JP2017011098A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting device that can suppress occurrence of fluctuation of chromaticity even when ambient temperature varies.SOLUTION: A light emitting device includes a light emitting element and a first phosphor that absorbs at least a part of light from the light emitting element and emits light having a different wavelength. In the light emitting element, the peak wavelength of a light emission spectrum of the light emitting element is shifted to a longer wavelength side as ambient temperature rises. The peak wavelength of the light emission spectrum of the light emitting element is on a shorter wavelength side than the peak wavelength of an excitation spectrum of the first phosphor. In a wavelength variation range occurring when the ambient temperature of the light emitting element varies, the excitation efficiency of the first phosphor on a long wavelength side of the wavelength variation range is higher than that on a short wavelength side.SELECTED DRAWING: None

Description

  The present disclosure relates to a light emitting device.

  Research and development is underway to create white light sources for lighting and backlight units using light emitting elements. Examples of a method for producing a white light source using a light emitting element include a method using a phosphor and a method using a plurality of light emitting elements that emit monochromatic light. In the method using a phosphor, white is produced using a light emitting element that emits blue light and a phosphor that absorbs light from the light emitting element and converts the wavelength to emit yellow light. As the phosphor, an yttrium / aluminum / garnet phosphor (hereinafter referred to as “YAG phosphor”) is known (for example, see Patent Document 1).

JP 2004-119743 A

  However, when the white light source device using the phosphor is used as an illumination light source that continuously emits strong light, the temperature of the white light source device rises due to heat generation of the light emitting element, and the brightness of the white light source device increases. Problems such as change, color shift, and change in color temperature have occurred. Here, the color misregistration means that the chromaticity of the light emitted on the chromaticity diagram is observed at a position deviated from the desired chromaticity.

  Therefore, an object of the present embodiment is to provide a light emitting device that can suppress the occurrence of chromaticity deviation even when the ambient temperature changes.

  The light emitting device according to the present embodiment includes a light emitting element and a first phosphor that absorbs at least a part of light from the light emitting element and emits light having a different wavelength. As the temperature rises, the peak wavelength of the emission spectrum of the light-emitting element is shifted to the longer wavelength side, and the peak wavelength of the emission spectrum of the light-emitting element is excited by the first phosphor. In the range of wavelength change that occurs when the ambient temperature of the light emitting element is changed, which is on the shorter wavelength side than the peak wavelength of the spectrum, the first phosphor is configured such that the longer wavelength side of the wavelength change range is shorter than the shorter wavelength side. The excitation efficiency of is high.

  Thus, a light emitting device with little chromaticity deviation can be provided when the ambient temperature changes.

(A) is sectional drawing which shows typically the structure of the light-emitting device which concerns on embodiment, (b) is an expanded partial sectional view which expands and shows a part of (a). It is a graph which shows the excitation spectrum of a YAG type fluorescent substance. It is a graph which shows the excitation spectrum of a LAG type fluorescent substance. It is a graph which shows the excitation spectrum of a KFS type | system | group fluorescent substance. 3 is a graph showing an excitation spectrum of a YAG phosphor used in Example 1. FIG. 6 is a graph showing a chromaticity change on the chromaticity diagram when the ambient temperature changes in the light emitting device of Example 1.

  Embodiments will be described below with reference to the drawings. However, the embodiment described below exemplifies a light emitting device for embodying the technical idea of the present invention, and the present invention does not limit the light emitting device to the following. Moreover, although the size and positional relationship of the members shown in each drawing are exaggerated for clarity of explanation, they correspond to the facts.

The light-emitting device according to the embodiment includes a light-emitting element and a first phosphor that absorbs at least part of light from the light-emitting element and emits light of different wavelengths. In the light emitting element, the peak wavelength of the emission spectrum of the light emitting element is shifted to the longer wavelength side as the ambient temperature rises. The peak wavelength of the emission spectrum of the light emitting element is on the shorter wavelength side than the peak wavelength of the excitation spectrum of the first phosphor. In the range of wavelength change that occurs when the ambient temperature of the light emitting element changes, the excitation efficiency of the first phosphor is higher on the long wavelength side of the wavelength change range than on the short wavelength side.
As the peak wavelength of the emission spectrum of the light emitting element, one that changes by 5 to 20 nm as the ambient temperature increases from 25 ° C. to 150 ° C. can be used.
As the first phosphor, one containing Y and Al and containing an yttrium-aluminum-garnet phosphor activated with at least one element selected from rare earth elements can be used.
The first phosphor further includes at least one element selected from Lu, Sc, La, Gd, Tb, Eu, and Sm and one element selected from Ga and In. be able to.
What is Ce (provided that 0 <z ≦ 1,0 <x ≦ 1): the first _{phosphor, (Y z Gd 1-z} ) 3 (Al x Ga 1-x) 5 O 12 Can be used.
The first phosphor can be covered with a second phosphor.
It is preferable that the moving distance on the chromaticity diagram generated when the ambient temperature is changed from 25 ° C. to 150 ° C. is 0.02 or less.
It is preferable that a color temperature change amount generated when the ambient temperature is changed from 25 ° C. to 150 ° C. is 600 or less.
The 150 ° C. luminous intensity generated when the ambient temperature changes from 25 ° C. to 150 ° C. is preferably greater than 0.67 in terms of relative luminous intensity with respect to 25 ° C.
In the light emitting device according to this embodiment, the first phosphor has a short wavelength on the long wavelength side in the range of wavelength change that occurs in the light emitting element when the ambient temperature of the light emitting element changes due to heat generation of the light emitting element, for example. The excitation efficiency is higher than the wavelength side, and the decrease in excitation efficiency due to the increase in ambient temperature is caused by the increase in excitation efficiency caused by the longer peak wavelength corresponding to the increase in ambient temperature of the peak wavelength of the light emitting element. It becomes possible to cancel.
Therefore, it is possible to provide a light-emitting device that can suppress the decrease in the luminous flux [lm] and the occurrence of chromaticity deviation even when the ambient temperature changes, and can suppress the change in color temperature.
The light emitting device according to the embodiment includes a light emitting element and a first phosphor that absorbs at least a part of light from the light emitting element and emits light of different wavelengths.
FIG. 1 is a cross-sectional view schematically showing the configuration of the light emitting device according to the embodiment.
The lead type (bullet type) light emitting device 100 includes a mount lead 105, an inner lead 106, and a mold member 104. The light emitting element 102 is placed in the cup portion of the mount lead 105. The coating part 101 including the phosphor 107 is filled in the cup part so as to cover the light emitting element 102. Further, the cup portion of the mount lead 105, the light emitting element 102, and the coating portion 101 are resin-molded by a molding member 104. Here, the pair of electrodes of the light emitting element 102 is connected to the mount lead 105 and the inner lead 106 using the wire 103.

  In the light emitting device 100, part of the light emitted by the light emitting element 102 excites the phosphor 107, and other light is emitted from the coating unit 101 to the outside without being absorbed by the phosphor 107. The phosphor 107 excited by the light from the light emitting element 102 emits light having a wavelength different from that of the light from the light emitting element. The light emitted from the phosphor 107 and the light from the light emitting element 102 emitted without contributing to the excitation of the phosphor 107 are mixed to emit mixed color light from the light emitting device 100. Based on the emission color of the light emitting element 102 and the fluorescent color of the phosphor 107, the amount of the phosphor 107 is set so that the mixed color light of the light emitting device 100 becomes a desired color.

  Here, the content of the phosphor 107 to be included in the coating unit 101 is light of a desired emission color at a room temperature at which the light emitting device 100 is considered to be used most frequently, for example, at a temperature of 25 ° C. Is set to emit. However, in general, the excitation efficiency of the phosphor 107 decreases as the ambient temperature rises. Therefore, when the ambient temperature rises due to the heat generation of the light-emitting element 102 and / or the change in the environmental temperature, the light emitted from the phosphor 107 does not emit light. The output is also reduced. Therefore, when the ambient temperature changes, the color mixture ratio of the fluorescence of the phosphor 107 and the light of the light emitting element 102 changes, resulting in a color shift. Further, the peak wavelength of the emission spectrum of the light emitting element 102 changes due to a change in ambient temperature caused by its own heat generation or a change in environmental temperature. For example, the light emitting element 102 generally shifts the peak wavelength of the emission spectrum to the longer wavelength side when the ambient temperature rises. Further, the excitation spectrum of the phosphor 107 also has wavelength dependency.

Therefore, the light emitting device 100 according to the present embodiment is configured as follows in consideration of the above.
(1) As the light emitting element 102, as the ambient temperature rises, the peak wavelength of the emission spectrum of the light emitting element 102 shifts to the longer wavelength side.
(2) As the phosphor 107, a phosphor having a higher excitation efficiency on the long wavelength side than on the short wavelength side is used in a range where the wavelength generated when the ambient temperature of the light emitting element 102 changes.
(3) The peak wavelength of the emission spectrum of the light emitting element 102 is set to be shorter than the peak wavelength of the excitation spectrum of the phosphor 107. At this time, preferably, even when the ambient temperature of the light emitting element 102 is the highest, the peak wavelength of the emission spectrum of the light emitting element 102 is located on the shorter wavelength side than the peak wavelength of the excitation spectrum of the phosphor 107. Preferably it is.

With the above configuration, even if the ambient temperature of the light emitting element 102 changes, the excitation efficiency decreases as the ambient temperature rises, and the excitation efficiency of the phosphor 107 is increased by increasing the peak wavelength of the light emitting element 102. It can be countered by the increase. When the light emission intensity of the light emitting element 102 tends to decrease due to a change in the ambient temperature of the light emitting element 102, the rate of decrease in the light emission intensity accompanying the increase in the ambient temperature of the light emitting element 102 and the increase in the ambient temperature of the phosphor 107 It is preferable to compensate for the decrease in excitation efficiency due to the increase in the excitation efficiency of the phosphor 107 by increasing the peak wavelength of the light emitting element 102. That is, the rate of increase in the excitation efficiency of the phosphor 107 due to the longer wavelength of the excitation wavelength varies depending on the wavelength, so the rate of decrease in emission intensity associated with the increase in ambient temperature of the light emitting element 102 and excitation associated with the increase in ambient temperature of the phosphor 107. The peak wavelength of the light emitting element 102 may be set at a position that compensates for the decrease in efficiency.
For example, when the rate of decrease in emission intensity associated with the increase in ambient temperature of the light emitting element 102 and the decrease in excitation efficiency associated with the increase in ambient temperature of the phosphor 107 are large, the excitation wavelength of the excitation efficiency of the phosphor 107 is increased. The peak wavelength of the light emitting element 102 is set at a position where the increase rate associated with is large.

  Hereinafter, each configuration of the embodiment will be described in detail.

[Phosphor 107]
(Yttrium / Aluminum / Garnet phosphor)
The phosphor used in the present embodiment is, for example, a YAG-based phosphor activated with Ce, and YAlO ₃ : Ce, Y ₃ Al ₅ O ₁₂ Y: Ce (YAG: Ce) and Y ₄ Al ₂ O. ₉ : Ce, and a mixture thereof. This YAG phosphor emits light when excited by visible light or ultraviolet light emitted from the light emitting element 102. In the present specification, the YAG-based phosphor is not only a phosphor having the above-described composition, but also at least one element selected from the group consisting of Lu, Sc, La, Gd, and Sm, as a part or all of yttrium. Or a part or all of aluminum is used in a broad sense including a phosphor having a fluorescent action in which any one or both of Ba, Tl, Ga, and In are substituted. More specifically, the general formula _{(Y z Gd 1-z)} 3 Al 5 O 12: Ce ( where, 0 <z ≦ 1) photoluminescence phosphor and the general formula represented by _{(Re 1-a Sm a)} 3 Re ' ₅ O ₁₂ : Ce (where 0 ≦ a <1, 0 ≦ b ≦ 1, Re is at least one selected from Y, Gd, La, and Sc, and Re ′ is Al, Ga, Ba, Tl, and At least one selected from In.).
In the present embodiment, preferably, at least one first selection element containing Y and Al and selected from Lu, Sc, La, Gd, Tb, Eu and Sm, and one selected from Ga and In is used. A YAG phosphor containing a second selective element and activated with cerium is used.
In this YAG phosphor, the excitation spectrum of the excitation spectrum and the peak wavelength of the excitation spectrum can be variously set in a relatively wide range depending on the types and contents of the first selection element and the second selection element.
In this embodiment, in addition to Ce, an yttrium-aluminum oxide phosphor activated with Pr can also be used. In addition, the YAG phosphor may contain at least one of Ba, Sr, Mg, Ca, and Zn, and by further containing Si, the crystal growth reaction is suppressed and the phosphor particles are aligned. You can also

  The yttrium / aluminum oxide-based phosphor activated with cerium used in the present embodiment is resistant to heat, light and moisture due to its garnet structure. The YAG phosphor capable of emitting green light, which is an yttrium / aluminum oxide phosphor activated by cerium, has an excitation absorption spectrum depending on the types and contents of the first selection element and the second selection element. Can be set in the vicinity of 420 nm to 470 nm. In addition, the YAG phosphor capable of emitting green light has a broad emission spectrum that has a light emission peak wavelength λp near 530 nm and extends to the vicinity of 700 nm. On the other hand, a YAG phosphor capable of emitting yellow light, which is an yttrium / aluminum oxide phosphor activated with cerium, has an excitation absorption spectrum depending on the types and contents of the first and second selective elements. Can be set in the vicinity of 420 nm to 470 nm. Further, the YAG phosphor capable of emitting yellow light has a broad emission spectrum with an emission peak wavelength λp in the vicinity of 560 nm and extending to the vicinity of 750 nm.

  Of the composition of YAG phosphors with a garnet structure, the emission spectrum is shifted to the short wavelength side by substituting part of Al with Ga, and part of Y of the composition is replaced with Gd and / or La. By doing so, the emission spectrum shifts to the long wavelength side. Such a YAG-based phosphor can also be obtained, for example, by firing a raw material adjusted so as to add an excess of substitutional elements relative to the stoichiometric ratio. If the substitution of Y is less than 20%, the green component is large and the red component is small. On the other hand, at 80% or more, although the reddish component increases, the luminance rapidly decreases. Similarly, the excitation absorption spectrum is shifted to the short wavelength side by substituting part of Al with Ga in the composition of the YAG phosphor having a garnet structure. By substituting a part of Gd and / or La, the excitation absorption spectrum is shifted to the longer wavelength side.

Such YAG-based phosphors use oxides or compounds that easily become oxides at high temperatures as raw materials such as Y, Gd, Ce, La, Al, Sm, and Ga. Mix thoroughly to obtain the raw material. Alternatively, a coprecipitated oxide obtained by co-precipitation of a solution obtained by coprecipitation of a solution obtained by dissolving a rare earth element of Y, Gd, Ce, La, and Sm in an acid at a stoichiometric ratio with oxalic acid, and aluminum oxide or gallium oxide. To obtain a mixed raw material. An appropriate amount of fluoride such as ammonium fluoride or NH ₄ Cl is mixed as a flux into this crucible and packed in a crucible, and baked in the temperature range of 1350 to 1450 ° C. for 2 to 5 hours to obtain a baked product. The fired product can be obtained by ball milling in water, washing, separating, drying, and finally passing through a sieve. The firing step includes a first firing step performed in the atmosphere or a weak reducing atmosphere, and a second firing step performed in a reducing atmosphere, a mixture consisting of a mixed raw material and a flux mixed with phosphor raw materials, Baking in two stages is preferred. Here, the weak reducing atmosphere refers to a weak reducing atmosphere set to include at least the amount of oxygen necessary in the reaction process of forming a desired phosphor from the mixed raw material. By performing the first firing step until the formation of the phosphor structure is completed, blackening of the phosphor can be prevented and a decrease in light absorption efficiency can be prevented. In addition, the reducing atmosphere in the second firing step refers to a reducing atmosphere stronger than the weak reducing atmosphere. By firing in two stages in this way, a phosphor with high absorption efficiency at the excitation wavelength can be obtained. Therefore, when a light emitting device is formed with the phosphor thus formed, the amount of the phosphor necessary for obtaining a desired color tone can be reduced, and a light emitting device with high light extraction efficiency can be formed. Can do.

  In the present embodiment, for example, a YAG phosphor having the following composition can be used.

(Y _0.90 Gd _0.10 ) _2.85 Ce _0.15 Al ₅ O ₁₂ , (Y _0.395 Gd _0.605 ) _2.85 Ce _0.15 Al ₅ O ₁₂ , Y _2.965 Ce _0.035 (Al _0.8 Ga _0.2 ) ₅ O ₁₂ , (Y _0.8 , Gd _0.2 ) _2.965 Ce _0.035 Al ₅ O ₁₂ , Y _2.965 Ce _0.035 (Al _0.5 , Ga _0.5 ) ₅ O ₁₂ , Y _2.85 Ce _0.15 Al ₅ O _12, La _2.96 Ce _0.04 Al ₅ O ₁₂ , (Y _0.8 , Lu _0.2 ) _2.93 Ce _0.07 Al ₅ O ₁₂

  In the present embodiment, yttrium / aluminum oxide phosphors activated by two or more kinds of cerium having different compositions may be used. When using yttrium / aluminum oxide phosphors activated with two or more kinds of cerium, they may be used in combination, for example, separated into a first layer and a second layer, respectively. You may arrange. When the phosphors are arranged independently, it is preferable to arrange the phosphors in the order of the phosphor that easily absorbs and emits light from the light emitting element on the shorter wavelength side and the phosphor that easily absorbs and emits light on the longer wavelength side. This makes it possible to efficiently absorb and emit light.

  In the present embodiment, for example, a nitride-based phosphor that absorbs part of blue light emitted by the light-emitting element and emits light in the yellow to red region can be used together with the YAG-based phosphor. When the nitride-based phosphor is used together with the YAG-based phosphor, it is possible to provide a light-emitting device that emits a warm white light in which yellow to red light is further added by the nitride-based phosphor.

  That is, the yttrium / aluminum oxide phosphor activated by cerium absorbs part of the blue light emitted by the light emitting element 102 and emits light in the yellow region. Here, the emission color due to the color mixture of the blue light emitted by the light emitting element 102 and the yellow light of the yttrium aluminum oxide fluorescent material is pale white. Therefore, this yttrium aluminum oxide phosphor and a phosphor emitting red light (for example, a nitride phosphor) are mixed together in a coating member 101 having translucency, and blue light emitted by the light emitting element 102 is mixed. By combining with light, a light emitting device that emits white mixed light can be provided. Particularly preferred is a white light emitting device whose chromaticity is located on the locus of black body radiation in the chromaticity diagram. However, in order to provide a light emitting device having a desired color temperature, the amount of phosphor of the yttrium / aluminum oxide phosphor and the amount of phosphor of red light emission can be appropriately changed. This light-emitting device that emits white-based mixed color light improves the special color rendering index R9. A conventional light emitting device that emits white light only with a combination of a blue light emitting element and a yttrium aluminum oxide phosphor activated by cerium has a special color rendering index R9 of nearly 0 at a color temperature of Tcp = 4600K, The red component was insufficient. Therefore, increasing the special color rendering index R9 has been a problem to be solved. In this embodiment, a special color rendering evaluation is performed in the vicinity of the color temperature Tcp = 4600K by using a phosphor emitting red light together with an yttrium aluminum oxide phosphor. The number R9 can be increased to around 40.

(Nitride phosphor)
The nitride-based phosphor contains N and is selected from at least one element selected from Be, Mg, Ca, Sr, Ba, and Zn, and C, Si, Ge, Sn, Ti, Zr, and Hf A phosphor activated with at least one element selected from rare earth elements and emitted from visible light, ultraviolet light, and YAG phosphors Is excited to absorb light and emits light. The basic constituent element of the nitride-based phosphor is represented by the general formula L _X Si _Y N _{(2 / 3X + 4 / 3Y)} : Eu or L _X Si _Y O _Z N _{(2 / 3X + 4 / 3Y-2 / 3Z)} : Eu (L Is any one of Sr, Ca, Sr and Ca. 0.5 ≦ X ≦ 3 and 1.5 ≦ Y ≦ 8. In the general formula, X and Y are preferably X = 2, Y = 5, or X = 1, Y = 7, but any can be used. The general formula LAlSiN ₃ : Eu can also be used.

  L is any one of Sr, Ca, Sr and Ca. The mixing ratio of Sr and Ca can be changed as desired.

  By using Si for the composition of the phosphor, it is possible to provide an inexpensive phosphor with good crystallinity.

Europium Eu, which is a rare earth element, is used for the emission center. Europium mainly has bivalent and trivalent energy levels. The phosphor according to the present embodiment uses Eu ²⁺ as an activator with respect to the base alkaline earth metal silicon nitride. Eu ²⁺ is easily oxidized and is commercially available with a trivalent Eu ₂ O ₃ composition. However, in commercially available Eu ₂ O ₃ , O is greatly involved and it is difficult to obtain a good phosphor. Therefore, it is preferable to use a material obtained by removing O from Eu ₂ O ₃ out of the system. For example, it is preferable to use europium alone or europium nitride. However, this is not the case when Mn is added.

Mn as an additive promotes diffusion of Eu ²⁺ and improves luminous efficiency such as luminous luminance, energy efficiency, and quantum efficiency. Mn is contained in the raw material, or Mn alone or a Mn compound is contained in the manufacturing process and fired together with the raw material. However, Mn is not contained in the basic constituent elements after firing, or even if contained, only a small amount remains compared to the initial content. This is probably because Mn was scattered in the firing step.

  The phosphor has at least one selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, O and Ni in the basic constituent element or together with the basic constituent element. Contains the above. These elements have actions such as increasing the particle diameter and increasing the luminance of light emission. Further, B, Al, Mg, Cr and Ni have an effect that afterglow can be suppressed.

  Such a nitride-based phosphor absorbs part of the blue light emitted by the light emitting element 102 and emits light in the yellow to red region. Using the nitride phosphor together with the YAG phosphor in the light emitting device having the above-described configuration, the blue light emitted from the light emitting element 102 and the yellow to red light by the nitride phosphor are mixed to produce a warm color system. Provided is a light emitting device that emits white light.

  The light emitting element preferably has a peak wavelength of an emission spectrum of 350 nm to 530 nm. In particular, 400 nm to 530 nm having a color tone to light from the light emitting element is preferable. More preferably, a wavelength shorter than the excitation peak of the first phosphor of 400 to 450 nm is suitable. With this configuration, it is possible to control the color shift of the entire light emitting device by controlling the color tone change of the semiconductor light emitting element and the color tone change of the phosphor.

  In the present embodiment, a blue light emitting device using a nitride compound semiconductor for the YAG phosphor and the light emitting layer, a blue light emitting device using a nitride compound semiconductor for the YAG phosphor and the nitride phosphor and the light emitting layer, Can be used to provide a light emitting device having an arbitrary color tone such as a light bulb color including white.

  That is, blue light emitted from a light emitting element using a nitride compound semiconductor in the light emitting layer, and green light and red light emitted from a phosphor whose body color is yellow or red to absorb blue light. Alternatively, when yellow light and green light and red light are mixedly displayed, a desired white light emission color display can be performed. In order to cause this color mixture, the light emitting device preferably contains phosphor powder or bulk in various resins such as epoxy resin, acrylic resin or silicone resin, and inorganic materials such as silicon oxide and aluminum oxide. Such phosphors can be used in various ways depending on the application, such as dot-like and layer-like ones that are formed thin enough to transmit light from the light-emitting element. Arbitrary color tones such as a light bulb color including white can be provided by variously adjusting the ratio, coating, and filling amount of the phosphor and the resin, and selecting the emission wavelength of the light emitting element.

As a phosphor that emits reddish light that can be used in this embodiment, in addition to a nitride-based phosphor, the phosphor emits light when excited by light having a wavelength of 400 to 600 nm, for example, Y ₂ O ₂ S: Eu. La ₂ O ₂ S: Eu, CaS: Eu, SrS: Eu, ZnS: Mn, ZnCdS: Ag, Al, ZnCdS: Cu, Al, and the like can also be used. The color rendering property of the light emitting device can be improved by using a phosphor capable of emitting such red light together with the YAG phosphor.

  A mechanism for preventing color misregistration of the light emitting device according to this embodiment will be described using a specific example.

(Selection of phosphor and light emitting element)
Consider a light-emitting device that uses a YAG-based phosphor having a peak wavelength on the long wavelength side of the excitation spectrum of about 457 nm.

In this light emitting device, for example, when a light emitting element having an emission peak wavelength of 457 nm is used at a rated drive of 20 mA with a low input current to the light emitting element, an excitation spectrum of a YAG phosphor (Y _2.85 Ce _0.15 Al ₅ O ₁₂ ) ( Since the peak wavelength in FIG. 2) is 457 nm, the YAG phosphor emits light most efficiently when the light emitting element is turned on, that is, when the ambient temperature is about room temperature. However, as the ambient temperature to the light emitting element rises, the peak wavelength of the emission spectrum of the light emitting element shifts by about 10 nm to the long wavelength side. When the emission peak wavelength shifts to the long wavelength side by about 10 nm, the excitation efficiency of the YAG phosphor decreases, so the relative emission intensity of the YAG phosphor decreases. That is, the ratio of the emission intensity of the converted light to the excitation light is relatively lowered. Further, in the light emitting device of the comparative example, the color misregistration is further increased by increasing the luminous blue component accompanying the long wave shift of the light emission peak wavelength of the light emitting element. For this reason, the light emitting device of this comparative example causes a color shift due to an increase in the ambient temperature of the light emitting element.

On the other hand, in the light emitting device according to the present embodiment in which the light emitting element having the emission peak wavelength of 445 nm is selected with respect to the phosphor having the peak wavelength of the excitation spectrum of the YAG-based phosphor of 457 nm, the light emitting element generates heat. Thus, when the emission peak wavelength of the light emitting element is shifted by a long wave, the excitation efficiency of the YAG phosphor increases and the emission intensity improves. In addition, when the emission peak wavelength of the light emitting element is shifted to a long wave, the luminous blue component increases. However, since the emission intensity of the YAG phosphor is improved to balance the increase in the luminous blue component, the luminous blue component increases and the YAG component increases. The balance of the emission intensity of the phosphor can be maintained, and the color tone deviation can be suppressed. That is, the light emitting device according to the present embodiment suppresses color misregistration due to a change in the emission intensity ratio caused by a decrease in the excitation efficiency of the YAG phosphor when the peak wavelength of the light emitting element shifts to the long wavelength side. In addition, the color shift is suppressed by the balance between the luminous blue component and the increase due to the long wave shift of the emission peak wavelength of the light emitting element and the improvement of the emission intensity of the YAG phosphor. On the other hand, the light emission output of both the light emitting element and the YAG phosphor usually decreases with the heat generation of the light emitting element, but the light emission output of the light emitting element decreases and the phosphor decreases even if the ambient temperature of the light emitting element rises. Therefore, the color tone misalignment due to the decrease in the output due to the temperature increase of the light emitting element and the phosphor can be reduced.
Therefore, according to the light emitting device according to the present embodiment, it is possible to provide a light emitting device capable of emitting light with a stable color tone.

  Note that the peak wavelength of the emission spectrum of the light emitting element shifts to the short wavelength side by increasing the input current. However, regarding the shift to the short wavelength side, the shift to the long wavelength side due to the increase in the ambient temperature is more dominant than the shift to the short wavelength side due to the increase in current density. When the temperature rises from 25 ° C. to 150 ° C., there is a shift to the long wavelength side of about 5 to 10 nm.

  In the case where the light emitting device is configured using two types of first phosphor and second phosphor as phosphors, the peak wavelength of the light emitting element is lower than the peak wavelength of the excitation spectrum of each phosphor. Select a light emitting element. As the second phosphor, one that emits light in a longer wavelength region than the first phosphor is used.

  For example, a case where a YAG phosphor is used as the first phosphor and a nitride phosphor is used as the second phosphor will be described. Here, the nitride-based phosphor absorbs not only light from the light-emitting element but also light near the peak wavelength (about 530 nm) of the emission spectrum of the YAG-based phosphor, and is excited.

  As described above, when a current is supplied to the light emitting device, heat is generated in the light emitting element, and when the ambient temperature rises, the peak wavelength of the light emitting element shifts to the long wavelength side, and the first phosphor emits light. Strength increases. By these interactions, the color tone and the light emission output can be maintained with almost no change in the relationship between the light emitting element and the first phosphor. The second phosphor also prevents a decrease in light output due to the relationship between the excitation spectrum of the second phosphor and the shift of the light emitting element to the longer wavelength side, and the increase in the intensity of excitation light due to the increase in the emission intensity of the first phosphor. it can. Therefore, even in the relationship between the second phosphor, the first phosphor, and the light emitting element, the color tone and the light output can be maintained with almost no change.

  Note that a phosphor whose excitation spectrum hardly changes within a range in which the light emitting element shifts to the short wavelength side due to an increase in input power can be used as the second phosphor. Even in this case, the effect is shown by the combination with YAG.

  In addition, the position of the excitation spectrum and the peak wavelength of the light emitting element can be adjusted in consideration of the thermal resistance value and heat dissipation characteristics of the light emitting device, the junction temperature of the light emitting element, and the like.

  The relationship between the color name and the chromaticity coordinates in the specification is based on the JIS standard (JIS Z8110).

  The particle size is F. S. S. S. No. (Fisher Sub Sieve Sizer's No.) Value by air permeation method.

[Light emitting element 102]
The light emitting element used in this embodiment is the light emitting element 102. When a light emitting device that emits light having a wavelength converted by exciting a phosphor by combining the phosphor and the light emitting element, a light emitting element that emits light having a wavelength that can excite the phosphor is used. In the light emitting element 102, a semiconductor such as GaAs, InP, GaAlAs, InGaAlP, InN, AlN, GaN, InGaN, AlGaN, or InGaAlN is formed as a light emitting layer on a substrate by MOCVD or the like. Examples of the semiconductor structure include a homostructure having a MIS junction, a PIN junction, a PN junction, etc., a heterostructure, or a double heterostructure. Various emission wavelengths can be selected depending on the material of the semiconductor layer and the degree of mixed crystal. In addition, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed in a thin film in which a quantum effect is generated can be used. Preferably, a nitride compound semiconductor (general formula In _i Ga _j Al _k N, where 0 ≦ i, 0 ≦ j, 0 ≦ k, capable of efficiently exciting a phosphor and capable of efficiently emitting a relatively short wavelength) i + j + k = 1).

When a gallium nitride compound semiconductor is used, a material such as sapphire, spinel, SiC, Si, ZnO, or GaN is preferably used for the semiconductor substrate. In order to form gallium nitride with good crystallinity, it is more preferable to use a sapphire substrate. When a semiconductor film is grown on a sapphire substrate, it is preferable to form a gallium nitride semiconductor having a PN junction on a buffer layer made of GaN, AlN or the like. Further, a GaN single crystal itself selectively grown on a sapphire substrate using SiO ₂ as a mask can be used as the substrate. In this case, the light emitting element and the sapphire substrate can be separated by etching away SiO ₂ after forming each semiconductor layer. Gallium nitride-based compound semiconductors exhibit N-type conductivity without being doped with impurities. When forming a desired N-type gallium nitride semiconductor such as improving luminous efficiency, Si, Ge, Se, Te, C, etc. are preferably introduced as appropriate as N-type dopants. On the other hand, when a P-type gallium nitride semiconductor is formed, a P-type dopant such as Zn, Mg, Be, Ca, Sr, or Ba is doped.

  Since a gallium nitride compound semiconductor is difficult to become P-type only by doping with a P-type dopant, it is preferable to make it P-type by annealing with a furnace, low-energy electron beam irradiation, plasma irradiation or the like after introduction of the P-type dopant. . Specific examples of the layer structure of the light-emitting element include an N-type contact layer, which is a gallium nitride semiconductor, and an aluminum nitride / gallium semiconductor on a sapphire substrate or silicon carbide having a buffer layer in which gallium nitride, aluminum nitride, or the like is formed at a low temperature. An N-type cladding layer, an active layer that is an indium gallium nitride semiconductor doped with Zn and Si, a P-type cladding layer that is an aluminum nitride-gallium semiconductor, and a P-type contact layer that is a gallium nitride semiconductor Are preferable. In order to form the light emitting element 102, in the case of the light emitting element 102 having a sapphire substrate, an exposed surface of a P-type semiconductor and an N-type semiconductor is formed by etching or the like, and then a sputtering method or a vacuum evaporation method is performed on the semiconductor layer. Each electrode is formed in a desired shape. In the case of a SiC substrate, a pair of electrodes can be formed using the conductivity of the substrate itself.

  Next, the formed semiconductor wafer or the like is directly fully cut by a dicing saw with a blade having a diamond cutting edge, or a groove having a width wider than the cutting edge width is cut (half cut), and then the semiconductor is applied by an external force. Break the wafer. Alternatively, after a very thin scribe line (meridian) is drawn on the semiconductor wafer by, for example, a grid shape by a scriber in which the diamond needle at the tip moves reciprocally linearly, the wafer is divided by an external force and cut into chips. In this manner, the light emitting element 102 which is a nitride compound semiconductor can be formed.

  In the light emitting device according to this embodiment that emits light by exciting the phosphor, the main emission wavelength of the light emitting element 102 is preferably 350 nm or more and 530 nm or less in consideration of the complementary color with the phosphor and the like.

[Conductive wire 103]
The conductive wire 103 is required to have good ohmic properties, mechanical connectivity, electrical conductivity, and thermal conductivity with the electrode of the light emitting element 102. Preferably ^{0.01cal / (s) (cm 2} ) (℃ / cm) or higher as heat conductivity, and more preferably ^{0.5cal / (s) (cm 2} ) (℃ / cm) or more. In consideration of workability and the like, the diameter of the conductive wire is preferably Φ10 μm or more and Φ45 μm or less. In particular, the conductive wire is likely to break at the interface between the coating portion containing the phosphor and the mold member not containing the phosphor. Even if the same material is used, it is considered that wire breakage easily occurs because the substantial amount of thermal expansion differs depending on the phosphor. Therefore, the diameter of the conductive wire is more preferably 25 μm or more, and more preferably 35 μm or less from the viewpoint of light emission area and ease of handling.

  Specific examples of such conductive wires include conductive wires using metals such as gold, copper, platinum, and aluminum, and alloys thereof. Such a conductive wire can easily connect an electrode of each light emitting element to an inner lead, a mount lead, and the like by a wire bonding apparatus.

[Mount lead 105]
As the mount lead 105, the light emitting element 102 is disposed, and it is sufficient that the mount lead 105 has a size sufficient to be stacked by a die bond device or the like. Further, when a plurality of light emitting elements are installed and the mount lead is used as a common electrode of the light emitting elements, sufficient electrical conductivity and connectivity with bonding wires and the like are required. Further, when the light emitting element is arranged in the cup on the mount lead and the phosphor is filled inside, it is possible to prevent the pseudo lighting by the light from another light emitting diode arranged in the vicinity. .

Adhesion between the light emitting element 102 and the cup of the mount lead 105 can be performed by a thermosetting resin or the like. Specifically, an epoxy resin, an acrylic resin, an imide resin, etc. are mentioned. In addition, Ag paste, carbon paste, metal bumps, or the like can be used for bonding and electrical connection to the mount lead by a face-down light emitting element or the like. Further, in order to improve the light utilization efficiency of the light emitting diode, the surface of the mount lead on which the light emitting element is arranged may be a mirror surface, and the surface may have a reflecting function. In this case, the surface roughness is preferably 0.1 S or more and 0.8 S or less. The specific electric resistance of the mount lead is preferably 300 μΩ-cm or less, more preferably 3 μΩ-cm or less. In addition, when a plurality of light emitting elements are stacked on the mount lead, heat generation from the light emitting elements is required to be high, so that thermal conductivity is required. Specifically, more preferably preferably ^{0.01cal / (s) (cm 2} ) (℃ / cm) or more is ^{0.5cal / (s) (cm 2} ) (℃ / cm) or more. Examples of materials that satisfy these conditions include iron, copper, iron-containing copper, tin-containing copper, and ceramic with a metallized pattern.

[Inner lead 106]
The inner lead 106 is intended to be connected to the conductive wire 103 connected to the light emitting element 102 arranged on the mount lead 105. In the case where a plurality of light emitting elements are provided on the mount lead, it is necessary that the conductive wires can be arranged so as not to contact each other. Specifically, as the distance from the mount lead increases, the area of the end surface of the inner lead that is wire-bonded increases to prevent contact of the conductive wire that is connected to the inner lead that is further away from the mount lead. it can. The roughness of the connecting end surface with the conductive wire is preferably 1.6 S or more and 10 S or less in consideration of adhesion. In order to form the tip of the inner lead in various shapes, the shape of the lead frame may be determined in advance by the mold, and it may be punched or formed, or after all the inner leads are formed, the upper part of the inner lead You may form by shaving a part of. Furthermore, after punching and forming the inner lead, it is possible to simultaneously form the desired end face area and end face height by applying pressure from the end face direction.

  The inner lead is required to have good connectivity and electrical conductivity with a bonding wire or the like that is a conductive wire. The specific electric resistance is preferably 300 μΩ-cm or less, more preferably 3 μΩ-cm or less. Examples of materials that satisfy these conditions include iron, copper, iron-containing copper, tin-containing copper and copper, gold, silver plated aluminum, iron, copper, and the like.

[Coating part 101]
The coating portion 101 is provided on the mount lead cup separately from the mold member 104 and contains a phosphor that converts the light emission of the light emitting element. As a specific material for the coating portion, a transparent resin having excellent weather resistance such as epoxy resin, urea resin, and silicone, and a light-transmitting inorganic material such as silica sol and glass having excellent light resistance are preferably used. Here, in particular, the coating portion using silicon oxide or aluminum oxide as a specific material is filled with a solution containing a phosphor in a metal alkoxide such as ethyl silicate or aluminum alcoholate, and then sintered and dried. Is formed. Moreover, you may contain a diffusing agent with fluorescent substance. As a specific diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, silicon dioxide or the like is preferably used.

[Mold member 104]
The mold member 104 can be provided to protect the light emitting element 102, the conductive wire 103, the coating portion 101 containing the phosphor, and the like from the outside according to the use application of the light emitting diode. In general, the mold member can be formed using a resin. In addition, the viewing angle can be increased by containing the phosphor, but by adding a diffusing agent to the resin mold, the directivity from the light emitting element 102 can be relaxed and the viewing angle can be further increased. Furthermore, by forming the mold member 104 in a desired shape, it is possible to have a lens effect that focuses or diffuses light emitted from the light emitting element. Accordingly, a plurality of mold members 104 may be stacked. Specifically, a convex lens shape, a concave lens shape, an elliptical shape as viewed from the light emission observation surface, or a combination of them. As a specific material of the mold member 104, a transparent resin or glass having excellent weather resistance such as an epoxy resin, a urea resin, or a silicone resin is preferably used. As the diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, silicon dioxide, or the like is preferably used. Furthermore, in addition to the diffusing agent, a phosphor can also be contained in the mold member. Therefore, the phosphor may be contained in the mold member or may be contained in other coating portions. Alternatively, the coating portion may be formed using a resin containing a phosphor, and a different member obtained by replacing the mold member with glass or the like. In this case, a light-emitting device with high productivity and less influence of moisture or the like can be obtained. Further, in consideration of the refractive index, the mold member and the coating portion may be formed using the same member. Inclusion of a diffusing agent or a coloring agent in the mold member can hide the coloring of the phosphor viewed from the light emission observation surface side. In addition, the coloring of the phosphor means that the phosphor absorbs the blue component of the light from the strong external light and emits light. Therefore, it seems to be colored yellow. In particular, depending on the shape of the mold member such as a convex lens shape, the colored portion may appear enlarged. Such coloring may be undesirable in terms of design. The diffusing agent contained in the mold member can make the mold member invisible white by coloring the mold member milky white and the colorant in a desired color. Therefore, the color of the phosphor is not observed from such a light emission observation surface side.

  Further, when the main emission wavelength of light emitted from the light emitting element is 430 nm or more, it is more preferable in terms of weather resistance to contain an ultraviolet absorber as a light stabilizer in the mold member.

In the above embodiment, the YAG phosphor has been described as an example.
However, the present embodiment is not limited to this. For example, the light emitted from the blue light emitting element emits light having a longer wavelength than the excitation light, and the peak of the excitation spectrum is longer than the peak wavelength of the light emitting element. In addition, any phosphor can be used as long as the excitation efficiency is higher on the long wavelength side than on the short wavelength side in the range of the wavelength change of the light emitting element that occurs when the ambient temperature changes.
Specifically, the following lutetium / aluminum / garnet phosphors (hereinafter sometimes referred to as “LAG phosphors”), K ₂ SiF ₆ : Mn phosphors, abbreviated as KSF, and the like are used. it can.

(Lutetium / Aluminum / Garnet phosphor)
The lutetium / aluminum / garnet phosphor is a general formula (Lu _1-ab R _a M _b ) ₃ (Al _1-c Ga _c ) ₅ O ₁₂ (provided that R is at least one element in which Ce is essential). The above rare earth elements, M is at least one element selected from Sc, Y, La, and Gd, and 0.0001 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.5, 0.0001 ≦ a + b <1, 0 ≦ c ≦ 0.8.) For example, the composition formula is (Lu _0.99 Ce _0.01 ) ₃ Al ₅ O ₁₂ , (Lu _0.90 Ce _0.10 ) ₃ Al ₅ O ₁₂ , (Lu _0.99 Ce _0.01 ) ₃ (Al a phosphor represented by _0.5 Ga _{0.5) 5} O _12.
FIG. 3 shows an example of an excitation spectrum of a lutetium / aluminum / garnet phosphor.

  The lutetium / aluminum / garnet phosphor is obtained as follows. As a phosphor raw material, a lutetium compound, a rare earth element R compound, a rare earth element M compound, an aluminum compound, and a gallium compound are used, and each compound is weighed so as to have the ratio of the above general formula, and mixed, or these Flux is added to the phosphor material and mixed to obtain a material mixture. After filling this raw material mixture into a crucible, it is fired at 1200 to 1600 ° C. in a reducing atmosphere, and after cooling, the phosphor according to the present embodiment represented by the above general formula is obtained by dispersion treatment.

  As the phosphor raw material, an oxide or a compound such as a carbonate or hydroxide that becomes an oxide by thermal decomposition is preferably used. Moreover, the coprecipitate which contains all or one part of each metal element which comprises a fluorescent substance can also be used as a fluorescent substance raw material. For example, when an aqueous solution such as alkali or carbonate is added to an aqueous solution containing these elements, a coprecipitate can be obtained, which can be used after being dried or thermally decomposed. Moreover, as a flux, a fluoride, a borate, etc. are preferable, and it adds in 0.01-1.0 weight part with respect to 100 weight part of fluorescent substance raw materials. The firing atmosphere is preferably a reducing atmosphere in which the activator cerium is not oxidized. A mixed gas atmosphere of hydrogen and nitrogen having a hydrogen concentration of 3.0% by volume or less is more preferable. The firing temperature is preferably 1200 to 1600 ° C., and a phosphor having a target center particle diameter can be obtained. More preferably, it is 1300-1500 degreeC.

  In the above general formula, R is an activator, and is at least one or more rare earth elements essential to Ce, specifically, Ce, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lr. R may be Ce alone, but may contain Ce and at least one element selected from rare earth elements other than Ce. This is because rare earth elements other than Ce act as coactivators. Here, it is preferable that Ce contains 70 mol% or more of Ce with respect to the total amount of R. The a value (R amount) is preferably 0.0001 ≦ a ≦ 0.5. If the value is less than 0.0001, the light emission luminance is lowered, and if it exceeds 0.5, the light emission luminance is lowered by concentration quenching. More preferably, 0.001 ≦ a ≦ 0.4, and still more preferably 0.005 ≦ a ≦ 0.2. The b value (M amount) is preferably 0 ≦ b ≦ 0.5, more preferably 0 ≦ b ≦ 0.4, and still more preferably 0 ≦ b ≦ 0.3. For example, when M is Y and the b value exceeds 0.5, the emission luminance due to excitation of long-wavelength ultraviolet light to short-wavelength visible light, particularly 360 to 410 nm is extremely lowered. The c value (Ga content) is preferably 0 ≦ c ≦ 0.8, more preferably 0 ≦ c ≦ 0.5, and still more preferably 0 ≦ c ≦ 0.3. When the c value exceeds 0.8, the emission wavelength shifts to a short wavelength, and the emission luminance decreases.

  The center particle size of the LAG phosphor is preferably in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm, and still more preferably in the range of 5 to 15 μm. Phosphors smaller than 1 μm tend to form aggregates. On the other hand, the phosphor having a particle size in the range of 5 to 50 μm has high light absorptivity and conversion efficiency, and easily forms a light conversion member. As described above, the mass productivity of the light-emitting device is improved by including a phosphor having a large particle diameter and having optically excellent characteristics. Moreover, it is preferable that the phosphor having the central particle size value is contained frequently, and the frequency value is preferably 20% to 50%. By using a phosphor having a small variation in particle size in this way, a light emitting device having a favorable color tone with more suppressed color unevenness can be obtained.

  Since the lutetium / aluminum / garnet phosphor is efficiently excited and emitted by ultraviolet rays or visible light in the wavelength region of 300 nm to 550 nm, it can be effectively used as a phosphor contained in the light conversion member. Furthermore, by using a plurality of types of LAG phosphors having different composition formulas or LAG phosphors together with other phosphors, the emission color of the light emitting device can be variously changed. A conventional light emitting device that emits white mixed light by mixing the blue light emitted from the semiconductor light emitting element and the light emitted from the phosphor emitting yellow light by absorbing the light emitted from the light emitting element. Since part of the light is used through transmission, there is an advantage that the structure itself can be simplified and the output can be easily improved. On the other hand, since the light emitting device emits light by mixing two colors, the color rendering property is not sufficient, and improvement is required. Therefore, a light emitting device that emits white color mixed light using a LAG phosphor can improve its color rendering as compared with a conventional light emitting device. In addition, since the LAG phosphor has excellent temperature characteristics as compared with the YAG phosphor, a light emitting device with little deterioration and color shift can be obtained.

(K ₂ SiF ₆ : Mn phosphor)
The K ₂ SiF ₆ : Mn phosphor has the general formula K ₂ (Si _1-x Mn _x ) F ₆ (where x is 0.01 <x <0.2, and part of Si is Ti , Zr, and Hf group 4 elements and C, Ge, and Sn group 14 elements). For example, it is a phosphor whose composition formula is represented by K ₂ (Si _0.95 Mn _0.05 ) F ₆ .

(K ₂ SiF ₆ : Mn phosphor)
The K ₂ SiF ₆ : Mn phosphor is obtained as follows. Hexafluorosilicic acid is added to a solution in which potassium hydrogen fluoride is dissolved in hydrofluoric acid (solution A) and a solution in which potassium hexafluoromanganate is dissolved in hydrofluoric acid so that the ratio of the above general formula is obtained. The phosphor represented by the above general formula is obtained by adjusting a mixed solution (solution B) to which an aqueous solution is added, and separating, washing, and drying the precipitate obtained by mixing the liquid A and the liquid B. .

Example 1.
As Example 1, the light emitting devices 1, 2, and 3 having the structure shown in FIG. 1 were fabricated using a YAG phosphor having an excitation spectrum peak of 447 nm. The YAG phosphor of Example 1 is Y _2.9 Ce _0.1 Al ₅ O ₁₂ and has the excitation spectrum shown in FIG. A light emitting diode using a nitride semiconductor was used as the light emitting element, and the peak of the emission spectrum was set to 434 nm (light emitting device 1), 438 nm (light emitting device 2), and 441 nm (light emitting device 3), respectively.
In addition, as a comparative example, the same YAG phosphor as that of the example having an excitation spectrum peak of 447 nm was used, and the emission spectrum peak of the light emitting element was 447 nm (Comparative Example 1), 450 nm (Comparative Example 2), and 453 nm ( Three types of comparative examples set in Comparative Example 3) were produced.
The results are shown in Table 1.

The light-emitting element of the light-emitting device 1 has a peak wavelength of 434 nm when the ambient temperature is 25 ° C., and the peak wavelength shifts to the longer wavelength side as the ambient temperature increases, and reaches 440 nm when the ambient temperature reaches 150 ° C. Become. Further, the excitation spectrum of the YAG phosphor of Example 1 has higher excitation efficiency as the excitation wavelength is higher in the range of the excitation wavelength from 434 nm to 440 nm. Therefore, as the ambient temperature rises, the YAG phosphor absorbs more light from the light emitting element, and the luminous intensity increases. As a result, the YAG phosphor itself has a strong yellow tint, and the light emitting element shifts from blue to green on the chromaticity coordinates.
This tendency appears in the chromaticity diagram shown in FIG.

On the other hand, for example, the comparative example will be described as follows in the example of the comparative example 5, for example.
In Comparative Example 5, the light-emitting element has a peak wavelength of 450 nm when the ambient temperature is 25 ° C., but when the ambient temperature increases, the peak wavelength shifts to the longer wavelength side, and the ambient temperature becomes 150 ° C. The peak wavelength of the emission spectrum of the light emitting element is 457 nm.
On the other hand, in the excitation spectrum of the YAG phosphor, the excitation efficiency becomes lower as the peak wavelength is longer in the range from 450 nm to 457 nm.
Therefore, in the range of 450 nm to 457 nm in which the wavelength of the light emitting element changes, the longer the peak wavelength of the light emitting element is, the less light is absorbed from the light emitting element (the more the reflection is), and the light intensity is reduced. Thereby, the yellow color of the YAG phosphor itself is weakened, and the emission color of the light emitting element shifts on the chromaticity coordinates from blue to green.
As described above, in the comparative example, the YAG phosphor itself has a yellowish color, and the emission color of the light emitting element shifts in the green direction. Therefore, the color shift is larger in the comparative example.

Specifically, in the light emitting devices 1 to 3 of Example 1 according to the present embodiment, when the ambient temperature changes from 25 ° C. to 150 ° C., the moving distance on the chromaticity diagram is 0.02 or less. On the other hand, in the light emitting devices of Comparative Examples 1 to 3, the moving distance on the chromaticity diagram exceeds 0.02.
Further, in the light emitting devices 1 to 3 of Example 1 according to the present embodiment, when the ambient temperature changes from 25 ° C. to 150 ° C., the change amount of the color temperature is 600 or less, whereas Comparative Example 1 In the light emitting devices of ˜3, it exceeds 600.
Further, the light emitting device of the example is larger than the light emitting device of the comparative example with respect to the relative value of the light intensity of 150 ° C. with reference to the light intensity of 25 ° C.

  This light-emitting device can be applied to, for example, fluorescent lamps for storefront display lighting, medical field lighting, and backlight light sources for liquid crystal displays.

DESCRIPTION OF SYMBOLS 100 ... Light-emitting device 101 ... Coating part 102 ... Light-emitting element 103 ... Wire 104 ... Mold member 105 ... Mount lead 106 ... Inner lead 107 ... Phosphor

Claims (9)

A light emitting element, and a first phosphor that absorbs at least part of light from the light emitting element and emits light of a different wavelength,
The light emitting element, as the ambient temperature rises, the peak wavelength of the emission spectrum of the light emitting element is shifted to the long wavelength side,
The peak wavelength of the emission spectrum of the light emitting element is on the shorter wavelength side than the peak wavelength of the excitation spectrum of the first phosphor,
In the range of wavelength change that occurs when the ambient temperature of the light emitting element changes, the light emitting device in which the excitation efficiency of the first phosphor is higher on the long wavelength side of the wavelength change range than on the short wavelength side.   2. The light emitting device according to claim 1, wherein a peak wavelength of an emission spectrum of the light emitting element changes by 5 to 20 nm as the ambient temperature increases from 25 ° C. to 150 ° C. 3.   3. The light emitting device according to claim 1, wherein the first phosphor includes Y and Al, and includes an yttrium / aluminum / garnet phosphor activated by at least one element selected from rare earth elements.   The first phosphor further includes at least one element selected from Lu, Sc, La, Gd, Tb, Eu, and Sm, and one element selected from Ga and In. The light-emitting device of description. The first _{phosphor, (Y z Gd 1-z} ) 3 (Al x Ga 1-x) 5 O 12: a Ce (provided that 0 <z ≦ 1,0 <x ≦ 1) according Item 5. The light emitting device according to any one of Items 1 to 4.   The light emitting device according to any one of claims 1 to 5, wherein the first phosphor is covered with a second phosphor.   The light emitting device according to any one of claims 1 to 6, wherein a moving distance on the chromaticity diagram generated when the ambient temperature is changed from 25 ° C to 150 ° C is 0.02 or less.   The light emitting device according to any one of claims 1 to 7, wherein an amount of change in color temperature that occurs when the ambient temperature changes from 25 ° C to 150 degrees is 600 or less.   9. The light emitting device according to claim 1, wherein the 150 ° C. luminous intensity generated when the ambient temperature changes from 25 ° C. to 150 ° C. is greater than 0.67 in terms of relative luminous intensity with respect to 25 ° C. 9.

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