(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2006/0227545 A1
`Mok et al.
`(43) Pub. Date:
`Oct. 12, 2006
`
`US 20060227545A1
`
`(54) LIGHT EMITTING PANEL
`
`Publication Classification
`
`(76) Inventors: Thye Linn Mok, Loveland, CO (US);
`Siew Kim Tan, Loveland, CO (US);
`Shin Wen Ng, Loveland, CO (US)
`
`Correspondence Address:
`AVAGO TECHNOLOGIES, LTD.
`P.O. BOX 1920
`DENVER, CO 80201-1920 (US)
`
`(21) Appl. No.:
`(22) Filed:
`
`11/103,172
`Apr. 11, 2005
`
`(51) Int. Cl.
`(2006.01)
`B60O I/26
`(52) U.S. Cl. .............................................................. 362/227
`
`ABSTRACT
`(57)
`In one embodiment, a light emitting panel includes a base
`panel and a plurality of light emitting elements mounted to
`the base panel. Each of the light emitting elements produces
`an illumination pattern having a region of Substantially
`uniform intensity that extends over a radiation angle of at
`least about 60°. One or more light conditioners are posi
`tioned adjacent the base panel to receive and condition light
`produced by the light emitting elements.
`
`1
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`16
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`
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`18
`
`12
`
`Petitioner Hisense USA Corporation
`Exhibit 1025 - Page 1 of 7
`
`

`

`Patent Application Publication Oct. 12, 2006 Sheet 1 of 2
`
`US 2006/0227545 A1
`
`20
`
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`FIG. 1
`
`12
`
`
`
`Petitioner Hisense USA Corporation
`Exhibit 1025 - Page 2 of 7
`
`

`

`Patent Application Publication Oct. 12, 2006 Sheet 2 of 2
`
`US 2006/0227545 A1
`
`
`
`4. 6 N
`
`-90 - 70 -50 -30 - 10 1 0 30 50 70 90
`Degree
`FIG. 4
`
`
`
`162
`
`Petitioner Hisense USA Corporation
`Exhibit 1025 - Page 3 of 7
`
`

`

`US 2006/0227545 A1
`
`Oct. 12, 2006
`
`LIGHT EMITTING PANEL
`
`BACKGROUND
`Light emitting panels are commonly used as back
`0001
`lights for display systems (e.g. liquid crystal displays),
`although they may be used for other purposes as well. Light
`emitting panels commonly used for backlighting displays
`include cold cathode florescent lamps (CCFL) and electro
`luminescent panels. These types of light emitting panels are
`advantageous in that they provide Substantially uniform
`illumination over the entire area of the panel, thus providing
`even illumination for the display. Unfortunately, however,
`CCFL and electro-luminescent panels are not without their
`disadvantages, including poor color rendition. In addition,
`they may involve the use of hazardous materials. Such as
`mercury.
`0002 Partly in an effort to address the shortcomings of
`CCFL and electro-luminescent panels, light emitting panels
`have been developed that utilize light emitting diodes
`(LEDs) as the light sources. Besides being mercury-free,
`LED light emitting panels typically provide better color
`rendition than CCFL and electro-luminescent panels.
`0003. One type of LED light emitting panel is the edge-lit
`panel. In an edge-lit panel, a plurality of LEDs are posi
`tioned adjacent one or more of the edges of a light guide
`panel. Light from the LEDs enters the edges of the light
`guide panel and is re-directed within the light guide panel so
`that the light emerges from the front face of the light guide
`panel. A reflector may be provided on the back surface of the
`panel to reflect light toward the front surface of the panel
`that would otherwise exit from the back surface of the panel.
`0004 Unfortunately, edge-lit light emitting panels are not
`without their drawbacks. For example, the placement of the
`LEDs along the edges of an edge-lit panel limits the ability
`to dissipate heat produced by the LEDs. The edge-lit con
`figuration also limits the maximum size of the panel, in that
`the number of LEDs that may be used to illuminate the panel
`increases linearly with the edge length, but the area that must
`be illuminated increases as the square of the edge length.
`Consequently, edge-lit panels are typically limited to panels
`having Small areas.
`0005 Another type of LED light emitting panel is a
`so-called back-lit panel in which a plurality of LEDs are
`arranged in a two-dimensional array adjacent the back
`surface of the panel. The panel diffuses (i.e., evens-out) the
`light from the LEDs so that the panel appears to provide
`more even illumination than would be possible with just the
`LEDs alone. While back-lit panels do not suffer from the
`brightness limitations of edge-lit designs, and they may be
`used with panels having larger areas, it has proven difficult
`to effectively diffuse the light from the individual LEDs so
`that the panel appears to be evenly illuminated.
`0006 For example, one way to improve the illumination
`uniformity of a back-lit LED panel is to place the LEDs
`closer together. Disadvantageously, however, this increases
`the cost of the panel as more LEDs must be used. The closer
`spacing of the LEDs can also create heat dissipation prob
`lems. Another way to improve the illumination uniformity is
`to cause the panel to provide increased light diffusion.
`However, increased light diffusion typically represents a
`decrease in efficiency, thereby reducing the brightness of the
`
`panel or requiring the use of more or brighter LEDs to
`compensate for the efficiency loss associated with the
`increased diffusion.
`
`SUMMARY OF THE INVENTION
`0007. In one embodiment, a light emitting panel com
`prises a base panel having a plurality of light emitting
`elements mounted thereon. Each of the light emitting ele
`ments produces an illumination pattern having a region of
`Substantially uniform intensity that extends over a radiation
`angle of at least about 60°. One or more light conditioners
`are positioned adjacent the base panel to receive and con
`dition light produced by the light emitting elements.
`0008. Other embodiments are also disclosed.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0009 Illustrative and presently preferred exemplary
`embodiments of the invention are shown in the drawings in
`which:
`0010 FIG. 1 is a side view in elevation of one embodi
`ment of a light emitting panel;
`0011 FIG. 2 is a plan view of a base panel having a
`plurality of light emitting elements mounted thereon;
`0012 FIG. 3 a sectional view in elevation of one
`embodiment of a light emitting diode producing an illumi
`nation pattern comprising a region of Substantially uniform
`intensity;
`0013 FIG. 4 is a graphical representation of the illumi
`nation pattern produced by the light emitting diode of FIG.
`3; and
`0014 FIG. 5 is a sectional view in elevation of another
`embodiment of a light emitting diode producing an illumi
`nation pattern comprising a region of Substantially uniform
`intensity.
`
`DETAILED DESCRIPTION
`0015. An exemplary light emitting panel 10 is shown in
`FIGS. 1 and 2 and may comprise a base panel 12 having a
`plurality of light emitting elements 14 thereon. As will be
`described in greater detail below, each of the light emitting
`elements 14 produces an illumination pattern 46 that com
`prises a region 28 of Substantially uniform intensity that
`extends over a large radiation angle (e.g., at least about 60°.
`and typically at least about 100). See FIG. 4. One or more
`light conditioners 16, 18 are positioned adjacent the base
`panel to receive and condition light produced by the various
`light emitting elements 14. The light conditioners may
`comprise a diffuser 16 that is positioned adjacent the base
`panel 12 so that the diffuser 16 receives and diffuses light
`produced by the various light emitting elements 14 provided
`on the base panel 12, and a brightness enhancer 18 that is
`positioned adjacent the diffuser 16. The brightness enhancer
`18 collects diffused light from the diffuser 16 and directs it
`out of a front surface 52 of the brightness enhancer 18 to
`maximize the on-axis brightness of the light emitting panel
`10. In one application, the light emitting panel 10 may be
`positioned adjacent a display device 20, such as a liquid
`crystal display panel 22, to form a backlit display system 24.
`
`Petitioner Hisense USA Corporation
`Exhibit 1025 - Page 4 of 7
`
`

`

`US 2006/0227545 A1
`
`Oct. 12, 2006
`
`0016 Referring now to FIGS. 3 and 4, each light emit
`ting element 14 may comprise a light emitting diode 26 that
`produces an illumination pattern 46 that includes a region 28
`of substantially uniform intensity. The region 28 of substan
`tially uniform intensity extends over a radiation angle of at
`least about 60° and typically over a radiation angle of at least
`about 100°. See FIG. 4. In the embodiment shown and
`described herein, the light emitting diode 26 may comprise
`a body or substrate 300 in which is formed a reflector cup 32.
`A light emitting diode junction 34 (i.e., a die) is positioned
`within the reflector cup 32. A lens 36 is then formed over the
`diode junction 34 and reflector cup 32 in the manner best
`seen in FIG. 3. The reflector cup, 32 and lens 36 collect and
`direct light emitted by the diode junction 34 so that the light
`emitting diode 26 produces an illumination pattern 46 that
`comprises the region 28 of substantially uniform intensity, as
`illustrated in FIG. 4. The region 28 of substantially uniform
`intensity may also be referred to herein as a “flat topped
`radiation pattern,” to distinguish it from a Lambertian radia
`tion pattern, in which the intensity is proportional to the
`cosine of the emission angle relative to the normal. Lam
`bertian radiation patterns are typically associated with con
`ventional LEDs that emit light over high radiation angles
`(i.e., greater than about 100).
`0017. In operation, the light emitting panel 10 produces
`a Substantially uniform light output over its entire area,
`making it highly Suitable for backlighting applications. The
`Substantially uniform light output of the light emitting panel
`10 is achieved without the need for closely-spaced light
`emitting diodes and without the need to utilize high-diffu
`sivity diffusers. In addition, the light emitting panel 10 is not
`size-limited and is capable of providing high illuminations
`over large areas, making it ideal for use with large area
`displays, such as large screen computer and television
`displays.
`0018. Having briefly described one embodiment of a light
`emitting panel 10, various exemplary embodiments of the
`light emitting panel will now be described in detail. How
`ever, before proceeding with the description it should be
`noted that the light emitting panels disclosed herein may be
`utilized in any of a wide range of applications (e.g., as
`backlights for display devices) and to produce light having
`any of a wide range of spectral outputs (e.g., white light or
`colored light), as would become readily apparent to persons
`having ordinary skill in the art after having become familiar
`with the teachings provided herein.
`0.019
`Referring back now to FIG. 1, one embodiment of
`a light emitting panel 10 may comprise a base panel 12
`Suitable for receiving the various light emitting elements 14
`in the manner described herein. The base panel 12 may
`comprise a generally rectangular shaped, plate-like member
`having a length 38 and a width 40 that are commensurate
`with the intended size of the panel 10. The base panel 12
`provides a convenient mounting location for the various
`light emitting elements 14, allowing them to be arranged in
`a two dimensional array or pattern over both the length 38
`and width 40 of the base panel 12. Because each of the light
`emitting elements needs to be electrically connected to a
`source of electrical power, it will be convenient in most
`applications for the base panel 12 to comprise a printed
`circuit board, although this is not required. In an embodi
`ment wherein the base panel 12 comprises a printed circuit
`board, the light emitting elements 14 may be electrically
`
`connected (e.g., by soldering) to pads (not shown) provided
`on the base panel 12. The pads of the base panel 12 may then
`be connected to drive circuitry (not shown) suitable for
`providing the required electric current to the light emitting
`elements 14.
`0020. The various light emitting elements 14 may be
`mounted to the base panel 12 in any of a wide variety of
`configurations. In the embodiment shown and described
`herein, the light emitting elements 14 are arranged so that
`they define a plurality of rows 42 and columns 44. Alterna
`tively, other configurations are possible.
`0021. A reflective surface 50 may be provided on the base
`panel 12 to “recycle” (i.e., reflect) light which may be
`reflected by the back surface 60 of diffuser 16 (i.e., light
`incident on the back surface 60 of the diffuser 16 at an angle
`that exceeds the critical angle for the particular diffuser 16).
`The reflective surface 50 may comprise a specular reflective
`Surface (e.g., aluminum), or a diffuse reflective Surface (e.g.,
`white paint). The reflective surface 50 may comprise a
`separate component (e.g., a sheet-like material) that is
`affixed to the base panel 12. Alternatively, the reflective
`surface 50 may be deposited directly on the base panel 12 by
`any of a wide range of processes Suitable for depositing the
`particular type of reflective material that is to be used.
`0022. The diffuser 16 is positioned in spaced-apart rela
`tion to the base panel 12 so that it receives and diffuses light
`produced by the light emitting elements 14 as well as light
`that my be reflected by the reflective surface 50 provided on
`base panel 12. In the embodiment shown and described
`herein, the diffuser 16 comprises a plastic diffuser film
`formed from a polycarbonate (e.g., Lexan R)) plastic mate
`rial, such as a plastic diffuser film available from GE
`Advanced Materials and sold under the trade mark "Illu
`minex”. Alternately, other types of diffuser films made from
`other types of materials (e.g., polyethylene terephthalate
`(PET)) could also be used.
`0023 The diffuser 16 may be mounted in front of the base
`panel 12 and separated therefrom by a spaced-distance 48.
`Generally speaking, larger spaced-distances 48 will improve
`the uniformity of the light produced by the panel, but at the
`expense of panel thickness and some loss of efficiency. By
`way of example, in one embodiment, the diffuser 16 is
`separated from the base panel 12 by a distance 48 of about
`50 millimeters (mm) or less.
`0024. The brightness enhancer 18 is positioned adjacent
`the diffuser 16 and receives diffused light therefrom. The
`brightness enhancer 18 comprises a plurality of optical
`elements, such as prisms 55 defined by the front surface 52
`of the brightness enhancer 18, that collect light from the
`diffuser 16 and direct it out the front surface 52 of the
`brightness enhancer 18. The brightness enhancer 18 thereby
`maximizes the on-axis brightness of the panel 10. By way of
`example, in the embodiment shown and described herein,
`the brightness enhancer 18 comprises a brightness enhance
`film (BEF) available from 3M and sold under the registered
`trademark Vikuitir). Alternatively, other types of brightness
`enhancers could be used.
`0025 The brightness enhancer 18 may be mounted in
`front of the diffuser 16 and may be separated therefrom by
`a spaced-distance 54. However, the brightness enhancer 18
`is preferably stacked directly on (or applied to) the diffuser
`16, thereby minimizing or eliminating the distance 54.
`
`Petitioner Hisense USA Corporation
`Exhibit 1025 - Page 5 of 7
`
`

`

`US 2006/0227545 A1
`
`Oct. 12, 2006
`
`0026 Referring now to FIGS. 3 and 4, each light emit
`ting element 14 may comprise a light emitting diode 26 that
`produces an illumination pattern 46 having a region 28 of
`Substantially uniform intensity that extends over a large
`radiation angle of at least about 60° and more preferably
`over an angle of at least about 100°. See FIG. 4. In one
`embodiment, the light emitting diode 26 may comprise a
`base portion or substrate 30 in which is formed a reflector
`cup 32. The light emitting diode junction 34 or die is then
`positioned within the reflector cup 32.
`0027. The base portion or substrate 30 may be fabricated
`from various materials (e.g., plastics). The base portion 30
`may also be provided with a suitable lead-frame or other
`electrically conductive structure for electrically connecting
`the light emitting diode junction 34 to pads or terminals 56
`provided on the base portion 30.
`0028. The reflector cup 32 may be formed in the base
`portion 30 during fabrication thereof. Alternatively, the
`reflector cup 32 may be mechanically formed after fabrica
`tion of the base portion 30, such as, for example, by drilling.
`It is generally preferred that the reflector cup 32 be provided
`with a reflective coating 58 thereon to improve efficiency.
`By way of example, in one embodiment, the reflector cup 32
`is initially plated with copper, then with a Subsequent layer
`of gold or silver to maximize reflectivity.
`0029. A lens 36 is then formed over the diode junction 34
`and reflector cup 32 in the manner best seen in FIG. 3. The
`lens 36 may comprise any of a wide range of transparent
`plastic materials and may be formed in accordance with any
`of a wide range of processes known in the art for providing
`lenses to LED packages. However, what is not conventional
`about the lens 36 is its shape. More specifically, the lens 36
`and reflector cup 32 work together to re-direct light pro
`duced by the light emitting junction 34 so that the LED
`produces an illumination pattern 46 comprising the region
`28 of substantially uniform intensity, as best seen in FIG. 4.
`0030. With reference now primarily to FIG. 4, the illu
`mination pattern 46 may be characterized as a flat topped
`radiation pattern in that the region 28 of substantially
`uniform intensity extends over a wide radiation angle of at
`least about 60° and typically at least about 100°, before the
`illumination intensity drops below about 50% of the maxi
`mum illumination intensity produced by the light emitting
`element 14. Stated another way, the region 28 of substan
`tially uniform intensity includes a minimum intensity value
`and a maximum intensity value, the minimum intensity
`value not being less than about 50% of the maximum
`intensity value. The flat-topped radiation pattern is achieved
`by the combination of the reflector cup 32 and the lens 36.
`0031. A suitable design configuration for the reflector cup
`32 and lens 36 may be developed by using any of a number
`of ray-tracing computer programs (e.g., ASAP Pro, available
`from Breault Research Organization, Inc., of Tucson, Ariz.
`85715 (USA)) to model a proposed design. By way of
`example, in one embodiment, a generally conically-shaped
`reflector cup 32 and a lens 36 having a generally flat light
`output surface 62 (FIG. 3) will produce an illumination
`pattern 46 in which the region 28 of substantially uniform
`intensity extends over a radiation angle of at least about
`100°. In another embodiment, illustrated in FIG. 5, the lens
`136 may comprise a light output Surface 162 having a
`convex portion 164 and a concave portion 166. Generally
`
`speaking, it will be preferred, but not required, to base the
`shape of the light output surface (e.g., 62 or 162) of the lens
`(e.g., 36 or 136) on a 3" order polynomial curve for ease of
`fabrication, although this is not required.
`0032. It is noted that regardless of the particular arrange
`ment of the light emitting elements 14 on the base panel 12,
`the light emitting elements 14 should be spaced so as to
`maximize the uniformity of the light output of the panel 10.
`For example, the uniformity of the light output of the panel
`10 can be maximized by considering the illumination pattern
`46 (FIG. 4) produced by the light emitting elements 14,
`specifically the angle over which the illumination pattern 46
`comprises the region 28 of substantially uniform intensity, as
`well as the distance 48 separating the base panel 12 and
`diffuser 16. That is, each of the light emitting elements 14
`should be positioned sufficiently close to one another so that
`the regions 28 of Substantially uniform intensity converge or
`merge together at about the same distance from the light
`emitting elements 14 as the distance 48 separating the base
`panel 12 and the diffuser 16. So spacing the various light
`emitting elements 14 will reduce the appearance of dark and
`light spots in the light emitting panel 10. Accordingly, in one
`embodiment wherein the region 28 of substantially uniform
`intensity extends over a radiation angle of about 100°, and
`wherein the distance 48 between the base panel 12 and the
`diffuser 16 is about 50 mm or less, a uniform illumination
`may be achieved by arranging the individual light emitting
`elements 14 So that they are spaced apart form one another
`by a distance of about 10-20 mm.
`0033. The light emitting elements 14 may be selected to
`provide any of a wide range of spectral outputs that may be
`desired for the particular light emitting panel 10. For
`example, several types of light emitting diodes have been
`developed that produce substantially white light. Therefore,
`a light emitting panel 10 that emits substantially white light
`may be produced in accordance with the teachings provided
`herein by utilizing white light emitting LEDs for the light
`emitting elements 14 (e.g., LEDs comprised of blue light
`emitters covered by phosphor coatings that convert their
`blue light to white light). Alternatively, white light-emitting
`panels may be produced by utilizing separate red, green, and
`blue LEDs for the light emitting elements 14, or by utilizing
`LEDs of other colors. Adjustments in the spectral output of
`the light emitting panel 10 may be accomplished by varying
`the numbers and placements of certain of the colors of the
`light emitting elements, as well as by variably driving the
`various colors of light emitting elements to increase or
`decrease their relative brightness.
`1. A light emitting panel, comprising:
`a base panel;
`a plurality of light emitting elements mounted to said base
`panel, each of said plurality of light emitting elements
`producing an illumination pattern having a region of
`substantially uniform intensity that extends over a
`radiation angle of at least about 60°; and
`one or more light conditioners to receive and condition
`light produced by said plurality of light emitting ele
`mentS.
`2. The light emitting panel of claim 1, wherein each of
`said plurality of light emitting elements comprises a light
`emitting diode.
`
`Petitioner Hisense USA Corporation
`Exhibit 1025 - Page 6 of 7
`
`

`

`US 2006/0227545 A1
`
`Oct. 12, 2006
`
`3. The light emitting panel of claim 2, wherein each
`region of Substantially uniform light intensity extends over
`a radiation angle of at least about 100°.
`4. The light emitting panel of claim 3, wherein each light
`emitting diode comprises:
`a reflector cup;
`a light emitting junction mounted within said reflector
`Cup; and
`a lens positioned over said reflector cup and said light
`emitting junction.
`5. The light emitting panel of claim 4, wherein said lens
`comprises a Substantially flat light output surface.
`6. The light emitting panel of claim 4, wherein said lens
`comprises a light output Surface comprising a convex por
`tion and a concave portion.
`7. The light emitting panel of claim 2, wherein the light
`emitting diodes emit two or more different wavelengths of
`light.
`8. The light emitting panel of claim 1, wherein said base
`panel comprises a printed circuit board, said printed circuit
`board electrically connecting each of said light emitting
`elements to a Supply of electric current.
`9. The light emitting panel of claim 1, wherein each
`region of Substantially uniform intensity comprises a mini
`mum intensity and a maximum intensity, the minimum
`intensity not being less than about 50% of the maximum
`intensity.
`10. The light emitting panel of claim 1, further comprising
`a reflective surface provided on said base panel.
`11. The light emitting panel of claim 10, wherein said
`reflective Surface comprises a specular reflective surface.
`12. The light emitting panel of claim 10, wherein said
`reflective surface comprises a diffuse reflective surface.
`13. The light emitting panel of claim 1, wherein the light
`conditioners comprise:
`a diffuser positioned adjacent said base panel, said dif
`fuser receiving and diffusing light produced by said
`plurality of light emitting elements; and
`a brightness enhancer positioned adjacent said diffuser to
`collect diffused light from said diffuser and direct light
`out of a front surface of the brightness enhancer.
`14. The light emitting panel of claim 13, wherein said
`diffuser comprises a polycarbonate plastic.
`
`15. The light emitting panel of claim 13, wherein said
`brightness enhancer comprises a sheet-like material defining
`a plurality of prisms.
`16. A display system, comprising:
`a base panel;
`a plurality of light emitting elements mounted to said base
`panel, each of said plurality of light emitting elements
`producing an illumination patter comprising a region of
`substantially uniform intensity that extends over a
`radiation angle of at least about 100°:
`one or more light conditioners to receive and condition
`light produced by said plurality of light emitting ele
`ments; and
`a display device positioned adjacent said light condition
`CS.
`17. The display system of claim 16, wherein the light
`conditioners comprise:
`a diffuser positioned adjacent said base panel, said dif
`fuser receiving and diffusing light produced by said
`plurality of light emitting elements; and
`a brightness enhancer positioned adjacent said diffuser,
`said brightness enhancer receiving diffused light from
`said diffuser.
`18. The display system of claim 17, wherein said display
`device comprises a liquid crystal display panel.
`19. A light emitting panel, comprising:
`a base panel having a reflective surface provided thereon;
`a plurality of light emitting elements mounted to said base
`panel, each of said plurality of light emitting elements
`producing an illumination patter that comprises a
`region of Substantially uniform intensity that extends
`over a radiation angle of at least about 100:
`diffuser means positioned adjacent said base panel for
`diffusing light produced by said plurality of light emit
`ting elements; and
`brightness enhancing means positioned adjacent said dif
`fuser means for enhancing the brightness of diffused
`light from said diffuser means.
`20. The light emitting panel of claim 19, wherein each of
`said plurality of light emitting elements comprises a light
`emitting diode.
`
`Petitioner Hisense USA Corporation
`Exhibit 1025 - Page 7 of 7
`
`