Light-emitting device and backlight including light-emitting device

• US 10,529,695 B2
• Filed: 08/01/2016
• Issued: 01/07/2020
• Est. Priority Date: 08/04/2015
• Status: Active Grant

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Corporation
• Inventors: Yamamoto, Atsushi, Ono, Keiko, Yamamoto, Saiki, Maruyama, Tomokazu, Morikawa, Takeshi, Akagawa, Seitaro
• Primary Examiner(s): Lee, Diane I
• Assistant Examiner(s): Cadima, Omar Rojas
• Application Number:
  US15/224,738
• Publication Number:
  US 20170040301A1
• Time in Patent Office: 1,254 Days
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

The light-emitting device includes a first light-emitting element having an emission peak wavelength of 430 nm or more and less than 490 nm, a second light-emitting element having an emission peak wavelength of 490 nm or more and 570 nm or less, a support body at which the first light-emitting element and the second light-emitting element are disposed, and a light-transmissive member containing a red phosphor and covering the first light-emitting element and the second light-emitting element. A content density of the red phosphor in the light-transmissive member in a space between the first and second light-emitting elements is higher in a part below an upper surface of the second light-emitting element than in a part above the upper surface thereof.

Claims

1. A light-emitting device, comprising:

a first light-emitting element having an emission peak wavelength of 430 nm or more and less than 490 nm;

a second light-emitting element having an emission peak wavelength of 490 nm or more and 570 nm or less;

a support body at which the first light-emitting element and the second light-emitting element are disposed; and

a light-transmissive member containing a red phosphor and covering the first light-emitting element and the second light-emitting element, wherein

a content density of the red phosphor in the light-transmissive member located in a space between the first light-emitting element and the second light-emitting element is higher in a part below an upper surface of the second light-emitting element than in a part above the upper surface thereof, and

the red phosphors located in the light-transmissive member in a space between the first light-emitting element and the second light-emitting element settle out so as to be in contact with each other,

wherein the red phosphor includes a phosphor having a composition represented by the following formula (II);

(x−

a)MgO.a(Ma)O.b/2(Mb)₂O₃.yMgF₂.c(Mc)X₂.(1−

d−

e)GeO₂.d(Md)O₂.e(Me)₂O₃;

Mn⁴⁺ 

 

(II)

wherein Ma is at least one element selected from Ca, Sr, Ba and Zn;

Mb is at least one element selected from Sc, La and Lu;

Mc is at least one element selected from Ca, Sr, Ba and Zn;

X is at least one element selected from F and Cl;

Md is at least one element selected from Ti, Sn and Zr; and

Me is at least one element selected from B, Al, Ga and In, furthermore, x, y, a, b, c, d and e are set to satisfy the following ranges;

2≤

x≤

4;

0<

y≤

2;

0≤

a≤

1.5;

0≤

b<

1;

0≤

c≤

2;

0≤

d≤

0.5; and

0≤

e<

1.

2. The light-emitting device according to claim 1, wherein the red phosphor is at least one of a phosphor with the composition represented by the general formula (I) below and a phosphor with the composition represented by 3.5MgO.0.5MgF₂.GeO₂:

Mn⁴⁺

A₂MF₆;

Mn^{4 +} 

 

(I)

where, in the general formula (I), A is at least one selected from the group consisting of K, Li, Na, Rb, Cs and NH⁴⁺; and

M is at least one element selected from the group consisting of Group 4 elements and Group 14 elements.

3. The light-emitting device according to claim 1, wherein the first light-emitting element and the second light-emitting element are alternately arranged in a longitudinal direction and a lateral direction at an element mounting surface of the support body.

4. The light-emitting device according to claim 1, wherein a ratio of a light output from the second light-emitting element to that from the first light-emitting element is in a range of 0.3 or more and 0.7 or less.

5. The light-emitting device according to claim 1, wherein an upper surface of the second light-emitting element is positioned closer to a light extraction surface of the light-emitting device, compared to an upper surface of the first light-emitting element.

6. The light-emitting device according to claim 1, wherein the first light-emitting element and the second light-emitting element are nitride semiconductor light-emitting elements.

7. The light-emitting device according to claim 1, wherein one of positive and negative electrodes of the first light-emitting element is connected to one of positive and negative electrodes of the second light-emitting element via a wire.

8. A backlight comprising:

the light-emitting device according to claim 1; and

a light guide plate having a light input portion at a side surface thereof, wherein

the light extraction surface of the light-emitting device and the light input portion are disposed facing each other.

9. The light-emitting device according to claim 1, wherein the red phosphors in the light-transmissive member located in a space between the first light-emitting element and the second light-emitting element continuously contact the support body, the lateral surface of the first light-emitting element, and the lateral surface of the second light-emitting element.

10. The light-emitting device according to claim 1, wherein the distribution density of the red phosphor is gradually increased downward from the part above the upper surface of the second light-emitting element.

11. The light-emitting device according to claim 10, wherein the distribution density of the red phosphor is highest in the vicinity of the support body.

12. The light-emitting device according to claim 1, wherein the volume-average particle size of the red phosphor is in range of 1 μ

m or more and 100 μ

m less.

13. The light-emitting device according to claim 1, wherein the reflectance of the red phosphor to the light from the second light-emitting element is 70% or more.

14. The light-emitting device according to claim 1, wherein the red phosphor further includes a phosphor selected from the group consisting of Y₂O₂S:

Eu³⁺, La₂O₂S;

Eu³⁺, and

AEuxLn<sub>(1−

x)</sub>M₂O₈, wherein 0<

X≤

1;

A is at least one element selected from Li, Na, K, Pb and Cs;

Ln is at least one element selected from Y, La, Cd and Lu; and

M is W or Mo.

15. The light-emitting device according to claim 1, wherein the red phosphor further includes a phosphor selected from the group consisting of K₂SiF₆:

Mn⁴⁺, K₂(Si, Ge)F₆;

Mn⁴⁺and K₂TiF₆;

Mn⁴⁺.

16. The light-emitting device according to claim 1, wherein in the space between the first light-emitting element and the second light-emitting element, the content density of the red phosphor from the upper surface of the second light-emitting element to a lower surface of the light-transmissive member is two or more times as high as that of the red phosphor in the part from the upper surface of the second light-emitting element to an upper surface of the light-transmissive member.

17. The light-emitting device according to claim 1, wherein the light-transmissive member contains a diffusing agent.

18. The light-emitting device according to claim 17, wherein the diffusing agent is TiO₂ or SiO₂.