U.S. patent application number 11/640533 was filed with the patent office on 2008-02-07 for led lighting arrangement including light emitting phosphor.
This patent application is currently assigned to Intematix Corporation. Invention is credited to Yi-Qun Li.
Application Number | 20080029720 11/640533 |
Document ID | / |
Family ID | 39028247 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080029720 |
Kind Code |
A1 |
Li; Yi-Qun |
February 7, 2008 |
LED lighting arrangement including light emitting phosphor
Abstract
A lighting arrangement (20) comprises: a radiation source, LED
chip, (22) configured to emit radiation having a first wavelength
range; a phosphor, photoluminescent material, (30) configured to
absorb at least a portion of said first wavelength range radiation
and emit radiation having a second wavelength range; and an optical
component, lens, (26) through which at least said first wavelength
range radiation passes. The LED is characterized in that the
phosphor is provided on a surface (28) of the optical
component.
Inventors: |
Li; Yi-Qun; (Danville,
CA) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Intematix Corporation
Fremont
CA
|
Family ID: |
39028247 |
Appl. No.: |
11/640533 |
Filed: |
December 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60835601 |
Aug 3, 2006 |
|
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Current U.S.
Class: |
250/581 |
Current CPC
Class: |
C09K 11/7734 20130101;
C09K 11/7741 20130101; F21Y 2103/10 20160801; Y10T 428/31663
20150401; F21V 3/12 20180201; Y10T 428/24479 20150115; F21V 13/14
20130101; H01L 2933/0041 20130101; Y10T 428/13 20150115; C09K
11/0883 20130101; C09K 11/7774 20130101; H01L 33/502 20130101; F21Y
2115/10 20160801; F21Y 2115/30 20160801; F21V 5/041 20130101; Y10T
428/31511 20150401; Y10T 428/265 20150115; F21V 5/10 20180201 |
Class at
Publication: |
250/581 |
International
Class: |
G21K 4/00 20060101
G21K004/00 |
Claims
1. A lighting arrangement comprising: a radiation source configured
to emit radiation having a first wavelength range; a phosphor
configured to absorb at least a portion of said first wavelength
range radiation and emit radiation having a second wavelength
range; and an optical component through which at least said first
wavelength range radiation passes, characterized in that the
phosphor is provided on a surface of the optical component.
2. The lighting arrangement according to claim 1, in which the
phosphor is provided as a substantially uniform thickness layer on
said surface of the optical component.
3. The lighting arrangement according to claim 1 or claim 2, in
which the optical component has a substantially planar surface and
the phosphor is provided on said substantially planar surface.
4. The lighting arrangement according to claim 1 or claim 2, in
which the optical component has a convex surface and the phosphor
is provided on said convex surface.
5. The lighting arrangement according to claim 1 or claim 2, in
which the optical component has a concave surface and the phosphor
is provided on said concave surface.
6. The lighting arrangement according to claim 1 or claim 2, in
which the optical component has a substantially hemispherical
surface and the phosphor is provided on said hemispherical
surface.
7. The lighting arrangement according to claim 6, in which the
optical component comprises a substantially hemispherical shell and
the phosphor is provided on the inner hemispherical surface.
8. The lighting arrangement according to claim 6, in which the
optical component comprises a substantially hemispherical shell and
the phosphor is provided on at least a part of the outer
hemispherical surface.
9. The lighting arrangement according to claim 1 or claim 2, in
which the optical component comprises a substantially spherical
shell and the phosphor is provided on at least a part of the inner
spherical surface.
10. The lighting arrangement according to claim 1 or claim 2, in
which the optical component comprises a substantially spherical
shell and the phosphor is provided on at least a part of the outer
spherical surface.
11. The lighting arrangement according to claim 1 or claim 2, in
which the optical component comprises a hollow cylinder and the
phosphor is provided on at least a part of the inner surface.
12. The lighting arrangement according to claim 1 or claim 2, in
which the optical component comprises a hollow cylinder and the
phosphor is provided on at least a part of the outer surface.
13. The lighting arrangement according to claim 1 to 2, in which
the optical component is made from one of a plastics material,
glass.
14. The lighting arrangement according to claim 1, in which the
phosphor comprises a powder which is incorporated within one of an
epoxy resin, a silicone material and a polymer material to form a
mixture and in which the phosphor mixture is applied to the optical
component to form a layer of phosphor on the optical component
surface.
15. The lighting arrangement according to claim 14, and further
comprising incorporating a light diffusing material with the
phosphor powder.
16. The lighting arrangement according to any of claims 1, 2, 14 or
15, in which the phosphor comprises a photoluminescent material
having a formula A.sub.2SiO.sub.4:Eu.sup.2+D where A is a divalent
metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn and
Cd and D is a dopant selected from the group consisting of F, Cl,
Br, I, P, S and N.
17. The lighting arrangement according to any one of claims 1, 2,
14 or 15, in which the phosphor comprises a photoluminescent
material having a formula
(YA).sub.3(AlB).sub.5(OC).sub.12:Ce.sup.3+ where A is a trivalent
metal selected from the group consisting of Gd, Tb, La, Sm or
divalent metal ions such as Sr, Ca, Ba, Mg, Zn and Cd; B is
selected from the group consisting of Si, B, P, and Ga; and C is a
dopant selected from the group consisting of F, Cl, Br, I, P, S and
N.
18. The lighting arrangement according to any one of claims 1, 2,
14 or 15, in which the phosphor comprises an orange-red
silicate-based phosphor having a formula
(SrM1).sub.3Si(OD).sub.5:Eu where M1 is selected from the group
consisting of Ba, Ca, Mg, Zn . . . ; and D is selected from the
group consisting of F, Cl, S, and N.
19. The lighting arrangement according to any one of claims 1, 2 14
or 15, in which the phosphor comprises a red silicon nitride based
phosphor having a formula (SrM1)Si.sub.5N.sub.8 where M1 is
selected from the group consisting Sr, Ca, Mg, and Zn.
20. The lighting arrangement according to any one of claims 1, 2,
14 or 15, in which the phosphor comprises a red sulfate based
phosphor having a formula (SrM1)S where M1 is selected from the
group consisting of Ca, Ba, and Mg.
21. The lighting arrangement according to any one of claims 1, 2 14
or 15, in which the phosphor comprises a green sulfate based
phosphor having a formula (SrM1)(GaM2).sub.2S.sub.4:Eu where M1 is
selected from the group consisting of Ca, Ba, and Mg, and M2 is
selected from the group consisting of Al and In.
22. The lighting arrangement according to claim 1, in which the
radiation source comprises a light emitting diode.
23. The lighting arrangement according to claim 1, in which said
LED chip comprises a Gallium Nitride LED.
24. The lighting arrangement according to claim 1, in which said
radiation source is operable to emit radiation having a wavelength
range of 300 to 500 nm.
25. The lighting arrangement according to claim 1, in which the
phosphor is configured to emit radiation having a wavelength
ranging from 450 to 700 nm.
26. An optical component for a lighting arrangement of a type
comprising a radiation source configured to emit radiation having a
first wavelength range; a phosphor configured to absorb at least a
portion of said first wavelength range radiation and emit radiation
having a second wavelength range; and said optical component being
configured such that at least said first wavelength range radiation
passes though the optical component, and characterized in that said
phosphor is provided on a surface of said optical component.
27. The optical component according to claim 26, in which the
phosphor is provided as a substantially uniform thickness layer on
said surface of the optical component.
28. The optical component according to claim 26 or claim 27, in
which the optical component has a substantially planar surface and
the phosphor is provided on said substantially planar surface.
29. The optical component according to claim 26 or claim 27, in
which the optical component has a convex surface and the phosphor
is provided on said convex surface.
30. The optical component according to claim 26 or claim 27, in
which the optical component has a concave surface and the phosphor
is provided on said concave surface.
31. The optical component according to claim 26 or claim 27, in
which the optical component has a substantially hemispherical
surface and the phosphor is provided on said hemispherical
surface.
32. The optical component according to claim 31, in which the
optical component comprises a substantially hemispherical shell and
the phosphor is provided on the inner hemispherical surface.
33. The optical component according to claim 31, in which the
optical component comprises a substantially hemispherical shell and
the phosphor is provided on at least a part of the outer
hemispherical surface.
34. The optical component according to claim 26 or claim 27, in
which the optical component comprises a substantially spherical
shell and the phosphor is provided on at least a part of the inner
spherical surface.
35. The optical component according to claim 26 or claim 27, in
which the optical component comprises a substantially spherical
shell and the phosphor is provided on at least a part of the outer
spherical surface.
36. The optical component according to claim 26 or claim 27, in
which the optical component comprises a hollow cylinder and the
phosphor is provided on at least a part of the inner surface.
37. The optical component according to claim 26 or claim 27 in
which the optical component comprises a hollow cylinder and the
phosphor is provided on at least a part of the outer surface.
38. The optical component according to claim 26 or 27, in which the
phosphor comprises a powder which is incorporated within one of an
epoxy resin, a silicone material and a polymer material to form a
mixture and in which the phosphor mixture is applied to the optical
component to form a layer of phosphor on the optical component
surface.
39. The optical component according to claim 38, and further
comprising a light diffusing material with the phosphor powder.
40. The optical component according to claim 26 or 27, in which the
optical component is fabricated from one of a plastics material, a
glass.
41. The optical component according to claim 26 or 27 in which the
phosphor comprises a photoluminescent material having a formula
A.sub.2SiO.sub.4:Eu.sup.2+D where A is a divalent metal selected
from the group consisting of Sr, Ca, Ba, Mg, Zn and Cd and D is a
dopant selected from the group consisting of F, Cl, Br, I, P, S and
N.
42. The optical component according to claim 26 or 27, in which the
phosphor comprises a photoluminescent material having a formula
(YA).sub.3(AlB).sub.5(OC).sub.12:Ce.sup.3+ where A is a trivalent
metal selected from the group consisting of Gd, Tb, La, Sm or
divalent metal ions such as Sr, Ca, Ba, Mg, Zn and Cd; B is
selected from the group Si, B, P, and Ga; and C is a dopant
selected from the group consisting of F, Cl, Br, I, P, S and N.
43. The optical component according to claim 26 or 27, in which the
phosphor comprises an orange-red silicate-based phosphor having a
formula (SrM1).sub.3Si(OD).sub.5:Eu where M1 is selected from the
group consisting of Ba, Ca, Mg, and Zn, and D is selected from the
group consisting of F, Cl, S, and N.
44. The lighting arrangement according to claim 26 or 27, in which
the phosphor comprises a red silicon nitride based phosphor having
a formula (SrM1)Si.sub.5N.sub.8 where M1 is selected from the group
consisting of Sr, Ca, Mg, and Zn.
45. The lighting arrangement according to claim 26 or 27, in which
the phosphor comprises a red sulfate based phosphor having a
formula (SrM1)S where M1 is selected from the group consisting of
Ca, Ba, and Mg.
46. The lighting arrangement according to claim 26 or 27, in which
the phosphor comprises a green sulfate based phosphor having a
formula (SrM1)(GaM2).sub.2S.sub.4:Eu where M1 is selected from the
group consisting of Ca, Ba, and Mg, and M2 is selected from the
group consisting of Al and In.
47. A method of fabricating a lighting arrangement comprising:
providing a radiation source configured to emit radiation having a
first wavelength range and an optical component through which said
radiation passes; and providing on a surface of the optical
component a phosphor configured to absorb at least a portion of
said first wavelength range radiation and emit radiation having a
second wavelength range.
48. The method according to claim 47, and comprising providing the
phosphor as a substantially uniform thickness layer on said surface
of the optical component.
49. The method according to claim 47 or claim 48, in which the
optical component has a substantially planar surface and comprising
providing the phosphor on said substantially planar surface.
50. The method according to claim 47 or claim 48, in which the
optical component has a convex surface and comprising providing the
phosphor on said convex surface.
51. The method according to claim 47 or claim 48, in which the
optical component has a concave surface and comprising providing
the phosphor on said concave surface.
52. The method according to claim 47 or claim 48, in which the
optical component has a substantially hemispherical surface and
comprising providing the phosphor on said hemispherical
surface.
53. The method according to claim 52, in which the optical
component comprises a substantially hemispherical shell and
comprising providing the phosphor on the inner hemispherical
surface.
54. The method according to claim 52, in which the optical
component comprises a substantially hemispherical shell and
comprising providing the phosphor on at least a part of the outer
hemispherical surface.
55. The method according to claim 47 or claim 48, in which the
optical component comprises a substantially spherical shell and
comprising providing the phosphor on at least a part of the inner
spherical surface.
56. The method according to claim 47 or claim 48, in which the
optical component comprises a substantially spherical shell and
comprising providing the phosphor on at least a part of the outer
spherical surface.
57. The method according to claim 47 or claim 48, in which the
optical component comprises a hollow cylinder and comprising
providing the phosphor on at least a part of the inner surface.
58. The method according to claim 47 or claim 48, in which the
optical component comprises a hollow cylinder and comprising
providing the phosphor on at least a part of the outer surface.
59. The method according to claim 47 or 48 in which the optical
component is fabricated from one of a plastics material, a
glass.
60. A method of fabricating an optical component for a lighting
arrangement of a type comprising a radiation source configured to
emit radiation having a first wavelength range; a phosphor
configured to absorb at least a portion of said first wavelength
range radiation and emit radiation having a second wavelength
range; and said optical component being configured such that at
least said first wavelength range radiation passes through said
optical component, the method comprising providing said phosphor on
a surface of the optical component.
61. The method according to claim 60, and comprising providing the
phosphor as a substantially uniform thickness layer.
62. The method according to claim 60 or claim 61, in which the
optical component has a substantially planar surface and comprising
providing the phosphor on said substantially planar surface.
63. The method according to claim 60 or claim 61, in which the
optical component has a convex surface and comprising providing the
phosphor on said convex surface.
64. The method according to claim 60 or claim 61, in which the
optical component has a concave surface and comprising providing
the phosphor on said concave surface.
65. The method according to claim 60 or claim 61, in which the
optical component has a substantially hemispherical surface and
comprising providing the phosphor on said hemispherical
surface.
66. The method according to claim 65, in which the optical
component comprises a substantially hemispherical shell and
comprising providing the phosphor on the inner hemispherical
surface.
67. The method according to claim 65, in which the optical
component comprises a substantially hemispherical shell and
comprising providing the phosphor on at least a part of the outer
hemispherical surface.
68. The method according to claim 60 or 61, in which the optical
component comprises a substantially spherical shell and comprising
providing the phosphor on at least a part of the inner spherical
surface.
69. The method according to claim 60 or 61, in which the optical
component comprises a substantially spherical shell and comprising
providing the phosphor on at least a part of the outer spherical
surface.
70. The method according to claim 60 or 61, in which the optical
component comprises a hollow cylinder and comprising providing the
phosphor on at least a part of the inner surface.
71. The method according to claim 60 or 61, in which the optical
component comprises a hollow cylinder and comprising providing the
phosphor on at least a part of the outer surface.
72. The method according to claim 60 or 61, in which the phosphor
comprises a powder and comprising incorporating the phosphor within
one of a epoxy resin, silicone material, polymer material to form a
mixture and applying the phosphor mixture to the optical component
to form a layer of phosphor on the optical component surface.
73. The method according to claim 60, and further comprising
incorporating a light diffusing material with the phosphor
powder.
74. The method according to any one of claims 60, 61 or 73, in
which the phosphor comprises a photoluminescent materials have a
formula A.sub.2SiO.sub.4:Eu.sup.2+D where A is a divalent metal
selected from the group consisting of Sr, Ca, Ba, Mg, Zn and Cd and
D is a dopant selected from the group consisting of F, Cl, Br, I,
P, S and N.
75. The lighting arrangement according to any one of claims 60, 61
or 73, in which the phosphor comprises a photoluminescent material
having a formula (YA).sub.3(AlB).sub.5(OC).sub.12:Ce.sup.3+ where A
is a trivalent metal selected from the group consisting of Gd, Tb,
La, Sm or divalent metal ions such as Sr, Ca, Ba, Mg, Zn and Cd; B
is selected from the group consisting of Si, B, P, and Ga; and C is
a dopant selected from the group consisting of F, Cl, Br, I, P, S
and N.
76. The lighting arrangement according to any one of claims 60, 61
or 73, in which the phosphor comprises an orange-red silicate-based
phosphor having a formula (SrM1).sub.3Si(OD).sub.5:Eu where M1 is
selected from the group consisting of Ba, Ca, Mg, and Zn, and D is
selected from the group consisting of F, Cl, S, and N.
77. The lighting arrangement according to any one of claims 60, 61
or 73, in which the phosphor comprises a red silicon nitride based
phosphor having a formula (SrM1)Si.sub.5N.sub.8 where M1 is
selected from the group consisting of Sr, Ca, Mg, and Zn.
78. The lighting arrangement according to any one of claims 60, 61
or 73, in which the phosphor comprises a red sulfate based phosphor
having a formula (SrM1)S where M1 is selected from the group
consisting of Ca, Ba, and Mg.
79. The lighting arrangement according to any one of claim 60, 61
or 73, in which the phosphor comprises a green sulfate based
phosphor having a formula (SrM1)(GaM2).sub.2S.sub.4:Eu where M1 is
selected from the group consisting of Ca, Ba, and Mg, and M2 is
selected from the group consisting of Al, and In.
80. The method according to any one of claims 60, 61 or 73, and
comprising fabricating the optical component from one of a plastics
material, glass.
81. The method according to claim 60 and further comprising
providing a plurality of optical components in the form of an array
said array of optical components having a common planar surface and
depositing said phosphor on the planar surface.
82. The method according to claim 81, and comprising providing the
phosphor as a substantially uniform thickness layer on said planar
surface of the array of optical components.
83. A phosphor material for coating an optical component of an LED
lighting arrangement comprising a phosphor powder incorporated
within one of an epoxy resin, a silicone material and a polymer
material.
84. The phosphor material according to claim 83 and further
comprising a light diffusing material.
85. An optical component for a lighting arrangement of a type
comprising a radiation source configured to emit radiation having a
first wavelength range; a phosphor configured to absorb at least a
portion of said first wavelength range radiation and emit radiation
having a second wavelength range; and said optical component being
configured such that at least said first wavelength range radiation
passes through said optical component, and characterized in that
said phosphor is incorporated in said optical component.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to solid-state lighting applications
which comprise light emitting diodes (LEDs) which include a light
emitting phosphor, photoluminescent material, to generate light of
a desired color, that is in a different part of the wavelength
spectrum from the LEDs. In particular, although not exclusively,
the invention concerns LED-based lighting arrangements which
generate light in the visible part of the spectrum and in
particular, although not exclusively white light. Moreover the
invention provides an optical component for such a lighting
arrangement and methods of fabricating a lighting arrangement and
an optical component. Furthermore the invention provides a phosphor
material for coating an optical component or as a part of optical
designs in lighting arrangements.
[0003] 2. State of the Art
[0004] In the context of this patent application light is defined
as electromagnetic radiation in a wavelength range 300 nm
(Ultraviolet) to 1000 nm (Infrared). Primarily, although not
exclusively the invention concerns lighting arrangements which emit
light in the visible part of the spectrum that is 380 to 750
nm.
[0005] White light emitting diodes (LEDs) are known in the art and
are a relatively recent innovation. It was not until LEDs emitting
in the blue/ultraviolet of the electromagnetic spectrum were
developed that it became practical to develop white light sources
based on LEDs. As is known white light generating LEDs ("white
LEDs") include a phosphor, that is a photoluminescent material,
which absorbs a portion of the radiation emitted by the LED and
re-emits radiation of a different color (wavelength). For example
the LED emits blue light in the visible part of the spectrum and
the phosphor re-emits yellow light. Alternatively the phosphor can
emit a combination of green and red light, green and yellow or
yellow and red light. The portion of the visible blue light emitted
by the LED which is not absorbed by the phosphor mixes with the
yellow light emitted to provide light which appears to the eye as
being white. A known yellow phosphor is a YAG-based phosphor having
a main emission wavelength peak that varies in wavelength range
from 530 to 590 nm depending on the composition of the phosphors.
Further examples of phosphors are described in our co-pending
patent application U.S. 2006/0028122 in which the photoluminescent
materials have a formula A.sub.2SiO.sub.4:Eu.sup.2+D where A is a
divalent metal selected from the group consisting of Sr, Ca, Ba,
Mg, Zn and Cd and D is a dopant selected from the group consisting
of F, Cl, Br, I, P, S and N. Such phosphors emit light of
intensities that are greater than either known YAG compounds or
silicate-based phosphors.
[0006] It is predicted that white LEDs could potentially replace
incandescent light sources due to their long operating lifetimes,
typically many 100,000 of hours, and their high efficiency. Already
high brightness LEDs are used in vehicle brake lights and
indicators as well as traffic lights and flash lights.
[0007] To increase the intensity of light emitted from an LED it is
known to include a lens made of a plastics material or glass to
focus the light emission and to thereby increase intensity.
Referring to FIG. 1 a high brightness white LED 2 is shown. The LED
2 comprises an LED chip 4 which is mounted within a plastic or
metal reflection cup 6 and the LED chip is then encapsulated within
an encapsulating material, typically an epoxy resin 8. The
encapsulation material includes the phosphor material for providing
color conversion. Typically the inner surface of the cup 6 is
silvered to reflect stray light towards a lens 10 which is mounted
on the surface of the encapsulating epoxy resin 8.
[0008] The inventor has appreciated that such an arrangement has
limitations and the present invention arose in an endeavor to
mitigate, at least in part, these limitations. For example for high
intensity LEDs having a high intensity output larger than 1 W, the
high temperature at the output of the LED combined with its close
proximity the phosphor material can give rise to a light
characteristic which is temperature dependent and in some cases
thermal degradation of the phosphor material can occur. Moreover
the uniformity of color of light emitted by such LEDs can be
difficult to maintain with the phosphor distributed within the
epoxy resin since light passing through different path lengths will
encounter and be absorbed by differing amounts of phosphor.
Furthermore the fabrication of such LEDs is time consuming due to
the encapsulation and subsequent placement of the lens.
SUMMARY OF THE INVENTION
[0009] According to a first aspect of the invention there is
provided a lighting arrangement comprising: a radiation source
configured to emit radiation having a first wavelength range; a
phosphor configured to absorb at least a portion of said first
wavelength range radiation and emit radiation having a second
wavelength range; and an optical component through which at least
said first wavelength range radiation passes, characterized in that
the phosphor is provided on a surface of the optical component. The
invention provides the advantage of reducing the manufacturing
steps and hence cost and also provides a more uniform color of
output light.
[0010] Advantageously the phosphor is provided as a substantially
uniform thickness layer on said surface of the optical component.
Such an arrangement ensures a more uniform color of emitted
light.
[0011] The optical component can have a number of forms and
typically comprises a lens for focusing the radiation to increase
the intensity of the emitted light. Alternatively the optical
component can be for directing the radiation thus acting as a
waveguide or as a window through which the radiation passes. The
phosphor can be provided on inner or outer surfaces of the optical
component and this will determine whether said second wavelength
range radiation also passes through the optical component. For
example in one implementation the optical component has a
substantially planar surface and the phosphor is provided on said
substantially planar surface. An advantage of applying the phosphor
to the planar surface is that it is easier to produce a uniform
thickness layer. Alternatively the optical component can have a
convex or concave surface and the phosphor is provided on said
convex or concave surfaces.
[0012] In one implementation the optical component has a
substantially hemispherical surface and the phosphor is provided on
said hemispherical surface. Preferably, the optical component
comprises a substantially hemispherical shell and the phosphor is
provided on the inner hemispherical surface. Alternatively the
phosphor can be provided on at least a part of the outer
hemispherical surface. In a further alternative embodiment the
optical component comprises a substantially spherical shell and the
phosphor is provided on at least a part of the inner or outer
spherical surfaces. Such a form finds particular application as a
light source for replacing incandescent light sources. In yet a
further embodiment the optical component comprises a hollow
cylinder and the phosphor is provided on at least a part of the
inner or outer surfaces.
[0013] Advantageously, the optical component is made of a plastics
material such as a polycarbonate and silicone or a glass such as a
silica-based glass. The optical component comprises a material
which is at least substantially transparent to said first
wavelength range radiation and where the phosphor is provided on an
inner surface of the component the material is further
substantially transparent to the second wavelength range
radiation.
[0014] In a preferred implementation the phosphor comprises a
powder which is incorporated within an epoxy resin, a silicone
material or a polymer material to form a mixture and the phosphor
mixture is then applied to the optical component to form a layer of
phosphor on the optical component surface. To improve the
uniformity of light emitted from the lighting arrangement the
phosphor mixture advantageously further incorporates a light
diffusing material such as titanium oxide, silica, alumina, etc.
Such a light diffusing material has as low an absorption of light
as possible.
[0015] The phosphor advantageously comprises a phosphor which emits
luminescent light when illuminated by radiation in wavelength range
from 300 nm to 550 nm. One example of the phosphor advantageously
comprises a YAG-based phosphor which comprises a photoluminescent
material having a formula
(YA).sub.3(AlB).sub.5(OC).sub.12:Ce.sup.3+ where A is a trivalent
metal selected from the group comprising Gd, Tb, La, Sm or divalent
metal ions such as Sr, Ca, Ba, Mg, Zn and Cd, B comprising Si, B,
P, and Ga and C is a dopant selected from the group comprising F,
Cl, Br, I, P, S and N. In another implementation the phosphor
comprises a photoluminescent material having a formula
A.sub.2SiO.sub.4:Eu.sup.2+D where A is a divalent metal selected
from the group comprising Sr, Ca, Ba, Mg, Zn and Cd and D is a
dopant selected from the group comprising F, Cl, Br, I, P, S and
N.
[0016] In yet a further embodiment an orange-red silicate-based
phosphor having a formula (SrM1).sub.3Si(OD).sub.5:Eu where M1 is
selected from the group comprising Ba, Ca, Mg, Zn . . . and where D
is selected from the group comprising F, Cl, S, and N. Such a
phosphor is advantageously used for emitting light in a wavelength
range from green to yellow (580 to 630 nm).
[0017] Alternatively the phosphor comprises a red silicon nitride
based phosphor having a formula (SrM1)Si.sub.5N.sub.8 where M1 is
selected from the group comprising Sr, Ca, Mg, and Zn.
[0018] In another embodiment the phosphor comprises a red sulfate
based phosphor having a formula of (SrM1)S where M1 is selected
from the group comprising Ca, Ba, and Mg.
[0019] In yet another embodiment the phosphor can comprise a green
sulfate based phosphor having a formula of
(SrM1)(GaM2).sub.2S.sub.4:Eu where M1 is selected from the group
comprising Ca, Ba, and Mg, and M2 is selected from the group
comprising Al and In.
[0020] Preferably, the radiation source comprises a light emitting
diode, advantageously a Gallium Nitride based LED.
[0021] The present invention finds particular application for white
light sources and the radiation source is operable to emit
radiation having a wavelength range of 300 to 500 nm. Preferably,
the phosphor composition is configured to emit radiation having a
wavelength ranging from 450 to 700 nm.
[0022] According to a second aspect of the invention there is
provided an optical component for a lighting arrangement of a type
comprising a radiation source configured to emit radiation having a
first wavelength range; a phosphor configured to absorb at least a
portion of said first wavelength range radiation and emit radiation
having a second wavelength range; and said optical component
configured such that at least said first wavelength range radiation
passes through the optical component, and characterized in that
said phosphor is provided on a surface of said optical
component.
[0023] Such an optical component provides the advantages of
reducing the manufacturing steps and hence cost and emits a more
uniform color light. Moreover such an optical component can be used
to provide direct color conversion in an LED arrangement.
[0024] To ensure the uniformity of color of light generated by the
optical component, the phosphor is advantageously provided as a
substantially uniform thickness layer on said surface of the
optical component.
[0025] For ease of fabrication the optical component preferably has
a substantially planar surface and the phosphor is provided on said
substantially planar surface. Alternatively, the optical component
has a convex or concave surface and the phosphor is provided on
said convex or concave surfaces by for example spraying or printing
related coating methods.
[0026] In one implementation the optical component has a
substantially hemispherical surface and the phosphor is provided on
said hemispherical surface. The optical component can comprise a
substantially hemispherical shell and the phosphor is provided on
the inner hemispherical surface. Such an arrangement provides
environmental protection of the phosphor. Alternatively, the
phosphor is provided on the outer hemispherical surface. In a
further embodiment the optical component comprises a substantially
spherical shell and the phosphor is provided on at least a part of
the inner or outer spherical surfaces. In yet a further
implementation the optical component comprises a hollow cylinder
and the phosphor is provided on at least a part of the inner or
outer surfaces.
[0027] Preferably, the phosphor comprises a powder which is
incorporated within an epoxy resin, a silicone material or a
polymer material to form a mixture and then the phosphor mixture is
applied to the optical component to form a layer of phosphor on the
optical component surface. To ensure a uniform light intensity
output the phosphor mixture advantageously further comprises a
light diffusing material.
[0028] Preferably, the optical component is fabricated from a
plastics material or a glass.
[0029] The phosphor advantageously comprises a photoluminescent
material having a formula A.sub.2SiO.sub.4:Eu.sup.2+D where A is a
divalent metal selected from the group comprising Sr, Ca, Ba, Mg,
Zn and Cd and D is a dopant selected from the group comprising F,
Cl, Br, I, P, S and N.
[0030] According to third aspect of the invention there is provided
a method of fabricating a lighting arrangement comprising:
providing a radiation source configured to emit radiation having a
first wavelength range and an optical component through which said
radiation passes; and providing on a surface of the optical
component a phosphor configured to absorb at least a portion of
said first wavelength range radiation and emit radiation having a
second wavelength range.
[0031] Advantageously the method further comprises providing the
phosphor as a substantially uniform thickness layer on said surface
of the optical component.
[0032] The optical component can have a substantially planar
surface, convex or concave surfaces and the method comprises
providing the phosphor on said substantially planar surface, convex
or concave surfaces.
[0033] In one implementation the optical component has a
substantially hemispherical surface and the method comprises
providing the phosphor on said hemispherical surface. Preferably,
the optical component comprises a substantially hemispherical shell
and the method comprises providing the phosphor on the inner or
outer hemispherical surfaces. Alternatively, the optical component
can comprise a substantially spherical shell and the method
comprises providing the phosphor on at least a part of the inner or
outer spherical surfaces. In a further alternative arrangement the
optical component comprises a hollow cylinder and the method
comprises providing the phosphor on at least a part of the inner or
outer surfaces.
[0034] The optical component is preferably fabricated from a
plastics material or glass.
[0035] According to a further aspect of the invention there is
provided a method of fabricating an optical component for a
lighting arrangement of a type comprising a radiation source
configured to emit radiation having a first wavelength range; a
phosphor configured to absorb at least a portion of said first
wavelength range radiation and emit radiation having a second
wavelength range; and said optical component being configured such
that at least said first wavelength range radiation passes through
the optical component the method comprising providing said phosphor
on a surface of the optical component.
[0036] To ensure uniform color conversion the method advantageously
comprises providing the phosphor as a substantially uniform
thickness layer.
[0037] When the optical component has a substantially planar
surface the method preferably comprises providing the phosphor on
said substantially planar surface.
[0038] Alternatively where the optical component has a convex or
concave surface the method can comprise providing the phosphor on
said convex or concave surfaces.
[0039] In yet a further alternative arrangement the optical
component has a substantially hemispherical surface and the method
comprises providing the phosphor on said hemispherical surface.
Where the optical component comprises a substantially hemispherical
shell the method comprises providing the phosphor on the inner or
outer hemispherical surfaces. Moreover where the optical component
comprises a substantially spherical shell the method comprises
providing the phosphor on at least a part of the inner or outer
spherical surfaces. Alternatively the optical component can
comprise a hollow cylinder and the method comprises providing the
phosphor on at least a part of the inner or outer surfaces.
[0040] In a preferred method the phosphor comprises a powder and
the method comprises incorporating the phosphor within an epoxy
resin or silicone material or polymer material to form a mixture
and then applying the phosphor mixture to the optical component to
form a layer of phosphor on the optical component surface. The
mixture can be applied by painting the mixture onto the surface of
the optical component, spraying or other known deposition
techniques. When the phosphor is to be applied to a planar surface
the optical component is then advantageously spun or tape casting
to distribute the mixture uniformly over the surface to thereby
ensure a uniform thickness of phosphor forms.
[0041] Advantageously the method further comprises incorporating a
light diffusing material, for example titanium oxide, silica,
alumina in the phosphor mixture. Alternatively the light diffusing
material can be provided as a separate layer.
[0042] Advantageously, the phosphor comprises a photoluminescent
material having a formula A.sub.2SiO.sub.4:Eu.sup.2+D where A is a
divalent metal selected from the group comprising Sr, Ca, Ba, Mg,
Zn and Cd and D is a dopant selected from the group comprising F,
Cl, Br, I, P, S and N.
[0043] The method further comprises fabricating the optical
component from a plastics material or glass.
[0044] For ease of fabrication, and in accordance with a
particularly preferred method of the invention a plurality of
optical components in the form of an array, said array of optical
components having a common planar surface, and said phosphor is
deposited on the planar surface. Advantageously, the phosphor is
provided as a substantially uniform thickness layer on said planar
surface of the array of optical components.
[0045] In accordance with a further aspect of the invention there
is provided a phosphor material for coating an optical component of
an LED comprising a phosphor powder incorporated within an epoxy
resin, a silicone material or a polymer material. Advantageously
the phosphor material further incorporates a light diffusing
material.
[0046] In accordance with yet a further aspect of the invention
there is provided an optical component for a lighting arrangement
of a type comprising a radiation source configured to emit
radiation having a first wavelength range; a phosphor configured to
absorb at least a portion of said first wavelength range radiation
and emit radiation having a second wavelength range; and said
optical component being configured such that at least said first
wavelength range radiation passes through the optical component,
and characterized in that said phosphor is incorporated in said
optical component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a schematic representation of a known white LED as
already described;
[0048] FIGS. 2 to 7 are schematic representations of LED lighting
arrangements in accordance with the invention; and
[0049] FIG. 8 is a schematic representation of a method of
fabricating an optical component for an LED lighting arrangement in
accordance with the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0050] In order that the present invention is better understood,
embodiments of the invention will now be described by way of
example only with reference to the accompanying drawings.
[0051] Referring to FIG. 2 there is shown a LED lighting
arrangement 20 in accordance with the invention. The LED lighting
arrangement 20 is for generating light of a selected color for
example white light. The lighting arrangement comprises a LED chip
22, preferably a Gallium Nitride chip, which is operable to produce
light, radiation, preferably of wavelength in a range 300 to 500
nm. The LED chip 22 is mounted inside a stainless steel enclosure
or reflection cup 24 which has metallic silver deposited on its
inner surface to reflect light towards the output of the lighting
arrangement. A convex lens 26 is provided to focus light output
from the arrangement. In the example illustrated the lens 26 is
substantially hemispherical in form. The lens 26 can be made of a
plastics material such as polycarbonates or glass such as silica
based glass or any material substantially transparent to the
wavelengths of light generated by the LED chip 22.
[0052] In the embodiment in FIG. 2 the lens 26 has a planar,
substantially flat, surface 28 onto which there is provided a layer
of phosphor 30 before the lens is mounted to the enclosure 22. The
phosphor 30 preferably comprises a photoluminescent material having
a formula A.sub.2SiO.sub.4:Eu.sup.2+D where A is a divalent metal
selected from the group comprising Sr (Strontium), Ca (Calcium), Ba
(Barium), Mg (Magnesium), Zn (Zinc) and Cd (Cadmium) and D is a
dopant selected from the group comprising F (Fluorine), Cl
(Chlorine), Br (Bromine), I (Iodine), P (Phosphorous), S (Sulfur)
and N (Nitrogen) as disclosed in our co-pending patent application
U.S. 2006/0028122 the content of which is hereby incorporated by
way of reference thereto. The phosphor which is in the form of a
powder is mixed with an adhesive material such as epoxy or a
silicone resin, or a transparent polymer material and the mixture
is then applied to the surface of the lens to provide the phosphor
layer 30. The mixture can be applied by painting, dropping or
spraying or other deposition techniques which will be readily
apparent to those skilled in the art. Moreover the phosphor mixture
preferably further includes a light diffusing material such as
titanium oxide, silica or alumina to ensure a more uniform light
output.
[0053] The color of light emitted from the lighting arrangement can
be controlled by appropriate selection of the phosphor composition
as well as the thickness of the phosphor layer which will determine
the proportion of output light originating from the phosphor. To
ensure a uniform output color the phosphor layer is preferably of
uniform thickness and has a typical thickness in a range 20 to 500
.mu.m.
[0054] An advantage of the lighting arrangement of the invention is
that no phosphor need be incorporated within the encapsulation
materials in the LED package. Moreover the color of the light
output by the arrangement can be readily changed by providing a
different lens having an appropriate phosphor layer. This enables
large scale production of a common laser package. Moreover such a
lens provides direct color conversion in an LED lighting
arrangement.
[0055] Referring to FIG. 3 there is shown an LED lighting
arrangement in accordance with a further embodiment in which the
phosphor 30 is provided as a layer on the outer convex surface 32
of the lens 26. In this embodiment the lens 26 is dome shaped in
form.
[0056] FIG. 4 shows an LED lighting arrangement in accordance with
a further embodiment in which the lens 26 comprises a substantially
hemispherical shell and the phosphor 30 is provided on the inner
surface 34 of the lens 26. An advantage of providing the phosphor
on the inner surface is that the lens 26 then provides
environmental protection for the LED and phosphor. Alternatively
the phosphor can be applied as a layer of the outer surface of the
lens 26 (not shown).
[0057] FIG. 5 illustrates an LED arrangement in which the lens 26,
optical component, comprises a substantially spherical shell and
the phosphor 30 is deposited as a layer on at least a part of the
inner 36 or outer spherical 38 surfaces and the LED chip 22 is
mounted within the spherical shell. To ensure uniform emission of
radiation a plurality of LED chips are advantageously incorporated
in which the chip are oriented such that they each emit light in
differing directions. Such a form is preferred as a light source
for replacing existing incandescent light sources (light
bulbs).
[0058] Referring to FIG. 6 there is shown a further arrangement in
which the optical component 26 comprises a hollow cylindrical form
and the phosphor is applied to the inner 40 or outer 42 curved
surfaces. In such an arrangement the laser chip preferably
comprises a linear array of laser chips that are arranged along the
axis of the cylinder. Alternatively the lens 26 can comprise a
solid cylinder (not shown).
[0059] FIG. 7 shows an LED arrangement in which the optical
component comprise a solid substantially spherical lens 26 and the
phosphor is provided on at least a part of the spherical surface
44. In a preferred arrangement, as illustrated, the phosphor is
applied to only a portion of the surface, which surface is then
mounted within the volume defined by the enclosure. By mounting the
lens 26 in this way this provides environmental protection of the
phosphor 30.
[0060] Referring to FIG. 8 there is shown a preferred method of
fabricating lenses in accordance with the invention. An array of
lenses 46 is provided in which the lenses have a common planar
surface 48 onto which the phosphor 30 is provided. In the example
illustrated the lenses 36 are substantially hemispherical in form.
After the phosphor has been deposited the lenses can be separated
and mounted to the LED assemblies. Such a method is found to be
particularly advantageous for mass production of the optical
components.
[0061] It will be appreciated that the present invention is not
restricted to the specific embodiments described and that
modifications can be made which are within the scope of the
invention. For example although in the foregoing description
reference is made to a lens the phosphor can be deposited onto
other optical components such as for example a window through which
light passes though is not necessarily focused or directed or a
waveguide which guides, directs, light. Moreover the optical
component can have many forms which will be readily apparent to
those skilled in the art.
[0062] It will be appreciated that the phosphor and LED chip can be
selected depending on the intended application to provide light of
a desired color. It is also envisaged to provide two or more
phosphor materials to achieve the desired color, spectral content,
of emitted light. The different phosphors can be provided by mixing
the powdered material and incorporating them within a single layer
or alternatively by providing multiple layers of different
phosphors.
[0063] Examples of preferred phosphors are: [0064] YAG-based
phosphors which comprising a photoluminescent material having a
formula (YA).sub.3(AlB).sub.5(OC).sub.12:Ce.sup.3+ where A is a
trivalent metal selected from the group comprising Gd (Gadolinium),
Tb (Terbium), La (Lanthanum), Sm (Samarium) or divalent metal ions
such as Sr (Strontium), Ca (Calcium), Ba (Barium), Mg (Magnesium),
Zn (Zinc) and Cd (Cadmium), B comprising Si (Silicon), B (Boron), P
(phosphorous), and Ga (Gadolinium) and C is a dopant selected from
the group comprising F (Fluorine), Cl (Chlorine), Br (Bromine), I
(Iodine), P (phosphorous), S (Sulfur) and N (Nitrogen); [0065]
orange-red silicate-based phosphors of general formula
(SrM1).sub.3Si(OD).sub.5:Eu where M1 is selected from the group
comprising Ba, Ca, Mg, Zn . . . and D is selected from the group
comprising F, Cl, S, and N (such a phosphor can be used for
emitting light in a wavelength range from green to yellow (580 to
630 nm));
[0066] red silicon nitride based phosphors of general formula of
(SrM1)Si.sub.5N.sub.8 where M1 is selected from the group
comprising Sr, Ca, Mg, and Zn; [0067] red sulfate based phosphors
having a general formula (SrM1)S where M1 is selected from the
group comprising Ca, Ba, and Mg; and
[0068] green sulfate based phosphors having a general formula
(SrM1)(GaM2).sub.2S.sub.4:Eu where M1 is selected from the group
comprising Ca, Ba, and Mg, and where M2 is selected from the group
comprising Al and In.
[0069] In addition to providing an LED lighting arrangement the
invention further provides a novel optical component and method of
fabrication thereof.
[0070] In a further embodiment it is also envisaged to incorporate
the phosphor within material comprising the optical component.
Moreover the phosphor can be provided as a layer on the
encapsulating material.
* * * * *