JP2004115621A - Fluoride fluorescent material, its manufacturing method and light-emitting device using the material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent material which efficiently absorbs ultraviolet rays, and a light-emitting device which efficiently radiates blue light emission. <P>SOLUTION: A blue light-emitting material is a fluoride fluorescent material 11 which is represented by the formula: AE<SB>1-x</SB>Eu<SB>x</SB>F<SB>2</SB>(wherein AE is Ca or Sr; and x is 0.3-0.05 mol%) and is composed of a single crystal. The light-emitting device enables efficient blue light emission by providing the fluoride fluorescent material 11 adjoining a nitride semiconductor layer 13 which comes to a light-emitting layer. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fluoride fluorescent material and a light emitting device using the same, and more particularly, to a fluoride fluorescent material that efficiently absorbs ultraviolet light and a light emitting device that obtains good blue light using the same.
[0002]
[Prior art]
Generally, as a white light emitting diode, a phosphor (YAG: Ce phosphor) in which Ce is doped in a base lattice of a YAG-based oxide known by a composition formula of (Y, Gd) ₃ (Al, Ga) ₅ O _12. ) Is dispersed in a sealing resin surrounding a blue light emitting diode (blue LED) using a nitride semiconductor (for example, Patent Nos. 2990928, 2998696, and 2927279). And a non-particulate phosphor layer formed on a blue LED (for example, see Patent Document 1). These are used for a display backlight, an LED display, and the like. I have.
[0003]
This non-particulate phosphor layer is as shown in the sectional view of the LED chip shown in FIG. That is, a nitride-based compound semiconductor layer 13a serving as a light emitting layer is provided on a substrate 12a of sapphire or the like, and the semiconductor layer 13a excluding the electrodes 15a and 15b on the semiconductor layer 13a is covered with a non-particulate material. The fluorescent layer 11a is formed.
[0004]
The fluorescent layer 11a is a non-particulate inorganic phosphor, and the non-particulate property means that the phosphor itself is formed not in powder but in a layered form, and Y, Gd, Ce, Sm, It is made of an Al, La-based phosphor, and uses a sintered body thereof or a thin film formed by sputtering. When the light emitted from the LED chip and the light emitted from the non-particulate fluorescent layer 11a have a complementary color relationship or the like, white light is emitted by mixing the respective lights.
[0005]
Further, there is a structure in which a light emitting portion of a blue LED using a group III nitride semiconductor (general formula: AlGaInN) has an oxynitride glass phosphor layer to which an emission center is added (for example, see Patent Document 2). .). The light-emitting element, a oxynitride glass, in particular those with Ca-Al-Si-O- N -based oxynitride glass doped with Eu ₂ ⁺ ions as a luminescent center.
[0006]
This light emitting device is shown in the cross-sectional view of FIG. That is, an epitaxial wafer for a blue LED in which an epitaxial layer 13b made of a group III nitride semiconductor is formed on a sapphire substrate 12b using a metal organic chemical vapor deposition (MOCVD) method is prepared. to those where the _Eu ^{2 +} phosphor layer 11b formed of the Ca-Al-Si-O- N -based oxynitride glass added was laminated with a high-frequency sputtering method.
[0007]
The epitaxial wafer for white LED is formed into chips in the same process as that for manufacturing a normal blue LED, and the epitaxial wafer is bonded to the leads 16 and 17 with the epitaxial wafer surface facing down on a pedestal serving also as the electrodes 15a and 15b. Then, it is covered with the mold part 18. In this light emitting device, blue light emitted from the active layer of the group III nitride semiconductor by current injection is emitted to the outside from the back surface of the sapphire substrate 12b, and part of the light is excited to convert the phosphor to yellow to red light. High power white light is emitted in combination with blue light emission.
[0008]
[Patent Document 1]
JP-A-11-46015 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-33521
[Problems to be solved by the invention]
However, in these conventional techniques, the color reproducibility of the light emitting element is poor and the Ra value is low, so that the problem of color reproducibility is caused. Therefore, a three-wavelength type combining an ultraviolet light emitting diode and blue, green, and red phosphors is used. Of white LEDs have been developed. However, there is no phosphor that efficiently absorbs light having an emission wavelength of about 370 nm and emits visible light having a wavelength of 400 nm or more efficiently, and has not yet been commercialized. Further, the phosphor for LED conventionally used has poor crystallinity because it is a powder, and has been a cause of deterioration of life.
[0010]
An object of the present invention is to solve these problems and to provide a fluorescent material that emits blue light efficiently and is expected to have a long life, a method for manufacturing the same, and a light emitting device using the same.
[0011]
[Means for Solving the Problems]
Configuration of fluoride fluorescent material of the present invention, the blue luminescent _{material, AE1-x Eux F 2 (} AE = Ca or Sr, x = 0.3~0.05mol%,) the Eu represented by the activated It is characterized by being made of fluoride.
[0012]
The structure of the method for manufacturing a fluoride fluorescent material according to the present invention is characterized in that the blue light-emitting material is manufactured as a single crystal in a reducing gas or hydrogen fluoride gas atmosphere.
[0013]
Structure of a light-emitting element of the present invention, the excitation wavelength 370nm before and after the light-emitting diodes, fluorescent material which absorbs efficiently ultraviolet (composition formula _AE1-xEuxF 2: AE = Ca or Sr, x = 0.3~0.005mol% ) To efficiently emit blue light. In addition, it is characterized by emitting white or any intermediate color by combining green and red light emitting phosphors,
Structure of another light-emitting device of the present invention, the blue luminescent _{material, AE1-x Eux F 2 (} AE = Ca or Sr, x = 0.3~0.05mol%,) single crystal of fluoride which is represented by A plate layer is provided adjacent to the nitride semiconductor layer of the light emitting layer formed on the substrate, and emits blue light through the single crystal plate layer.
[0014]
In the present invention, a single crystal of fluoride may be provided on the transparent conductive film formed on the nitride semiconductor layer.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a light emitting device illustrating one embodiment of the present invention. In the present embodiment, a light emitting element including a nitride semiconductor layer 13 formed on a transparent sapphire substrate 12 and a part of light emitted from the light emitting element has a longer wavelength than light emitted from the light emitting element. A light-emitting single-crystal plate layer 11 for converting light. This light-emitting element has at least a fluoride light-emitting single crystal doped with europium (Eu) on a transparent substrate (conductive film) 14 and on a surface opposite to the substrate 12 on which the nitride semiconductor layer 13 is laminated. It is characterized by having a layer 11. The light emitting element is connected to the leads 16 and 17 from the electrodes 15a and 15b, and emits light when power is supplied from the leads 16 and 17.
[0016]
As the present embodiment, as a blue emitting phosphor, Ca0.99, Eu0.01, using _{F 2.} The light emitting phosphor is manufactured by a Bridgman method in a reducing gas or hydrogen fluoride gas atmosphere. In addition, as a method for forming a single crystal, there is a pulling method or the like. As a starting material of the light emitting phosphor, a predetermined amount of a CaF ₂ reagent having a purity of 99.99% or more and a EuF ₃ reagent having a purity of 99.9% or more are prepared, dried, and manufactured at a high temperature of about 1100 ° C.
[0017]
In the embodiment of the present invention, a light emitting element including a nitride semiconductor layer 13 formed on a transparent sapphire substrate 12 and a part of light emitted from the light emitting element having a longer wavelength than light emitted from the light emitting element. In a light-emitting element having a light-emitting single-crystal plate layer 11 for converting light, at least on a transparent substrate 14 and a surface opposite to the surface of the substrate 12 on which the nitride semiconductor layer 13 is laminated, europium is deposited. It is characterized by having a fluoride light emitting single crystal layer 12 added.
[0018]
As the fluoride light emitting single crystal plate 12, there is one obtained by adding europium (Eu) to CaF ₂ , SrF ₂ , (Ca, Sr) F ₂ , LiCaF ₃ , LiSrF ₃ , Li (CaSr) F _{3 and the} like. This Eu functions as a luminescence center and is replaced by replacing Ca or Sr in the base material.
[0019]
The fluorescent material of the present embodiment emits blue light, and when emitting light as white light, a green phosphor and / or a red phosphor are mixed in a single crystal plate, or a green phosphor and And / or a red phosphor layer can be formed. Here, the green phosphor includes ZnS: Cu, BaMgAl ₁₀ O ₁₇ : Eu, Mn, and the red phosphor includes Y ₂ O ₂ S: Eu, YVO ₄ : Eu (for example, see US6084250).
[0020]
FIG. 1 shows a specific example of the structure, and FIG. 2 shows the optical characteristics of the developed fluorescent material CaF ₂ : Eu (Ca0.99Eu0.01F ₂ ), and SrF ₂ : Eu (Sr0. 99Eu0.01F ₂ ) is shown in the characteristic diagram of FIG. From these figures, it can be seen that each of the fluorescent materials efficiently emits light at a wavelength of around 370 nm.
[0021]
According to the embodiment of the present invention, a fluoride matrix fluorescent material that efficiently absorbs ultraviolet light from an ultraviolet LED and emits blue light is obtained, and is combined with a green phosphor and a red phosphor to produce a white light for illumination or the like. It can also be used as a light source. Further, blue light-emitting material according to the present invention, a fluoride represented by _AE1-xEuxF 2 (AE = Ca or / or Sr, x = 0.3~0.05mol%), and characterized in that it consists of a single crystal I do.
[0022]
【The invention's effect】
As described above, according to the fluorescent material of the present invention, it is possible to efficiently absorb ultraviolet light having a wavelength of about 370 nm and emit deep blue light having a wavelength of 420 to 440 nm, thereby obtaining a light source having good color purity. There is an effect that can be. In addition, conventional phosphors for LEDs have poor crystallinity due to being powder and cause a deterioration in life, but in the structure of the present invention, since the phosphor material can be made into a single crystal, There is an effect that deterioration can be suppressed as compared with powder and a long-life light emitting LED can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a light-emitting element illustrating one embodiment of the present invention.
FIG. 2 is a graph illustrating light emission characteristics of the light emitting device of FIG.
FIG. 3 is a graph illustrating light emission characteristics of another light emitting element in FIG.
FIG. 4 is a cross-sectional view illustrating a chip structure of a conventional light emitting element.
FIG. 5 is a sectional view showing the structure of another conventional light emitting element.
[Explanation of symbols]
Reference Signs List 11 Fluoride single crystal plate layer 11a Non-particulate fluorescent layer 11b Phosphor layer 12, 12a, 12b of oxynitride glass Sapphire substrate 13 Nitride semiconductor layer 13a Group III nitride semiconductor layer 13b Nitride compound semiconductor layer 14 Transparent conductive film 15a, b Electrode 16, 17 Lead 18 Mold part

Claims (6)

Fluoride blue luminescent material, characterized in that it consists _{AE1-x Eux F 2 (AE} = Ca or Sr, x = 0.3~0.05mol%,) fluorides activated by Eu represented by Fluorescent material. A method for producing a fluoride fluorescent material, wherein the blue light-emitting material according to claim 1 is produced as a single crystal in a reducing gas or hydrogen fluoride gas atmosphere. A light emitting device comprising a fluorescent material according to claim 1 as a fluoride fluorescent material. A light-emitting element comprising a phosphor that emits blue light as a fluorescent phosphor material according to claim 1 combined with a green phosphor and a red phosphor to form a white light source for illumination or the like. Emitting a blue light emitting _{material, AE1-x Eux F 2 (} AE = Ca or Sr, x = 0.3~0.05mol%,) the single crystal plate layer of fluoride represented by, formed on a substrate A light-emitting element which is provided adjacent to a nitride semiconductor layer and emits blue light through the single crystal plate layer. 6. The light emitting device according to claim 5, wherein the fluoride single crystal plate layer is provided on a transparent conductive film formed on the nitride semiconductor layer.

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