WO2007001117A2 - White light emitting diode based on mixing of tri-color phosphors - Google Patents

White light emitting diode based on mixing of tri-color phosphors Download PDF

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Publication number
WO2007001117A2
WO2007001117A2 PCT/KR2006/001916 KR2006001916W WO2007001117A2 WO 2007001117 A2 WO2007001117 A2 WO 2007001117A2 KR 2006001916 W KR2006001916 W KR 2006001916W WO 2007001117 A2 WO2007001117 A2 WO 2007001117A2
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Prior art keywords
light emitting
emitting diode
white light
phosphors
color
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PCT/KR2006/001916
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French (fr)
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WO2007001117A3 (en
Inventor
Joung Kyu Park
Chang Hae Kim
Kyoung Jae Choi
Jae Myung Kim
Kyung Nam Kim
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Korea Research Institute Of Chemical Technology
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Publication of WO2007001117A2 publication Critical patent/WO2007001117A2/en
Publication of WO2007001117A3 publication Critical patent/WO2007001117A3/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7728—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing europium
    • C09K11/7737—Phosphates
    • C09K11/7738—Phosphates with alkaline earth metals
    • C09K11/7739—Phosphates with alkaline earth metals with halogens
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7728—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing europium
    • C09K11/77342—Silicates
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
    • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/45099—Material
    • H01L2224/451—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45144—Gold (Au) as principal constituent
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
    • H01L2224/48247—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a bond pad of the item
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
    • H01L2224/48257—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a die pad of the item
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/49—Structure, shape, material or disposition of the wire connectors after the connecting process of a plurality of wire connectors
    • H01L2224/491—Disposition
    • H01L2224/49105—Connecting at different heights
    • H01L2224/49107—Connecting at different heights on the semiconductor or solid-state body
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    • H01L2224/73—Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
    • H01L2224/732—Location after the connecting process
    • H01L2224/73251—Location after the connecting process on different surfaces
    • H01L2224/73265—Layer and wire connectors
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    • H01L2224/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L2224/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
    • H01L2224/85909—Post-treatment of the connector or wire bonding area
    • H01L2224/8592—Applying permanent coating, e.g. protective coating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/181—Encapsulation
    • H—ELECTRICITY
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    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/50—Wavelength conversion elements
    • H01L33/501—Wavelength conversion elements characterised by the materials, e.g. binder
    • H01L33/502—Wavelength conversion materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/50—Wavelength conversion elements
    • H01L33/501—Wavelength conversion elements characterised by the materials, e.g. binder
    • H01L33/502—Wavelength conversion materials
    • H01L33/504—Elements with two or more wavelength conversion materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Definitions

  • the present invention relates to a white light emitting diode based on the mixing of tri-color phosphors .
  • the present invention relates to a light emitting diode prepared by coating red, green and blue phosphors on a UV light emitting diode chip and transmitting light , wherein each of the red, green and blue phosphors emits light in the specific wavelength region from 380 to 410 nm and is comprised at a predetermined proportion to obtain the phosphor mixture , thereby providing improved light emitting intensity, superior white light and a high efficiency of greater than 10 mW.
  • a light emitting diode is a PN junction diode that, when a voltage is applied, emits the energy corresponding to the band gap formed by electron-hole recombination in the form of light . If the PN junction of silicon led the innovation in electronics and information technology, the PN junction of group III - V compound semiconductors may be said to lead the innovation of optics.
  • a method of the first group is to bind phosphors on a single blue or UV light emitting diode chip and the other is to combine two or three light emitting diode chips to obtain white light .
  • the above method was introduced in late 1990s as the high-brightness blue light emitting diode became commercially available.
  • the blue light emitting diode is used as reference light source.
  • the blue light is illuminated to a yellow YAG (yttrium aluminum garnet) phosphor, the incident light is excited and lights in the wavelength range of 500 to 780 nm are emitted.
  • White light is obtained from the combination of these lights .
  • the white light emitting diode tends often causes a flash due to the large difference in wavelength between blue and yellow colors .
  • the first multi - chip type white light emitting diode introduced was to use three combined chips of red, green and blue colors. But, this had problems of no uniformity in operation voltage of each chip , change in color coordinates caused by different output of each chip depending on ambient temperature, need for additional driving circuit, etc . Accordingly, it was thought necessary to control brightness of each light emitting diode through circuit design in order to obtain various colors than to employ a white light emitting diode .
  • the color coordinate system is based on the color matching functions defined by the Commission Internationale de PEclairage (CIE) in 1931. It is now widely adopted in industries as color display standard since it enables expression of colors based on color mixing . Occasionally, the white color is defined more rigorously than defined by the CIE system. For example, the SAE (Society of Automotive Engineers ) Standard J578 strictly defines the white color used in automobiles .
  • BCW binary complementary light emitting diode
  • white light can be obtained by mixing orange and blue-green at a proportion of 4:1.
  • the performance index of the InGaAlP light emitting diode which can emit light in the range of from orange to red, exceeds 100 lm/W
  • the luminous efficiency of the BCW white light emitting diode is comparable to that of fluorescent light .
  • the present inventors made intensive efforts to improve luminous efficiency of the white light emitting diode manufactured from a single chip .
  • a white light emitting diode prepared by coating a phosphor mixture comprising phosphors of red, green and blue colors, which emits purple light in the wavelength range of 380 to 410 nm, and illuminating purple light in the wavelength range of 380 to 410 nm has superior color rendering index (CRI) and easily controllable color temperature because of the three phosphors emitting light at 460 nm, 520 nm and 580 nm, respectively .
  • CRI color rendering index
  • the white light emitting diode has significantly improved luminous intensity and offers superior color vividness because it emits light in the broad range of from 380 to 700 nm.
  • an objective of the present invention is to provide a white light emitting diode which offers significantly improved luminous intensity and color vividness using specific tri-color phosphors and purple light in the specific wavelength range .
  • the present invention relates to a white light emitting diode prepared by coating red, green and blue phosphors on a UV light emitting diode chip and illuminating light, wherein the phosphors comprise:
  • the present invention relates to a white light emitting diode using a single chip and tri-color phosphors, which is prepared by coating a mixture of red, green and blue phosphors which emits purple light in the wavelength range of 380 to 410 nm and illuminating purple light in said w wavelength range .
  • a white light emitting diode is prepared by using a blue light emitting chip with a yellow phosphor or by coating a mixture of red, green and blue phosphors on a UV light emitting chip .
  • the present invention uses the latter technique and is characterized by selecting phosphors emitting light in specific wavelength range and mixing them with a specific proportion in order to improve luminance and color vividness .
  • phosphors emitting light at 185 nm , 254 nm and 365 nm were mixed for use in the fluorescent lamp.
  • the present invention is for use in the UV LED.
  • phosphors emitting light in the wavelength range of 380 to 410 nm are selected and mixed at a specific proportion to offer improved luminous intensity and superior color vividness .
  • Such prepared white light emitting diode has a high efficiency of 10 mW or better.
  • a phosphor mixture is coated directly or indirectly on a UV light emitting diode chip comprising a packaging frame or a lead frame .
  • the packaging frame may be a printed circuit board (PCB) frame , a ceramic frame , a silicon frame or a metal frame .
  • the present invention relates to the use of a mixture of red, green and blue phosphors, which can emit light in the wavelength range of 380 to 410 nm , at a specific mixing rate .
  • the phosphors are the ones commonly used in the art and are not particularly limited in the present invention , as long as emission of light in the afore-mentioned wavelength range is possible.
  • a silicate-based and sulfide-based red phosphor having a broad bandwidth and a center wavelength of 580 nm, for example, Si SiO :Eu, SrS :Eu or CaS :Eu, is used.
  • a green phosphor one having a broad bandwidth and a center wavelength of 520 nm, that is, alkaline earth metal silicate , alkaline earth metal gallium sulfide or a mixture thereof is preferably used.
  • a blue phosphor one having a broad bandwidth and a center wavelength of 460 nm, that is, alkaline earth metal silicate , alkaline earth metal aluminate , halophosphate or a mixture thereof are preferably used.
  • Ca MgSi O :Eu, Ba MgSi O :Eu, Sr MgSi O :Eu, BaMgAl O :Eu, Sr (PO ) Cl:Eu, Sr (PO ) Cl:Eu or Mg (PO ) Cl:Eu may be used.
  • the above phosphors one having a broad bandwidth and a center wavelength of 460 nm, that is, alkaline earth metal silicate , alkaline earth metal aluminate , halophosphate or a mixture thereof are preferably used.
  • each of the red , green and blue phosphor is comprised in the amount of 10 to 30 wt% , 30 to 50 wt% and 30 to 50 wt%, respectively . If the content of the red phosphor is below 10 wt%, a white color with a strong blue-green tone is obtained while if it exceeds 50 wt%, a white color with a strong red tone is obtained. If the content of the green phosphor is below 30 wt%, white color is not obtained while if it exceeds 50 wt%, a white color with a strong green tone is obtained .
  • the content of the blue phosphor is below 30 wt%, a white color with a strong green-red tone is obtained while if it exceeds 50 wt%, a white color with a strong blue tone is obtained .
  • the afore-mentioned mixing rate is an important factor because luminance efficiency , color temperature and CRI are determined by the mixing rate of the red , green , and blue phosphors .
  • the tri-color phosphors After coating the tri-color phosphors , purple light in the wavelength range of 380 to 410 nm is illuminated to obtain a white light emitting diode .
  • an epoxy resin is added during the coating .
  • the weight proportion of the tri-color phosphors and the epoxy resin is an important factor that determines luminance efficiency and color temperature .
  • the epoxy resin is added so that the weight proportion of the phosphor mixture becomes 20 to 50 wt% . If the proportion of the phosphor mixture is below 20 wt%, the peak resulting from the UV chip becomes too strong. In contrast, a proportion of the phosphor mixture exceeding 50 wt% is inefficient .
  • the resultant white light emitting diode has improved light emitting intensity, superior white color and high luminance efficiency of 10 mW or higher, preferably 10 to 30 mW, which is significantly better than the conventional ones.
  • Fig. 1 illustrates a package type white light emitting diode .
  • Fig. 2 illustrates a tower type light emitting diode .
  • Fig. 3 shows the emission spectra of the red, green and blue phosphors used in the present invention, when they are excited by light with a wavelength of 405 nm.
  • Fig. 4 shows the emission spectra of the white light emitting diodes prepared in
  • Fig. 5 shows the emission spectra of the white light emitting diode prepared in
  • Fig. 6 shows the color coordinate of the white light emitting diode prepared in
  • Fig. 7 shows the emission spectra of the white light emitting diode prepared in
  • Fig. 8 shows the color coordinate of the white light emitting diode prepared in
  • Fig. 9 shows the emission spectra of the white light emitting diode prepared in
  • Fig. 1 0 shows the color coordinate of the white light emitting diode prepared in
  • Fig. 1 1 shows the emission spectra of the white light emitting diode prepared in
  • Example 1 [52] Package type white light emitting diode and tower type white light emitting diode illustrated in Fig. 1 and Fig. 2, respectively, were prepared .
  • the white light emitting diode comprised an electrode and an LED chip (1) bonded and fixed by a silver (Ag) paste (2).
  • the LED chip was electrically connected to the electrode by a gold (Au) wire (4) .
  • the LED chip was held in a hole cup , which had been formed by hardening treatment of the mixture of epoxy resin (5) and tri-color phosphors (3) . Subsequently, purple light in the wavelength range of 380 to 410 nm was illuminated . Then, resin molding was performed to obtain the white light emitting diode . In Fig. 2, the hardening treatment was performed in a reflector .
  • Luminance intensity of the red, green and blue phosphors used in the present invention is shown in Fig. 3.
  • Fig. 4 shows the luminous intensity of the white light emitting diodes prepared in Examples 1 to 3. Table 1
  • Examples 9 to 11 A white light emitting diode was prepared using the tri-color phosphors of Example 1 to 3 and epoxy resin, with the mixing rate given in Table 2 below.
  • Luminous intensity and color coordinate of the resultant white light emitting diode are shown in Figs. 5 to 10.
  • Table 2 Luminous intensity and color coordinate of the resultant white light emitting diode are shown in Figs. 5 to 10.
  • Comparative Example 1 A light emitting diode was prepared in the same manner as in Example 1, with a mixing rate of red, green and blue phosphors of 40 : 30 : 30 by weight. As seen in Fig. 1 1 , a white color with a strong red tone was obtained when the content of the red phosphor was high.
  • Comparative Example 1 was for the case where the content of each of the phosphors falls outside the range defined in the present invention. It was confirmed that the tri-color phosphors have to be mixed at a specific proportion to obtain white LED and that white colors of all region can be attained by varying the mixing rate of the tri-color phosphors .
  • the present invention provides a white light emitting diode, which offers improved light emitting intensity , superior white color and high luminance efficiency of greater than 10 mW, by using red, green and blue phosphors emitting light in a specific wavelength range with a specific mixing rate .

Abstract

The present invention relates to a white emitting diode based on the mixing of tri-color phosphors, more particularly to a light emitting diode prepared by coating red, green and blue phosphors (3) on a UV light emitting diode chip (1) and transmitting light, which is characterized in that each of the red, green and blue phosphors absorbs light in the specific wavelength region from 380 to 410 nm and is comprised at a specific proportion to obtain the phosphor mixture, thereby offering improved light emitting intensity, superior white light and a high efficiency.

Description

Description WHITE LIGHT EMITTING DIODE BASED ON MIXING OF
TRI-COLOR PHOSPHORS
[i]
Technical Field
[2]
[3] The present invention relates to a white light emitting diode based on the mixing of tri-color phosphors . M ore particularly, the present invention relates to a light emitting diode prepared by coating red, green and blue phosphors on a UV light emitting diode chip and transmitting light , wherein each of the red, green and blue phosphors emits light in the specific wavelength region from 380 to 410 nm and is comprised at a predetermined proportion to obtain the phosphor mixture , thereby providing improved light emitting intensity, superior white light and a high efficiency of greater than 10 mW.
[4]
Background Art
[5]
[6] Basically, a light emitting diode (LED) is a PN junction diode that, when a voltage is applied, emits the energy corresponding to the band gap formed by electron-hole recombination in the form of light . If the PN junction of silicon led the innovation in electronics and information technology, the PN junction of group III - V compound semiconductors may be said to lead the innovation of optics.
[7] The technique of using InGaN -based light emitting diodes to attain white light has been adopted worldwide and is generally classified into two groups.
[8] A method of the first group is to bind phosphors on a single blue or UV light emitting diode chip and the other is to combine two or three light emitting diode chips to obtain white light .
[9] The above method was introduced in late 1990s as the high-brightness blue light emitting diode became commercially available. The blue light emitting diode is used as reference light source. When the blue light is illuminated to a yellow YAG (yttrium aluminum garnet) phosphor, the incident light is excited and lights in the wavelength range of 500 to 780 nm are emitted. White light is obtained from the combination of these lights . However, the white light emitting diode tends often causes a flash due to the large difference in wavelength between blue and yellow colors .
[10] Thus , it is difficult to produce white light emitting diodes with identical color coordinates in large quantity and it is also difficult to control color temperature and color rendering index (CRI), which are important factors of an illuminating light source. Further , temperature-dependent color change is another critical problem . Consequently, there has been an attempt to add a red light emitting phosphor to broaden the emission spectrum .
[11] As UV light emitting diodes are developed as a light source for excitation, it has become possible to attain a white light emitting diode with a single chip . This technique is quite similar to the one attaining the fluorescent lamp light with the 185 nm, 254 nm , or 365 nm UV light resulted from electrode discharge. When multi-layer phosphors of blue , green and red colors are coated on a UV light emitting diode , a broad wavelength, comparable to that of the glow lamp, is obtained. Thus, superior color stability is attained and color temperature and color rendering index can be freely controlled to some extent. However, it has not been commercially adopted as yet because of insufficient brightness .
[12] The first multi - chip type white light emitting diode introduced was to use three combined chips of red, green and blue colors. But, this had problems of no uniformity in operation voltage of each chip , change in color coordinates caused by different output of each chip depending on ambient temperature, need for additional driving circuit, etc . Accordingly, it was thought necessary to control brightness of each light emitting diode through circuit design in order to obtain various colors than to employ a white light emitting diode . The color coordinate system is based on the color matching functions defined by the Commission Internationale de PEclairage (CIE) in 1931. It is now widely adopted in industries as color display standard since it enables expression of colors based on color mixing . Occasionally, the white color is defined more rigorously than defined by the CIE system. For example, the SAE (Society of Automotive Engineers ) Standard J578 strictly defines the white color used in automobiles .
[13] Recently, a BCW (binary complementary) light emitting diode was developed, which is based on two light emitting diodes offering complementary colors . White light can be obtained by mixing orange and blue-green at a proportion of 4:1. As the performance index of the InGaAlP light emitting diode, which can emit light in the range of from orange to red, exceeds 100 lm/W, the luminous efficiency of the BCW white light emitting diode is comparable to that of fluorescent light . However, it is not adequate to be used as backlight of displays such as a monitor, in which color rendering is important .
[14] The present inventors made intensive efforts to improve luminous efficiency of the white light emitting diode manufactured from a single chip . In doing so, they found out that a white light emitting diode prepared by coating a phosphor mixture comprising phosphors of red, green and blue colors, which emits purple light in the wavelength range of 380 to 410 nm, and illuminating purple light in the wavelength range of 380 to 410 nm has superior color rendering index (CRI) and easily controllable color temperature because of the three phosphors emitting light at 460 nm, 520 nm and 580 nm, respectively . Also, they realized that the white light emitting diode has significantly improved luminous intensity and offers superior color vividness because it emits light in the broad range of from 380 to 700 nm.
[15] Therefore , an objective of the present invention is to provide a white light emitting diode which offers significantly improved luminous intensity and color vividness using specific tri-color phosphors and purple light in the specific wavelength range .
[16]
Disclosure
[17]
[18] The present invention relates to a white light emitting diode prepared by coating red, green and blue phosphors on a UV light emitting diode chip and illuminating light, wherein the phosphors comprise:
[19] (1) 10 to 30 wt% of a silicate- or sulfide-based red phosphor or a mixture thereof ;
[20] (2) 30 to 50 wt% of an alkaline earth metal silicate- or alkaline earth metal gallium sulfide-based green phosphor or a mixture thereof ; and
[21] (3) 30 to 50 wt% of an alkaline earth metal silicate- , alkaline earth metal aluminate- or halophosphate-based blue phosphor or a mixture thereof; and
[22] purple light in the wavelength range of 380 to 410 nm is illuminated to the phosphor mixture .
[23] Hereunder is given a more detailed description of the present invention .
[24] The present invention relates to a white light emitting diode using a single chip and tri-color phosphors, which is prepared by coating a mixture of red, green and blue phosphors which emits purple light in the wavelength range of 380 to 410 nm and illuminating purple light in said w wavelength range .
[25] In general, a white light emitting diode is prepared by using a blue light emitting chip with a yellow phosphor or by coating a mixture of red, green and blue phosphors on a UV light emitting chip . The present invention uses the latter technique and is characterized by selecting phosphors emitting light in specific wavelength range and mixing them with a specific proportion in order to improve luminance and color vividness . Conventionally, phosphors emitting light at 185 nm , 254 nm and 365 nm were mixed for use in the fluorescent lamp. In contrast , the present invention is for use in the UV LED. In the present invention, phosphors emitting light in the wavelength range of 380 to 410 nm are selected and mixed at a specific proportion to offer improved luminous intensity and superior color vividness . Such prepared white light emitting diode has a high efficiency of 10 mW or better. [26] Hereunder is given a more detailed description of the white light emitting diode of the present invention .
[27] As seen in the package type of Fig. 1 and the tower type of Fig. 2 , a phosphor mixture is coated directly or indirectly on a UV light emitting diode chip comprising a packaging frame or a lead frame . The packaging frame may be a printed circuit board (PCB) frame , a ceramic frame , a silicon frame or a metal frame .
[28] This technique is one commonly employed in the art and is not particularly limited in the present invention .
[29] The present invention relates to the use of a mixture of red, green and blue phosphors, which can emit light in the wavelength range of 380 to 410 nm , at a specific mixing rate .
[30] The phosphors are the ones commonly used in the art and are not particularly limited in the present invention , as long as emission of light in the afore-mentioned wavelength range is possible. Preferably, a silicate-based and sulfide-based red phosphor having a broad bandwidth and a center wavelength of 580 nm, for example, Si SiO :Eu, SrS :Eu or CaS :Eu, is used. For a green phosphor, one having a broad bandwidth and a center wavelength of 520 nm, that is, alkaline earth metal silicate , alkaline earth metal gallium sulfide or a mixture thereof is preferably used. For examp Vle, Sr 1 SiO 4 :Eu, Ba 2 Mg toSi 2 O 7 :Eu, Ba 2 SiO 4 :Eu, Sr 2 SiO 4 :Eu, CaGa 2 S4 :Eu, SrGa 2 S4
:Eu or BaGa S :Eu may be used. And , for a blue phosphor, one having a broad bandwidth and a center wavelength of 460 nm, that is, alkaline earth metal silicate , alkaline earth metal aluminate , halophosphate or a mixture thereof are preferably used. For example, Ca MgSi O :Eu, Ba MgSi O :Eu, Sr MgSi O :Eu, BaMgAl O :Eu, Sr (PO ) Cl:Eu, Sr (PO ) Cl:Eu or Mg (PO ) Cl:Eu may be used. The above phosphors
4 3 5 4 3 5 4 3 have been prepared by the present inventors and they are shown effective .
[31] In the phosphor mixture, each of the red , green and blue phosphor is comprised in the amount of 10 to 30 wt% , 30 to 50 wt% and 30 to 50 wt%, respectively . If the content of the red phosphor is below 10 wt%, a white color with a strong blue-green tone is obtained while if it exceeds 50 wt%, a white color with a strong red tone is obtained. If the content of the green phosphor is below 30 wt%, white color is not obtained while if it exceeds 50 wt%, a white color with a strong green tone is obtained . Further, if the content of the blue phosphor is below 30 wt%, a white color with a strong green-red tone is obtained while if it exceeds 50 wt%, a white color with a strong blue tone is obtained . The afore-mentioned mixing rate is an important factor because luminance efficiency , color temperature and CRI are determined by the mixing rate of the red , green , and blue phosphors .
[32] After coating the tri-color phosphors , purple light in the wavelength range of 380 to 410 nm is illuminated to obtain a white light emitting diode . In general, an epoxy resin is added during the coating . The weight proportion of the tri-color phosphors and the epoxy resin is an important factor that determines luminance efficiency and color temperature . Preferably, the epoxy resin is added so that the weight proportion of the phosphor mixture becomes 20 to 50 wt% . If the proportion of the phosphor mixture is below 20 wt%, the peak resulting from the UV chip becomes too strong. In contrast, a proportion of the phosphor mixture exceeding 50 wt% is inefficient .
[33] The resultant white light emitting diode has improved light emitting intensity, superior white color and high luminance efficiency of 10 mW or higher, preferably 10 to 30 mW, which is significantly better than the conventional ones.
[34]
Description Of Drawings
[35]
[36] Fig. 1 illustrates a package type white light emitting diode .
[37] Fig. 2 illustrates a tower type light emitting diode .
[38] Fig. 3 shows the emission spectra of the red, green and blue phosphors used in the present invention, when they are excited by light with a wavelength of 405 nm.
[39] Fig. 4 shows the emission spectra of the white light emitting diodes prepared in
Examples 1 to 3, with different mixing ratio of red, green and blue phosphor .
[40] Fig. 5 shows the emission spectra of the white light emitting diode prepared in
Example 1 using tri-color phosphors (red : green : blue = 1 : 2 : 2 , based on weight) and epoxy resin .
[41] Fig. 6 shows the color coordinate of the white light emitting diode prepared in
Example 1 using tri-color phosphors (red : green : blue = 1 : 2 : 2) and epoxy resin .
[42] Fig. 7 shows the emission spectra of the white light emitting diode prepared in
Example 2 using tri-color phosphors (red : green : blue = 1.5 : 1 : 1.5) and epoxy resin
[43] Fig. 8 shows the color coordinate of the white light emitting diode prepared in
Example 2 using tri-color phosphors (red : green : blue = 1.5 : 1 : 1.5) and epoxy resin
[44] Fig. 9 shows the emission spectra of the white light emitting diode prepared in
Example 3 using tri-color phosphors (red : green : blue = 1.5 : 1 : 2.5) and epoxy resin
[45] Fig. 1 0 shows the color coordinate of the white light emitting diode prepared in
Example 3 using tri-color phosphors (red : green : blue = 1.5 : 1 : 2.5) and epoxy resin
[46] Fig. 1 1 shows the emission spectra of the white light emitting diode prepared in
Comparative Example 1 using tri-color phosphors (red : green : blue = 4 : 3 : 3) and epoxy resin . [47]
Best Mode
[48] [49] Practical and preferred embodiments of the present invention are illustrated as shown in the following examples. However, it will be appreciated that those skilled in the art, in consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention .
[50] [51] Example 1 [52] Package type white light emitting diode and tower type white light emitting diode illustrated in Fig. 1 and Fig. 2, respectively, were prepared . The white light emitting diode comprised an electrode and an LED chip (1) bonded and fixed by a silver (Ag) paste (2). The LED chip was electrically connected to the electrode by a gold (Au) wire (4) . The LED chip was held in a hole cup , which had been formed by hardening treatment of the mixture of epoxy resin (5) and tri-color phosphors (3) . Subsequently, purple light in the wavelength range of 380 to 410 nm was illuminated . Then, resin molding was performed to obtain the white light emitting diode . In Fig. 2, the hardening treatment was performed in a reflector .
[53] [54] Examples 2 to 8 [55] A white light emitting diode was prepared in the same manner as in Example 1 with the composition and content given in Table 1 below.
[56] Luminance intensity of the red, green and blue phosphors used in the present invention is shown in Fig. 3. Fig. 4 shows the luminous intensity of the white light emitting diodes prepared in Examples 1 to 3. Table 1
Figure imgf000007_0001
[58] Examples 9 to 11 [59] A white light emitting diode was prepared using the tri-color phosphors of Example 1 to 3 and epoxy resin, with the mixing rate given in Table 2 below.
[60] Luminous intensity and color coordinate of the resultant white light emitting diode are shown in Figs. 5 to 10. Table 2
Tri-color Epoxy resin
Mixing rate (wt%) phosphors (Daejoo Fine Chemical)
0.164 : 1
Example 9 Example 1 Hardener : resin = 1 1
0.334 : 1
0.135 : 1
Example 10 Example 2 Hardener : resin = 1 1 0.308 : 1
0.428 : 1
0.128 : 1
0.159 : 1
Example 11 Example 3 Hardener : resin = 1 1
0.278 : 1
0.338 : 1
[61] As seen in Figs. 5 , 7 and 9, luminous intensity improved as thee content of the tricolor phosphors increased . [62] And , as seen in Figs. 6 , 8 and 10, the white LED prepared by mixing red, green and blue phosphors showed a black body radiation pattern .
[63] [64] Comparative Example 1 [65] A light emitting diode was prepared in the same manner as in Example 1, with a mixing rate of red, green and blue phosphors of 40 : 30 : 30 by weight. As seen in Fig. 1 1 , a white color with a strong red tone was obtained when the content of the red phosphor was high.
[66] Comparative Example 1 was for the case where the content of each of the phosphors falls outside the range defined in the present invention. It was confirmed that the tri-color phosphors have to be mixed at a specific proportion to obtain white LED and that white colors of all region can be attained by varying the mixing rate of the tri-color phosphors .
[67] Industrial Applicability
[68]
[69] As apparent from the above description , the present invention provides a white light emitting diode, which offers improved light emitting intensity , superior white color and high luminance efficiency of greater than 10 mW, by using red, green and blue phosphors emitting light in a specific wavelength range with a specific mixing rate .
[70] While the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the present invention as set forth in the appended claims.
[71]

Claims

Claims [1] A white light emitting diode prepared by coating red, green and blue phosphors on a UV light emitting diode chip and illuminating light, wherein said phosphors comprise:
(1) 10 to 30 wt% of a silicate- or sulfide-based red phosphor or a mixture thereof
(2) 30 to 50 wt% of an alkaline earth metal silicate- or alkaline earth metal gallium sulfide-based green phosphor or a mixture thereof ; and
(3) 30 to 50 wt% of an alkaline earth metal silicate- , alkaline earth metal aluminate- or halophosphate-based blue phosphor or a mixture thereof; and purple light in the wavelength range of 380 to 410 nm is illuminated to the phosphor mixture .
[2] The white light emitting diode as set forth in Claim 1, wherein said red phosphor is selected from Si SiO :Eu, SrS :Eu and CaS :Eu.
3 5
[3] The white light emitting diode as set forth in Claim 1, wherein said green phosphor is selected from Sr 2 SiO4 :Eu, Ba2 MgSi2 O7 :Eu, Ba2 SiO4 :Eu, Sr2 SiO4 :Eu,
CaGa 2 S 4 :Eu, SrGa 2 S 4 :Eu and BaGa 2 S 4 :Eu.
[4] The white light emitting diode as set forth in Claim 1, wherein said blue phosphor is selected from Ca MgSi O :Eu, Ba MgSi O :Eu, Sr MgSi O :Eu, BaMgAl O :Eu, Sr (PO ) Cl:Eu, Sr (PO ) Cl:Eu and Mg (PO ) Cl:Eu.
° 10 17 5 4 3 5 4 3 °5 4 3
[5] The white light emitting diode as set forth in Claim 1, which has a luminance efficiency ranging from 10 to 30 mW.
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