U.S. patent application number 14/293010 was filed with the patent office on 2014-12-11 for light emitting device.
This patent application is currently assigned to NICHIA CORPORATION. The applicant listed for this patent is NICHIA CORPORATION. Invention is credited to Tomonori MIYOSHI, Kenji OZEKI.
Application Number | 20140362570 14/293010 |
Document ID | / |
Family ID | 50828810 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140362570 |
Kind Code |
A1 |
MIYOSHI; Tomonori ; et
al. |
December 11, 2014 |
LIGHT EMITTING DEVICE
Abstract
A light emitting device include a plurality of arrayed light
emitting elements, each light emitting element including a
plurality of side faces; at least one light reflecting member that
covers the side faces of each of the light emitting elements; and
at least one light blocking member disposed in between light
emitting elements and disposed separated from the light emitting
elements.
Inventors: |
MIYOSHI; Tomonori;
(Tokushima-shi, JP) ; OZEKI; Kenji;
(Tokushima-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NICHIA CORPORATION |
Anan-shi |
|
JP |
|
|
Assignee: |
NICHIA CORPORATION
Anan-shi
JP
|
Family ID: |
50828810 |
Appl. No.: |
14/293010 |
Filed: |
June 2, 2014 |
Current U.S.
Class: |
362/240 |
Current CPC
Class: |
F21Y 2115/10 20160801;
H01L 33/60 20130101; H01L 33/58 20130101; H01L 2933/0058 20130101;
H01L 25/0753 20130101; H01L 2924/0002 20130101; F21K 9/68 20160801;
H01L 2224/16 20130101; H01L 33/56 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
362/240 |
International
Class: |
F21S 2/00 20060101
F21S002/00; F21V 7/00 20060101 F21V007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 5, 2013 |
JP |
2013-118558 |
Claims
1. A light emitting device comprising: a plurality of arrayed light
emitting elements, each light emitting element including a
plurality of side faces; at least one light reflecting member that
covers the side faces of each of the light emitting elements; and
at least one light blocking member disposed in between light
emitting elements and disposed separated from the light emitting
elements.
2. The light emitting device according to claim 1, further
comprising at least one translucent member that covers at least one
upper face of the light emitting element, the light reflecting
member covers side faces of the translucent member.
3. The light emitting device according to claim 2, wherein the
light blocking member is disposed between the light reflecting
members that cover the side faces of the translucent member and is
disposed in between the light emitting elements.
4. The light emitting device according to claim 1, wherein the
light emitting elements are joined on a base material and an
embedding material is embedded between the base material and the
light emitting elements.
5. The light emitting device according to claim 4, wherein the
embedding material is formed from a light reflecting resin.
6. The light emitting device according to claim 2, wherein upper
faces of the translucent member, the light reflecting member and
the light blocking member substantially lie on the same plane.
7. The light emitting device according to claim 1, wherein a
plurality of light emitting elements are mounted on the base
material so as to be independently driven according to a wiring
pattern of the base material.
8. The light emitting device according to claim 1, wherein the
light reflecting member has a groove at between the light emitting
elements, and the light blocking member is disposed in a groove
formed in the light reflecting member.
9. The light emitting device according to claim 8, wherein the
groove is disposed extending to the ends of the light reflecting
members.
10. The light emitting device according to claim 1, wherein the
light blocking member is disposed in a straight line between the
light emitting elements.
11. A light emitting device comprising: a plurality of arrayed
light emitting elements, each light emitting element including a
plurality of side faces; light reflecting members that covers the
side faces of each of the light emitting elements; and at least one
light blocking member disposed between the light reflecting members
in between light emitting elements.
12. The light emitting device according to claim 11, further
comprising at least one translucent member that covers at least one
upper face of the light emitting element, the light reflecting
member covers side faces of the translucent member.
13. The light emitting device according to claim 12, wherein the
light blocking member is disposed between the light reflecting
members that cover the side faces of the translucent member and is
disposed in between the light emitting elements.
14. The light emitting device according to claim 11, wherein the
light emitting elements are joined on a base material and an
embedding material is embedded between the base material and the
light emitting elements.
15. The light emitting device according to claim 14, wherein the
embedding material is formed from a light reflecting resin.
16. The light emitting device according to claim 12, wherein upper
faces of the translucent member, the light reflecting member and
the light blocking member substantially lie on the same plane.
17. The light emitting device according to claim 11, wherein a
plurality of light emitting elements are mounted on the base
material so as to be independently driven according to a wiring
pattern of the base material.
18. The light emitting device according to claim 11, wherein the
light reflecting member has a groove at between the light emitting
elements, and the light blocking member is disposed in a groove
formed in the light reflecting member.
19. The light emitting device according to claim 18, wherein the
groove is disposed extending to the ends of the light reflecting
members.
20. The light emitting device according to claim 11, wherein the
light blocking member is disposed in a straight line between the
light emitting elements.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2013-118558 filed on Jun. 5, 2013. The entire
disclosure of Japanese Patent Application No. 2013-118558 is hereby
incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a light emitting device
including a plurality of light emitting element.
[0004] 2. Related Art
[0005] Semiconductor light emitting elements have been used in
recent years not only as illumination light sources instead of
fluorescent bulbs, but also as light sources with good
directionality and high brightness in projection illumination
devices, projectors, and so forth, such as automotive
headlights.
[0006] The light emitting device used in such applications is
proposed, for example, in JP2012-99545A, and has the side faces of
a plurality of light emitting elements covered with a reflecting
material, with these elements being arranged in a row and close
together.
SUMMARY
[0007] The embodiments of the invention provides a light emitting
device. This light emitting device include a plurality of arrayed
light emitting elements, each light emitting element including a
plurality of side faces; at least one light reflecting member that
covers the side faces of each of the light emitting elements; and
at least one light blocking member disposed in between light
emitting elements and disposed separated from the light emitting
elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1A is a simplified plan view of the light emitting
device in Embodiment 1 of the present invention;
[0009] FIG. 1B is a cross section along the A-A' line in FIG.
1A;
[0010] FIG. 2A is a simplified plan view of the process for
manufacturing the light emitting device in Embodiment 1 of the
present invention;
[0011] FIG. 2B is a cross section along the A-A' line in FIG.
2A;
[0012] FIG. 3 is a simplified plan view of the process for
manufacturing the light emitting device in Embodiment 1 of the
present invention;
[0013] FIG. 4A is a simplified plan view of the process for
manufacturing the light emitting device in Embodiment 1 of the
present invention;
[0014] FIG. 4B is a cross section along the A-A' line in FIG.
4A;
[0015] FIG. 5 is a simplified plan view illustrating a method for
evaluating the light emitting device in Embodiment 1 of the present
invention;
[0016] FIG. 6 is a simplified cross section of the light emitting
device in Embodiment 2 of the present invention;
[0017] FIG. 7 is a simplified cross section of the light emitting
device in Embodiment 3 of the present invention;
[0018] FIG. 8 is a simplified plan view of the light emitting
device in Embodiment 4 of the present invention; and
[0019] FIG. 9 is a simplified plan view of the light emitting
device in Embodiment 5 of the present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0020] The present invention is an object thereof to provide a
light emitting device having good brightness distribution and good
visibility, and with which there is a clear difference between
emitting and non-emitting parts.
[0021] The sizes and the arrangement relationships of the members
in each of drawings are occasionally shown exaggerated for ease of
explanation. Further, in the description below, the same
designations or the same reference numerals may, in principle,
denote the same or like members and duplicative descriptions will
be appropriately omitted. In addition, constitutions described in
some of examples and embodiments can be employed in other examples
and embodiments.
[0022] In the specification, the term "upper" and "lower" also mean
a light extraction side and the opposite side from the light
extraction side, respectively. For example, the upper face means
the light extraction face of the light emitting device, whereas the
lower face means the opposite side from light extraction face of
the light emitting device.
[0023] As shown in FIGS. 1A and 1B, the light emitting device 10 in
this embodiment has a plurality of light emitting elements 11, at
least one light reflecting member 12 and at least one light
blocking member 13.
[0024] According to the light emitting devices, and particularly
with light emitting devices equipped with a plurality of light
emitting elements, it is possible to provide a light emitting
device with good visibility, with which there is a clear difference
between elements in an emission state and elements in a
non-emission state.
[0025] Light Emitting Elements 11
[0026] A light emitting diode is usually used as the light emitting
element 11.
[0027] The composition, emission color or wavelength, size, number,
etc., can be suitably selected according to the intended use.
Examples of light emitting element emitted with blue or green light
include one using a semiconductor layer such as ZnSe, gallium a
nitride-based semiconductor, for example,
In.sub.XAl.sub.YGa.sub.1-X-YN (0.ltoreq.X, 0.ltoreq.Y, X+Y<1),
GaP and the like, examples of light emitting element emitted with
red light include one using a semiconductor layer such as GaAlAs,
AlInGaP and the like.
[0028] The light emitting elements are usually formed by laminating
semiconductor layers on a growth substrate (such as a sapphire
substrate). The growth substrate may have concavity and convexity
on the face joined with the semiconductor layer. This allows the
critical angle when light emitted from the semiconductor layer
irradiates the growth substrate to be changed intentionally, and
allows the light to be easily extracted to the outside of the
growth substrate.
[0029] The growth substrate of the light emitting elements may be
removed after the lamination of the semiconductor layers. This
removal can be accomplished, for example, by polishing, LLO (laser
lift-off), etc. When the growth substrate is to be removed, the
semiconductor layer may also include a supporting substrate used
for mounting.
[0030] The light emitting elements preferably have a pair of
positive and negative electrodes on the same side to the
semiconductor layers. This allows the light emitting elements to be
flip-chip mounted on a base material for mounting. In this case,
the face opposite the face on which the pair of electrodes is
formed will be the light extraction face. In flip-chip mounting,
the light emitting elements are electrically connected to a wiring
pattern on the base material by using a bump joining member, a
thin-film joining member, or a paste joining member having
conductivity, such as solder.
[0031] Alternatively, in the case of face-up mounting, the face on
which the pair of electrodes is formed may be the light extraction
face.
[0032] The light emitting elements preferably have a pair of
positive and negative electrodes on the same side, but may instead
have a pair of positive and negative electrodes on different sides.
In the case of light emitting elements having an opposing electrode
structure in which the positive and negative electrodes are
provided on opposite faces, the lower face electrode may be fixed
to the base material with a conductive material, and the upper face
electrode may be connected to the base material with a conductive
wire or the like.
[0033] A plurality of the light emitting elements are included in a
single light emitting device. The plurality of light emitting
elements are arrayed in a row, for example, but may instead be
arrayed in a matrix. The number of light emitting elements can be
suitably set according to the characteristics, size, and so forth
of the light emitting device to be obtained.
[0034] The arranged light emitting elements are preferably close to
each other, and when automotive applications, as well as brightness
distribution and so forth are taken into account, the distance
between the light emitting elements is preferably less than the
size of the light emitting elements themselves (such as the length
along one side), and more preferably, for example, is about 30% or
less, and even more preferably 20% or less, of the size of the
light emitting elements themselves. Thus disposing the light
emitting elements close together affords a light emitting device
with a planar light source that offers little emission variation
and high emission quality.
[0035] Light Reflecting Members 12
[0036] The light emitting device has one or more light reflecting
member 12. That is, the light reflecting member may be formed to
cover a plurality of light emitting elements integrally.
Alternatively, the light reflecting members may be formed to cover
each light emitting elements individually, or to cover a plurality
of assorted light emitting elements.
[0037] As shown in FIGS. 1A and 1B, the light reflecting members 12
cover the side faces of the light emitting elements 11. The "side
faces of the light emitting elements 11" here refers to at least
part of the side faces of the semiconductor layer in the thickness
direction, and preferably all of the semiconductor layer in the
thickness direction and/or part of the side faces of the
semiconductor layer around the outer periphery, and more preferably
the entire side faces around the outer periphery of the
semiconductor layer. The term "cover" as used herein may mean that
a separate layer is interposed between semiconductor layer and the
light reflecting member, but the light reflecting member is
preferably in contact with the semiconductor layer. It is
especially preferable for the entire outer peripheral side faces of
the light emitting elements that are included to be covered by the
light reflecting members. Consequently, the light emitted from the
light emitting elements at the boundary between the light emitting
elements and the light reflecting members will be reflected within
the light emitting elements, so the light will not be absorbed by
adjacent light emitting elements, and will instead be emitted from
the upper faces of the light emitting elements to the upper faces
of the translucent members and the outside.
[0038] The separate layer referred to here is, for example, an
adhesive agent or an embedding material. An adhesive agent is used
when the light emitting elements are further provided with
translucent members that cover upper face of the light emitting
element. In particular, when translucent members that are larger
than the light emitting elements are provided, the adhesive agent
will sometimes be disposed all the way to the light emitting
element side faces so that light from the light emitting elements
will propagate more easily to the translucent members. If an
adhesive agent is interposed between the semiconductor layer and
the light reflecting members, the adhesive agent is preferably
disposed so as not to bulge out from directly below the translucent
members. Also, when an embedding material is interposed, it is
preferably a light reflecting resin. When the embedding material is
a light reflecting resin, there are no particular restricts on the
interposition thickness, but when the above-mentioned covering of
the side faces of the light emitting elements 11 by the light
reflecting members 12 is taken into account, it is preferable for
the material to be interposed only in part of the thickness
direction of the side faces of the semiconductor layer, exposing at
least the side higher than the light emitting layer of the light
emitting elements, or for the material to be interposed so as to
expose the light emitting layer and the side higher than the light
emitting layer.
[0039] When a separate layer is interposed between the light
emitting elements and the light reflecting resin, the separate
layer is preferably disposed so as not to be exposed on the light
emitting face side of the light emitting device. If the separate
layer is exposed on the light emitting face side, there is the risk
that light will be reflected and propagate between the light
emitting elements and the light reflecting members, resulting in
uneven color.
[0040] The upper faces of light reflecting members disposed between
the light emitting elements can be in the same plane, or
substantially in the same plane, as the upper faces of the light
emitting elements (the light extraction face). The term "in the
same plane" here means that a height difference of about .+-.10%,
and preferably .+-.5%, of the thickness of the light reflecting
members is allowed (the same applies elsewhere in this
Specification).
[0041] Alternatively, as discussed below, if at least one
translucent member that covers the upper faces of the light
emitting elements are further provided to these faces, the upper
faces of the light reflecting members preferably is on the same
plane, or substantially on the same plane, as the upper face of the
translucent member.
[0042] In particular, as discussed below, the thickness (width) of
the light reflecting members covering the side faces of the light
emitting elements to the light blocking member at the locations
where the light blocking are disposed between the light reflecting
members in between the light emitting elements is preferably about
10 to 100 .mu.m, and more preferably about 50 to 100 .mu.m. Setting
to this thickness will keep light leakage to a minimum, and allow
the light to be reflected efficiently, while reducing the distance
between adjacent light emitting elements and ensuring a good
brightness distribution.
[0043] The light reflecting members are formed from a material
capable of reflecting the light emitted from the light emitting
elements. Consequently, the light emitted from the light emitting
elements is reflected within the light emitting elements at the
boundary between the light emitting elements and the light
reflecting members. As a result, the light propagates within the
light emitting elements, and is ultimately emitted from the upper
faces of the light emitting elements to the upper faces of the
translucent members and to the outside.
[0044] The light reflecting members can be formed from a resin
including at least one of a silicone resin, a modified silicone
resin, an epoxy resin, a modified epoxy resin, an acrylic resin or
a hybrid resin containing one or more of those resins, and a
reflecting substance. Examples of the reflecting substance include
titanium oxide, silicon oxide, zirconium oxide, potassium titanate,
alumina, aluminum nitride, boron nitride, mullite and the like.
[0045] The content of the reflecting substance, etc., can change
the amount of light reflected, transmitted, etc., by the light
reflecting members, so it can be suitably adjusted according to the
desired characteristics of the light emitting device and so forth.
For example, the reflecting substance is preferably contained in an
amount of at least 30 wt %.
[0046] As the light reflecting members, a material having heat
dissipation property in addition to light reflecting property may
be used. The thermal conductivity of the light reflecting member is
preferably at least about 0.2 w/mk, and more preferably at least 1
W/mK. Setting the thermal conductivity higher, it is possible to
improve the heat dissipation property. Examples of such material
include aluminum nitride, boron nitride and the like having
relatively high thermal conductivity.
[0047] For example, as discussed below, if the translucent members
contain a fluorescent material, the fluorescent material will
sometimes undergo self-heating attributable to Stokes loss, and
this heat may lower the light conversion efficiency. On the other
hand, if the light reflecting members have high thermal
conductivity, heat from the fluorescent material in the translucent
members can be efficiently dissipated.
[0048] The light reflecting members can be formed, for example, by
injection molding, potting, resin printing, transfer molding,
compression molding, and so forth.
[0049] A Zener diode or other such protective element may be
installed in the light emitting device of the present invention.
Embedding a protective element in the light reflecting members, for
example, will prevent a decrease in light extraction caused when
the light from the light emitting elements is absorbed by the
protective element, or is blocked by the protective element.
[0050] Light Blocking Members 13
[0051] The light emitting device has one or more light blocking
member 13. That is, one or more the light blocking member may be
disposed in between light emitting elements and disposed separated
from the light emitting elements.
[0052] For example, as shown in FIGS. 1A and 1B, one or more the
light blocking member 13 may be disposed between the light
reflecting members 12 covering the side faces between the light
emitting elements 11. The phrase "between the light reflecting
members" here means that the light reflecting members covering the
side faces of the light emitting elements are segmentalized. That
is, the light blocking member is preferably disposed in a groove
which is formed in the light reflecting member at between the light
emitting elements 11. Therefore, the light blocking members 13 may
only be disposed between at least the adjacent light emitting
elements as seen in top view, and disposed separated from the light
emitting elements, but are preferably disposed extending from
between the adjacent light emitting elements toward the ends of the
light reflecting members, and more preferably disposed extending to
the ends of the light reflecting members. This disposition
effectively prevents the light emitted from one light emitting
element from passing through the light reflecting members and
interfering with adjacent light emitting elements and/or the light
emitted from those, etc.
[0053] The light blocking members 13 are preferably disposed in a
straight line between the light emitting elements, as seen in top
view, and more preferably are disposed in a straight line in the
middle between the light emitting elements. This disposition
ensures uniformity in the thickness of the light reflecting members
covering the area between light emitting elements, and affords a
light emitting device with good visibility and a good brightness
distribution.
[0054] The width of the light blocking members in cross sectional
view may be substantially uniform, but may also taper down as in a
V shape, for example. A V-shaped cross section allows light in the
side face direction to be confined in the downward direction, which
affords better visibility. A V-shaped cross section can be formed
by using a blade with a tapered tip, etc., in the segmentalization
of the light reflecting members.
[0055] The width is preferably set so that the material forming the
light blocking members fills in the space by capillary action in
the manufacturing method discussed below. The width may be about 10
to 100 .mu.m, preferably 30 to 90 .mu.m, and more preferably 40 to
70 .mu.m, in plan view, for example. Thus setting the width
effectively prevents light leakage between adjacent light emitting
elements, and ensures good visibility and good brightness
distribution. In particular, this minimizes the interference of
light from a lit light emitting element with an unlit light
emitting element when adjacent light emitting elements are in lit
and unlit states, and this greatly reduces the micro-emission level
of unlit light emitting elements.
[0056] The height of the light blocking members is preferably at
least equal to the height corresponding to all or part of the
thickness direction of the semiconductor layer of the light
emitting elements, and the upper face of the light blocking members
more preferably is on the same plane, or substantially in the same
plane, as the upper faces of the light reflecting members and/or
the light extraction faces of the light emitting elements.
[0057] Alternatively, as discussed below, if the translucent
members that cover the light extraction faces of the light emitting
elements are further provided to these faces, the upper faces of
the light blocking members preferably are on the same plane, or
substantially on the same plane, as the upper faces of the
translucent members. In other words, the light blocking members
preferably cover the side faces of the translucent members.
[0058] Also, as discussed below, if the light emitting elements are
joined on the base material, the lower ends of the light blocking
members preferably coincide with the surface of the base material,
but may not necessarily have to reach all the way to the surface of
the base material. This would be to avoid damaging the base
material and/or the wiring, etc., disposed on the base material
surface during processing. If the lower ends of the light blocking
members do not reach the base material surface, then the lower ends
of the base material surface preferably are disposed below the
lower faces of the light emitting elements. This minimizes light
interference between adjacent light emitting elements.
[0059] Furthermore, when the light emitting elements are joined on
the base material, and an embedding material is embedded between
the base material and the light emitting elements (discussed below)
and reaches to between the light emitting elements, the lower ends
of the light blocking members may be disposed either on the surface
of the embedding material or in the embedding material.
[0060] The light blocking members can be formed from a material
capable of blocking or absorbing the light emitted from the light
emitting elements. As mentioned above, this effectively prevents
light leakage between adjacent light emitting elements, and ensures
good visibility and good brightness distribution. In particular,
this minimizes the interference of light from a lit light emitting
element with an unlit light emitting element when adjacent light
emitting elements are in lit and unlit states, and this greatly
reduces the micro-emission level of unlit light emitting
elements.
[0061] The light blocking members may be disposed between some or
all of the light emitting elements installed in the light emitting
device. For example, when a plurality of light emitting elements
are arranged in a row, a light blocking member may be disposed at
only one location between any two adjacent light emitting elements,
and when the light emitting elements are arranged in two rows, the
light blocking members may be disposed between the rows, and when
the light emitting elements are disposed in a matrix, the light
blocking members may be disposed in a lattice shape between all of
the light emitting elements. The layout of the light blocking
members can be suitably varied according to the object and
application.
[0062] The light blocking members can be formed from a resin
including at least one of a silicone resin, a modified silicone
resin, an epoxy resin, a modified epoxy resin, an acrylic resin or
a hybrid resin containing one or more of those resins, and a light
absorbing substance. Examples of the light absorbing substance
include a black pigment, carbon black and the like.
[0063] Further, the light reflecting members may be formed using a
reflecting substance together with the light absorbing substance.
Examples of the reflecting substance include titanium oxide,
silicon oxide, zirconium oxide, potassium titanate, alumina,
aluminum nitride, boron nitride, mullite and the like.
[0064] The content of light absorbing substance, reflecting
substance, etc., can be suitably adjusted as dictated by the type
and so forth of the light absorbing substance and reflecting
substance being used. For example, it is preferably that the
content of the light absorbing substance is at least 1 wt % and the
reflecting substance is at least 30 wt %.
[0065] The light blocking members may be made from a material that
has the above-mentioned heat dissipation properties, in addition to
having light absorption properties and light reflecting
properties.
[0066] The light blocking members can be formed by removing the
light reflecting members where the light blocking members are to be
disposed by using a blade, laser irradiation, or the like after the
formation of the light reflecting members, and using a mold method
or the like to fill in these removed locations.
[0067] Translucent Members
[0068] The light emitting device preferably further has translucent
members that cover the upper faces (light extraction faces) of the
light emitting elements (see 18 in FIG. 1B). The translucent
members are able to transmit light emitted from the light emitting
elements, and release this light to the outside.
[0069] The translucent members preferably cover the entire upper
faces of the light emitting elements in order to extract all of the
light emitted from the light emitting elements. However, it may be
that the more the size of the translucent members exceeds that of
the light emitting elements, the lower is the brightness of the
light emitted from these elements. Therefore, the translucent
members covering the light emitting elements are at least as large
as the light emitting elements, but are preferably as close in size
to that of the light emitting elements as possible. This affords
even higher brightness, in addition to making to possible for the
light emitting device to be even more compact.
[0070] When a plurality of light emitting elements are individually
covered by translucent members that are larger than the light
emitting elements, the distance between the translucent members is
preferably less than the size of the translucent members themselves
(the length along one side, for example), and is more preferably no
more than 20% of the size of the translucent members themselves.
Thus disposing the translucent members close together gives a light
emitting device of a planar light source with little emission
unevenness and high emission quality.
[0071] The translucent member may individually cover a plurality of
light emitting elements, or may integrally cover a plurality of
light emitting elements.
[0072] The side faces of translucent members that individually
cover a plurality of light emitting elements are preferably covered
by the light reflecting members. In this case, the light blocking
members are preferably disposed between the light reflecting
members in between the plurality of translucent members.
[0073] The side faces of the translucent members integrally
covering a plurality of light emitting elements does not
necessarily have to be covered by the light reflecting members
and/or the translucent members.
[0074] It is especially preferable if the side faces of translucent
members that individually cover a plurality of light emitting
elements are covered by the light reflecting members, and the light
blocking members are disposed between the light reflecting members
in between the translucent members.
[0075] For example, (1) after a plurality of light emitting
elements have been joined on the base material, a plurality of
translucent members may be disposed on the various upper faces of
these light emitting elements, after which this may be covered with
the light reflecting members, and the light blocking members are
formed between the light reflecting members, or (2) after a
plurality of light emitting elements have been joined on the base
material, a single translucent member may be disposed on the upper
faces of these light emitting elements, after which the translucent
member is cut between the light emitting elements with a blade,
laser irradiation, or the like, this is covered with the light
reflecting members, and light blocking members are formed between
the light reflecting members, or (3) after a plurality of light
emitting elements have been joined on the base material, the light
reflecting members may cover the side faces of the light emitting
elements, and a single translucent member may be disposed on the
light extraction faces of a plurality of light emitting elements,
after which the translucent member and the light reflecting members
are cut between the light emitting elements with a blade, laser
irradiation, or the like, and the light blocking members are
formed, or (4) after a plurality of light emitting elements have
been joined on the base material, the light reflecting members may
cover the side faces of the light emitting elements, and light
blocking members may be formed, after which a single translucent
member is formed on the light extraction faces of the light
emitting elements.
[0076] When the side faces of the translucent members are covered
by the light reflecting members and/or the light blocking members,
the upper faces of the translucent members preferably are on the
same plane, or substantially on the same plane, as the upper faces
of the light reflecting members and/or the light blocking members.
It is particularly preferable for the upper faces of the
translucent members to lie on the same plane as the upper faces of
the light reflecting members and the light blocking members. This
more effectively prevents interference between light rays emitted
from the side faces of the translucent members. Alternatively, the
interference of light with respect to adjacent, unlit light
emitting elements can be more effectively prevented.
[0077] There are no particular restrictions on the thickness of the
translucent members, but an example is about 50 to 300 .mu.m.
[0078] The upper faces of the translucent members can be formed in
a uneven shape, as a curved face, as a lens shape, or any of
various other shapes, and the lower faces are preferably parallel
to the light extraction faces of the light emitting elements.
[0079] There are no particular restrictions on the material
constituting the translucent members, but examples include a resin,
a glass, an inorganic material, a cut plate from an ingot of
monocrystals or polycrystals of fluorescent material or sinter of
fluorescent material powder, or another such material, and a sinter
of a mixture of a fluorescent powder with a resin, a glass, an
inorganic material, etc. The higher is the transparency, the more
readily will the light be reflected at the boundary with the light
reflecting members, which increases the brightness.
[0080] Examples of the fluorescent material which allows to obtain
white light in combination with a blue light emitting element
include a YAG (Yttrium Aluminum Garnet)-based fluorescent material,
a BOS (Barium ortho-Silicate)-based fluorescent material or the
like. When such fluorescent material is contained in the
translucent member, the fluorescent material is preferably
contained in an amount of 5 to 50 wt %.
[0081] The translucent members are joined so as to cover the upper
faces (light extraction faces) of the light emitting elements. This
joining can be accomplished, for example, by compression bonding,
sintering, bonding with a known adhesive agent such as epoxy or
silicone, bonding with an organic adhesive agent with a high
refractive index, or bonding with low-melting point glass.
[0082] For example, if the translucent members contain a
fluorescent material, a light emitting device that emits light in a
light bulb color conforming to JIS standards can be obtained by
adding a red fluorescent material to an adhesive agent that joins
these translucent members to blue light emitting elements.
[0083] Base Material 14
[0084] As shown in FIGS. 1A and 1B, the light emitting elements 11
are installed on the base material 14 in the light emitting
device.
[0085] The base material can be any one that is known in this field
and used for the mounting of light emitting elements and so forth.
Examples of the base material include a substrate formed by an
insulating member such as glass epoxy, resin, ceramic or the like,
a metal member formed the insulating member and the like. Among
them, those using a ceramic having high heat resistance and weather
resistance are preferred. Examples of the ceramic material include
alumina, aluminum nitride, mullite and the like, and the ceramic
materials may combine with the insulating material such as BT
resin, glass epoxy, epoxy resin or the like.
[0086] The base material usually has a wiring pattern (see 15 in
FIG. 1A and elsewhere) on its surface that is connected to the
light emitting elements.
[0087] The light emitting device is such that a plurality of light
emitting elements are independently driven according to the wiring
pattern of the base material and its power supply control, etc.
This independent flash control can be any method that is known in
this field and ordinarily used.
[0088] Embedding Material 19
[0089] As discussed above, an embedding material is preferably
disposed between the base material and the light emitting elements
when the light emitting elements are joined on the base material
(see 19 in FIG. 7). Disposing an embedding material between the
base material and the light emitting elements improves heat
dissipation and absorbs stress produced by the difference in the
coefficients of thermal expansion between the light emitting
elements and the base material.
[0090] The embedding material may be disposed only directly under
the light emitting elements, or may extend from directly under the
light emitting elements to between the light emitting elements, or
may be in contact with part of the side faces of the light emitting
elements. The embedding material can have a film thickness of about
several microns to several hundred microns at the thickest
point.
[0091] The embedding material is also known as an underfill, which
usually includes a resin. The resin that is contained is preferably
a light reflecting resin. Using a light reflecting resin allows the
light emitted downward from the light emitting elements to be
reflected, which results in a better light flux.
[0092] It is preferable for the embedding material to be made of a
material whose elasticity and linear expansion are both lower than
those of the light reflecting members, because there will be less
resin expansion and contraction stress at the junctions between the
light emitting elements and the base material, and the electrical
junction reliability will be enhanced. Also, it is preferable to
use a material with high mechanical strength for the light
reflecting members, and for the embedding material to be completely
covered by the light reflecting members so that the embedding
material is not exposed on the outside. This ensures good
durability with respect to external stress at the light emitting
elements and the embedding material portions. If the embedding
material and the light reflecting members are made of different
materials, the embedding material is preferably cured prior to
filling of the light reflecting members. This prevents the resins
from mixing together, so the performance of each resin is not
compromised.
[0093] The embedding material can be formed from a silicone resin
composition, a modified silicone resin composition, an epoxy resin
composition, a modified epoxy resin composition, an acrylic resin
composition, etc., or a resin containing a silicone resin, an epoxy
resin, a urea resin, a fluororesin, or a hybrid resin containing
one or more of those resins as a base polymer and a light
reflecting material. Among them, a resin containing silicone resin,
epoxy resin, etc., as a base polymer is preferable. Here, the base
polymer means a resin having the most component weight among the
embedding material.
[0094] Examples of the light reflecting material include titanium
dioxide, silicon dioxide, zirconium dioxide, potassium titanate,
alumina, aluminum nitride, boron nitride, mullite, or the like.
This allows the light from the light emitting element to be
reflected efficiently.
[0095] The material constituting the embedding material may be a
single type, or two or more types may be combined. This allows
adjustment of the coefficient of linear expansion of the resin
and/or the reflectivity of light.
[0096] Method for Manufacturing Light Emitting Device
[0097] As shown in FIGS. 2A and 2B, first the base material 14
having a wiring pattern 15 on its surface is provided.
[0098] A plurality of light emitting elements 11 are arranged and
electrically connected on the wiring pattern 15 of the base
material 14.
[0099] Next, translucent members 18 are joined on the upper faces
of the light emitting elements 11, and the side faces of the
translucent members 18 and the light emitting elements 11 are
covered by the light reflecting members 12. The upper faces of the
light reflecting members 12 lie on substantially the same plane as
the light extraction faces (i.e., upper faces) of the translucent
members 18.
[0100] After this, a blade or the like is used to cut the light
reflecting members 12 between the light emitting elements 11 from
one end to the other, forming grooves 16 between the light emitting
elements 11. The cutting here may be done to a depth that matches
the surface of the base material 14, but it does not necessarily
have to reach the surface of the base material 14.
[0101] Next, as shown in FIG. 3, a frame 17 that integrally
surrounds both ends of the grooves 16 is formed in the light
reflecting members 12. The frame 17 here can be formed using the
same resin as the light reflecting resin, for example.
[0102] After this, as shown in FIGS. 4A and 4B, the inside of the
frame 17 is filled with a light blocking resin. The light blocking
resin used here fills the inside of the grooves 16 formed in the
light reflecting members 12 by capillary action. This allows the
light blocking members 13 to be formed. The viscosity of the light
blocking resin is preferably adjusted so that everything in the
width direction and the depth direction inside the grooves 16 can
be embedded.
[0103] Then, as shown in FIGS. 4A and 4B, the flame 17 and the
light blocking resin outside the grooves 16 is removed as needed.
The removal here can be accomplished by etching, for example. The
upper faces of the light blocking members 13 lie substantially on
the same plane as the light extraction faces of the translucent
members 18 and the upper faces of the light reflecting members
12.
Embodiment 1
[0104] As shown in FIGS. 1A and 1B, the light emitting device in
Embodiment 1 has five light emitting elements 11 that are arranged
and connected in the column direction on the base material 14
having the wiring pattern 15 on its surface, the light reflecting
members 12, and the light blocking members 13 disposed between the
light reflecting members 12.
[0105] The base material 14 has a wiring pattern including
titanium, platinum, or gold vapor deposited on the surface of an
aluminum nitride plate having a thermal conductivity of about 170
W/mK.
[0106] The light emitting elements 11 measure 1.0.times.1.0 mm and
0.11 mm thick, and include a semiconductor layer laminated on a
sapphire substrate, with a pair of electrodes formed on the same
side.
[0107] These light emitting elements 11 are flip-chip mounted on
the base material 14 with bumps composed of gold. Therefore, the
sapphire substrate is the light extraction face.
[0108] The upper faces of the light emitting elements 11 are
covered by the translucent members 18 in the form of plate, which
are formed by mixing and sintering YAG and alumina, with an
adhesive agent composed of a silicone resin by using thermal
curing.
[0109] The distance between the light emitting elements 11 is about
0.3 mm, and the distance between the translucent members 18 is
about 0.2 mm.
[0110] The light reflecting members 12 cover the side faces of the
light emitting elements 11 and the translucent members 18 covering
the upper faces of the light emitting elements 11, and the outer
peripheries of these.
[0111] The light reflecting members 12 contain 30 wt % titanium
oxide in a silicone resin, and have a thermal conductivity of about
0.2 W/mK.
[0112] The width of the light reflecting members 12 between the
light emitting elements to the light blocking members 13 is about
70 .mu.m in plan view.
[0113] The upper faces of the light reflecting members 12 lie on
the same plane as the upper faces of the translucent members 18 on
the upper faces of the light emitting elements 11, and the
thickness at the thickest portion of the light reflecting members
12 is about 0.3 mm.
[0114] The light blocking members 13 disposed between the light
reflecting members 12 are formed from a mixture of 5 wt % carbon
black and 30 wt % titanium oxide in a silicone resin.
[0115] The light blocking members 13 are formed from one side to
the other along opposing sides of the light reflecting members 12,
and their width is about 60 .mu.m in plan view. The lower faces of
the light blocking members 13 reach near the surface of the base
material 14, and the depth is about 0.28 mm.
[0116] The upper faces of the light blocking members 13 lie on the
same plane as the upper faces of the light reflecting members 12
and the translucent members 18 on the upper faces of the light
emitting elements 11.
[0117] Brightness Evaluation
[0118] This light emitting device 10 was used to measure the
brightness distribution.
[0119] For the sake of comparison, a light emitting device was
produced that was configured the same as the light emitting device
10, except that no light blocking members 13 were used.
[0120] As shown in FIG. 5, the brightness distribution was measured
using the light emitting device 10 and a comparative light emitting
device each having two unlit light emitting elements 11b, one lit
light emitting element 11a sandwiched between the two unlit light
emitting elements 11b, and two adjacent light emitting elements,
and a relative comparison was made using a ProMetric
(PM-1423F-1).
[0121] With the comparative light emitting device, if we let 100 be
the brightness of the two adjacent lit light emitting elements, the
micro-emission level of the unlit light emitting element sandwiched
between the two lit light emitting elements was 0.6.
[0122] Meanwhile, the micro-emission level of the unlit light
emitting element with the light emitting device 10 in this
embodiment was approximately 50% of that in the comparative light
emitting device.
[0123] Thus, it was confirmed that with the light emitting device
in this embodiment, there is a more steep difference in brightness
between the emitting and non-emitting parts, and the resulting
light emitting device had good visibility and a good brightness
distribution.
Embodiment 2
[0124] As shown in FIG. 6, the light emitting device 20 in this
embodiment is configured substantially the same as the light
emitting device 20 in Embodiment 1, except that the translucent
members are not formed on the upper faces of the light emitting
elements 11, the sapphire substrate surface of the light emitting
elements is the light extraction face, and this light extraction
face lies on the same plane as the upper faces of the light
reflecting members 12 and the light blocking members 13.
[0125] This light emitting device 20 is similar to Embodiment 1 in
that it is a light emitting device with good visibility and a good
brightness distribution.
Embodiment 3
[0126] As shown in FIG. 7, the light emitting device 30 in this
embodiment is configured substantially the same as the light
emitting device 10 in Embodiment 1, except that an embedding
material 19 is formed between the light emitting elements 11 and
the base material 14, and the lower ends of grooves 23 are disposed
so as to substantially coincide with the surface of the embedding
material 19.
[0127] The embedding material 19 is formed by adding 30 wt %
titanium oxide to a silicone resin. The embedding material 19 is
formed by potting after the flip-chip mounting of the light
emitting elements 11 with bumps, and the formation of the
translucent members on the light extraction faces of the light
emitting elements 11.
[0128] This light emitting device 30 is similar to Embodiment 1 in
that it is a light emitting device with good visibility and a good
brightness distribution.
Embodiment 4
[0129] As shown in FIG. 8, the light emitting device 40 in this
embodiment is configured substantially the same as the light
emitting device 10 in Embodiment 1, except that the light blocking
members 13 are formed only partially between the light emitting
elements 11.
Embodiment 5
[0130] As shown in FIG. 9, the light emitting device 50 in this
embodiment is configured substantially the same as the light
emitting device 10 in Embodiment 1, except that the light emitting
elements 11 are disposed in 5 columns and 2 rows, light blocking
members 53 are formed between the light emitting elements 11 and
between the rows, and the light blocking members 53 are not
disposed between the light emitting elements 11 within the same
row, and that light reflecting members 52 and the pattern shape of
a wiring pattern 55 had by the base material 54 on its surface are
changed along with this layout of the light emitting elements
11.
[0131] Unlike in FIG. 4A, the light blocking members 53 with this
shape are such that a frame is formed on the left and right (the
row direction) of the light reflecting members 52 in the light
emitting device 50, and this frame is used to fill grooves formed
in the light reflecting members 52 with the light blocking members
by capillary action.
INDUSTRIAL APPLICABILITY
[0132] The light emitting device according to the present invention
can be used for various kinds of light sources, such as
illumination light sources, light sources for various kinds of
indicators, light sources for automobile use, light sources for
displays, back light sources for liquid crystal displays, light
sources for sensors, signals, automobile use, channel control
characters for channel boards.
[0133] As illustrated above, embodiments are described to give a
concrete form to technical ideas of a light emitting device
according to the present invention, the present invention is not
limited to the described embodiments of the present invention.
Also, obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings,
which are within the scope and spirit of the invention, and such
other modifications and variations are intended to be covered by
the following claims.
* * * * *