U.S. patent number RE48,207 [Application Number 15/395,223] was granted by the patent office on 2020-09-15 for display apparatus.
This patent grant is currently assigned to LG ELECTRONICS INC.. The grantee listed for this patent is LG ELECTRONICS INC.. Invention is credited to Juyoung Joung, Wondo Kee, Kyungjoon Lee, Uihyung Lee.
United States Patent |
RE48,207 |
Lee , et al. |
September 15, 2020 |
Display apparatus
Abstract
Provided is a display apparatus. The display apparatus may
include a display panel and a backlight provided adjacent the
display panel. The backlight may include an optical sheet provided
adjacent the display panel, a reflector provided a prescribed
distance from the optical sheet, at least one light emitting device
provided adjacent the reflector, and a lens provided over a
corresponding the light emitting device. The lens may include a
lower recess formed on a bottom surface of the lens and provided a
prescribed distance over the light emitting device, and an upper
recess formed on a top surface of the lens and provided to
vertically overlap the bottom recess. The lower recess may include
an upper surface that extends from the side surface and having a
prescribed shape and curvature. The upper recess may also include a
lower surface having a prescribed shape and curvature.
Inventors: |
Lee; Kyungjoon (Seoul,
KR), Lee; Uihyung (Seoul, KR), Joung;
Juyoung (Seoul, KR), Kee; Wondo (Seoul,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
N/A |
KR |
|
|
Assignee: |
LG ELECTRONICS INC. (Seoul,
KR)
|
Family
ID: |
48874100 |
Appl.
No.: |
15/395,223 |
Filed: |
December 30, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
14013427 |
Aug 29, 2013 |
9297519 |
Mar 29, 2016 |
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Foreign Application Priority Data
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Apr 15, 2013 [KR] |
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10-2013-0040735 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F21V
13/04 (20130101); G02F 1/133603 (20130101); G02B
19/0028 (20130101); G02B 19/0071 (20130101); G02F
1/133606 (20130101); G02F 1/133606 (20130101); G02F
1/133603 (20130101); G02B 19/0061 (20130101); G02B
19/0028 (20130101); G02F 1/133607 (20210101); H01L
33/58 (20130101); G02F 1/133607 (20210101); G02B
19/0071 (20130101); G02B 19/0061 (20130101); H01L
33/58 (20130101); F21V 13/04 (20130101) |
Current International
Class: |
F21V
13/04 (20060101); H01L 33/58 (20100101); G02F
1/1335 (20060101); G02F 1/13357 (20060101); G02B
19/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1783523 |
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Jun 2006 |
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CN |
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102282416 |
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Dec 2011 |
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CN |
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2012-517037 |
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Jul 2012 |
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JP |
|
10-2006-0111266 |
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Oct 2006 |
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KR |
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10-2012-0011185 |
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Feb 2012 |
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KR |
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10-2012-0011185 |
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Feb 2012 |
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KR |
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10-2013-0081868 |
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Jul 2013 |
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KR |
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2008-37449 |
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Sep 2008 |
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TW |
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WO 2012/132872 |
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Oct 2012 |
|
WO |
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WO 2012/132872 |
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Oct 2012 |
|
WO |
|
Other References
Chinese Office Action dated Sep. 30, 2016 issued in Application No.
201310392431.2. cited by applicant .
U.S. Office Action dated Aug. 6, 2015 issued in co-pending U.S.
Appl. No. 14/013,427. cited by applicant .
Korean Office Action dated Aug. 20, 2019 issued in Application
10-2013-0040735. cited by applicant .
European Search Report issued in Application No. 13003645.2 dated
Oct. 31, 2014. cited by applicant.
|
Primary Examiner: Bonshock; Dennis G
Attorney, Agent or Firm: KED & Associates LLP
Claims
What is claimed is:
1. A display apparatus comprising: a display panel; and a backlight
provided adjacent the display panel, wherein the backlight
includes: an optical sheet provided adjacent the display panel, a
reflector provided a prescribed distance from the optical sheet, at
least one light emitting device provided adjacent the reflector,
and a lens provided over a corresponding the light emitting device,
wherein the lens includes: a lower recess formed on a bottom
surface of the lens and provided a prescribed distance over the
light emitting device, and an upper recess formed on a top surface
of the lens and provided to vertically overlap the bottom recess,
.Iadd.wherein the upper recess has a convex surface; .Iaddend.
wherein the lower recess has an oval shape and includes: a side
surface that extends vertically from the bottom surface, and a
first upper surface that extends from the side surface at a first
prescribed angle relative to the side surface, the first upper
surface having a convex curvature .Iadd.and a vertex formed in a
region of the first upper surface away from the side surface,
wherein the first upper surface is convex to extend toward the
light emitting device, and wherein the vertex is formed on the
first upper surface at a highest point of the lower recess, wherein
the lower recess further includes: a second upper surface that
extends from the side surface, and a third upper surface
symmetrical to the second upper surface and extending to the second
upper surface from an opposite side of the lower
recess.Iaddend..
.[.2. The display apparatus of claim 1, wherein the first upper
surface extends from the side surface to form a vertex a prescribed
distance above the bottom surface..].
.[.3. The display apparatus of claim 2, wherein the lower recess
includes a second upper surface that extends from the side surface
at a second prescribed angle relative to the side surface, and a
third upper surface symmetrical to the second upper surface and
extending to the second upper surface from an opposite side of the
lower recess..].
4. The display apparatus of claim .[.3.]. .Iadd.1.Iaddend., wherein
the second upper surface and the third upper surface have a concave
curvature.
5. The display apparatus of claim 4, wherein the second upper
surface and the third upper surface intersect at a prescribed angle
relative to each other parallel to a long axis of the lower
recess.
6. The display apparatus of claim 5, wherein the vertex of the
first upper surface is adjacent to the first and second upper
surfaces where the first and second surfaces intersect.
7. The display apparatus of claim .[.3.]. .Iadd.1.Iaddend., wherein
the first upper surface extends from the side surface at a first
prescribed distance from the bottom surface and the second upper
surface extends from the side surface at a second prescribed
distance from the bottom surface, the second prescribed distance
being less than or equal to the first prescribed distance.
8. The display apparatus of claim 4, wherein .[.the oval shape
of.]. the lower recess includes a rectangular portion and round
portions provided at short ends of the rectangular portion, and
wherein the first upper surface extends from the side surface at
the round portion and the second and third surfaces extend from the
side surface at the rectangular portion.
9. The display apparatus of claim 1, wherein a length of the lower
recess is at least twice a width of the lower recess.
10. The display apparatus of claim 1, wherein the top surface of
the lens has a prescribed shape that is convex from an outer
circumferential edge to a center of the lens.
11. The display apparatus of claim 10, wherein the top surface
includes a plurality of sections corresponding to circular sectors
of the lens, and wherein adjacent sections have different heights
relative to each other.
12. The display apparatus according to claim 10, wherein the
curvature of the top surface is such that an angle of incidence of
light incident on the top surface of the lens from a corresponding
light emitting device is greater than or equal to 42.degree..
.[.13. A display apparatus comprising: a display panel; and a
backlight provided adjacent the display panel, wherein the
backlight includes an optical sheet provided adjacent the display
panel, a reflector provided a prescribed distance from the optical
sheet, at least one light emitting device provided adjacent the
reflector, and a lens provided over a corresponding the light
emitting device, wherein the lens includes a lower recess formed on
a bottom surface of the lens and provided a prescribed distance
over the light emitting device, and an upper recess formed on a top
surface of the lens and provided to vertically overlap the bottom
recess, wherein the upper recess has an oval shape and includes a
side surface that extends vertically from the top surface of the
lens, a first lower surface having a prescribed curvature and
extending from the side surface, and a second lower surface which
is symmetrical to the first lower surface and extending toward the
first lower surface from an opposite side of the upper
recess..].
.[.14. The display apparatus of claim 13, wherein the first lower
surface and the second lower surface have concave
curvatures..].
.[.15. The display apparatus of claim 13, wherein the first and
second lower surfaces intersect at a prescribed angle relative to
each other parallel to a long axis of the upper recess..].
.[.16. The display apparatus according to claim 15, wherein a depth
of the upper recess is greatest where the first and second lower
surfaces intersect..].
.[.17. The display apparatus according to claim 13, wherein a long
axis of the lower recess is parallel to a long axis of the upper
recess and provided to vertically overlap each other..].
.[.18. A display apparatus comprising: a display panel; and a
backlight provided adjacent the display panel, wherein the
backlight includes an optical sheet provided adjacent the display
panel, a reflector provided a prescribed distance from the optical
sheet, at least one light emitting device provided adjacent the
reflector, and a lens provided over a corresponding the light
emitting device, wherein the lens includes a lower recess formed on
a bottom surface of the lens and provided a prescribed distance
over the light emitting device, and an upper recess formed on a top
surface of the lens and provided to vertically overlap the bottom
recess, wherein a ratio of a depth of the upper recess to a radius
of the lens satisfies a following condition:
0.3.ltoreq.H/P.ltoreq.0.5, wherein H is a height from a top of the
lens to a lowermost point in the upper recess, and P is the radius
of the lens..].
.[.19. A display apparatus comprising: a display panel; a light
emitting device; a reflector provided adjacent to the light
emitting device; and a lens provided a prescribed distance over the
light emitting device and configured to distribute light to
illuminate the display panel, wherein the lens includes a recess
having an oval shape provided on a bottom surface of the lens, the
recess including a side surface that extends vertically a
prescribed distance from the bottom surface, and an upper surface
that extends from the side surface and having a convex curvature,
wherein a width of the upper surface gradually decreases into the
recess..].
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
This application .Iadd.is a Reissue Application of prior U.S. Pat.
No. 9,297,519 issued Mar. 29, 2016 (U.S. patent application Ser.
No. 14/013,427 filed Aug. 29, 2013, which .Iaddend.claims priority
under 35 U.S.C. .sctn.119 to Korean Application No. 10-2013-0040735
filed in Korea on Apr. 15, 2013, whose entire disclosure is hereby
incorporated by reference.
BACKGROUND
1. Field
The present disclosure relates to a display apparatus.
2. Background
As an information-oriented society develops, needs for diverse
forms of display apparatuses are increasing. Accordingly, research
has been carried out on various display apparatuses such as liquid
crystal display devices (LCDs), plasma display panels (PDPs),
electro luminescent displays (ELDs), vacuum fluorescent displays
(VFDs), and the like, which have been commercialized.
Among these, a liquid crystal panel of a liquid crystal display
(LCD) includes a liquid crystal layer, TFT substrates facing each
other with the liquid crystal layer therebetween, and a color
filter substrate. The liquid crystal panel may use light supplied
from a backlight unit to display an image because it does not emit
light.
A backlight unit using an isotropic lens has a structure in which
light sources are arranged in an orthogonal or honeycomb structure,
and the lens disperses light emitted from the light sources in a
form of isotropic light distribution. In such a structure, since
the pitch between the light sources increases as the number of
light sources is reduced, it is difficult to disperse light in the
form of circular isotropic light distribution using a secondary
lens.
The above references are incorporated by reference herein where
appropriate for appropriate teachings of additional or alternative
details, features and/or technical background.
BRIEF DESCRIPTION OF THE DRAWINGS
The embodiments will be described in detail with reference to the
following drawings in which like reference numerals refer to like
elements wherein:
FIG. 1 is an exploded perspective view illustrating a structure of
a display apparatus according to an embodiment;
FIG. 2 is a cross-sectional view of the display apparatus;
FIG. 3 is a perspective view illustrating an outer appearance of a
lens constituting a light emitting part according to an
embodiment;
FIG. 4 is a perspective cross-sectional view of the lens according
to an embodiment, taken alone line I'-I of FIG. 3;
FIG. 5 is a bottom perspective cross-sectional view of the lens
according to an embodiment, taken along line I'-I of FIG. 3;
FIG. 6 is a cross-sectional view of the lens according to an
embodiment, taken alone line I'-I of FIG. 3;
FIG. 7 is a perspective cross-sectional view of the lens according
to an embodiment, taken alone line II-II' of FIG. 3;
FIG. 8 is a cross-sectional view of the lens according to an
embodiment, taken alone line II-II' of FIG. 3;
FIG. 9 is a perspective cross-sectional view of the lens according
to an embodiment, taken alone lines I-I' and II-II' of FIG. 3;
FIG. 10 is a view comparing light reflective index profiles
realized in a lens according to a related art and a lens according
to an embodiment;
FIG. 11 is a cross-sectional view of a moving path of light
occurring on a top surface portion of a lens according to an
embodiment;
FIG. 12 is a view illustrating light distribution according to a
ratio of a long axis length to a short axis length in a recess
portion defined in a central portion of a bottom surface of a lens
according to an embodiment;
FIG. 13 is a view comparing light distribution occurring in a lens
in which an uneven portion is disposed on a central portion thereof
according to an embodiment and a lens in which an uneven portion is
not provided according to the related art; and
FIG. 14 is a simulation illustrating light distribution in a
backlight unit on which a plurality of light emitting parts
including a lens are mounted according to an embodiment.
DETAILED DESCRIPTION
In the following detailed description of the preferred embodiments,
reference is made to the accompanying drawings that form a part
hereof, and in which is shown by way of illustration specific
preferred embodiments in which the disclosure may be practiced.
These embodiments are described in sufficient detail to enable
those skilled in the art to practice the disclosure, and it is
understood that other embodiments may be utilized and that logical
structural, mechanical, electrical, and chemical changes may be
made without departing from the spirit or scope of the disclosure.
To avoid detail not necessary to enable those skilled in the art to
practice the disclosure, the description may omit certain
information known to those skilled in the art. The following
detailed description is, therefore, not to be taken in a limiting
sense, and the scope of the present disclosure is defined only by
the appended claims.
Exemplary embodiments of the present disclosure will now be
described with reference to the accompanying drawings. Embodiments
may, however, be embodied in different forms and should not be
constructed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
present disclosure to those skilled in the art. In the drawings,
the thicknesses of layers and regions are exaggerated for
clarity.
Embodiments provide a display apparatus which may include an
optical assembly which is capable of improving quality of a
displayed image. Embodiments also provide a display apparatus which
is capable of realizing a surface light source structure through
anisotropic light distribution.
FIG. 1 is an exploded perspective view illustrating a structure of
a display apparatus according to an embodiment, and FIG. 2 is a
cross-sectional view of the display apparatus.
Referring to FIGS. 1 and 2, a display apparatus 10 according to an
embodiment includes a display panel 16 displaying an image, a
backlight unit disposed at a rear side of the display panel 16 to
emit light toward the display panel 16, and an optical sheet 15
diffusing or processing the light emitted from the backlight
unit.
In detail, the optical sheet 15 includes a diffusion sheet and a
prism sheet. Also, the backlight unit may include an LED as a light
source. Here, the backlight unit includes a top view type LED
package in which light emitted from the light source is oriented
toward the display panel 16.
The backlight unit includes a board layer 12 placed on the bottom
of a panel case 11, light emitting parts 20 mounted on the board
layer 12, and a reflective layer 13 placed on a top surface of the
board layer 12.
In detail, the light emitting parts 20 may be arranged in a line at
a predetermined distance on a central portion of the reflective
layer 13. Also, a portion of the reflective layer 13 corresponding
to both side areas of the reflective layer 13 with respect to the
light emitting parts 20 may have an upwardly inclined surface.
Since the portion of the reflective layer 13 is inclined, light
emitted from the light emitting parts 20 and then refracted toward
the reflective layer 13 may be reflected toward the optical sheet
15 to improve light efficiency. Also, a reflective pattern or a
light extraction pattern 131 may be disposed on a top surface of
the reflective layer 13. The light emitted from the light emitting
parts 20 may collide with the pattern and thus be reflected toward
the display panel 16.
The board layer 12 may be a printed circuit board (PCB) formed of
one of polyethylene terephthalate, glass, polycarbonate, or
silicon. Alternatively, the board layer 12 may be provided in a
film type.
Each of the light emitting parts 20 may include a light emitting
device 21 including an LED and a lens 22 coupled to an upper
portion of the light emitting device 21. The light emitting device
21 may be the top view type LED package in which a light emitting
surface faces an upper side. Thus, light may be emitted upward at a
viewing angle of about 120 degrees. Also, most of light emitted
from the light emitting device 21 may be totally reflected in a
lateral direction by the lens 22. Thus, since the lens 22 is
disposed above the light emitting device 21, the backlight unit may
decrease in thickness and improve light efficiency and luminance
uniformity.
Also, a light guide layer 14 is disposed between the reflective
layer 13 and the optical sheet 15. The light guide layer 14 may be
filled with air or maintained in a vacuum state.
Hereinafter, a structure of the light emitting part according to
embodiments will be described in detail.
FIG. 3 is a perspective view illustrating an outer appearance of a
lens constituting a light emitting part according to an embodiment,
FIG. 4 is a perspective cross-sectional view of the lens according
to an embodiment, taken alone line I'-I of FIG. 3, FIG. 5 is a
bottom perspective view of the lens according to an embodiment,
taken along line I'-I of FIG. 3, FIG. 6 is a cross-sectional view
of the lens according to an embodiment, taken alone line I'-I of
FIG. 3, FIG. 7 is a perspective cross-sectional view of the lens
according to an embodiment, taken alone line II-II'' of FIG. 3,
FIG. 8 is a cross-sectional view of the lens according to an
embodiment, taken alone line II-II'' of FIG. 3, and FIG. 9 is a
perspective cross-sectional view of the lens according to an
embodiment, taken alone lines I'-I and II-II' of FIG. 3.
Referring to FIGS. 3 to 9, the light emitting part 20 according to
an embodiment includes the light emitting device 21 and the lens 22
disposed above the light emitting device 21. The lens 22 may be a
secondary lens disposed above a primary lens disposed on a top
surface of the light emitting device 21.
In detail, the lens 22 may have a concentric shape in
cross-section. Also, the lens 22 may have a cylindrical shape
having a predetermined height. In more detail, the lens 22 includes
a bottom surface portion 222 covering the light emitting device 21,
seated on the board layer 12, and having a concentric shape, a side
surface portion 223 extending upward from the bottom surface
portion 222 by a predetermined length and having a cylindrical
shape, and a top surface portion 221 having an aspheric curvature
having a parabolic shape on an upper end of the side portion 223
and gradually recessed toward a central direction of the lens 22.
The top surface portion 221 may be divided in a plurality of
sections in a circumferential direction. A boundary portion between
the adjacent sections may be stepped upward or downward. Light
emitted upward from the light emitting device 21 may collide with
the top surface portion 221 and thus be totally reflected in a
lateral direction. Also, one portion of the totally reflected light
may advance in the lateral direction, and the other portion of the
light may collide with the reflective layer 13 and thus be
re-reflected. Here, the more a distance between the light emitting
device 21 and the top surface portion 221 decreases, the more a
distance between the light emitting device 21 and a point at which
light collides with the reflective layer 13 decrease because a
total reflection angle decreases. Thus, when the stepped portion is
provided to cause a height difference of the top surface portion
221, the light emitted onto the top surface portion 221 and then
totally reflected may be re-reflected on several points of the
reflective layer 13. That is, the totally reflected light may
collide with any point of the reflective layer 13 corresponding to
a short-distance from the light emitting device 21 and any point of
the reflective layer 13 corresponding to a long-distance from the
light emitting device 21 and then be re-reflected. Thus, the light
re-reflected toward the optical sheet 15 may be uniformly
distributed onto the entire backlight unit to maintain uniform
brightness.
The top surface portion 221 may have an aspheric shape gradually
recessed from an outer edge portion in the central direction and
rounded upward in a convex shape.
Also, a top surface center portion 225 is defined on a central area
of the top surface portion 221. The top surface center portion 225
includes a recess portion 225a having a general oval shape with a
continuous curve or a track-shaped oval shape in which a
straight-line section and a curved-line section are connected to
each other when viewed from an upper side and recessed downward by
a predetermined depth and an uneven portion 225b defining the
bottom of the recess portion 225a and having a cross-section with a
spread book shape. The uneven portion 225b includes a pair of ridge
portions extending from an edge of the recess portion 225 to a
central portion and a valley portion disposed on a boundary portion
of the pair of ridge portions. Also, a curvature of the ridge
portion may be set in a shape in which the valley portion is lower
than an outer edge of the ridge portion. Thus, as shown in FIG. 11,
a depth H of a central portion of a top surface of the lens 22 may
be defined as a vertical length from an upper end of the lens 22 to
the valley portion. Also, a pitch P (or a radius) of the top
surface of the lens 22 may be defined as a horizontal distance from
the valley portion to an edge of the lens 22, i.e., a radius of the
lens 22.
Also, as shown in FIGS. 4 to 6, the top surface portion 221 of the
lens 22 that is cut by a vertical surface passing through a short
axis of the oval defining the recess portion 225a has a shape
continuously connected to the ridge portion of the uneven portion
225b. Also, the top surface portion 221 of the lens 22 and the
ridge portion constituting the uneven portion 225b may have rounded
with the same curvature, or the ridge portion may have a curvature
less than that of the top surface portion 221.
A bottom surface center portion 224 recessed upward by a
predetermined height is disposed on a bottom surface of the lens
22.
In detail, the bottom surface center portion 224 includes a bottom
portion 224a having a general oval shape with a continuous curve or
a track-shaped oval shape in which a straight-line section and a
curved-line section are connected to each other, a vertical
extension portion 224b vertically extending upward from the bottom
portion 224a, and a first roof portion 224c roundly extending
upward from an end of the vertical extension portion 224b. The
first roof portion 224c may extend in a shape of which a transverse
width is gradually narrowed toward an upper side. That is, the
first roof portion 224c has a prism shape or a lying triangular
pillar shape and a smoothly rounded edge. An inclined surface
constituting the first roof portion 224c may extend in a curved
shape in a direction in which an inner space of the bottom surface
center portion is gradually narrowed. For example, the inclined
surface may have a convex curvature.
Also, as shown in FIG. 9, a tip of the first roof portion 224c may
be spaced a predetermined distance d from the lowest point of the
top surface center portion 225, i.e., a valley portion of the
uneven portion 225b. When the first roof portion 224c communicates
with the valley portion, a hole connecting the top surface center
portion 225 of the lens 22 to the bottom surface center portion of
the lens 22 is defined. Light emitted through the hole may be
emitted onto the optical sheet 15 to cause a hot-spot having
luminance significantly greater than that of surrounding luminance.
Thus, the recess portions respectively defined in the top surface
center portion 225 and the bottom surface center portion of the
lens 22 may not communicate with each other.
Also, a second roof portion 224d may be further defined inside the
recess portion defined by the vertical extension portion 224b and
the first roof portion 224c.
In detail, the second roof portion 224d may extend from any point
corresponding between the bottom portion 224a of the bottom surface
center portion 224 and the upper end of the vertical extension
portion 224b to the tip of the first roof portion 224c. Also, the
second roof portion 224d may be roundly extends at a predetermine
curvature. Particularly, the second roof portion 224d may extend
upward in a rounded shape that is convex in a central direction of
a recess space defined by the first roof portion 224c and the
vertical extension portion 224b. Thus, the second roof portion 224d
may be the other roof portion additionally provided within the
first roof portion 224c.
Also, a transverse width (or length) of the second roof portion
224d may be less than a long axis of the oval defining the bottom
portion 224a.
A reference symbol X illustrated in FIG. 9 may be defined as a
center point of the lens 22. The center point of the lens 22 may
also be the center of the recess. That is, the recess on the top
and bottom of the lens 22 may be provided at the center of the
lens.
FIG. 10 is a view comparing light reflective index profiles
realized in a lens according to a related art and a lens according
to an embodiment.
Referring to FIG. 10, as shown in FIG. 10A, in a case of a lens
according to a related art, which has a concentric structure in
cross-section of the recess portion defined by the bottom surface
center portion, it may be confirmed that light horizontally emitted
from the light emitting device is not refracted while passing
through the lens, but advances straightly. Also, it may be
confirmed that light horizontally emitted from the light emitting
device is uniformly diffused in a circumferential direction of the
lens 22. That is, isotropic light distribution in which light
emitted from the light emitting device is uniformly diffused in the
circumferential direction may be realized.
On the other hand, as shown in FIG. 10B, in a case where a
cross-section of the recess portion defined by the bottom surface
center portion has a substantially oval shape, it may be confirmed
that anisotropic light distribution in which light emitted from the
light emitting device is refracted by a boundary surface between
the recess portion and the lens and then concentrated in a specific
direction. Here, the substantially oval shape may represent that
the oval shape includes the general oval shape connected in a
curved shape and the tracks shaped oval shape having a
straight-line section and a curved section.
In detail, in a case of a lens having the bottom surface center
portion with an oval shape, it may be confirmed that light is
refracted and concentrated in an extension direction of a short
axis of the oval. Particularly, it may be confirmed that
anisotropic light distribution in which light emitted from the
light emitting device 21 is refracted by a boundary surface between
the recess portion defined in the bottom surface center portion 224
and the lens 22, and then the light is concentrated into a
fan-shaped area that is spread by a predetermined angle .theta. in
left and right directions with respect to a short axis passing
through a center point of the lens 22 is realized. As described
above, since the lens has an anisotropic side surface shape, the
anisotropic light distribution in which light emitted from the
light emitting device 21 is concentrated in a specific direction
may be realized, and thus, the light may be diffused far away in a
single axis direction. Also, a ratio of a short-axis length to a
long-axis length of the oval may be adjusted to adjust an amount of
light refracted in the short axis direction and an angle .theta.
spread in the left and right directions with respect to the short
axis.
FIG. 11 is a cross-sectional view of a moving path of light
occurring on the top surface portion of a lens according to an
embodiment.
Referring to FIG. 11, light emitted from the light emitting device
21 is primarily refracted by the boundary surface between the lens
22 and the bottom surface center portion 224. In detail, light
emitted from the light emitting device 21 may be refracted in a
direction in which the light is concentrated in the short axis
direction of the recess portion having the oval shape while passing
through the bottom surface center portion 224 of the lens 22.
Also, light passing through the bottom surface center portion 224
to collide with the top surface portion 221 of the lens 22 and a
surface of the ridge portion constituting the uneven portion 225b
of the top surface center portion 225 may be totally reflected due
to a refractive index difference between the lens and air. Also,
one portion of the totally reflected light may be horizontally
diffused into the light guide layer 14, and the other portion of
the light may collide with the reflective layer 13 and then be
re-reflected upward.
Here, an angle at which the light colliding with the ridge portion
is totally reflected may be different from that at which the light
colliding with the top surface portion 221 is totally reflected.
Thus, points at which the light totally reflected by the top
surface portion 221 of the lens 22 and the uneven portion 225b of
the top surface center portion 225 is re-reflected may be uniformly
distributed over a short-distance area and a long-distance area
from the center of the lens 22. Thus, the brightness of the light
may be uniformly maintained.
A totally reflected angle .theta..sub.c of the light colliding with
the top surface portion 221 of the lens 22 may be defined by
Snell's law as follows:
sin .theta..sub.c=(n2/n1) (where, n1 is a refractive index of a
lens, and n2 is a refractive index of air)
When the lens 22 is formed of polycarbonate, since the
polycarbonate has a refractive index of about 1.58, a critical
angle .theta..sub.c for total reflection may be about 42 degrees.
Thus, the top surface portion 221 may have a curvature so that an
angle of incidence of the light incident into the top surface
portion 221 may be about 42 degrees or more. Thus, most of light
incident into the top surface portion 221 of the lens 22 may be
totally reflected and then diffused into the light guide layer.
Also, only a portion of the light may pass through the lens 22 to
move toward the display panel 15. Here, a light shield pattern
layer may be disposed on the top surface of the lens 22 to
re-reflect a portion of the light advancing toward the display
panel 15 onto the light guide layer.
A degree in which the light incident into the lens 22 is spread in
the short axis direction of the bottom surface center portion 224
may be decided by the depth H of the top surface center portion
225/a pitch P of the top surface portion 221 of the lens 22. The
pitch P of the top surface portion 221 of the lens 22 may represent
a distance from the top surface center portion 225 of the lens 22
to an edge of the top surface portion of the lens 22. Hereinafter,
the H/P value that represents the spread degree of the light
incident into the lens 22 may be defined as luminous intensity
distribution of the lens. A value of the luminous intensity
distribution may increase to allow light to be uniformly spread up
to a far distance.
According to the result of experiment, it may be confirmed that the
more the value of the luminous intensity distribution increases,
the more the hot-spot decreases to decrease light losses, whereas
the more the value of the luminous intensity distribution
decreases, the more the hot-spot increases to increase light
losses. Also, if the value of the luminous intensity distribution
is about 0.3 or less, the light losses may significantly increase.
Thus, the value of the luminous intensity distribution may be about
0.3 or more, particularly, about 0.5.
FIG. 12 is a view illustrating light distribution according to a
ratio of the long axis length to the short axis length in the
recess part defined in the central portion of the bottom surface of
the lens according to an embodiment.
Referring to FIG. 12, FIG. 12A illustrates light distribution in a
case where a ratio of the long axis/short axis (L/S) of the bottom
surface portion of the lens illustrated in FIG. 10A is about 1,
i.e., in a case of the recess portion having the concentric shape.
Also, FIG. 12B illustrates light distribution when a ratio of the
long axis/short axis is about 2, and FIG. 12C illustrates light
distribution when a ratio of the long axis/short axis is about
3.
According to the light distribution, it may be confirmed that the
more a ratio of the long axis/short axis, light is concentrated
into a single axis direction (the short axis direction) and moves
up to a far distance. That is to say, it may be confirmed that the
more a ratio of the long axis/short axis increases, a diffusion
angle .theta. of light spread in the circumferential direction
decreases, and the light is horizontally spread up to a far
distance. According to the above-described results, to achieve the
anisotropic light distribution that is intended to be realized
through the lens according to an embodiment, the lens may be
designed so that the ratio of the long axis/short axis of the oval
defining the recess portion of the bottom surface center portion is
at least 2 or more.
FIG. 13 is a view comparing light distribution occurring in a lens
in which the uneven part is disposed on the central portion thereof
according to an embodiment and a lens in which an uneven part is
not provided according to the related art.
Referring to FIG. 13, FIG. 13A illustrates light distribution in a
case where the uneven portion 225b is not provided on the top
surface portion, and FIG. 13B illustrates light distribution in a
case where the uneven portion 225b is provided on the top surface
portion.
In detail, in the case where the uneven portion 225b having a
specific shape is provided on the top surface of the lens 22, it
may be confirmed that an amount of totally reflected and
horizontally spread light increases when compared to the case in
which the uneven portion 225b is not provided. This represents that
the light colliding with the uneven portion 225b is totally
reflected to reduce an amount of light straightly advancing toward
the optical sheet 15, thereby minimizing generation of the
hot-spot. That is to say, a large amount of light emitted from the
light emitting device 21 may not be concentrated just above the
light emitting device 21, but be spread in the horizontal direction
to reduce intensity of the hot-spot.
Also, since the uneven portion 225b has the cross-section with the
spread book shape, extends in a long axis direction of the oval
constituting the bottom portion 224a of the bottom surface center
portion 224, and is disposed within the recess portion 225a having
the oval shape, a refraction direction of the light emitted from
the light emitting device 21 may be concentrated into a short axis
direction of the oval. Thus, when compared to the lens in which the
uneven portion 225b is not provided on the top surface portion
thereof, the lens 20 according to the current embodiment may have
an effect in which the light is spread up to far distance in the
short axis direction.
FIG. 14 is a simulation illustrating light distribution in a
backlight unit on which a plurality of light emitting parts
including the lens are mounted according to an embodiment.
Referring to FIG. 14, the simulation illustrates light distribution
in a backlight unit in which three light emitting parts 20 each
including the lens according to an embodiment are disposed at a
distance of about 60 mm in a length direction of the display panel
16, and an optical gap that represents a thickness of the light
guide layer is about 25 mm.
In detail, the length direction of the display panel 16 may
represent an arrangement direction of the light emitting parts 20
of FIG. 1. That is, in the display apparatus of FIG. 1, a long side
may be defined as a length direction, and a short side may be
defined as a width direction. Also, the light emitting parts 20 may
be arranged so that the long axis of the oval on the bottom surface
center portion of the lens is parallel to the length direction of
the display panel 16, and the short axis is parallel to the width
direction.
According to the above-described structure, the single light
emitting part 20 may have the light distribution illustrated in
FIG. 13B, i.e., the light distribution in which a pair of fan
shapes is disposed symmetrical to each other. Thus, a plurality of
light distribution having the above-described shape may overlap
each other on the edge portion to uniformly spread light over an
entire surface of the backlight unit. Thus, the brightness of the
backlight unit may be uniformly maintained, as well as, the number
of mounted light emitting device may be reduced when compared to
that of a backlight unit according to the related art to reduce the
manufacturing costs. Also, when compared to the backlight unit
according to the related art, since the optical gap may be reduced,
the backlight unit may be reduced in thickness. Therefore, the
display apparatus may be slimmer.
According to the embodiments, the backlight unit may be reduced in
thickness, and thus, the display apparatus including the backlight
unit may be improved in outer appearance.
Also, the lens structure in which the light emitted from the light
emitting device is totally reflected in the downward direction of
the side surface may be adopted to the light source provided in the
backlight unit to improve the light efficiency and the luminance
uniformity. Therefore, the quality of an image displayed on the
display apparatus may be improved.
Also, the lens having the anisotropic light distribution structure
may be adopted to the top view-type LED package to maximally
horizontally total-reflect the light emitted from the light source
in the short axis direction, thereby spreading the light up to a
far distance. Thus, even though the number of light sources is
reduced, the light efficiency and the luminance uniformity may be
uniformly maintained.
Also, since a portion of the reflective layer provided on the
bottom of the backlight unit is inclinedly designed, the light
emitted from the light source may be maximally reflected toward the
display panel to improve the light efficiency.
Also, since it is unnecessary to provide a separate member
corresponding to the light guide layer, the backlight unit may be
reduced in weight, and thus, the display apparatus may be
lightweight.
As broadly described and embodied herein, a display apparatus may
include a display panel, and a backlight provided adjacent the
display panel. The backlight may include an optical sheet provided
adjacent the display panel, a reflector provided a prescribed
distance from the optical sheet, at least one light emitting device
provided adjacent the reflector, and a lens provided over a
corresponding the light emitting device. Here, the lens may include
a lower recess formed on a bottom surface of the lens and provided
a prescribed distance over the light emitting device, and an upper
recess formed on a top surface of the lens and provided to
vertically overlap the bottom recess.
The lower recess may have an oval shape and may include a side
surface that extends vertically from the bottom surface, and a
first upper surface that extends from the side surface at a first
prescribed angle relative to the side surface, the first upper
surface having a convex curvature. The first upper surface extends
from the side surface to form a vertex a prescribed distance above
the bottom surface. The lower recess may include a second upper
surface that extends from the side surface at a second prescribed
angle relative to the side surface, and a third upper surface
symmetrical to the second upper surface and extending to the second
upper surface from an opposite side of the lower recess. Moreover,
the second upper surface and the third upper surface may have a
concave curvature.
The second upper surface and the third upper surface intersect at a
prescribed angle relative to each other parallel to a long axis of
the lower recess. The vertex of the first upper surface may be
adjacent to the first and second upper surfaces where the first and
second surfaces intersect. The first upper surface may extend from
the side surface at a first prescribed distance from the bottom
surface and the second upper surface may extend from the side
surface at a second prescribed distance from the bottom surface.
The second prescribed distance may be less than or equal to the
first prescribed distance. Moreover, the oval shape of the lower
recess may include a rectangular portion and round portions
provided at short ends of the rectangular portion, and the first
upper surface may extend from the side surface at the round portion
and the second and third surfaces may extend from the side surface
at the rectangular portion.
A length of the lower recess may be at least twice a width of the
lower recess. The top surface of the lens may have a prescribed
shape that is convex from an outer circumferential edge to a center
of the lens. The top surface may include a plurality of sections
corresponding to circular sectors of the lens. Here, adjacent
sections of the top surface may have different heights relative to
each other. Moreover, the curvature of the top surface may be such
that an angle of incidence of light incident on the top surface of
the lens from a corresponding light emitting device is greater than
or equal to 42.degree..
The upper recess may have an oval shape and may include a side
surface that extends vertically from the top surface of the lens, a
first lower surface having a prescribed curvature and extending
from the side surface, and a second lower surface which is
symmetrical to the first lower surface and extending toward the
first lower surface from an opposite side of the upper recess.
The first lower surface and the second lower surface may have
concave curvatures. The first and second lower surfaces may
intersect at a prescribed angle relative to each other parallel to
a long axis of the upper recess. A depth of the upper recess may be
greatest where the first and second lower surfaces intersect. A
long axis of the lower recess may be parallel to a long axis of the
upper recess and provided to vertically overlap each other.
Moreover, a ratio of a depth of the upper recess to a radius of the
lens may satisfy the condition: 0.3.ltoreq.H/P.ltoreq.0.5, wherein
H is a height from a top of the lens to a lowermost point in the
upper recess, and P is the radius of the lens.
In one embodiment, a display apparatus may include a display panel,
a light emitting device, a reflector provided adjacent to the light
emitting device, and a lens provided a prescribed distance over the
light emitting device and configured to distribute light to
illuminate the display panel. The lens may include a recess having
an oval shape provided on a bottom surface of the lens. The recess
may include a side surface that extends vertically a prescribed
distance from the bottom surface, and an upper surface that extends
from the side surface and having a convex curvature, wherein a
width of the upper surface gradually decreases into the recess.
In one embodiment, a display apparatus may include a board, a light
emitting part comprising a light emitting device mounted on the
board and a lens disposed above the light emitting device, a
reflective layer disposed on a top surface of the board, an optical
sheet disposed above the reflective layer at a height spaced apart
from the light emitting part, and a display panel disposed on a top
surface of the optical sheet. Here, the lens may include a bottom
portion having a cross-section with an oval shape, a vertical
extension portion recessed and extending by a predetermined length
upward from the bottom portion, and a bottom surface center portion
comprising a first roof portion inclinedly received in a shape that
is gradually narrowed upward from an end of the vertical extension
portion.
The display apparatus may include an edge of the first roof portion
is smoothly rounded. An inclined surface may include the first roof
portion extends in a curved shape in a direction in which an inner
space of the bottom surface center portion is gradually narrowed.
The display apparatus may further include a second roof portion
protruding to an inner space defined by the vertical extension
portion and the first roof portion, the second roof portion
connecting a tip of the first roof portion at any point of the
vertical extension portion. The display apparatus may include an
inclined surface constituting the second roof portion is curved in
a direction in which the second roof portion protrudes to the inner
space. The tip of the first roof portion may have a length (or a
width) less than a long axis length of the bottom portion.
Moreover, a ratio of a long axis/short axis of the bottom portion
may be about 2 or more.
The lens may include a top surface portion having an aspherical
surface with a parabola shape that is gradually higher outward from
a center thereof and having an outer line with a concentric shape.
The top surface portion may be partitioned into a plurality of
sections in a circumferential direction, and the adjacent sections
may have stepped with respect to each other so that the adjacent
sections a height difference therebetween.
The lens may include a recess portion recessed by a predetermined
depth with a cross-section having an oval shape in a central area
of the top surface portion and a top surface center portion
comprising an uneven portion disposed on a bottom of the recess
portion. The uneven portion may include a pair of ridge portions
curved upward and a valley portion disposed between the pair of
ridge portions. The valley portion may extend in a long axis
direction of the oval constituting the recess portion. The uneven
portion may have a cross-section with a spread book shape, and the
valley passing through a center of the uneven portion may extend in
a long axis direction of the oval constituting the recess
portion.
The center of the uneven portion may be recessed by a predetermined
depth from a tip of the first roof part. A long axis of the oval
constituting the bottom portion and the long axis of the oval
constituting the recess portion of the top surface center portion
may extend in parallel to each other.
A ratio of a depth of the top surface center portion of the lens to
a radius of the lens may satisfy a following condition
0.3.ltoreq.H/P.ltoreq.0.5 (where, H is the depth of the top surface
center portion of the lens, and P is the radius of the lens). The
top surface portion of the lens may be rounded in a convex shape
with a curvature so that incident light has an incident angle of
about 42 degrees or more.
At least one portion of the reflective layer may be inclined in a
direction in which the reflective layer is higher toward an edge
thereof. A space between the reflective layer and the optical sheet
may be an air layer or a vacuum layer.
Any reference in this specification to "one embodiment," "an
embodiment," "example embodiment," etc., means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
invention. The appearances of such phrases in various places in the
specification are not necessarily all referring to the same
embodiment. Further, when a particular feature, structure, or
characteristic is described in connection with any embodiment, it
is submitted that it is within the purview of one skilled in the
art to effect such feature, structure, or characteristic in
connection with other ones of the embodiments.
Although embodiments have been described with reference to a number
of illustrative embodiments thereof, it should be understood that
numerous other modifications and embodiments can be devised by
those skilled in the art that will fall within the spirit and scope
of the principles of this disclosure. More particularly, various
variations and modifications are possible in the component parts
and/or arrangements of the subject combination arrangement within
the scope of the disclosure, the drawings and the appended claims.
In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to
those skilled in the art.
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