U.S. patent application number 14/387312 was filed with the patent office on 2015-03-19 for led module, lighting device, and lamp.
This patent application is currently assigned to PANASONIC CORPORATION. The applicant listed for this patent is PANASONIC CORPORATION. Invention is credited to Toru Hirano, Hideaki Hyuga, Akifumi Nakamura, Masanori Suzuki, Kenichiro Tanaka, Yoji Urano, Teruhisa Yokota.
Application Number | 20150077982 14/387312 |
Document ID | / |
Family ID | 49672850 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150077982 |
Kind Code |
A1 |
Urano; Yoji ; et
al. |
March 19, 2015 |
LED MODULE, LIGHTING DEVICE, AND LAMP
Abstract
An LED module includes: an opaque substrate on which a wiring
circuit is provided; a submount bonded to a surface of the opaque
substrate with a first bond; an LED chip bonded with a second bond
to an opposite side of the submount from the opaque substrate; and
wires electrically connecting the LED chip to patterned wiring
circuit. In the LED module, the first bond and the second bond each
allow light emitted from the LED chip to pass therethrough. The
submount is a light-transmissive member. A lighting device includes
a device main body and the LED module. The lamp includes the LED
module.
Inventors: |
Urano; Yoji; (Osaka, JP)
; Tanaka; Kenichiro; (Osaka, JP) ; Nakamura;
Akifumi; (Osaka, JP) ; Hirano; Toru; (Osaka,
JP) ; Hyuga; Hideaki; (Osaka, JP) ; Suzuki;
Masanori; (Osaka, JP) ; Yokota; Teruhisa;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PANASONIC CORPORATION |
Osaka |
|
JP |
|
|
Assignee: |
PANASONIC CORPORATION
Osaka
JP
|
Family ID: |
49672850 |
Appl. No.: |
14/387312 |
Filed: |
May 24, 2013 |
PCT Filed: |
May 24, 2013 |
PCT NO: |
PCT/JP2013/003301 |
371 Date: |
September 23, 2014 |
Current U.S.
Class: |
362/217.14 ;
257/98; 362/382 |
Current CPC
Class: |
F21K 9/27 20160801; H01L
33/642 20130101; H01L 2224/48091 20130101; H01L 33/507 20130101;
H01L 2224/48091 20130101; H01L 2224/48137 20130101; H01L 25/0753
20130101; H01L 33/62 20130101; H01L 33/58 20130101; H01L 2224/48227
20130101; H01L 2224/45144 20130101; H01L 33/504 20130101; H01L
33/50 20130101; H01L 2224/45144 20130101; H01L 2224/8592 20130101;
H01L 33/486 20130101; H01L 33/60 20130101; H01L 2924/00014
20130101; H01L 2924/00012 20130101; H01L 2924/00 20130101; H01L
2224/73265 20130101; H01L 2933/0058 20130101; H01L 2924/181
20130101; H01L 2924/181 20130101 |
Class at
Publication: |
362/217.14 ;
257/98; 362/382 |
International
Class: |
H01L 33/48 20060101
H01L033/48; H01L 33/50 20060101 H01L033/50; F21K 99/00 20060101
F21K099/00; H01L 33/60 20060101 H01L033/60; H01L 33/64 20060101
H01L033/64; H01L 33/62 20060101 H01L033/62; H01L 33/58 20060101
H01L033/58 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2012 |
JP |
2012-125016 |
Aug 31, 2012 |
JP |
2012-191742 |
Nov 2, 2012 |
JP |
2012-242686 |
Claims
1-14. (canceled)
15. An LED module comprising: an opaque substrate on which a wiring
circuit is provided; a submount bonded to a surface of the opaque
substrate with a first bond; an LED chip bonded with a second bond
to an opposite side of the submount from the opaque substrate; and
wires electrically connecting the LED chip to the wiring circuit,
the first bond and the second bond each allowing light emitted from
the LED chip to pass therethrough, the submount being a
light-transmissive member, the LED chip including: a LED structure
portion including a n-type semiconductor layer, a light-emitting
layer, a p-type semiconductor layer; and a substrate being
transparent to light emitted from the light-emitting layer, the LED
structure portion provided on a main surface of the substrate, the
substrate being situated closer to the light-transmissive member
than the LED structure portion, the light-transmissive member
having a planar size greater than a planar size of the LED chip,
and the transparent member allowing parts of the light emitted from
the light-emitting layer of the LED chip towards the transparent
member to be diffused in the light-transmissive member and emerge
from the light-transmissive member through the face and/or side
faces.
16. The LED module according to claim 15, wherein: the submount has
light diffusing properties.
17. The LED module according to claim 15, wherein the submount has
a planar size larger than a planar size of the LED chip.
18. The LED module according to claim 15, wherein the surface of
the opaque substrate has light diffusing properties.
19. The LED module according to claim 15, wherein the surface of
the opaque substrate has specular reflective properties.
20. The LED module according to claim 15, wherein the opaque
substrate functions as a heat sink.
21. The LED module according to claim 15, wherein at least one of
the first bond and the second bond contains a first fluorescent
material which is excited by the light emitted from the LED chip to
emit light having a different color from the light emitted from the
chip.
22. The LED module according to claim 21, further comprising: a
color conversion portion made of a transparent material containing
a second fluorescent material which is excited by the light emitted
from the LED chip to emit light having a different color from the
light emitted from the LED chip, the color conversion portion
covering sides of the LED chip and an opposite surface of the LED
chip from the second bond.
23. The LED module according to claim 22, wherein the color
conversion portion contains a light diffusion material.
24. The LED module according to claim 21, further comprising a
resin portion which is situated over the face of the submount and
serves as an outer cover through which light passes last, the resin
portion being made of a transparent resin which contains a light
diffusion material.
25. The LED module according to claim 15, wherein the submount is
constituted by a plurality of light-transmissive layers which are
stacked in a thickness direction of the submount and have different
optical properties so that a light-transmissive layer of the
plurality of light-transmissive layers which is farther from the
LED chip is higher in reflectance in a wavelength range of the
light emitted from the LED chip.
26. The LED module according to claim 25, wherein each of the
plurality of light-transmissive layers is a ceramic layer.
27. A lighting device comprising: a device main body; and the LED
module according to claim 15 which is held on the device main
body.
28. A lamp comprising: a tube main body; and a light source that is
the LED module according to claim 15.
Description
TECHNICAL FIELD
[0001] The present invention relates to an LED module, a lighting
device, and a lamp.
BACKGROUND ART
[0002] Heretofore, a light emission apparatus 100 having a
configuration shown in FIG. 45 has been proposed (JP 2008-91831A:
Patent Document 1). The light emission apparatus 100 includes a
submount substrate 120 having a nitride-based ceramic substrate
121, an Au layer 124 provided on a surface of the nitride based
ceramic substrate 121, an oxide layer 123 interposed between the
nitride based ceramic substrate 121 and the Au layer 124, and an
LED light-emitting element 126 mounted on the submount substrate
120 via a solder layer 125. The oxide layer 123 includes a metal
oxide as a main component. The submount substrate 120 has a
reflecting layer 122 composed of at least one of Ag and Al that is
formed on the surface of the nitride-based ceramic substrate 121 so
as not to overlap the Au layer 124.
[0003] Patent Document 1 discloses that, for the purpose of
extracting light efficiently from the LED light-emitting element
126, it is preferable to use the nitride-based ceramic substrate
121 of aluminum nitride having high reflectance.
[0004] Also, heretofore, a chip-type light-emitting element having
a configuration shown in FIG. 46 has been proposed (JP 11-112025A:
Patent Document 2). The chip-type light-emitting element includes
an insulating substrate 201, an LED chip 206 that is mounted on a
surface of the insulating substrate 201, and a package 207 which
covers the LED chip 206 and surroundings thereof.
[0005] Patent Document 2 discloses that blue light propagating
toward the back face of the substrate of the LED chip 206 can be
reflected by the insulating substrate 201 that is a white
insulating substrate composed of ceramics such as alumina and
aluminum nitride.
[0006] Also, heretofore, as shown in FIG. 47, a configuration has
been proposed in which a light emission apparatus is mounted on an
external circuit substrate 301 (JP 2006-237557A: Patent Document
3). The light emission apparatus includes: a light-emitting element
housing package having a substrate 304 and a reflecting member 302;
and a light-emitting element 306 constituted by an LED chip mounted
on a mounting portion 304a of the substrate 304.
[0007] Patent Document 3 discloses that the substrate 304 and the
reflecting member 302 are preferably composed of white ceramics.
Also, Patent Document 3 discloses a lighting apparatus including
the above-mentioned light emission apparatus as a light source.
[0008] In the light emission apparatus 100 having the configuration
shown in FIG. 45, it is speculated that part of light emitted from
a light-emitting layer of the LED light-emitting element 126
propagates toward the nitride-based ceramic substrate 121 through
the LED light-emitting element 126 and is reflected by the solder
layer 125. However, in the light emission apparatus 100, it is
speculated that light outcoupling efficiency decreases due to
absorption, multiple reflection and the like of the light reflected
by the solder layer 125 in the LED light-emitting element 126.
[0009] In the chip-type light-emitting element having the
configuration shown in FIG. 46, blue light that propagates toward
the back face of the substrate of the LED chip 206 is reflected by
the insulating substrate 201. It is speculated that light
outcoupling efficiency decreases due to absorption, multiple
reflection and the like of the light in the LED chip 206.
[0010] In the configuration shown in FIG. 47, part of the light
emitted from a light-emitting layer of the light-emitting element
306 propagates toward the substrate 304 through the light-emitting
element 306, and is reflected by the substrate 304. It is
speculated that light outcoupling efficiency decreases due to
absorption, multiple reflection, and the like of the light in the
light-emitting element 306.
SUMMARY OF INVENTION
[0011] The present invention has been made in view of the
above-described insufficiencies, and an object of the present
invention is to provide an LED module, a lighting device, and a
lamp each having improved light outcoupling efficiency.
[0012] An LED module in accordance with the present invention
includes: an opaque substrate on which a wiring circuit is
provided; a submount bonded to a surface of the opaque substrate
with a first bond; an LED chip bonded with a second bond to a face
on an opposite side of the submount from the opaque substrate; and
wires electrically connecting the LED chip to the wiring circuit.
Each of the first bond and the second bond allows light emitted
from the LED chip to pass therethrough, and the submount is a
light-transmissive member.
[0013] In this LED module, the submount preferably has light
diffusing properties.
[0014] In this LED module, the submount preferably has a planar
size larger than a planar size of the LED chip.
[0015] In this LED module, the surface of the opaque substrate
preferably has light diffusing properties.
[0016] In this LED module, the surface of the opaque substrate
preferably has specular reflective properties.
[0017] In this LED module, the opaque substrate preferably
functions as a heat sink.
[0018] In this LED module, at least one of the first bond and the
second bond preferably contains a first fluorescent material which
is excited by the light emitted from the LED chip to emit light
having a different color from the light emitted from the LED
chip.
[0019] This LED module preferably includes a color conversion
portion made of a transparent material containing a second
fluorescent material which is excited by the light emitted from the
LED chip to emit light having a different color from the light
emitted from the LED chip, the color conversion portion covering
sides of the LED chip and an opposite surface of the LED chip from
the first bond.
[0020] In this LED module, the color conversion portion preferably
contains a light diffusion material.
[0021] This LED module preferably includes a resin portion which is
situated over the face of the submount and serves as an outer cover
through which light passes last, the resin portion being made of a
transparent resin which contains a light diffusion material.
[0022] In this LED module, the submount is preferably constituted
by a plurality of light-transmissive layers which are stacked in a
thickness direction of the submount and have different optical
properties so that a light-transmissive layer of the plurality of
light-transmissive layers which is farther from the LED chip is
higher in reflectance in a wavelength range of the light emitted
from the LED chip.
[0023] In this LED module, each of the plurality of
light-transmissive layers is a ceramic layer.
[0024] A lighting device in accordance with the present invention
includes a device main body; and the LED module which is held on
the device main body.
[0025] A lamp in accordance with the present invention includes a
light source that is the LED module.
[0026] The LED module in accordance with the present invention
includes: the first bond and the second bond each allowing the
light emitted from the LED chip to pass therethrough; and the
submount being the light-transmissive member, and therefore can
have improved light outcoupling efficiency.
[0027] The lighting device in accordance with the present invention
can have improved light outcoupling efficiency.
[0028] The lamp in accordance with the present invention can have
improved light outcoupling efficiency.
BRIEF DESCRIPTION OF DRAWINGS
[0029] FIG. I is a schematic cross-section of an LED module of
Embodiment 1;
[0030] FIG. 2 is a schematic explanatory diagram of a propagating
path of light in the LED module of Embodiment 1;
[0031] FIG. 3 is a schematic explanatory diagram of a propagating
path of light in the LED module of Embodiment 1;
[0032] FIG. 4 is a schematic explanatory diagram of a propagating
path of light in the LED module of Embodiment 1;
[0033] FIG. 5 is a schematic explanatory diagram of a propagating
path of light in the LED module of Embodiment 1;
[0034] FIG. 6 is a schematic cross-section illustrating the first
modification of the LED module of Embodiment 1;
[0035] FIG. 7 is a main portion schematic cross-section of the
second modification of the LED module of Embodiment 1;
[0036] FIG. 8 is a main portion schematic cross-section of the
third modification of the LED module of Embodiment 1;
[0037] FIG. 9 is a main portion schematic cross-section of an
exemplary configuration of the fourth modification of the LED
module of Embodiment 1;
[0038] FIG. 10 is a main portion schematic cross-section of the
fifth modification of the LED module of Embodiment 1;
[0039] FIG. 11 is a main portion schematic cross-section of the
sixth modification of the LED module of Embodiment 1;
[0040] FIG. 12 is a main portion schematic cross-section of the
seventh modification of the LED module of Embodiment 1;
[0041] FIG. 13 is an explanatory diagram of dimensional parameters
of a submount and an LED chip of the seventh modification of the
LED module of Embodiment 1;
[0042] FIG. 14A is a schematic perspective view illustrating
another exemplary configuration of the submount of the seventh
modification of the LED module of Embodiment 1;
[0043] FIG. 14B is an explanatory diagram of dimensional parameters
of the exemplary configuration of the submount of the seventh
modification of the LED module of Embodiment 1;
[0044] FIG. 15A is a schematic perspective view illustrating
another exemplary configuration of the submount of the seventh
modification of the LED module of Embodiment 1;
[0045] FIG. 15B is an explanatory diagram of dimensional parameters
of the exemplary configuration of the submount of the seventh
modification of the LED module of Embodiment 1;
[0046] FIG. 16 is a schematic cross-section illustrating the
submount and the LED chip of the seventh modification of the LED
module of Embodiment 1;
[0047] FIG. 17 is a main portion schematic cross-section of the
eighth modification of the LED module of Embodiment 1;
[0048] FIG. 18 is a main portion schematic cross-section of the
ninth modification of the LED module of Embodiment 1;
[0049] FIG. 19 is a main portion schematic cross-section of the
tenth modification of the LED module of Embodiment 1;
[0050] FIG. 20 is a schematic cross-section of an LED module of
Embodiment 2;
[0051] FIG. 21 is a perspective view of a submount of the LED
module of Embodiment 2;
[0052] FIG. 22 is a schematic explanatory diagram of a propagating
path of light in the LED module of Embodiment 2;
[0053] FIG. 23 is an explanatory diagram of the relation between a
particle diameter and reflectance of an alumina particle;
[0054] FIG. 24 is an explanatory diagram of a simulation result of
the relation between a thickness of a submount and light
outcoupling efficiency in an LED module of a comparative
example;
[0055] FIG. 25 is an explanatory diagram of a simulation result of
the relation between a planar size of the submount and a light
outputting amount of the LED module of the comparative example;
[0056] FIG. 26 is an explanatory diagram of an experimental result
of the relation between a thickness of the submount and light
outcoupling efficiency;
[0057] FIG. 27 is a reflectance-wavelength characteristic diagram
of a submount and an alumina substrate in Example 1 of Embodiment
2;
[0058] FIG. 28 is an explanatory diagram of an experimental result
of the relation between a particle diameter of an alumina particle
in a first ceramic layer and efficiency and color difference;
[0059] FIG. 29 is a schematic explanatory diagram of the submount
in the LED module of Embodiment 2;
[0060] FIG. 30 is an explanatory diagram of the relation between a
glass compounding ratio of the submount in the LED module of
Embodiment 2 and integrated intensity of an integrating sphere;
[0061] FIG. 31 is a reflectance-wavelength characteristic diagram
of the submount and an alumina substrate in Example 2 of Embodiment
2;
[0062] FIG. 32 is a schematic cross-section illustrating the first
modification of the LED module of Embodiment 2;
[0063] FIG. 33 is an inferred mechanism diagram for illustrating
the principle relating to improvement of light outcoupling
efficiency in the first modification of the LED module of
Embodiment 2;
[0064] FIGS. 34A to 34C are inferred mechanism diagrams for
illustrating the principle relating to improvement of light
outcoupling efficiency in the first modification of the LED module
of Embodiment 2;
[0065] FIG. 35 is a schematic perspective view of the second
modification of the LED module of Embodiment 2 with a partial
cutaway thereof;
[0066] FIG. 36 is a schematic perspective view of the third
modification of the LED module of Embodiment 2, which is partially
exploded;
[0067] FIG. 37 is a main portion schematic cross-section of the
fourth modification of the LED module of Embodiment 2;
[0068] FIG. 38A is a schematic cross-section of an LED module of
Embodiment 3;
[0069] FIG. 38B is a schematic cross-section taken along X-X in
FIG. 38A;
[0070] FIG. 38C is a schematic cross-section taken along Y-Y in
FIG. 38A;
[0071] FIG. 39 is a schematic perspective view of the modification
of the LED module of Embodiment 3 with a partial cutaway
thereof;
[0072] FIG. 40 is a schematic cross-section of the modification of
the LED module of Embodiment 3;
[0073] FIG. 41A is a schematic perspective view of a lighting
device of Embodiment 3, which is partially exploded;
[0074] FIG. 41B is a main portion enlarged view in FIG. 41A;
[0075] FIG. 42A is a schematic perspective view of a straight-tube
LED lamp of Embodiment 3, which is partially exploded;
[0076] FIG. 42B is a main portion enlarged view in FIG. 42A;
[0077] FIG. 43 is a schematic perspective view of another lighting
device of Embodiment 3;
[0078] FIG. 44 is a schematic perspective view of the lighting
device of Embodiment 3, which is partially exploded;
[0079] FIG. 45 is a cross section of a light emission apparatus of
a conventional example;
[0080] FIG. 46 is a perspective explanatory diagram of a chip-type
light-emitting element of another conventional example; and
[0081] FIG. 47 is a cross section of a configuration of yet another
conventional example.
DESCRIPTION OF EMBODIMENTS
Embodiment 1
[0082] Hereinafter, an LED module 1 of the present embodiment will
be described with reference to FIGS. 1 to 5.
[0083] The LED module 1 includes: an opaque substrate 2 on which
patterned conductors (patterned wiring circuit) 8 serving as a
wiring circuit is provided; a submount 4 bonded to a surface 2sa of
the opaque substrate 2 with a first bond 3; an LED chip 6 bonded
with a second bond 5 to a face 4sa on an opposite side of the
submount 4 from the opaque substrate 2; and wires 7 electrically
connecting the LED chip 6 to the patterned conductors 8,
respectively.
[0084] In the LED module 1, the first bond 3 and the second bond 5
allows light emitted from the LED chip 6 to pass therethrough, and
the submount 4 is a light-transmissive member. The
light-transmissive member propagates incident light to the outside
through refraction or internal diffusion (scattering).
[0085] Accordingly, in the LED module 1, part of the light emitted
from a light-emitting layer (not shown) in the LED chip 6 passes
through the LED chip 6 and the second bond 5, and thereafter is
diffused inside the submount 4. Consequently, the light that has
passed through the LED chip 6 and the second bond 5 is less likely
to be totally reflected, and more likely to emerge from the
submount 4 through either side faces 4sc or the face 4sa.
Therefore, in the LED module 1, light outcoupling efficiency can be
improved and a total light flux amount can be increased.
[0086] Hereinafter, each constituent element of the LED module 1
will be described in detail.
[0087] The LED chip 6 includes a first electrode (not shown)
serving as an anode electrode and a second electrode (not shown)
serving as a cathode electrode both on a face of the LED chip 6 in
the thickness direction.
[0088] The LED chip 6 includes, as shown in FIG. 2, a substrate 61
and an LED structure portion 60 on a main surface of the substrate
61. The LED structure portion 60 includes an n-type semiconductor
layer, a light-emitting layer, and a p-type semiconductor layer.
The stacking order of the n-type semiconductor layer, the
light-emitting layer, and the p-type semiconductor layer is the
n-type semiconductor layer, the light-emitting layer, and the
p-type semiconductor layer from the substrate 61. The stacking
order is not limited thereto, however, and the stacking order may
be the p-type semiconductor layer, the light-emitting layer, and
the n-type semiconductor layer from the substrate 61. The LED chip
6 more preferably has a structure in which a buffer layer is
provided between the LED structure portion 60 and the substrate 61.
The light-emitting layer preferably has a single quantum well
structure or a multiple quantum well structure, but is not limited
thereto. For example, the LED chip 6 may have a doublehetero
structure configured by the n-type semiconductor layer, the
light-emitting layer, and the p-type semiconductor layer. Note
that, the structure of the LED chip 6 is not particularly limited.
The LED module 1 may be an LED chip which includes a reflector such
as a Bragg reflector.
[0089] The LED chip 6 may be a GaN-based blue LED chip which emits
blue light, for example. In this case, the LED chip 6 includes a
sapphire substrate serving as the substrate 61. Note that, the
substrate 61 of the LED chip 6 is not limited to the sapphire
substrate, and the substrate 61 may be a transparent substrate with
respect to light that is emitted from the light-emitting layer.
[0090] The chip size of the LED chip 6 is not particularly limited.
The LED chip 6 may have a chip size of 0.3 mm sq. (0.3 mm by 0.3
mm), 0.45 mm sq. (0.45 mm by 0.45 mm), 1 mm sq. (1 mm by 1 mm), or
the like. Also, the planar shape of the LED chip 6 is not limited
to a square shape, and, for example, may be a rectangular shape.
When the planar shape of the LED chip 6 is a rectangular shape, the
chip size of the LED chip 6 may be 0.5 mm by 0.24 mm or the
like.
[0091] In the LED chip 6, the material and the emission color of
the light-emitting layer is not particularly limited. That is, the
LED chip 6 is not limited to a blue LED chip, and may be a violet
LED chip, an ultraviolet LED chip, a red LED chip, a green LED
chip, or the like.
[0092] The second bond 5 which bonds the LED chip 6 to the submount
4 may be formed of a transparent material such as a silicone resin,
an epoxy resin, and a hybrid material composed of a silicone resin
and an epoxy resin.
[0093] The light-transmissive member which is the submount 4 is
light-transmissive so as to transmit light in an ultraviolet
wavelength region and a visible wavelength region. As shown
schematically by arrows in FIG. 2, the light-transmissive member
transmits and diffuses light that is emitted from the
light-emitting layer of the LED structure portion 60 of the LED
chip 6. The light-transmissive member which is the submount 4 may
be formed of light-transmissive ceramics (such as alumina and
barium sulfate), for example. Properties of the light-transmissive
ceramics such as transmittance, reflectance, refractive index, and
thermal conductivity can be adjusted by the type and concentration
of a binder, an additive substance, or the like. In the LED module
1, the LED chip 6 is bonded to a center of the face 4sa of the
submount 4 with the second bond 5.
[0094] The submount 4 preferably has light diffusing properties.
Accordingly, in the LED module 1, as shown schematically by arrows
in FIG. 3, light emitted from the light-emitting layer of the LED
structure portion 60 of the LED chip 6 toward a further face of the
LED chip 6 in the thickness direction is diffused inside the
submount 4. Therefore, in the LED module 1, it is possible to
prevent light emitted toward the submount 4 from the LED chip 6
from returning to the LED chip 6 and therefore light can be more
easily extracted from the face 4sa and the side faces 4sc of the
submount 4. The light outcoupling efficiency of the LED module 1
can thereby be improved. Note that, in FIG. 3. broken-line arrows
schematically show propagating directions of rays of light that are
diffused inside the submount 4. Also, in FIG. 3, a solid-line arrow
schematically shows a propagating direction of a ray of light which
emerges from the submount 4 through the side face 4sc.
[0095] The submount 4 has a rectangular shape in a planar view, but
the shape thereof is not limited thereto, and may be a round shape,
a polygonal shape other than a rectangle, or the like. The planar
size of the submount 4 is set to be larger than the planar size of
the LED chip 6. Accordingly, light outcoupling efficiency of the
LED module 1 can be improved.
[0096] The submount 4 preferably has a stress alleviation function
of alleviating stress which acts on the LED chip 6 caused by the
difference between the linear expansion coefficients of the LED
chip 6 and the opaque substrate 2. The stress alleviation function
is provided by designing the submount 4 to have a linear expansion
coefficient close to that of the LED chip 6. Accordingly, in the
LED module 1, it is possible to alleviate the stress which acts on
the LED chip 6 caused by the difference between the linear
expansion coefficients of the LED chip 6 and the opaque substrate
2.
[0097] The submount 4 preferably has a heat conduction function of
conducting heat which is generated in the LED chip 6 toward the
opaque substrate 2. Also, the submount 4 preferably has a heat
conduction function of conducting heat which is generated in the
LED chip 6 to a region which is larger than the chip size of the
LED chip 6. Accordingly, in the LED module 1, heat generated in the
LED chip 6 can be efficiently dissipated via the submount 4 and the
opaque substrate 2.
[0098] The first bond 3 for bonding the submount 4 to the opaque
substrate 2 may be made of a transparent material such as a
silicone resin, an epoxy resin, and a hybrid material composed of a
silicone resin and an epoxy resin, for example. Alternatively, the
first bond 3 may be made of a conductive paste (such as silver
paste and gold paste) or a resin containing a filler (such as
titania and zinc oxide) or the like. When the first bond 3 is made
of the silver paste, it is preferable to surround the first bond 3
by a gas barrier layer composed of an adhesive having high gas
barrier properties or the like. When the opaque substrate 2 is
provided with a mask layer at the surface 2sa, the mask layer may
be used as the first bond 3.
[0099] The opaque substrate 2 is ideally an opaque medium
(non-transparent body) which does not transmit light in a visible
wavelength region, and is an non-transparent substrate which does
not transmit light in the visible wavelength region. The
transmittance of the opaque substrate 2 with respect to light in a
visible wavelength region is preferably 0% to 10%, more preferably
0 to 5%, and still more preferably 0 to 1%. Also, the opaque
substrate 2 ideally does not absorb light in the visible wavelength
region, and the absorptance thereof with respect to light in the
visible wavelength region is preferably 0% to 10%, more preferably
0 to 5%, and still more preferably 0 to 1%. The transmittance and
the absorptance are measured using an integrating sphere.
[0100] The opaque substrate 2 may be made of aluminum, an aluminum
alloy, silver, copper, phosphor bronze. a copper alloy (such as
alloy 42), a nickel alloy, or the like.
[0101] The opaque substrate 2 may be constituted by a base material
formed of the above-described material and a reflection layer (not
shown) provided on a surface of the base material, the reflection
layer having higher reflectance than the base material with respect
to light that is emitted from the LED chip 6. That is, the opaque
substrate 2 may include the reflection layer as a surface treatment
layer. The reflection layer may be formed of an Ag film, a stack of
an Ni film, a Pd film, and an Au film, a stack of an Ni film and an
Au film, a stack of an Ag film, a Pd film, and an Au--Ag alloy
film, or the like. The reflection layer formed of a metal material
preferably includes a plating layer or the like. In short, the
reflection layer formed of a metal material is preferably formed by
a plating method. Also, the reflection layer may be formed of, for
example, a white mask layer. The white mask for the mask layer may
be composed of a resin (such as silicone resin) that contains a
white pigment such as barium sulfate (BaSO.sub.4) and titanium
dioxide (TiO.sub.2). The white mask may be made of ASA COLOR
(registered trademark) RESIST INK available from Asahi Rubber Inc.,
which is a white mask material made of silicone, or the like. The
white mask layer may be formed by coating, for example.
[0102] The opaque substrate 2 may be a highly reflective substrate
including: an aluminum plate serving as the base material; an
aluminum film on a surface of the aluminum plate; and a reflection
enhancing film on the aluminum film. The aluminum film has higher
purity than the aluminum plate, and the reflection enhancing film
is constituted by two kinds of dielectric films having different
refractive indices. Here, the two kinds of dielectric films are
preferably an SiO.sub.2 film and a TiO.sub.2 film, for example. The
LED module 1 can have reflectance of 95% or more with respect to
visible light, due to using the highly reflective substrate as the
opaque substrate 2. The highly reflective substrate may be MIRO2 or
MIRO (registered trademark) available from Alanod, for example. The
aforementioned aluminum plate may be an aluminum plate having a
surface which has been subjected to an anodic oxidation
treatment.
[0103] Alternatively, the opaque substrate 2 may be an insulating
substrate formed of a material including a resin and a filler to
increase reflectance. This insulating substrate may be made of
unsaturated polyester and titania as the resin and the filler,
respectively, for example. The resin of the insulating substrate is
not limited to unsaturated polyester, and may be vinylester or the
like. Also, the filler is not limited to titania and may be
magnesium oxide, boron nitride, or aluminum hydroxide, for example.
The opaque substrate 2 may be a resin substrate composed of a white
resin, or a ceramic substrate having a reflection layer formed of a
white resin.
[0104] On the surface 2sa of the opaque substrate 2, the patterned
conductors 8 (hereinafter also referred to as "patterned circuit")
serving as a wiring circuit to supply power to the LED chip 6 is
provided. The electrodes (first electrode and second electrode) of
the LED chip 6 are electrically connected to the patterned
conductors 8 via wires 7 individually. The wire 7 may be a gold
wire, an aluminum wire, or the like, for example. The patterned
conductors 8 may be made of, for example, copper, phosphor bronze,
a copper alloy (such as 42 alloy), a nickel alloy, aluminum, an
aluminum alloy, or the like. The patterned conductors 8 may be
formed of a lead frame, a metal foil, a metal film, or the like.
When the opaque substrate 2 has electrical conductivity, an
insulation layer may be provided between the opaque substrate 2 and
the patterned conductors 8. Note that, in the LED module 1 of the
present embodiment, the opaque substrate 2 and the patterned
conductors 8 constitute a mounting substrate, and the LED chip 6 is
mounted on the mounting substrate with the submount 4 being
interposed therebetween.
[0105] The planar shape of the opaque substrate 2 is a rectangular
shape, but the planar shape is not limited thereto, and may be a
round shape, an elliptical shape, a triangular shape, a polygonal
shape other than a rectangle, or the like.
[0106] The number of LED chips 6 that are arranged on the surface
2sa of the opaque substrate 2 is not limited to one, and may be two
or more. The LED module 1 may be configured such that the planar
shape of the opaque substrate 2 is an elongated shape, and a
plurality of LED chips 6 are arranged along a longitudinal
direction of the opaque substrate 2, for example. In this case, the
patterned circuit 8 may be configured to be connected to the
plurality of LED chips 6 in series, in parallel, or in
series-parallel. In short, the LED module 1 may have a circuit
configuration in which a plurality of LED chips 6 are connected in
series, may have a circuit configuration in which a plurality of
LED chips 6 are connected in parallel, or may have a circuit
configuration in which a plurality of LED chips 6 are connected in
series-parallel.
[0107] In the LED module 1, the surface 2sa of the opaque substrate
2 preferably has light diffusing properties or specular reflective
properties.
[0108] When the surface 2sa of the opaque substrate 2 has light
diffusing properties, in the LED module 1, it is possible to
diffusely reflect light which is emitted from the light-emitting
layer of the LED structure portion 60 in the LED chip 6 and then
passes through the second bond 5, the submount 4, and the first
bond 3, by the surface 2sa of the opaque substrate 2, as shown
schematically by arrows in FIG. 4. As a result, light returning to
the LED chip 6 can be reduced. Note that, in FIG. 4, the
broken-line arrows schematically show propagating directions of
rays of light which strike the face 4sa of the submount 4 and are
diffusely reflected by the surface 2sa of the opaque substrate 2.
Also, in FIG. 4, the solid-line arrow schematically shows a
propagating direction of a ray of light which enters the submount 4
through the face 4sa and then emerges from the submount 4 through
the side face 4sc.
[0109] When the surface 2sa of the opaque substrate 2 has specular
reflective properties, in the LED module 1, it is possible to
specularly reflect light which is emitted from the LED chip 6, then
passes the second bond 5, the submount 4, and the first bond 3, and
thereafter obliquely enter the surface 2sa of the opaque substrate
2 as shown schematically by an arrow in FIG. 5. As a result, light
outcoupling efficiency of the side faces 4sc of the submount 4 can
be improved. Note that, in FIG. 5, the right arrow schematically
shows a propagating direction of a ray of light that strikes the
face 4sa of the submount 4 and is specularly reflected by the
surface 2sa of the opaque substrate 2. Also, in FIG. 5, the left
arrow schematically shows a propagating direction of a ray of light
that enters the submount 4 through the face 4sa and then emerges
from the submount 4 through the side face 4sc.
[0110] When the LED module 1 includes the opaque substrate 2 having
the surface 2sa with light diffusing properties or specular
reflective properties, light outcoupling efficiency thereof can be
further improved.
[0111] In the LED module 1, the opaque substrate 2 preferably
serves as a heat sink. In the LED module 1, when the opaque
substrate 2 is made of metal having high thermal conductivity such
as aluminum and copper, the opaque substrate 2 can function as a
heat sink. Accordingly, in the LED module 1, heat generated in the
LED chip 6 can be more efficiently dissipated, and as a result
light output can be increased. The heat dissipation property of the
LED module 1 can be improved without increasing the number of
parts, when the LED module 1 has a configuration in which a
plurality of fins 22 protruding from a further surface 2sb are
integrally provided on the further surface 2sb of the opaque
substrate 2 like the first modification shown in FIG. 6. The opaque
substrate 2 in which the plurality of fins 22 are integrally
provided can be formed by aluminum die-casting or the like.
[0112] Hereinafter, the second modification of the LED module 1 of
the present embodiment will be described with reference to FIG.
7.
[0113] The LED module 1 of the second modification differs from the
LED module 1 of Embodiment 1 in that each of the first bond 3 and
the second bond 5 is composed of a transparent material and a first
fluorescent material. The first fluorescent material is a
fluorescent material that is excited by the light emitted from the
LED chip 6 to emit light having a different color from a color of
the emitted light of the LED chip 6. In short, the LED module 1 of
the second modification differs from the LED module 1 of Embodiment
1 in that the first bond 3 and the second bond 5 contain the
fluorescent material that is excited by the light emitted from the
LED chip 6 to emit light having a different color from a color of
the emitted light of the LED chip 6. Note that, constituent
elements similar to those in Embodiment 1 are provided with the
same reference numerals, and redundant description thereof will be
omitted. Also, in FIG. 7. illustrations of the wires 7 and the
patterned conductors 8 shown in FIG. 1 are omitted.
[0114] The fluorescent material functions as a wavelength
conversion material that converts the light emitted from the LED
chip 6 to light with a longer wavelength than that of the light
from the LED chip 6. Accordingly, it is possible, using the LED
module 1, to obtain mixed-color light constituted by light that is
emitted from the LED chip 6 and light emitted from the fluorescent
material.
[0115] When including a blue LED chip as the LED chip 6 and a
yellow fluorescent material as the fluorescent material of the
wavelength conversion material for example, the LED module 1 can
emit white light. That is, in the LED module 1, blue light that is
emitted from the LED chip 6 and light that is emitted from the
yellow fluorescent material can pass through the LED chip 6 and the
submount 4, and as a result white light can be obtained. Note that,
FIG. 7 schematically illustrates propagating paths of light which
are emitted from the LED chip 6 and of light produced as a result
of wavelength conversion by the fluorescent material in the second
bond 5.
[0116] The fluorescent material serving as the wavelength
conversion material is not limited to the yellow fluorescent
material, and may include, for example, a set of a yellow
fluorescent material and a red fluorescent material, or a set of a
red fluorescent material and a green fluorescent material. Also,
the fluorescent material serving as the wavelength conversion
material is not limited to one kind of yellow fluorescent material,
and may include two kinds of yellow fluorescent materials having
different emission peak wavelengths. The color rendering property
of the LED module 1 can be improved by use of a plurality of
fluorescent materials as the wavelength conversion material.
[0117] In the LED module 1, at least one of the first bond 3 and
the second bond 5 may contain the second fluorescent material which
is excited by light emitted from LED chip 6 to emit light having a
different color from the emitted light of the LED chip 6.
Accordingly, the LED module 1 can produce mixed-color light
constituted by light emitted from the LED chip 6 and light emitted
from the fluorescent material.
[0118] In the LED module 1, when both the first bond 3 and the
second bond 5 contain the fluorescent materials, the fluorescent
material in the first bond 3 and the fluorescent material in the
second bond 5 may emit light rays having different wavelengths from
each other.
[0119] In this case, the fluorescent material in the second bond 5
that is closer to the LED chip 6 may be a fluorescent material that
emits light having a relatively long wavelength (such as red
fluorescent material) among two kinds of fluorescent materials, and
the fluorescent material in the first bond 3 that is farther from
the LED chip 6, may be a fluorescent material that emits light
having a relatively short wavelength (green fluorescent material).
Accordingly, in the LED module 1, it is possible to suppress
secondary absorption of light converted by the fluorescent material
in the second bond 5, by the fluorescent material in the first bond
3. The LED module 1 includes a combination of the red fluorescent
material and the green fluorescent material as the combination of
the two kinds of fluorescent materials. Even when the green
fluorescent material is a fluorescent material having poor
temperature characteristics (a fluorescent material in which
temperature quenching occurs frequently) compared with the red
fluorescent material, the green fluorescent material can be
arranged close to the opaque substrate 2 which functions as a heat
sink, and therefore, temperature increase of the green fluorescent
material can be suppressed, and as a result, the temperature
quenching of the green fluorescent material can be suppressed.
[0120] Furthermore, the LED module 1 may include a fluorescent
material to emit light having a relatively short wavelength (green
fluorescent material) as the fluorescent material in the second
bond 5 that is close to the LED chip 6, and a fluorescent material
to emit light having a relatively long wavelength (red fluorescent
material) as the fluorescent material in the first bond 3 that is
distant from the LED chip 6, for example, among two kinds of
fluorescent materials. Accordingly, in the LED module 1, it is
possible to suppress secondary absorption of light which has been
converted by the fluorescent material in the first bond 3, by the
fluorescent material in the second bond 5.
[0121] Note that, in the LED module 1 of the second modification,
the opaque substrate 2 preferably functions as a heat sink,
similarly to the LED module 1 of Embodiment 1.
[0122] Hereinafter, the third modification of the LED module 1 of
the present embodiment will be described with reference to FIG.
8.
[0123] The LED module 1 of the third modification differs from the
LED module 1 of Embodiment 1 in including a color conversion
portion 10 made of a transparent material containing a second
fluorescent material. The second fluorescent material is a
fluorescent material that is excited by the light emitted from the
LED chip 6 to emit light having a different color from a color of
the emitted light of the LED chip 6. Note that, constituent
elements similar to those in Embodiment 1 are provided with the
same reference numerals, and redundant description thereof will be
omitted. Also, in FIG. 8, illustrations of the wires 7 and the
patterned wiring circuit 8 shown in FIG. 1 are omitted.
[0124] The color conversion portion 10 is provided to cover side
faces of the LED chip 6 and an opposite surface of the LED chip 6
from the second bond 5. Accordingly, in the LED module 1, color
unevenness can be suppressed.
[0125] The transparent material for the color conversion portion 10
may be, for example, a silicone resin, an epoxy resin, an acrylic
resin, glass, or an organic/inorganic hybrid material in which an
organic component and an inorganic component are mixed and/or
combined at a nanometer (nm) level or molecular level.
[0126] The fluorescent material for the color conversion portion 10
functions as a wavelength conversion material that converts light
emitted from the LED chip 6 to light having longer wavelength than
the light emitted from the LED chip 6. Accordingly, the LED module
1 can emit mixed-color light constituted by light emitted from the
LED chip 6 and light emitted from the fluorescent material.
[0127] For example, when the LED chip 6 is a blue LED chip and the
fluorescent material of the wavelength conversion material is a
yellow fluorescent material, the LED module 1 can provide white
light. That is, blue light that is emitted from the LED chip 6 and
light that is emitted from the yellow fluorescent material can pass
through the LED chip 6 and the submount 4, and as a result the LED
module 1 can emit white light.
[0128] The fluorescent material serving as the wavelength
conversion material is not limited to the yellow fluorescent
material, and may include, for example, a set of a yellow
fluorescent material and a red fluorescent material, or a set of a
red fluorescent material and a green fluorescent material. Also,
the fluorescent material serving as the wavelength conversion
material is not limited to one kind of yellow fluorescent material,
and may include two kinds of yellow fluorescent materials having
different emission peak wavelengths. The color rendering property
of the LED module 1 can be improved by use of a plurality of
fluorescent materials as the wavelength conversion material.
[0129] In the LED module 1 of the present embodiment, the color
conversion portion 10 is in the form of a layer. The color
conversion portion 10 can be formed by a method such as molding and
screen-printing. In the LED module 1, the color conversion portion
10 is formed into a layer-form so as to be thin, and therefore it
is possible to reduce an amount of light which is to be converted
to heat by the fluorescent material in the color conversion portion
10. The color conversion portion 10 has a thin layer shape.
However, the shape of the color conversion portion 10 is not
limited to this, and may be hemisphere, semiellipse, semicylinder,
or the like.
[0130] The LED module 1 may be configured such that the color
conversion portion 10 contains a light diffusion material. The
light diffusion material is preferably composed of particles and
dispersed in the color conversion portion 10. In the LED module 1,
due to the color conversion portion 10 containing the light
diffusion material, color unevenness can be further suppressed. The
material of the light diffusion material may be an inorganic
material such as aluminum oxide, silica, titanium oxide, and Au, an
organic material such as a fluorine based resin, an organic and
inorganic hybrid material in which an organic component and an
inorganic component are mixed and/or combined at a nanometer level
or molecular level, or the like. In the LED module 1, the larger
the difference between the refractive indices of the light
diffusion material and the transparent material of the light
conversion portion 10, the smaller the required light diffusion
material content to obtain an effect to suppress color unevenness
to a similar level.
[0131] It is possible to further improve the color rendering
property of the LED module 1 by that the LED chip 6 is a blue LED
chip and the color conversion portion 10 contains a plurality of
fluorescent materials (green fluorescent material and red
fluorescent material) and the light diffusion material.
Furthermore, it is possible to further improve the color rendering
property of the LED module 1 by that the LED chip 6 is an
ultraviolet LED chip and the color conversion portion 10 contains a
plurality of kinds of fluorescent materials (blue fluorescent
material, green fluorescent material, and red fluorescent material)
and the light diffusion material.
[0132] The LED module 1 may be configured such that at least one of
the first bond 3 and the second bond 5 contains a first fluorescent
material, in addition to the color conversion portion 10. The first
fluorescent material is a fluorescent material which is excited by
light emitted from the LED chip 6 to emit light having a different
color from the emitted light of the LED chip 6. The LED module 1
may be configured such that the color conversion portion 10 is
provided so as to cover not only the LED chip 6 but also periphery
of the submount 4 (in the example in FIG. 9, the periphery of the
face 4sa and the side faces 4sc), like the fourth modification
shown in FIG. 9, for example. In FIG. 9, illustrations of the wires
7 and the patterned conductors 8 shown in FIG. 1 are omitted.
[0133] In a case of the fourth modification, a fluorescent material
in the color conversion portion 10 provided around the submount 4
is preferably a fluorescent material to emit light having a
relatively short wavelength compared with the fluorescent material
in the second bond 5. Accordingly, in the LED module 1, it is
possible to suppress re-absorption in the color conversion portion
10 provided around the submount 4.
[0134] Note that, in each of the LED modules 1 of the third
modification and the fourth modification, as with the LED module 1
of Embodiment 1, the opaque substrate 2 preferably functions as a
heat sink.
[0135] Hereinafter, the fifth modification of the LED module 1 of
the present embodiment will be described with reference to FIG.
10.
[0136] The LED module 1 of the fifth modification differs from the
LED module 1 of the third modification in including a resin portion
11 on the face 4sa of the submount 4. The resin portion 11
preferably serves as an outer cover through which light passes last
(in other words, an outer cover for extracting light). Note that,
constituent elements similar to those in the third modification are
provided with the same reference numerals, and redundant
description thereof will be omitted. Also, in FIG. 10,
illustrations of the wires 7 and the patterned conductors 8 shown
in FIG. 1 are omitted.
[0137] The resin portion 11 is preferably formed of a transparent
resin containing a light diffusion material. The transparent resin
is a silicone resin. The transparent resin is not limited to the
silicone resin, and may be an epoxy resin, an acrylic resin, or the
like. The material of the light diffusion material may be an
inorganic material such as aluminum oxide, silica, titanium oxide,
and Au, an organic material such as a fluorine based resin, or an
organic and inorganic hybrid material in which an organic component
and an inorganic component are mixed and/or combined at a nanometer
level or molecular level, or the like.
[0138] The resin portion 11 has a hemispherical shape, but the
shape is thereof not limited to the hemispherical shape, and may be
a hemispherical shape or a hemicylindrical shape.
[0139] The LED module 1 of the fifth modification includes the
resin portion 11, and therefore the reliability can be improved.
Also, the LED module 1 may be configured such that the resin
portion 11 contains the light diffusion material, as described
above. Accordingly, in the LED module 1, color unevenness can be
further suppressed. Also, when the color conversion portion 10
contains a plurality of kinds of fluorescent materials and the
resin portion 11 contains a light diffusion material, the color
rendering property of the LED module 1 can be further improved.
[0140] Note that, as with the LED module 1 of the Embodiment 1, the
opaque substrate 2 of the LED module 1 of the fifth modification
preferably functions as a heat sink.
[0141] Hereinafter, the sixth modification of the LED module 1 of
the present embodiment will be described with reference to FIG.
11.
[0142] The LED module 1 of the sixth modification differs from the
LED module 1 of the second modification in including a resin
portion 11 on the face 4sa of the submount 4. The resin portion 11
serves as an outer cover through which light is extracted. Note
that, constituent elements similar to those in the second
modification are provided with the same reference numerals, and
redundant description thereof will be omitted. Also, in FIG. 11,
illustrations of the wires 7 and the patterned conductors 8 shown
in FIG. 1 are omitted.
[0143] The resin portion 11 is preferably formed of a transparent
resin containing a light diffusion material. The transparent resin
is a silicone resin. However, the transparent resin is not limited
to the silicone resin, and may be an epoxy resin, an acrylic resin,
or the like. The material of the light diffusion material may be an
inorganic material such as aluminum oxide, silica, titanium oxide,
and Au, an organic material such as a fluorine based resin, or an
organic and inorganic hybrid material in which an organic component
and an inorganic component are mixed and/or combined at a nanometer
level or molecular level, or the like.
[0144] The resin portion 11 has a hemispherical shape, but the
shape of the resin portion 11 is not limited to the hemispherical
shape, and may be a hemiellipse spherical shape or a hemicylidrical
shape.
[0145] The LED module 1 of the sixth modification has improved
reliability due to the resin portion 11. Furthermore, the LED
module 1 may be configured such that the resin portion 11 contains
the light diffusion material, as described above. Accordingly, in
the LED module 1, color unevenness can be suppressed. Also, when
the LED module 1 is configured such that at least one of the first
bond 3 and the second bond 5 contains a plurality of kinds of
fluorescent materials (first fluorescent materials) and the resin
portion 11 contains the light diffusion material, the color
rendering property can be further improved.
[0146] Note that, as with the LED module 1 of Embodiment 1, the
opaque substrate 2 of the LED module 1 of the sixth modification
preferably functions as a heat sink.
[0147] Hereinafter, the seventh modification of the LED module 1 of
the present embodiment will be described with reference to FIGS. 12
to 16.
[0148] The LED module 1 of the seventh modification differs from
the LED module 1 of Embodiment 1 in including the color conversion
portion 10 containing a transparent material and a first
fluorescent material. The second fluorescent material is a
fluorescent material that is excited by the light emitted from the
LED chip 6 to emit light having a different color from the emitted
light of the LED chip 6. Note that, constituent elements similar to
those in Embodiment 1 are provided with the same reference
numerals, and redundant description thereof will be omitted. Also,
in FIG. 12, illustrations of the wires 7 and the patterned
conductors 8 shown in FIG. 1 are omitted.
[0149] The transparent material for the color conversion portion 10
may be, for example, a silicone resin, an epoxy resin, an acrylic
resin, glass, or an organic/inorganic hybrid material in which an
organic component and an inorganic component are mixed and/or
combined at a nanometer (nm) level or molecular level. The
fluorescent material for the color conversion portion 10 functions
as a wavelength conversion material that converts light emitted
from the LED chip 6 to light having longer wavelength than the
light emitted from the LED chip 6. Accordingly, the LED module 1
can emit mixed-color light constituted by light emitted from the
LED chip 6 and light emitted from the fluorescent material.
[0150] For example, when the LED chip 6 is a blue LED chip and the
fluorescent material of the wavelength conversion material is a
yellow fluorescent material, the LED module 1 can provide white
light. That is, blue light that is emitted from the LED chip 6 and
light that is emitted from the yellow fluorescent material can pass
through the LED chip 6 and the submount 4, and as a result the LED
module 1 can emit white light.
[0151] The fluorescent material serving as the wavelength
conversion material is not limited to the yellow fluorescent
material, and may include, for example, a set of a yellow
fluorescent material and a red fluorescent material, or a set of a
red fluorescent material and a green fluorescent material. Also,
the fluorescent material serving as the wavelength conversion
material is not limited to one kind of yellow fluorescent material,
and may include two kinds of yellow fluorescent materials having
different emission peak wavelengths. The color rendering property
of the LED module 1 can be improved by use of a plurality of
fluorescent materials as the wavelength conversion material.
[0152] The color conversion portion 10 has a hemispherical shape
and is formed on the surface 2sa of the opaque substrate 2 so as to
cover the first bond 3, the submount 4, the second bond 5, and the
LED chip 6.
[0153] In the LED module 1 of the seventh modification, some of
rays of the light produced in a light-emitting layer (not shown) in
the LED chip 6 and then passing through the LED chip 6 and the
second bond 5 are diffused in the submount 4. Consequently, the
light passing through the LED chip 6 and the second bond 5 is less
likely to be totally reflected, and more likely to be extracted
from the submount 4 through any one of the side faces 4sc and the
face 4sa. Therefore, in the LED module 1, light outcoupling
efficiency can be improved and a total light flux amount can be
increased. Moreover, in the LED module 1, by providing the surface
2sa of the opaque substrate 2 with diffuse reflective properties or
specular reflective properties, light emitted toward the opaque
substrate 2 from the color conversion portion 10 is likely to be
reflected by the opaque substrate 2, and thus light outcoupling
efficiency can be improved. In this case, in the LED module 1, some
of rays of light that are reflected by the opaque substrate 2 and
travel toward the color conversion portion 10 enter the color
conversion portion 10 again, and consequently, the conversion rate
at the color conversion portion 10 can be increased.
[0154] Incidentally, the inventors performed simulation in terms of
values of dimensional parameters of the submount 4, which are
effective to improve the light outcoupling efficiency of the LED
module 1. As a result, the inventors obtained knowledge that the
dimensional parameters preferably satisfy conditions defined by
Equations (1), (2), and (3) described later. The simulation is a
geometric optical simulation by Monte Carlo ray tracing.
[0155] For this simulation, dimensional parameters of the LED chip
6 and the submount 4 are defined as shown in FIG. 13. and a
dimensional parameter of the color conversion portion 10 is defined
as shown in FIG. 12.
[0156] With regard to the dimensional parameters of the LED chip 6,
a planar shape of the LED chip 6 is assumed to be rectangular, and
a lengthwise dimension of a side along the left and right direction
of FIG. 12 is denoted by Wc [mm], a lengthwise dimension of a side
along the direction perpendicular to the sheet of FIG. 12 is
denoted by Lc [min], and the thickness dimension is denote by Hc
[mm].
[0157] With regard to the dimensional parameters of the submount 4,
a planar shape of the submount 4 is assumed to be rectangular, and
a lengthwise dimension of a side along the left and right direction
in FIG. 12 is denoted by Ws [mm], a lengthwise dimension of a side
along the direction perpendicular to the sheet of FIG. 12 is
denoted by Ls [mm], and the thickness dimension is denoted by Hs
[mm].
[0158] With regard to the dimensional parameter of the color
conversion portion 10, the radius is denoted by R [mm].
[0159] In the simulation, the LED chip 6 is assumed to include the
substrate 61 made of sapphire having a refractive index of 1.77 and
the LED structure portion 60 made from GaN having a refractive
index of 2.5. Besides, the light-emitting layer is assumed to
isotropically emit light rays with the same intensity along all
directions from all the points of the light-emitting layer. The
first bond 3 and the second bond 5 are assumed to be made of
silicon resin with a refractive index of 1.41. Besides, regarding
physical properties of the submount 4, the structure of the
submount 4 is assumed to be a structural model where spherical
particles compounded in a base material composed of ceramics and
having different refractive index from that of the particles, and
the refractive index of the base member is supposed to be 1.77, the
refractive index of the particles is supposed to be 1.0, and a
filling rate of the particles is supposed to be 16.5%.
[0160] The above-mentioned Equations (1), (2), and (3) are as
follows.
2R>Ws>Wc+0.4 (1)
2R>Ls>Lc+0.4 (2)
Hs<(0.54/0.75)R-Hc (3)
[0161] The planar shape of the submount 4 is not limited to a
rectangular shape, and may be a polygonal shape other than the
rectangle or a round shape, for example. In a case where the
submount 4 is a regular hexagon, the above-described dimensional
parameters Ws and Ls each denote a dimension between two opposite
sides of the regular hexagon as shown in FIG. 14. Then, when the
requirements defined by the above-mentioned Equations (1), (2), and
(3) are satisfied, it is possible to improve the light-outcoupling
efficiency of the LED module 1.
[0162] Note that, the above-described simulation conditions are an
example, and are not particularly limited.
[0163] In the submount 4, as shown in FIG. 16, chamfers 41 may be
formed between the face 4sa and the side faces 4sc at a periphery
of the face 4sa. The chamfer 41 is a C chamfer with a chamfering
angle of 45.degree., but the chamfer is not limited thereto and may
be an R chamfer.
[0164] The color conversion portion 10 has a hemispherical shape,
but the shape thereof is not limited thereto, and may be a
hemiellipse spherical shape or a hemicylindrical shape.
[0165] Note that, as with the LED module 1 of Embodiment 1, the
opaque substrate 2 of the LED module 1 of the seventh modification
preferably functions as a heat sink. Also, in the LED module 1 of
the seventh modification, instead of the color conversion portion
10, an encapsulating portion composed of a transparent resin having
the same shape as the color conversion portion 10 may be
provided.
[0166] Hereinafter, the eighth modification of the LED module 1 of
the present embodiment will be described with reference to FIG.
17.
[0167] The LED module 1 of the eighth modification differs from the
LED module 1 of the seventh modification in terms of the shape of
the color conversion portion 10. Note that, constituent elements
similar to those in the seventh modification are provided with the
same reference numerals, and redundant description thereof will be
omitted. Also, in FIG. 17, illustrations of the wires 7 and the
patterned conductors 8 shown in FIG. 1 are omitted.
[0168] The color conversion portion 10 in the LED module 1 of the
eighth modification has a bombshell shape. The color conversion
portion 10 having the bombshell shape has a hemispherical portion
at the front end (the end that is distant from the opaque substrate
2) and a columnar portion at the back end (the end that is close to
the opaque substrate 2).
[0169] Incidentally, the inventors performed simulation in terms of
values of dimensional parameters of the submount 4, which are
effective to improve the light outcoupling efficiency of the LED
module 1. As a result, the inventors obtained knowledge that the
dimensional parameters preferably satisfy conditions defined by
Equations (4), (5), and (6) described later. The simulation
conditions for this simulation are substantially the same as the
simulation conditions described in the seventh modification, but
are different therefrom in the following points.
[0170] In the LED module 1 of the eighth modification, a
dimensional parameter of the color conversion portion 10 is defined
as shown in FIG. 17. That is, with regard to the dimensional
parameter of the color conversion portion 10, a radius of the
hemispherical portion is denoted by R [mm]. Besides, with regard to
the dimensional parameters of the submount 4, a dimension from the
face 4sa of the submount 4 to the center of the hemispherical
portion of the color conversion portion 10 is denoted by Hs'
[mm].
[0171] The above-mentioned Equations (4), (5), and (6) are as
follows.
2R>Ws>Wc+0.4 (4)
2R>Ls>Lc+0.4 (5)
Hs'<(0.54/0.75)R-Hc (6)
[0172] The planar shape of the submount 4 is not limited to a
rectangular shape, and may be a polygonal shape other than the
rectangle or a round shape, for example.
[0173] Note that, as with the LED module 1 of Embodiment 1, the
opaque substrate 2 of the LED module 1 of the eighth modification
preferably functions as a heat sink.
[0174] Hereinafter, the ninth modification of the LED module 1 of
the present embodiment will be described with reference to FIG.
18.
[0175] The LED module 1 of the ninth modification differs from the
LED module 1 of the seventh modification in that the color
conversion portion 10 is formed to have a semispherical shape on
the face 4sa of the submount 4. Note that, constituent elements
similar to those in the seventh modification are provided with the
same reference numerals, and redundant description thereof will be
omitted. Also, in FIG. 18, illustrations of the wires 7 and the
patterned conductors 8 shown in FIG. 1 are omitted.
[0176] Incidentally, the inventors performed simulation in terms of
values of dimensional parameters of the submount 4, which are
effective to improve the light outcoupling efficiency of the LED
module 1. As a result, the inventors obtained knowledge that the
dimensional parameters preferably satisfy conditions defined by
Equations (7), (8), and (9) described later. The simulation
conditions for this simulation are basically the same as the
simulation conditions described in the seventh modification. Note
that, the LED module 1 of the ninth modification is different from
the LED module 1 of the seventh modification in that, in the ninth
modification, the center of the color conversion portion 10 with a
hemispherical shape is present on the face 4sa of the submount 4
while, in the seventh modification, the center of the color
conversion portion 10 with a semispherical shape is situated on the
surface 2sa of the opaque substrate 2.
[0177] The above-mentioned Equations (7), (8), and (9) are as
follows.
Ws>2R>Wc+0.4 (7)
Ls>2R>Lc+0.4 (8)
Hs<(0.44/0.75)R-He (9)
[0178] The planar shape of the submount 4 is not limited to a
rectangular shape, and may be a polygonal shape other than the
rectangle or a round shape, for example.
[0179] Note that, as with the LED module 1 of Embodiment 1, the
opaque substrate 2 of the LED module 1 of the ninth modification
preferably functions as a heat sink.
[0180] Hereinafter, the tenth modification of the LED module 1 of
the present embodiment will be described with reference to FIG.
19.
[0181] The basic configuration of the LED module 1 of the tenth
modification is substantially the same as that of the LED module 1
of the ninth modification shown in FIG. 18, but differs therefrom
in that the opaque substrate 2 (refer to FIG. 18) is constituted by
a device main body of a lighting device (unshown) and the device
main body and the submount 4 are bonded with the first bond 3
(refer to FIG. 18). Note that, constituent elements similar to
those of the LED module 1 of the ninth modification are provided
with the same reference numerals, and redundant description thereof
will be omitted. Also, in FIG. 19, illustrations of the wires 7 and
the patterned conductors 8 shown in FIG. 1 are omitted.
[0182] Incidentally, the inventors performed simulation in terms of
values of dimensional parameters of the submount 4, which are
effective to improve the light outcoupling efficiency of the LED
module 1. As a result, the inventors obtained knowledge that the
dimensional parameters preferably satisfy conditions defined by
Equations (10), (11), and (12) described later. The simulation
conditions for this simulation are substantially the same as the
simulation conditions described in the ninth modification.
[0183] The above-mentioned Equations (10), (11), and (12) are as
follows.
Ws>2R>Wc+0.4 (10)
Ls>2R>Lc+0.4 (11)
Hs<(0.44/0.75)R-He (12)
[0184] The planar shape of the submount 4 is not limited to a
rectangular shape, and may be a polygonal shape other than the
rectangle or a round shape, for example.
[0185] Note that, as with the LED module 1 of Embodiment, the
opaque substrate 2 of the LED module 1 of the tenth modification
preferably functions as a heat sink.
[0186] Incidentally, not only the LED module 1 of the tenth
modification, but each of the LED modules 1 of Embodiment 1 and the
first modification to the ninth modification can be used as light
sources of various lighting apparatuses.
[0187] The lighting apparatus which includes the LED module 1 may
be, for example, a lighting device including a light source that is
the LED module 1 and is provided on a device main body. The
lighting device may include the device main body and the LED module
1 that is held on the device main body. In the lighting device
including the LED module 1, light outcoupling efficiency can be
improved.
[0188] The lighting apparatus which includes the LED module 1 may
be, for another example, a straight-tube LED lamp which is a type
of a lamp. The lamp may include a light source that is the LED
module 1. In the lamp including a light source that is the LED
module 1, light outcoupling efficiency can be improved. Note that,
in terms of the straight-tube LED lamp, "straight-tube LED lamp
system with L-type pin cap GX16t-5 (for general illumination)" (JEL
801:2010) is standardized by Japan Electric Lamp Manufacturers
Association, for example.
[0189] Such a straight-tube LED lamp may include: a tube main body
having a straight-tube shape and made of a light-transmissive
material (such as milky white glass and a milky white resin); and a
first cap and a second cap which are respectively provided at an
end and the other end of the tube main body in the longitudinal
direction. The LED module 1 is accommodated in the tube main body.
The opaque substrate 2 has an elongated shape, and a plurality of
LED chips 6 are aligned along the longitudinal direction of the
opaque substrate 2.
Embodiment 2
[0190] Hereinafter, an LED module 1 of the present embodiment will
be described with reference to FIGS. 20 to 22.
[0191] The LED module 1 of the present embodiment differs from the
LED module 1 of the seventh modification of Embodiment 1 in that
the submount 4 is constituted by two layers of ceramic layers 4a
and 4b which are stacked in the thickness direction. Note that,
constituent elements similar to those in the seventh modification
of Embodiment 1 are provided with the same reference numerals, and
redundant description thereof will be omitted.
[0192] In the submount 4, the ceramic layers 4a and 4b have
different optical properties from each other, and the ceramic layer
4a, which is farther from the LED chip 6, is higher in reflectance
with respect to light emitted from the LED chip 6. In this regard,
the optical properties refer to reflectance, transmittance,
absorptance, or the like. The submount 4 is required to be
constituted by at least two ceramic layers stacked in the thickness
direction, and have such a property that optical characteristics of
the ceramic layers are different from each other, and the further
the ceramic layer is from the LED chip 6, the higher the
reflectance thereof is with respect to the light emitted from the
LED chip 6.
[0193] Accordingly, in the LED module 1, light emitted from the
light-emitting layer of the LED structure portion 60 of the LED
chip 6 toward the further face of the LED chip 6 in the thickness
direction is more likely to be reflected at the interface between
the ceramic layer 4b and the ceramic layer 4a as shown
schematically by arrows in FIG. 22. Therefore, in the LED module 1,
it is possible to prevent light which is emitted from the LED chip
6 toward the submount 4 from returning to the LED chip 6 and to
prevent the light from entering, the surface 2sa of the opaque
substrate 2. As a result, light can be more easily extracted from
the face 4sa and the side faces 4sc of the submount 4.
Consequently, in the LED module 1, light outcoupling efficiency can
be improved. Moreover, it is possible to reduce the influence of
reflectance of the opaque substrate 2, and to increase the degree
of freedom in terms of the materials of the opaque substrate 2. For
example, in the LED module 1 of the seventh modification of
Embodiment 1, when the opaque substrate 2 includes an organic-based
substrate or a metal plate and a mask layer composed of a white
mask thereon, the reflectance of the opaque substrate 2 is prone to
decrease with time. Accordingly, there is a concern that the light
outcoupling efficiency may decrease with time greatly. In contrast,
in the LED module 1 of Embodiment 1, it is possible to reduce
influences of the reflectance of the opaque substrate 2 on the
light outcoupling efficiency, and therefore suppress deterioration
with time in the light outcoupling efficiency.
[0194] With regard to the submount 4, the uppermost ceramic layer
4b that is the closest to the LED chip 6 may be referred to as a
first ceramic layer 4b, and the lowermost ceramic layer 4a that is
the farthest from the LED chip 6 may be referred to as a second
ceramic layer 4a, for convenience of description.
[0195] The first ceramic layer 4b may be made of alumina
(Al.sub.2O.sub.3), for example. The first ceramic layer 4b may be
an alumina substrate, for example. When the first ceramic layer 4b
is the alumina substrate, the particle diameter of alumina
particles of the alumina substrate is preferably in a range between
1 .mu.m to 30 .mu.m. The larger the particle diameter of the
alumina particles, the smaller the reflectance of the first ceramic
layer 4b. The smaller the particle diameter of the alumina
particles, the larger the scattering effect of the first ceramic
layer 4b. In short, reducing the reflectance and increasing the
scattering effect are in a trade-off relationship.
[0196] The aforementioned particle diameter is determined by a
number-size distribution curve. Here, the number-size distribution
curve is obtained by measuring a particle size distribution by an
imaging method. Specifically, the particle diameter is determined
by a particle size (two-axis average diameter) and the number of
particles determined by image processing of a SEM image obtained by
scanning electron microscope (SEM) observation. In the number-size
distribution curve. the particle diameter value at the integrated
value of 50% is referred to as a median diameter (d.sub.50), and
the aforementioned particle diameter refers to the median
diameter.
[0197] Note that, FIG. 23 shows a theoretical relation between the
particle diameter and the reflectance of a spherical alumina
particle in the alumina substrate. The smaller the particle
diameter, the higher the reflectance. The relation of the first
ceramic layer 4b between the median diameter (d.sub.50) and the
measured value of reflectance is approximately the same as the
theoretical value shown in FIG. 23. The reflectance is measured
using a spectrophotometer and an integrating sphere.
[0198] The second ceramic layer 4a may be made of, for example, a
composite material that contains SiO.sub.2, Al.sub.2O.sub.3, a
material having a higher refractive index than Al.sub.2O.sub.3
(such as ZrO.sub.2 and TiO.sub.2), CaO, and BaO as components. In
the second ceramic layer 4a, the particle diameter of
Al.sub.2O.sub.3 particles is preferably in a range between 0.1
.mu.m to 1 .mu.m. The optical properties (such as reflectance,
transmittance, and absorptance) of the second ceramic layer 4a can
be adjusted by adjusting components, composition, particle
diameter, thickness, or the like of the composite material. In the
submount 4, when the first ceramic layer 4b and the second ceramic
layer 4a are made of the same kind of material, the first ceramic
layer 4b should be made of a material having the particle diameter
larger than that for the second ceramic layer 4a.
[0199] Incidentally, the inventors selected, as a comparative
example of the LED module 1 of the present embodiment, an LED
module including the submount 4 configured by a single layer of
alumina substrate. Then, the inventors performed a simulation
regarding light outcoupling efficiency of the comparative example
of the LED module with a parameter which is the dimension of the
submount 4 of the LED module of the comparative example. FIG. 24
shows an example of the results. The simulation is a geometric
optical simulation by Monte Carlo ray tracing. Note that, in the
simulation, the reflectance of the surface 2sa of the opaque
substrate 2 and the absorptance of the opaque substrate 2 are
assumed to be 95% and 5%, respectively. Also, in the simulation,
the chip size of the LED chip 6 is assumed to be 0.5 mm by 0.24
mm.
[0200] In FIG. 24, the horizontal axis represents a thickness of
the submount 4, and the vertical axis represents light outcoupling
efficiency. A curve denoted by "B1" in the diagram shows a case
where the planar size of the submount 4 is 1 mm sq. (1 mm by 1 mm),
and a curve denoted by "B2" in the diagram shows a case where the
planar size of the submount 4 is 2 mm sq. (2 mm by 2 mm). From FIG.
24, it is inferred that, when the thickness of the submount 4 is 2
mm or less, the light outcoupling efficiency decreases due to light
absorption by the opaque substrate 2, regardless of the planar size
of the submount 4.
[0201] Also, FIG. 24 teaches that, when the thickness of the
submount 4 is 2 mm or less, the light outcoupling efficiency is
higher with a decrease in the planar size of the submount 4.
[0202] Besides, the inventors simulated a ratio between light
emission amounts from the faces of the LED module, regarding the
LED modules of the comparative examples each including the submount
4 constituted by the alumina substrate only. The submounts had the
same thickness of 0.4 mm, and the planar sizes of 1 mm sq. and 2 mm
sq., respectively. FIG. 25 shows an example of the results. This
simulation is a geometric optical simulation by Monte Carlo ray
tracing. Note that, in the simulation, the reflectance of the
surface 2sa of the opaque substrate 2 and the absorptance of the
opaque substrate 2 are assumed to be 95% and 5%, respectively.
Also, in the simulation, the chip size of the LED chip 6 is assumed
to be 0.5 mm by 0.24 mm. Also, in the simulation, only a Fresnel
loss is assumed to occur at the side faces of the LED chip 6.
[0203] Reference sign "I1" in FIG. 25 denotes a ratio of the
outputted light amount directly from the LED chip 6. Reference sign
"I2" in FIG. 25 denotes a ratio of the outputted light amount from
an exposed surface (exposed portion of the face 4sa of the submount
4) of the submount 4 at the side of the LED chip 6. Reference sign
13'' in FIG. 25 denotes a ratio of the outputted light amount from
the side faces 4sc of the submount 4.
[0204] From the results in FIGS. 24 and 25, the inventors obtained
knowledge that the smaller the planar size of the submount 4, the
higher the ratio of the outputted light amount from the side faces
4sc of the submount 4, and as a result the light outcoupling
efficiency can be improved.
[0205] Moreover, the inventors investigated a relation between the
thickness of the submount 4 and the light flux emitted by the LED
module 1 with respect to various opaque substrates 2 in condition
that a planar size of the submount is 2 mm sq. (2 mm by 2 mm). The
light flux is measured by an integrating sphere. As the result, the
inventors obtained an experimental result shown in FIG. 26. In the
experiment, as the LED chip 6, adopted was a blue LED chip in which
the substrate was a sapphire substrate and the emission peak
wavelength from the light-emitting layer was 460 nm. The chip size
of the LED chip 6 was 0.5 mm by 0.24 mm. The color conversion
portion 10 was composed of a silicone resin containing a yellow
fluorescent material. The white circles (.largecircle.) in line C1
in FIG. 26 denote measured values of light flux with respect to an
LED module of Reference Model 1. In the LED module of Reference
Model 1, the submount 4 was an alumina substrate, and the opaque
substrate 2 was a silver substrate having reflectance of 98% with
respect to light with a wavelength of 460 nm. The white triangles
(.DELTA.) in line C2 in FIG. 26 designate measured values of light
flux with respect to an LED module of Reference Model 2. In the LED
module of Reference Model 2, the submount 4 was an alumina
substrate, and the opaque substrate 2 was a substrate including a
copper substrate and a reflection layer composed of a white mask
having reflectance of 92% with respect to light with a wavelength
of 460 nm on a surface of the copper substrate. The white rhombuses
(.diamond.) in line C3 in FIG. 26 designate measured values of
light flux with respect to an LED module of Reference Model 3. In
the LED module of Reference Model 3, the submount 4 was an alumina
substrate, and the opaque substrate 2 was an aluminum substrate
having reflectance of 95% with respect to light with a wavelength
of 460 nm.
[0206] From values denoted by reference signs C1, C2, and C3 in
FIG. 26, it is inferred that the light outcoupling efficiency of
the LED module 1 of the present embodiment can be improved by
increasing the thickness of the submount 4. Also, in the LED module
1 of the present embodiment, it is speculated that the light
outcoupling efficiency can be improved by using a silver substrate
as the opaque substrate 2 similarly to Reference Model 1.
[0207] On the other hand, from a viewpoint of efficiently
dissipating heat generated in the LED chip 6 to the further surface
of the opaque substrate 2 (that is, from a viewpoint of improving
the heat dissipation property), it is preferable that the submount
4 is thinner. In short, the light outcoupling efficiency and the
heat dissipation property are in a trade-off relationship.
[0208] Moreover, the inventors fabricated an LED module having a
reference structure in which the submount 4 was not provided and a
high purity alumina substrate was used as the opaque substrate 2,
and performed an experiment of measuring a light flux emitted by
the LED module having the reference structure. The black square
(.box-solid.) in FIG. 26 designates measured values of light flux
with respect to the LED module having the reference structure. The
inventors obtained an experimental result that, the LED module of
aforementioned Reference Model 1 is required to include the
submount 4 having the thickness of 0.4 mm or more to emit greater
light flux than the LED module having the reference structure.
Therefore, the inventors considered that it is preferable to adjust
the thickness of the submount 4 to an approximate range of 0.4 mm
to 0.5 mm, in view of the light outcoupling efficiency and the heat
dissipation property. Note that, with regard to the alumina
substrate used in the LED module having the reference structure,
the thickness of the alumina substrate is 1 mm, the particle
diameter of particles constituting the alumina substrate is 1
.mu.m. and the reflectance of the alumina substrate is 91%.
[0209] In the LED module of Reference Model 1 in which the silver
substrate was used as the opaque substrate 2, there is concern that
the reflectance may decrease due to sulfurization of the silver
substrate. In the LED module of Reference Model 2 in which the
reflection layer composed of the white mask is used, there is
concern that the reflectance may decrease due to thermal
degradation of the white mask.
[0210] Accordingly, in the LED module 1 of the present embodiment,
the opaque substrate 2 includes a base material (cupper substrate)
made of cupper and a reflection layer composed of the white mask
layer provided on a surface of the base material, and the submount
4 is the light-transmissive member having a configuration in which
the second ceramic layer 4a and the first ceramic layer 4b are
stacked in the thickness direction.
[0211] The inventors performed an experiment of measuring light
flux emitted by Example 1 of the LED module 1 of the present
embodiment. In Example 1, the submount 4 had the thickness of 0.5
mm, the second ceramic layer 4a had the thickness Hsa (refer to
FIG. 21) of 0.1 mm and the reflectance of 96% to light with a
wavelength of 450 nm, and the first ceramic layer 4b had the
thickness Hsb (refer to FIG. 21) of 0.4 mm and the reflectance of
80% to light with a wavelength of 450 nm. The black circle ( ) in
FIG. 26 designates a measured value of light flux with respect to
Example 1. FIG. 26 teaches that the LED module 1 of Example 1 emits
a greater light flux than the LED module having the reference
structure. Also, from FIG. 26, it is speculated that the LED module
1 of Example 1 emits a greater light flux than those of Reference
Models 1, 2, and 3 in which the submount 4 has the thickness of 0.5
mm.
[0212] Note that, reflectance-wavelength characteristics of the
submount 4 in Example 1 are as shown by a curve denoted by
reference sign A1 in FIG. 27, and reflectance-wavelength
characteristics of a single layer alumina substrate with a
thickness of 0.4 mm are as shown by a curve denoted by reference
sign A2 in FIG. 27. Note that the alumina substrate has the same
specification as those of the alumina substrates in Reference
Models 1, 2, and 3. The reflectance-wavelength characteristics
shown in FIG. 27 were measured using a spectrophotometer and an
integrating sphere.
[0213] Moreover, the inventors performed an experiment to measure
light flux and chromaticity of light emitted from the LED module 1.
In the experiment, the measurement was made for each of the
different particle diameters (median diameter) of the alumina
particle in the first ceramic layer 4b. In the experiment, the LED
chip 6 was a blue LED chip in which the substrate was a sapphire
substrate and the emission peak wavelength from the light-emitting
layer was 460 nm. The chip size of the LED chip 6 was 0.5 mm by
0.24 mm. The thickness and the planar size of the submount 4 were
0.49 mm and 2 mm sq. (2 mm by 2 mm), respectively.
[0214] The chromaticity is a psychophysical property of color that
is determined by chromaticity coordinates in an xy chromaticity
diagram of a CIE color system. The chromaticity was measured in a
direction in which the radiation angle of light emitted from the
LED module 1 is 0.degree. (light axis direction), and in a
direction in which the radiation angle is 60.degree. (direction in
which the angle relative to the light axis is 60.degree.). In the
measurement of the chromaticity, a spectral distribution in each of
the radiation angles was obtained by a spectrophotometer, and the
chromaticity in the CIE color system was calculated from each of
the spectral distribution.
[0215] The experimental results are summarized in FIG. 28. The
horizontal axis in FIG. 28 indicates a particle diameter. The left
vertical axis in FIG. 28 indicates efficiency calculated by a light
flux and input power supplied to the LED module 1. The right
vertical axis in FIG. 28 indicates a color difference. The color
difference is defined as the value of x (hereinafter referred to as
"x.sub.1") in the direction in which the radiation angle is
60.degree. in the chromaticity coordinates, when a value of x
(hereinafter referred to as "x.sub.0") in the direction in which
the radiation angle is 0.degree. in the chromaticity coordinates is
set as a reference. That is, the color difference in the right
vertical axis in FIG. 28 is a value of (x.sub.1-x.sub.0). When the
value of (x.sub.1-x.sub.0) is positive, it means that the larger
the absolute value thereof, the larger the shift of the
chromaticity to the yellowish-white side. When the value of
(x.sub.1-x.sub.0) is negative, it means that the larger the
absolute value thereof, the larger the shift of the chromaticity to
the blue-white side. Note that the design value of the chromaticity
in the LED module 1 is (0.33, 0.33). That is, the design value of x
in the chromaticity coordinates is 0.33. The design value of the
chromaticity is an example, and is not limited thereto.
[0216] The black rhombuses (.diamond-solid.) in FIG. 28 designate
measured values of the efficiency of the LED module 1. The black
squares (.box-solid.) in FIG. 28 designate measured values of the
color difference of the LED module 1. The white rhombus (.diamond.)
in FIG. 28 designates a measured value of the efficiency of the
aforementioned LED module having the reference structure. The white
square (.quadrature.) in FIG. 28 designates a measured value of the
color difference of the aforementioned LED module having the
reference structure. Note that, since the LED module having the
reference structure does not include the submount 4, the particle
diameter in the horizontal axis in FIG. 28 shows a particle
diameter of particles in the alumina substrate.
[0217] The allowable range of the color difference in the LED
module 1 is preferably in a range between -0.0015 to 0.0015, for
example, from a viewpoint of suppressing color unevenness and a
viewpoint of realizing a color difference similar to the color
difference of the LED module having the reference structure or
less.
[0218] FIG. 28 teaches that the LED module 1 has higher efficiency
than the LED module having the reference structure. Also, from FIG.
28, it is inferred that the efficiency of the LED module 1 can be
increased compared with that of the LED module having the reference
structure by setting the particle diameter in a range between 1
.mu.m to 4 .mu.m, while suppressing the color difference from
exceeding the allowable range (in other words, becoming larger than
the color difference of the LED module having the reference
structure).
[0219] The first ceramic layer 4b is a first dense layer composed
of ceramics sintered at a high temperature in an approximate range
of 1500.degree. C. to 1600.degree. C. The first ceramic layer 4b
has good rigidity compared with the second ceramic layer 4a, since
ceramic particles are bound strongly to each other by the high
temperature sintering. Here, the good rigidity indicates that a
flexural strength is relatively high. As a material of the first
ceramic layer 4b, alumina is preferable.
[0220] The second ceramic layer 4a is composed of ceramics sintered
at 1000.degree. C. or less (850.degree. C. to 1000.degree. C., for
example) which is a relatively low temperature compared with the
sintering temperature of the first ceramic layer 4b. The ceramics
constituting the second ceramic layer 4a may be a second dense
layer which contains a ceramic filler (ceramic microparticles) and
a glass component, or a porous layer containing a ceramic filler
(ceramic microparticles) and a glass component, for example.
[0221] The second dense layer is composed of dense ceramics in
which ceramic fillers are bound each other by sintering and glass
components are arranged around the ceramic fillers as a matrix. In
the second dense layer, the ceramic filler mainly performs a
function of reflecting light. The second dense layer may be made of
borosilicate glass, glass ceramics which contains lead borosilicate
glass and alumina, a material in which a ceramic filler is mixed to
glass ceramics which contains soda-lime glass and alumina, or the
like. The glass content of the glass ceramics is preferably set in
a range of around 35 to 60 wt %. The ceramics content of the glass
ceramics is preferably set in a range of around 40 to 60 wt %. Note
that, in the second dense layer, the zinc component of the lead
borosilicate glass can be substituted for titanium oxide or
tantalum oxide to increase refractive index of the glass ceramics.
The ceramic filler is preferably made of a material having higher
refractive index than glass ceramics, and may be, for example,
tantalum pentoxide, niobium pentoxide, titanium oxide, barium
oxide, barium sulfate, magnesium oxide, calcium oxide, strontium
oxide, zinc oxide, zirconium oxide, or silicate oxide (zircon).
[0222] When the second ceramic layer 4a is constituted by a porous
layer (hereinafter, "second ceramic layer 4a" is also referred to
as "porous layer 4a"), it is preferable that a first glass layer
40aa is interposed between a porous layer 4a having a plurality of
pores 40c and the first ceramic layer 4b, and a second glass layer
40ab is formed on an opposite side of the porous layer 4a from the
first ceramic layer 4b, as shown in the schematic diagram in FIG.
15. The porosity of the porous layer 4a is set to be around 40%,
but is not limited thereto. The first glass layer 40aa and the
second glass layer 40ab are transparent layers composed of a glass
component and transmit visible light. The thicknesses of the first
glass layer 40aa and the second glass layer 40ab may be set to
around 10 .mu.m, for example, but are not limited thereto. Around
half of the glass component of each of the first glass layer 40aa
and the second glass layer 40ab is composed of SiO.sub.2, but the
glass component is not limited thereto.
[0223] The first glass layer 40aa is provided so as to be
interposed between the porous layer 4a and the first ceramic layer
4b, and is closely-attached to the surface of the porous layer 4a
and to the surface of the first ceramic layer 4b by sintering at
the time of manufacture.
[0224] The second glass layer 40ab is provided on the opposite face
of the porous layer 4a from the first ceramic layer 4b, and
protects the porous layer 4a. Accordingly, pores 40c that exist on
the opposite surface of the porous layer 4a from the first ceramic
layer 4b is enclosed by the second glass layer 40ab.
[0225] The porous layer 4a contains a ceramic filler (ceramic
particulate) and a glass component. In the porous layer 4a. the
ceramic fillers are combined to form clusters by sintering so as to
form a porous structure. The glass component serves as a binder for
the ceramic filler. In the porous layer 4a, the ceramic filler and
the plurality of pores mainly perform a function of reflecting
light. Note that, the porous layer 4a can be formed in accordance
with a manufacturing process of a package disclosed in paragraphs
[0023]-[0026] and in FIG. 4 in WO2012/039442 A1.
[0226] The reflectance of the porous layer 4a can be changed by,
for example, changing a weight ratio between the glass component
and the ceramic component (such as alumina and zirconia). That is,
the reflectance of the porous layer 4a can be changed by changing
the glass compounding ratio. In FIG. 30, the horizontal axis
indicates a glass compounding ratio, and the vertical axis
indicates an integrated intensity measured with an integrating
sphere. In measurement with the integrating sphere, intensities of
reflected light with wavelengths between 380 to 780 nm are
integrated. FIG. 30 teaches that the reflectance can be increased
with a decrease in the glass compounding ratio.
[0227] Accordingly, in Example 2, the first ceramic layer 4b is
formed by sintering alumina at 1600.degree. C., and the porous
layer 4a is formed by sintering materials at 850.degree. C., the
materials being compounded such that the weight ratio of the glass
component to the ceramic component is 20:80. In Example 2, the
glass component is borosilicate glass with a median diameter of
around 3 .mu.m, and the alumina is a compound of alumina with a
median diameter of around 0.5 .mu.m and alumina with a median
diameter of around 2 .mu.m, and the zirconia has a median diameter
of around 0.2 .mu.m. In Example 2, the first ceramic layer 4b has
the thickness of 0.38 mm, and the porous layer 4a has the thickness
of 0.10 mm. The reflectance-wavelength characteristics of the
submount 4 in Example 2 is indicated by a curve designated by "A3"
in FIG. 31 and the reflectance-wavelength characteristics of the
single layer alumina substrate with a thickness of 0.38 mm is as
shown by a curve designated by "A4" in FIG. 31. Note that, the
weight ratio of the glass component to the ceramic component in the
porous layer 4a and the particle diameters (median diameters) of
the respective materials are not particularly limited.
[0228] The porous layer 4a has a graded composition in which the
density of the glass component gradually decreases from the both
sides thereof to the inside in the thickness direction, since the
glass components of the first glass layer 40aa and the second glass
layer 40ab infiltrate at the time of manufacture.
[0229] Specifically, as the result of observing a cross-section
along the thickness direction of the porous layer 4a with a
thickness of around 100 .mu.m with a microscope, it was found out
that in regions from respective faces of the porous layer 4a to the
depth of around 20 .mu.m in the thickness direction, glass dense
layers exist in which glass occupies 70% or more of the area per
unit area. In contrast to this, in the internal region deeper than
20 .mu.m from respective faces of the porous layer 4a in the
thickness direction, glass occupies around 20% of the area per unit
area, and a non-dense layer exists in which the glass and the
ceramic filler are mixed at a certain ratio.
[0230] In the LED module 1 of the present embodiment, the submount
4 is constituted by the two ceramic layers 4a and 4b, and optical
properties of these two ceramic layers 4a and 4b differ from each
other, and the ceramic layer 4a which is further from the LED chip
6 has a higher reflectance with respect to light emitted from the
LED chip 6 than the ceramic layer 4b that is closer to the LED chip
6. Accordingly, light outcoupling efficiency of the LED module 1 of
the present embodiment can be improved compared with that of a LED
module including the submount 4 which is constituted by a single
layer alumina substrate. In the LED module 1 of the present
embodiment, it is possible to reduce an amount of light reflected
from the face 4sa of the submount 4, and as a result, absorption
loss in the LED chip 6 can be reduced. Furthermore, in the LED
module 1 of the present embodiment, absorptance of light
(approximately 0%) of the submount 4 can be smaller than the
absorptance of light (around 2 to 8%, for example) of the opaque
substrate 2, and parts of light incident on the face 4sa of the
submount 4 can be scattered in the ceramic layer 4b and can be
reflected at the interface between the ceramic layer 4b and the
ceramic layer 4a. Consequently, in the LED module 1, it is possible
to reduce an amount of light which passes through the submount 4
and arrives at the surface 2sa of the opaque substrate 2 and
absorption loss at the opaque substrate 2. As a result, light
outcoupling efficiency can be improved.
[0231] Incidentally, in the LED module 1 of the present embodiment,
the first ceramic layer 4b has relatively higher light
transmittance, and the second ceramic layer 4a has relatively
higher light scattering rate, out of the first ceramic layer 4b and
the second ceramic layer 4a. Accordingly, it is inferred that, in
the LED module 1, light can be diffused in the second ceramic layer
4a that is farther from the LED chip 6, and an amount of light that
is diffused before arriving at the opaque substrate 2 increases
compared with a LED module having only the first ceramic layer 4b.
Also, it is speculated that, in the LED module 1, the possibility
that light reflected by the opaque substrate 2 directly below the
submount 4 is diffused without returning to the LED chip 6 can be
increased. In contrast, it is speculated that, in the LED module 1,
when the submount 4 is constituted by only the second ceramic layer
4a, the possibility that light is scattered in the vicinity of the
LED chip 6 and then returns to the LED chip 6 may be increased,
unfortunately, because the possibility that light emitted from the
LED chip 6 toward the submount 4 is scattered in a vicinity of the
LED chip 6 may be increased. Consequently, it is speculated that,
in the LED module 1, it is possible to reduce an amount of light
returning to the LED chip 6, compared with a LED module including
the submount 4 constituted by only the second ceramic layer 4a.
Moreover, in the LED module 1, it is possible to reduce the
thickness of the submount 4 required to obtain the same
reflectance, compared with the submount 4 constituted by only the
first ceramic layer 4b.
[0232] As shown in FIG. 20, the color conversion portion 10 is
formed on the submount 4 and has a hemispherical shape so as to
cover the LED chip 6 and a portion of each of the wires 7.
Therefore, the LED module 1 whose configuration is shown in FIG. 20
preferably includes an encapsulating portion (not shown) which
covers the exposed portion of each of the wires 7 and the color
conversion portion 10. The encapsulating portion is preferably made
of a transparent material. The transparent material of the
encapsulating portion may be, for example, a silicone resin, an
epoxy resin, an acrylic resin, glass, or an organic and inorganic
hybrid material in which an organic component and an inorganic
component are mixed and/or combined at a nanometer level or
molecular level. The transparent material of the encapsulating
portion is preferably a material having a linear expansion
coefficient which is close to that of the transparent material of
the color conversion portion 10, and is more preferably a material
having a linear expansion coefficient that is the same as that of
the transparent material of the color conversion portion 10.
Accordingly, in the LED module 1, it is possible to suppress the
concentration of stress on each of the wires 7 in a vicinity of the
interface between the encapsulating portion and the color
conversion portion 10 due to the difference between the linear
expansion coefficients of the encapsulating portion and the color
conversion portion 10. Consequently, in the LED module 1,
disconnection of wires 7 can be suppressed. Furthermore, in the LED
module 1, it is possible to suppress the occurrence of cracks in
the encapsulating portion or in the color conversion portion 10 due
to the difference between the linear expansion coefficients of the
encapsulating portion and the color conversion portion 10. The
encapsulating portion is preferably formed in a hemispherical
shape, but the shape thereof is not limited thereto, and may be a
semiellipse spherical shape or a semicircular columnar shape.
[0233] The color conversion portion 10 may be formed in a
hemispherical shape which covers the LED chip 6, the wires 7, and
the submount 4, similarly to that of the LED module 1 of the first
modification of shown in FIG. 32.
[0234] With regard to the first modification shown in FIG. 32, the
reason why the light outcoupling efficiency of the LED module 1 is
improved will be described with reference to the inferred mechanism
diagrams in FIGS. 33, 34A, 34B, and 34C. Note that the first
modification is in the scope of the present invention, even if the
inferred mechanism is different from the mechanism described
below.
[0235] Arrows shown in FIGS. 33, 34A, 34B, and 34C schematically
illustrate propagating paths of rays of light which are emitted
from the light-emitting layer of the LED structure portion 60 in
the LED chip 6. Solid-line arrows in FIGS. 33, 34A, and 34B
schematically illustrate propagating paths of rays of light which
are emitted from the light-emitting layer and are reflected by the
face 4sa of the submount 4. Broken-line arrows in FIGS. 33, 34A,
34B, and 34C schematically illustrate propagating paths of rays of
light which are emitted from the light-emitting layer of the LED
structure portion 60 and enter the submount 4.
[0236] The inventors inferred that, as shown in FIGS. 33, 34A, and
34B, reflection and refraction occur in the first ceramic layer 4b
at the interface between the ceramic particles and the grain
boundary phase (glass component is the main component therein)
caused by a difference between the refractive indices of the
ceramic particle and the grain boundary phase. Also, the inventors
inferred that, as shown in FIGS. 33 and 34C, reflection and
refraction occur in the second ceramic layer 4a at the interface
between the ceramic particle and the pore and the grain boundary
phase (glass component is the main component) caused by a
difference between the refractive indices of the ceramic particle
and the pore and the grain boundary phase. Also, the inventors
inferred that, as shown in FIGS. 33 and 34C, reflection and
refraction occur in the second ceramic layer 4a at the interface
between the pore and the grain boundary phase caused by a
difference between the refractive indices of the pore and the grain
boundary phase. Also, the inventors inferred that, with respect to
a ceramic plate, when the plate thickness is the same, the larger
the particle diameter of the ceramic particles in the plate, the
smaller the reflectance and the larger the transmittance, since the
larger the particle diameter of the ceramic particles, the smaller
the number of interfaces, and the probability that light passes
through the interface between the ceramic particles and the grain
boundary phase is reduced when light propagates a unit length.
[0237] The inventors inferred that light outcoupling efficiency of
the LED module 1 can be improved by causing light emitted from the
LED chip 6 to pass through the first ceramic layer 4b as much as
possible, and causing the light to be reflected in the second
ceramic layer 4a as much as possible. Therefore, it is preferable
that, in the submount 4, the first ceramic layer 4b includes
ceramic particles having a greater particle diameter than the
second ceramic layer 4a while the second ceramic layer 4a includes
ceramic particles having a smaller particle diameter than the first
ceramic layer 4b and further include pores.
[0238] In the LED module 1, the opaque substrate 2 may have an
elongated shape, and a plurality of LED chips 6 may be arranged
along the longitudinal direction of the opaque substrate 2. In this
case, in the LED module 1, the wires 7 may extend along a direction
perpendicular to the arrangement direction of the LED chips 6, and
the color conversion portions 10 may have a hemispherical shape to
cover the respective LED chips 6 and portions of the respective
wires 7 on the submount 4, similarly to a LED module of the second
modification shown in FIG. 35, for example. Note that, in FIG. 35,
the patterned conductors 8 in FIG. 20 are omitted.
[0239] Alternatively, in the LED module 1, the wires 7 may extend
along the arrangement direction of the LED chips 6, and the color
conversion portions 10 may haves a convex shape to cover the
submount 4, the respective LED chip 6, and the respective wires 7,
similarly to a LED module of the third modification shown in FIG.
36, for example. Note that, in FIG. 36, the patterned conductors 8
in FIG. 20 are omitted.
[0240] Alternatively, in the LED module 1, the wires 7 may extend
along the arrangement direction of the LED chips 6, and the color
conversion portions 10 may haves a convex shape to cover most part
of the submount 4, the respective LED chip 6, and the respective
wires 7, similarly to a LED module of the fourth modification shown
in FIG. 37, for example. Note that, in FIG. 34, the patterned
conductors 8 in FIG. 20 are omitted.
[0241] In the LED module 1 shown in FIG. 37, opposite ends of the
submount 4 in a perpendicular direction to the arrangement
direction of the LED chips 6 are not covered with the color
conversion portion 10 and are exposed.
[0242] In the LED module 1 of the present embodiment, the plurality
of ceramic layers (first ceramic layer 4b and second ceramic layer
4a) of the submount 4 are light-transmissive layers having
different optical properties.
[0243] The submount 4 is constituted by the plurality of
light-transmissive layers stacked in the thickness direction, and
is required to have such a property that optical properties of the
plurality of light-transmissive layers differ from each other, and
a light-transmissive layer of the plurality of light-transmissive
layers which is farther from the LED chip 6 is higher in
reflectance in a wavelength range of the light emitted from the LED
chip 6. Hereinafter, the uppermost light-transmissive layer which
is the closest to the LED chip 6 may be referred to as a first
light-transmissive layer, and the lowermost light-transmissive
layer which is farther from the LED chip 6 may be referred to as a
second light-transmissive layer.
[0244] The first light-transmissive layer is preferably composed of
a material that has high transmittance with respect to light
emitted from the LED chip 6, and has a refractive index close to
the refractive index of the LED chip 6. The refractive index of the
first light-transmissive layer being close to the refractive index
of the LED chip 6 means that the difference between the refractive
index of the first light-transmissive layer and the refractive
index of the substrate 61 in the LED chip 6 is 0.1 or less, and is
more preferably 0. The first light-transmissive layer is preferably
composed of a material having a high thermal resistance.
[0245] The material of the first light-transmissive layer is not
limited to ceramics, and may be glass, SiC, GaN, GaP, sapphire, an
epoxy resin, a silicone resin, unsaturated polyester, or the like.
The material of the ceramics is not limited to Al.sub.2O.sub.3, and
may be another metal oxide (such as magnesia, zirconia, and
titania), a metal nitride (such as aluminum nitride), or the like.
As the material of the first light-transmissive layer, ceramics is
more preferable than a single crystal from a viewpoint of causing
light emitted from the LED chip 6 to be forward-scattered.
[0246] The light-transmissive ceramics may be LUMICERA (registered
trademark) available from Murata Manufacturing Co., Ltd., HICERAM
(product name) available from NGK Insulators, Ltd., or the like.
LUMICERA(registered trademark) has a Ba(Mg,Ta)O.sub.3-based complex
perovskite structure as the main crystal phase. HICERAM is a
light-transmissive alumina ceramic.
[0247] The first light-transmissive layer made of ceramic
preferably include particles having the particle diameter of around
1 .mu.m to 5 .mu.m.
[0248] The first light-transmissive layer may be a single crystal
in which voids, a modified portion having a different refractive
index, or the like is formed. The voids, the modified portion, or
the like may be formed by irradiating, with a laser beam from a
femto-second laser, a scheduled formation region of the voids, the
modified portion, or the like in the single crystal. The wavelength
and the irradiation conditions of the laser beam from the
femto-second laser may vary appropriately according to the material
of the single crystal, the forming target (void or modified
portion), the size of the forming target, or the like. The first
light-transmissive layer may be made of a base resin (such as epoxy
resin, silicone resin, and unsaturated polyester) (hereinafter,
referred to as "first base resin") which contains a filler
(hereinafter, referred to as "first filler") having a refractive
index different from the base resin. It is more preferable that a
difference between the refractive indices of the first filler and
the first base resin is small. The first filler preferably has
higher thermal conductivity. The first light-transmissive layer
preferably has a high density of the first filler, from a viewpoint
of increasing thermal conductivity. The shape of the first filler
is preferably a sphere, from a viewpoint of suppressing total
reflection of incident light. The larger the particle diameter of
the first filler, the smaller the reflectivity and the refractivity
thereof. The first light-transmissive layer may be configured such
that a first filler having a relatively large particle diameter is
present in a region of the first light-transmissive layer close to
the LED chip 6 in the thickness direction, and a first filler
having a relatively small particle diameter is present in a region
thereof distant from the LED chip 6. In this case, the first
light-transmissive layer may include a plurality of stacked layers
having the first fillers with different particle diameters.
[0249] On the surface of the first light-transmissive layer close
to the LED chip 6 (the face 4sa of the submount 4), a fine asperity
structure portion is preferably formed around the mounting region
of the LED chip 6 so as to suppress total reflection of light which
is emitted from the LED chip 6 toward the submount 4 and is
reflected by or refracted in the submount 4. The asperity structure
portion may be formed by roughening the surface of the first
light-transmissive layer by sandblast processing or the like. The
surface roughness of the asperity structure portion is preferably
such that an arithmetic average roughness Ra specified in JIS B
0601-2001 (ISO 4287-1997) is around 0.05 .mu.m.
[0250] The submount 4 may have a configuration in which a resin
layer having a smaller refractive index than the first
light-transmissive layer is formed on the surface of the first
light-transmissive layer close to the LED chip 6 around the
mounting region of the LED chip 6. The material of the resin layer
may be a silicone resin, an epoxy resin, or the like. The material
of the resin layer may be a resin containing a fluorescent
material.
[0251] The second light-transmissive layer is more preferably
configured such that light emitted from the LED chip 6 is diffusely
reflected, than configured such that the light is specularly
reflected.
[0252] The material of the second light-transmissive layer is not
limited to ceramics, and may be glass, SiC, GaN, GaP, sapphire, an
epoxy resin, a silicone resin, unsaturated polyester, or the like.
The material of the ceramics is not limited to Al.sub.2O.sub.3, and
may be another metal oxide (such as magnesia, zirconia, and
titania), a metal nitride (such as aluminum nitride), or the
like.
[0253] The second light-transmissive layer made of ceramics
preferably includes particles having the particle diameter of 1
.mu.m or less, and more preferably include particles having the
particle diameter of around 0.1 .mu.m to 0.3 .mu.m. Also, the
second light-transmissive layer may be the aforementioned porous
layer 4a. In a case where the first light-transmissive layer was
the first ceramic layer 4b composed of alumina having purity of
99.5%, the bulk density of the first light-transmissive layer was
3.8 to 3.95 g/cm.sup.3. In a case where the first
light-transmissive layer was the first ceramic layer 4b composed of
alumina having purity of 96%, the bulk density of the first
light-transmissive layer was 3.7 to 3.8 g/cm.sup.3. In contrast, in
a case where the second light-transmissive layer was the porous
layer 4a, the bulk density of the second light-transmissive layer
was 3.7 to 3.8 g/cm.sup.3. Note that, the aforementioned bulk
density is a value estimated by image processing a SEM image
observed and obtained by an SEM.
[0254] The second light-transmissive layer may be of a single
crystal in which voids, a modified portion having a different
refractive index, or the like is formed. The voids, the modified
portion, or the like may be formed by irradiating, with a laser
beam from a femto-second laser, a scheduled formation region of the
voids, the modified portion, or the like in the single crystal. The
wavelength and the irradiation conditions of the laser beam from
the femto-second laser may vary appropriately according to the
material of the single crystal, the forming target (void or
modified portion), the size of the forming target, or the like. The
second light-transmissive layer may be made of a base resin (such
as epoxy resin, silicone resin, unsaturated polyester, and a
fluorine resin) (hereinafter, referred to as "second base resin")
which contains a filler (hereinafter, referred to as "second
filler") having a refractive index different from the base resin.
The second light-transmissive layer may be configured such that a
second filler having a relatively large particle diameter is
present in a region of the second light-transmissive layer close to
the LED chip 6 in the thickness direction, and a second filler
having a relatively small particle diameter is present in a region
thereof distant from the LED chip 6. The material of the second
filler is preferably, for example, a white inorganic material, and
may be a metal oxide such as TiO.sub.2 and ZnO. The particle
diameter of the second filler is preferably in a range between
around 0.1 .mu.m to 0.3 .mu.m, for example. The filling rate of the
second filler is preferably in a range of around 50 to 75 wt %, for
example. The silicone resin for the second base resin may be methyl
silicone, phenyl silicone, or the like. In a case where the second
filler is in a form of solid particle, it is preferable that there
is a great difference between the refractive indices of the second
filler and the second base resin. A material containing the second
base resin and the second filler in the second base resin may be
KER-3200-T1 available from Shin-Etsu Chemical Co., Ltd. or the
like.
[0255] The second filler may be a core-shell particle, hollow
particle, or the like. The refractive index of the core of the
core-shell particle can be arbitrarily selected, but is preferably
smaller than the refractive index of the second base resin. It is
preferable that the hollow particle has a smaller refractive index
than the second base resin, and that inside of the hollow particle
is gas (such as air and inert gas) or vacuum.
[0256] The second light-transmissive layer may be a light diffusion
sheet. The light diffusion sheet may be a white polyethylene
terephthalate sheet having a plurality of bubbles, or the like.
[0257] The submount 4 may be formed by, in a case of both the first
light-transmissive layer and the second light-transmissive layer
being made of ceramics, stacking ceramic green sheets to be the
first light-transmissive layer and the second light-transmissive
layer individually and sintering the stacked sheets. Note that, in
the submount 4, provided that the second light-transmissive layer
includes bubbles, the first light-transmissive layer may include
bubbles. In such a case, it is preferable that the first
light-transmissive layer is smaller in the number of bubbles and
higher in the bulk density than the second light-transmissive
layer.
[0258] The first light-transmissive layer and the second
light-transmissive layer are preferably composed of a material that
has a high resistance to light and heat, which are emitted from the
LED chip 6 and the fluorescent material.
[0259] The LED module 1 may include a reflection layer over the
further face 4sb of the submount 4 to reflect light from the LED
chip 6 or the like. The reflection layer may be made of silver,
aluminum, a silver aluminum alloy, silver alloys other than the
silver aluminum alloy, an aluminum alloy, or the like. The
reflection layer may be constituted by a thin film, a metal foil, a
solder mask (solder), or the like. The reflection layer may be
provided on the submount 4, or may be provided on the opaque
substrate 2.
Embodiment 3
[0260] An LED module 1 of the present embodiment differs from the
LED module 1 of Embodiment 2 in that, as shown in FIGS. 38A, 38B,
and 38C, an opaque substrate 2 has an elongated shape and a
plurality of LED chips 6 are included. Note that, constituent
elements similar to those in Embodiment 2 are provided with the
same reference numerals, and redundant description thereof will be
omitted.
[0261] In the LED module 1, the plurality of LED chips 6 are
aligned in a prescribed direction (in the horizontal direction in
FIG. 38B) on a surface 2sa of the opaque substrate 2. In the LED
module 1, the LED chips 6 aligned in the prescribed direction and
wires 7 that are connected to the respective LED chips 6 are
covered by a color conversion portion 10 having a band shape. The
color conversion portion 10 has recessed portions 10b to suppress
total reflection of light emitted from the LED chips 6 between
adjacent LED chips 6 to each other in the prescribed direction.
[0262] A patterned conductors (patterned wiring circuit) 8 serving
as a wiring circuit includes a first patterned wiring (first
pattern) 8a to which a first electrode of the LED chip 6 is to be
connected and a second patterned wiring (second pattern) 8b to
which the second electrode of the LED chip 6 is to be
connected.
[0263] The first patterned wiring 8a and the second patterned
wiring 8b each have a planar shape of a comb shape, and are arrayed
so as to interdigitate in the lateral direction of the opaque
substrate 2. In this regard, in the patterned conductors 8, a first
shaft 8aa of the first patterned wiring 8a faces a second shaft 8ba
of the second patterned wiring 8b. In the patterned conductors 8,
first comb teeth 8ab of the first patterned wiring 8a and second
comb teeth 8bb of the second patterned wiring 8b are arranged
alternately in in the longitudinal direction of the opaque
substrate 2 and separated by a space.
[0264] In the LED module 1, the plurality of (nine in an example
shown in the diagram) LED chips 6 are arranged in the longitudinal
direction (in the aforementioned prescribed direction) of the
opaque substrate 2 and are connected in parallel. In the LED module
1, power can be supplied to a parallel circuit in which the
plurality of LED chips 6 are connected in parallel. In short, in
the LED module 1, power can be supplied to all the LED chips 6 by
applying voltage between the first patterned wiring 8a and the
second patterned wiring 8b. When a plurality of the LED modules 1
are arranged, adjacent LED modules 1 may be electrically connected
by conductive members, wires for feed wiring (not shown),
connectors (not shown), or the like. In this case, one power supply
unit can supply power to the plurality of LED modules 1 so that all
the LED chips 6 of the respective LED modules 1 can emit light.
[0265] The patterned conductors 8 are preferably provided with a
surface treatment layer (not shown). The surface treatment layer is
preferably made of a metal material having higher
oxidation-resistance and corrosion-resistance than the material of
the patterned conductors 8. When the patterned conductors 8 are
made of copper, the surface treatment layer is preferably a nickel
film, a stack of a nickel film and a gold film, a stack of a nickel
film, a palladium film, and a gold film, a stack of a nickel film
and a palladium film, or the like, for example. Here, the surface
treatment layer is more preferably a stack of a nickel film and a
palladium film, from the viewpoint of cost reduction. Note that the
surface treatment layer may be formed by plating.
[0266] The color conversion portion 10 is made of a resin
containing a fluorescent material, for example. The color
conversion portion 10 is preferably made of the resin in which the
fluorescent material is dispersed. The resin of the color
conversion portion 10 is not particularly limited, as long as it
transmits light emitted from the LED chip 6 as well as light
emitted from the fluorescent material.
[0267] The resin of the color conversion portion 10 may be a
silicone resin, an epoxy resin, an acrylic resin, an urethane
resin, an oxetane resin, a polycarbonate resin, or the like. As the
resin, the silicone resin is preferable from a viewpoint of thermal
resistance and weather resistance, and gel-like silicone is more
preferable from a viewpoint of suppressing breaking of the wires 7
due to a thermal stress caused by temperature cycling.
[0268] The fluorescent material functions as a wavelength
conversion material to convert light emitted from the LED chip 6
into light having a longer wavelength than the light emitted from
the LED chip 6. Accordingly, the LED module 1 can provide
mixed-color light constituted by the light emitted from the LED
chip 6 and light emitted from the fluorescent material. In short,
the color conversion portion 10 has a function serving as a
wavelength conversion portion to convert light emitted from the LED
chip 6 into light having a longer wavelength than the light emitted
from the LED chip 6. Besides, the color conversion portion 10 has a
function serving as an encapsulating portion for encapsulating each
LED chip 6 and each wire 7.
[0269] When including a blue LED chip as the LED chip 6 and a
yellow fluorescent material as the fluorescent material being the
wavelength conversion material, for example, the LED module 1 can
emit white light. That is, in the LED module 1, blue light emitted
from the LED chip 6 and light emitted from the yellow fluorescent
material can be emitted outside through the surface of the color
conversion portion 10, and as a result, white light can be
obtained.
[0270] The fluorescent material serving as the wavelength
conversion material is not limited to the yellow fluorescent
material, and may include, for example, a set of a yellow
fluorescent material and a red fluorescent material, or a set of a
red fluorescent material and a green fluorescent material. Also,
the fluorescent material serving as the wavelength conversion
material is not limited to one kind of yellow fluorescent material,
and may include two kinds of yellow fluorescent materials having
different emission peak wavelengths. The color rendering property
of LED module 1 can be improved by use of a plurality of
fluorescent materials as the wavelength conversion material.
[0271] The color conversion portion 10 has, as described above,
recessed portions 10b to suppress total reflection of light emitted
from each of the LED chips 6 between the LED chips 6 which are
adjacent to each other in the prescribed direction. Accordingly. in
the LED module 1, it is possible to suppress total reflection of
light which is emitted from the LED chip 6 and then strikes an
interface between the color conversion portion 10 and air.
Consequently, in the LED module 1, it is possible to reduce an
amount of light which is confined due to total reflection, compared
with the LED module including the color conversion portion 10
having a hemicylindrical shape, and therefore light outcoupling
efficiency can be improved. In short, in the LED module 1, a total
reflection loss can be reduced, and light outcoupling efficiency
can be improved.
[0272] The color conversion portion 10 is formed so as to have a
cross section including a step which corresponds to a step between
the face of the LED chip 6 and the surface 2sa of the opaque
substrate 2. Consequently, the color conversion portion 10 has a
cross section along a direction orthogonal to the arrangement
direction of the LED chips 6, and a cross section along the
arrangement direction of the LED chips 6, the former is a convex
shape while the latter has recesses and convexes. In short, in the
LED module 1, the color conversion portion 10 with a band shape has
a recess and convex structure to improve the light outcoupling
efficiency.
[0273] The period of the recess and convex structure is the same as
the array pitch of the LED chips 6. The period of the recess and
convex structure is the array pitch of the convex portions 10a
which cover respective LED chips 6.
[0274] The surface shape of the color conversion portion 10 may be
designed such that the angle between a light ray from the LED chip
6 and a normal line on the surface of the color conversion portion
10 at a point where the light ray from the LED chip 6 crosses the
surface thereof is smaller than the critical angle. Here, in the
LED module 1, each of the convex portions 10a of the color
conversion portion 10 is preferably designed to have the surface
shape such that, in substantially all the areas of the surface of
the convex portion 10a of the color conversion portion 10, the
incident angle (light incident angle) of the light ray from the LED
chip 6 is smaller than the critical angle.
[0275] For this reason, in the color conversion portion 10, each of
the convex portions 10a which covers a corresponding LED chip 6 is
preferably formed in a hemispherical shape. Each convex portion 10a
is designed such that the light axis of the convex portion 10a is
aligned with the light axis of the LED chip 6 covered with the
convex portion 10a in the thickness direction of the opaque
substrate 2. Accordingly, in the LED module 1, it is possible to
suppress not only the total reflection at the surface (interface
between the color conversion portion 10 and air) of the color
conversion portion 10 but also color unevenness. The color
unevenness is a state in which chromaticity varies depending on an
irradiation direction of light. In the LED module 1, the color
unevenness can be suppressed to such an extent the color unevenness
cannot be perceived visually.
[0276] In the LED module 1, it is possible to substantially
equalize light path lengths of light rays from the LED chip 6 to
the surface of the convex portion 10a regardless the emission
direction of light from the LED chip 6. As a result, color
unevenness can be further suppressed. The shape of each convex
portion 10a of the color conversion portion 10 is not limited to
hemisphere, and may be a semielliptical shape, for example. Note
that, each convex portion 10a may have a shape, a cuboid shape, or
the like.
[0277] For manufacturing the LED module 1, first, the opaque
substrate 2 is prepared. Thereafter, the LED chips 6 are die-bonded
on the surface 2sa of the opaque substrate 2 with a die bonding
apparatus or the like. Thereafter, the first electrode and the
second electrode of each of the LED chips 6 are connected to the
patterned wiring circuit 8 via the respective wires 7 with a wire
bonding apparatus, or the like. Thereafter, the color conversion
portion 10 is formed using a dispenser system or the like.
[0278] In a case where the color conversion portion 10 is formed
with a dispenser system, a material of the color conversion portion
10 is applied by discharging the material from a nozzle while a
dispenser head is moved in the arrangement direction of the LED
chips 6, for example.
[0279] In order to apply the material of the color conversion
portion 10 with the dispenser system so as to form an application
shape corresponding to the surface shape of the color conversion
portion 10, the material is discharged and applied while the
dispenser head is moved, for example. Specifically, an application
amount is varied by varying the moving speed of the dispenser head
while the distance between the nozzle and the surface 2sa of the
opaque substrate 2 directly under the nozzle is varied by moving
the dispenser head up and down. More specifically, the moving speed
of the dispenser head is relatively varied in applying the material
between in a region to form the convex portion 10a of the color
conversion portion 10 and in a region to form a portion of the
color conversion portion 10 between adjacent convex portions 10a.
The moving speed of the dispenser head is slow in the former
region, and the moving speed thereof is fast in the latter region.
Moreover, the dispenser head is moved up and down depending on the
surface shape of the color conversion portion 10. Accordingly, by
the method of forming the color conversion portion 10 with the
dispenser system, it is possible to form, with the material, the
application shape in accordance with the surface shape of the color
conversion portion 10. The application shape may be set in view of
contraction in curing the material.
[0280] The dispenser system preferably includes: a movement
mechanism constituted by a robot for moving the dispenser head; a
sensor unit for measuring heights of the surface 2sa of the opaque
substrate 2 and the nozzle from a table; and a controller for
controlling the movement mechanism and a discharge amount of the
material from the nozzle. The controller can be realized, for
example, by loading an appropriate program to a microcomputer. The
dispenser system can be adapted to various types of products
different in the array pitch of the LED chips 6, the number of the
LED chips 6, the width of the color conversion portion 10, or the
like, by changing the program loaded to the controller
appropriately.
[0281] The surface shape of the color conversion portion 10 can be
controlled by adjusting viscosity or the like of the material, for
example. The curvature of the surface (convex face) in each of the
convex portions 10a can be designed with viscosity and surface
tension of the material, a height of the wire 7, or the like.
Larger curvature can be realized by increasing the viscosity and
the surface tension of the material, or by increasing the height of
the wire 7. A smaller width (band width) of the color conversion
portion 10 having the band shape can be realized by increasing the
viscosity and the surface tension of the material. The viscosity of
the material is preferably set to be in a range of around 100 to
2000 mPas. Note that, the value of the viscosity may be measured
under a room temperature using a cone and plate rotational
viscometer, for example.
[0282] The dispenser system may include a heater to heat an
un-cured material so as to adjust viscosity to a desirable value.
Accordingly, in the dispenser system, reproducibility of the
application shape of the material can be improved, and
reproducibility of the surface shape of the color conversion
portion 10 can be improved.
[0283] Hereinafter, a modification of the LED module 1 of the
present embodiment will be described with reference to FIGS. 39 and
40. Note that, constituent elements similar to those in Embodiment
3 are provided with the same reference numerals, and redundant
description thereof will be omitted appropriately.
[0284] In an LED module 1 of the modification, a plurality of LED
chips 6 are arranged on the surface 2sa of the opaque substrate 2
in a prescribed direction (hereinafter, referred to as "first
direction") at equal intervals.
[0285] The patterned conductors 8 serving as a wiring circuit
includes the first patterned wiring 8a and the second patterned
wiring 8b which are each formed into a comb shape and
interdigitate. The first patterned wiring 8a is electrically
connected to the first electrode of each of the LED chip 6 via the
wire 7 (hereinafter, referred to as "first wire 7a"). The second
patterned wiring 8b is electrically connected to the second
electrode of each of the LED chip 6 via the wire 7 (hereinafter,
referred to as "second wire 7b").
[0286] The first patterned wiring 8a includes a first shaft 8aa
formed along the first direction and a plurality of first comb
teeth 8ab which are formed along a second direction orthogonal to
the first direction.
[0287] The second patterned wiring 8b includes a second shaft 8ba
which is formed along the first direction and a plurality of second
comb teeth 8bb which are formed along the second direction.
[0288] The plurality of first comb teeth 8ab of the first patterned
wiring 8a are constituted by first comb teeth 8ab (8ab.sub.1)
having a relatively large tooth width and first comb teeth 8ab
(8ab.sub.2) having a relatively small tooth width. In the first
patterned wiring 8a, the wide first comb teeth 8ab.sub.1 and the
narrow first comb teeth 8ab.sub.2 are arranged alternately in the
first direction.
[0289] The plurality of second comb teeth 8bb of the second
patterned wiring 8b are constituted by second comb teeth 8bb
(8bb.sub.1) having a relatively large tooth width and second comb
teeth 8bb (8bb.sub.2) having a relatively small tooth width. In the
second conductor 8b, the wide second comb teeth 8bb.sub.1 and the
narrow second comb teeth 8bb.sub.2 are arranged alternately in the
first direction.
[0290] The patterned conductors 8 includes the wide first comb
teeth 8ab.sub.1, the narrow second comb teeth 8bb.sub.2, the narrow
first comb teeth 8ab.sub.2, and the comb teeth 8bb.sub.1 which are
arranged cyclically in the first direction.
[0291] The opaque substrate 2 is provided with the patterned wiring
circuit 8 on a surface of a base substrate 2a having an electrical
insulation property. and a mask layer 2b which covers the patterned
wiring circuit 8 over the surface of the base substrate 2a. The
mask layer 2b is formed over the surface of the base substrate 2a
so as to also cover portions in which the patterned wiring circuit
8 is not formed. The material of the mask layer 2b may be a white
mask made of a resin (such as silicone resin) which contains a
white pigment such as barium sulfate (BaSO.sub.4) and titanium
dioxide (TiO.sub.2). The white mask may be a white mask material
"ASA COLOR(registered trademark) RESIST INK" made of silicone
produced by Asahi Rubber Inc., or the like.
[0292] The mask layer 2b has a plurality of openings 2ba for
exposing first pads on the first comb teeth 8ab to which the
respective first wires 7a are connected and a plurality of openings
2bb for exposing second pads on the second comb teeth 8bb to which
the respective second wires 7b are connected. In short, the mask
layer 2b has the openings 2ba and the openings 2bb which are formed
alternately in the first direction. In the mask layer 2b, the
plurality of openings 2ba and the plurality of openings 2bb are
formed so as to be aligned on a line.
[0293] The openings 2ba for exposing the first pads on the wide
first comb teeth 8ab.sub.1 are located at a distant side from the
respective adjacent narrow second comb teeth 8bb.sub.2 with respect
to the respective center lines of the wide first comb teeth
8ab.sub.1 in the first direction. In the LED module 1, the
submounts 4 and the LED chips 6 are arranged vertically above
regions on the wide first comb teeth 8ab.sub.1 that are close to
the respective narrow second comb teeth 8bb.sub.2 with respect to
the respective center lines thereof.
[0294] The openings 2ba for exposing the first pads on the narrow
first comb teeth 8ab.sub.2 are located on the respective center
lines of the narrow first comb teeth 8ab.sub.2.
[0295] The openings 2bb for exposing the second pads on the wide
second comb teeth 8bb.sub.1 are located at a distant side from the
respective adjacent narrow first comb teeth 8ab.sub.2 with respect
to the respective center lines of the wide second comb teeth
8bb.sub.1 in the first direction. In the LED module 1, the
submounts 4 and the LED chips 6 are arranged vertically above
regions on the wide second comb teeth 8bb.sub.1 that are close to
the respective narrow first comb teeth 8ab.sub.2 with respect to
the respective center lines thereof.
[0296] The openings 2bb for exposing the second pads on the narrow
second comb teeth 8bb.sub.2 are located on the respective center
lines of the narrow second comb teeth 8bb.sub.2.
[0297] Each LED chip 6 is located between, in a planar view, the
first pad to which the first electrode is connected via the first
wire 7a and the second pad to which the second electrode is
connected via the second wire 7b. In short, in the LED module 1,
the plurality of LED chips 6, the plurality of first pads, and the
plurality of second pads are formed so as to be aligned on a line
in a planar view.
[0298] The color conversion portion 10 is formed in a band shape to
cover the plurality of LED chips 6, the plurality of first wires
7a, and the plurality of second wires 7b. The cross section of the
color conversion portion 10 along a direction orthogonal to the
first direction is a hemispherical shape. The color conversion
portion 10 may have a similar shape to that of Embodiment 3.
[0299] In the LED module 1 of the modification, the patterned
conductors 8 is present on the opaque substrate 2 to overlap
respective vertical projection regions of the LED chips 6. In the
LED module 1 of the modification, heat generated in the LED chips 6
and the color conversion portions 10 in lighting can thereby be
conducted to a wide area via the patterned conductors 8. That is,
in the LED module 1 of the modification, a heat dissipation
property can be improved, and light output can be increased. In the
LED module 1 of the modification, since the directions of the LED
chips 6 can be made the same. handling of the LED chips 6 in
bonding process of the LED chips 6 on the respective submounts 4 on
the opaque substrate 2 can be facilitated, and manufacturing can be
facilitated.
[0300] Incidentally, the LED modules 1 of Embodiments 2 and 3 and
the LED module 1 of the modification of Embodiment 3 can be used as
a light source for a variety of lighting apparatuses, similar to
the LED modules 1 of Embodiment 1 and the first modification to the
eleventh modification of Embodiment 1. Preferable examples of a
lighting apparatus which includes the LED module 1 include: a
lighting device having a light source which is the LED module 1 and
provided on a device main body; and a lamp (such as a straight-tube
LED lamp and a bulb type lamp), but the lighting apparatus is not
limited thereto and may be other lighting apparatuses.
[0301] Hereinafter, a lighting device 50 including the LED module 1
of Embodiment 3 as a light source will be described with reference
to FIGS. 41A and 41B.
[0302] The lighting device 50 is an LED lighting device and
includes a device main body 51 and an LED module 1 serving as a
light source held by the device main body 51.
[0303] The device main body 51 is formed in an elongated shape
(rectangle plate shape, here) and is larger than the LED module 1
in a planar size. In the lighting device 50, the LED module 1 is
provided on a surface 51b of the device main body 51 in the
thickness direction. In the lighting device 50, the LED module 1
and the device main body 51 are arranged such that the longitudinal
direction of the LED module 1 is aligned with the longitudinal
direction of the device main body 51. The lighting device 50
includes a cover 52 for covering the LED module 1 provided on the
surface 51b of the device main body 51. The cover 52 transmits
light which is emitted from the LED module 1.
[0304] The lighting device 50 includes a lighting unit 53 which
supplies direct current electric power to the LED module 1 for
lighting (allowing light emission) each of the LED chips 2. In the
lighting device 50, the lighting unit 53 and the LED module 1 are
electrically connected via wires 54 e.g., lead wires.
[0305] In the lighting device 50, at the further surface 51c of the
device main body 51 in the thickness direction, a recess 51a is
formed to house the lighting unit 53. The recess 51a is formed
along the longitudinal direction of the device main body 51. Also,
the device main body 51 has a through hole (not shown) to which the
wire 54 is to be inserted. The through hole penetrates a thin
portion between the surface 51b and the inner bottom face of the
recess 51a.
[0306] In the LED module 1, the wires 54 can be connected to
exposed portions of the patterned conductors 8. A connection
portion between the patterned conductors 8 and the wire 54 may be a
connection portion composed of a conductive bonding material such
as solder, a connection portion constituted by a male connector and
a female connector, or the like.
[0307] In the lighting device 50, the LED module 1 can be lighted
with direct current electric power supplied from the lighting unit
53. Note that, the lighting unit 53 may receive power from an
alternating current power supply such as a commercial power supply,
or receive electric power from a direct current power supply such
as a solar cell and a storage battery.
[0308] The light source in the lighting device 50 is not limited to
the LED module 1 of Embodiment 3, but may be any of LED modules 1
of Embodiment 1, the first modification to the ninth modification
of Embodiment 1, Embodiment 2, and the first modification to the
fourth modification of Embodiment 2.
[0309] The device main body 51 is preferably made of a material
having high thermal conductivity, and is more preferably made of a
material having higher thermal conductivity than the opaque
substrate 2. Here, the device main body 51 is preferably made of a
metal having high thermal conductivity such as aluminum and
copper.
[0310] The LED module 1 may be fixed to the device main body 51 by:
a method using a fixture such as a screw; or bonding the device
main body 51 to the LED module 1 by providing therebetween an epoxy
resin layer which is a thermoset sheet adhesive. The sheet adhesive
may be a sheet adhesive made of a stack of a plastic film (PET
film) and a B stage epoxy resin layer (thermoset resin). The B
stage epoxy resin layer contains a filling material composed of a
filler such as silica and alumina and has a property in which
viscosity becomes small and fluidity becomes large when heated.
Such a sheet adhesive may be an adhesive sheet TSA available from
Toray Industries, Inc. or the like. The filler may be an electrical
insulation material having high thermal conductivity than an epoxy
resin which is a thermoset resin. The thickness of the
aforementioned epoxy resin layer is set to be 100 .mu.m, but this
value is an example, and the thickness is not limited thereto, and
may be set in a range of around 50 .mu.m to 150 .mu.m as
appropriate. The thermal conductivity of the aforementioned epoxy
resin layer is preferably larger than 4 W/mK.
[0311] The epoxy resin layer which is a sheet adhesive described
above has high thermal conductivity, high fluidity when heated, and
high adhesiveness to a surface having asperity, along with having
an electrical insulation property. Consequently, in the lighting
device 50, it is possible to suppress generation of gaps between
the aforementioned insulation layer of the epoxy resin layer and
the LED module 1 and between the insulation layer and the device
main body 51, and as a result it is possible to improve adhesion
reliability and to suppress an increase of a thermal resistance and
occurrence of variation due to lack of adhesion. The insulation
layer has an electrical insulation property and thermal
conductivity, and has a function of connecting the LED module 1 and
the device main body 51 thermally.
[0312] Thus, in the lighting device 50, it is possible to lower a
thermal resistance between each LED chip 6 and the device main body
51 and reduce a variation of thermal resistances, compared with a
lighting device where a heat dissipation sheet (heat conduction
sheet) of a rubber sheet type or a silicone gel type such as
Sarcon(registered trademark) is interposed between the LED module 1
and the device main body 51. Accordingly, in the lighting device
50, since the heat dissipation property is improved and therefore
an increase in junction temperature of each of the LED chips 6 can
be suppressed. Hence, input power can be increased and light output
can be increased. The thickness of the aforementioned epoxy resin
layer is set to be 100 .mu.m, but this value is an example, and the
thickness is not limited thereto, and may be set in a range of
around 50 .mu.m to 150 .mu.m as appropriate. The thermal
conductivity of the aforementioned epoxy resin layer is preferably
larger than 4 W/mK.
[0313] The cover 52 may be made of an acrylic resin, a
polycarbonate resin, a silicone resin, glass, or the like.
[0314] The cover 52 has a lens portion (not shown) which is formed
integrally therewith and controls a directional distribution of
light emitted from the LED module 1. Cost can be reduced compared
with a configuration in which a lens which has been separately
prepared from the cover 52 is attached to the cover 52.
[0315] The lighting device 50 described above includes the LED
module 1 serving as the light source, and therefore cost thereof
can be reduced and light output thereof can be increased.
[0316] The lighting device 50 includes the device main body 51 made
of metal, and therefore the heat dissipation property thereof can
be improved.
[0317] Hereinafter, a straight-tube LED lamp 80 including a light
source that is the LED module 1 of Embodiment 3 will be described
with reference to FIGS. 42A and 42B.
[0318] The straight-tube LED lamp 80 includes: a tube main body 81
having a straight-tube shape (cylindrical shape) formed of a
light-transmissive material; and a first cap 82 and a second cap 83
that are respectively provided at an end portion and the other end
portion of the tube main body 81 in the longitudinal direction. The
LED module 1 of Embodiment 3 is housed in the tube main body 81.
The LED module 1 is not limited to the LED module 1 of Embodiment
3, but may be any of LED modules 1 of Embodiment 1, the first
modification to the ninth modification of Embodiment 1, Embodiment
2, the first modification to fourth modification of Embodiment 2,
and the modification of Embodiment 3. Note that, in terms of a
general straight-tube LED lamp, "straight-tube LED lamp system with
L-type pin cap GX16t-5 (for general illumination)" (JEL 801:2010)
is standardized by Japan Electric Lamp Manufacturers Association,
for example.
[0319] The tube main body 81 may be made of transparent glass,
milky white glass, a transparent resin, a milky white resin, or the
like.
[0320] The first cap 82 has two power supply terminals 84 and 84
(hereinafter referred to as "first lamp pins") which are
electrically connected to the LED module 1. These two first lamp
pins 84 and 84 are configured to be electrically connected to two
power supply contacts respectively of a lamp socket for a power
supply which is held in the device main body of a lighting device
(not shown).
[0321] The second cap 83 has one grounding terminal 85 (hereinafter
referred to as "second lamp pin") for grounding. This one second
lamp pin 85 is configured to be electrically connected to a
grounding contact of a lamp socket for grounding which is held in
the device main body.
[0322] Each of the first lamp pins 84 is formed in an L-shape. and
is constituted by a pin main body 84a which protrudes along the
longitudinal direction of the tube main body 81 and a key portion
84b which extends along the radial direction of the tube main body
81 from the tip of the pin main body 84a. The two key portions 84b
extend in directions so as to be farther from each other. Note that
each of the first lamp pins 84 is formed by bending a long metal
plate.
[0323] The second lamp pin 85 protrudes from an end face (cap
reference face) of the second cap 83 in the opposite direction to
the tube main body 81. The second lamp pin 85 is formed in a
T-shape. Note that the straight-tube LED lamp 80 is preferably
configured so as to meet the standard of "straight-tube LED lamp
system with L-type pin cap GX16t-5 (for general illumination)" (JEL
801:2010) which is standardized by Japan Electric Lamp
Manufacturers Association, or the like.
[0324] The straight-tube LED lamp 80 as described above includes
the aforementioned LED module 1 in the tube main body 81, and
therefore cost thereof can be reduced and light output thereof can
be increased.
[0325] A lamp which includes the LED module 1 is not limited to the
aforementioned straight-tube LED lamp, and may be a straight-tube
LED lamp including the LED module 1 and a lighting unit to switch
on the LED module 1 both in the tube main body. Note that power is
supplied to the lighting unit from an external power supply via
lamp pins.
[0326] The LED module 1 of Embodiment 3 includes the opaque
substrate 2 having an elongated shape and a plurality of the LED
chips 6, but the shape of the opaque substrate 2 and the number of
LED chips 6 and arrangement of the LED chips 6 can be changed as
appropriate depending on the type or the like of the lighting
device to which the LED module 1 is applied.
[0327] Hereinafter, an embodiment of another lighting device 70
including the LED module 1 will be described with reference to
FIGS. 41 and 42.
[0328] The lighting device 70 is an LED lighting device which can
be used as a downlight, and includes a device main body 71 and a
light source that is the LED module 1 and is held by the device
main body 71. Besides, the lighting device 70 includes a case 78
which has a rectangular box shape and accommodates a lighting unit
to operate the LED module 1. The lighting unit and the LED module 1
are electrically connected by wires (unshown) or the like.
[0329] In the lighting device 70, the device main body 71 is formed
in a disk shape, and the LED module 1 is present on a face of the
device main body 71. The lighting device 70 includes a plurality of
fins 71ab which protrude from a further face of the device main
body 71. The device main body 71 and the fins 71ab are formed
integrally.
[0330] In the LED module 1, an opaque substrate 2 has a rectangular
shape, a plurality of (not shown) LED chips are arranged in a
two-dimensional array on a surface 2sa of the opaque substrate 2,
and a color conversion portion 10 covers all these plurality of LED
chips. Note that. this LED chip may be the same as the LED chip 6
in Embodiment 3.
[0331] Moreover, the lighting device 70 includes a first reflector
73 to reflect light which is emitted laterally from the LED module
1, a cover 72, and a second reflector 74 to control a directional
distribution of light which is outputted from the cover 72. Note
that, in the lighting device 70, an outer cover to house the LED
module 1, the first reflector 73 and the cover 72 is constituted by
the device main body 71 and the second reflector 74.
[0332] The device main body 71 has two projecting base portions
71a, which face each other on the face thereof. In the lighting
device 70, a plate shaped fixing member 75 to fix the LED module 1
is attached to the two projecting base portions 71a. The fixing
member 75 is formed of a metal plate, and is fixed to each of the
projecting base portions 71a by a screw 77. The first reflector 73
is fixed to the device main body 71. The LED module 1 may be
sandwiched between the first reflector 73 and the fixing member 75.
The first reflector 73 is formed of a white synthetic resin.
[0333] The fixing member 75 has an opening 75a for exposing part of
the opaque substrate 2 of the LED module 1. The lighting device 70
includes a thermal conduction portion 76 interposed between the
opaque substrate 2 and the device main body 71. The thermal
conduction portion 76 has a function of conducting heat from the
opaque substrate 2 to the device main body 71. The thermal
conduction portion 76 is formed of a heat-conductive grease, but is
not limited thereto, and may be formed of a heat-conductive
sheet.
[0334] The heat-conductive sheet may be a silicone gel sheet having
electrical insulation and thermal conductivity. The silicone gel
sheet used as the heat-conductive sheet is preferably soft. This
king of silicone gel sheet may be Sarcon(registered trademark) or
the like.
[0335] The material of the heat-conductive sheet is not limited to
silicone gel, and may be elastomer, for example, so long as the
material has electrical insulation and thermal conductivity.
[0336] In the lighting device 70, heat generated in the LED module
1 can be efficiently conducted to the device main body 71 via the
thermal conduction portion 76. Consequently, in the lighting device
70, heat generated in the LED module 1 can be efficiently released
from the device main body 71 and the fins 71ab.
[0337] The device main body 71 and the fins 71ab are preferably
formed of a material having high thermal conductivity, and more
preferably made of a material having higher thermal conductivity
than the opaque substrate 2. Here, the device main body 71 and the
fins 71ab are preferably formed of a metal having high thermal
conductivity such as aluminum and copper.
[0338] The cover 72 may be made of an acrylic resin, a
polycarbonate resin, a silicone resin, glass, or the like.
[0339] The cover 72 may has a lens portion (not shown) for
controlling a directional distribution of light emitted from the
LED module 1. The cover 72 and the lens portion may be formed
integrally.
[0340] The second reflector 74 may be made of aluminum, stainless
steel, a resin, ceramic, or the like.
[0341] The lighting device 70 described above includes a light
source that is the aforementioned LED module 1, and therefore cost
can be reduced and light output can be increased. Besides, the
lighting device 70 may have a configuration in which the device
main body 71 also serves as the opaque substrate 2 of the LED
module 1.
* * * * *