JP2006032726A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure capable of stabilizing the ratios of intensities at every main wavelength component contained in output beams at every product to a light emitting device constituted so as to conduct a cascade excitation by a GaN light emitting element and a phosphor. <P>SOLUTION: The light emitting device is constituted while having the GaN light emitting elements emitting an original excitation light L, a primary phosphor member 1, and a secondary phosphor member 2. The primary phosphor member 1 contains primary phosphors 10 being excited by the original excitation light and emitting a primary fluorescence L1. The secondary phosphor member 2 contains secondary phosphors 20 being excited by the primary fluorescence L1 and emitting a secondary fluorescence L2. The primary phosphor member 1 and the secondary phosphor member 2 are arranged as mutually other members, so that the primary phosphors 10 and the secondary phosphors 20 independently exist while being divided into mutually different space regions without being mutually mixed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light-emitting device configured by combining a nitride semiconductor light-emitting element (hereinafter also referred to as “GaN-based light-emitting element”) and a phosphor.

2. Description of the Related Art There is known a light emitting device configured to use a GaN-based light emitting element that emits near ultraviolet to blue light having a wavelength of 380 nm to 480 nm as an excitation light source, and to emit a phosphor with excitation light emitted from the element.
The phosphor as used herein refers to a substance that can emit fluorescence (an organic or inorganic compound, or a substance to which a specific element is added), and in actual use, the phosphor is in the form of fine particles. In many cases, it is used as a phosphor member dispersed in a transparent medium such as resin or low-melting glass. In general, the wavelength conversion efficiency is improved when the phosphor is used as a fine particle rather than a lump.
Hereinafter, a phosphor that emits yellow light is referred to as a yellow phosphor. Similarly, for phosphors that emit fluorescence of other colors, the names of the fluorescence colors are named, for example, a red phosphor and a green phosphor. The prior art and the present invention will be described by calling a blue phosphor.

In Patent Document 1, a blue LED and a yellow phosphor are combined as a GaN-based light emitting element, and consists of blue light (a part of which excites the yellow phosphor and a part of the light as it is) and a yellow light. A light emitting device that emits white light of two complementary colors is disclosed. Hereinafter, in order to distinguish white light by two complementary colors such as blue light and yellow light from white light including the three primary color lights, it is also referred to as pseudo white light.
Pseudo white light is not suitable for color rendering because the three primary colors of light are not aligned, so it is used for applications that require only white light (designed to appear white), such as electronic bulletin boards and backlights. It has been.

Patent Document 2 describes a white light-emitting device that combines a GaN-based light-emitting element and three types of phosphors that emit RGB (red, green, and blue) primary colors, respectively. It also describes that a phosphor emitting light of a color other than the three primary colors is added to reinforce or modify the white light spectrum.
Such white light containing light of three primary colors or more has good color rendering properties and is expected as a lighting application.

In Patent Document 3, a primary phosphor (primary phosphor) is excited by ultraviolet rays (original excitation light) emitted from a GaN-based light emitting diode (GaN-based LED), and then further emitted by primary fluorescence emitted therefrom. A technique is disclosed in which the next phosphor (secondary phosphor) is excited to generate secondary fluorescence, and white light is obtained by synthesizing the primary fluorescence and the secondary fluorescence. Such a configuration in which excitation is performed in such a multistage manner is called “cascade excitation” or the like.
In a one-step excitation light emitting device constituted by a semiconductor light emitting element and a primary phosphor, since the emission wavelength of the light emitting element is likely to vary, the intensity of the primary fluorescence varies greatly. In contrast, phosphors have the property that the emission wavelength is less likely to fluctuate than semiconductor light-emitting devices, so in cascade excitation, even if the primary fluorescence fluctuates in terms of intensity, the fluctuation in terms of wavelength does not occur. Is small, there is an advantage that the fluctuation of the intensity of the secondary fluorescence is further improved.

FIG. 8 shows the light emitting elements, primary phosphors, and secondary phosphors emitting light in the conventional light emitting devices such as Patent Documents 1 to 3 described above, in particular, the light emitting devices performing cascade excitation. It is sectional drawing which showed typically whether it was assembled as an apparatus.
In the example of FIG. 8A, a GaN-based LED (excitation light source) 110 that emits near ultraviolet light (original excitation light) L10 is mounted in the stem 100, and the phosphor member 120 is a plate-like member (wavelength conversion plate). ) And closes the opening of the stem 100.
In the example of FIG. 8B, the GaN-based LED 110 is mounted on the stem 100, but the phosphor member 121 is not plate-shaped but is filled in the stem cavity.

  8A and 8B, in the transparent substrate constituting the phosphor member, the blue phosphor as the primary phosphor and the types different from each other by the number of colors necessary as the secondary phosphor. Particles of phosphor (for example, red phosphor, green phosphor, etc.) are dispersed. In the figure, these phosphor particles are schematically indicated by black dots.

  When the original excitation light L10 is irradiated to the phosphor member, first, primary fluorescence (blue light) is emitted from the primary phosphor (blue phosphor), and red light and green light are emitted from each secondary phosphor by the blue light. Is emitted. Blue light is used not only as excitation light but also as output light, and white light LW is output by these blue, red, and green light.

However, when the present inventors examined in detail about the structure of the light-emitting device which performs the above cascade excitation, it turned out that the following problems exist in the aspect of a phosphor member.
The problem is caused by the fact that the phosphor member has a configuration in which both the primary phosphor and the secondary phosphor are in the form of particles, and these are mixed and dispersed in one base material.
When dispersing fine particle phosphors in a substrate such as a resin, mix the fine particle phosphors with a liquid substrate material or a substrate material that has been made fluid by heating or the like. A manufacturing process of dispersing and curing in a state where it is disposed at a predetermined position of a mold or a stem is performed.
However, the phosphor particles settle before the substrate is cured, and the dispersion in the substrate becomes non-uniform. Moreover, the speed of sedimentation varies depending on the size, shape and surface condition of the particles, the specific gravity difference between the particles and the substrate for each type of phosphor, the viscosity of the substrate before curing, and the uniform particle size. It is generally difficult to obtain phosphor powders having Therefore, it is difficult to control the state of spatial distribution of the primary phosphor particles and the secondary phosphor particles in the substrate.
For this reason, the amount of the following (a) to (c) is not always constant for each product, and the ratio between the intensity of primary fluorescence and the intensity of secondary fluorescence contained in the output light is not stable. There arises a problem that the quality of white light is different every time.
(A) The amount of the original excitation light that can finally reach the primary phosphor while being absorbed and scattered by the secondary phosphor among the original excitation light incident on the phosphor member.
(B) Of the primary fluorescence emitted from the primary phosphor, the amount of primary fluorescence that can reach the secondary phosphor while being scattered by the primary phosphor itself, and the amount of primary fluorescence emitted to the outside.
(C) Of the secondary fluorescence emitted from the secondary phosphor, the amount of secondary fluorescence emitted to the outside while being scattered by the primary phosphor and the secondary phosphor.
JP-A-7-99345 JP 2004-14942 A JP 2003-147351 A JP 2000-331947 A JP 2002-280611 A

  An object of the present invention is to solve the above-mentioned problem, and for a light-emitting device configured to perform cascade excitation with a GaN-based light-emitting element and a phosphor, the intensity ratio for each main wavelength component included in the output light, An object of the present invention is to provide a structure that can be more stable for each product and can suppress variations in the quality of white light when the light-emitting device is a white light-emitting device.

The present invention has the following features.
(1) A light-emitting device that includes a nitride semiconductor light-emitting element that emits original excitation light, a primary phosphor member, and a secondary phosphor member,
The primary phosphor member includes a primary phosphor that emits primary fluorescence when excited by the original excitation light, and the secondary phosphor member includes a secondary phosphor that emits secondary fluorescence when excited by the primary fluorescence. And
The primary phosphor member is arranged so that the primary excitation light can be irradiated to the primary phosphor, the secondary phosphor member is arranged so that the primary fluorescence can be irradiated to the secondary phosphor, and
The primary phosphor member and the secondary phosphor member are arranged as separate members so that the primary phosphor and the secondary phosphor are separated and exist independently in different spatial regions without being mixed with each other. A light-emitting device,
(2) The light-emitting device according to (1) above, which is configured so that the original excitation light does not reach the secondary phosphor, or has a property that the secondary phosphor is not excited by the original excitation light.
(3) The light-emitting device according to (2), wherein the original excitation light is configured not to reach the secondary phosphor, and the configuration is the following configuration (a) and / or (b).
(A) A configuration in which the amount of primary phosphor contained in the primary phosphor member is selected so that substantially all of the original excitation light irradiated to the primary phosphor member is converted into primary fluorescence.
(B) A configuration in which a filter is provided that prevents the secondary phosphor member from being irradiated with the original excitation light.
(4) The light emitting device according to any one of (1) to (3), wherein the secondary phosphor member is arranged as a subdivided pattern on the surface of the primary phosphor member.
(5) Any of (1) to (3) above, wherein the secondary phosphor member is arranged as a subdivided pattern on the irradiated surface of the substrate arranged at a position where the primary fluorescence can be irradiated. The light emitting device according to 1.
(6) A part of the primary fluorescence is output as it is together with the secondary fluorescence, the primary fluorescence is blue light, the secondary fluorescence includes at least yellow light, and the output light is white light. The light-emitting device according to any one of (1) to (5), wherein the intensity of each of these fluorescences is adjusted.
(7) A phosphor emitting blue light is [(M, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu] (M is at least one of Ca, Sr, and Ba) or [BaMgAl ₁₀ O ₁₇ : Eu. The light emitting device according to (6), wherein the phosphor that emits yellow light is [(Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce, SrAl ₂ O ₄ : Eu].
(8) The primary fluorescence and / or the secondary fluorescence further includes green light and red light, and the output light is white light including blue light, yellow light, green light, and red light. The light-emitting device according to (7), wherein the intensity of each fluorescence is adjusted.
(9) A part of the primary fluorescence is output as it is together with the secondary fluorescence, the primary fluorescence is blue light, the secondary fluorescence includes at least green light and red light, and the output light The light emitting device according to any one of the above (1) to (5), wherein the intensity of each of these fluorescences is adjusted so that becomes white light.
(10) A phosphor emitting blue light is [(M, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu] (M is at least one of Ca, Sr and Ba) or [BaMgAl ₁₀ O ₁₇ : Eu. And a phosphor emitting green light is [BaMgAl ₁₀ O ₁₇ : Eu, Mn], [ZnS: Cu, Al] or [MGa ₂ S ₄ : Eu] (M is at least one of Ca, Sr and Ba) And phosphors emitting red light are [REuW ₂ O ₈ ] (R is at least one of Li, Na, K, Rb, and Cs), [M ₂ Si ₅ N ₈ : Eu] ( M is at least one of Ca, Sr, and Ba), [(Ca, Sr) S: Eu], [3.5MgO.0.5MgF ₂ .GeO ₂ : Mn], or [La ₂ O ₂ S: Eu]. ] (8) or (9) The light-emitting device of description.
(11) The light emitting device according to (8) or (9), wherein the phosphor emitting green light is [BaMgAl ₁₀ O ₁₇ : Eu, Mn].
(12) The light emitting device according to (1), wherein the original excitation light is light having a wavelength belonging to a wavelength range of 360 nm to 480 nm.

As described in the description of the background art, the phosphor member used in the conventional cascade excitation is such that, as shown in FIG. 8, both the primary phosphor and the secondary phosphor are in the form of particles in one substrate. Both were mixed.
However, even with this kind of dispersion, it is conventionally considered that sufficiently uniform dispersion is always obtained with good reproducibility, and the primary fluorescence and secondary fluorescence included in the output light The ratio was always the same, and no problems were raised.

  On the other hand, in the present invention, as illustrated in FIG. 1, the primary phosphor and the secondary phosphor are not mixed in one base material, but are divided into different spatial regions independently. As shown, the primary phosphor is included in the primary phosphor member, the secondary phosphor is included in the secondary phosphor member, and the primary phosphor member and the secondary phosphor member are separated from each other. It is arranged.

  The primary phosphor member and the secondary phosphor member are separate members independent from each other, not only in a mode in which each member can be handled separately as one independent component, but also with the primary phosphor member Even if it is inseparable in handling, such as a state in which the secondary phosphor members are stacked on each other, the primary phosphor and the secondary phosphor are assembled in different spatial areas and mixed together. Any mode that can exist without any problem is acceptable.

With the configuration of the present invention, the primary phosphor and the secondary phosphor are surely separated into different desired spatial positions, so that the primary excitation light is not absorbed or scattered by the secondary phosphor. Can reach. Therefore, it becomes easy to control the amount of the original excitation light that reaches the primary phosphor.
Similarly, the amount of primary fluorescence that reaches the secondary phosphor and the ratio of primary fluorescence and secondary fluorescence emitted to the outside can be easily controlled, and variations in the quality of output light from product to product are reduced.

Also, when dispersing phosphor particles in a substrate, the optimum dispersion conditions for each phosphor type are generally not the same, so the more types of phosphors to be simultaneously dispersed in the substrate, the more optimal Manufacturing conditions are narrowed.
As in the present invention, by separating the primary phosphor member and the secondary phosphor member as separate members that are independent from each other, the manufacturing conditions for preferably dispersing the phosphor particles in the substrate are reduced. Can be avoided.

The light emitting device according to the present invention includes a GaN-based light emitting element S that emits original excitation light L, a primary phosphor member 1, a secondary light, as schematically shown in FIGS. 1 (a) and 1 (b). And at least a phosphor member 2.
The primary phosphor member 1 includes a primary phosphor 10. The phosphor 10 is a substance that emits primary fluorescence L1 when excited by the original excitation light L. The primary phosphor member 1 is arranged with its position, orientation, etc. selected with respect to the original excitation light L so that the primary excitation light L is sufficiently irradiated to the primary phosphor 10 and can emit sufficient primary fluorescence L1. Has been.
The secondary phosphor member 2 includes a secondary phosphor 20. The phosphor 20 is a substance that emits secondary fluorescence L2 when excited by the primary fluorescence L1. The secondary phosphor member 2 is arranged with a selected position, orientation, etc. with respect to the primary fluorescence L1, so that the primary fluorescence L1 can be sufficiently irradiated to the secondary phosphor and emit sufficient secondary fluorescence L2. Has been.
The important point here is that, as described in the effect of the present invention, the primary phosphor particles and the secondary phosphor particles are separated from each other in different spatial regions without being mixed with each other. That is, both phosphor particles are present in separate members independent of each other. With this configuration, the effects described in the effect of the invention can be obtained.

The GaN-based light-emitting element that is an excitation light source may be various light-emitting elements such as LEDs and LDs (semiconductor lasers) in which a nitride semiconductor is used as a material of the light-emitting portion. A GaN-based LED is preferable as an excitation light source for the configuration.
The nitride semiconductor is _a compound semiconductor represented by _{In A Ga B Al C N (} 0 ≦ A ≦ 1,0 ≦ B ≦ 1,0 ≦ C ≦ 1, A + B + C = 1), for example, AlN, GaN AlGaN, InGaN, etc. are mentioned as important compounds.

There is no limitation on the emission wavelength of the GaN-based light emitting device, but in order to excite various color phosphors as the original excitation light, it is preferably light having higher energy, a short wavelength from blue to ultraviolet, That is, a wavelength belonging to the range of 360 nm to 480 nm is preferable.
In particular, a GaN-based light emitting device using In _A Ga _1- AN having a composition ratio determined so as to have such a light emission wavelength as a light emitting layer has a high light emission efficiency, and thus has a high output and an excitation light source. As preferred. In addition, a light emitting layer having a single quantum well (SQW) or multiple quantum well (MQW) structure using In _A Ga _1-A N as a well layer is more preferable because it is more efficient. In this case, examples of the material for the barrier layer in the quantum well structure include GaN.

If the output light is white light and at least three primary color lights (RGB three-wavelength light) for producing the white light are all made of a phosphor, the emission wavelength of the GaN-based light emitting element is 410 nm or less. Preferably, 380 nm to 410 nm is more preferable. As described above, a high-efficiency, high-power GaN-based light-emitting element having a light-emitting layer made of In _A Ga _1-A N can be used as an excitation light source and exhibits high excitation efficiency in a wavelength range of 380 nm to 410 nm. This is because RGB phosphors are available.
Alternatively, the light-emitting device may be configured so that the excitation light is blue-violet light to blue light (wavelength 400 nm to 480 nm) or the like and is emitted together with primary fluorescence and secondary fluorescence as part of output light.

There is no limitation on the element structure of the GaN-based light-emitting element, and any known GaN-based light-emitting element may be used, but it is preferable to obtain a higher output with the same current.
FIG. 2 is a schematic diagram showing an example of a preferable element structure of a GaN-based LED. An n-type contact layer 31 is sequentially formed on a crystal substrate (such as a sapphire substrate) 30 via a GaN-based low-temperature growth buffer layer 30b. , Light emitting portion 35 (n-type cladding layer 32 / MQW light emitting layer (detailed laminated structure not shown) 33 / p-type cladding layer 34), p-type contact layer (multiple layer structure may be used) (Not shown) are stacked by vapor deposition, and an n-electrode P1 and a p-electrode P2 are provided in each contact layer.
In the example shown in the figure, the crystal substrate 30 is drawn on the lower side for the sake of explanation. However, the p-electrode P2 is directly connected to the circuit with the p-electrode P2 facing the mounting substrate side (so-called flip chip) The configuration may be such that light is extracted from the back surface of the substrate by performing mounting) and the phosphor portion is irradiated with the light.

  In the example of FIG. 2, the unevenness 40 is processed on the upper surface of the crystal substrate 30 (the surface on which the GaN-based crystal layer grows) as a preferred embodiment. This unevenness reduces the dislocation density of the GaN-based crystal layer and further increases the light emission efficiency in the light emitting part (improves internal quantum efficiency). Moreover, this unevenness does not keep the light generated in the element confined, but shows an effect of emitting more to the outside (improvement of external quantum efficiency). Combined with these actions, a high-power GaN-based LED can be obtained. In the case of such an element structure, the above-described element for flip chip mounting is a preferable aspect from the viewpoint of extracting more light to the outside through the uneven surface.

  For the crystal substrate, the buffer layer, the crystal growth technique on the substrate, the light emitting element structure, the mounting technique, and the like for constituting the GaN-based light emitting element, conventionally known techniques may be referred to (Patent Documents 4 and 5).

In the embodiment of FIG. 1A, the primary phosphor member 1 and the secondary phosphor member 2 are each formed as a plate-shaped member, and these are in a two-layer state, and a GaN-based LED is mounted. The opening of the stem 50 is closed.
Further, in the embodiment of FIG. 1B, the primary phosphor member 1 and the secondary phosphor member 2 are formed as a dome-shaped resin mold and cover the GaN-based LED and the stem 50 in a double manner.
In these embodiments, both the primary and secondary phosphor members have a structure in which fine particles of phosphor are dispersed in a transparent resin base material.
In addition, the primary phosphor member is laminated on the excitation light source side and the secondary phosphor member is on the outside (exit side), so that the light of the original excitation light is not absorbed or scattered by the secondary phosphor. First, since it reaches the primary phosphor, the conversion efficiency is good.
When the GaN-based light emitting device is a flip chip mounting type device, the primary phosphor member and the secondary phosphor member may be arranged in two layers on the back surface of the crystal substrate of the light emitting device so as to be directly cascade-excited.
There is no limitation on how the primary phosphor member and secondary phosphor member are formed, and any combination of mold type, plate type, reflective surface, and coating on a transparent substrate is possible. do it. The light-emitting device of the present invention can be increased in size by using a plurality of GaN-based semiconductor elements mounted side by side as an excitation light source. In the case of increasing the size in this way, the primary phosphor member or secondary It is preferable that the phosphor member be a plate type or a transparent substrate coated.

  The light-emitting device of the present invention may be configured to guide light from a GaN-based light-emitting element that is an excitation light source to a phosphor member via a light guide such as a plate, rod, or fiber. The primary fluorescence emitted from the body member may be guided to the secondary phosphor member by such a light guide.

A mode in which the secondary phosphor is excited not only by the primary fluorescence but also by the original excitation light to emit the secondary fluorescence is not preferable in the following points.
That is, when the secondary phosphor can be excited even by the original excitation light, when both the original excitation light and the primary fluorescence reach the secondary phosphor, the fluorescence generated by the secondary phosphor depending on the ratio (original excitation). Since the intensity of the fluorescence generated by excitation by light and the intensity of the fluorescence generated by excitation by the primary fluorescence change, the emission intensity of the secondary phosphor is greatly affected by the spatial distribution of the primary phosphor. This is because control for stabilizing the component of the output light becomes difficult.

In order to prevent the secondary phosphor from being emitted by being excited by the original excitation light, (a) the primary excitation light hardly reaches the secondary phosphor, or (ii) the secondary phosphor. For example, the phosphor itself may be a material that is not excited by the original excitation light.
Examples of the configuration for achieving the above (a) include the following configurations (a) and / or (b).
(A) A primary phosphor member is disposed between an excitation light source and a secondary phosphor member so that substantially all of the original excitation light is converted into primary fluorescence in the primary phosphor member. The structure which adjusts the quantity of the primary fluorescent substance contained in.
(B) A configuration in which a filter layer that transmits primary fluorescence but absorbs or reflects original excitation light is disposed between the primary phosphor member and the secondary phosphor member.

FIG. 3 is a schematic diagram illustrating another configuration example when the primary phosphor member and the secondary phosphor member are disposed on the stem on which the GaN-based LED is mounted.
In the example of FIG. 3A, the plate-like primary phosphor member 1 and the secondary phosphor member 2 are in a two-layer state to close the opening of the stem 50, as in the embodiment of FIG. However, the stacking order of the primary phosphor member 1 and the secondary phosphor member 2 is opposite to that shown in FIG. The original excitation light L once passes through the secondary phosphor member 2 and enters the primary phosphor member 1, a part of the primary fluorescence generated there is output to the outside world, and a part enters the secondary phosphor member 2. Then, secondary fluorescence L2 is emitted.
In such a configuration, it is preferable to use, as the secondary phosphor, a substance having a property that is not excited by the original excitation light, thereby allowing a larger amount of the original excitation light to enter the outer primary phosphor member. Can do.

In the example of FIG. 3B, the primary phosphor member 1 a and the secondary phosphor member 2 a have a plate shape and are stacked, but the primary phosphor 1 a is formed on one main surface of the transparent substrate 3. The secondary phosphor 2a is thinly coated.
In the example of FIG. 3C, the primary phosphor member layer 1a is coated on the inner main surface of the transparent substrate 3, and the secondary phosphor member layer 2a is coated on the outer main surface.
3 (b) and 3 (c), the stacking order or position of the primary phosphor member layer and the secondary phosphor member layer may be reversed as shown in FIG. 3 (a) with respect to FIG. .

In the example of FIG. 4 (a), the primary phosphor member 1 is a plate-like material in which the primary phosphor is dispersed in the base material as in the example of FIG. 1 (a). Are formed, and the secondary phosphor member 2 is filled therein. In this aspect, it can be said that the secondary phosphor member layer is arranged as a pattern formed by the concave portion.
Thus, the aspect which arrange | positions a secondary fluorescent substance member layer as a subdivided pattern is a secondary fluorescent substance with the intended in-plane distribution pattern (an equal pattern, a biased pattern) in a plate-shaped fluorescent substance member. Special functions and effects such as the ability to freely control the quantitative ratio of each secondary phosphor in a plane when a plurality of secondary phosphors are dispersed. Have. This aspect will be described in detail later.

  In the example of FIG. 4B, the primary phosphor member 1 is formed as a dome-shaped resin mold as in the example of FIG. 1B, and covers the GaN-based LED and the stem 50. On the other hand, the secondary phosphor member 2 is formed as a plate-like member as in the example of FIG. 1A, and closes the opening of the stem 50 on which the GaN-based LED is mounted.

In the example of FIG. 4C, the primary phosphor member 1 is coated on the funnel-shaped (parabolic) reflecting surface of the stem, and the primary fluorescence L1 generated there is directed upward. . The secondary phosphor member 2 is formed as a plate-like member as in the example of FIG. 4B, and closes the opening of the stem 50 on which the GaN-based LED is mounted.
The primary phosphor member 1 and the secondary phosphor 2 may be interchanged with each other.

  In the example of FIG. 5, the primary phosphor member 1 is coated on the reflecting surface of the stem as in the example of FIG. 4C, but the secondary phosphor member 2 is further coated on the lower layer side. Yes. The primary phosphor member 1 is also formed as a plate-like member as in the example of FIG. 4B, and closes the opening of the stem 50. Of the original excitation light L, the light directed upward is converted into primary fluorescence L1 by the plate-like primary phosphor member 1 at the stem opening. In addition, the light of the original excitation light L toward the reflecting surface of the stem is first converted into primary fluorescence L1 by the primary phosphor, and further the primary fluorescence L1 that has proceeded to the lower layer side (inside) becomes secondary fluorescence L2. The secondary fluorescence L2 passes through the primary phosphor member 1 on the surface layer and travels upward.

In the present invention, cascade excitation is performed by the primary phosphor member and the secondary phosphor member, but whether to use the original excitation light and the primary fluorescence as the output light may be freely selected according to the application.
A preferred embodiment is a combination in which the original excitation light is used as ultraviolet light and is not used as output light, while the primary fluorescence is used as blue light, which is used as output light and the excitation light of the secondary phosphor. . In this case, if at least a red phosphor and a green phosphor are used as the secondary phosphor, white light can be output.
Alternatively, a yellow phosphor may be used as the secondary phosphor, and pseudo white light generated by blue light (primary fluorescence) and yellow light (secondary fluorescence) may be output. When the color rendering property is improved by further adding a red phosphor or a green phosphor to the pseudo white light, the red phosphor or the green phosphor may be included in either the primary phosphor or the secondary phosphor. .
In the light emitting device of the present invention, the primary phosphor is not necessarily one type, and may include a phosphor that emits fluorescence not related to the excitation of the secondary phosphor.

The aspect which arrange | positions the secondary phosphor member layer as a subdivided pattern schematically demonstrated in the example of Fig.4 (a) is demonstrated in detail.
6 (a) is a perspective view of the embodiment of FIG. 4 (a) as viewed from above, in which the secondary phosphor member layer 2 has a fine rectangular shape on the surface of the plate-like primary phosphor member 1. FIG. The regions are arranged as a pattern in which the regions are spaced apart. In other words, the surface of the primary phosphor member 1 is divided into a plurality of small areas, and the presence or absence of the secondary phosphor 20 is selected for each small area. Here, the type of secondary phosphor 20 may be selected for each small region. As a result, the secondary phosphor member layer 2 is arranged as a subdivided pattern on the surface of the primary phosphor member 1.

In the example of FIG. 6B, the secondary phosphor member layer 2 is coated on the main surface of the substrate 21 independent of the primary phosphor member 1. The substrate 21 is disposed at a position where primary fluorescence can be irradiated. The secondary phosphor member layer 2 is arranged as a pattern in which fine rectangular regions are spaced apart from each other on the irradiated surface of the substrate 21 where primary fluorescence can be irradiated. The example in the figure is configured such that the primary fluorescence is irradiated to the irradiated surface through the substrate 21, and the substrate 21 is transparent so that the primary fluorescence can be transmitted.
Hereinafter, also in the example of FIG. 6A, the surface of the surface of the primary phosphor member that is irradiated with the primary fluorescence and on which the secondary phosphor member layer is disposed is referred to as an “irradiated surface”.

An aspect in which the secondary phosphor member layer is arranged as a subdivided pattern (hereinafter abbreviated as “phosphor subdivision arrangement”) exhibits the following effects.
For example, as in the embodiment of FIG. 1, when the secondary phosphor member is a single block in which a particulate phosphor is dispersed in a resin base material, the primary fluorescence is incident on the secondary phosphor member. The ratio of the primary fluorescence and the secondary fluorescence emitted from the secondary phosphor member is mainly determined by the spatial distribution of the secondary phosphor fine particles in the resin substrate (as described above, these are the secondary fluorescence). It is controlled by the particle size of the next phosphor fine particles, the blending ratio with respect to the resin base material, etc.
On the other hand, as illustrated in FIGS. 6A and 6B, the following effects can be obtained by arranging the secondary phosphor member layer as a subdivided pattern.
(A) Even if there are a plurality of types of secondary phosphors, by controlling the pattern formed in the irradiated surface by the secondary phosphor member layer including each secondary phosphor, in the irradiated surface, The distribution of each secondary phosphor (uniform distribution, uneven distribution) and the quantitative ratio (equal ratio, different ratio) of each secondary phosphor can be controlled. Similarly, even when there is only one kind of secondary phosphor, the manner of distribution in the irradiated surface can be freely controlled as described above.
(B) Since a gap region where the secondary phosphor member layer does not exist is formed between the regions where the secondary phosphor member layer is formed, the gap region is surely formed within the irradiated surface. A region where the secondary phosphor does not exist (a region where excitation light or primary fluorescence can pass without being substantially affected by the secondary phosphor) can be used. Such an effect is remarkably useful when the original excitation light or the primary fluorescence incident on the irradiated surface is allowed to pass through to be output light.

In the phosphor subdivision arrangement, the secondary phosphor member may be arranged on either the front side or the rear side of the primary phosphor member as viewed from the excitation light source. In the example of FIGS. 6A and 6B, the secondary phosphor member 2 is disposed behind the primary phosphor member 1 when viewed from the excitation light source S. Further, for example, in the example of FIG. 6B, the transparent substrate 21 may be turned over and the secondary phosphor member 2 may be disposed on the front side of the primary phosphor member 1 when viewed from the excitation light source S.
In addition to the positional relationship described above, there is no limitation on the relationship between the incident direction of the original excitation light with respect to the phosphor member and the extraction direction of output light emitted from the phosphor member. In the example of FIGS. 6A and 6B, the light emitting device may be configured to extract output light including at least secondary fluorescence from the side of the surface on which the secondary phosphor member layer 2 is formed. Alternatively, it may be configured to be taken out from the surface facing the excitation light source S. In the latter case, the output light traveling in the direction away from the excitation light source S may be positively directed toward the excitation light source S by the reflecting means.

  The irradiated surface on which the secondary phosphor member layer is to be disposed may be a flat surface or an arbitrary curved surface depending on the use of the light emitting device. When the irradiated surface is a simple concave shape or a convex curved surface, the irradiated surface may be convex toward the traveling direction of the excitation light or may be concave. The simple concave or convex curved surface may be a spherical surface or a cylindrical side surface.

  When the secondary phosphor member layer is arranged as a subdivided pattern, the degree of subdivision is such that secondary fluorescence, primary fluorescence and / or original excitation light emitted from the light emitting device is sufficiently mixed and output light It is preferable to make it fine until a color unevenness that can be detected does not exist. To what extent subdivision is appropriate depends on the scale of the light emitting device, the technology for forming the subdivision pattern, the configuration and characteristics of the optical components such as lenses and the optical system included in the light emitting device, cost, effects, etc. It may be determined in consideration of.

  Typical types of subdivision patterns include a large number of single dot-like areas, regularly or irregularly arranged patterns, a long and elongated strip-like area, a pattern arranged at regular or irregular intervals, Examples thereof include dendritic patterns, lattice patterns, mesh patterns, and the like. For each phosphor, the size of the region (the diameter of the dot-like region, the width of the belt-like region, the width of the linear region constituting the lattice / mesh shape, etc.) and the number of existence (dispersion density of the dot-like region, By selecting an interval, a grid-like / mesh-like fineness, etc., it becomes easy to finely set the balance of the light intensity of each color included in the output light.

Typical shapes of the dot-like regions may be a circle, a triangle, a rectangle, a hexagon, a rhombus, a polygon, an indeterminate shape, or any other shape.
The arrangement pattern of these dot-like regions may be selected according to the use, such as a fine pattern, a square matrix pattern, a pattern repeated according to a specific rule, or a random pattern.

  The formation density of the secondary phosphor member layer may be intentionally unevenly distributed depending on the application. For example, when arranging a circular dot-shaped secondary phosphor member layer on the substrate surface, it is arranged locally at a high density in a specific part (the central part of the figure, for example, the part directly above the excitation light source) For example, the density of the arrangement is lowered as it expands. Such an uneven arrangement has the same effect as the configuration in which the concentration of the secondary phosphor is changed (for example, correction of the problem that the color of the light changes depending on the direction and angle of viewing the output light from the light emitting device). In addition, the distribution density of the secondary phosphor in the irradiated surface can be controlled easily and freely simply by changing the arrangement pattern and the size of the secondary phosphor member layer. It becomes possible.

  Typical examples of the arrangement pattern of the band-like regions include parallel stripes, multiple concentric circles, multiple spirals, meanders, radials, etc., all of which are locally striped. is there. Such a belt-like region may be a pattern branched in the middle.

When the secondary phosphor member layer is formed in a dot shape, the size of the dot varies depending on the overall scale of the apparatus and the distance to the irradiation target, but for example, an element outer shape of about 0.35 mm × 0.35 mm One GaN-based light emitting element is used as an excitation light source, and a single phosphor part is associated with this to form a light emitting device. The illuminated surface of the phosphor part is a square plane having a side of about 5 mm, In the case where square dots formed of the secondary phosphor member layer and square gap regions having the same size and not including the secondary phosphor are alternately arranged in a square matrix without gaps, the length of one side of the square Is preferably about 0.01 mm to 1 mm, and more preferably 0.1 mm to 0.5 mm. In this case, the entire area of the irradiated surface is divided into 5 × 5 to 500 × 500 sections (half are sections including secondary phosphors, and half are sections not including secondary phosphors). Become.
Even when the dot shape is circular or irregular, the size may be equivalent to the above square.
When the secondary phosphor member layer is formed in a band shape, the individual band width is preferably about 0.01 mm to 1 mm, particularly preferably 0.1 mm to 0.5 mm.
Note that the length of one side of the square dots and the width of the band-shaped region are not particularly limited as long as color unevenness that is a problem in the use of the light-emitting device does not occur. If it is the use of this, you may enlarge to about 10 mm or more.

  When there are multiple types of secondary phosphors to be arranged, the secondary phosphor member layer including each secondary phosphor is arranged as any subdivision pattern, and the area occupied by each secondary phosphor member layer The method of selecting the light source may be freely selected in consideration of the balance of the light intensity of each color included in the output light.

  In the above-described configuration in which the gap region where the secondary phosphor member layer is not formed is provided, the primary fluorescence passes through the gap region and is included in the output light together with the secondary fluorescence. By this design, the mixing ratio of the primary fluorescence and the secondary fluorescence contained in the emitted light can be controlled easily and accurately simply by designing the shape, size, and dispersion density of the dots and band-like regions made up of the secondary phosphor member layer. be able to.

  As a method of arranging the secondary phosphor member layer as a subdivided pattern, a coating composition in which secondary phosphor fine particles are dispersed is prepared, and predetermined printing is performed on a predetermined surface by offset printing, screen printing, ink jet printing, or the like. And a method of forming a phosphor thin film patterned in a predetermined shape on a predetermined surface by a mask process using a photolithography technique.

  In the above, the example in which the secondary phosphor member layer is arranged as a subdivided pattern has been described. On the other hand, when a plurality of primary phosphors are used, primary phosphor members including different primary phosphors are used as independent members. It may be formed, and a part or all of it may be arranged as a layered body formed as a subdivided pattern in the surface that receives the irradiation of the original excitation light. In this case, the shape and arrangement of the secondary phosphor member are not particularly limited. Of the primary phosphor member layers arranged as a subdivided pattern, the layer including the primary phosphor member involved in cascade excitation. It is preferable to arrange a secondary phosphor member layer in the same pattern as the primary phosphor member layer on or below, because the efficiency of cascade excitation is improved.

The primary phosphor member and the secondary phosphor member may be a member formed of a compound in which particulate phosphor is dispersed in a transparent medium, or the particulate phosphor adheres to the substrate. In the case of a phosphor that can constitute a member by itself, it may be a member formed only of the phosphor. The phosphor that can constitute a member by itself is, for example, a (thin) film shape by a vapor deposition method such as a chemical vapor deposition method, a sputtering method, or a vacuum deposition method, a solvent casting method, a sol-gel method, etc. And a phosphor that can be formed into a molded body by melt molding or powder molding.
When the phosphor member layer is arranged on the substrate, the phosphor may be arranged so as to rise from the plate surface, or as shown in FIG. 4A, the substrate (in this case, the primary phosphor member is connected to the substrate). A recess is formed on the plate surface, and the recess is filled with a secondary phosphor member.
If the material of the substrate is a device configuration in which the original excitation light and primary fluorescence pass through the substrate, a material that can transmit the light should be used. For example, a silicone resin, an epoxy resin, a polycarbonate, a fluororesin, Various inorganic glasses and the like can be mentioned as preferable materials.

Examples of the blue phosphor include [(M, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu], [(Ba, Sr) MgAl ₁₀ O ₁₇ : Eu], and [Ca ₂ B ₅ O ₉ Cl: Eu]. ], [M ₃ MgSi ₂ O ₈ : Eu], [M ₂ MgSi ₂ O ₇ : Eu], [CaMgSi ₂ O ₆ : Eu], [Sr ₅ Cl (PO ₄ ) ₃ : Eu] and [ZnS: Ag (Wherein M is at least one of Ca, Sr, and Ba).

As the secondary phosphor, a phosphor that emits a necessary type of color as output light and that has the property of being excited by primary fluorescence may be selected.
For example, red phosphors that can be excited by blue phosphors include [Ln ₂ O ₂ S: Eu (Ln = Y, La, Gd, Lu)], [(Zn _a Cd _1-a ) S: Ag, Cl. , (0.5>a> 0.2)], [REuW ₂ O ₈ ], [M ₂ Si ₅ N ₈ : Eu], [3.5MgO · 0.5MgF ₂ · GeO ₂ : Mn], and [ (Ca, Sr) S: Eu] (where M is at least one of Ca, Sr, and Ba, and R is at least one of Li, Na, K, Rb, and Cs). One or more types of phosphors.

The green phosphor that can be excited by the blue phosphor includes [(Zn _a Cd _1-a ) S: Cu, Al, (1 ≧ a> 0.6)], [(Zn _a Cd _1-a ). S: Au, Al, (1 ≧ a> 0.6)], [(Zn _a Cd _1-a ) S: Ag, Cl, (1 ≧ a> 0.6)], [(Ba, Sr) MgAl ₁₀ O ₁₇ : Eu, Mn], [SrAl ₂ O ₄ : Eu], [Sr ₄ Al ₁₄ O ₂₅ : Eu] and [MGa ₂ S ₄ : Eu] (where M is one of Ca, Sr, and Ba) One or more phosphors selected from (at least one).

According to studies by the present inventors, a green phosphor (ZnS phosphor) based on Zn _a Cd _1-a S has a synergistic effect between moisture in the air and short wavelength light from the light emitting element. Has the problem of changing to black.
Due to this discoloration, it was found that a white light emitting device using a ZnS-based phosphor has a decrease in color rendering properties and luminance due to a decrease in the green light component over time.
When this problem was solved and the use of a reliable green phosphor that was stable over time was examined, the stability over time, such as [(Ba, Sr) MgAl ₁₀ O ₁₇ : Eu, Mn], was used. It has been found that an oxide-based phosphor is more preferable.
However, the oxide phosphor is superior to the ZnS phosphor in terms of the stability (reliability) of the material. However, when the emission characteristic (emission spectrum) is examined, the half width of the emission spectrum is Since it is narrow, it has been found that the component at around 540 nm to 650 nm, which is the component on the long wavelength side, is missing compared to the ZnS-based phosphor before blackening.

Therefore, in the present invention, a configuration in which an oxide phosphor such as the above [(Ba, Sr) MgAl ₁₀ O ₁₇ : Eu, Mn] is used as the green phosphor and a yellow phosphor is added to this is recommended.
Thereby, a long wavelength component missing in green light can be supplemented by yellow light, and a preferable white light emitting device having both excellent stability (reliability) and excellent color rendering properties can be obtained.

Yellow light is light having an emission distribution within a wavelength range of about 420 nm to about 750 nm.
The yellow phosphor is preferably a material that is excited by light emitted from the primary phosphor (blue phosphor). Such phosphor materials include [(Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce], [SrAl ₂ O ₄ : Eu], [(Y, Gd, Sc) -Al—O—. N: (Eu, Ce)] is one or more types of phosphors.
When [(Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce] is used as the yellow phosphor, the material is excited by blue light having an emission distribution with a wavelength of 400 nm to 550 nm. It is a preferable combination to use [(Ba, Sr) MgAl ₁₀ O ₁₇ : Eu].

In the graph of FIG. 7, the main emission wavelength of the GaN-based light emitting element is 395 nm, and blue phosphor [(Ca, Sr, Ba, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu] is used as the primary phosphor. When a red phosphor [LiEuW ₂ O ₈ ], a green phosphor [BaMgAl ₁₀ O ₁₇ : Eu, Mn], and a yellow phosphor [(Y, Gd) ₃ Al ₅ O ₁₂ : Ce] are used as the next phosphor It is a graph which shows the spectrum of white light output (blue light, red light, green light, yellow light).
As is apparent from the graph of FIG. 6, the long wavelength component missing in the green light is supplemented by the yellow light, which is a preferable white light.

  The phosphor layer may be a layer in which phosphor fine particles are dispersed in a transparent medium (resin, low-melting glass, etc.), or may be formed as a thin film by chemical vapor deposition, sputtering, vacuum evaporation, or the like. . A combination of these may also be used.

  The primary phosphor and the secondary phosphor involved in cascade excitation are not limited to one type. For example, (cascade excitation by one primary phosphor and a plurality of secondary phosphors), (cascade excitation by a plurality of primary phosphors and one secondary phosphor), (a plurality of primary phosphors, Cascade excitation with a plurality of secondary phosphors). From the viewpoint of controllability, a simpler system is preferable.

  Two or more different cascade excitation systems may exist in one light emitting device. For example, a cascade excitation system with a blue phosphor (primary) and a yellow phosphor (secondary) and a cascade excitation system with a green phosphor (primary) and a red phosphor (secondary) are simultaneously provided.

  Phosphors that do not participate in cascade excitation (phosphors that are excited by the original excitation light and do not generate primary fluorescence that excites other phosphors) may be added to the phosphor member that the original excitation light reaches, In that case, you may add to the phosphor member used as the separate body from the primary phosphor member and secondary phosphor member which are related to cascade excitation.

Example 1
In the present embodiment, a near-ultraviolet LED using InGaN as a light emitting part material as an excitation light source, a primary phosphor member including a blue phosphor, a red phosphor, and a green phosphor with a structure similar to FIG. In combination with a secondary phosphor member containing, a light emitting device that outputs white light was actually manufactured and its performance was evaluated.

[Main specifications of near-ultraviolet LED]
Emission wavelength peak: 382 nm.
Structure of light emitting part: MQW structure in which 6 pairs of InGaN well layers / GaN barrier layers are stacked.
Dislocation density reduction method: Striped irregularities are processed on a sapphire substrate, and GaN-based crystals are facet grown on the bottom and top surfaces of each concave portion, and then flattened by making lateral growth dominant. Facet LEPS method.
Bare chip outline: 350 μm × 350 μm square.
Mounting method: Flip chip Light emission output in bare chip state: 6.5 mW at a current of 20 mA

[Main specifications of phosphor]
Blue phosphor: (Sr, Ca, Ba, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu
Red phosphor: La ₂ O ₂ S: Eu
Green phosphor: BaMgAl ₁₀ O ₁₇ : Eu, Mn

[Outline of manufacturing process of light-emitting device]
A housing having an insulating substrate on which a wiring pattern for arranging near-ultraviolet LEDs was formed and a frame-like reflecting member surrounding the near-ultraviolet LED was prepared.
Near-ultraviolet LEDs were mounted on the wiring pattern in the housing via a conductive adhesive such as Ag paste.
The case was filled with a silicone resin (the filled resin is not specifically shown in FIG. 1A), the near-ultraviolet LED was covered, and the resin was further cured by heating to form an inner layer.

Next, a silicone resin containing blue phosphor (resin made of the same material as the inner layer) is formed in a thick film on a smooth substrate, heated and cured, and then peeled off from the substrate to form a film. Primary phosphor member.
The primary phosphor member was attached to the upper surface of the inner layer with the same material resin as the silicone resin of the inner layer interposed as an adhesive.

Similar to the method for forming the primary phosphor member, a silicone resin containing a red phosphor and a green phosphor is formed in a thick film on a smooth substrate, heated to form a film, and a secondary phosphor. A body member was obtained.
As shown in FIG. 1A, the secondary phosphor member 2 is attached to the upper surface of the primary phosphor member 1 by interposing the same silicone resin as the inner layer and the same material resin as the adhesive. A light emitting device was obtained. Evaluation will be described later.

Comparative Example 1
A light emitting device shown in FIG. 8A was manufactured as a conventional light emitting device, and the performance was evaluated as Comparative Example 1 in the same manner as in Example 1.
[Specification specifications]
The same housing, near-ultraviolet LED, and phosphor as those in Example 1 were used.
Near-ultraviolet LEDs were mounted on the wiring pattern in the housing via a conductive adhesive (Ag paste).
The blue phosphor, red phosphor, and green phosphor used in Example 1 above were added to the liquid silicone resin before curing, and the mixture was stirred and dispersed uniformly.
Using a dispenser, the silicone resin containing the three types of phosphors is filled in a housing, covered with a near-ultraviolet LED, and cured by heating at 150 ° C. for 10 minutes, whereby the light emitting device of Comparative Example 1 is obtained. Obtained.

[Evaluation]
Eleven light emitting devices of Example 1 and Comparative Example 1 were produced, and the variations in color temperature of the output light were evaluated.
Table 1 shows the measurement results of the color temperature of the output light for each sample.

As is clear from Table 1, the color temperature variation in the light emitting device of Comparative Example 1 was ± 300 [K], but the color temperature variation in the light emitting device of Example 1 was ± 50 [K]. .
That is, the light-emitting device of the present invention is arranged as a separate member so that the primary phosphor member and the secondary phosphor member exist separately in different spatial regions, so that It was found that the intensity ratio of each major wavelength component contained in the output light can be further stabilized, and the variation in the color temperature of the output light can be effectively suppressed.

Example 2
In this embodiment, in the structure shown in FIG. 1A, a primary phosphor member including a blue phosphor, a red phosphor, and a green phosphor, and a secondary phosphor member including a yellow phosphor, A light-emitting device that outputs white light with excellent color characteristics and color rendering is actually manufactured.
Other than the blue phosphor, red phosphor, and green phosphor dispersed in the silicone resin as the primary phosphor member, and the yellow phosphor dispersed in the silicone resin as the secondary phosphor member In the case, each material, the configuration of each part, the manufacturing process, etc., such as the housing, near-ultraviolet LED, blue phosphor, red phosphor, and green phosphor, are all the same as in the first embodiment. The yellow phosphor is [Y ₃ Al ₅ O ₁₂ : Ce].
Evaluation will be described later.

Comparative Example 2
A light emitting device shown in FIG. 8A was manufactured as a conventional light emitting device for Example 2, and the performance of the light emitting device was evaluated.
The same housing, near-ultraviolet LED, and phosphor as those in Example 1 were used.
Near-ultraviolet LEDs were mounted on the wiring pattern in the housing via a conductive adhesive (Ag paste).
The liquid silicone resin before curing contains the blue phosphor, red phosphor, and green phosphor used in Example 1 above, and the yellow phosphor used in Example 2 above, and is stirred and dispersed uniformly. It was.
Using a dispenser, the silicone resin containing the four types of phosphors is filled in a housing, covered with a near-ultraviolet LED, and cured by heating at 150 ° C. for 10 minutes, whereby the light emitting device of Comparative Example 2 is obtained. Obtained.

[Evaluation]
Eleven light-emitting devices of Example 2 and Comparative Example 2 were produced, and the variations in color temperature of the output light were evaluated.
Table 2 shows the measurement results of the color temperature of the output light for each sample.

As is clear from Table 2 above, the variation in color temperature in the light emitting device of Comparative Example 2 was ± 500 [K], but the variation in color temperature in the light emitting device of Example 2 was ± 100 [K]. .
In Comparative Example 2, the dispersion state of the blue phosphor, the green phosphor, the red phosphor, and the yellow phosphor (excited and emitted by the fluorescence of the blue phosphor) in the silicone resin causes the light emitted from the light emitting device to be output. The intensity ratio of each included main wavelength component becomes unstable, and the color temperature varies. That is, the blue phosphor, the green phosphor, and the red phosphor are excited by light from the near-ultraviolet LED and output fluorescence. On the other hand, the yellow phosphor is excited by fluorescence from the blue phosphor dispersed inside the silicone resin and outputs fluorescence. For this reason, it is considered that the light output of the blue phosphor and the yellow phosphor varies greatly depending on the dispersion state and arrangement state of the blue phosphor and the yellow phosphor in the silicone resin, and as a result, the light intensity varies.
On the other hand, in the light emitting device of Example 2, the emission intensity of the green phosphor and the red phosphor, which are excited by the fluorescence of the blue phosphor in the primary phosphor member, is small, and therefore output from the primary phosphor member. The emission intensity of the blue phosphor is stable. As a result, blue fluorescence with stable emission intensity can be input to the secondary phosphor member, so that the light output of the yellow phosphor excited by the blue fluorescence is also stable. That is, in the light emitting device of Example 2, since the blue phosphor and the yellow phosphor are arranged as separate members so as to exist separately in different spatial regions, the primary phosphor member The intensity of the output blue fluorescence can be stabilized, and the emission output of the yellow phosphor excited by the blue fluorescence can also be stabilized. Therefore, it is considered that the intensity ratio for each main wavelength component contained in the output light of the light emitting device can be further stabilized, and variation in the color temperature of the output light can be effectively suppressed.
Furthermore, as a result of measuring the average color rendering index Ra for the color rendering properties of the light emitting device of Example 2, it was confirmed that Ra was 90 or more.
From the above results, it was found that the light-emitting device of the present invention is a light-emitting device that is more stable in color temperature variation of output light and has excellent color rendering properties that is optimal as a lighting device or a medical light source. .

Example 3
In Example 2 above, instead of forming the phosphor member in which the yellow phosphor was dispersed as a film, the layer containing the yellow phosphor was formed as a pattern in which a large number of fine dot-like regions were dispersed by the inkjet printing method. (Detailed pattern formation process itself is as described in, for example, Japanese Patent Application Laid-Open No. 2004-80058).
When the distribution density of the dot-like regions was changed by changing the pattern of inkjet printing, the color temperature of the light output from the obtained light emitting device changed in the range of 5500K to 6500K.
This is because the ratio between the primary fluorescence and the secondary fluorescence included in the output light is changed by changing the distribution of the yellow phosphor.
Thus, it has been found that the color tone of the output light can be easily controlled by changing the dot distribution density as a change in the printing pattern.

  With the configuration of the light emitting device according to the present invention, it is possible to further stabilize the intensity ratio of each major wavelength component included in the output light for each product even though the phosphor is arranged to perform cascade excitation. became.

It is a figure which shows typically the structure of the light-emitting device by this invention. It is a schematic diagram which shows an example of the element structure of the GaN-type light emitting element used in order to comprise the light-emitting device by this invention. It is a figure which shows the other structural example of the light-emitting device by this invention, Comprising: Another structural example at the time of arrange | positioning a primary fluorescent material member and a secondary fluorescent material member with respect to the stem by which GaN-type LED was mounted is typical. Is shown. It is a figure which shows the other structural example of the light-emitting device by this invention. It is a figure which shows the other structural example of the light-emitting device by this invention. It is a perspective view when the aspect of Fig.4 (a) is seen from upper direction, Comprising: The state which the secondary fluorescent member is arrange | positioned as the subdivided pattern on the surface of the plate-shaped primary fluorescent member is shown Yes. It is a graph which shows the spectrum of the white light produced using the red fluorescent substance, the green fluorescent substance, the blue fluorescent substance, and the yellow fluorescent substance as one structural example of the light-emitting device by this invention. It is a figure which shows typically the structure of the conventional light-emitting device, especially the light-emitting device which is performing cascade excitation.

Explanation of symbols

S Nitride semiconductor light emitting element L Excitation light 1 Primary phosphor member 10 Primary phosphor L1 Primary fluorescence 2 Secondary phosphor member 20 Secondary phosphor L2 Secondary fluorescence

Claims (12)

A light-emitting device that includes a nitride semiconductor light-emitting element that emits original excitation light, a primary phosphor member, and a secondary phosphor member,
The primary phosphor member includes a primary phosphor that emits primary fluorescence when excited by the original excitation light, and the secondary phosphor member includes a secondary phosphor that emits secondary fluorescence when excited by the primary fluorescence. And
The primary phosphor member is arranged so that the primary excitation light can be irradiated to the primary phosphor, the secondary phosphor member is arranged so that the primary fluorescence can be irradiated to the secondary phosphor, and
The primary phosphor member and the secondary phosphor member are arranged as separate members so that the primary phosphor and the secondary phosphor are separated and exist independently in different spatial regions without being mixed with each other. A light-emitting device,   The light-emitting device according to claim 1, wherein the light-emitting device is configured such that the original excitation light does not reach the secondary phosphor, or has a property that the secondary phosphor is not excited by the original excitation light. The light-emitting device according to claim 2, configured so that the original excitation light does not reach the secondary phosphor, and the configuration is the following configuration (a) and / or (b):
(A) A configuration in which the amount of primary phosphor contained in the primary phosphor member is selected so that substantially all of the original excitation light irradiated to the primary phosphor member is converted into primary fluorescence.
(B) A configuration in which a filter is provided that prevents the secondary phosphor member from being irradiated with the original excitation light.   The light-emitting device according to claim 1, wherein the secondary phosphor member is arranged as a subdivided pattern on the surface of the primary phosphor member.   The light-emitting device according to any one of claims 1 to 3, wherein the secondary phosphor member is arranged as a subdivided pattern on the irradiated surface of the substrate arranged at a position where the primary fluorescence can be irradiated.   A configuration in which a part of the primary fluorescence is output as it is together with the secondary fluorescence so that the primary fluorescence is blue light, the secondary fluorescence includes at least yellow light, and the output light becomes white light. The light-emitting device according to claim 1, wherein the intensity of each of these fluorescences is adjusted. The phosphor emitting blue light is [(M, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu] (M is at least one of Ca, Sr and Ba) or [BaMgAl ₁₀ O ₁₇ : Eu]. ,
The light-emitting device according to claim 6, wherein the phosphor emitting yellow light is [(Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce, SrAl ₂ O ₄ : Eu].   Each of these fluorescences is such that the primary fluorescence and / or the secondary fluorescence further includes green light and red light, and the output light is white light including blue light, yellow light, green light, and red light. The light emitting device according to claim 7, wherein the intensity of the light emitting device is adjusted.   A part of the primary fluorescence is output as it is together with the secondary fluorescence. The primary fluorescence is blue light, the secondary fluorescence includes at least green light and red light, and the output light is white light. The light-emitting device according to claim 1, wherein the intensity of each of these fluorescences is adjusted so that The phosphor emitting blue light contains [(M, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu] (M is at least one of Ca, Sr and Ba) or [BaMgAl ₁₀ O ₁₇ : Eu]. ,
The phosphor emitting green light is [BaMgAl ₁₀ O ₁₇ : Eu, Mn], [ZnS: Cu, Al] or [MGa ₂ S ₄ : Eu] (M is at least one of Ca, Sr, and Ba). Including
A phosphor emitting red light is [REuW ₂ O ₈ ] (R is at least one of Li, Na, K, Rb, and Cs), [M ₂ Si ₅ N ₈ : Eu] (M is Ca, Sr, At least one of Ba), [(Ca, Sr) S: Eu], [3.5MgO.0.5MgF ₂ .GeO ₂ : Mn] or [La ₂ O ₂ S: Eu],
The light emitting device according to claim 8 or 9. The light emitting device according to claim 8 or 9, wherein the phosphor emitting green light is [BaMgAl ₁₀ O ₁₇ : Eu, Mn].   The light-emitting device according to claim 1, wherein the original excitation light is light having a wavelength belonging to a wavelength range of 360 nm to 480 nm.

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