JP2013168658A - Light-emitting device, and vehicular lighting appliance and headlamp using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device which efficiently emits light by reducing a color change with a temperature change even if used in a high-temperature environment.SOLUTION: A light-emitting device is configured by combining a light source which emits exciting light with a phosphor which emits light by absorbing the exciting light. Within a range of environmental temperatures from -20°C to 85°C, a variation of all light flux is within ±30% and on chromaticity coordinates (CIE1931), chromaticity of light to be emitted ranges in x≥0.545, y≥0.39 and y≤x-0.12. Preferably, within the range of environmental temperatures from -20°C to 85°C, on the chromaticity coordinates (CIE1931), the variation of chromaticity ranges in Δx≤0.03 and Δy≤0.03.

Description

  The present invention relates to a light emitting device combining a semiconductor light emitting element (LED) and a novel phosphor and an illumination device using the same, and more particularly to a vehicular lamp and a headlamp whose emission color is amber.

  Conventionally, a vehicle lamp that emits amber color, for example, a direction indicator, which has a built-in amber colored light bulb, has been used. However, there are disadvantages of the light bulb, that is, a large amount of power consumption and restrictions on miniaturization. As a solution to this problem, a device using an LED has been proposed and put into practical use.

  As an amber LED, an AlGaInP semiconductor or a GaAsP semiconductor having an emission spectrum at about 580 to 610 nm is known. However, these LEDs have a problem that the light emission intensity greatly decreases as the ambient temperature increases. For this reason, in applications where the ambient temperature is high, such as rear combination lamps, it is necessary to prepare a large number of amber LEDs to meet the required light intensity, which limits the design of lamps by increasing costs and securing the installation location. It was causing. Further, since the turn signal lamp incorporated in the headlamp is close to the engine and has a particularly high ambient temperature, the above-described amber LED cannot secure a necessary light amount.

On the other hand, the lamp which implement | achieves amber color combining the fluorescent substance which light-emits long wavelength light by light emission of blue LED and LED is also proposed (patent document 1). Patent Document 1 describes that (Ca, Sr) ₂ Si ₅ N ₈ : Eu is used as a long-wavelength phosphor combined with a blue LED.

  However, since this phosphor has a wide half-value width of about 100 nm and many long wavelength components with low visibility, there is a problem that efficiency is low. Moreover, since it has an afterglow characteristic, there is a problem that the afterglow at the time of non-light emission deteriorates visibility in an application in which it is blinked. Furthermore, in the amber-colored lamp described in Patent Document 1, an optical filter for blocking light emitted from the LED is essential.

JP-A-2005-123165

  An object of the present invention is to provide a light-emitting device that emits light efficiently with little color change due to temperature change even when used in a high-temperature environment. Moreover, this invention makes it a subject to provide the vehicle lamp excellent in visibility using the said light-emitting device.

  This invention solves the said subject by using a novel fluorescent substance in the light-emitting device which combined LED and fluorescent substance.

That is, the light-emitting device of the present invention is a light-emitting device that combines a light source that emits excitation light and a phosphor that emits light by absorbing the excitation light, and has an ambient temperature in the range of −20 ° C. to 85 ° C. The change amount of the total luminous flux is within ± 30%, and the chromaticity of the emitted light is x ≧ 0.545, y ≧ 0.39, y ≦ x−0.12 on the chromaticity coordinates (CIE1931). It is characterized by.
  As a phosphor, a general formula: (Ca _α , Eu _β ) (Si, Al) ₁₂ (O, N) ₁₆ (However, 1.5 <α + β <2.2 and 0 <β <0.2, O / N
.Ltoreq.0.04) and a specific surface area of 0.1 to 0.35 m. ² A phosphor of / g is used.

  A vehicle lamp according to the present invention uses the light emitting device.

The figure which shows one Embodiment of the light-emitting device of this invention. The figure which shows one Embodiment of the vehicle lamp of this invention. The figure which shows one Embodiment of the headlamp using the light-emitting device of this invention. The figure which shows the emission spectrum of the light-emitting device of an Example. The figure which shows the temperature dependence of the light beam of the light-emitting device of an Example. The figure which shows the temperature dependence of chromaticity of the light-emitting device of an Example.

Hereinafter, embodiments of the light-emitting device and the vehicular lamp of the present invention will be described.
First, the phosphor constituting the light emitting device of the present invention will be described in detail.

The α-sialon used by the light-emitting device of the present invention is represented by the general formula: M _z (Si, Al) ₁₂ (O, N) ₁₆ , and Ca is used as the element M, and a part thereof is the emission center. This is an Eu-activated Ca-α-sialon phosphor into which Eu is introduced. In general, Eu-activated Ca-α-sialon phosphors are excited by light in a wide wavelength range from ultraviolet to blue, and show visible light emission of yellow to orange. By reducing the oxygen content and increasing the solid solution concentration of Ca (including Eu), long-wavelength emission from orange to red is realized. Specifically, amber light emission is exhibited by excitation in the wavelength range of 420 to 480 nm.

  The α-type sialon phosphor described above includes, for example, (a) silicon nitride, (b) aluminum nitride, (c) a Ca-containing compound, (d) an Eu-containing compound, and (e) an α-type sialon. The raw material mixed powder can be produced by heat-treating the raw material mixed powder at 1650 to 1850 ° C. in a nitrogen atmosphere to obtain α-sialon, and only by classification treatment to obtain a powder having an average particle size of 15 to 25 μm. This method is characterized in that α-sialon (e) is contained in the raw material mixed powder, and a powder having an average particle size of 15 to 25 μm is obtained only by classification treatment. The surface area is small, the luminous efficiency is excellent, the temperature dependence of the luminescent color is small, and the color change is small even in a high temperature environment.

  The molar ratio (α + β) of Ca and Eu in the phosphor exceeds 1.5 and is 2.2 or less. When α + β is 1.5 or less, it is difficult to obtain fluorescence having a peak wavelength of 595 nm or more. On the other hand, if (α + β) exceeds 2.2, a second phase that adversely affects the fluorescence characteristics is likely to be generated. Further, the solid solution amount (value of β) of Eu is less than 0.2. If it is 0.2 or more, the fluorescence peak wavelength shifts, it is difficult to obtain an amber color, and the light emission efficiency decreases.

  The ratio O / N of oxygen and nitrogen is 0.04 or less. If it exceeds 0.04, it is difficult not only to obtain fluorescence having a peak wavelength of 595 nm or more, but also the solid solution limit amount of Ca and Eu decreases, and it becomes difficult to realize α + β> 1.5.

The specific surface area is 0.1 to 0.35 m ² / g. When it is larger than 0.35 m ² / g, the primary particles are not sufficiently developed, or the surface of the phosphor particles is uneven, and as a result, a high luminous efficiency of 60% or more cannot be obtained. On the other hand, if the specific surface area is smaller than 0.1 m ² / g, the particle size becomes too large, and there may be a problem that the dispenser nozzle used at the time of assembling the light emitting device is clogged.
In the present invention, the specific surface area is a value obtained by BET multipoint analysis after measurement based on the BET method.

The light emitting device of the present invention is the same as a known light emitting device except that the α-sialon phosphor is used as the phosphor, and the structure and type are not particularly limited.
FIG. 1 shows a typical light emitting device to which the present invention is applied as a first embodiment. In this light-emitting device, anode / cathode electrodes 4 and 5 are installed in a lamp house 3 made of an insulating material such as glass fiber or epoxy resin, and the LED 2 is lamp housed by an adhesive such as epoxy resin. 3 is fixed. The anode / cathode electrodes of the LED 2 are electrically joined by corresponding lead electrodes 4 and 5 and conductive wires 6. The lamp house 3 is formed with a concave portion at substantially the center, and the orange phosphor and the resin 1 are filled in the concave portion to constitute a light emitting element.

  As the blue LED 2, a known blue LED having a peak wavelength in the range of 420 to 480 nm can be used. Specific examples include GaN-based compound semiconductors, InGaN-based compound semiconductors, ZnO-based compound semiconductors, and ZnSe-based compound semiconductors.

  As a resin that is a sealing material filling the concave portion, any material that is transparent up to a wavelength region shorter than the emission peak wavelength from the LED 2 and can be mixed with a phosphor may be used. Specifically, thermosetting resin, photocurable resin, low melting point glass, and the like can be given. Particularly preferred are thermosetting resins such as epoxy resins, silicone resins, polydimethylsiloxane derivatives having an epoxy group, oxetane resins, acrylic resins and cycloolefin resins. These resins can be used alone or in combination of two or more.

  The chromaticity of light emitted from the light emitting device of the present invention is preferably x ≧ 0.545, y ≧ 0.39, and y ≦ x−0.12 on the chromaticity coordinates (CIE1931). Such chromaticity can be realized by combining a blue LED having a peak wavelength in the range of 420 to 480 nm with the above-described α-sialon phosphor, but the above-described amber color is within a range not departing from this chromaticity range. A phosphor other than the phosphor may be included.

Other phosphors include europium activated M ₂ SiO ₄ (M = Mg, Ca, Sr, Ba), europium activated M ₂ Si ₅ N ₈ (M = Mg, Ca, Sr, Ba), europium. Activated M ₃ SiO ₅ (M = Mg, Ca, Sr, Ba), europium activated MAlSiN ₃ (M = Mg, Ca, Sr, Ba), cerium activated A ₃ B ₅ O ₁₂ (A = Y, Gd, Lu, Tb, B = Al, Ga) and other generally known phosphors can be used singly or in combination of two or more. If necessary, each wavelength conversion material may be mixed with a scattering agent such as barium sulfate, magnesium oxide, or silicon oxide to assist reflection of excitation light and wavelength-converted light.

  The phosphor can be used by mixing an appropriate amount of the above-described resin. The mixing amount in the case of mixing with the resin is not particularly limited, but is usually about 1 to 50% by weight of the resin. It is also possible to disperse the phosphor in the lamp house 3.

  The lamp house 3, the blue LED 2 and the electrodes 4, 5 are electrically connected so that the blue LED 2 is fixed on the lamp house 3, and each lead-out electrode for the anode / cathode and the anode / cathode electrode of the LED 2 correspond to each other. As long as it is made, it can take various forms in addition to the form shown in FIG. For example, although not shown, the anode / cathode electrodes of the LED 2 and the corresponding extraction electrodes are represented by eutectic materials such as Au-Sn, Au bumps, anisotropic conductive sheets, and Ag pastes. A form that is electrically joined and fixed to the lamp house 3 by a conductive resin or the like, and only one electrode of the LED 2 is electrically joined to a corresponding extraction electrode by the above-described material and is fixed to the lamp house 3. The other electrode and the extraction electrode corresponding to the other electrode can be electrically connected with a conductive wire. Further, the lamp house 3 may be made of a conductive material such as metal in order to improve the heat dissipation of the LED 2, and may also serve as a single electrode lead electrode 5.

  A high reflectance material may be formed inside the recess formed in the lamp house 3 by coating, plating, vapor deposition, or the like. The shape of the recess is preferably a substantially truncated cone, but may be a substantially quadrangular pyramid. Although it is desirable that the side wall of the recess be inclined, it may be substantially vertical depending on the application.

  The light-emitting device of the present invention uses a specific Eu-activated Ca-α type sialon phosphor as a phosphor that emits light when excited by a blue LED, so that there is little color change even in a high-temperature environment, and luminous efficiency is low. Good. The light-emitting device of the present invention uses an LED having an emission peak wavelength of 420 to 480 nm and the α-sialon phosphor, so that the area of the emission spectrum having a wavelength of 500 nm or less is 5% or less of the area of the emission spectrum. It can be. As a result, even if there is no optical filter or the like for blocking light with a wavelength of 500 nm or less, the color of x ≧ 0.545, y ≧ 0.39, y ≦ x−0.12 on the chromaticity coordinates (CIE1931). Degree can be realized.

  Next, the vehicle lamp of the present invention and a headlamp incorporating the same will be described.

  FIG. 2 is a diagram showing an example of a vehicular lamp according to the present invention. The lamp includes a light emitting element 21, a support portion 22 that supports the light emitting element 21, a reflector 23 having a substantially arc shape, and an outer lens 24 that is disposed to face the reflector 23. The light emitting element 21 is a light emitting element 21 having the same structure as that of the light emitting device shown in FIG. 1, and the upper surface of the light emitting element filled with the phosphor is arranged so that the light from the outside does not directly hit the light emitting element 21. The light emitting element 21 and the lens 24 are fixed to the support portion 22 so as to face a direction substantially orthogonal to the straight line connecting the light emitting element 21 and the lens 24. The light emitting element 21 is connected to a power supply unit (not shown). The reflector 23 reflects light emitted from the light emitting element 21 toward the lens 24, and at least a surface facing the light emitting element 21 is made of a metal or a white material. For example, a metal film such as aluminum or a white pigment film is formed on the surface by vapor deposition, coating, or the like. Although not shown, an optical filter for adjusting the color as needed may be disposed between the outer lens and the light emitting element.

  With such a structure, the color of the optical filter and the outer lens cannot be seen from the outside when the light emitting element 21 does not emit light. At the time of light emission, the light reflected by the reflector 23 is irradiated to the outside through the lens 24. Accordingly, the color (appearance) is completely different between lighting and non-lighting, and the visibility is good.

  The vehicular lamp of the present invention can be applied to various vehicular lamps such as an in-vehicle turn signal lamp, a rear combination lamp, an in-vehicle illumination lamp, a meter illumination, and a switch illumination. FIG. 3 shows an example of a headlamp to which the present invention is applied. 3A is a front view thereof, and FIG. 3B is a cross-sectional view taken along the line AA. The headlamp is composed of a plurality of lamps such as a high beam lamp 31, low beam lamps 32 and 33, a position lamp 34, and a turn signal lamp 35. The light-emitting device of the present invention can be applied to any of these lamps, and is particularly suitable for a vehicle-mounted turn signal lamp whose amber color range is standardized in each country. In Japan, the amber color range used for in-vehicle turn signal lamps is 0.429 ≧ y ≧ 0.398, z ≦ 0.007 (provided that z = 1−xy, xyz) as orange ranges in JIS D5500. Is standardized as chromaticity coordinates), and in Europe, y ≧ 0.39, y ≧ 0.79−0.67x, and y ≦ x−0.12 are standardized by ECE rules. In the United States, SAE J578c and J578d are standardized as y = 0.39, y = 0.79−0.67x, and y ≦ x−0.12.

  The light emitting element 21 used by the vehicle lamp of the present invention can realize the chromaticity ranges of x ≧ 0.545, y ≧ 0.39, and y ≦ x−0.12 on the chromaticity coordinates (CIE1931). An in-vehicle turn signal lamp that satisfies the standards can be provided.

  In the vehicle lamp of the present invention, since the light-emitting device (light-emitting element 21), which is a light source, is within the chromaticity specification range of the vehicle-mounted turn signal lamp, the turn signal lamp can be manufactured without using an optical filter. It becomes possible. Since no optical filter is used, light emission loss is reduced and efficiency is improved.

  Examples of the present invention will be described below.

1. Production of α-sialon phosphor 61.2% by mass of silicon nitride powder, 22.1% by mass of aluminum nitride powder, 9.5% by mass of calcium nitride powder, 5.0% by mass of calcium fluoride powder, 2.2 europium oxide powder The mass% was mixed using a mortar, filled in a boron nitride crucible, and heat-treated at 1750 ° C. for 16 hours in nitrogen at atmospheric pressure with an electric furnace of a carbon heater. As a result of the powder X-ray diffraction measurement, the powder obtained by the heat treatment was confirmed to be α-sialon.

  15% by mass of powder (α-sialon) obtained by heat treatment, 53% by mass of silicon nitride powder, 19.1% by mass of aluminum nitride powder, 11% by mass of calcium nitride powder, and 1.9% by mass of europium oxide powder were mixed. Then, a boron nitride crucible was filled, and heat treatment was performed at 1750 ° C. for 16 hours in a nitrogen atmosphere in an electric furnace of a carbon heater. The obtained sample was classified with a sieve, and the powder that passed through the 45 μm sieve was used as a phosphor for producing a light emitting device.

As a result of examining the crystal phase of this phosphor by powder X-ray diffraction measurement, the existing crystal phase was only α-sialon. When the fluorescence spectrum was measured with a fluorescence spectrophotometer, the peak wavelength was 600 nm and the half width was 85 nm. The specific surface area was 0.24 m ² / g.

Production method similar to the above, except that the α + β, O / N ratio in the phosphor composition formula (Ca _α , Eu _β ) (Si, Al) ₁₂ (O, N) ₁₆ is changed as shown in Table 1. Thus, a plurality of types of phosphors (Examples 1 to 3, Comparative Examples 1 to 5) were produced. However, the phosphor of Comparative Example 5 was prepared by mixing raw material powder excluding α-sialon as a raw material powder in a stoichiometric ratio.

2. Measurement of emission characteristics of phosphors The fluorescence characteristics of the phosphors of Examples 1 to 3 and Comparative Examples 1 to 5 when excited with excitation light of 455 nm were measured. The results are shown in Table 1.

From comparison between Example 3 (α + β = 1.71) and Comparative Example 1 (α + β = 1) and Comparative Example 2 (α + β = 2.5), the peak wavelength was found when α + β was 1.5 or less. It is difficult to obtain fluorescence with a wavelength of 595 nm or more, and it is found that when an α-sialon exceeding 2.2 is produced, a second phase that adversely affects the fluorescence characteristics is easily generated.

Further, from the comparison between Example 2 (β = 0.04) and Comparative Example 3 (β = 0.25), even if α + β is the same, if the solid solution amount (β value) of Eu exceeds 0.2, It can be seen that the fluorescence peak wavelength also shifts and the luminous efficiency decreases.
From comparison between Example 3 (O / N = 0.02) and Comparative Example 4 (O / N ratio = 0.06), the ratio of oxygen to nitrogen is 0.04 or less for both peak wavelength and luminous efficiency. It turns out that it is preferable.

As for the specific surface area, a comparison between Example 1 (0.24 m ² / g) and Comparative Example 5 (0.42 m ² / g) shows that when the specific surface area is larger than 0.35 m ² / g, high light emission of 60% or more. It turns out that efficiency cannot be obtained.

3. Production of Light-Emitting Device After blending 20 parts by weight of the phosphor of Example 1 with 100 parts by weight of thermosetting silicone resin and stirring uniformly, the electrode 5 and blue LED (gallium nitride compound semiconductor LED, emission wavelength) It was injected into the lamp Hans 3 with a fixed peak (about 460 nm) with an injector. Thereafter, the resin was cured by heating at 150 ° C. for 1 to 4 hours to fix, and a light emitting device as shown in FIG. 1 was produced.

  A current of 350 mA was passed through the blue LED of this light emitting device, and the total luminous flux was measured with an integrating sphere, and the emission spectrum at an ambient temperature of 25 ° C. was measured. The emission spectrum is shown in FIG. As a result, the total luminous flux was about 29 lumen (lm), the peak wavelength was 603 nm, and the half width of the emission spectrum was 86 nm. The integral value of 500 nm or less was 0.33% with respect to the total integral value. The chromaticity coordinates at the time of light emission were x, y = 0.5798, 0.4169, and it was confirmed that the chromaticity coordinates are within the range of amber color used for the on-vehicle turn signal lamp.

4). 2. Evaluation of temperature characteristics With respect to the light-emitting device manufactured in step 1 and the conventional AIGalnP semiconductor LED, a current of 350 mA was applied with the ambient temperature controlled, and the total luminous flux and chromaticity were measured with an integrating sphere. The results are shown in FIGS. In FIG. 5, the intensity of the light beam represents the relative intensity with respect to the light beam when the ambient temperature is 25 ° C. In FIG. 6, a region surrounded by a dotted line indicates an ECE direction indicator chromaticity region, and a one-dot chain line indicates a CIE1971 Spectrum Locus (monochromatic light locus).

As apparent from FIG. 5, the light flux of the AIGalnP semiconductor LED decreases in the high temperature region, whereas the light emitting device of the present invention has a small decrease of the light flux in the high temperature region.
Further, as shown in FIG. 6, the AIGalnP semiconductor LED has a large chromaticity change with respect to the ambient temperature change and deviates from the chromaticity region of the direction indicator, whereas the light emitting device according to the present invention has an ambient environment of 100 Even at ℃, there was little change in chromaticity.

  From these results, it was confirmed that the light-emitting device of the present invention can stably maintain the luminous flux even when the usage environment is high, and the chromaticity change is small.

  According to the present invention, there is provided an amber light emitting device that can stably maintain a light beam even at high temperatures and has little chromaticity change. This light emitting device can be applied to a vehicular lamp and a general amber color light source, and is particularly suitable for a vehicular lamp having a high ambient temperature.

DESCRIPTION OF SYMBOLS 1 ... Resin, 2 ... Blue LED, 3 ... Lamp house, 4, 5 ... Electrode, 6 ... Conductive wire, 21 ... Light emitting element, 23 ... Reflector, 24 ... Outer lens.

Claims (7)

A light-emitting device that combines a light source that emits excitation light and a phosphor that absorbs the excitation light and emits light. When the ambient temperature is in the range of −20 ° C. to 85 ° C., the amount of change in the total luminous flux is ± 30. A light emitting device characterized in that the chromaticity of emitted light is x ≧ 0.545, y ≧ 0.39, and y ≦ x−0.12 on chromaticity coordinates (CIE1931). 2. The light emitting device according to claim 1, wherein the change in chromaticity is Δx ≦ 0.03 and Δy ≦ 0.03 on the chromaticity coordinates (CIE1931) when the environmental temperature is in the range of −20 ° C. to 85 ° C. 3. A light emitting device characterized by the above. A vehicular lamp using the light-emitting device according to claim 1. A vehicle lamp comprising: a light-emitting element; a reflector that receives and reflects light from the light-emitting element; and a lens for irradiating the light reflected by the reflector to the outside, wherein the light-emitting element is used as a light-emitting element. A vehicle lamp characterized by using the light-emitting device according to 2. 5. The vehicle lamp according to claim 4, wherein an area of a region of 500 nm or less in an emission spectrum measured without using a color filter is 5% or less of an area of the entire emission spectrum. Lamps. The vehicular lamp according to claim 4, wherein a main light emission direction of the light emitting element is substantially orthogonal to a main light emission direction of the lamp. A headlamp incorporating the lamp according to any one of claims 3 to 6.

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