U.S. patent application number 10/916525 was filed with the patent office on 2005-12-01 for light emitting diode device.
This patent application is currently assigned to Samsung Electro-Mechanics Co., Ltd.. Invention is credited to Hahm, Hun Joo, Jeong, Young June, Kim, Hyung Suk, Park, Jung Kyu, Park, Young Sam.
Application Number | 20050263785 10/916525 |
Document ID | / |
Family ID | 35424207 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050263785 |
Kind Code |
A1 |
Kim, Hyung Suk ; et
al. |
December 1, 2005 |
LIGHT EMITTING DIODE DEVICE
Abstract
Disclosed herein is a light emitting diode (LED) device. The
light emitting diode device comprises a package formed with a
terminal for applying an electrical signal, one or more LED chips
mounted on the package such that the LED chips are electrically
connected to the terminal, a lens formed to surround the LED chips
on the package for changing path of light emitted from the LED
chips to the horizontal direction with the difference of the
refraction rates of the media, and a reflector formed on the lens
for reflecting the light, emitted above the lens without being
refracted in the horizontal direction at the lens, to the
horizontal direction. The LED device reflects the light, which is
deviated from the optical design range of the lens and emitted
above the lens, back to the lens, thereby preventing the hot spot
from being generated, and enhancing horizontal emission efficiency
of the light.
Inventors: |
Kim, Hyung Suk; (Suwon,
KR) ; Park, Young Sam; (Seoul, KR) ; Hahm, Hun
Joo; (Sungnam, KR) ; Park, Jung Kyu; (Suwon,
KR) ; Jeong, Young June; (Suwon, KR) |
Correspondence
Address: |
LOWE HAUPTMAN GILMAN AND BERNER, LLP
1700 DIAGONAL ROAD
SUITE 300 /310
ALEXANDRIA
VA
22314
US
|
Assignee: |
Samsung Electro-Mechanics Co.,
Ltd.
Suwon
KR
|
Family ID: |
35424207 |
Appl. No.: |
10/916525 |
Filed: |
August 12, 2004 |
Current U.S.
Class: |
257/100 ;
257/E33.059; 257/E33.072 |
Current CPC
Class: |
H01L 33/54 20130101;
H01L 33/60 20130101 |
Class at
Publication: |
257/100 |
International
Class: |
H01L 033/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2004 |
KR |
2004-37763 |
Claims
What is claimed is:
1. A light emitting diode device, comprising: a package formed with
a terminal for applying an electrical signal; one or more LED chips
mounted on the package such that the LED chips are electrically
connected to the terminal; a lens formed to surround the LED chips
on the package for changing path of light emitted from the LED
chips to the horizontal direction using differences of refraction
rates of media; and a reflector formed on the lens for reflecting
the light, emitted above the lens without being refracted in the
horizontal direction at the lens, to the horizontal direction.
2. The light emitting diode device as set forth in claim 1, wherein
the lens is formed of a transparent or translucent resin.
3. The light emitting diode device as set forth in claim 1, wherein
the lens comprises: a first reflective surface inclined at an angle
allowing total reflection of the light emitted upwardly from the
LED chips, with reference to an axis extending in the perpendicular
direction from the middle of the one or more LED chips or from the
center of the LED chip; and a second reflective surface extending
from the first reflective surface to the top surface of the package
at an angle refracting the light emitted from the LED chips
approximately to the horizontal direction.
4. The light emitting diode device as set forth in claim 1, wherein
the reflector is formed by applying a highly reflective metallic
material on a bowl-shaped plastic base having a diameter larger
than that of the lens.
5. The light emitting diode device as set forth in claim 1, wherein
the lens is formed at an upper portion of the lens with a concave
groove, and the reflector is formed at a lower portion of the
reflector with a protrusion, such that the groove and the
protrusion correspond to each other, forming a pair, so that the
lens can be engaged with the reflector by inserting the protrusion
into the concave groove.
6. The light emitting diode device as set forth in claim 1, wherein
the package is formed with a heat dissipation structure for
dissipating heat generated from the LED chips.
7. The light emitting diode device as set forth in claim 3, wherein
the reflector comprises: a third reflective surface defined at the
bottom surface of the reflector contacting the lens for reflecting
the light, passing through the first reflective surface without
being totally reflected at the first reflective surface of the
lens, below the reflector; and a fourth reflective surface
obliquely defined from the third reflective surface for reflecting
the light, emitted above the lens without being refracted at the
second reflective surface of the lens in the horizontal direction,
to the horizontal direction.
8. The light emitting diode device as set forth in claim 3, wherein
the light emitting diode device is defined with an air gap having a
predetermined shape surrounded by the first reflective surface of
the lens and the reflector.
9. The light emitting diode device as set forth in claim 3, wherein
the light emitting diode device is defined with a space having a
predetermined shape surrounded by the first reflective surface of
the lens and the reflector, and the space is filled with a material
having a refraction rate higher than that of the lens but lower
than that of air.
10. The light emitting diode device as set forth in claim 7,
wherein the reflector further comprises a fifth reflective surface
defined at the top surface connected to the fourth reflective
surface for reflecting the light, returned to the top surface of
the reflector, above the light emitting device diode.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a light emitting diode
device, which can be used for a light source of a backlight in a
liquid crystal display (LCD), and more particularly to a light
emitting diode device, which completely changes the path of light
emitted upwardly at the center of the light emitting diode to the
horizontal direction, thereby enhancing horizontal emission
efficiency, together with preventing a hot spot.
[0003] 2. Description of the Related Art
[0004] A light emitting diode (LED) is a semiconductor light
emitting device, which emits various colors of light, with light
sources being constituted by compound semiconductors made of
various materials, such as GaAs, AlGaAs, GaN, InGaN and AlGaInP.
Particularly, with the advent of highly efficient three primary
colors (red, blue, green) and white LEDs realized by a nitride
having excellent physical and chemical properties, the LEDs have
more diverse applications, and thus have been spotlighted as a
light source of a backlight for a liquid crystal display (LCD).
[0005] As a standard for determining characteristics of the LEDs,
colors, brightness, intensity of light, and the like of the LEDs
can be used, and these are determined primarily by the material of
the compound semiconductor for the LEDs, and secondarily by a
package structure for mounting LED chips.
[0006] Particularly, in the case of a horizontal emitting type LED
device, which is used for a direct illumination type backlight
unit, it is important to transmit the light generated from LED
chips in the horizontal direction without light loss.
[0007] FIG. 1 is a cross sectional view illustrating a conventional
horizontal emitting type LED device.
[0008] Referring to FIG. 1, the conventional horizontal emitting
type LED device comprises a package 11 made of a plastic material
and formed with a terminal 11a for inputting or outputting an
electrical signal, an LED chip 14 mounted on the frame 11, and a
lens 13 coupled to the frame 11 at the top surface of the frame 11
while being structured such that light generated from the LED chip
14 can be reflected to the horizontal direction.
[0009] The lens 13 is defined with a lower reflective surface A
contacting the package 11, a first reflective surface B smoothly
curved to have a semi-spherical shape from the lower reflective
surface A, a second reflective surface C inclined outwardly from an
upper portion of the first reflective surface B with reference to a
central axis 10 of the lens 13, and a third reflective surface D
inclined downwardly from the second reflective surface C to the
central axis of the lens 10, in which the central axis 10 is
established with reference to the LED chip 12.
[0010] The light emitted from the LED chip 12 collides against the
reflective surfaces A to D defined as described above, is
refracted, and then emitted.
[0011] The package 11 is provided for protecting the LED chip 12
from the external environment. The package is made of a plastic
material, and structured such that the LED chip 12 can be protected
from the external environment. The package 11 comprises a heat sink
structure or means for dissipating heat generated when the LED chip
12 emits light, in addition to the terminal 11a for transmitting
the electrical signal when being mounted thereon.
[0012] In the case where the horizontal emitting type LED device is
used as the light source of the backlight, the backlight comprises
an LED array provided as a linear light source by arranging the
horizontal emitting type LED devices in a line on a predetermined
printed circuit board, and a reflection plate provided at both
sides of the LED array such that the light emitted in the
horizontal direction is reflected to the perpendicular direction
through the reflection plate.
[0013] Meanwhile, the conventional horizontal type light emitting
diode device shown in FIG. 1 utilizes differences in the refraction
rates of media, which the light passes through, that is, an LED
chip 12, a lens 13, and air. For instance, the LED chip 12 is
formed of a gallium-based compound with a refraction rate of about
2.4. The lens 13 is formed of a transparent or translucent resin
with a refraction rate of about 1.5, and air has a refraction rate
of 1. Accordingly, the light generated from the LED chip 12
sequentially passes through the media from the lower refraction
rate to the higher refraction rate while being refracted or
reflected according to an incident angle at the interface between
the media.
[0014] Thus, the lens 13 is optically designed such that the light
emitted from the LED chip 12 in any direction is refracted in the
horizontal direction.
[0015] Meanwhile, in the light emitting diode device as described
above, there sometimes occurs a problem in that a portion of the
light incident at an angle deviated from an optical design range is
emitted directly above the lens without being refracted at the
reflective surfaces. Such a problem can become more apparent in the
case where a large LED chip is mounted on the light emitting diode
device, thereby further reducing horizontal emission efficiency of
the light emitting diode device. In order to shield the light
emitted in the perpendicular direction, structure of the lens 13
must become more complicated, thereby complicating the light
emitting diode device.
[0016] Moreover, when the backlight unit of the LCD is realized
using the light emitting diode device as described above, due to
the light emitted in the perpendicular direction from the LCD
device, there occurs a hot spot on a screen of the LCD.
Accordingly, in order to prevent the hot spot, a separate sheet for
preventing the hot spot is required for the backlight unit.
SUMMARY OF THE INVENTION
[0017] The present invention has been made in view of the above
problems, and it is an object of the present invention to provide a
light emitting diode device, which completely changes the path of
light emitted upwardly at the center of the light emitting diode
device to the horizontal direction, thereby enhancing horizontal
emission efficiency together with preventing a hot spot.
[0018] In accordance with one aspect of the present invention, the
above and other objects can be accomplished by the provision of a
light emitting diode device, comprising: a package formed with a
terminal for applying an electrical signal; one or more LED chips
mounted on the package such that the LED chips are electrically
connected to the terminal; a lens formed to surround the LED chips
on the package for changing path of light emitted from the LED
chips to the horizontal direction using the differences of
refraction rates of the media; and a reflector formed on the lens
for reflecting the light, emitted above the lens without being
refracted in the horizontal direction by the lens, to the
horizontal direction. The light emitting diode device completely
shields the light emitted above the lens, and changes the path of
light in the perfectly horizontal direction, thereby enhancing
horizontal emission efficiency of the light, and absolutely
preventing a hot spot from being generated when using the liquid
emitting diode device for the backlight unit of the liquid crystal
display.
[0019] The lens may be formed of a transparent or translucent
resin. Further, the lens may comprise a first reflective surface
inclined at an angle allowing total reflection of the light emitted
upwardly from the LED chips, with reference to an axis extending in
the perpendicular direction from the middle of the LED chips or
from the center of the LED chip; and a second reflective surface
extending from the first reflective surface to the top surface of
the package at an angle refracting the light emitted from the LED
chips approximately in the horizontal direction.
[0020] The reflector may be formed by applying a highly reflective
metallic material to a bowl-shaped plastic base having a diameter
larger than that of the lens.
[0021] Further, the lens may be formed at an upper portion of the
lens with a concave groove and the reflector may be formed at a
lower portion of the reflector with a protrusion, such that the
groove and the protrusion correspond to each other, forming a pair,
so that the lens can be engaged with the reflector by inserting the
protrusion into the concave groove.
[0022] Further, the reflector may comprise: a third reflective
surface defined at the bottom surface of the reflector contacting
the lens for reflecting the light, passing through the first
reflective surface without being totally reflected at the first
reflective surface of the lens, below the reflector; and a fourth
reflective surface obliquely defined from the third reflective
surface for reflecting the light, emitted above the lens without
being refracted at the second reflective surface of the lens in the
horizontal direction, to the horizontal direction. The reflector
may further comprises a fifth reflective surface defined at the top
surface connected to the fourth reflective surface for reflecting
the light, returned to the top surface of the reflector, above the
light emitting device diode.
[0023] The light emitting diode device may be defined with an air
gap having a predetermined shape surrounded by the first reflective
surface of the lens and the reflector.
[0024] The light emitting diode device may be defined with a space
having a predetermined shape surrounded by the first reflective
surface of the lens and the reflector, and the space may be filled
with a material having a refraction rate higher than that of the
lens but lower than that of air.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0026] FIG. 1 is a cross sectional view illustrating a conventional
light emitting diode device;
[0027] FIG. 2 is a cross sectional view illustrating a light
emitting diode device according to the present invention;
[0028] FIG. 3 is an exploded perspective view illustrating the
light emitting diode device according to the present invention;
and
[0029] FIG. 4 is a diagram of the path of light in the light
emitting diode device according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Now preferred embodiments of the present invention will be
described in detail with reference to the accompanying drawings so
that those skilled in the art may easily understand and repeat the
present invention.
[0031] FIG. 2 is a cross sectional view illustrating a light
emitting diode device according to the present invention, and FIG.
3 is an exploded perspective view illustrating the light emitting
diode device according to the present invention.
[0032] Referring to FIGS. 2 and 3, a light emitting diode device
comprises a package 21 formed with a terminal for applying an
electrical signal, one or more LED chips 22 mounted on the package
21, a lens 23 formed to surround the LED chips at an upper portion
of the package 21 for changing the path of light emitted from the
LED chips 21 to the horizontal direction, and a reflector 24 for
reflecting the light, emitted above the lens 23 without being
refracted in the horizontal direction at the lens 23, to the
horizontal direction.
[0033] First, the package 21 is structured such that the LED chips
22 can be protected from the external environment while being
easily mounted thereon. The package 21 may be made of, for example,
a plastic material, and may function to dissipate heat generated by
the LED chips 22 as well as to electrically connect to other
components at the outside. That is, the package 21 is formed with a
lead frame or the terminal for electrically connecting to the other
components at the outside thereof, and formed, at a portion to be
mounted with the LED chips, with a heat sink made of a material
having high thermal conductivity or having a structure of high
thermal conductivity, which transmits the heat to a lower portion
thereof. Moreover, the package 21 may be mounted with two or more
LED chips 22, and in this case, the package 21 may comprise a
board, with a printed circuit pattern for transmitting the
electrical signal formed thereon, and the board may be made of
aluminum in order to increase the heat dissipation
characteristics.
[0034] The lens 23 is made of, for example, a transparent or
translucent material having a refraction rate, which is lower than
that of the LED chip 22 but higher than that of air, so that the
light can be refracted at an interface between these materials in
the horizontal direction due to the difference of the diffraction
rate between adjacent media. That is, the lens 23 is optically
designed such that the light emitted from the LED chips 22 in any
direction can be refracted in the horizontal direction at the
surface of the lens 23 contacting the air.
[0035] For instance, as shown in FIGS. 2 and 4, the lens 23
comprises: a first reflective surface E inclined such that the
light emitted upwardly from the LED chips 22 can be incident
thereon within a critical angle with reference to an axis extending
in the perpendicular direction from the middle of the LED chips 22
or from the center of the LED chip 22; and a second reflective
surface F extending from the first reflective surface to the top
surface of the package at an angle, which refracts the light
emitted from the LED chips 22, into the air, approximately in the
horizontal direction.
[0036] The lens 23 is defined, at an upper portion thereof, with a
concave groove having a cone-shape at the center of the groove by
the first reflective surface.
[0037] The reflector 24 formed on the lens 23 may be formed by
coating a highly reflective metallic material on the surface of a
bowl-shaped base, which has a diameter larger than that of the lens
23.
[0038] The reflector 24 comprises: a third reflective surface H,
defined at the bottom surface of the reflector 24 contacting the
lens 23, for reflecting the light, passing through the first
reflective surface without being totally reflected at the first
reflective surface of the lens 23, below the reflector 24; and a
fourth reflective surface I, obliquely defined from the third
reflective surface, for reflecting the light, emitted above the
lens without being refracted at the second reflective surface of
the lens 23 in the horizontal direction, in the horizontal
direction.
[0039] The reflector 24 further comprises a fifth reflective
surface J, defined at the top surface connected to the fourth
reflective surface I, for reflecting the light, returned to the top
surface of the reflector 24, above the light emitting device
diode.
[0040] As shown in FIG. 3, the lens 23 is formed at an upper
portion thereof with a concave groove, and the reflector 24 is
formed at a lower portion of the reflector 24 with a protrusion,
such that the groove and the protrusion correspond to each other,
forming a pair, so that the lens 23 can be engaged with the
reflector 24 by inserting the protrusion into the concave groove.
As a result, there is an effect in that assembly process of the
lens and the reflector is simplified.
[0041] In the above structure of the lens and the reflector, the
light emitted diode device is defined with a space surrounded by
the first reflective surface of the lens 23 and the reflector 24.
Alternatively, an air gap may be provided, instead of the space.
The space may be filled with a material having a refraction rate,
which is higher than that of the lens 23 but lower than that of the
air.
[0042] FIG. 4 is a diagram showing the path of light in the light
emitting diode device according to the present invention.
[0043] As shown in FIG. 4, the light, colliding against the second
reflective surface F after being emitted from the LED chips 22, is
refracted at the second reflective surface F, and is then emitted
to the air in the horizontal direction. Further, the light,
arriving at the first reflective surface E after being emitted from
the LED chips 22, is bent toward the second reflective surface F
while being totally reflected at the first reflective surface E,
and is then emitted to the air in the horizontal direction after
being refracted when passing through the second refractive surface
F. At this point, the light, which is not incident on the first
reflective surface E within the critical angle, passes through the
first reflective surface E, and is emitted above the lens 23.
However, the light is totally reflected at the third reflective
surface H of the reflector 24 on the lens, so that the light is
incident into the lens 23, and is refracted at the second
reflective surface F, thereby being emitted to the air
approximately in the horizontal direction. Here, among the light
passing through the second reflective surface F of the lens 23, the
light, emitted above the lens 23 without being refracted in the
horizontal direction, is reflected while colliding against the
fourth reflective surface I of the reflector 24, thereby having its
path changed to the horizontal direction.
[0044] That is, the light is completely prevented from being
emitted in the perpendicular direction in the light emitting diode
device of the present invention, and all the light generated from
the LED chip 22 can be directed in the horizontal direction,
thereby completely preventing the hot spot from being
generated.
[0045] Further, even though a portion of the light is deviated from
the design range due to an increase in size of the LED chip 22 and
is then not refracted at the lens 23 in the horizontal direction,
the portion of the light can also be emitted in the absolutely
horizontal direction, thereby enhancing horizontal emission
efficiency of the device.
[0046] Additionally, the reflector 24 is provided with the fifth
reflective surface J, which is formed by applying the highly
reflective material on the top surface of the reflector 24, so that
when the LED device is employed as the light source for the
backlight unit of the liquid crystal display, the fifth reflective
surface J also reflects the light, refracted to the top surface of
the reflector 24 from the outside of the reflector, above the
reflector, thereby providing uniform light emission efficiency over
the entire screen of the liquid crystal display.
[0047] As is apparent from the above description, there are
advantageous effects in that the LED device according to the
present invention reflects the light, which is deviated from the
optical design range of the lens and emitted above the lens, back
to the lens, thereby preventing the hot spot from being generated.
Further, the path of the light emitted above the lens is changed to
the horizontal direction, thereby maximizing the horizontal
emission efficiency of the LED device.
[0048] Moreover, when the LED device is used for the light source
of the backlight unit, a separate sheet is not required for
preventing the hot spot from being generated in the backlight unit,
thereby simplifying the construction of the backlight unit, and
enhancing uniform vertical light emission efficiency over the
entire screen.
[0049] It should be understood that the embodiments and the
accompanying drawings as described above have been described for
illustrative purposes and the present invention is limited only by
the following claims. Further, those skilled in the art will
appreciate that various modifications, additions and substitutions
are allowed without departing from the scope and spirit of the
invention as set forth in the accompanying claims.
* * * * *