(12) United States Patent
`Suehiro et al.
`
`(54) LIGHT EMITTING DEVICE
`
`(75)
`
`Inventors: Yoshinobu Suehiro, Aichi-ken (JP);
`Yuji Takahashi, Aichi-ken (JP);
`Hideaki Kato, Aichi-ken (JP); Koichi
`Kaga, Aichi-ken (JP); Kiyotaka
`Teshima, Tokyo (JP); Shunsuke
`Ohtsuka, Tokyo (JP)
`
`(73) Assignees: Toyoda Gosei Co., Ltd., Aichi-ken
`(JP); Koha Co., Ltd., Tokyo (JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 207 days.
`
`(21) Appl. No.: 09/871,699
`Jun. 4, 2001
`(22) Filed:
`Prior Publication Data
`(65)
`US 2002/0001192 Al Jan. 3, 2002
`Foreign Application Priority Data
`(30)
`Jun. 2, 2000
`(JP)
`2000-165864
`F21L 4/00
`(51) Int. CI.7
`362/187; 362/800; 362/119;
`(52) U.S. CI
`362/120; 362/202; 362/203
`(58) Field of Search
`362/800, 119,
`362/202, 203, 187, 545, 247, 231; 313/500,
`505, 510, 498, 512; 257/100, 86, 91, 93,
`98, 99
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`5,177,593 A * 1/1993 Abe
`
`II
`
`US006834977B2
`US 6,834,977 B2
`Dec. 28,2004
`
`(io) Patent No.:
`(45) Date of Patent:
`
`5,475,241 A * 12/1995 Harrah et al. .
`6,093,940 A * 7/2000 Ishinaga et al.
`6,345,903 B1 * 2/2002 Koike et al. ..
`6,383,835 B1 * 5/2002 Hata et al
`
`. 257/99
`. 257/99
`362/249
`. 438/65
`
`* cited by examiner
`
`Primary Examiner—Stephen Husar
`Assistant Examiner—Anabel Ton
`(74) Attorney, Agent, or Firm—McGinn & Gibb, PLLC
`
`(57)
`
`ABSTRACT
`
`Separate leads and a common lead are provided on the upper
`and lower surfaces of a substrate. A plurality of LED
`elements are disposed in an array on the common lead on the
`upper surface of the substrate. The common lead provided
`on the upper surface of the substrate is connected to the
`common lead provided on the lower surface of the substrate
`through through-hole plating. Heat generated from the plu­
`rality of LED elements is transferred through the common
`lead provided on the upper surface of the substrate and the
`through-hole plating to the common lead provided on the
`lower surface of the substrate and is release therefrom into
`the air. By virtue of this construction, an light emitting
`device can be realized in which heat radiating properties are
`homogenized, heat radiation efficiency is improved, and a
`compact structure is obtained and, thus, the color balance is
`improved and unfavorable phenomena such as lowering in
`the output of light emitting elements and shortening of the
`service life are avoided.
`
`257/98
`
`31 Claims, 6 Drawing Sheets
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`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`U.S. Patent
`
`Dec. 28,2004
`
`Sheet 1 of 6
`
`US 6,834,977 B2
`
`FIG. 1A
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`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`U.S. Patent
`
`Dec. 28,2004
`
`Sheet 2 of 6
`
`US 6,834,977 B2
`
`FIG. 2 A
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`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`U.S. Patent
`
`Dec. 28,2004
`
`Sheet 3 of 6
`
`US 6,834,977 B2
`
`FIG. 3
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`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`U.S. Patent
`
`Dec. 28,2004
`
`Sheet 4 of 6
`
`US 6,834,977 B2
`
`FIG. 5
`
`123a
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`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`U.S. Patent
`
`Dec. 28,2004
`
`Sheet 5 of 6
`
`US 6,834,977 B2
`
`FIG. 7A
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`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`U.S. Patent
`
`Dec. 28,2004
`
`Sheet 6 of 6
`
`US 6,834,977 B2
`
`FIG. 8 A
`
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`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`1
`LIGHT EMITTING DEVICE
`
`US 6,834,977 B2
`
`This invention is based on Japanese application 2000-
`165864 filed Jun. 2, 2000, which is hereby incorporated by
`reference.
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates to a light emitting device, 10
`and more particularly to a light emitting device suitable for
`use, for example, as white light sources for backlight or
`frontlight in liquid crystal display panels.
`2. Description of Related Art
`Various light emitting devices for backlight in full color 15
`liquid crystal display panels are known. Generally, a light
`emitting device (LED) includes an LED chip array com­
`prising an LED for red (R), an LED for green (G), and an
`LED for blue (B). Alight guide section is generally provided
`such that light from the LED chip array enters therein 20
`through an incident face. The light is guided so as to
`propagate through the inside of the light guide section,
`thereby permitting planar backlight to be emitted through an
`outgoing face from the light guide section. Each of the LEDs
`for respective colors R, G, and B has a narrow-band emis- 25
`sion spectrum. Therefore, upon light emission from each
`LED for R, G, and B, lights of R, G, and B from the
`respective LEDs can be mixed together to supply white
`backlight to a liquid crystal display panel. One such example
`is shown in Japanese Patent Laid-Open No. 329044/1999. 30
`Radiation characteristics of each light emitting device
`varies from position to position and the speed of deteriora­
`tion varies for each light emitting element. This tends to
`change the color balance over time. Light emitting elements
`having poor radiation characteristics can generally cause 35
`lowered power output and have shortened service life, which
`is undesirable.
`Some light emitting elements, such as G and B, have both
`positive and negative electrodes on light emitting faces
`thereof, which can increase the number of bonding elements
`coupled to the light emitting elements. With more bonding
`elements coupled to the light emitting elements, a compact
`packaging arrangement is difficult to achieve.
`
`2
`metal connection connects the negative leads on the top and
`bottom surfaces of the insulating base.
`According to a second feature of the invention, a light
`emitting device includes a pair of metal layers provided
`5 respectively on the upper and lower surfaces of an insulating
`base. A plurality of light emitting elements are arranged on
`the metal layer provided on the upper surface of the insu­
`lating base, and a metal connection connects the pair of
`metal layers to each other at a position where at least one of
`the of the plurality of light emitting elements is disposed.
`According to this construction, heat generated from the
`plurality of light emitting elements is released through the
`metal layer provided on the upper surface of the insulating
`base into the air, and, in addition, is transferred through the
`metal connection to the metal layer provided on the lower
`surface of the insulating base and is then released into the air.
`Further, since the radiating surface is increased, the radiation
`efficiency can be improved.
`According to a third feature of the invention, a light
`emitting device includes a substrate comprising a plurality
`of leads provided on an insulating base. A plurality of light
`emitting elements are arranged on a base line along the
`surface of the substrate in its predetermined direction. A
`plurality of bonding wires connect the plurality of light
`emitting elements to the plurality of leads in the predeter­
`mined direction or on one side relative to the base line.
`According to this construction, in the connection of the
`plurality of light emitting elements to the plurality of leads
`through bonding wires, this connection is carried out in such
`a state that the bonding wire has been rendered eccentric.
`This can reduce the size of the device in a direction
`perpendicular to a direction in which the plurality of light
`emitting elements are arrayed. The plurality of light emitting
`elements comprise a first light emitting element having first
`and second electrodes on its light emitting face side and a
`second light emitting element having a first electrode on its
`light emitting face side and a second electrode on its side
`remote from the light emitting face. The term "light emitting
`element" as used herein means a bared chip, such as LED
`(light emitting diode) having first and second electrodes. The
`term "substrate" refers to, for example, a printed board
`formed by providing leads connected to first and second
`electrodes on a base by a circuit printing method, and a
`45 substrate having a lead frame structure formed by placing a
`SUMMARY OF THE INVENTION
`lead frame, corresponding to leads connected to first and
`Accordingly, it is an aspect of embodiments of the inven­
`second electrodes, within a mold and pouring an insulating
`tion to provide a light emitting device in which homoge­
`material into the mold.
`According to a fourth feature of the invention, a light
`neous radiation characteristics can be obtained and, thus, no
`significant change balance in color results from the elapse of 50 emitting device includes a pair of metal layers provided
`time.
`respectively on the upper surface and lower surface of an
`It is another aspect of embodiments of the invention to
`insulating base. A plurality of light emitting elements are
`provide a light emitting device in which improved radiation
`arranged on a base line along the surface of the metal layer,
`efficiency is obtained and unfavorable phenomena such as
`in its predetermined direction, provided on the upper surface
`lowering in power output and shortening of service life of 55 of the insulating base. A metal connection connects the pair
`light emitting elements can be avoided.
`of metal layers to each other at a position where a prede­
`termined light emitting element out of the plurality of light
`It is a further aspect of embodiments of the invention to
`emitting elements is disposed. A plurality of bonding wires
`provide a light emitting device having a compact structure.
`connect the plurality of light emitting elements to the metal
`According to a first
`feature of the invention, a light
`emitting device includes an insulating base having positive 60 layer, provided on the upper surface of the insulating base,
`in the predetermined direction or on one side relative to the
`and negative leads, respectively, provided on top and bottom
`base line.
`surfaces thereof. A LED chip array is arranged on the
`negative lead on the top surface of the insulating base. The
`According to this construction, heat generated from the
`LED chip array is electrically connected to the positive and
`plurality of light emitting elements is released through the
`negative leads on the top surface of the insulating base. A 65 pair of metal layers provided respectively on the upper and
`first metal connection connects the positive leads on the top
`lower surfaces of the insulating base into the air. In addition,
`and bottom surfaces of the insulating base; and a second
`in the connection of the plurality of light emitting elements
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`US 6,834,977 B2
`
`5
`
`3
`4
`to the plurality of leads through bonding wires, this connec­
`FIG. 6 is a plan view showing an embodiment of the
`tion is carried out in such a state that the bonding wire has
`application of the light emitting device according to the first
`been rendered eccentric. This can reduce the size of the
`preferred embodiment of the invention to a backlight appa­
`device in a direction perpendicular to a direction in which
`ratus;
`the plurality of light emitting elements are arrayed.
`FIG. 7A is a diagram showing the upper surface of the
`According to a fifth
`feature of the invention, a light
`light emitting device showing a light emitting device accord­
`emitting device for driving a plurality of LED chips dis­
`ing to a second preferred embodiment of the invention;
`posed in an array to emit a mixed light composed of lights
`FIG. 7B is a cross-sectional view taken on line IV—IV of
`emitted from the plurality of LED chips, an insulating base
`having an upper surface and a lower surface. An LED chip 10
`'
`FIG. 7C is a diagram showing a metal pattern provided on
`connection lead is provided on the upper surface of the
`the upper surface of the light emitting device;
`insulating base. A power supply connection lead is provided
`on the lower surface of the insulating base. A link lead
`FIG. 7D is a diagram showing the lower surface of the
`connects the LED chip connection lead to the power supply
`light emitting device;
`connection lead between the upper and lower surfaces of the
`FIG. 8Ais a diagram showing the upper surface of a light
`insulating base. The LED chip connection lead comprises a 15
`emitting device according to a third preferred embodiment
`plurality of separate leads connected respectively to the
`of the invention;
`plurality of LED chips and a common lead, to which the
`FIG. 8B is a front view;
`plurality of LED chips are connected by common connec-
`8C a cross-sectional view taken on line V V of
`tion and which is loaded with the plurality of LED chips, for
`TT/"1 Q A
`absorbing heat generated from the plurality of LED chips. 20 rlu. OA; ana
`FIG. 8D is a cross-sectional view taken on line VI—VI of
`According to this construction, heat generated from the
`FIG. 8A.
`plurality of LED chips is released, through a common lead
`in the LED chip connection lead provided on the upper
`DESCRIPTION OF PREFERRED
`surface of the insulating base, into the air, and, in addition,
`EMBODIMENTS
`is transferred through the link lead, to the power supply 25
`FIGS. 1A, IB, 1C and ID show a light emitting diode or
`connection lead provided on the lower surface of the insu­
`device (LED) in accordance with the principles of the
`lating base, and is then released into the air. Further, since
`present invention. For the facilitation of understanding, in
`the radiating surface is increased, the radiation efficiency can
`FIG. 1A, a case and a filling member are not shown, and, in
`be improved.
`These and other aspects and features of this invention will 30 FIG. 1C, a resin is not shown. The light emitting device 1
`comprises a printed circuit board 2A on which a metal
`be described in or apparent from the following detailed
`description when taken in conjunction with the accompa­
`pattern to be loaded with LED has been printed. A plurality
`nying drawings, which are a part of this disclosure and
`of LEDs 3 (3R (red), 3G (green), 3B (blue)) are disposed in
`which illustrate, by way of example, preferred embodiments
`an array. The LED array 3 is electrically connected to the
`of the invention.
`35 positive and negative leads on the upper surface 2a of the
`printed circuit board 2A. A case 4 having an opening 4a
`BRIEF DESCRIPTION OF THE DRAWINGS
`provided so as to surround the plurality of LEDs 3. A filling
`The invention will be explained in more detail in con­
`member 5, for example, of a transparent epoxy resin, fins the
`junction with the appended drawings, wherein:
`opening 4a and seals the plurality of LEDs 3 in the case 4.
`FIG. 1A is a diagram showing the upper surface of the
`The printed circuit board 2A includes a base 2 having
`light emitting device in a first preferred embodiment of the 40
`upper, lower and side surfaces 2a, 2c, 2b, respectively.
`invention;
`Preferably, the printed circuit board 2A can be produced in
`FIG. IB is a cross-sectional view taken on line I—I of
`a small size at low cost so that an inexpensive and small-size
`FIG. 1A;
`light emitting device can be achieved.
`FIG. 1C is a diagram showing a metal pattern provided on
`The base 2 is formed of a material having heat resistance
`the upper surface of the light emitting device;
`and high white reflectance, for example, a glass-epoxy resin
`FIG. ID is a diagram showing the lower surface of the
`containing a white colorant having high white reflectance.
`light emitting device;
`The printed circuit board 2A also has a metal pattern
`FIG. 2A is a plan view showing an embodiment of the
`comprising separate leads 6R, 6G, 6B respectively for red
`application of the light emitting device according to the first 5o ^
`n (G) and blue (B) ^ elements 3^ 3G AND 3^
`preferred embodiment of the invention to a backlight appa­
`respectively, printed on the upper surface 2a of the base 2.
`ratus;
`The printed circuit board 2A also has a common lead 6C
`FIG. 2B is a cross-sectional view taken on line II—II of
`common to each light element 3R, 3G, 3B included in the
`FIG. 2A;
`plurality of LEDs 3. A resist 12 (FIG. IB) is applied to the
`FIG. 2C is a cross-sectional view taken on line III—III of 55 iower surfaCe 2c of the base 2 and is configured to help
`FIG. 2A;
`prevent short circuiting among leads 6R, 6G, 6B, 6C.
`FIG. 3 is a diagram showing an LED drive circuit in the
`The separate leads 6R, 6G, 6B comprise electrode faces
`light emitting device according to the first preferred embodi­
`6RJ, 6G1, 6B! provided on the upper surface 2a of the base
`ment of the invention;
`2 and connections 6R2, 6G2, 6B2 provided on the lower
`FIG. 4 is a perspective view of the principal part of an go surface 2c of the base 2. The common lead 6C comprises an
`assembly comprising the light emitting device according to
`electrode face 6CJ provided on the upper surface 2a of the
`the first preferred embodiment of the invention incorporated
`base 2, a connection 6C2 provided on the side face 2b of the
`into a backlight apparatus;
`base 2 and a heat radiating section 6C3 provided on the
`FIG. 5 is a plan view showing an embodiment of the
`lower surface 2c of the base 2. The electrode face 6^ in the
`application of the light emitting device according to the first 65 common lead 6C has a substantially => shape, but could be
`preferred embodiment of the invention to a backlight appa-
`configured to have other shapes as well, for example, any
`ratus;
`arcuate configuration.
`
`45
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`US 6,834,977 B2
`
`15
`
`5
`6
`The electrode faces 61^, 60^ 6B! of the separate leads
`reflection can be realized for all emission wavelengths of R,
`6R, 6G, 6B provided on the upper surface 2a of the base 2
`G, and B. Since all emission wavelengths of R, G and B can
`be enhanced, the power used can be reduced. The case 4 may
`are connected to the connections 6R2, 6G2, 6B2, which are
`be formed of, for example, a white resin, such as polyph-
`provided on the lower surface 2c of the base 2. Through-hole
`thalamide with a white colorant having high white reflec­
`platings 9R, 9G, 9B and a solder 11 filled into the through- 5
`tance incorporated therein or may be formed of a resin
`hole platings 9R, 9G, 9B connect the electrode faces 6RJ,
`wherein a white coating is applied onto the opening 4a.
`6GJ, 6B! to the connections 6R2, 6G2, 6B2. The electrode
`The printed circuit board 2A can be loaded with the LED
`face e C j in the common lead 6C provided on the upper
`surface 2a of the base 2 is connected to the heat radiating
`3 and may be mounted onto the light emitting device mount
`substrate 21, followed by mounting onto the printed circuit
`section 6C3 provided on the lower surface 2c of the base 2
`board 2A, as shown in FIG. 2A. The case 4 can be mounted
`via through-hole platings 10R, 10G, 10B. Solder 11 is filled
`on the board 2A, such that the draft angle of the opening 4a
`into the through-hole platings 10R, 10G, 10B, and the
`can be reduced. The opening 4a defined by the case 4 can be
`connection 6C0. The through-hole platings 10R, 10G, 10B
`are provided adjacent to and below the LEDs 3G, 3B. The
`any configuration although shown as a generally annular
`opening in FIG. 1A.
`LEDs 3G, 3B can generate a large quantity of heat, among
`pjQ ^ opening 4a is provided so
`the plurality of LEDs 3.
`(3est seen
`The side face 2b of the base 2 functions as a face for
`that the center of the plurality of LEDs 3 is spaced from the
`mounting to a light emitting device mount substrate, as will
`center of the opening 4a by a distance "e". In the illustrated
`be described in greater detail below. The connections 6R
`embodiment, the distance "e" is shown in a direction per­
`2'
`6G2, 6B2, 6C2 are connected to a wiring pattern provided on
`pendicular to the horizontally aligned array of LEDs 3, but
`the light emitting device mount substrate 21 (FIGS. 2A, 2B 20
`the distance "e" could also be formed in a direction along the
`and 2C).
`LEDs shown in FIGS. 1A, 1C and ID.
`The plurality of LEDs 3 comprise a blue light emitting
`In the light emitting device 1, heat from the LEDs 3G, 3B,
`element 3B disposed in the center of the array of LEDs, two
`which generate a relatively large quantity of heat, is released
`on
`red light emitting elements 3R disposed adjacent and
`through the common lead 6C into the air. The heat is also
`opposite sides of the blue light emitting element 3B and two 25
`transferred through the through-hole platings 10R, 10G, 10B
`green light emitting elements 3G disposed adjacent to and
`and the solder 11 before being released into the air through
`on opposite sides of the blue light emitting elements 3B. The
`the common lead 6C provided on the lower surface 2c of the
`red light emitting element or LED 3R is formed of, for
`insulated base 2. This allows radiation characteristics among
`example, an AlInGaP-base semiconductor which emits red
`light. The red LED 3R has a first electrode 3a on its upper 3Q the LEDs 3R, 3G, 3B to be homogenized, and, thus, a
`surface eRj and a second electrode 3fc on its lower surface.
`change in color balance over time is reduced. Further,
`The first electrode 3a on the upper surface 2a is electrically
`unfavorable phenomena, such as lowered power output and
`connected to the electrode face eRj of the separate lead 6R
`shortened service life, caused by a temperature rise of the
`for R, for example, using a bonding wire 7R. The second
`LED 3 can be avoided. Since the radiating surface is
`electrode 3fc on the lower surface 2c is electrically and 3S increased, the radiation efEciency can be improved, which
`mechanically connected to the electrode face 6^ of the
`makes it possible to avoid the unfavorable phenomena, such
`common lead 6C and may be bonded thereto, for example,
`as lowered power output and shortened service life of the
`using a conductive adhesive. The green LED 3G comprises,
`LED 3.
`As best seen in FIG. 1A, bonding wires 7R, 7G, 7B, 8R,
`for example, a GaN-base semiconductor which emits a green
`light. The green LED 3G has a first electrode 3a and a 4Q 8G, 8B extend toward the array of LEDs 3 and are extended
`second electrode 3fc on its upper surface. The lower surface
`from this array toward one side thereof. The plurality of
`is mechanically connected to the electrode face 6C! of the
`LEDs 3 can be disposed in an eccentric state relative to the
`common lead 6C with the aid of an adhesive.
`opening 4a. This reduces the width Wj of the opening 4a,
`and can realize a compact structure such that the width W2
`As best shown in FIG. 1A, the first electrode 3a is
`electrically connected to the electrode face 6G! for G 45 of the device 1 has been reduced,
`through the bonding wire 7G. The second electrode 3fc is
`In mixing lights R, G, and B to form white light, light can
`electrically connected to the common electrode face 6C!
`be emitted from the blue LED 3B at full power. Therefore,
`through a bonding wire 8G. The blue LED 3B comprises, for
`light can be efficiently emitted. Further, since the base 2 and
`example, a GaN-base semiconductor which emits blue light.
`the case 4 are formed of a material having high white
`The blue LED 3B has a first electrode 3a and a second 50 reflectance, a high level of reflection can be realized for all
`electrode 3fc on its upper surface. The lower surface is
`emission wavelengths of R, G, and B. Therefore, the emis-
`mechanically connected to the electrode face 6C! of the
`sion efEciency can be enhanced, and the power can be
`common lead 6C with the aid of an adhesive. The first
`reduced. Additionally, the printed board 2A used is one
`electrode 3a is electrically connected to the electrode face
`which can be produced in a small size at low cost. This can
`6B! for B through a bonding wire 7B. The second electrode 55 provide an inexpensive and small-size light emitting device.
`3fc is electrically connected to the common electrode face
`In FIG. 1A, LEDs 3G, 3R, 3B, 3R and 3G for colors G,
`6('l through a bonding wire 8B. The LEDs 3R, 3G, 3B
`R, B, R and G are arranged to be arrayed in the horizontal
`respectively for colors R, G, and B have a light intensity
`direction. The arrangement of LEDs may be changed as
`ratio of, for example, 1:3:1. Therefore, when numbers cor­
`LEDs arranged respectively for colors R, G, B, G and R in
`responding to light intensity ratio of the blue LED 3B, the 6Q the horizontal direction. Even in this arrangement, the same
`red LED 3R, and the green LED 3G are used, as described
`advantage as the first preferred embodiment is obtained. On
`above (one, two, and two, respectively), for example, an
`the other hand, the arrangement of LEDs for colors R, B, G,
`optimal intensity ratio of lights R, G, and B for providing
`B and R to be arrayed may be adopted, when bluish white
`white light through mixing of lights R, G, and B
`light is required to be emitted from the arrangement of
`(for example, R:G:B=2:6:1) can be realized.
`65 LEDs.
`FIGS. 2A to 2C show a backlight apparatus 20 including
`The insulating base 2 and the case 4 are formed of a
`the light emitting device 1. The backlight apparatus 20
`material having high white reflectance, thus a high level of
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1011
`
`

`

`US 6,834,977 B2
`
`7
`8
`through the solder 13 in the connections 6R2, 6G2, 6B2. The
`comprises a light emitting device mount substrate 21, the
`connections 6R2, 6G2, 6B2 are provided on the lower surface
`light emitting device 1 and a light guide section 23. The light
`2c of the substrate 2A while the connection 6C2 is provided
`emitting device mount substrate 21 includes an LED drive
`on the side face 2b. This configuration can prevent the board
`circuit (FIG. 3) having a wiring pattern on its surface 21a.
`The light emitting device 1 is provided on one end of the 5 2A from being toppled backward, for example,
`light emitting device mount substrate 21 and has leads 6R,
`As best seen in FIGS. 2A, 2B and 2C, the backlight
`6G, 6B, 6C connected to a wiring pattern on the light
`apparatus 20 is configured such that the LEDs 3 for respec-
`emitting device mount substrate 21. Light from the light
`tive colors are densely disposed to create a state close to a
`emitting device 1 enters the light guide section 23 through
`point light source. Therefore, white light can be homoge-
`an incident face 23a thereof and is guided so as to propagate lo neously diffused within the light guide plate 230. As a result,
`through the inside of the light guide section 23, thereby
`a diffusion homogeneity of not less than 60% in terms of
`permitting planar white backlight to be exit from the light
`minimum brightness relative to the maximum brightness can
`guide section 23 through an outgoing face 23b.
`be ensured in the outgoing face 23b of the light guide section
`23. This diffusion homogeneity can prevent color shading in
`The light guide section 23 comprises a light guide plate
`230 formed of a transparent material, such as polycarbonate, 15 full color liquid crystal display panels, for example,
`acryl, or glass, a reflection plate 231 which is provided on
`The thickness of the backlight apparatus 20 can be
`the backside 230a of the light guide plate 230 and a diffusion
`reduced by reducing the width W, of the opening 4a in the
`plate 232. The reflection plate 231 is formed of a white film
`light emitting device 1.
`Other embodiments of the light emitting device 1 and the
`of polyethylene terephthalate or the like and is configured to
`reflect light incident to the incident face 23a from the light 20 backlight apparatus 20 will be described below. In the
`emitting device 1. The diffusion plate 232 is provided on the
`descriptions of the further embodiments, only the points of
`surface 230fc of the light guide plate 230 and is formed of,
`difference of each embodiment from the first embodiment
`will be described. That is, in those embodiments, the con­
`for example, a polycarbonate film having concave and
`stituent parts the same as those in the first embodiment are
`convex portions in the outgoing face 23b. The diffusion plate
`232 is configured to diffuse light which is incident from the 25 referenced correspondingly in the drawings and the descrip-
`light emitting device 1 to the incident face 23a and to diffuse
`tion about them will be omitted,
`light which is reflected from the reflection plate 231.
`FIG. 5 shows a backlight apparatus 120, which is an
`alternative embodiment of the backlight apparatus 20 shown
`FIG. 3 shows the LED drive circuit provided on a light
`in FIG. 2. The backlight apparatus 120 includes two incident
`emitting device mount substrate 21. As illustrated, the LED
`drive circuit comprises a power supply 14 and a control unit 30 faces 123a of the light guide section 123 provided on one
`side thereof. One light emitting device 1 is provided on each
`16. The power supply 14 is configured to apply a drive
`incident face 123a. By providing two incident faces 123a,
`voltage to the anode or positive lead of each of LEDs 3R,
`more homogeneous emission characteristics can be realized
`3G, 3B while the control unit 16 is connected to the cathode
`in the widthwise direction for the backlight apparatus 120.
`or negative lead of each of LEDs 3R, 3G, 3B. The control
`FIG. 6 shows backlight apparatus 220, which is another
`unit 16 connects