JP2011014697A - White light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white light-emitting device that has excellent uniformity of a spatial color hue and excellent luminous efficiency.SOLUTION: The white light-emitting device is configured as follows. A blue phosphor, a green phosphor, and an orange phosphor are excited by using radiation light of a semiconductor light-emitting element having a main luminescence-peak wavelength of 400-440 nm. The white light mainly composed of the radiation light of the phosphors is made as output light of the white light-emitting device. The white light is configured such that a wavelength, in which a spectrum strength becomes maximum in a region on the long-wavelength side longer than 515 nm, is in a range of 535-600 nm while a spectrum strength in a range of a wavelength of 570-600 nm is equal to or more than a half of the maximum spectrum strength in the region on the long-wavelength side longer than 515 nm.

Description

  The present invention relates to a white light-emitting device configured by combining a semiconductor light-emitting element such as a light-emitting diode (LED) element and a phosphor that is a wavelength conversion material, and in particular, blue phosphor, green phosphor, and orange phosphor as phosphors. And a white light-emitting device that uses, as output light, white light composed mainly of photoluminescence light emitted from these phosphors.

Nitride system comprising an LED structure formed of a nitride semiconductor represented by the general formula Al _x In _y Ga _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1) LED elements are widely used as light emitting elements capable of generating short wavelength light ranging from ultraviolet to green. Among them, an InGaN-based LED element in which an active layer (in particular, a quantum well layer) is formed of InGaN (in the above general formula, x = 0, 0 <y <1) is known to have particularly high luminous efficiency.

  In addition, a white light emitting device (white LED) in which a nitride LED element and a phosphor are combined has been put into practical use. A typical example is a type of white light that generates white light by mixing blue light emitted from an InGaN-based blue LED element and yellow light obtained by converting the wavelength of the blue light with a Ce-activated YAG phosphor. This is a light emitting device (Patent Document 1). In the present specification, this type of white light emitting device is hereinafter referred to as a BY type.

Since the spectrum of the output light is concentrated in the wavelength range (near 555 nm) where the visibility is maximized, the BY type white light emitting device has [lm / W] (lumen per watt: total luminous flux per unit power). It is a light source having a very high luminous efficacy expressed using the unit, i.e., a light source that feels very bright visually.
However, the BY light-emitting device has a drawback of low spatial color uniformity. In short, the color tone of the emitted white light differs depending on the direction from which the light source is viewed. This phenomenon occurs because the radiation pattern is significantly different between the LED chip that is a blue light source and the phosphor powder that is a yellow light source (usually dispersed in a resin).

  In order to solve this problem in the BY type, a nitride-based LED element that emits near-ultraviolet light or violet light with low visibility is used as an excitation light source, and wavelength conversion of three primary colors of blue, green, and red is performed by a phosphor. There is also known a white light emitting device generated by the above (Patent Document 2). In the present specification, hereinafter, this type of white light emitting device is referred to as an RGB type.

International Publication No. WO98 / 05078 Pamphlet JP 2003-249694 A U.S. Pat. No. 3,576,756 US 2006/0169998

E.FRED SCHUBERT: LIGHT-EMITTING DIODES, CAMBRIDGE UNIVERSITY PRESS, 2003

Comparing the BY type and RGB type white light emitting devices, the RGB type is superior in spatial color uniformity, but the BY type is overwhelmingly advantageous in terms of luminous efficiency. This is a general recognition in the industry. This is because the light generated by the wavelength conversion by the phosphor is only yellow light in the BY light-emitting device, but is all three primary color lights in the RGB light-emitting device. In other words, the loss associated with wavelength conversion is greater in the RGB type than in the BY type. This loss includes Stokes shift.
Therefore, a white light-emitting device that has the advantages of both the BY type and the RGB type, that is, a white light-emitting device that is excellent in spatial color tone uniformity and also in light emission efficiency, is desired.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a white light emitting device which is excellent in spatial color tone uniformity and luminous efficiency.

It is true that the RGB type white light emitting device generates more colors by wavelength conversion than the BY type. On the other hand, it is also true that many phosphors that can be excited by light of near ultraviolet to blue wavelengths exhibit higher excitation efficiency on the shorter wavelength side than blue. Further, the above-mentioned drawbacks of the BY type white light emitting device can be alleviated by diffusing the radiated light of the semiconductor light emitting element using means such as a diffusing agent. A decrease in efficiency is inevitably accompanied.
Furthermore, the Stokes shift has a dominant effect on the efficiency of white light-emitting devices only when most of the other major factors that reduce the efficiency of the phosphor are removed. The external quantum efficiency of the phosphor does not reach 100%, and there is still much room for improvement in the light extraction efficiency at the light emitting device level.
Therefore, it is too early to conclude that the RGB type white light emitting device cannot compete with the BY type in terms of luminous efficiency.
The present invention has been completed as a result of researches based on such considerations.
In order to achieve the above object, the white light emitting device of the present invention adopts the following configuration.

A blue phosphor, a green phosphor and an orange phosphor are excited using the emitted light of a semiconductor light emitting device having a main emission peak wavelength in the range of 400 nm to 440 nm, and are composed mainly of the emitted light of these phosphors (A ) White light-emitting device that uses white light as output light.
(A) The wavelength having the maximum spectral intensity in the region on the longer wavelength side from 515 nm is in the range of 535 nm to 600 nm, and the spectral intensity at an arbitrary wavelength in the range of 570 nm to 600 nm is on the longer wavelength side than 515 nm. White light that is more than half of the maximum spectral intensity in the region.

  In the white light emitting device according to the present invention, the reason why the lower limit of 400 nm is provided for the main emission peak wavelength of the semiconductor light emitting element is to reduce the Stokes shift. Even if the excitation efficiency of the phosphor increases when the wavelength of the excitation light is shortened, the presence of the Stokes shift is commensurate with the increase in power consumption of the semiconductor light-emitting element that is inevitably associated with the shortening of the wavelength of the excitation light. However, there is a case where an increase in luminous efficiency cannot be expected. In order to make the Stokes shift smaller, the main light emission peak wavelength of the semiconductor light emitting device is preferably 410 nm or more, more preferably 420 nm or more.

  In particular, in the case of an InGaN-based light-emitting element, the half-width of the emission spectrum can be suppressed to 25 nm or less by adopting a quantum well structure in the active layer. Therefore, if the main emission peak wavelength is 410 nm or more, the emitted light The ultraviolet component having a wavelength of less than 400 nm contained in can be brought close to zero. By suppressing the generation amount of ultraviolet rays from the semiconductor light emitting element, it is possible to use a resin material having low resistance to ultraviolet degradation as a member of the white light emitting device.

  In the white light emitting device according to the present invention, the reason why the upper limit of 440 nm is set on the main emission peak wavelength of the semiconductor light emitting element is to reduce the blue component with high visibility contained in the emitted light of the semiconductor light emitting element. is there. Accordingly, the influence of the emitted light of the semiconductor light emitting element on the color tone of the output light of the light emitting device can be reduced, and consequently the spatial color tone uniformity of the light emitting device can be improved.

  As described above, by adopting a quantum well structure in the InGaN-based light emitting device, the half-value width of the emission spectrum can be suppressed to 25 nm or less. Therefore, when the main emission peak wavelength is 440 nm or less, it is included in the emitted light. The component having a wavelength of 460 nm or more can be brought close to zero. The photopic curve (CIE 1978) for photopic vision rises at a wavelength of 460 nm. Therefore, in the violet light having a wavelength of less than 460 nm and the blue light having a wavelength of 460 nm or more, the former is more in color tone of the output light of the light emitting device than the latter. The effect is much smaller.

  In the white light emitting device according to the present invention, the white light of the above (A) is composed mainly of blue light, green light and orange light emitted from the blue phosphor, green phosphor and orange phosphor, respectively. Is the output light. The color of light (blue, green, orange, white) here is a color defined according to the color assignment on the CIE chromaticity diagram. For this assignment, see FIG. 17.4 (1931 CIE chromaticity diagram with areas attributed to distinct colors (after Gage et al., 1977)). In the present specification, the name of the phosphor is determined based on the color of light emitted from the phosphor. For example, a phosphor that emits blue light is called a blue phosphor, a phosphor that emits green light is called a green phosphor, and a phosphor that emits orange light is called an orange phosphor.

  In order to reduce the loss associated with wavelength conversion, a blue phosphor, a green phosphor and an orange phosphor to be used are all capable of being excited by the emitted light of the semiconductor light emitting device. In the prior art, there has been proposed a white light emitting device that excites a blue phosphor with the emitted light of a semiconductor light emitting element and excites a yellow phosphor using only the emitted light of the blue phosphor. In the conventional method, double wavelength conversion loss occurs in the process of generating yellow light.

  Since the white light emitting device according to the present invention uses white light composed mainly of the radiated light of the phosphor as the output light, for the same reason as in the case of the conventional RGB type white light emitting device, it has a spatial color tone. High uniformity. Therefore, a configuration (such as a light diffusing agent) for diffusing the emitted light of the semiconductor light emitting element can be omitted or reduced. Adopting such a configuration is not preferable because it reduces the light extraction efficiency of the semiconductor light emitting device.

In the white light emitting device according to the present invention, with respect to white light composed mainly of radiated light of a blue phosphor, a green phosphor and an orange phosphor, a wavelength having a maximum spectral intensity in a region longer than 515 nm, The requirement is to be in the range of 535 nm to 600 nm. This requirement is intended to concentrate the combined spectrum of the green and orange phosphor radiation in (i) the wavelength range where the visibility is maximum or (ii) the yellow wavelength range. . Note that the wavelength of 515 nm is the lower limit wavelength of the green wavelength region (the wavelength region in which monochromatic light having a wavelength in the region exhibits green).

  According to the CIE visibility curve regarding photopic vision, when the visibility at a wavelength of 555 nm is 1, the visibility is 0.9 or more in the wavelength range of 535 nm to 575 nm. Therefore, the intensity of the combined spectrum of the emitted light of the green phosphor and the orange phosphor takes a maximum value within this wavelength range. This means that the energy input to the light-emitting device is visually transmitted through these two phosphors. It means focusing on the production of light that looks brightest on.

  On the other hand, when the intensity of the combined spectrum of the emitted light of the green phosphor and the orange phosphor takes a maximum value in the yellow wavelength region, the input energy to the light emitting device passes through these two phosphors and the blue phosphor. The most efficient conversion to RGB balanced white light. The perception of white color from yellow light and blue light, and the reason is that yellow light stimulates the M cone (green cone) and L cone (red cone) of the human retina, and the S cone. It is well known that blue light stimulates the body (blue cone). In addition, the yellow wavelength region here is a region having a wavelength of 570 nm to 600 nm. Monochromatic light having a wavelength in this region exhibits a yellow color.

  In the white light emitting device according to the present invention, the spectral intensity at an arbitrary wavelength within a range of 570 nm to 600 nm with respect to white light mainly composed of emitted light of a blue phosphor, a green phosphor and an orange phosphor, The requirement is that it is at least half of the maximum spectral intensity in the region longer than 515 nm. If the combined spectrum of the emitted light from the green and orange phosphors does not contain sufficient wavelength components in the yellow wavelength region, RGB balanced light is generated from the emitted light from these two phosphors and the blue phosphor. It is because it cannot be made to do. Therefore, in the white light, the spectral intensity at an arbitrary wavelength within the range of 570 nm to 600 nm is more preferably 60% or more, and more preferably 80% or more of the maximum spectral intensity in the region longer than 515 nm. Is more preferable.

  In a preferred embodiment of the white light-emitting device according to the present invention, the white phosphor is derived from the emitted light of the green phosphor on the spectrum curve of the white light composed mainly of the emitted light of the blue phosphor, the green phosphor and the orange phosphor. The separation of the peak from the peak of the orange phosphor and the peak derived from the emitted light of the orange phosphor is not observed. In order to obtain such a spectrum curve, first, for both the green phosphor and the orange phosphor, those having only one peak in the emission spectrum are selected. Then, the emission wavelengths of the green phosphor and the orange phosphor may be brought close to each other. That is, a green phosphor having a relatively long emission wavelength may be selected, and an orange phosphor having a relatively short emission wavelength may be selected. When such a spectral curve is obtained, the energy input to the light-emitting device is transmitted through the green phosphor and the orange phosphor more efficiently, and the light in the wavelength range or yellow wavelength range where the visibility is maximum. Will be concentrated on the generation of

  In a preferred embodiment of the white light emitting device according to the present invention, the spectrum curve of white light composed mainly of the emitted light of a blue phosphor, a green phosphor and an orange phosphor is on the upper side within a wavelength range of 535 nm to 600 nm. It is convex and the spectral intensity at an arbitrary wavelength longer than 650 nm is less than half of the spectral intensity at a wavelength of 600 nm. Furthermore, the spectral intensity on the longer wavelength side than 650 nm is more preferably less than 40% and particularly preferably less than 30% of the spectral intensity at a wavelength of 600 nm. These limitations on the spectral curve represent a state where the combined spectrum of the emitted light of the green phosphor and the orange phosphor is efficiently concentrated within the wavelength range of 535 nm to 600 nm.

By combining the white light emitting device according to the present invention with a Mn ⁴⁺ activated fluoride complex phosphor, which is a red phosphor, the color rendering properties can be improved without significantly reducing the light emission efficiency. The color gamut can be expanded or the color temperature can be lowered.
The Mn ⁴⁺ activated fluoride complex phosphor has a light emission peak wavelength in a relatively short wavelength (shorter wavelength side than 650 nm) in the red wavelength region, and the shape of the light emission peak is very sharp (Patent Literature). 3 and Patent Document 4). As can be seen from the characteristics on the emission spectrum, this phosphor does not convert the absorbed excitation light into light in a wavelength region with low visibility (region longer than 650 nm), so it is extremely high as a red phosphor. Indicates conversion efficiency.

A typical Mn ⁴⁺ -activated fluoro complex phosphor is of the hexafluoro complex salt type represented by the chemical formula M ₂ XF ₆ : Mn, but 5 to 7 metal atoms as a coordination center. Some include complex ions coordinated by fluorine ions. A preferred Mn ⁴⁺ activated fluorocomplex phosphor is K ₂ SiF ₆ : Mn based on potassium hexafluorosilicate. A material in which a part of Si (10 mol% or less) in K ₂ SiF ₆ : Mn is substituted with Al and a part of K (10 mol% or less) is substituted with Na can also be suitably used.

A point to be noted when using the Mn ⁴⁺ activated fluoride complex phosphor is that the excitation spectrum of this phosphor has a sharp dent in the vicinity of a wavelength of 400 nm (Patent Document 3). Therefore, in order to excite this phosphor with the emitted light of the semiconductor light emitting device, it is necessary to use a semiconductor light emitting device having a main emission peak wavelength of 420 nm or more, preferably 430 nm or more. However, even when a semiconductor light emitting device having a shorter emission peak wavelength is used, it is not preferable in terms of light emission efficiency, but it is Mn ⁴⁺ activated fluoride complex phosphor by blue light emitted by the blue phosphor. Can be excited.

In the embodiment using the Mn ⁴⁺ activated fluoride complex phosphor, in addition to the white light satisfying the above limitation (A), which is composed mainly of the emitted light of the blue phosphor, the green phosphor and the orange phosphor. The white light emitting device is configured such that the emitted light of the Mn ⁴⁺ activated fluoride complex phosphor is simultaneously emitted as output light. Since this white light and the emitted light of the Mn ⁴⁺ activated fluoride complex phosphor have completely different spectral curves, they can be distinguished on the synthetic spectrum of these lights.

  The white light emitting device according to the present invention is excellent in spatial color uniformity and luminous efficiency, and can be preferably used as a light source for an illumination device or a light source for a display device.

1 is a schematic cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention. It is a schematic cross section of an InGaN-based LED chip. It is an emission spectrum of the white LED produced in Experimental Example 1. It is an emission spectrum of white LED produced in the comparative experiment example. It is an emission spectrum of white LED produced in Experimental example 2.

Hereinafter, the present invention will be described in accordance with specific embodiments with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a white light emitting device according to an embodiment of the present invention. The white light emitting device 1 shown in this figure is an SMD (surface mounted) LED, and an InGaN-based LED chip 20 has an adhesive (not shown) on the bottom surface of a cavity (cup-shaped portion) provided in the package 10. It is fixed using.

  The package 10 includes an insulating substrate 11 formed of ceramic (alumina, AlN, etc.), white resin (transparent resin in which a white pigment is dispersed), etc., two package electrodes 12, and a metal or white material (ceramic or resin). It is comprised from the reflector 13 formed by. Although the insulating substrate 11 and the reflector 13 are shown as separate members in this figure, they can be formed integrally using the same material.

  The InGaN-based LED chip 20 includes a crystal substrate 21 made of sapphire, SiC, GaN, and the like, and a nitride semiconductor film 22 formed thereon, and positive and negative electrodes are formed on the surface of the nitride semiconductor film 22. Is formed. The positive electrode is composed of a transparent electrode 23a made of a transparent conductive oxide (TCO) and a metal bonding pad 23b formed on a part thereof. The negative electrode is also composed of a transparent electrode 24a made of TCO and a metal bonding pad 24b formed on a part thereof. A metallic reflective film 25 is formed on the lower surface of the crystal substrate 21.

Each of the positive electrode and the negative electrode of the InGaN-based LED chip 20 is connected to each of the two package electrodes 12 by a bonding wire 30 made of Au, Al, Cu or the like.
The InGaN-based LED chip 20 is embedded with a translucent coating 40. In the coating 40, a blue phosphor, a green phosphor, and an orange phosphor, which are powdered, are dispersed (the phosphor is not shown). These phosphors can be uniformly dispersed within the coating 40. A method for forming the coating 40 may be appropriately selected from known methods such as mold forming, potting forming, and dipping forming.

  In one embodiment, the coating 40 can be a multilayer structure with a phosphor containing layer and a non-containing layer. Alternatively, layers containing different phosphors, such as a layer containing a blue phosphor, a layer containing a green phosphor, a layer containing an orange phosphor, a layer containing only two of the three types of phosphors, etc. Various arrangements can also be provided. When the coating has a multilayer structure, the molding method may be changed for each layer.

FIG. 2 shows a schematic cross-sectional view of the InGaN-based LED chip 20. In the nitride semiconductor film 22 formed on the crystal substrate 21, a buffer layer (not shown), an undoped GaN layer 22a, an Si-doped n-type GaN contact layer 22b, and Si are sequentially formed from the crystal substrate 21 side. An active layer 22d having a quantum well structure (preferably a multiple quantum well structure) formed by alternately laminating doped n-type GaN cladding layers 22c, GaN barrier layers, and InGaN well layers (illustration of the internal laminated structure is omitted) Mg-doped p-type Al _0.2 Ga _0.8 N cladding layer 22e and Mg-doped p-type Al _0.02 Ga _0.98 N contact layer 22f are included. Each of these layers can be formed using a known vapor phase epitaxial growth method such as MOVPE method, MBE method, laser vapor deposition method, sputtering method or the like. The negative electrode composed of the transparent electrode 24a and the bonding pad 24b is formed on the n-type contact layer 22b partially exposed by etching. The reflective film 25 on the back side of the crystal substrate 21 is formed by a vapor deposition method such as vacuum deposition, sputtering, and CVD using a highly reflective metal such as Al, Ag, Rh, and Pt after forming the nitride semiconductor film 22. Can be formed to a thickness of 0.1 μm to 1 μm.

In the InGaN-based LED chip 20, light emission is caused by recombination of electrons and holes in the InGaN well layer included in the active layer 22d. The emission wavelength of the InGaN-based LED chip 20 can be controlled by changing the InN mixed crystal ratio a of the In _a Ga _1-a N crystal constituting the InGaN well layer. In order to set the emission peak wavelength to 400 nm to 440 nm, the InN mixed crystal ratio a may be set in the range of about 5% to 15%.

The reason why the InGaN-based light emitting device exhibits high luminous efficiency is that the miscibility between GaN and InN is not sufficiently high in the InGaN crystal constituting the quantum well layer.
It is said that there is a region where the InN mixed crystal ratio is locally increased on a nanometer scale, and the presence thereof increases the efficiency of luminescence recombination.
Due to the existence of such a mechanism, the luminous efficiency of an InGaN-based light emitting device having an emission peak wavelength of less than 400 nm to 410 nm varies greatly depending on the InN mixed crystal ratio of the InGaN well layer, and the InN mixed crystal ratio is increased. The higher the light emission wavelength, the higher the emission wavelength.
On the other hand, the crystallinity of the InGaN crystal decreases as the InN mixed crystal ratio increases. When these elements are combined, the luminous efficiency of the InGaN-based light emitting element is maximized when the emission peak wavelength is a violet wavelength that is between ultraviolet and blue, particularly when it is 410 nm to 430 nm.
An example of a blue phosphor that can be used by being dispersed in the coating 40 is shown in Table 1 below.

Particularly preferable blue phosphors include Eu-activated halophosphate phosphors and Eu-activated aluminate phosphors having high luminous efficiency. Since the Eu-activated aluminate-based phosphor has a sudden decrease in excitation efficiency when the wavelength of excitation light exceeds 410 nm, when the emission peak wavelength of the InGaN-based LED chip 20 is longer than 410 nm, Eu It is preferable to use an activated halophosphate phosphor.

  An example of the green phosphor that can be used dispersed in the coating 40 is shown in Table 2 below. The green phosphor shown in this table generally has only one peak in the emission spectrum.

  An example of an orange phosphor that can be used dispersed in the coating 40 is shown in Table 2 below. The orange phosphor shown in this table generally has only one peak in the emission spectrum.

  The green phosphor and orange phosphor exemplified above can be efficiently excited by violet light having a wavelength of 400 nm to 440 nm emitted from the InGaN LED chip 20. Types of green and orange phosphors used and coating of each phosphor so that the intensity of the combined spectrum of the emitted light of the green and orange phosphors is sufficiently high in the yellow wavelength range (570 nm to 600 nm) The amount added in 40 is determined.

Such a method using a green phosphor and an orange phosphor is considered to be a method that can generate light in the yellow wavelength region from purple light most efficiently at present. This is because it is difficult to obtain a highly efficient yellow phosphor that directly converts violet light into yellow light.
A transparent resin or glass can be used for the base material of the coating 40. Examples of the resin include various thermoplastic resins, thermosetting resins, photocurable resins, and the like. More specifically, methacrylic resins (polymethyl methacrylate, etc.), styrene resins (polystyrene, styrene-acrylonitrile). Copolymer), polycarbonate resin, polyester resin, phenoxy resin, butyral resin, polyvinyl alcohol, cellulose resin (ethyl cellulose, cellulose acetate, cellulose acetate butyrate, etc.), epoxy resin, phenol resin, silicone resin, etc. . Moreover, as glass, well-known low melting glass, such as a phosphoric acid type, a borophosphoric acid type, a vanadium boric acid type, an alkali silicic acid type, a bismuth type, is illustrated preferably.

In particular, for applications that require high output such as lighting, it is preferable to use a silicon-containing compound as the base material of the coating 40 for the purpose of heat resistance, light resistance, and the like.
The silicon-containing compound refers to a compound having a silicon atom in a molecule, for example, an organic material (silicone material) such as polyorganosiloxane, an inorganic material such as silicon oxide, silicon nitride, silicon oxynitride, and borosilicate. And glass materials such as phosphosilicate and alkali silicate. Among these, silicone materials are preferable from the viewpoints of transparency, adhesiveness, ease of handling, and excellent mechanical / thermal stress relaxation characteristics. The silicone-based material usually refers to an organic polymer having a siloxane bond as a main chain. For example, a silicone-based material such as a condensation type, an addition type, a sol-gel type, and a photo-curable type can be used.

With the exception of a portion of the Mn ⁴⁺ activated fluoride complex phosphor, the refractive index of the phosphor is usually greater than 1.5, so that the refraction of the base material of the coating 40 is increased in order to increase the phosphor extraction efficiency. The rate is desirably higher than 1.50. Examples of the resin material having a refractive index higher than 1.50 include epoxy resins, polycarbonate resins, styrene resins, diphenyldimethyl-based and phenylmethyl-based silicone resins, and the like. Epoxy resins, silicone resins, acrylic resins, polycarbonate resins, etc. can be refracted by adding high refractive index inorganic nanoparticles made of calcium oxide, cerium oxide, hafnium oxide, titanium oxide, zinc oxide, zirconium oxide, etc. It is known that the rate can be increased to about 1.8. The low-melting glass material usually has a refractive index higher than 1.50.

On the other hand, the refractive index of the Mn ⁴⁺ activated fluoride complex phosphor having a base crystal of hexafluorosilicate, particularly potassium hexafluorosilicate, is less than 1.40. Therefore, for such a phosphor, a transparent material having a refractive index of less than 1.45, such as a low refractive index type silicone resin based on dimethyl silicone, so that excitation light is not strongly reflected on the surface of the phosphor. It is preferable to disperse in the material. Generally speaking, if a Mn ⁴⁺ activated fluoride complex phosphor having a refractive index of less than 1.40 is used simultaneously with other phosphors having a refractive index higher than 1.50, A layer for dispersing the Mn ⁴⁺ activated fluoride complex phosphor and a layer for dispersing other phosphors are separately provided, and the refractive index of the base material of the layer for dispersing the Mn ⁴⁺ activated fluoride complex phosphor is set. The refractive index of the base material of the layer in which the other phosphor is dispersed is desirably lower.

  A light diffusing agent may be dispersed inside the coating 40 as necessary. Depending on the type of base material of coating 40, organic polymer (acrylic resin, polyethylene, etc.), metal oxide (titanium oxide, aluminum oxide, silicon dioxide, zinc oxide, magnesium oxide, etc.), calcium carbonate, barium titanate, sulfuric acid A known light diffusing agent comprising barium, magnesium hydroxide, calcium hydroxide or the like can be appropriately selected and used. The particle size of the light diffusing agent is preferably 1 μm to 20 μm, more preferably 2 μm to 10 μm.

However, since the light diffusing agent lowers the light extraction efficiency of the semiconductor light emitting device, it should not be added more than necessary.
The blue phosphor, green phosphor and orange phosphor added to the coating 40 absorb the emitted light of the InGaN-based LED chip 20 and emit blue light, green light and orange light, respectively. The light emitted from the blue phosphor may contribute to the excitation of the green phosphor. In addition, light emitted from the blue phosphor or the green phosphor may contribute to the excitation of the orange phosphor.

  When phosphor powder is added to coating 40 at a density that is too high, radiation from phosphor particles located near the bottom of the cavity is shielded by phosphor particles located near the surface of coating 40, resulting in phosphor There arises a problem that the extraction efficiency is lowered. In order to prevent this problem, it is possible to disperse the phosphor powder loosely so that a part of the emitted light of the InGaN-based LED chip 20 is emitted outside the coating 40 without undergoing wavelength conversion by the phosphor. preferable. Even in such a case, in the white light emitting device 1, since the emitted light of the LED chip 20 is light having a wavelength with low visibility, the spatial pattern caused by the difference in the radiation pattern of the LED chip and the phosphor is different. Color unevenness does not appear remarkably.

As described above, the present invention has been described based on the specific configuration example of the white light emitting device, but the present invention is not limited to the structure of the illustrated light emitting device.
For example, the white light emitting device of the present invention is not limited by the packaging form of the LED chip. The white light emitting device of the present invention may be a bullet type LED or a chip-on-board type LED.

In the white light emitting device of the present invention, the number of LED chips mounted per package is arbitrary, and may be one or several tens, for example.
The white light emitting device of the present invention is not limited by the form of the phosphor used. For example, a phosphor ceramic containing a phosphor phase, a phosphor particle layer obtained by depositing phosphor particles by electrophoresis or aerosol deposition, a single crystal phosphor thin film, and other various forms of phosphors are disclosed in the present invention. It can be used for the white light emitting device.
In addition, the white light emitting device of the present invention may be a device in which a semiconductor light emitting element and a phosphor are coupled via an optical element such as a lens, an optical fiber, or a light guide plate.
The present invention can also be preferably applied to a white light emitting device using an oxide semiconductor light emitting element such as a ZnO semiconductor light emitting element.

[Experimental example]
(Experimental example 1)
One InGaN-based LED chip having a 350 μm square and a main emission peak wavelength of 407 nm formed using a sapphire substrate was bonded onto the cavity bottom surface of a 3528 SMD type PPA resin package using a silicone resin-based transparent die bond paste. After bonding, the die bond paste was cured by heating at 150 ° C. for 2 hours, and then the LED chip-side electrode and the package-side electrode were connected using an Au wire having a diameter of 25 μm.

Next, a transparent binder mainly composed of a silicone resin, Eu-activated halophosphate-based blue phosphor Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu (abbreviation: SCA), Eu-activated alkaline earth (Ba, Sr) ₂ SiO ₄ : Eu (abbreviation: BSS) which is a silicate-based green phosphor and Sr ₂ BaSiO ₅ : Eu (abbreviation) which is an Eu-activated alkaline earth silicate-based orange phosphor. : SBS) were mixed in the amounts shown in Table 4 to prepare a phosphor paste. In Table 4,
The emission peak wavelength and chromaticity (CIE chromaticity coordinate value) measured in the powder state for each phosphor are also shown.

Next, the phosphor paste obtained above was injected into the cavity of the SMD type resin package on which the InGaN-based LED chip was mounted. The injected weight was 0.003 g. Then, after preheating at 110 degreeC for 1 hour, 150 degreeC was heated for 2 hours, and white LED was obtained by hardening a fluorescent substance paste.
The light emission characteristics when a current of 20 mA was applied to the white LED obtained by the above procedure were examined. The CIE chromaticity coordinate value of light emission was (x, y) = (0.266, 0.232), which was a value included in the white light region on the chromaticity diagram. The luminous flux was 3.3 [lm], and the luminous efficiency was 49.8 [lm / W]. The emission spectrum is as shown in FIG. 3, and the wavelength at which the spectrum intensity is maximum in the region longer than 515 nm is 575 nm. Further, the spectral intensity within the range of 570 nm to 600 nm was 89% or more of the spectral intensity at the wavelength of 575 nm at any wavelength within this range (the wavelength at which the spectral intensity is minimum within this wavelength range is 600 nm). The spectral intensity at a wavelength of 600 nm was 89% of the spectral intensity at a wavelength of 575 nm).

(Comparative experiment example)
Except that the red phosphor CaAlSiN ₃ : Eu (abbreviation: CASN) was used instead of the orange phosphor, and that the binder and each phosphor were mixed in the blending amounts shown in Table 5 and Experimental Example 1 Similarly, white LED was produced. The light emission characteristics when a current of 20 mA was applied to the white LED were examined. The CIE chromaticity coordinate value of light emission is (x, y) = (0.242, 0.222), which is a value included in the white light region on the chromaticity diagram. The luminous flux was 2.8 [lm], and the luminous efficiency was 42.2 [lm / W]. The emission spectrum is as shown in FIG. 4, and the wavelength at which the spectral intensity is maximum in the region longer than 515 nm is 528 nm. Further, looking at the spectral intensity in the range of 570 nm to 600 nm, it was less than half of the spectral intensity at the wavelength of 528 nm in almost the entire range (574 nm to 600 nm).

(Experimental example 2)
Twelve InGaN LED chips having a 350 μm square and a main emission peak wavelength of 408 nm formed using a sapphire substrate were flip-chip mounted using Au bumps on the electrodes formed on the cavity bottom surface of the SMD type package. The 12 LED chips mounted were connected in parallel.

Next, a transparent binder mainly composed of a silicone resin, BaMgAl ₁₀ O ₁₇ : Eu (abbreviation: BAM) which is an Eu-activated aluminate-based blue phosphor, and Eu-activated alkaline earth silicate system (Ba, Sr) ₂ SiO ₄ : Eu (abbreviation: BSS) that is a green phosphor and Sr ₂ BaSiO ₅ : Eu (abbreviation: SBS) that is an Eu-activated alkaline earth silicate-based orange phosphor. The phosphor paste was prepared by mixing in the blending amounts shown in Table 6. Table 6 also shows the emission peak wavelength and chromaticity (CIE chromaticity coordinate value) measured in the powder state for each phosphor.

Next, the phosphor paste obtained above was injected into the cavity of the SMD type package on which the InGaN-based LED chip was mounted. Then, after preheating at 110 degreeC for 1 hour, 150 degreeC was heated for 2 hours, and white LED was obtained by hardening a fluorescent substance paste.
The light emission characteristics when a current of 240 mA was applied to the white LED obtained by the above procedure were examined. The CIE chromaticity coordinate value of light emission was (x, y) = (0.344, 0.380), and was a value included in the white light region on the chromaticity diagram. The correlated color temperature was 5155 [K], and the average color rendering index Ra was 83. The luminous flux was 62 [lm], and the luminous efficiency was 76 [lm / W]. The emission spectrum is as shown in FIG. 5, and the wavelength at which the spectrum intensity is maximum in the region longer than 515 nm is 581 nm. Further, the spectral intensity within the range of 570 nm to 600 nm was 91% or more of the spectral intensity at the wavelength of 581 nm at any wavelength within this range (the wavelength at which the spectral intensity is minimum within this range is 600 nm). The spectral intensity at a wavelength of 600 nm was 91% of the spectral intensity at a wavelength of 581 nm).

DESCRIPTION OF SYMBOLS 1 White light-emitting device 10 Package 11 Insulating substrate 12 Package electrode 13 Reflector 20 InGaN-type LED chip 21 Crystal substrate 22 Nitride semiconductor film 23a, 24a Transparent electrode 23b, 24b Bonding pad 25 Reflective film 30 Bonding wire 40 Coating

Claims (12)

A blue phosphor, a green phosphor and an orange phosphor are excited using the emitted light of a semiconductor light emitting device having a main emission peak wavelength in the range of 400 nm to 440 nm, and are composed mainly of the emitted light of these phosphors (A ) White light-emitting device that uses white light as output light.
(A) The wavelength having the maximum spectral intensity in the region on the longer wavelength side from 515 nm is in the range of 535 nm to 600 nm, and the spectral intensity at an arbitrary wavelength in the range of 570 nm to 600 nm is on the longer wavelength side than 515 nm. White light that is more than half of the maximum spectral intensity in the region.   2. The white light emitting device according to claim 1, wherein a separation between a peak derived from the emitted light of the green phosphor and a peak derived from the emitted light of the orange phosphor is not observed on the spectrum curve of the white light.   The spectrum curve of the white light is convex upward within a wavelength range of 535 nm to 600 nm, and the spectral intensity on the longer wavelength side than 650 nm is less than half of the spectral intensity at a wavelength of 600 nm. The light-emitting device of description.   The white light emitting device according to any one of claims 1 to 3, wherein a main light emission peak wavelength of the semiconductor light emitting element is longer than 410 nm.   The white light emitting device according to claim 4, wherein a main light emission peak wavelength of the semiconductor light emitting element is longer than 420 nm.   The white light emitting device according to claim 4 or 5, wherein the semiconductor light emitting element is an InGaN-based light emitting element provided with an active layer having a quantum well structure. Furthermore, it has a Mn ⁴⁺ activated fluoride complex phosphor that can be excited by the emitted light of the semiconductor light emitting device, and by adding red light emitted from the fluoride complex phosphor to the white light, color rendering properties The white light emitting device according to claim 1, wherein the white light emitting device is improved. Furthermore, it has a Mn ⁴⁺ activated fluoride complex phosphor that can be excited by the emitted light of the semiconductor light emitting device, and by adding the red light emitted by the fluoride complex phosphor to the white light, The white light emitting device according to claim 1, wherein (color gamut) is expanded. Furthermore, it has a Mn ⁴⁺ activated fluoride complex phosphor that can be excited by the emitted light of the semiconductor light-emitting element, and adds the red light emitted from the fluoride complex phosphor to the white light, whereby the color temperature The white light-emitting device of any one of Claims 1-6 which made low.   The white light-emitting device according to claim 1, wherein the blue phosphor includes an Eu-activated halophosphate phosphor.   The green phosphor includes at least one phosphor selected from an Eu-activated alkaline earth silicate nitride phosphor and an Eu-activated alkaline earth silicate phosphor. The white light-emitting device of any one of Claims.   The orange phosphor includes one or more phosphors selected from Eu-activated nitride phosphors, Eu-activated oxynitride phosphors, and Eu-activated alkaline earth silicate phosphors. Item 12. The white light emitting device according to any one of Items 1 to 11.

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