Phosphors protected against moisture and LED lighting devices

1 . A photoluminescent phosphor comprising:

a. an inorganic phosphor having one of the following formulas:

i. M1(Ga, Al) 2 S 4 :A.x(Ga, Al) 2 S 3   Ia;

ii. M1 2 SiS 4 :A  Ib;

iii. M1Si 2 S 5 :A  Ic;

iv. M2(S, Se):A,X  IIa;

v. M2S:A,X  IIb; or

vi. M2SiO 4 X:A  IIIc;

wherein, if present in the formula:

A is at least one activator cation;

M1 is at least one metal ion selected from Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ and Y 3+ ;

M2 is at least one metal ion selected from Ca 2+ , Sr 2+ , Ba 2+ and Cd 2+ ;

x is 0 to 0.2; and

X is either at least one halide in atomic or ionic form or absent; and

b. at least one layer of a coating on the inorganic phosphor, wherein the layer comprises at least one oxide;

2 . The photoluminescent phosphor of claim 1 , wherein A is Eu 2+ , Cu 2+ , Cu + , Yb 2+ , Mn 2+ , Bi + , Bi 3+ , Sb 3+ , Pb 2+ , La 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ or Lu 3+ .

3 . The photoluminescent phosphor of claim 1 , wherein the coating is continuous.

4 . The photoluminescent phosphor of claim 1 , wherein the oxide is titanium oxide, aluminum oxide, zirconium oxide, tin oxide, boron oxide, silicon oxide, zinc oxide, germanium oxide, aluminum silicate, Al 8 BSi 3 O 19 (OH), B 2 Al 2 (SiO 4 ) 2 (OH), ZnAl 2 O 4 , Al 2 SiO 5 , Al 4 (SiO 4 ) 3 , ZrSiO 4 , or a combination thereof.

5 . The photoluminescent phosphor of claim 1 , wherein the oxide of the coating is titanium oxide, aluminum oxide or silicon oxide.

6 . The photoluminescent phosphor of claim 1 , wherein the coating on the inorganic phosphor comprises at least two layers.

7 . The photoluminescent phosphor of claim 6 , wherein each layer independently comprises an oxide selected from titanium oxide, aluminum oxide, silicon oxide and a combination thereof.

8 . The photoluminescent phosphor of claim 7 , wherein one layer comprises titanium oxide.

9 . The photoluminescent phosphor of claim 1 , wherein the photoluminescent phosphor retains about 40% or more of its original emission intensity when maintained at about 85° C. and about 85% relative humidity for about 4 hours.

10 . The photoluminescent phosphor of claim 1 , wherein the photoluminescent phosphor retains about 40% or more of its original emission intensity when maintained at about 85° C. and about 85% relative humidity for about 96 hours.

11 . The photoluminescent phosphor of claim 10 , wherein the oxide comprises titanium oxide.

12 . The photoluminescent phosphor of claim 11 , wherein the oxide comprises silicon oxide.

13 . The photoluminescent phosphor of claim 1 , wherein the inorganic phosphor has one of the following formulas:

a. M1(Ga, Al) 2 S 4 :A.x(Ga, Al) 2 S 3   Ia;

b. M1Ga 2 S 4 :A.xGa 2 S 3   Id;

c. M2(S, Se):A,X  IIa; or

d. M2S:A,X  IIb.

14 . The photoluminescent phosphor of claim 13 , wherein:

a. M1 is Ca 2+ , Sr 2+ or a combination thereof; and

b. M2 is Ca 2+ , Sr 2+ or a combination thereof.

15 . The photoluminescent phosphor of claim 14 , wherein A is Eu 2+ .

16 . The photoluminescent phosphor of claim 13 , wherein the oxide comprises titanium oxide.

17 . The photoluminescent phosphor of claim 16 , wherein the oxide comprises silicon oxide, aluminum oxide or a combination thereof.

18 . The photoluminescent phosphor of claim 1 , wherein the inorganic phosphor is:

a. CaS:Bi + , Na + ;

b. CaS:Ce 3+ ;

c. CaS:Cu + , Na + ;

d. CaS:Eu 2+ ;

e. CaS:La 3+ ;

f. CaS:Pb 2+ , Mn 2+ ;

g. CaS:Sb 3+ ;

h. CaS:Sb 3+ , Na + ;

i. SrS:Ce 3+ ;

j. SrS:Cu + , Na + ;

k. SrS:Eu 2+ ;

l. SrS:Mn 2+ ;

m. Sr α Ca 1-α S:Eu 2+ , wherein α=0-1;

n. Sr β Ca 1-β S:Ce 3+ , wherein β=0-1;

o. Sr γ Ca 1-γ S:Pb 2+ , Mn 2+ , wherein γ=0-1;

p. Zn ε1 Cd 1-ε1 S:Cu + , Al 3+ , wherein ε1=0-1;

q. Zn ε2 Cd 1-ε2 S:Ag + , Cl − , wherein ε2=0-1;

r. Zn(S, Se):Cu + , Ag + ;

s. MgS:Eu 2+ ;

t. CaGa 2 S 4 :Ce 3+ ;

u. CaGa 2 S 4 :Eu 2+ ;

v. CaGa 2 S 4 :Mn 2+ ;

w. CaGa 2 S 4 :Pb 2+ ;

x. ZnGa 2 S 4 :Mn 2+ ;

y. SrGa 2 S 4 :Pb 2+ ;

z. BaAl 2 S 4 :Eu 2+ ;

aa. SrGa 2 S 4 :Ce 3+ ;

bb. SrGa 2 S 4 :Eu 2+ ;

cc. Sr δ Ca 1-δ Ga 2 S 4 :Eu, wherein δ=0-1;

dd. Ca 2 SiS 4 :Eu 2+ ;

ee. Ca 3 SiO 4 Cl 2 :Eu 2+ ;

ff. Sr 2 SiS 4 :Eu 2+ ;

gg. Ba 2 SiS 4 :Eu 2+ ;

hh. SrSi 2 S 5 :Eu 2+ ;

ii. BaSi 2 S 5 :Eu 2+ ;

jj. SrAl 2 S 4 :Eu 2+ ; or

kk. CaAl 2 S 4 :Eu 2+ .

19 . A lighting device comprising:

a. a light source that emits light at wavelengths of at least about 300 nm; and

b. a photoluminescent phosphor according to claim 1 ,

wherein:

i. the photoluminescent phosphor is capable of absorbing at least a portion of the light emitted from the light source;

ii. the photoluminescent phosphor modifies the chromaticity of the portion of the light absorbed from the light source; and

iii. the photoluminescent phosphor emits light of a longer wavelength than that of the light absorbed from the light source.

20 . The lighting device of claim 19 , wherein the lighting device produces white light.

21 . The lighting device of claim 19 , wherein the inorganic phosphor comprises the formula: M1Ga 2 S 4 :A:xGa 2 S 3 (Ia)or M2S:A,X (IIb).

22 . The lighting device of claim 19 , wherein the light source is a LED.