U.S. patent number RE47,891 [Application Number 15/161,885] was granted by the patent office on 2020-03-03 for emission device, surface light source device, display and light flux control member.
This patent grant is currently assigned to Enplas Corporation. The grantee listed for this patent is Enplas Corporation. Invention is credited to Shingo Ohkawa, Masao Yamaguchi.
View All Diagrams
United States Patent |
RE47,891 |
Yamaguchi , et al. |
March 3, 2020 |
Emission device, surface light source device, display and light
flux control member
Abstract
A display has a member irradiated by a surface light source
device comprising a light diffusion member and emission device. The
emission device is provided with a light flux control member having
a recess and light control emission face which is configurated so
as to satisfy Conditions 1 and 2 in a range at least covering a
half-intensity-angular-range. Light emitting element(s) may be
sealed. Condition 1 is that relation .theta.5/.theta.1>1 is
satisfied except for light emitted from a light emitting element
toward within an angular-neighbourhood of a standard optical axis
of the emission device, and Condition 2 is that value of
.theta.5/.theta.1 decreases gradually according to increasing of
.theta.1, where .theta.1 is an emission angle of any light at being
emitted from the light emitting element, and .theta.5 is an
emission angle of that light of .theta.1 at then being emitted from
the light control emission face of the light flux control
member.
Inventors: |
Yamaguchi; Masao (Kitamoto,
JP), Ohkawa; Shingo (Misato, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Enplas Corporation |
Kawaguchi-shi, Saitama |
N/A |
JP |
|
|
Assignee: |
Enplas Corporation (Saitama,
JP)
|
Family
ID: |
35520670 |
Appl.
No.: |
15/161,885 |
Filed: |
May 23, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
11235361 |
Sep 27, 2005 |
7348723 |
Mar 25, 2008 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Sep 27, 2004 [JP] |
|
|
2004-278888 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
33/58 (20130101); G02B 19/0066 (20130101); H01L
33/486 (20130101); G02F 1/133603 (20130101); H01L
25/0753 (20130101); G02B 3/04 (20130101); G02B
19/0014 (20130101); G02B 19/0061 (20130101); G02B
19/0066 (20130101); H01L 33/58 (20130101); F21V
5/048 (20130101); G02B 19/0071 (20130101); H01L
33/486 (20130101); H01L 25/0753 (20130101); G02B
19/0071 (20130101); G02B 3/04 (20130101); G02F
1/133603 (20130101); G02B 19/0061 (20130101); G02B
19/0014 (20130101); G02B 5/02 (20130101); F21Y
2115/10 (20160801); H01L 2924/00 (20130101); H01L
2924/0002 (20130101); G02F 1/133607 (20210101); F21Y
2115/10 (20160801); G02F 1/133607 (20210101); G02B
5/02 (20130101); F21V 5/048 (20130101); H01L
2924/0002 (20130101); H01L 2924/0002 (20130101); H01L
2924/00 (20130101) |
Current International
Class: |
H01L
25/075 (20060101); F21V 5/04 (20060101); H01L
33/58 (20100101); H01L 33/48 (20100101); G02B
19/00 (20060101); G02B 3/04 (20060101); G02B
5/02 (20060101); G02F 1/1335 (20060101) |
Field of
Search: |
;313/498,501,512
;362/311,331,307-309,335-338,340,222,223,326,257 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
8713875 |
|
Feb 1998 |
|
DE |
|
1213773 |
|
Jun 2002 |
|
EP |
|
1255132 |
|
Nov 2002 |
|
EP |
|
1653254 |
|
May 2006 |
|
EP |
|
58-152219 |
|
Sep 1983 |
|
JP |
|
59-226381 |
|
Dec 1984 |
|
JP |
|
59-226381 |
|
Dec 1984 |
|
JP |
|
61-063712 |
|
Apr 1986 |
|
JP |
|
63-6702 |
|
Jan 1988 |
|
JP |
|
63-006702 |
|
Jan 1988 |
|
JP |
|
02-052463 |
|
Apr 1990 |
|
JP |
|
2-306289 |
|
Dec 1990 |
|
JP |
|
2979961 |
|
Sep 1999 |
|
JP |
|
2000030521 |
|
Jan 2000 |
|
JP |
|
2000089694 |
|
Mar 2000 |
|
JP |
|
2001-250986 |
|
Sep 2001 |
|
JP |
|
2002-49326 |
|
Feb 2002 |
|
JP |
|
2002-049326 |
|
Feb 2002 |
|
JP |
|
2002-344027 |
|
Nov 2002 |
|
JP |
|
2002334607 |
|
Nov 2002 |
|
JP |
|
2003297127 |
|
Oct 2003 |
|
JP |
|
2003-331604 |
|
Nov 2003 |
|
JP |
|
565951 |
|
Dec 2003 |
|
TW |
|
01/083264 |
|
Nov 2001 |
|
WO |
|
02/081929 |
|
Oct 2002 |
|
WO |
|
2006/076899 |
|
Jul 2006 |
|
WO |
|
Other References
Utilizing Light-Emitting Diodes in Today's Energy Conscious World,
"Ledtronics, Inc. The Future of Light", issue date Jun. 15, 2000,
16 pages. cited by applicant.
|
Primary Examiner: Nguyen; Minh
Attorney, Agent or Firm: Brundidge & Stanger, P.C.
Claims
What is claimed is:
.[.1. An emission device comprising a light flux control member
provided with a recess and an light control emission face, and a
light emitting element accommodated in said recess, said light
emitting element emits light which is emitted from said light
control emission face after travelling within said light flux
control member, wherein said light control emission face is
configured so as to satisfy the following Conditions 1 and 2 for at
least light which is emitted toward within a
half-intensity-angular-range around a
maximum-intensity-emission-direction from said light emitting
element; Condition 1: Relation .theta.5/.theta.1>1 is satisfied
except for light emitted toward within an angular-neighborhood of a
standard optical axis of said emission device; Condition 2: Value
of .theta.5/.theta.1 decreases gradually according to increasing of
.theta.1; where .theta.1 is an emission angle of any light at being
emitted from said light emitting element, and .theta.5 is an
emission angle of that light of .theta.1 at then being emitted from
said light control emission face of said light flux control
member..].
.[.2. The emission device in accordance with claim 1, wherein said
recess provides a concave surface which is in contact with an light
emitting surface of said light emitting element..].
.[.3. The emission device in accordance with claim 1, wherein said
recess provides a concave surface and a gap is formed between said
concave surface and an light emitting surface of said light
emitting element..].
.[.4. The emission device in accordance with claim 1, 2 or 3,
wherein said light control emission face includes a first emission
face region crossing with said standard optical axis and a second
emission face region extending around said first emission face
region, said first and second emission face regions having a
connecting portion in which a point of inflection exists..].
.[.5. A surface light source device comprising an emission device
and a light diffusion member which diffuses and transmits light
from said emission device, wherein said emission device is an
emission device in accordance with claim 1, 2 or 3..].
.[.6. A surface light source device comprising an emission device
and a light diffusion member which diffuses and transmits light
from said emission device, wherein said emission device is an
emission device in accordance with claim 4..].
.[.7. The surface light source device comprising an emission device
and a light diffusion member which diffuses and transmits light
from said emission device, wherein said emission device is an
emission device in accordance with claim 5..].
.[.8. The surface light source device comprising an emission device
and a light diffusion member which diffuses and transmits light
from said emission device, wherein said emission device is an
emission device in accordance with claim 6..].
.[.9. The emission device in accordance with claim 1, wherein said
light emitting element is sealed by a sealing material so that
light emitted from said light emitting element impinges on said
light flux control member after transmitting through said sealing
material..].
.[.10. The emission device in accordance with claim 9, wherein said
recess provides a concave surface which is in contact with an outer
surface of said sealing material..].
.[.11. The emission device in accordance with claim 9, wherein said
recess provides a concave surface and a gap is formed between said
concave surface and an outer surface of said sealing
material..].
.[.12. The emission device in accordance with claim 9, 10 or 11,
wherein said light control emission face includes a first emission
face region crossing with said standard optical axis and a second
emission face region extending around said first emission face
region, said first and second emission face regions having a
connecting portion in which a point of inflection exists..].
.[.13. The surface light source device comprising an emission
device and a light diffusion member which diffuses and transmits
light from said emission device, wherein said emission device is an
emission device in accordance with claim 9, 10 or 11..].
.[.14. The surface light source device comprising an emission
device and a light diffusion member which diffuses and transmits
light from said emission device, wherein said emission device is an
emission device in accordance with claim 12..].
.[.15. The surface light source device comprising an emission
device and a light diffusion member which diffuses and transmits
light from said emission device, wherein said emission device is an
emission device in accordance with claim 13..].
.[.16. The surface light source device comprising an emission
device and a light diffusion member which diffuses and transmits
light from said emission device, wherein said emission device is an
emission device in accordance with claim 14..].
.[.17. A light flux control member provided with a recess for
accommodating a light emitting element, comprising: a light control
emission face for causing light coming from said light emitting
element after travelling within said light flux control member to
be emitted, wherein said light control emission face is configured
so as to satisfy the following Conditions 1 and 2 for at least
light which is emitted toward within a half-intensity-angular-range
around a maximum-intensity-emission-direction from said light
emitting element; Condition 1: Relation .theta.5/.theta.1 >1 is
satisfied except for light emitted toward within an
angular-neighborhood of a standard optical axis of said light flux
control member; Condition 2: Value of .theta.5/.theta.1 decreases
gradually according to increasing of .theta.1; where .theta.1 is an
emission angle of any light at being emitted from said light
emitting element, and .theta.5 is an emission angle of that light
of .theta.1 at then being emitted from said light control emission
face of said light flux control member..].
.[.18. The light flux control member in accordance with claim 17,
wherein said recess is a recess for accommodating a light emitting
element together with a sealing material that seals said light
emitting element..].
.Iadd.19. A surface light source device comprising: an emission
device unit comprising a substrate and emission devices disposed on
said substrate, each of said emission devices including a light
emitting element and a light flux control member for controlling a
light distribution of light emitted from said light emitting
element; and a diffuser disposed over said emission device unit,
wherein said light flux control member includes a light incidence
surface on which light emitted from said light emitting element is
incident, and an light control emission face which emits light
incident on said incidence surface, said light control emission
face is configured so as to satisfy the following Conditions 1 and
2 for at least light which is emitted toward within a
half-intensity-angular-range around a
maximum-intensity-emission-direction from said light emitting
element, and thereby the at least light which is emitted toward
within said half-intensity-angular-range around said
maximum-intensity-emission-direction from said light emitting
element is expanded smoothly; Condition 1: Relation
.theta.5/.theta.1>1 is satisfied except for light emitted toward
within an angular-neighborhood of a standard optical axis of said
emission device; Condition 2: Value of .theta.5/.theta.1 decreases
gradually according to increasing of .theta.1; where .theta.1 is an
emission angle of any light at being emitted from said light
emitting element, and .theta.5 is an emission angle of that light
of .theta.1 at then being emitted from said light control emission
face of said light flux control member, said emission devices are
disposed on said substrate at predetermined intervals so that light
from said emission devices adjacent to each other are mixed, said
diffuser is disposed over said emission device unit such that light
from said emission devices adjacent to each other are mixed between
said emission devices and said diffuser, and said light emitted
from said emission device is directly applied to the diffuser and
does not travel through another element disposed between said
emission device and said diffuser..Iaddend.
.Iadd.20. The surface light source device in accordance with claim
19, wherein said light control emission face has a substantially
circular shape when viewed along said standard optical
axis..Iaddend.
.Iadd.21. The surface light source device in accordance with claim
19, wherein said light control emission face includes a first
emission face region existing within a predetermined range from
said standard optical axis and a second emission face region
extending around said first emission face region, said first
emission face region having a concave shape being shaped like a
partially removed sphere, said first emission face region and
second emission face region having a connecting portion in which a
point of inflection exists..Iaddend.
.Iadd.22. The surface light source device in accordance with claim
21, wherein .theta.3 decreases gradually according to increasing of
.theta.1 in said first emission face region, and .theta.3 increases
gradually according to increasing of .theta.1 in said second
emission face region, where .theta.3 is an angle between a line
perpendicular to said standard optical axis and a line being a
tangent of said light control emission face at a pass position at
which that light of .theta.1 is emitted from said light control
emission face..Iaddend.
.Iadd.23. The surface light source device in accordance with claim
19, wherein a gap is formed between said light incidence surface
and a light emitting surface of said light emitting
element..Iaddend.
.Iadd.24. The surface light source device in accordance with claim
19, wherein said light emitting element is sealed by a sealing
material..Iaddend.
.Iadd.25. The surface light source device in accordance with claim
24, wherein a gap is formed between said light incidence surface
and an outer surface of said sealing material..Iaddend.
.Iadd.26. The surface light source device in accordance with claim
19, wherein said emission devices are disposed on said substrate at
predetermined intervals such that light from said emission devices
adjacent to each other across said emission device are mixed
between said emission devices and said diffuser..Iaddend.
.Iadd.27. The emission device to be used in said surface light
source device in accordance with claim 19..Iaddend.
.Iadd.28. A display comprising: said surface light source device in
accordance with claim 19; and a display member to be irradiated
with light emitted from said surface light source device..Iaddend.
Description
.Iadd.CROSS REFERENCE TO RELATED APPLICATIONS.Iaddend.
.Iadd.This application is a reissue application of U.S. application
Ser. No. 11/235,361, filed Sep. 27, 2005, now U.S. Pat. No.
7,348,723..Iaddend.
BACKGROUND
1. Field of Invention
The present invention relates to an emission device, surface light
source device, display, and light flux control member used therein.
The present invention is applied, for instance, to backlighting
arrangements for liquid crystal display panel, various illumination
devices for general uses such as interior illumination, or displays
composed of illumination device and member to be irradiated.
2. Related Art
A surface light source device employing a plurality of LEDs (light
emitting diodes) as point-like light sources has been known as an
illuminating means for a LCD monitor display of a personal computer
or TV set. A plate-like light flux control member having roughly
the same shape as that of a LCD panel is employed in the surface
light source device, being provided with a plurality of LEDs
arranged like a matrix at the back side. The LEDs emit light which
is incident to a back face of the light flux control member and
travels within the light flux control member to an emission face
opposite to the back face, being outputted from the emission face
toward a LCD panel to be backlighted. Prior arts like this have
been disclosed in the following documents.
<Prior Art 1>
This is found disclosed in Tokkai 2002-49326 (JP-A 2002-49326),
according to which surface light source device 10 is provided with
microlens array 102. Individual microlenses are arranged in
one-to-one correspondence to a plurality of LEDs 101, as shown in
FIG. 12. Light from LEDs 101 is outputted in a direction
perpendicular to a plane (upward) via microlens array 102.
<Prior Art 2>
This is found disclosed in Tokkaisho 59-226381(JP-A 1984-226381),
according to which emission display device 103 is provided with LED
104, concave lens 105 and convex lens 106, as shown in FIG. 13.
Light from LED 104 is condensed by convex lens 106 after being
diverged by concave lens 105, being outputted in a direction
roughly parallel with an "optical axis" of LED 104. Please note
that "optical axis" is defined as a light travelling direction at a
center of three-dimensional light flux emitted from a point-like
light source (LED 104).
<Prior Art 3>
This is found disclosed in Tokkaisho 63-6702 (JP-A 1988-6702),
providing display 107 having LED(s) 108, as shown in FIG. 14. Light
from LED 108 is condensed by condenser lens 110 and directed
forward, then being diverged by diverging lens 111.
<Prior Art 4>
Another prior art provides display 121 as shown in FIG. 15. Display
121 is provided with a plurality of LED chips 125, light diffusion
member 126 and member 127 (such as LCD panel) irradiated by light
transmitted through light diffusion member 126. LED chips 125, each
of which is composed of LED 124 and light flux control member 123
fixed on an emission surface side, are arranged at intervals, for
instance, at regular intervals. Light flux control member 123 has
hemisphere-like emission surface 122. Object 127 is supplied with
light emitted from LED chips 125 and then transmitted through light
diffusion member 126.
However, the above prior arts involve problems as follows.
(1) Prior Art 1;
Surface light source device 100 has a portion at which
configuration of microlens array 102 varies discontinuously. The
portion is located between LEDs 101 adjacent to each other.
Emission intensity changes sharply at this discontinuity portion,
with the result that a conspicuous unevenness in brightness appears
around boundary regions between individual microlenses of microlens
array 102.
(2) Prior Art 2;
It is difficult to say that concave lenses 105 in emission display
103 are coupled with each other continuously to form a plane.
Further to this, convex lenses 106 are scarcely coupled with each
other continuously to form a plane. Therefore, a member of a large
area to be illuminated, such as large-screen liquid crystal display
panel, is hardly supplied with uniform illumination light.
(3) Prior Art 3;
With display 107, light from LED 108 is diverged by diverging lens
111 after being condensed by condenser lens 110. This wil reduce
unevenness in brightness as compared with Prior Art 1. However, a
sufficient mixing of light fluxes from LEDs 108 adjacent to each
other is hardly expected, with the result that unevenness in
emission color between individual LEDs 108 tends to be
conspicuous.
(4) Prior Art 4;
With display 121, wave-shaped brightness unevenness appears
strikingly corresponding to LEDs 124 arranged at intervals, as
shown in FIG. 10. This brings dark areas corresponding to absence
of LED 124 between LED s 124, making uniform illumination
difficult. In addition, Prior Art 4 tends to give a locally large
brightness area in the vicinity of optical axis L of LED 125.
Therefore, it is difficult to male light from LEDs 124 adjacent to
each other mixed well, with the result that unevenness in emission
color between individual LEDs 124 tends to be conspicuous.
OBJECT AND SUMMARY OF INVENTION
An object of the present invention is to enables an emission
device, surface light source device employing the emission device,
and display employing the surface light source device to provide
uniform area illumination free from conspicuous brightness
unevenness.
Another object of the present invention is to enable the above
devices, if they employ single point-like light source such as LED,
to expand light from the point-like light source smoothly and
effectively to a desirable range.
A still another object of the present invention is to avoid a
surface light source device employing a plurality of point-like
light sources such as LEDs, and display employing the surface light
source device from showing a conspicuous unevenness of emission
color.
Another object of the present invention
A further object of the present invention is to provide a light
flux control member employable in the above devices.
In the first place, the present invention is applied to an emission
device comprising a light flux control member provided with a
recess and an light control emission face, and a light emitting
element accommodated in said recess, wherein the light emitting
element emits light which is emitted from the light control
emission face after travelling within said light flux control
member.
According to a feature of the present invention, said light control
emission face is configured so as to satisfy the following
Conditions 1 and 2 for at least light which is emitted toward
within a half-intensity-angular-range around a
maximum-intensity-emission-direction from said light emitting
element. Condition 1: Relation .theta.5/.theta.1>1 is satisfied
except for light emitted toward within an angular-neighborhood of a
standard optical axis of said emission device; Condition 2: Value
of .theta.5/.theta.1 decreases gradually according to increasing of
.theta.1;
where .theta.1 is an emission angle of any light at being emitted
from said light emitting element, and .theta.5 is an emission angle
of that light of .theta.1 at then being emitted from said light
control emission face of said light flux control member.
Please note that the above angular-neighborhood of the standard
optical axis of the emission device, in other words, an
angular-neighborhood of optical axis L shown in FIG. 3, preferably
corresponds to within a range of .theta.1 from about -5.degree. to
about +5.degree..
The light control emission face provides a concave surface which
may be in contact with an light emitting surface of the light
emitting element. Alternatively, a gap may be formed between the
concave surface and the light emitting surface of the light
emitting element.
The light control emission face may include a first emission face
region crossing with the standard optical axis and a second
emission face region extending around the first emission face
region, and first and second emission face regions may have a
connecting portion such that a point of inflection exists
therein.
In addition, the present invention provides a surface light source
device comprising the above emission device and a light diffusion
member which diffuses and transmits light from the emission device.
The present invention also provides a display comprising the
surface light source device and a member illuminated by the surface
light source device.
In every case mentioned above, the light emitting element may be
sealed by a sealing material so that light emitted from the light
emitting element impinges on the light flux control member after
transmitting through the sealing material. The recess may provide a
concave surface which is in contact with an outer surface of the
sealing material. Alternatively, a gap may be formed between the
concave surface and the outer surface of the sealing material.
Further, the present invention is applied to a light flux control
member provided with a recess for accommodating a light emitting
element. A light flux control member according to the present
invention has a light control emission face for causing light
coming from the light emitting element after travelling within the
light flux control member to be emitted, wherein the light control
emission face is configured so as to satisfy the following
Conditions 1 and 2 for at least light which is emitted toward
within a half-intensity-angular-range around a
maximum-intensity-emission-direction from the light emitting
element;
Condition 1: Relation .theta.5/.theta.1>1 is satisfied except
for light emitted toward within an angular-neighborhood of a
standard optical axis of the light flux control member;
Condition 2: Value of .theta.5/.theta.1 decreases gradually
according to increasing of .theta.1;
where .theta.1 is an emission angle of any light at being emitted
from the light emitting element, and .theta.5 is an emission angle
of that light of .theta.1 at then being emitted from the light
control emission face of the light flux control member.
The recess may be a recess for accommodating a light emitting
element together with a sealing material that seals the light
emitting element.
According to the present invention, the light emitting element
outputs a light flux which the light control emission face of the
light flux control member causes to be expanded smoothly and
effectively to a broad angular range. As a result, a broad range
illumination is realized through the light flux control member.
In addition, if a plurality of light emitting elements are
arranged, light fluxes from the respective light emitting elements
are mixed with each other easily by transmitting through the light
flux control member. This brings a less conspicuous emission color
unevenness even if the respective emission colors are not even,
providing a high quality illumination.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a plan view illustrating a surface light source device
and display to which the present invention is applicable, with a
member to be illuminated and light diffusion member being not
shown;
FIG. 2 is a cross section view of the display shown in FIG. 1 along
X1-X1;
FIG. 3 is a partial cross section view of the display shown in FIG.
1 along a plane on which an optical axis of a LED extends, giving a
partial and enlarged illustration of FIG. 2;
FIGS. 4A, 4B and 4C show first mode of light flux control member in
details, FIG. 4a being a plan view, FIG. 4b being a cross section
view along X2-X2 in FIG. 4a, and FIG. 4c being an exploded view of
the light flux control member and LED;
FIG. 5 is a diagram illustrating a relation between LED-emission
angle (emission angle of light emitting element emission angle, in
general) .theta.1 and emission angle .theta.5 of a light flux
control member (control-member-emission angle);
FIG. 6 is a diagram illustrating a relation between LED-emission
angle .theta.1 and lens-face inclination angle .theta.3;
FIGS. 7A, 7B and 7C show a second mode of light flux control member
in details, FIG. 7a being a plan view, FIG. 7b being a cross
section view along X3-X3 in FIG. 7A, and FIG. 7C being an exploded
view of the light flux control member and LED;
FIG. 8 shows a cross section view of a display employing a light
flux control member of a third mode, in an illustration manner the
same as that of FIG. 2;
FIGS. 9A to 9F illustrate first, second, third, forth, fifth and
sixth examples of light diffusion members, respectively, and FIG.
9G is an enlarged partial view of display;
FIG. 10 is a diagram illustrating distributions of emission
intensity from a light diffusion member display to which the
present invention is applied, together with an emission intensity
distribution of an example for comparison (Prior Art 4);
FIGS. 11A and 11B illustrate a color-emission type surface light
source device and display using the same to which the present
invention is applicable, FIG. 11A being a plan view, with a member
to be illuminated and light diffusion member being not shown and
FIG. 11B being a cross section view along X4-X4 in FIG. 11A;
FIG. 12 is a diagram illustrating an outlined structure of Prior
Art 1;
FIG. 13 is a diagram illustrating an outlined structure of Prior
Art 2;
FIG. 14 is a diagram illustrating an outlined structure of Prior
Art 3; and,
FIG. 15 is a diagram illustrating a cross section of a display in
accordance with Prior Art 4.
EMBODIMENT
<Outlined Structure of Surface Light Source Device and
Display>
FIGS. 1 to 3 show display 1 and surface light source device 2
included in display 1. FIG. 1 is a plan view illustrating surface
light source device 2, with a member such as LCD panel 3 to be
illuminated being not shown. FIG. 2 is an outlined cross section
view of display 1 along X1-X1 in FIG. 1. FIG. 3 is a partial cross
section view of display 1 along a plane on which standard optical
axis L of light emitting element 4 extends, giving a partial and
enlarged illustration of FIG. 2 in order to illustrate a
configuration of light control emission face 6 of light flux
control member 5.
Standard optical axis L is defined as a light traveling direction
at a center of three-dimensional emission flux from an emission
device. Please note that this term (i.e. standard optical axis) is
used for a light flux control member in the same way in the instant
specification. That is, a light traveling direction at a center of
three-dimensional emission flux from an light flux control member
is called "standard optical axis of light flux control member".
In this embodiment handles a typical case where an optical axis of
light emitting element 4 (i.e. a light traveling direction at a
center of three-dimensional emission flux from light emitting
element 4) accords with standard optical axis L. Accordingly,
standard optical axis L is called simply "optical axis L"
occasionally.
Referring to FIGS. 1 to 3, display 1 comprises light diffusion
member 7 shaped like a rectangle, point-like light emitting
elements 4 and member (display panel) 3 to irradiated.
Light emitting elements 4 are disposed at generally regular
intervals with pitch P. Light emitting elements 4 may be sealed by
sealing material 9 as illustrated, so that light emitting element 4
and sealing material 9 compose LED 19.
Surface light source device 2 is composed of point-like light
sources (light emitting elements 4 or LEDs 19), flux control member
5 and light diffusion member 7, in which an emission device is
composed of point-like light sources (light emitting elements 4 or
LEDs 19) and flux control member 5.
<Light Flux Control Member>
(First Mode)
Light flux control member 5 is made of transparent resin such as
PMMA (polymethyl methacrylate), PC (polycarbonate) or EP (epoxy
resin), or transparent glass, being shaped as shown in FIGS. 1 to 3
with a circle-like planar shape.
Referring to FIG. 4B, light flux control member 5 has
hemisphere-like recess 10 on a back side, namely, on a lower side
in FIG. 4B. Recess 10 is in contact with light emitting surface 8
of light emitting element 4, being located at a center of a back
side of light flux control member 5 as shown in FIGS. 4B and 4C.
Light emitting surface 8 is shaped like a hemisphere, fitting
hemisphere-like recess 10.
Light flux control member 5 has a flat portion 11 on the back side.
Flat portion 11 is stuck and fixed to mounting substrate 12 of
light emitting element 4. Recess 10 is stuck and fixed to light
emitting surface 8 of light emitting element 4.
Light flux control member 5 has light control emission face 6 on an
outer side. Light control emission face 6 comprises first emission
face region 6a and second emission face region 6b extending around
first emission face region 6a.
Optical axis L crosses with first emission face region 6a at a
crossing point which provides a center of range in which first
emission face region 6a extends.
First emission face region 6a has a gently curved downward-convex
configuration as shown in FIG. 4B, being shaped like a partially
removed sphere providing a concave configuration.
Second emission face region 6b is formed continuously adjacent to
first emission face region 6a as shown in FIG. 4B, having a gently
curved upward-convex configuration. It can be said that second
emission face region 6b is shaped like a ring-band-like-disk
extending around first emission face region 6a.
Second emission face region 6b is connected to first emission face
region 6a smoothly, providing a connecting portion (boundary
portion) in which a point of inflection Po. Third emission face
region 6c is formed on an outside of second emission face region 6b
as to connecting second emission face region 6b to flat portion 11
on the back side, as shown in FIG. 4B.
FIG. 4B shows a generally straight slope-like cross section of
third emission face region 6c. However, this is merely an example.
That is, curved configuration may be employed so far as uniform and
broad emission from light flux control member 5 is not spoiled.
Here, angles .delta.1 and .delta.2 are defined as follows.
.delta.1; angle of connection point Pa of emission face regions 6b
and 6c with respect to optical axis L .delta.2; angle of inflection
point Po with respect to optical axis L
In FIG. 3, reference plane C is defined a horizontal plane
perpendicular to optical axis L of light emitting element 4. Line A
is defined as a line extends parallel with reference plane C as to
pass position Px at which light beam H is emitted from light
control emission face 6 after travelling within light flux control
member 5. Px is a crossing point of light control emission face 6
and light beam H.
In FIG. 3, line B is a tangent of configuration of light control
emission face 6, making angle .theta.3 at position Px with respect
to line A. Light beam H makes emission angle .theta.5 with respect
to light control emission face 6 after travelling within light flux
control member 5. Emission angle .theta.5 is defined as angle of
light beam H on emitting from light control emission face 6 with
respect to optical axis L.
An angular range called "half-intensity-angular-range" is
introduced. In general, light emitting element 4 has the maximum
emission intensity direction along optical axis L. The maximum
emission intensity direction is also a direction along a normal of
reference plane C. Emission intensity of light emitting element 4
falls gradually according to an increasing angular deviation from
the maximum emission intensity direction.
Under such situation, "half-intensity-angular-range" is defined as
an angular range extending up to an intensity-falling of 50% as
compared with the maximum emission intensity from the maximum
emission intensity direction.
Configuration of light control emission face 6 shown in FIG. 3
satisfies the following Conditions 1 and 2 for "light which is
emitted toward within a certain angular range at least including
half-intensity-angular-range from light emitting element 4". It is
noted that this certain angular range is exemplarily shown in FIG.
5 as an angular range of .theta.1<.delta.1. Condition 1:
Relation .theta.5/.theta.1>1 is satisfied except for light
emitted toward within an angular-neighborhood of a standard optical
axis L of emission device 29. Condition 2; Value of
.theta.5/.theta.1 falls gradually according to increasing of
.theta.1.
Please note that .theta.1 is an emission angle of any light at
being emitted from light emitting element 5, and .theta.5 is an
emission angle of that light of .theta.1 at then being emitted from
light control emission face 6.
It is noted that "angular-neighborhood of a standard optical axis
L" (angular-neighborhood of optical axis L in FIG. 3) is preferably
an angular range of .theta.1 within 5.degree. (within .+-.5.degree.
from the direction of optical axis L).
Referring to FIG. 5, dotted line 15 shows a relation of
(.theta.5/.theta.1)=1. If degree of light diverging of light flux
control member 5 is expressed by coefficient .alpha., .theta.5 is
expressed by Formula 1 under a condition such that
.theta.1<.delta.1, and .theta.3 is expressed by Formula 2 as
follows.
.theta.5=[1+{(.delta.1-.theta.1).times..alpha./.delta.1}].times..theta.1,
Formula 1) where .theta.1<.delta.1. .theta.3=tan.sup.-1 {(sin
.theta.5-nsin .theta.1)/(cos .theta.5-ncos .theta.1)}, (Formula 2)
where n is refractive index of light flux control member.
Such calculated angle .theta.3 decreases gradually according to
increasing of .theta.1 until .theta.1=.delta.2 is satisfied from an
angular neighbourhood of optical axis L as shown by curve 16 in
FIG. 6. In a range of .theta.1>.delta.2, .theta.3 increases
gradually according to increasing of .theta.1. If
.theta.1=.delta.2, .theta.3=.theta.1.
General operations light flux control member 5 having light control
emission face 6 are as follows.
As illustrated in FIGS. 2 and 3, light beam H generally
representing emission from light emitting element 4 enters into
light flux control member 5, then traveling within light flux
control member 5 and reaches light control emission face 6 to be
emitted toward an ambient medium (air) according to Snell's
Law.
This emission from light control emission face 5 in accordance with
the present invention occurs more uniformly toward an illumination
range, and broader and smoother angular expansion is realized as
compared with a case of emission from conventional hemisphere light
flux control member 23. In other words, locally strong emission
toward just above portion of light emitting element 4.
(Example of First Mode)
In the next place, an example of emission device 29 employing light
flux control member 5 of first mode is described by referring to
FIGS. 1 to 4. Shapes and others of first and second emission face
regions 6a, 6b are designed depending on various factors such as
the followings.
(a): Emission characteristics of light emitting element 4,
especially, angular extension represented by
half-intensity-angular-range.
(b): Thickness d of light flux control member 5 along a direction
of optical axis L, especially, distance d1 from emission portion 4a
of light emitting element 4 to light control emission face 6 along
a direction of optical axis L.
(c): Arrangement pitch p of light emitting element 4.
(d): Outer diameter Do of light flux control member 5.
(e): Distance L1 from light control emission face 6 to light
diffusion member 7 along a direction of optical axis L.
(f): Refractive index n of light flux control member 5.
(g): Configuration of incidence concave face (Configuration of
concave surface provided by recess 10).
(h): Refractive index n of medium (air or sealing material) through
which light of light emitting element 4 transmits before impinging
on light flux control member 5.
According to an example, light flux control member 5 has a
hemisphere-like recess, being made of transparent resin of
refractive index n=1.49, with L1=13.89 mm, p=24.25 mm, d=3.31 mm,
d1=2.11 mm and Do=7.85 mm. Medium between light flux control member
5 and light emitting element 4 has the same refractive index as
that of light flux control member 5.
This light flux control member 5 has first and second emission face
regions 6a, 6b which form a connection portion at which angle
.theta.1 satisfies .theta.1=.delta.2=16.degree.. In addition,
second and third emission face regions 6b, 6c form a connection
portion at which angle .theta.1 satisfies
.theta.1=.delta.1=85.degree.. It can be said that third emission
face region 6c is provided by rotating tangent of second emission
face regions 6b by 360.degree. around optical axis L.
A range of .theta.1.ltoreq..delta.2 corresponds to first emission
face region 6a and range of
.delta.2.ltoreq..theta.1.ltoreq..delta.1 corresponds to second
emission face region 6b, and range of .delta.1.ltoreq..theta.1
corresponds to third emission face region 6c, in FIG. 4B.
It is noted that, if sealing material 9 has refractive index
substantially the same as that of light flux control member 5,
light beam H from light emitting element 4 reaches light control
emission face 6 without undergoing refraction. For instance, if
sealing material 9 is made of the same transparent resin or glass,
this is realized.
However, the present invention is not limited by this mode. Sealing
material 9 may have refractive index different from that of light
flux control member 5. It is noted that absence of sealing material
9 air occupies a gap between light emitting element 4 and light
flux control member 5.
(Example of Second Mode)
FIG. 7 shows emission device 29 employing light flux control member
5 of second mode in accordance with the present invention. This
light flux control member 5 is generally the same as that of first
mode except structure for engaging with light emitting element
4.
As shown in FIG. 7, light flux control member 5 is suitable for a
case where LED 19 has a rectangular cross section and light
emitting face 17. Rectangular recess 18 formed at a center portion
on the back side contacts with rectangular light emitting face 17.
Light flux control member 5 has flat portion 11 on the back side.
Flat portion 11 is stuck and fixed to mounting substrate 12 for
light emitting element 4 and recess 18 is stuck and fixed to light
emitting surface 17.
Light flux control member 5 of this mode structured as
above-described has functions generally the same as those of light
flux control member 5 of first mode.
It is noted that, although FIG. 7 shows that sealing material 9
sealing light emitting element 4 (LED 19) has a rectangular cross
section, this does not limit the scope of the present invention.
For instance, LED 19 may shaped like hemisphere or others.
(Example of Third Mode)
FIG. 8 shows light flux control member 5 of third mode in
accordance with the present invention. This light flux control
member 5 is generally the same as that of first mode except
structure for engaging with light emitting element 4.
As shown in FIG. 8, light flux control member 5 of third mode has a
hemisphere-like incidence surface (concave surface of recess 23) 20
engaging with light emitting element 4 with a gap. Incidence
surface 20 is formed on the upper side with respect to reference
line C in FIG. 8.
Hemisphere-like incidence surface 20 has cylinder-like
LED-accommodation-portion 21 engaging with light emitting element 4
with a gap on the lower side in FIG. 8.
Light emitting element 4 is stuck and fixed to substrate 22. On the
other hand, light flux control member 5 has flat portion 11 on the
lower side and flat portion 11 is stuck and fixed to 22 after light
emitting element 4 is accommodated in LED-accommodation-portion 21
and positioned at a predetermined location by an action like
applying capping to light emitting element 4.
Light flux control member 5 structured as above-described causes
light of light emitting element 4 to enter into light flux control
member 5 through hemisphere-like incidence surface 20 after
transmitting through an air layer. After propagating in light flux
control member 5, emission from light control emission face 6
occurs.
In this mode, light control is performed under consideration of
conditions such as difference of the air layer and light flux
control member 5, and the concave configuration of incidence
face.
Light flux control member 5 of this mode has functions generally
the same as those of light flux control member 5 of first mode.
It is noted that the above-described second and third modes may be
modified by using only light emitting element 4 instead of LED
19.
Emission device 29 employing light flux control member 5 of first
or second mode may be modified as to omit sealing material 9.
Alternatively, sealing material 9 may be used as light flux control
member 5. Sealing material 9 may be stuck and fixed to light flux
control member 5 or contacted with light flux control member 5
without sticking and fixing.
(Other Modes)
Other modifications such as followings are allowed.
(1): Matting may be applied to light control emission face 6 of
light flux control member 5 of the above-described first, second or
third mode so that light is diffused on emitting from light control
emission face 6.
(2): Light flux control member 5 of the above-described first or
second mode may be made of material containing light diffusible
articles such as silicone articles or titanium oxide articles.
<Light Diffusion Member>
FIGS. 9a to 9f are side views of light diffusion members 7 in
accordance with to first to sixth examples, respectively.
Each light diffusion member 7 is a sheet-like or plate-like member
made of light well-permeable resin such as PMMA (polymethyl
methacrylate) or PC (polycarbonate), having an area size generally
equal to that of member 3 to be illuminated such as LCD panel,
advertising display panel.
Light diffusion member 6 shown in FIG. 9A employs sheet-like base
material 7a to both faces of which processing for giving light
diffusion ability, such as emboss-processing or bead-processing, is
applied. Thus both faces of light diffusion member 7 are provided
with fine uneven configurations 7b.
Light diffusion member 7 shown in FIG. 9B employs sheet-like base
material 7a to both faces of which processing for giving light
diffusion ability, such as emboss-processing or bead-processing, is
applied. Thus both faces of light diffusion member 7 are provided
with fine uneven configurations 7b. In addition, light diffusive
material 7c is dispersed within base material 7a.
Light diffusion member 7 shown in FIG. 9C employs sheet-like base
material 7a to only an inner face of which processing for giving
light diffusion ability, such as emboss-processing or
bead-processing, is applied to form a fine uneven configuration 7b.
It is noted that the inner face of light diffusion member 7 is a
face directed to light flux control member 4. In addition, other
face of light diffusion member 7 is provided with a great number of
repeated prismatic projections 7d extending along a direction
perpendicular to the paper surface.
Light diffusion member 7 shown in FIG. 9D is the same as one shown
in FIG. 9C except that light diffusive material 7c is dispersed
within base material 7a.
In the same manner as the case of FIG. 9C, processing such as
emboss-processing or bead-processing is applied to one face
directed to light flux control member 4 to form a fine uneven
configuration 7b. The other face of light diffusion member 7 is
provided with a great number of repeated prismatic projections 7d
extending along a direction perpendicular to the paper surface.
Each of prismatic projections 7d shown in FIGS. 9C and 9D is shaped
like triangle, for instance, like isosceles triangle.
Light diffusion member 7 shown in FIG. 9E employs sheet-like base
material 7a on an emission side face of which circular-cone-like
projections 7e for are formed to cause light transmitted through
base material 7a to be diffused.
Light diffusion member 7 shown in FIG. 9F employs sheet-like base
material 7a on an emission side face of which pyramid-like (such as
triangle-pyramid-like, quadrangle-pyramid-like or
hexangle-pyramid-like) projections 7f for are formed to cause light
transmitted through base material 7a to be diffused.
Every light diffusion member 7 as above transmits and diffuses
light emitted from light control emission face 6 of light flux
control member 5, causing member 3 to be illuminated uniformly.
It is noted that every light diffusion member 7 as above may be
mounted on an inner face directed to light flux control member 5 of
member 3 to be illuminated, or alternatively, may be interposed
between light flux control member 5 and member 3 to be illuminated,
with being separated from member 3.
<Emission Intensity from Light Diffusion Member>
FIG. 10 is a diagram illustrating distributions of emission
intensity from light diffusion member 7, together with an emission
intensity distribution of an example for comparison (Prior Art
4).
(Case of Single LED Arrangement)
In FIG. 10, curve A shows a distribution of emission intensity in a
case where light flux control member 5 in accordance with the
present invention is disposed, giving light intensity of one light
emitting element 4 after transmitting through light flux control
member 5 and light diffusion member 7. Curve B shows a distribution
of emission intensity in the prior art case of FIG. 15 where light
flux control member 123 is disposed, giving light intensity of one
LED 124 after transmitting through light flux control member 123
and light diffusion member 126.
Comparing curve A (using light flux control member 5) with curve B
(using light flux control member 123), the followings are
understood.
That is, Curve A shows a gently rising mountain-like changing while
Curve B shows a sharp rising in the vicinity of optical axis L.
Curve A gives smaller intensities in the vicinity of optical axis L
as compared with Curve B, but giving grater intensities in
positions far from optical axis L as compared with Curve B.
This tells that light flux control member 5 in accordance with the
present invention provides more uniformly distributed illumination
as compared with the prior art.
(Case of Multi-LED Arrangement)
In FIG. 10, curve C shows a distribution of emission intensity in a
case where light flux control members 5 in accordance with the
present invention are disposed corresponding to a plurality of
light emitting elements 4, giving light intensity of light emitting
elements 4 after transmitting through light flux control members 5
and light diffusion member 7 (See FIGS. 1 and 2).
In FIG. 10, Curve D shows a distribution of emission intensity in
the prior art case of FIG. 15 where light flux control members 123
corresponding to a plurality of LEDs 124 are disposed, giving light
intensity of one LEDs 124 after transmitting through light flux
control members 123 and light diffusion member 126.
Comparing curve C (using light flux control members 5) with curve D
(using light flux control members 123), the followings are
understood.
That is, Curve D shows a striking wave/-like repeating brightness
unevenness corresponding to discretely arranged LEDs 124. To the
contrary, Curve C hardly shows such a striking brightness
unevenness.
This is supposed to be brought by two facts. One fact is that light
from each light emitting element 4 is free from locally strong
emission toward a direction along optical axis L and spread widely,
as Curve A shows. Another fact is that light beams from light
emitting elements 4 adjacent to each other are mixed mutually well,
with the result a small bright unevenness is realized on an
emission face side of light diffusion ] member 7.
As described above, the present invention can provide uniform and
well-mixed illumination as shown in FIG. 10.
Well-mixed illumination enables high quality illumination to be
realized even if a plurality of light emitting elements 4, such as
white light emitting LEDs), have different intensities or emission
tones. For example, even if some emit remarkably yellowish light
and others emit slightly yellowish light, uniformly yellowish
illumination is obtained.
<Surface Light Source Device and Display for Color
Illuminations>
FIGS. 11A and 11B illustrate color-emission type surface light
source device 2 and display 1 using the same to which the present
invention is applicable. FIG. 11A is a plan view, with a member to
be illuminated and light diffusion member being not shown and FIG.
11B is a cross section view along X4-X4 in FIG. 11A.
As illustrated, light emitting elements 4R, 4G and 4B emitting
light of colors R, G and B are disposed alternately. Light from
these light emitting elements is emitted from light control
emission face 6 of light flux control member 5 to irradiate member
3 to be irradiated after transmitting through light diffusion
member 7.
Not only in a case all light emitting elements 4R, 4G and 4B are
lighted on, but also in a case any of light emitting elements 4R,
ones 4G and 4B are lighted on, light of each light emitting element
can reach far positions over adjacent ones, being mixed well there.
This brings a uniform brightness.
It is noted that emission device 29 in accordance with the present
invention has third emission face region 6c at which two or more
emission devices 29 are connected with each other. If pitch of LED
19 or light emitting element 4 is small, this makes assembling for
obtaining surface light source device 2 easy.
If large emission device 29 is produced, one light flux control
member may be assembled from a plurality of blocks each of which
corresponds to one light emitting element 4.
Further, although above description handles cases optical axis L of
light from light emitting element 4 accord a normal direction as
shown in FIG. 3, this does not limit the scope of the present
invention,
For example, the present invention can be applied to cases where
optical axis L of light from light emitting element 4 is slightly
different from a normal direction due to unevenness in quality of
light emitting element 4 or assembling errors of components
including light emitting element 4, allowing to provide generally
the same functions as those of embodiments described above.
* * * * *