JP2006179884A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device having high efficiency, low environmental load and high color rendering property. <P>SOLUTION: The light emitting device has a first light emitting body 2 and a second emitting body 1 absorbing light from the first light emitting body 2 and emitting light. The second light emitting body 1 comprises group III-V substances. A chrominance coordinate value of a luminescent color of the light emitting device exists in a region surrounded by five points of (X, Y)=(0.18, 0.30), (0.22, 0.50), (0.40, 0.40), (0.45, 0.30) and (0.22, 0.20). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device.

  As a light-emitting device used for applications such as lighting and display with high luminous efficiency, a solid-state light-emitting element such as a light-emitting diode (LED) or a laser diode (LD) is used as the first light-emitting body, and the configuration of the second light-emitting body Light emitting devices using phosphors as components are known, and various devices have been proposed.

For example, as a light emitting device with high brightness, low power consumption, long life and low environmental load, as a phosphor of a light emitting device comprising a primary light source and a phosphor that absorbs light from the primary light source and emits secondary light, III It is known to use a -V group semiconductor microcrystal whose volume is smaller than a specific value (see Patent Document 1).
Further, in this patent document, it is possible to obtain white fluorescence by laminating a phosphor made of a nanocrystal of a III-V semiconductor with a red phosphor, a green phosphor and a blue phosphor. It is described that a white illumination device can be obtained by exciting with GaN-based light emitting element light.

JP 2004-83653 A

  However, in a light emitting device using a group III-V semiconductor of the long periodic table as the second light emitter, a light emission characteristic exhibiting high color rendering is realized when an object is irradiated with light emitted from the light emitting device. It wasn't. In Patent Document 1, it is said that white light is obtained using an LED as a primary light source and an InN nanocrystal having a specific volume as a secondary light source as a phosphor. However, the degree of white is unknown, and the phosphor Since the details of the production are unknown, it is considered that sufficient color rendering is not achieved.

  As a result of intensive studies, the present inventors have conventionally used a phosphor that has been heated by microwave irradiation at the time of synthesis as a phosphor to be used for the second phosphor. It has been found that no color rendering property is exhibited, and the present invention has been achieved.

  That is, the gist of the present invention is that a light-emitting device having a first light emitter and a second light emitter that absorbs light from the first light emitter and emits light, the second light emitter is III-. The chromaticity coordinate value of the luminescent color of the light emitting device containing the group V material is (X, Y) = (0.18, 0.30), (0.22, 0.50), (0.40, 0.40), (0.45, 0.30), and (0.22, 0.20) exist in a region surrounded by five points.

  According to the present invention, it is possible to provide a light emitting device having high color rendering properties with high efficiency and low environmental load.

<First luminous body>
Examples of the first light emitter include solid light emitting elements such as light emitting diodes (LEDs) and laser diodes (LDs), and LEDs and LDs are preferable from the viewpoint of low power consumption, and LD is particularly preferable.
When an LED or LD is used as the first light emitter, an LED using a GaN-based compound semiconductor in the light-emitting layer (hereinafter sometimes referred to as “GaN-based LED”) or LD (hereinafter referred to as “GaN-based LD”). The emission output and the external quantum efficiency are larger than those of other LEDs and LDs having the same emission wavelength, for example, LEDs using SiC, etc. Since a light emitting device with high power and high luminance can be obtained, the light emitting layer of the first light emitter is preferably made of a GaN compound semiconductor. For example, for a current load of 20 mA, a GaN-based LED usually has a light emission intensity 100 times or more that of an LED using SiC.

Here, the GaN-based compound semiconductor refers to a compound semiconductor having Ga atoms and N atoms as main constituent components.
The light emitting layer in the GaN-based LED or GaN-based LD contains Al _x Ga _1-x N, GaN, or In _x Ga _1-x N because the light emission intensity of the LED or LD increases. In particular, it is preferable that In _x Ga _1-x N is contained. Here, x is an arbitrary real number satisfying 0 <x <1 (hereinafter, x represents the same meaning). Of the GaN-based LDs, a multiple quantum well structure having an In _x Ga _1-x N layer and a GaN layer is preferable in terms of high emission intensity. On the other hand, in a GaN-based LED, it is preferable that the light emitting layer is doped with Zn or Si because it is easy to adjust light emission characteristics such as light emission intensity and wavelength dispersion of the light emission spectrum.

A GaN-based LED usually has a light emitting layer, a p layer, an n layer, an electrode, and a substrate as basic components. Here, since the light emission efficiency can be increased, the light emitting layer is sandwiched between n-type and p-type Al _x Ga _1-x N layers, GaN layers, In _x Ga _1-x N layers, or the like. Those having a heterostructure are preferred. For the same reason, it is more preferable that the light emitting layer has a quantum well structure.
The wavelength of the first illuminant that gives the maximum value of the emission intensity in the emission spectrum is preferably 350 nm or more, more preferably 380 nm or more, most preferably 400 nm or more, while 500 nm or less is preferable. More preferably, it is 450 nm or less, and most preferably 430 nm or less. In particular, as described later, it is preferably within the above-mentioned wavelength from the viewpoint that the color coordinate value of the emission color of the light-emitting device of the present invention falls within a specific range of the present invention. When there are two or more wavelengths giving the maximum value of the emission intensity, or when the emission intensity is the same in a certain wavelength range, it is preferable that at least one of the wavelengths or the wavelength range is within the above range. . This is because, in the LED and LD, which are the first light emitters having good light emission efficiency, the light emission efficiency can be further increased by selecting the wavelength that gives the maximum value of the light emission intensity.

<Second luminous body>
The second light emitter is a light emitter that emits light by absorbing light from the first light emitter, and includes a phosphor that absorbs light from the first light emitter and generates photoluminescence. Usually, the wavelength peak of light emission from the first light emitter is different from the wavelength peak of light emission of the second light emitter, and the relationship is not particularly limited, but the peak wavelength of the second light emitter is the first light emitter. It is preferable that the wavelength is longer than the peak wavelength.

  In the present invention, a group III-V substance is used as the phosphor contained in the second light emitter.

  The group III-V substance is substantially at least one group III element in the long periodic table such as B, Al, Ga, In, Tl, and a long period such as N, P, As, Sb, Bi. It is a substance consisting of at least one group V element in the table. Here, “substantially consisting of at least one group III element and at least one group V element” means a substance mainly composed of group III element and group V element. Including the case of containing a trace amount component.

Examples of group III-V materials include BN-based materials, AlN-based materials, GaN-based materials, GaP-based materials, InP-based materials, InGaN-based materials, and InGaP-based materials.
Here, the meanings of “InGaP-based material”, “BN-based material” and the like are as follows. That is, in the case of an “InGaP-based material”, for example, it is “a material that contains at least three elements of In, Ga, and P and has a single and unique crystal structure”. The crystal structure is a structure having a periodic atomic arrangement, such as a sphalerite structure (Zinc Blend type structure) or a wurtzite structure. However, a part of at least one of In, Ga, and P may be substituted with another element.

When substituted, the In site or Ga site is preferably substituted with a group III element, and the P site is substituted with a group V element. In addition, since charge compensation is performed and the crystal structure is easily maintained, it is preferable that the element to be replaced and the element to be replaced have the same ion valence.
In addition, the group III-V material may have other impurity elements penetrating between sites as long as the characteristics are not impaired, and may have crystal defects and dislocations. Examples of the element that may be contained in the phosphor according to the present invention include one or more elements such as H, F, O, and Al.

  The phosphor contained in the second light emitter is more preferably an InP-based material or an InGaP-based material because light emission with good color rendering properties can be obtained when combined with the first light-emitting material. Substances are preferred.

ただし、上記式（II）において、ｙ及びｚは、０＜ｙ≦１，０≦ｚ＜１を満たす任意の実数である。さらに好ましくは０＜ｙ＜１，０＜ｚ＜１を満たす任意の実数である。ｙ，ｚが上記の範囲にあることは、この超微粒子が、ＩｎＰの結晶格子中のＩｎの一部がＧａに置換されているか、あるいは、ＧａＰの結晶格子中のＧａの一部がＩｎに置換されていることを特徴とする三元系半導体からなるという技術的な意義を有する。ここで、発光の量子収率の観点から、ｙの範囲は好ましくは０．９≦ｙ≦１、ｚに関しては、ｚ＝０である。さらに好ましくは、０．９≦ｙ＜１、ｚに関しては、ｚ＝０である。
ただし、Ｉｎ、Ｇａ及びＰの少なくとも何れかのサイトの一部が他の元素によって置換されて含有されていても良い。又、ＩｎＧａＰ系物質の結晶構造としては、尖亜鉛鉱構造（Zinc Blend型構造）であることが好ましい。 The InP-based material preferably has an InP composition ratio. However, a part of at least one of In and P may be substituted with other elements.
On the other hand, the InGaP-based substance preferably has a composition ratio of the following formula (II).

However, in the above formula (II), y and z are arbitrary real numbers satisfying 0 <y ≦ 1, 0 ≦ z <1. More preferably, it is an arbitrary real number satisfying 0 <y <1, 0 <z <1. The fact that y and z are in the above range means that in the ultrafine particles, a part of In in the InP crystal lattice is substituted with Ga, or a part of Ga in the GaP crystal lattice is replaced with In. It has the technical significance of being a ternary semiconductor characterized by being substituted. Here, from the viewpoint of the quantum yield of light emission, the range of y is preferably 0.9 ≦ y ≦ 1, and with respect to z, z = 0. More preferably, for 0.9 ≦ y <1, z, z = 0.
However, a part of at least one of In, Ga, and P may be substituted with other elements. Further, the crystal structure of the InGaP-based material is preferably a sphalerite structure (Zinc Blend type structure).

  The phosphor may be core-shell structured particles. The core-shell structure is a particle having an inner core (core) and an outer shell (shell) structure. By taking the core-shell structure, the physical and chemical properties of the particles can be preferably changed.

In this case, the phosphor may be contained on either the inner core or outer shell side of the core-shell structure, but it is preferable that the phosphor is contained in the inner core of the core-shell structure.
The inner core and outer shell of the core-shell structure may be composed of a plurality of types of substances. There may be a plurality of outer shells. As the material used for the outer shell, one or more of III-V compound semiconductor, II-VI compound semiconductor, or metal oxide is preferable. Among them, InP, BN, BAs, GaN, ZnO, ZnS, One or more of ZnSe, CdS, CdSe, MgS, MgSe, and SiO ₂ are more preferable.
Furthermore, two or more types of phosphors (that is, two or more types of III-V group substances) may be used, and the phosphors may be used for both the inner core and the outer shell.
However, the outer shell material must be different from the inner shell material.

  Further, the phosphor included in the second light emitter may be composed of one kind of phosphor or may be composed of a plurality of kinds of phosphors. Further, the phosphor particles may have crystal defects and dislocations as long as the characteristics are not impaired, may have a positional composition ratio shift, and contain impurities within a range that does not impair the characteristics. Also good. Moreover, any of a single crystal and a polycrystal may be sufficient.

The absorption spectrum of the III-V group substance contained in the second luminous body of the present invention preferably has a small intensity change in the wavelength range of 400 nm to 450 nm.
Furthermore, it is preferable to use a phosphor satisfying the following formula (I) as the phosphor contained in the second light emitter.

(In the above formula (I), P (λ) represents the intensity of the absorption spectrum at the wavelength λ, P (λ) _max represents the maximum value of P (λ) at 400 nm ≦ λ ≦ 450 nm, and P (λ) _min represents the minimum value of P (λ) at 400 nm ≦ λ ≦ 450 nm.)
P (λ) _min / P (λ) _max is preferably 0.5 or more, more preferably 0.7 or more, and most preferably 0.8 or more.

This is due to the following reason.
The main intensity distribution of the emission spectrum of the first luminous body having good luminous efficiency is usually 400 nm ≦ λ ≦ 450 nm. Here, the main intensity distribution of 400 nm ≦ λ ≦ 450 nm means that 70% or more, preferably 80% or more of the intensity area exists in the wavelength range of 400 nm and 450 nm. However, the emission spectrum of the first illuminant may vary with time, and is usually a change of about ± 10 nm. That is, the emission spectrum of the first illuminant temporally varies about ± 10 nm in the wavelength (λ) axis direction. In addition to the change over time, there are fluctuations in the emission spectrum due to individual differences in the first light emitters, and this point needs to be taken into account when actually mass-producing light-emitting devices. The fluctuation of the emission spectrum due to this individual difference is usually about ± 10 nm. Therefore, it is preferable that the absorption spectrum of the second light emitter has a small change when 400 nm ≦ λ ≦ 450 nm. In general, the emission spectrum of the first light emitter has a mountainous distribution around the wavelength giving the peak. Therefore, when the change is large, fluctuations in the wavelength direction of the emission spectrum due to changes over time and / or individual differences. As a result, the absorption efficiency of the second light emitter changes greatly. Therefore, the range of change in intensity at 400 nm ≦ λ ≦ 450 nm of the absorption spectrum of the phosphor contained in the second light emitter is 30% to 100%, that is, the minimum value is 30% to 100% of the maximum value. If not, effective light absorption from the first light emitter cannot be performed.

In order for the above P (λ) _min / P (λ) _max to satisfy the formula (I),
(1) A substance having a long wavelength at the end of the absorption spectrum (the maximum wavelength at which the absorption intensity is zero on the absorption spectrum) is used as the phosphor.
(2) reduce impurities contained in the phosphor;
(3) reducing composition shift in the phosphor (for example, In _0.3 Ga _0.2 P _0.5 in one region, In _0.1 Ga _0.7 P _0.2 in other regions, etc.)
(4) reducing the ratio of defect regions in the phosphor crystal (for example, regions that are displaced from the site where atoms should be present),
It is sufficient to take a method such as.

  Among them, it is preferable to use a substance having a long absorption spectrum end as the phosphor as in the method (1). Although the specific absorption spectrum edge is arbitrary as long as the effect of the present invention is not significantly impaired, it is preferably 400 nm or more, more preferably 450 nm or more, particularly 500 nm or more, and most preferably 600 nm or more. Moreover, it is 2 micrometers or less normally. In order to select a substance having an absorption spectrum edge having a long wavelength, it is preferable to use a material having as small an energy gap as the phosphor. For this purpose, for example, a group III-V substance may be used for the phosphor. Among them, it is preferable to use an InGaP-based material.

  When the above method (2) is performed, the impurity concentration is preferably 30% by weight or less, more preferably 10% by weight or less, and most preferably 1% by weight or less with respect to the phosphor. Moreover, it is 0.0001 weight% or more normally.

  Further, when the above method (3) is performed, the composition deviation in the phosphor is preferably 50% or less, preferably 10% or less, from the average value of the composition fraction of each atom. Is more preferable. Moreover, it is 0.1% or more normally. In addition, the average value of the composition fraction of each atom can be obtained by inductively coupled plasma optical emission spectrometry (IPC). Specifically, the deviation from the average value of the composition fraction of each atom is calculated by calculating the composition fraction of each atom with an electron beam microanalyzer (EPMA) for an arbitrary 10Å × 10Å plane 100 region. It can be obtained by calculating the ratio of deviation from the average value of the composition fraction.

Moreover, when performing said method (4), it is preferable that the ratio of the defect area | region within a fluorescent substance crystal is 50% or less with respect to a theoretical position, and it is more preferable that it is 30% or less. . Moreover, it is 0.1% or more normally. The ratio of the defect region can be obtained by measuring the site position of the atom by an X-ray absorption fine structure analysis method (XAFS) on an arbitrary 100Å × 100Å plane and calculating the ratio to the theoretical position.
However, the above methods (1) to (4) may be carried out by arbitrarily combining two or more.

On the other hand, in the group III-V group phosphor contained in the second light emitter, the intensity P (λ) of the absorption spectrum in the wavelength range exceeding 450 nm is preferably smaller than the above P (λ) _max . This is due to the following reason.
In the range of λ> 450 nm, when P (λ) has a value larger than the maximum value of 400 nm ≦ λ ≦ 450 nm (that is, P (λ) _max ), generally, the spectral weight in the range of 400 nm ≦ λ ≦ 450 nm is The amount of the cut is provided as a long wavelength side, that is, a spectrum of λ> 450 nm. FIG. 1 shows an example of an absorption spectrum in such a case. In such a case, a light emission spectrum of a light emitting diode that is preferably used (the light emission spectrum of the first light emitter when an LED having a light emission wavelength of 450 nm is used as the first light emitter in FIG. 2) is distributed. This means that the absorption spectrum intensity of the second light emitter in the region of 400 nm ≦ λ ≦ 450 nm is decreased. As a result, the light from the light emitting diode cannot be effectively absorbed.

Furthermore, it is more preferable that the intensity in the range where the wavelength λ exceeds 450 nm is smaller than any intensity in the range where the wavelength λ is 400 nm or more and 450 nm or less. That is, it is preferable that the intensity P (λ) of the absorption spectrum in the wavelength range exceeding 450 nm is smaller than the P (λ) _min . When there is a large absorption spectrum intensity in the range where the wavelength λ exceeds 450 nm, an absorption spectrum having a sufficient intensity is generally obtained in the region where the emission spectrum of the first luminous body with good luminous efficiency is distributed, 400 nm ≦ λ ≦ 450 nm. Because you can't.

  The average particle size of the phosphor of the present invention is usually 0.5 nm or more, preferably 1 nm or more, more preferably 2 nm or more, and usually 10 μm or less, preferably 1 μm or less, more preferably 100 nm or less, more preferably 20 nm or less. Among these, it is 12 nm or less, most preferably 10 nm or less. The average particle size is the number average particle size. If the average particle size is too small, non-radiation deactivation occurs due to a decrease in crystallinity and the like, and the internal quantum efficiency may be lowered, resulting in a decrease in luminous efficiency. On the other hand, if the average particle size is too large, the effect of increasing the state density due to the quantum effect is reduced, the absorption efficiency is not sufficiently obtained, and the light emission efficiency is lowered.

The average particle size and standard deviation are defined by morphological analysis of transmission electron microscope (TEM) images.
For this reason, when a light-emitting device is manufactured in combination with the first light emitter, it is possible to obtain excellent light emission stability over time.

  The phosphor according to the present invention can narrow the emission spectrum by narrowing the particle size distribution. Here, the narrowing of the emission spectrum can be referred to as an emission spectrum having a narrow half-value width. The particle size distribution of the phosphor according to the present invention is preferably 10% or less, more preferably 5% or less as a standard deviation. Although there is no particular lower limit of the particle size distribution, the standard deviation is usually 0.001% or more. If the particle size distribution of the phosphor exceeds this standard deviation range, the object of narrowing the emission spectrum cannot be sufficiently achieved, resulting in the disadvantage of poor color purity.

Here, the standard deviation (σ) is the sum of squares of the number average particle diameter (d) subtracted from the particle diameter (di) of each phosphor measured from the observation photograph of TEM. The half width is the value of the peak wavelength from the value of the wavelength longer than the peak taking the value of absorbance 0.5 when the absorbance at the peak wavelength is normalized to 1. Is defined as a value that is doubled.
The number average particle diameter and the standard deviation can be obtained by actual measurement from a TEM observation photograph, but may be obtained by using an image analysis processing device or the like.

  Moreover, the phosphor according to the present invention can control the peak wavelength of the emission spectrum of the secondary light by controlling the particle size. For example, when extracting red light with an emission wavelength of 590 nm to 650 nm, the individual particle size d of the phosphor may be within the range of 4 nm <d <6 nm, and green light with an emission wavelength of 520 nm to 570 nm may be obtained. In the case of taking out, it is sufficient that the individual particle diameter d of the phosphor is within a range of 1.5 nm <d <2.8 nm.

  Further, the quantum yield of the phosphor of the present invention is usually 40% or more, preferably 45% or more, and more preferably 50% or more. If the lower limit is exceeded, the intensity of the excitation light source must be increased in order to obtain practically sufficient luminance, which may increase the power consumption of the light emitting device. The upper limit is not limited, but is theoretically 100% or less.

  In order to improve the quantum yield of the phosphor, techniques such as etching with a fluorine compound, core-shell phosphor phosphor synthesis of a phosphor using a microwave, and coating of the phosphor surface with an organic substance are used. Among these, an etching method using a fluorine compound is generally used in order to improve the quantum yield of light emission of the ultrafine particle phosphor made of a III-V group substance.

Etching is performed by adding a solution containing fluoride ions to a solution containing a phosphor and irradiating with ultraviolet / visible light while stirring (reference: Talapin, DV, et al., J. Phys Chem. B 2002, 106, pp. 12659-12663). This process is also called photoetching. After adding a solution containing fluoride ions to a solution containing phosphor, the quantum yield of the phosphor increases with time by irradiating with light while stirring. Generally, the more dilute fluoride ion solution is used, the longer it takes to increase the quantum yield. On the other hand, when the concentration of the fluoride ion solution is increased, the quantum yield increases in a shorter time. Incidentally, where it is used, as the compound containing fluoride _{ions, HF, NH 4 F, (} CH 3) 4 NF, (C 4 H 9) 4 NF, and the like are exemplified.

The quantum yields described herein are relative quantum yields and are measured as follows. First, an ethanol solution of rhodamine 6G is prepared as a reference solution. At this time, the absorbance at a wavelength of 440 nm is set to about 0.1. A fluorescence spectrum obtained by exciting the solution at a wavelength of 440 nm is measured. Next, a phosphor solution as a sample is prepared. At this time, the absorbance of the phosphor solution at a wavelength of 440 nm is set to be the same as the absorbance of the reference solution at a wavelength of 440 nm. The fluorescence spectrum of the phosphor solution is measured under the same conditions as the reference. Then, the relative quantum yield φ _em is calculated using the following formula (III).

In the above formula (III), I represents the integrated area of the emission peak of the sample (phosphor solution), I ′ represents the integrated area of the emission peak of the reference solution, and A represents the excitation wavelength of the sample (phosphor solution) ( 440 nm), A ′ represents the absorbance at the excitation wavelength (440 nm) of the reference solution, n represents the refractive index of the solvent of the sample (phosphor solution), and n ′ represents the refractive index of the solvent of the reference solution. Represents a rate. Φ ′ _em is the quantum efficiency (0.95) of rhodamine 6G.

  Moreover, the phosphor according to the present invention may be accompanied by an organic compound on the surface thereof. The phrase “the phosphor is accompanied by an organic compound on its surface” means a state in which the organic compound is bonded and held on the phosphor surface. There is no limitation on the bonding mode between the organic compound and the phosphor on the surface of the phosphor. For example, relatively strong chemical bonds such as coordination bonds, covalent bonds, and ionic bonds, or van der Waals forces, hydrogen bonds, hydrophobic-hydrophobic Examples include relatively weak reversible attractive interactions such as interactions and molecular chain entanglement effects. The organic compound accompanying the surface may be one kind or plural kinds. Although there is no restriction | limiting regarding the organic substance, As a specific example, trialkyl phosphines, trialkyl phosphine oxides, alkane sulfonic acids, alkane phosphonic acids, alkyl amines, dialkyl sulfoxides, dialkyl ethers, fatty acids, alkenes, Examples include alkynes.

  When the phosphor is accompanied by an organic compound on its surface, there is an effect of improving dispersibility in an organic solvent or a binder resin.

<Synthesis method>
For the production of the phosphor particles of the present invention, it is preferable to use a heated reaction vessel. The heated reaction container can keep the inside of the container at a temperature higher than room temperature, and can suppress the exchange of substances with the outside in the case of a closed system. Usually, a plurality of types of source materials (phosphor precursors) and a solvent are placed in the reaction vessel, but in some cases, only the source materials may be used. As the raw material, a known raw material compound (compound of a metal element constituting the phosphor) used for the synthesis of the desired phosphor is used at a ratio of a desired composition.

The mixing of raw materials and / or solvents or raw material compounds is usually from −30 ° C. to 100 ° C., but is preferably at the same temperature (room temperature) as the outside environment because temperature control is easy. Generally, in the same case as the outside environment, the temperature is 0 ° C. or higher and 40 ° C. or lower. The temperature of the heated reaction vessel is measured by a thermometer, pyrometer, thermocouple or the like and used for control.
The manufacturing process of the phosphor in the heating reaction vessel usually comprises at least one of (1) heating, (2) heat retention, and (3) cooling. Here, the heat retention means to keep the temperature in the heating reaction container constant, and is usually higher than the external environment temperature (room temperature).

Heating in the heating reaction vessel is performed by a heat source such as an oil bath, a mantle heater, a flame burner, or microwave irradiation. In particular, by adopting heating by microwave irradiation, the emission intensity of the phosphor particles satisfying the above formula (I) tends to be adjusted within the range of the above formula (I). However, in addition to microwave irradiation, one or more methods such as an oil bath, a mantle heater, and a burner may be used in combination as appropriate.
The peak wavelength of the irradiated microwave is preferably 1 GHz or more, more preferably 2 GHz or more, and most preferably 2.4 GHz or more. Moreover, Preferably it is 10 GHz or less, More preferably, it is 3 GHz or less, Most preferably, it is 2.5 GHz or less. The wavelength spectrum of the microwave is preferably steep, and it is particularly preferable to use a single mode microwave. In addition, if the power intensity of the microwave is excessively high, it may be difficult to control the phosphor synthesis reaction, and if it is low, the synthesis reaction may not proceed sufficiently. Therefore, it is desirable that the microwave power intensity is about 100 W to 30 kW. . It is preferable that the reaction atmosphere gas be continuously flown into the reaction vessel during microwave irradiation. The heating temperature is usually 50 ° C. or higher, preferably 100 ° C. or higher, more preferably 200 ° C. or higher, and usually 1000 ° C. or lower, preferably 500 ° C. or lower, more preferably 300 ° C. or lower.

  In the synthesis of such a phosphor, the value of the particle size distribution of the obtained phosphor can be controlled by appropriately adjusting the heating rate and cooling rate of the reaction vessel in the phosphor synthesis. For example, in the heating reaction vessel, heating is performed steeply and cooling is performed steeply. Specifically, conditions where the heating rate is 20 ° C./min or more and the cooling rate is 50 ° C./min or more are preferable.

In addition, the particle size control of the obtained phosphor can be controlled by, for example, the concentration of the phosphor precursor in the reaction solution. If larger particles are to be produced, a multiple injection method (multi injection) is used. Use it. In the multiple synthesis method, after the phosphor is synthesized in the reaction container according to the phosphor synthesis method, a precursor of the phosphor is further added to the reaction container, and the phosphor is synthesized according to the phosphor manufacturing process. And repeat as necessary. For example, ultrafine particles having a particle size larger than that of the phosphor obtained by the first synthesis reaction can be produced by the second synthesis reaction. By using this multiple synthesis method, the particle size can be controlled.
The value of the particle size dispersion (standard deviation of the particle size distribution) of the phosphor of the present invention can be controlled by appropriately adjusting the microwave frequency.

<Structure of light emitter>
In the present invention, it is preferable to use a surface-emitting type illuminant, particularly a surface-emitting GaN-based LD, as the first illuminant. This is because the luminous efficiency of the entire light emitting device is increased. Here, the surface-emitting light emitter is a light emitter that emits strong light in the surface direction of the film. In surface-emitting GaN-based LDs, by controlling the crystal growth of the light-emitting layer, etc., and appropriately arranging the reflective layer, etc., it is realized that light emission in the surface direction is stronger than the edge direction of the light-emitting layer. ing. In the case of using a surface-emitting type light emitter, a light emission cross-sectional area per unit light emission amount can be increased compared to a type that emits light from the edge of the light emitting layer. As a result, when the phosphor constituting the second luminous body is irradiated with the light, the irradiation area per unit light quantity can be increased, that is, the irradiation efficiency can be improved, and a stronger light emission from the phosphor is obtained. It becomes possible. In the case of using a surface-emitting type illuminant as the first illuminant, the second illuminant is preferably formed into a film. Since the cross-sectional area of the light from the surface-emitting type light emitter is sufficiently large, when the second light emitter is formed into a film shape in the direction of the cross section, the phosphor having an irradiation cross-sectional area from the first light emitter to the phosphor The amount per unit amount can be increased, and stronger light emission from the phosphor can be obtained.

  Further, when a surface-emitting type is used as the first light emitter and a film-like one is used as the second light emitter, the second light emitter directly in the form of a film on the light-emitting surface of the first light emitter. It is preferable to have a shape in which is contacted. Here, the contact means a state in which the first light emitter and the second light emitter are in contact with each other without using a gas such as air or various liquids. As a result, it is possible to avoid that the light from the first light emitter is reflected by the film surface of the second light emitter and goes out (light loss), and the light emission efficiency of the entire device can be increased. It becomes.

Hereinafter, an example of a light emitting device of the present invention will be described based on the drawings.
FIG. 3 is a schematic perspective view showing the positional relationship between the first light emitter and the second light emitter in one embodiment of the light emitting device of the present invention. In FIG. 3, 1 represents a second light emitter, 2 represents a first light emitter (for example, a surface-emitting GaN-based LED), and 3 represents a substrate. It is preferable that the LED and the second light emitter are in contact with each other because the loss of light flux is reduced. In order to realize a state in which they are in contact with each other, the LED and the second light emitter are made separately, and the surfaces are brought into contact with each other by an adhesive or other means, or on the light emitting surface of the LED. The second light emitter may be formed or molded.

Here, it is preferable to use a phosphor in which phosphor powder is dispersed in a resin as the second luminous body. The light from the first light emitter and the light from the second light emitter are usually directed in various directions. However, by using the second light emitter dispersed in the resin, the light is removed from the resin. This is because a part of the light is reflected when the light exits, so that the directions of light can be aligned. Further, since the total irradiation area of the light from the first light emitter to the second light emitter is increased, the light emission intensity from the second light emitter can be increased. As the resin, an epoxy resin, a polyvinyl resin, a polyethylene resin, a polypropylene resin, a polyester resin, or the like may be used. In particular, it is preferable to use an epoxy resin. This is because the dispersibility of the phosphor powder is good.
When the phosphor powder is dispersed in the resin, the weight ratio of the phosphor powder and the resin as a whole is usually 1% or more, preferably 10% or more, more preferably 20% or more, more preferably 30% or more. . Moreover, it is 95% or less normally, Preferably it is 90% or less, More preferably, it is 80% or less. This is because if the weight ratio of the phosphor is too large, the light emission efficiency may be reduced due to aggregation of the phosphor powder, and if it is too small, the light emission efficiency may be reduced due to light absorption or scattering by the resin.

FIG. 4 shows a schematic cross-sectional view of another example of the light emitting device of the present invention.
The shape of the light emitting device in FIG. 4 is a cannonball shape. The first light emitter (7) is covered with the phosphor-containing resin portion (8) in the upper cup (5) of the mount lead. A second light emitter is formed on the first light emitter. The second light emitter is formed by mixing and dispersing a phosphor in a binder such as an epoxy resin or an acrylic resin and pouring the mixture into a cup.

On the other hand, in FIG. 4, the first light emitter (7) and the mount lead (5), and the first light emitter (7) and the inner lead (6) are connected by a conductive wire (9), respectively. These are entirely covered and protected by a mold member (10) made of epoxy resin or the like.
An example of a surface emitting illumination device (98) incorporating this light emitting element is shown in FIG. A large number of light emitting devices (91) are provided on the bottom surface of a rectangular holding case (910) whose inner surface is light opaque such as a white smooth surface. A power supply and a circuit (not shown) for driving the light emitting element are provided outside the light emitting device. A diffuser plate (99) such as a milky white acrylic plate is fixed to a portion corresponding to the lid portion of the holding case for the purpose of uniform light emission.
The surface-emitting illumination device is driven to apply a voltage to the first light emitter of the light-emitting element to cause the first light emitter to emit light, and a part of the emitted light contains a phosphor as the second light emitter. The phosphor in the resin part absorbs. The phosphor absorbs part of the light emitted from the first light emitter, and emits light having a spectrum different from the absorbed light. On the other hand, light emission with high color rendering properties is obtained by mixing with blue light or the like that has not been absorbed by the phosphor, and this light is transmitted through the diffusion plate and emitted upward from the drawing, and is uniform within the diffusion plate surface of the holding case. Illumination light with a high brightness can be obtained.

<Chromaticity coordinate value of emission color of light emitting device>
In the light emitting device of the present invention, it is preferable to mix the light from the first light emitter and the light from the second light emitter to make the light extracted from the light emitting device white. This is because when the extracted light is white light, the color rendering property of the object irradiated by the light emitting device is enhanced. This is particularly important when the light-emitting device is used as a component of a lighting device.

In particular, the chromaticity coordinate values of the luminescent color of the light emitting device of the present invention are (X, Y) = (0.18, 0.30), (0.22, 0.50), (0.40, 0. 40), (0.45, 0.30), and (0.22, 0.20) are present in the region surrounded by the five points (including the boundary line).
Here, the chromaticity coordinate value is the International Lighting Commission (Commission Internationale de l'Eclair
It is an XY coordinate value based on a spectrum tristimulus pure value defined in 1931 by age (CIE)). Since the chromaticity coordinate value of the light emission color of the light emitting device has the above range, the object irradiated by the light emission has a spectrum close to the object color in which the reflected light is illuminated by sunlight (daylight), Therefore, a light emitting device having high color rendering properties can be realized.

The chromaticity coordinate values of the emission color of the light emitting device are (X, Y) = (0.28, 0.26), (0.25, 0.35), (0.28, 0.40), (0 .38, 0.38) and (0.38, 0.31) are more preferably present in the region surrounded by the five points (including the boundary line).
In order to make the luminescent color of the light emitting device have the desired chromaticity coordinate value, use a group III-V substance for the phosphor contained in the second light emitter, and in particular, use a group III-V substance. It is preferable to use the III-V group material obtained by the process including the heating by microwave irradiation of the III-V group material raw material, in particular, using a heating reaction vessel.

It is also possible to have the desired chromaticity coordinate values by mixing a plurality of types of phosphors corresponding to III-V materials. Here, the plurality of types of phosphors refer to different types due to different material compositions or different particle diameters even with the same composition. Here, the meaning of “plurality” includes that a parameter indicating a difference (composition fraction (such as _x in In _x Ga _1-x ), particle size, etc.) has a distribution (has dispersion).

The light emitting device of the present invention may include a light emitter other than the first light emitter and the second light emitter. For example, a third light emitter that absorbs light from the second light emitter and emits visible light is used to form a light-emitting device that mixes the first light emitter, the second light emitter, and the third light emitter. May be. Alternatively, a third light emitter that absorbs light from the first and / or second light emitters and emits visible light is used, and a color mixture of the first light emitter, the second light emitter, and the third light emitter is used. A light emitting device may be configured.
In the light emitting device of the present invention, a color filter can also be used.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by the following examples.
Hereinafter, a synthesis example of an InGaP-based material will be shown as a phosphor. Unless otherwise specified below, commercially available chemicals were used as raw materials without purification. Moreover, the following apparatus was used for experiment.
(Experimental device)
Synthesizer using microwave:
DISCOVER system made by CEM Corporation
Constant power and pulse power sources:
Milestone Corporation's MILESTONE ETHOS system
Plasma emission spectrometer:
JOBIN YVON inductively coupled plasma-emission spectrophotometer "JY38S"
UV / V absorption spectrum measuring apparatus:
CARY 50BIO WIKN UV Spectrometer
Photoluminescence spectrum measuring device:
CARY ECLIPSE Fluorescence Spectrometer
X-ray diffractometer:
SCINTAG X2 powder diffractometer
Transmission electron microscope (TEM):
JEOL 2010 Transmission Electron Microscope
The DISCOVER system is equipped with a small 10 ml reaction vessel with a high-pressure aluminum cap with a Teflon (registered trademark) diaphragm. All glassware was dried before use before use. In addition, chemicals used as raw materials were handled with the air blocked.

Example 1
Indium acetate (In (OAc)), gallium acetylacetonate complex (Ga (acac)) and palmitic acid were dissolved in a hexadecene solvent kept at 100 ° C. to prepare a 15.6 mM cation solution. Here, the number of cations is defined as the sum of the number of Ga ions and the number of In ions. At this time, the mixing amount was adjusted to satisfy the following (1) and (2).

(1) Ga atom number / (In atom number + Ga atom number) = 0.095
(2) Palmitic acid molecule number / (Ga atom number + In atom number) = 3
The solution was degassed for 1 hour under vacuum while maintaining this temperature and purged with Ar gas three times.
Next, an 86.1 mM P (SiMe ₃ ) ₃ solution (Me represents a methyl group) was prepared using hexadecene as a solvent. In this manner, indium gallium palmitate (CH ₃ (CH ₂ ) ₁₄ COO (In, Ga)) and P (SiMe ₃ ) ₃ used as precursor materials for the reaction were synthesized. For the above synthesis method, Nano Lett. 2, 107 (2002) can be referred to.

Next, hexadecene solution of indium gallium palmitate, P (SiMe ₃ ) _{3 so} that the total number of cations (the sum of the number of indium ions and the number of gallium ions) and the number of anions (phosphorus ions) are 2: 1. Mixed in. The total volume of the solution was 5 mL. Also, the entire solution was kept at 50 ° C.
Next, the solution was irradiated with electromagnetic waves (frequency: 2.45 GHz) at a power intensity of 300 W in the reaction vessel until the solution reached 280 ° C. After reaching 280 ° C., the power intensity of electromagnetic wave irradiation was lowered to 280 W, and the power intensity was maintained as it was. The solution temperature and electromagnetic wave power intensity were kept constant for 15 minutes, and then rapidly cooled. Thereby, particles of an InGaP-based material having a particle diameter of 2.3 nm were obtained. The produced crystal of InGaP-based material particles had a zinc-blende structure, and the particle size dispersion (standard deviation of the particle size distribution) was 5%. Further, the composition of the particles of the InGaP-based substance was analyzed by plasma emission spectroscopic analysis and confirmed to be (In _0.95 Ga _0.05 ) P.

When the absorption spectrum of the InGaP particles was measured with a UV / V absorption spectrum measuring apparatus, the results shown in FIG. 6 (data of “solvent: hexadecene”) were obtained. Λ giving P (λ) _max was 400 nm, and λ giving P (λ) _min was 450 nm. Moreover, when the emission spectrum was measured with the photoluminescence spectrum measuring apparatus, the result (data of "solvent: hexadecene") of FIG. 7 was obtained. The emission spectrum was a normal distribution type, its peak wavelength was 560 nm, and the half width of the emission spectrum was 40 nm. As described above, particles having P (λ) _min / P (λ) _max = 0.50 were obtained.

  When a light-emitting device is configured by combining the obtained InGaP-based material (III-V group material) particles with an inorganic LED having an emission peak at 400 nm, chromaticity coordinate values (X, Y) = (0.33, 0. A light emitting device having an emission spectrum of 34) could be obtained.

  1 mL of the synthesized InGaP particles was weighed and transferred to a glass vial, and 4 mL of toluene was added thereto and mixed. Here, 20 mL of acetone was added to cause precipitation, and this precipitate was collected by centrifugation. The obtained precipitate was dissolved again in 5 mL of toluene. To this solution, 20 μL of a 10% by weight HF / water / butanol solution prepared by diluting a 48% by weight HF aqueous solution with butanol was added and stirred, and the wavelength was 365 nm using a handy small UV irradiation device. Of UV light for 1 hour. After completion of the reaction, 20 mL of methanol was added to this solution to cause precipitation, and this precipitate was collected by centrifugation. Toluene was added to the resulting precipitate to prepare a solution for measuring the quantum yield at a predetermined concentration. The quantum yield was measured and found to be 70%.

<Stability of emission spectrum>
The same synthetic experiment was repeated 5 times, and each emission spectrum was measured. As a result, the variation in the peak wavelength of the emission spectrum was in the range of 560 nm ± 3 nm, and an experimental result with good reproducibility was obtained.

(Example 2)
InGaP-based material particles having a particle size of 4.3 nm were synthesized in the same manner as in Example 1 except that the solvent for mixing indium gallium palmitate and P (SiMe ₃ ) ₃ was changed from hexadecene to octadecene.
The crystals of this InGaP-based material had a zinc-blende structure, and the particle size dispersion (standard deviation of the particle size distribution) was 5%.
Further, the composition of the InGaP-based material was analyzed by plasma emission spectroscopy, and confirmed to be (In _0.94 Ga _0.06 ) P.

When the absorption spectrum of this particle was measured with a UV / V absorption spectrum measuring apparatus, the result of FIG. 6 (data of “solvent: octadecene”) was obtained. Λ giving P (λ) _max was 400 nm, and λ giving P (λ) _min was 450 nm. When the emission spectrum was measured with a photoluminescence spectrum measuring apparatus, the result of FIG. 7 (data of “solvent: octadecene”) was obtained. The emission spectrum was a normal distribution type, its peak wavelength was 600 nm, and the half width of the emission spectrum was 50 nm. Here, the excitation wavelength at the time of emission spectrum measurement was 400 nm. As described above, particles of P (λ) _min / P (λ) _max = 0.71 were obtained.

When a light-emitting device is configured by combining the obtained InGaP-based material (III-V group material) particles with an inorganic LED having a light emission peak at 400 nm, the chromaticity coordinate value (X, Y) = (0.40, 0. A light emitting device having an emission spectrum of 39) could be obtained.
Further, the synthesized InGaP particles were etched by the same method as in Example 1. The quantum yield was measured and found to be 50%.

<Stability of emission spectrum>
The same synthetic experiment was repeated 5 times, and each emission spectrum was measured. As a result, the peak wavelength of the emission spectrum was in the range of 600 nm ± 4 nm, and an experimental result with good reproducibility was obtained.

For example, a GaN-based LD is used as a first light emitter, and a light emitter obtained by mixing phosphor particles of an InGaP-based material synthesized according to the above example as a second light emitter in a resin. In the light emitting device, since the absorption spectrum of the phosphor contained in the second light emitter is 1 ≧ P (λ) _min / P (λ) _max ≧ 0.3, the time of the emission wavelength of the first light emitter It is possible to suppress a change in the light emission characteristics from the second light emitter also against the target fluctuation. In addition, even when there is an individual difference in the emission spectrum of the first light emitter, a change in the light emission characteristics from the second light emitter can be suppressed. Therefore, it is possible to provide a light emitting device that improves at least one of temporal light emission stability and stability of light emission characteristics between individuals.

  The light emitting device of the present invention can be used for, for example, a light source for indoor lighting, a backlight for an image display device such as a color liquid crystal display, a traffic light, and the like.

It is an example of the absorption spectrum of the second light emitter having a large intensity at λ> 450 nm. It is an example of the emission spectrum of the 1st light emitter with good luminous efficiency. It is a typical perspective view which shows the positional relationship of a 1st light emitter and a 2nd light emitter. It is typical sectional drawing which shows one Example of the light-emitting device of this invention. It is typical sectional drawing which shows one Example of the surface emitting device of this invention. It is an example of the absorption spectrum of the 2nd light-emitting body used for the light-emitting device of this invention. It is an example of the emission spectrum of the 2nd light-emitting body used for the light-emitting device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 2nd light-emitting body 2 Surface emitting type GaN-type LED
DESCRIPTION OF SYMBOLS 3 Board | substrate 4 Light-emitting device 5 Mount lead 6 Inner lead 7 1st light-emitting body 8 Resin part containing the 2nd light-emitting body of this invention 9 Conductive wire 10 Mold member

Claims (5)

  In a light-emitting device including a first light emitter and a second light emitter that absorbs light from the first light emitter and emits light, the second light emitter includes a III-V group substance, The chromaticity coordinate values of the emission color of the light emitting device are (X, Y) = (0.18, 0.30), (0.22, 0.50), (0.40, 0.40), (0 .45, 0.30) and (0.22, 0.20), the light emitting device is present in a region surrounded by five points. The light-emitting device according to claim 1, wherein an absorption spectrum of the III-V group material satisfies the following formula (I).

(In the above formula (I), P (λ) represents the intensity of the absorption spectrum at the wavelength λ, P (λ) _max represents the maximum value of P (λ) at 400 nm ≦ λ ≦ 450 nm, and P (λ) _min represents the minimum value of P (λ) at 400 nm ≦ λ ≦ 450 nm.)   3. The light emitting device according to claim 1, wherein the number average particle diameter of the III-V group substance is 100 nm or less and the quantum yield is 40% or more. The light emitting device according to any one of claims 1 to 3, wherein the group III-V substance includes a compound that satisfies a composition ratio represented by the following formula (II).

(However, y and z are arbitrary real numbers satisfying 0 <y ≦ 1, 0 ≦ z <1)   5. The group III-V substance contained in the second light emitter is obtained by a process including heating by microwave irradiation. 6. Light emitting device.

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