United States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,998,925
`
`Shimizu et a1.
`[45] Date of Patent: Dec. 7, 1999
`
`
`
`UStHJSFJ‘JSQZSA
`
`[54] LIGHT EMITTING DEVICE HAVING A
`NITRI DE COMPOUN D SEM ICON DUCTOR
`AND A l’HOSPI-IOR CONTAINING A
`GARNET FLUORESCENT MATERIAL
`
`[75]
`
`inventors: Yosllinori Shimizu, Naka—gun; Kenshu
`Sakanu, Anan; Yasunubu Nuguehi,
`Naka-gun; Toshio Moriguehi, Anan, all
`of Japan
`
`[73] Assignee: Niehia Kagaku Kogyo Kabushiki
`Kaisha, Tokushima, Japan
`
`[2]] Appl. No.: 08,902,725
`
`[22]
`
`[30]
`
`Filed:
`
`Jul. 29, 1997
`
`Foreign Application Priority Data
`
`[JP]
`Jul. 29, 19.96
`[JP]
`Sep. 17, 1996
`[JP]
`Sep. [8, mo
`Dec. 2?, 19% [JP]
`Mar. 31, 1997
`[JP]
`
`Japan
`Japan .....
`Japan .....
`Japan .....
`Japan
`
`
`
`8—198585
`8—24-4339
`8—245381
`8—359Ufl4
`Q—IJS'HIIFJ
`
`Int. CI.h ................................ HfllJ 1162; Hill] 63ftl4
`[5]]
` [52] U.S. CI.
`313f503; 313E498; 3133501;
`313502; 2579103
`313x498, 503,
`313501, 502; 2573103
`
`Field of Search
`
`[58]
`
`[56]
`
`References Cited
`U.S. PA'l'L-N'l' DOCUMENTS
`
`3,699,428 JOIN—J2 Pinnow et al.
`.
`4,298,820
`1U1981 Bongcrs ct aI.
`4,227,283
`31988 Van Kemcnade cl al. .
`5,298,537
`3:19.98 Nilta ........................................ 257;"! {13
`
`332.3251
`
`FOREIGN PATENT DOCUMENTS
`
`50-43913
`
`‘“1925
`
`Japan .
`
`55—4898
`(32—21123?
`1-l'r'94'r'l
`5—152609
`7—099345
`1176794
`8-1.1(17'614
`9—{l27642
`
`Japan .
`L-"l‘JSfl
`Japan .
`1.11987
`Japan .
`2.31989
`Japan .
`(#1993
`Japan .
`4.31995
`Japan .
`7,-‘1995
`Japan .
`[#1996
`Japan .
`1.11997
`O'l'IIER PUBLICATIONS
`
`“A New Phosphor for Frying£pot Cathode—Ray Tubes for
`(folor 'l'elevision: Yellow—Emitting Y3a150D—(fe3w,
`(i.
`(ilasse et al., Applied Physics Letters, vol. I], No. 2, pp.
`53—54 (1967).
`“Improved color rendition in high pressure mercury vapor
`lamps”, Mary V. Hofl'man, Journal of 158, pp. 89—9 ]. (1977).
`S. Nakamura, SPIE, 3{X12126—35 (1997).
`
`Prirttrrrr Exrmtirier—Vip Patel
`Assistant ft'Jt'rrmirier—Michael J. Smith
`
`Attorney, Agent, or Firm—Birch, Stewart, Kolasch & Birch,
`LI .1’
`
`[57]
`
`ABSTRACT
`
`The white light emitting diode comprising a light emitting
`component using a semiconductor as a light emitting layer
`and a phosphor which absorbs a part ol‘ light emitted by the
`light emitting component and emits light of wavelength
`difl'erent from that of the absorbed light, wherein the light
`emitting layer of the light emitting component is a nitride
`compound semiconductor and the phosphor contains garnet
`fluorescent material activated with cerium which contains at
`
`least one element selected from the group consisting of Y,
`Lu, Se, La, Gd and Sm, and at least one element selected
`from the group consisting of A1, Ga and In and, and is
`subject to less deterioration of emission characteristic even
`when used with high luminance for a long period of time.
`
`23 Claims, 19 Drawing Sheets
`
`
`
`TCL 1037, Page 1
`LOWES 1037, Page 1
`
`LOWES 1037, Page 1
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 1 of 19
`
`5,998,925
`
`
`
`Fig.2
`299
`
`
` 204
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`
`TCL 1037, Page 2
`LOWES 1037, Page 2
`
`LOWES 1037, Page 2
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 2 0f19
`
`5,998,925
`
`Fig. 3A
`
`
`
`
`
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`
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`
`Fig.38
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`
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`
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`
`TCL 1037, Page 3
`LOWES 1037, Page 3
`
`LOWES 1037, Page 3
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 3 0f19
`
`5,998,925
`
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`TCL 1037, Page 4
`LOWES 1037, Page 4
`
`LOWES 1037, Page 4
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 4 0f19
`
`5,998,925
`
`Fig. 5A
`
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`
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`
`TCL 1037, Page 5
`LOWES 1037, Page 5
`
`LOWES 1037, Page 5
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 5 0f19
`
`5,998,925
`
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`TCL 1037, Page 6
`LOWES 1037, Page 6
`
`LOWES 1037, Page 6
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 6 of 19
`
`5,998,925
`
`
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`
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`TCL 1037, Page 7
`LOWES 1037, Page 7
`
`LOWES 1037, Page 7
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 7 0f19
`
`5,998,925
`
`Fig. 10
`
`601
`
`LED dispiay unit
`
`
`
`
`
`Gradation control unit
`Image data memory
`(RAM)
`(CPU)
`
`
`
`TCL 1037, Page 8
`LOWES 1037, Page 8
`
`LOWES 1037, Page 8
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 8 of 19
`
`5,998,925
`
`Fig.11
`
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`
`TCL 1037, Page 9
`LOWES 1037, Page 9
`
`LOWES 1037, Page 9
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 9 0f19
`
`5,998,925
`
`[—79.1314
`
`Life test
`
`|f=20mA Ta=25°C
`
`FieIative
`
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`(0/0)
`
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`
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`
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`
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`
`TCL 1037, Page 10
`LOWES 1037, Page 10
`
`LOWES 1037, Page 10
`
`

`

`US. Patent
`
`Dec. 7, 1999
`
`Sheet 10 of 19
`
`5,998,925
`
`Fig. 14A
`
`Weathering test
`
`Brightness
`holding rate
`
`(9’0)
`
`60
`
`2O
`
`4O
`
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`
`400
`
`600
`
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`
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`
`TCL 1037, Page 11
`LOWES 1037, Page 11
`
`LOWES 1037, Page 11
`
`

`

`US. Patent
`
`Dec. 7, 1999
`
`Sheet 11 01'19
`
`5,998,925
`
`Fig. 15A
`
`120
`
`Reliability test
`
`100
`
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`
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`
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`TCL 1037, Page 12
`LOWES 1037, Page 12
`
`LOWES 1037, Page 12
`
`

`

`US. Patent
`
`Dec. 1", I999
`
`Sheet 12 of 19
`
`5,998,925
`
`Eat
`
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`TCL 1037, Page 13
`LOWES 1037, Page 13
`
`LOWES 1037, Page 13
`
`

`

`US. Patent
`
`m1,
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`TCL 1037, Page 14
`LOWES 1037, Page 14
`
`LOWES 1037, Page 14
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 14 01'19
`
`5,998,925
`
`100
`
`90
`
`Fig. 18A
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`Wavelength (nm)
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`
`TCL 1037, Page 15
`LOWES 1037, Page 15
`
`LOWES 1037, Page 15
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`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 15 0f19
`
`5,998,925
`
`Fig. 19A
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`Wavelength (nm)
`
`TCL 1037, Page 16
`LOWES 1037, Page 16
`
`LOWES 1037, Page 16
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 16 01'19
`
`5,998,925
`
`380
`
`430
`
`480
`
`530
`
`580
`
`630
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`GAIEISH
`
` (0/0)Ausualu!
`
`
`380
`
`430
`
`480
`
`530
`
`580
`
`630
`
`680
`
`730
`
`Waveiength (nm)
`Fig20C
`‘33 -n----
`80 -ll---
`
`
`
`Waveiength (nm)
`
`TCL 1037, Page 17
`LOWES 1037, Page 17
`
`LOWES 1037, Page 17
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 17 of 19
`
`5,998,925
`
`
`
`
`
`
`
`380
`
`430
`
`480
`
`530
`
`580
`
`630
`
`680
`
`730
`
`Wavelength (nm)
`FI921B
`
`
`-'I------
`90
`g 80 -lII-_---
`
`
`e. 70 -III-----
`e 60 -llI-----
`
`
`g; 50 -l-I----
`
`
`g 40 -l-l-----
`
`
`M-m-H-Il
`,3 20--I-
`
`
`é 0-J-‘-----
`
`
`-J-_----
`80
`730
`430
`480
`530
`580
`630
`680
`
`
`
`o 3
`
`-
`Fig.21C
`
`100
`
`Wavelength (nm)
`
`
`
`
`
`g 90
`a: 80
`g 70
`3.50
`g 50
`3. 40
`q 30
`
`g, 20
`
`380
`
`430
`
`480
`
`530
`
`580
`
`630
`
`680
`
`730
`
`Wavelength (nm)
`
`TCL 1037, Page 18
`LOWES 1037, Page 18
`
`LOWES 1037, Page 18
`
`

`

`US. Patent
`
`Dec. 7,1999
`
`Sheet 18 01'19
`
`5,998,925
`
`80
`
`Fig.22A
`“’0—--r._-—
`
`
`
`90
`I-E="--
`
`
`1 “--
`23---1--‘--
`---|--_-
`
`
`---l--L‘-
`-----“-
`
`EEIIIII‘!
`
`
`
`
`380
`
`430
`
`480
`
`530
`
`58 O
`
`63 0
`
`680
`
`730
`
`F]g_ 228
`
`Wavelength (nm)
`
`
`
`
`
`enuelaa
` (9’6)Ausualul
`
`GAHBIGH
`(0/5)Kusuetw
`
`
`380
`
`430
`
`480
`
`530
`
`580
`
`630
`
`680
`
`730
`
`Fig22C
`
`Wavelength (nm)
`
`
`
`0
`380
`
`4
`430
`
`480
`
`530
`
`580
`
`630
`
`680
`
`730
`
`Wavelength (urn)
`
`TCL 1037, Page 19
`LOWES 1037, Page 19
`
`LOWES 1037, Page 19
`
`

`

`US. Patent
`
`Dec. 7, 1999
`
`Sheet 19 of 19
`
`5,998,925
`
`600650700750
`
`550
`
`400450500
`
`350
`
`0
`
`
`
`Wavelength(nm)
`
`TCL 1037, Page 20
`LOWES 1037, Page 20
`
`Fig.23
`
`100
`
`O
`(I)
`
`O
`(0
`
`C)
`Vt
`
`20
`
`Relative intensity (%)
`
`LOWES 1037, Page 20
`
`

`

`5,998,925
`
`2
`
`1
`LIGHT EMITTING DEVICE HAVING A
`NITRIDE COMPOUND SEMICONDUCTOR
`AND A PHOSPHOR CONTAINING A
`GARNET FLUORESCENT MATERIAL
`
`BACKGROUND OF THE INVENTION
`
`1!]
`
`'IS
`
`3!]
`
`I.) Ill
`
`in a cup
`large energy band gap of light emitting layer,
`provided at the tip of a lead frame, and having a fluorescent
`material
`that absorbs light emitted by the light emitting
`component and emits light of a wavelength different from
`that of the absorbed light (wavelength conversion), con-
`tained in a resin mold which covers the light emitting
`component.
`The light emitting diode disclosed as described above
`capable of emitting white light by mixing the light of a
`plurality of sources can be made by using a light emitting
`component capable of emitting blue light and molding the
`light emitting component with a resin including a fluorescent
`material that absorbs the light emitted by the blue light
`emitting diode and emits yellowish light.
`IIowever, conventional light emitting diodes have such
`problems as deterioration of the fluorescent material leading
`to color tone deviation and darkening of the fluorescent
`material resulting in lowered eliieiency of extracting light.
`Darkening here refers to, in the case of using an inorganic
`fluorescent material such as ((fd, Zn)S fluorescent material,
`for example, part of metal elements constituting the fluo-
`rescent material precipitate or change their properties lead—
`ing to coloration, or,
`in the case of using an organic
`fluorescent material, coloration due to breakage of double
`bond in the molecule. Especially when a light emitting
`component made of a semiconductor having a high energy
`baan gap is used to improve the conversion efliciency of the
`fluorescent material (that is, energy of light emitted by the
`semiconductor is increased and number of photons having
`energies above a threshold which can be absorbed by the
`fluorescent material increases, resulting in more light being
`absorbed), or the quantity of fluorescent material consump—
`tion is decreased (that is, the fluorescent material is irradi—
`ated with relatively higher energy}, light energy absorbed by
`the lluorescent material
`inevitably increases resulting in
`more significant degradation ot'the lluoreseent material. Use
`ofthe light emitting component with higher intensity of light
`emission for an extended period of time causes further more
`signilicant degradation of the lluorescent material.
`Also the fluorescent material provided in the vicinity of
`the light emitting component may be exposed to a high
`temperature such as rising temperature of the light emitting
`component and heat transmitted from the external environ—
`ment (for example, sunlight
`in case the device is used
`outdoors).
`Further, some fluorescent materials are subject to accel-
`erated deterioration due to combination of moisture entered
`
`introduced during the production)
`from the outside or
`process, the light and heat transmitted from the light emit-
`ting component.
`When it comes to an organic dye of ionic property, direct
`current electric field in the vicinity of the chip may cause
`el‘ctrophoresis, resulting in a change in the color tone.
`SUMMARY ()1: THE INVENTION
`
`1. (I'ield of the Invention)
`The present
`invention relates to a light emitting diode
`used in LED display, back light source, traffic signal, trail—
`way signal,
`illuminating switch,
`indicator, etc. More
`particularly,
`it relates to a light emitting device (LED)
`comprising a phosphor, which converts the wavelength of
`light emitted by a light emitting component and emits light,
`and a display device using the light emitting device.
`2. (Description of Related Art)
`A light emitting diode is compact and emits light of clear
`color with high efficiency. It is also free from such a trouble
`as burn-out and has good initial drive characteristic, high
`vibration resistance and durability to endure repetitive
`ONIOFF operations, because it is a semiconductor element.
`Thus it has been used widely in such applications as various
`indicators and various light sources. Recently light emitting
`diodes for RGB (red, green and blue} colors having ultra—
`high luminance and high efliciency have been developed,
`and large screen LED displays using these light emitting
`diodes have been put
`into use. The LEI) display can be
`operated with less power and has such good characteristics
`as light weight and long life, and is therefore expected to be
`more widely used in the future.
`Recently, various attempts have been made to make white
`light sources by using light emitting diodes. Because the
`light emitting diode has a favorable emission spectrum to
`generate monochromatic light, making a light source for
`white light requires it to arrange three light emitting com—
`ponents ofR, G and B closely to each other while dilfusing
`and mixing the light emitted by them. When generating
`white light with such an arrangement, there has been such a
`problem that white light of the desired tone cannot be
`generated due to variations in the tone, luminance and other
`factors ofthe light emitting component. Also when the light
`emitting components are made of dilferent materials, elec-
`tric power required for driving differs from one light emit-
`ting diode to another, making it necessary to apply dilferent
`voltages dilferent light emitting components, which leads to
`complex drive circuit. Moreover, because the light emitting
`components are semiconductor light emitting components,
`color tone is subject to variation due to the diflerence in
`temperature characteristics, chronological changes and oper—
`ating environment, or unevenness in color may be caused _
`due to failure in uniformly mixing the light emitted by the
`light emitting components. 'l'hus light emitting diodes are
`efl’ective as light emitting devices for generating individual
`colors, although a satisfactory light source capable of emit—
`ting white light by using light emitting components has not
`been obtained so far.
`
`'4;'41
`
`4O
`
`45
`
`_
`
`In order to solve these problems, the present applicant
`previously developed light emitting diodes which convert
`the color of light, which is emitted by light emitting
`components, by means ofa fluorescent material disclosed in
`Japanese Patent Kokai Nos. 5452609, 7-99345, 1176794
`and 8-8614. The light emitting diodes disclosed in these
`publications are such that, by using light emitting compo—
`nents of one kind, are capable of generating light of white
`and other colors, and are constituted as follows.
`The light emitting diode disclosed in the above gazettes
`are made by mounting a light emitting component, having a
`
`()0
`
`()5
`
`Thus, an object of the present invention is to solve the
`problems described above and provide a
`light emitting
`device which experiences only extremely low degrees of
`deterioration in emission light intensity, light emission etfi—
`ciency and color shift over a long time of use with high
`luminance.
`
`The present applicant completed the present invention
`through researches based on the assumption) that a light
`emitting device having a light emitting component and a
`fluorescent material must meet the following requirements
`to achieve the above-mentioned object.
`
`TCL 1037, Page 21
`LOWES 1037, Page 21
`
`LOWES 1037, Page 21
`
`

`

`5,998,925
`
`3
`(l) The light emitting component must be capable of
`emitting light of high luminance with light emitting char—
`acteristic which is stable over a long time of use.
`(2) The fluorescent material beint1gprovided1n the vicinity
`ol the high--luminance light emitting component, must show
`excellent resistance against light and heat so that the prop-
`erties thereof do not change even when used over an
`extended period of time while being exposed to ligit of high
`intensity emitted by the light emitting component
`(particularly the fluorescent material provided in the vicinity
`of the light emitting component is exposed to light of a
`radiation intensity as high as about 30 to 40 times that of
`sunlight according to our estimate, and is required to have
`more durability against light as light emitting component of
`higher luminance is used).
`(3} With regard to the relationship with the light emitting
`component,
`the fluorescent material must be capable of
`absorbing with high efliciency the light of high monochro—
`maticity emitted by the light emitting component and emit—
`ting light of a wavelength different from that of the light
`emitted by the light emitting component.
`Thus the present
`invention provides a light emitting
`device, comprising a light emitting component and a phos—
`phor capable of absorbing a part of light emitted by the light
`emitting component and emitting light of wavelength dif-
`ferent from that of the absorbed light; wherein said light
`emitting component comprises a nitride compound semi—
`conductor represented by the formula:
`InfGaJ-AJKN where
`(téi, Oéj, 02k and i+j+k=l) and said phosphor contains a
`garnet lluorescent material comprising 1) at
`least one ele-
`ment selected from the group consisting of Y, Lu, Sc, I_a, (id
`and Sm, and 2} at least one element selected from the group
`consisting ofAl, Ga and In, and being activated with cerium.
`The nitride compound semiconductor (generally repre—
`sented by chemical fon'nula [oi-(iaJAlkN where Uéi, OE],
`(ll—3k and i+j+k=l) mentioned above contains various mate-
`rials including InGaN and GaN doped with various impu—
`rities.
`
`1!]
`
`'IS
`
`3!]
`
`I.) 'JI
`
`f4;'41
`
`4
`
`In the light emitting device of the present invention, the
`phosphor may be a fluorescent material represented by a
`general
`formula (Re1_,Sm,}3(Al1_,.Gas}5012:Ce, where
`UEKI and (lgs‘él and Re is at least one selected from Y
`and (id, in which case good characteristics can be obtained
`similarly to the case where the yttrium—aluminum—garnet
`fluorescent material is used.
`
`Also in the light emitting device of the present invention,
`it is preferable, for the purpose of reducing the temperature
`dependence of light emission characteristics (wavelength of
`emitted light,
`intensity of light emission, etc),
`to use a
`lluorescent material
`represented by a general
`formula
`{Y1 --1"q “(id (.e Sm )._3(/\l_ (ia_)501: as the phosphor,
`where 02psitii, 0.0035q 50.2, 0.0003Er £0.08 and
`Oés El.
`
`Also in the light emitting device of the present invention,
`the phosphor may contain two or more yttrium-aluminum-
`garnet lluorescent materials, activated with cerium, of dif-
`ferent compositions including Y and A]. With this
`configuration,
`light of desired color can be emitted by
`controlling the emission spectrum of the phosphor according
`to the property (wavelength of emitted light) of the light
`emitting component.
`Further
`in the light emitting device of the present
`invention, in order to have light of a specified wavelength
`emitted by the light emitting device, it is preferable that the
`phosphor contains two or more fluorescent materials of
`different compositions represented by general
`formula
`(Re._,Sm,)_3(/\l.__,(ia_3.)5()1::(fe, where (l§r<l and Uésél
`and Re is at least one selected from Y and (id.
`
`Also in the light emitting device of the present invention,
`in order to control
`the wavelength of emitted light,
`the
`phosphor may contain a first
`lluorescent material repre-
`sented by general formula Y3(Al1__,(ia_3)5().2:(_‘e and a sec-
`ond fluorescent material represented by general formula
`Re_~,1¢'t150J 3:Ce, where Oésél and Re is at least one selected
`from Y, (ia and La.
`Also in the light emitting device of the present invention,
`in order to control
`the wavelength of emitted light,
`the
`phosphor may be an yttrium—aluminum—garnet fluorescent
`material containing a first fluorescent material and a second
`lluorescent material, with dilTerent parts of each yttrium
`being substituted with gadolinium.
`l-‘urther
`in the light emitting device of the present
`invention, it is preferable that main emission peak of the
`light emitting component is set within the range from 400
`nm to 530 nm and main emission wavelength of the phos—
`phor is set to be longer than the main emission peak of the
`light emitting component. This makes it possible to elli-
`ciently emit white light.
`Further
`in the light emitting device of the present
`invention, it is preferable that the light emitting layer of the
`light emitting component contains gallium nitride semicon-
`ductor which contains In, and the phosphor is yttrium-
`aluminum—garnet fluorescent material wherein part ofAl is
`substituted by Ga so that the proportion of GatAl is within
`the range from 1:] to 4:6 and part on is substituted by (id
`so that the proportion of Y:(id is within the range from 4:1
`to 2:3. Absorption spectrum of the phosphor which is
`controlled as described above shows good agreement with
`that of light emitted by the light emitting component which
`contains gallium nitride semiconductor including In as the
`light emitting layer, and is capable of improving the con-
`version efliciency (light emission efficiency). Also the light,
`generated by mixing blue light emitted by the light emitting
`component and fluorescent light of the fluorescent material,
`is a white light of good color rendering and, in this regard,
`an excellent light emitting device can be provided.
`
`TCL 1037, Page 22
`LOWES 1037, Page 22
`
`The phosphor mentioned above contains various materi—
`als defined as described above, including Y3AISO3QICe and
`(td,tn_,0,,:(7e.
`llecause the light emitting device of the present invention
`uses the light emitting component made of a nitride com—
`pound semiconductor capable of emitting light with high
`luminance, the light emitting device is capable of emitting
`light with high luminance. Also the phosphor used in the
`light emitting device has excellent resistance against light so
`that the fluorescent propertiesthereofexperience less change
`even when used over an extended period oftime while being _
`exposed to light of high intensity. This makes it possible to
`reduce the degradation of characteristics during long period
`of use and reduce deterioration due to light of high intensity
`emitted by the light emitting component as well as extra—
`neous light (sunlight including ultraviolet light, etc.) during _
`outdoor use, thereby to provide a light emitting device which
`experiences extremely less color shift and less luminance
`decrease. The light emitting device of the present invention
`can also be used in such applications that require response
`speeds as high as 120 nsec.,
`for example, because the
`phosphor used therein allows after glow only for a short
`period of time.
`The phosphor used in the light emitting diode of the
`present invention preferably contains an yttrium—aluminum—
`garnet fluorescent material that contains Y and At, which
`enables it
`to increase the luminance of the light emitting
`device.
`
`4O
`
`45
`
`(JD
`
`()5
`
`LOWES 1037, Page 22
`
`

`

`5,998,925
`
`5
`The light emitting device according to one embodiment of
`the present invention comprises a substantially rectangular
`optical guide plate provided with the light emitting compo—
`nent mounted on one side face thereofvia the phosphor and
`surfaces of which except
`for one principal surface are
`substantially covered with a reflective material, wherein
`light emitted by the light emitting component is turned to
`planar light by the optical guide plate and the phosphor, and
`is output from the principal surface of the optical guide
`plate.
`The light emitting device according to another embodi—
`ment ofthe present invention has a substantially rectangular
`optical guide plate, which is provided with the light emitting
`component mounted on one side face thereof and the phos-
`phor installed on one principal surface with surfaces thereof
`except for the principal surface being substantially covered
`with a reflective material, wherein light emitted by the light
`emitting component is turned to planar light by the optical
`guide plate and the phosphor, and is output from the prin-
`cipal surface of the optical guide plate.
`The LED display device according to the present inven—
`tion has an LED display device comprising the light emitting
`devices of the present invention arranged in a matrix and a
`drive circuit which drives the LEI) display device according
`to display data which is input thereto. This configuration
`makes it possible to provide a relatively low—priced LED
`display device which is capable of high—definition display
`with less color unevenness due to the viewing angle.
`The light emitting diode according to one embodiment of
`the present invention comprises:
`a mount lead having a cup and a lead;
`an LED chip mounted in the cup of the mount lead with
`one of electrodes being electrically connected to the mount
`lead;
`a transparent coating material filling the cup to cover the
`LED chip; and
`a light emitting diode having a molding material which
`covers the LED chip covered with the coating material
`including the cup of the mount lead,
`the inner lead and
`another electrode of the LEI) chip, wherein
`the LEI) chip is a nitride compound semiconductor and
`the coating material contains at least one element selected
`from the group consisting of Y, Lu, Sc, La, Gd and Sm, at
`least one element selected from the group consisting of A],
`(la and In and a phosphor made of garnet
`lluorescent
`material activated with cerium.
`
`The phosphor used in the light emitting diode of the
`present
`invention) preferably contains yttrium—aluminum—
`garnet lluorescerit material that contains Y and Al.
`In the light emitting diode of the present invention, the
`phosphor may be a fluorescent material represented by a
`general
`formula (Re,_,Sm,.)_,(Al,__,Ga_,)50,::Ce, where
`0% rd and Oésél and Re is at least one selected from Y
`and (id.
`
`Also in the light emitting diode of the present invention,
`a fluorescent material represented by a general
`formula
`(Y,_),,_,,_,GdPCequ,)_,(A],__,Ga_,)5012 may be used as the
`phosphor, where Oép 20.8, 0.003éq $0.2, (t.0003§r§0.08
`and U‘és‘él.
`
`In the light emitting diode of the present invention, the
`phosphor preferably contain two or more yttrium-
`aluminum—garnet
`fluorescent materials, activated with
`cerium, of different compositions including Y and Al,
`in
`order to control the emitted light to a desired wavelength.
`In the light emitting diode of the present
`invention,
`similarly,
`two or more lluorescent materials of different
`
`It]
`
`'IS
`
`3!]
`
`I.) 'JI
`
`f4;'41
`
`4O
`
`45
`
`(JD
`
`()5
`
`6
`compositions represented by a general formula (Re I_,Smr)3
`{AIM Ga_,)50,::Ce, where [téml and (tésél and Re is at
`least one selected from Y and Gd may be used as the
`phosphor in order to control the emitted light to a desired
`wavelength.
`invention,
`In the light emitting diode of the present
`similarly, a first fluorescent material represented by a general
`formula Y3(Al 1_,.Ga_,.)5012:Ce and a second fluorescent
`material represented by a general formula ReSAISOnfe,
`maybe used as the phosphor where (IEsE l and Re is at least
`one selected from Y, (la and La,
`in order to control
`the
`emitted light to a desired wavelength.
`invention,
`In the light emitting diode of the present
`similarly, yttrium—aluminum—garnet fluorescent material a
`first fluorescent material and a second fluorescent material
`
`may be used wherein part of yttrium being substituted with
`gadolinium to different degrees of substitution as the
`phosphor, in order to control the emitted light to a desired
`wavelength.
`Generally, a fluorescent material which absorbs light of a
`short wavelength and emits light of a long wavelength has
`higher efliciency than a fluorescent material which absorbs
`light of a long wavelength and emits light of a short
`wavelength. It is preferable to use a light emitting conipo—
`nent which emits visible light than a light emitting compo-
`nent which emits ultraviolet
`light
`that degrades resin
`(molding material, coating material, etc}. Thus for the light
`emitting diode of the present invention, for the purpose of
`improving the light emitting efficiency and ensure long life,
`it is preferable that main emission peak of the light emitting
`component be set within a relatively short wavelength range
`of 400 nm to 530 nm in the visible light region, and main
`emission wavelength ofthe phosphor be set to be longer than
`the main emission peak of the light emitting component.
`With this arrangement, because light converted by the
`fluorescent material has longer wavelength than that of light
`emitted by the light emitting component,
`it will not be
`absorbed by the light emitting component even when the
`light emitting component is irradiated with light which has
`been reflected and converted by the fluorescent material
`(since the ener