , M 2 ′ includes at least one element selected from the group consisting of Group 4 elements, Group 13 elements, and Group 14 elements, b′ satisfies 0<b′<0.2, c′ is an absolute value of electric charge of [M 2′ 1-b′ Mn 4+ b′ F d′ ] ion, and d′ satisfies 5<d′<7.
4. The light-emitting device according to claim 1 , wherein
the first phosphor further includes at least one selected from the group consisting of a second nitride phosphor having a composition represented by Formula (1B), a first fluoride phosphor having a composition represented by Formula (1C), and a second fluoride phosphor having a composition represented by Formula (1C′) with a different composition to that represented by Formula (1C),
Sr q Ca s Al t Si u N v :Eu (1B)
where q, s, t, u, and v satisfy 0≤q<1, 0<s≤1, q+s≤1, 0.9≤t≤1.1, 0.9≤u≤1.1, and 2.5≤v≤3.5,
A c [M 2 1-b Mn 4+ b F d ] (1C)
where A includes at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + , and NH 4 + , M 2 includes at least one element selected from the group consisting of Group 4 elements and Group 14 elements, b satisfies 0<b<0.2, c is an absolute value of electric charge of [M 2 1-b Mn 4+ b F d ] ion, and d satisfies 5<d<7,
A′ c′ [M 2′ 1-b′ Mn 4+ b′ F d′ ] (1C′)
where A′ includes at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + , and NH 4 + , M 2 ′ includes at least one element selected from the group consisting of Group 4 elements, Group 13 elements, and Group 14 elements, b′ satisfies 0<b′<0.2, c′ is an absolute value of electric charge of [M 2′ 1-b′ Mn 4+ b′ F d′ ] ion, and d′ satisfies 5<d′<7.
5. The light-emitting device according to claim 2 , wherein
the first phosphor further includes at least one selected from the group consisting of a second nitride phosphor having a composition represented by Formula (1B), a first fluoride phosphor having a composition represented by Formula (1C), and a second fluoride phosphor having a composition represented by Formula (1C′) with a different composition to that represented by Formula (1C),
Sr q Ca s Al t Si u N v :Eu (1B)
where q, s, t, u, and v satisfy 0≤q<1, 0<s≤1, q+s≤1, 0.9≤t≤1.1, 0.9≤u≤1.1, and 2.5≤v≤3.5,
A c [M 2 1-b Mn 4+ b F d ] (1C)
where A includes at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + , and NH 4 + , M 2 includes at least one element selected from the group consisting of Group 4 elements and Group 14 elements, b satisfies 0<b<0.2, c is an absolute value of electric charge of [M 2 1-b Mn 4+ b F d ] ion, and d satisfies 5<d<7,
A′ c′ [M 2′ 1-b ′Mn 4+ b′ F d′ ] (1C′)
where A′ includes at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + , and NH 4 + , M 2 ′ includes at least one element selected from the group consisting of Group 4 elements, Group 13 elements, and Group 14 elements, b′ satisfies 0<b′<0.2, c′ is an absolute value of electric charge of [M 2′ 1-b′ Mn 4+ b′ F d′ ] ion, and d′ satisfies 5<d′<7.
6. The light-emitting device according to claim 1 , wherein
the first phosphor has a full width at half maximum of an emission spectrum indicating a maximum emission intensity in an emission spectrum of the first phosphor within a range from 3 nm to 120 nm.
7. The light-emitting device according to claim 2 , wherein
the first phosphor has a full width at half maximum of an emission spectrum indicating a maximum emission intensity in an emission spectrum of the first phosphor within a range from 3 nm to 120 nm.
8. The light-emitting device according to claim 1 , further comprising:
a second phosphor having an emission peak wavelength within a range from 480 nm to less than 570 nm.
9. The light-emitting device according to claim 2 , further comprising:
a second phosphor having an emission peak wavelength within a range from 480 nm to less than 570 nm.
10. The light-emitting device according to claim 8 , wherein
the second phosphor includes at least one type of rare earth aluminate phosphor having a composition represented by Formula (2A),
L n 1 3 (Al 1-a Ga a ) 5 O 12 :Ce (2A)
where Ln 1 is at least one element selected from the group consisting of Y, Gd, Tb, and Lu, and a satisfies 0≤a≤0.5.
11. The light-emitting device according to claim 9 , wherein
the second phosphor includes at least one type of rare earth aluminate phosphor having a composition represented by Formula (2A),
Ln 1 3 (Al 1-a Ga a ) 5 O 12 :Ce (2A)
where Ln 1 is at least one element selected from the group consisting of Y, Gd, Tb, and Lu, and a satisfies 0≤a≤0.5.
12. The light-emitting device according to claim 8 , wherein
the second phosphor has a full width at half maximum of an emission spectrum indicating a maximum emission intensity in an emission spectrum of the second phosphor within a range from 20 nm to 125 nm.
13. The light-emitting device according to claim 9 , wherein
the second phosphor has a full width at half maximum of an emission spectrum indicating a maximum emission intensity in an emission spectrum of the second phosphor within a range from 20 nm to 125 nm.
14. The light-emitting device according to claim 8 , wherein
a content of the first phosphor relative to a total amount of the first phosphor and the second phosphor is within a range from 5 mass % to 95 mass %.
15. The light-emitting device according to claim 9 , wherein
a content of the first phosphor relative to a total amount of the first phosphor and the second phosphor is within a range from 5 mass % to 95 mass %.
16. The light-emitting device according to claim 1 , wherein
the light-emitting device emits light with a color deviation Duv from a black body radiation locus in a range from −0.008 to +0.008.
17. The light-emitting device according to claim 1 , wherein
the light-emitting device emits light with a second radiance in a range from 650 nm to 750 nm being 50% or less relative to 100% of a first radiance in a range from 400 nm to 750 nm.
18. The light-emitting device according to claim 1 , wherein
on a light emission side of the light-emitting element, a wavelength conversion member including a phosphor layer including the first phosphor and a band-pass filter layer disposed on a light emission side of the phosphor layer is provided, and
the band-pass filter layer has an average reflectivity of light with a wavelength range from 380 nm to less than 495 nm of 80% or greater and has an average reflectivity of light with a wavelength range from greater than 580 nm to 780 nm of 20% or less, with respect to light with an angle of incidence within a range from 0 degrees to 30 degrees.
19. A lighting appliance comprising:
the light-emitting device described in claim 1 .
20. A street light comprising:
the light-emitting device described in claim 1 .