JP4732888B2 - Red light emitting phosphor and light emitting module using the same - Google Patents

Description

  The present invention relates to a red light emitting phosphor and a light emitting module using the red light emitting phosphor, and more particularly, to a red light emitting phosphor having improved light resistance as compared with the conventional light emitting module and a light emitting module using the red light emitting phosphor with less luminance reduction and chromaticity deviation. .

Developed a light source for lighting that uses light emitting diodes (LEDs) and semiconductor lasers (LDs) that do not use mercury, combined with phosphors as excitation light sources, and uses light emission at that time as a light source. Has been.
For example, a light emitting diode that exhibits white light emission as a whole is disclosed by additive color mixing with yellow light emission from a Ce-activated rare earth aluminate phosphor that absorbs part of blue light emission and emits light. (Patent Document 1). However, this type of combination has a problem in color rendering properties because the emission color of white light finally obtained is limited, and color reproducibility under illumination of this light source is not reproduced in a preferable color.

  In recent years, in order to solve such problems, as a method of compensating for the disadvantages of white synthesis by adding two colors, ultraviolet or short wavelength visible light is used as primary light (excitation light) from a semiconductor element, and green, blue, red A light emitting module by mixing three-component phosphors is introduced. However, compared with the case where the semiconductor element emits blue light around 450 nm, when ultraviolet light or short wavelength visible light of 360 to 420 nm is used as the primary light, its light energy is high, and the light resistance of the phosphor itself mounted immediately above it is high. Is required.

Specifically, green, blue and red three-component phosphors, blue-emitting phosphors such as BaMgAl ₁₀ O ₁₇ : Eu, (Sr, Ca, Ba) ₅ (PO ₄ ) ₃ Cl: Eu, etc., green-emitting phosphors As Ca ₈ Mg (SiO ₄ ) ₄ Cl: Eu, Mn, BaMgAl ₁₀ O ₁₇ : Eu, Mn, etc., and red emitting phosphors include Y ₂ O ₂ S: Eu or Y ₂ O ₃ : Eu, Bi etc. It has been. At this time, the luminous efficiency of the phosphor of the red light emitting component is greatly inferior to that of the other components, so that a large mixing ratio of the phosphor of the red component is required, and the luminous efficiency of the entire light emitting element is lowered. In recent years, LiEuW ₂ O ₈ was discovered as a red phosphor with relatively high luminous efficiency (Patent Document 2), but it did not have sufficient light resistance corresponding to a light emitting module with a large amount of light.

Japanese Patent No. 2927279 JP 2003-41252 A

When UV or short wavelength visible light is used as the primary light (excitation light) of a semiconductor light emitting device, and a light emitting module that constitutes white light with blue, green and red three-component phosphors emits light with a luminance required for an automobile illumination light source, The phosphor placed immediately above the semiconductor element is exposed to light corresponding to an energy density about 1000 times that of sunlight. Therefore, the phosphor itself is required to have resistance to ultraviolet or short wavelength visible light at this energy density level. Currently, among blue, green, and red three-component phosphors, blue and green phosphors that convert UV or short wavelength visible light efficiently and have UV resistance exist, but the red phosphor LiEuW ₂ Since O ₈ does not have sufficient light resistance, when the white light-emitting module is lit for a long time, the red component in the emission spectrum is reduced and a blue shift occurs in the emission color.

  An object of the present invention is to solve the above-described problems and to provide a red light emitting phosphor having improved light resistance. Moreover, by using the red light-emitting phosphor with improved light resistance obtained in the present invention, a white LED light-emitting module with less luminance reduction and chromaticity deviation can be manufactured.

As a result of intensive studies, the present inventors have achieved the above object by adopting the following configuration, and have achieved the present invention.
(1) A red light emitting phosphor represented by the following general formula.
LiEuW ₂ O ₈・ 1 / xEuAO ₃
(X = 2 to 20 and A is one or more elements selected from boron, aluminum and gallium)
(2) The red light emitting phosphor according to (1), wherein the excitation peak wavelength is 360 to 420 nm.
(3) The red light-emitting phosphor according to (1) or (2), wherein the particle size is 50 μm or less.
(4) A light emitting module comprising a semiconductor element having an emission peak wavelength of 360 to 420 nm and the phosphor according to any one of (1) to (3).
(5) The light emitting module according to (4), wherein a phosphor emitting another color is used as a constituent.
(6) The light emitting module according to (5), wherein the phosphors emitting other colors are at least a green light emitting phosphor and a blue light emitting phosphor and emit white light.
(7) A vehicular lamp using the light-emitting module according to any one of (4) to (6) as a light source.

  Compared with the conventional red light-emitting phosphor, the red light-emitting phosphor of the present invention has improved light resistance, and when used in a light-emitting module, it is possible to obtain a light-emitting module with less luminance reduction and chromaticity deviation.

  The red light emitting phosphor of the present invention is represented by the following general formula.

LiEuW ₂ O ₈・ 1 / xEuAO ₃

(X = 2 to 20 and A is one or more elements selected from boron, aluminum and gallium)

  Such a red light emitting phosphor represented by the above general formula has an excitation peak wavelength of 360 to 420 nm, and among them, the excitation peak wavelength is preferably 390 to 410 nm.

  The red light-emitting phosphor of the present invention preferably has a particle size of 50 μm or less. When the particle size is 50 μm or less, scattering of light on the particle surface of the phosphor can be prevented, and the phosphor can emit light efficiently.

Moreover, the red light emitting phosphor of the present invention can be combined with an ultraviolet light emitting semiconductor element to form a light emitting module. For example, a white light emitting module can be formed by combining an ultraviolet light emitting semiconductor element and a blue / green light emitting phosphor.
In this case, the white light emitting module basically uses a blue light emitting phosphor and a green light emitting phosphor in addition to the red light emitting phosphor of the present invention. In order to obtain it, it is also possible to use other phosphors.

On the other hand, when only the red light emitting phosphor (R), the green light emitting phosphor (G), and the blue light emitting phosphor (B) of the present invention are used as the phosphor, the blending ratio thereof is a spectral fraction ratio. (R) 35-75: (G) 15-50: (B) 2-30, more preferably (R) 45-74: (G) 20-45: (B) 5 15.
Although it does not specifically limit as green fluorescent substance other than the red light emission fluorescent substance of this invention, and blue fluorescent substance, The well-known publicly used fluorescent substance can also be used suitably.

Moreover, a publicly known and used red light-emitting phosphor can be used as appropriate in combination with the red light-emitting phosphor of the present invention.
Examples of the publicly known phosphor include those described in the background art of this specification.
The blue light-emitting phosphor, the green light-emitting phosphor, and the publicly known red light-emitting phosphor of the present invention that are essential for the light-emitting module are preferably UV-resistant.

The semiconductor light emitting device used in the light emitting module using the red light emitting phosphor of the present invention is not particularly limited as long as the emission peak wavelength is 360 to 420 nm. InGaN / GaN generally used as a semiconductor light emitting device that emits ultraviolet light. The system type is preferred. Specifically, those described in JP-A-2002-17100 can be suitably used.
In an InGaN / GaN-based semiconductor light emitting device, the emission peak wavelength becomes longer as the In amount increases, and the emission peak wavelength becomes shorter as the In amount decreases. Therefore, in order to apply the InGaN / GaN-based semiconductor light emitting device to the light emitting module, the amount of In is adjusted as appropriate so that the emission peak wavelength becomes 360 to 420 nm.

A light emitting module using the red light emitting phosphor of the present invention is composed of the above semiconductor light emitting element and the phosphor containing the red light emitting fluorescent light of the present invention. And a structure in which the phosphor layer is provided.
In that case, the phosphor layer provided on the semiconductor light emitting element may be a single layer or a plurality of layers in which at least one kind of phosphor is laminated and a plurality of phosphors are arranged in a single layer. You may mix and arrange | position. As a form in which the phosphor layer is provided on the semiconductor light emitting element, a form in which the phosphor is mixed with a coating member that covers the surface of the semiconductor light emitting element, a form in which the phosphor is mixed with the mold member, or a covering that covers the mold member And a mode in which a translucent plate in which the phosphor is mixed is disposed in front of the light emitting side of the semiconductor light emitting element lamp.

  In addition, at least one of the aforementioned phosphors may be added to the mold member on the semiconductor light emitting device. Furthermore, you may provide the fluorescent substance layer which consists of at least 1 sort (s) or more of the above-mentioned fluorescent substance on the outer side of a light emitting module. As a form provided on the outside of the light emitting module, a form in which the phosphor is applied in layers on the outer surface of the mold member of the light emitting module, or a molded body in which the phosphor is dispersed in rubber, resin, elastomer or the like (for example, cap shape) The form which coats this to a semiconductor light emitting element, or the form which processes the above-mentioned fabrication object in the shape of a plate, and arranges this in front of a semiconductor light emitting element, etc. are mentioned.

An example of a specific form of a light emitting module using the red light emitting phosphor of the present invention is shown in FIG. In the light emitting module shown in FIG. 10, one chip is a short wavelength visible light LED chip having an InGaN active layer and a center wavelength of around 395 nm. This short wavelength visible light LED chip 1 is connected to a lead frame 2 via an adhesive layer. It is fixed to. The short wavelength visible light LED chip 1 and the lead frame 2 are electrically connected by a gold wire 3. The short wavelength visible light LED chip 1 is covered with a phosphor paste 4 in which a phosphor powder is kneaded with a binder resin. Examples of the binder resin of the phosphor paste 4 include silicone resin, epoxy resin, urethane resin, norbornene resin, fluorine resin, metal alkoxide, polysilazane, and acrylic resin. In addition, the light emitting module has a sealing material 5 that covers the periphery of the phosphor paste 4. Examples of the sealing material 5 include materials that are transparent to visible light, such as silicone resin, epoxy resin, urethane resin, norbornene resin, fluorine resin, acrylic resin, and low-melting glass.
In addition, the form for light emitting modules is not limited to this light emitting module structure, For example, there exist various forms, such as coating the light emission surface of the short wavelength visible light LED chip 1 as a fluorescent substance layer.

  The white light emitting module using the red light emitting phosphor of the present invention has a predetermined whiteness, and is preferably in accordance with the following numerical prescription range, which is the white prescription of the vehicle lamp of JIS D 5500. The chromaticity diagram corresponds to the shaded portion in FIG.

Yellow direction x ≦ 0.50
Blue direction x ≧ 0.31
Green direction y ≦ 0.44 and y ≦ 0.15 + 0.64x
Purple direction y ≧ 0.05 + 0.75x and y ≧ 0.382

  A more preferable whiteness defining range is as follows, and corresponds to the shaded portion in FIG.

  0.310 ≦ x ≦ 0.405 and blackbody radiation locus ≦ y ≦ 0.15 + 0.64x

  The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to these examples.

[Example 1]
Preparation of LiEuW ₂ O ₈ · 1 / 6EuBO ₃ Lithium carbonate; 0.37 g, europium oxide; 2.05 g, ammonium tungstate; 5.22 g, boric acid; 0.10 g, weighed uniformly in a mortar for about 20 minutes Mix.
The mixed raw material was put into an alumina crucible and baked in an electric furnace at 700 ° C. for 6 hours. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Example 2]
Preparation of LiEuW ₂ O ₈・ 1 / 6EuAlO ₃
Lithium carbonate; 0.37 g, europium oxide; 2.05 g, ammonium tungstate; 5.22 g, alumina; 0.085 g are weighed and mixed uniformly in a mortar for about 20 minutes.
The mixed raw material was put into an alumina crucible and baked in an electric furnace at 700 ° C. for 6 hours. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Example 3]
Preparation of LiEuW ₂ O ₈ · 1 / 6EuGaO ₃ Lithium carbonate; 0.37 g, europium oxide; 2.05 g, ammonium tungstate; 5.22 g, gallium oxide; Mix.
The mixed raw material was put into an alumina crucible and baked in an electric furnace at 700 ° C. for 6 hours. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Example 4]
Preparation of LiEuW ₂ O ₈ · 15 / 15EuBO ₃ Lithium carbonate; 0.37 g, europium oxide; 1.88 g, ammonium tungstate; 5.22 g, boric acid; 0.04 g are weighed and uniformly in a mortar for about 20 minutes Mix.
The mixed raw material was put into an alumina crucible and baked in an electric furnace at 700 ° C. for 6 hours. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Example 5]
Preparation of LiEuW ₂ O ₈ · 1 / 8EuBO ₃ Lithium carbonate; 0.37 g, europium oxide; 1.98 g, ammonium tungstate; 5.22 g, boric acid; 0.077 g, weighed uniformly in a mortar for about 20 minutes Mix.
The mixed raw material was put into an alumina crucible and baked in an electric furnace at 700 ° C. for 6 hours. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Example 6]
Preparation of LiEuW ₂ O ₈ · 1 / 3EuBO ₃ Lithium carbonate; 0.37 g, europium oxide; 2.35 g, ammonium tungstate; 5.22 g, boric acid; 0.21 g are weighed and uniformly in a mortar for about 20 minutes Mix.
The mixed raw material was put into an alumina crucible and baked in an electric furnace at 700 ° C. for 6 hours. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Comparative Example 1]
Preparation of LiEuW ₂ O ₈ Lithium carbonate; 0.37 g, europium oxide; 1.76 g, ammonium tungstate; 5.22 g are weighed and mixed uniformly in a mortar for about 20 minutes.
The mixed raw material was put into an alumina crucible and baked in an electric furnace at 700 ° C. for 6 hours. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Comparative Example 2]
Preparation of lithium carbonate _{LiEuW 2 O 8 · 1 / 1.5EuBO} 3; 0.37g, europium oxide; 2.89 g, ammonium tungstate; 5.22 g, boric acid; weighed 0.41 g, uniform about 20 minutes in a mortar To mix.
The raw material mixture was placed in an alumina crucible and fired at 700 ° C. for 6 hours in the atmosphere. The obtained fired product was finely pulverized, thoroughly washed with warm pure water, and further filtered and dried to prepare a target phosphor.

[Characteristics of phosphor]
The emission peak wavelengths of Examples 1 to 6 and Comparative Examples 1 and 2 and the excitation peak wavelength at 360 to 420 nm are shown in Table 1.

  The excitation spectra of the phosphors of Examples 1 to 3 and Comparative Example 1 are shown in FIGS. The width of the scale on the vertical axis in each figure represents the width of equal strength. These excitation spectra show almost the same excitation characteristics. Moreover, the same shape was shown also about the other Example.

Next, emission spectra in the vicinity of the excitation peak (395 nm) of the phosphors of Examples 1 to 3 and Comparative Example 1 are shown (FIGS. 5 to 8). The width of the scale on the vertical axis in each figure represents the width of equal strength. These emission spectra show almost the same emission spectrum distribution. Moreover, the same shape was shown also about the other Example.
Table 2 shows data comparing the luminance at that time. The vertical axis of the emission spectrum (FIGS. 5 to 8) is the relative intensity of the same scale, and Table 2 shows the relative integrated intensity of each phosphor when the integrated emission intensity of Comparative Example 1 is 100. . As a result, Examples 1 to 3 were found to have an improved integrated emission intensity of 3 to 26% red light emission as compared with Comparative Example 1.

[Light resistance of phosphor]
As a light source for a vehicle headlamp, a high-luminance light source is required in order to ensure distant visibility. For this purpose, it is necessary to reduce the light emitting area. In the case of a white light-emitting module using a semiconductor light-emitting element that emits ultraviolet or short-wavelength visible light, it is required to place a phosphor close to the semiconductor light-emitting element. An example of the white light emitting module is shown in FIG. Therefore, the phosphor is exposed to ultraviolet or short wavelength visible light having a high energy density from the semiconductor light emitting device, and its resistance is required. The luminance of the vehicle headlamp needs to be ²⁰ cd / mm ² or more. For this purpose, the ultraviolet or short-wavelength visible light energy density directly above the semiconductor light emitting device is 3 to 10 W / cm ² , which corresponds to about 1000 times that of sunlight.

Therefore, i-line (365 nm) was separated and condensed from the high-pressure mercury lamp light emission using a bandpass filter and a condenser lens to form 7 W / cm ² spot light. The phosphor was irradiated with this spot light, and the light resistance of the phosphor was evaluated. The result is shown in FIG. While Comparative Example 1 decreased to about 60% of the integrated emission intensity after 200 hours of UV irradiation, Examples 1 to 3 found that the integrated emission intensity of 80% or more was maintained and excellent light resistance could be secured.

[Color shift due to light-resistant deterioration of white light of additive color mixture]
In order to confirm the effects of Example 1 and Comparative Example 1 in which good light resistance was obtained as described above, performance was evaluated for white light formed by mixing with blue and green phosphors. Evaluation was performed by the following method.

[Adjust white light]
Using BaMgAl ₁₀ O ₁₇ : Eu as the blue phosphor and BaMgAl ₁₀ O ₁₇ : Eu, Mn as the green phosphor, the red phosphors of Example 1 and Comparative Example 1 are mixed, and the chromaticity (x , y = 0.360,0.365). The blending ratio based on the spectral fraction ratio is shown in Table 3.

[Production of white light conversion filter]
The mixed phosphor was mixed with a binder (silicone resin KE106 manufactured by Shin-Etsu Chemical Co., Ltd.) at a phosphor: binder ratio of 1: 1 to prepare a phosphor paste. A phosphor paste was applied to a 10 mm ² , 1 mm thick quartz plate with a thickness of 100 μm and cured at 150 ° C. for 1 hour to produce a white light conversion filter. This filter was exposed to the i-line spot light (7 W / cm ² ) used for the phosphor light resistance evaluation for 200 hours. In the evaluation, the white light conversion filter was irradiated with primary light of 395 nm, and the chromaticity / luminance of the generated white light was measured. The results are shown in Table 4. As a result, it was confirmed that the brightness loss and chromaticity shift greatly occurred in Comparative Example 1, whereas the filter using Example 1 had almost no color shift and light flux decrease.

  * Luminance ratio: Value when the initial luminance of the white conversion filter using Comparative Example 1 is 100

[effect]
According to the above invention, the light resistance of the new red phosphor LiEuW ₂ O ₈ · 1 / xEuAO ₃ is the blue phosphor BaMgAl ₁₀ O ₁₇ : Eu, (Sr, Ca, Ba) ₅ (PO ₄ ) ₃ Cl: Eu, green Phosphor Ca ₈ Mg (SiO ₄ ) ₄ Cl: Eu, Mn, BaMgAl ₁₀ O ₁₇ : Eu, Mn performance has been improved to a white light emitting module using a semiconductor light emitting element that emits ultraviolet or short wavelength visible light. When used, it is possible to expect a module configuration that does not decrease in luminance and does not shift in emission color even when lit for a long time.

  The red light emitting phosphor of the present invention can constitute a light emitting module in combination with, for example, an ultraviolet light emitting semiconductor element, and the light emitting module can be expected to be applied to, for example, a vehicle lamp.

2 is a diagram illustrating an excitation spectrum distribution of a red light-emitting phosphor of Example 1. FIG. 6 is a diagram illustrating an excitation spectrum distribution of a red light-emitting phosphor of Example 2. FIG. 6 is a diagram illustrating an excitation spectrum distribution of a red light-emitting phosphor of Example 3. FIG. It is a figure showing the excitation spectrum distribution of the red light emission fluorescent substance of the comparative example 1. FIG. 4 is a diagram illustrating an emission spectrum distribution of the red light-emitting phosphor of Example 1. It is a figure showing the emission spectrum distribution of the red light emission fluorescent substance of Example 2. FIG. FIG. 6 is a diagram illustrating an emission spectrum distribution of a red light-emitting phosphor of Example 3. It is a figure showing the emission spectrum distribution of the red light emission fluorescent substance of the comparative example 1. It is a figure showing the light resistance of the fluorescent substance of the red light emission of Examples 1-3 and the comparative example 1. FIG. It is a figure which shows an example of a white light emitting module. It is a chromaticity diagram which shows the preferable range of the whiteness of the light which the white light emitting module using the red light emission fluorescent substance of this invention light-emits. It is a chromaticity diagram which shows the more preferable range of the whiteness of the light which the white light emitting module using the red light emission fluorescent substance of this invention light-emits.

Explanation of symbols

1 LED chip 2 Lead frame 3 Metal wire 4 Phosphor paste 5 Sealing material

Claims (7)

A red light-emitting phosphor represented by the following general formula.
LiEuW ₂ O ₈・ 1 / xEuAO ₃
(X = 2 to 20 and A is one or more elements selected from boron, aluminum and gallium)   The red light-emitting phosphor according to claim 1, wherein an excitation peak wavelength is 360 to 420 nm.   3. The red light-emitting phosphor according to claim 1, wherein the particle size is 50 μm or less.   A light emitting module comprising a semiconductor element having an emission peak wavelength of 360 to 420 nm and the phosphor according to any one of claims 1 to 3.   The light emitting module according to claim 4, wherein a phosphor emitting another color is used as a constituent.   6. The light emitting module according to claim 5, wherein the phosphors emitting other colors are at least a green light emitting phosphor and a blue light emitting phosphor, and emit white light.   A vehicular lamp using the light-emitting module according to claim 4 as a light source.

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