JP7637592B2 - Phosphor, fluorescent member and light-emitting module - Google Patents

Description

The present invention relates to a phosphor.

Conventionally, a white light source combining a YAG phosphor and a blue LED has been widely known. On the other hand, as the brightness of the light source increases, thermal concentration due to wavelength conversion (Stokes loss) in the YAG phosphor causes temperature quenching, resulting in a decrease in the efficiency of the white light source. Therefore, _{BaY1.92Al4SiO12} : _{Ce0.08 ,} which is a solid solution of Ba _and Si in a YAG phosphor, has been devised (see Non _- Patent Document 1). This phosphor has better temperature characteristics than the conventional YAG phosphor ( _Y3Al5O12 :Ce), and when heated from ₂₅ °C to 200°C, the luminous intensity maintenance rate is 91.5%, making it less likely to cause temperature quenching.

Haipeng Ji et al., "New Y2BaAl4SiO12:Ce3+ yellow microcrystal-glass powder phosphor with high thermal emission stability", Journal of Materials Chemistry C, 2016, 4, pp.9872-9878

However, the chromaticity range _that can be realized by the yellow phosphor represented _{by BaY1.92Al4SiO12} : _Ce0.08 is limited, and therefore the chromaticity range that can be realized as a white light source by combining this yellow phosphor with a blue LED is also limited.

The present invention was made in light of these circumstances, and one of its objectives is to provide a novel phosphor.

In order to solve the above problems, a phosphor according to one embodiment of the present invention is represented by the general formula M _a Y _3-a-b Al _5-a/2 P _a/2 O ₁₂ :Ce _b (wherein M represents at least one element selected from the group consisting of Ba, Sr, Ca, and Mg, a satisfies 0<a≦1.5, and b satisfies 0<b≦0.12).

This aspect makes it possible to realize a new phosphor with good light emission and temperature characteristics.

The crystal structure may be garnet type.

It may be excited by blue light with a peak wavelength in the range of 430 to 480 nm and emit yellow light with a dominant wavelength in the range of 567 to 572 nm. This allows the realization of a novel yellow phosphor.

The device may be excited by blue light with a peak wavelength in the range of 430 to 480 nm, and emit light whose chromaticity coordinates (cx, cy) satisfy 0.414≦cx≦0.453 and 0.532≦cy≦0.558. This allows a white light source to be realized, for example, by combining the device with a light-emitting element that emits blue light with a peak wavelength in the range of 430 to 480 nm.

Another aspect of the present invention is a fluorescent member. This fluorescent member may include a phosphor powder, which is a powder of the above-mentioned phosphor, and a thermally conductive powder, which is a powder of a material having a thermal conductivity higher than that of the phosphor.

This aspect improves the heat dissipation of the fluorescent material.

The volume ratio of the phosphor powder to the thermally conductive powder may be 90:10 to 60:40. This improves the heat dissipation properties of the fluorescent material while enhancing the light-emitting performance of the fluorescent material.

The phosphor powder absorbs light with a peak wavelength of 450 nm, the thickness of the fluorescent material is 0.12 to 0.30 mm, and the transmittance of the fluorescent material for light with a wavelength of 550 to 600 nm may be 70% or more. This increases the mechanical strength of the fluorescent material while providing light suitable for the desired application (e.g., a headlamp).

The phosphor powder absorbs blue light with a peak wavelength of 450 nm, and the fluorescent material may have a blue light absorption rate of 75 to 85%. This allows light suitable for the desired application (e.g., headlamp) to be realized.

The fluorescent member may include a resin transparent to visible light and a phosphor encapsulated in the resin. The phosphor is contained in the resin at 0.1 to 30 vol %, and the thickness of the fluorescent member may be 0.01 to 5 mm. This makes it possible to realize a light emitting module that achieves a desired luminous efficiency and emits light with a chromaticity in a desired range.

Another aspect of the present invention is a light-emitting module. This light-emitting module includes an LED that emits blue light with a peak wavelength in the range of 430 to 480 nm, and a light wavelength conversion layer that is excited by the blue light emitted by the LED and contains the above-mentioned fluorescent material that emits yellow light. In addition, the emitted light color obtained by mixing the blue light and the yellow light has a chromaticity in the range surrounded by chromaticity coordinates (cx, cy) = (0.311, 0.339), (0.313, 0.342), (0.331, 0.354), (0.331, 0.338), (0.319, 0.315), and (0.311, 0.309).

This aspect makes it possible to realize a white light source suitable for a specific application (e.g., vehicle headlights).

Any combination of the above components, and expressions of the present invention converted between manufacturing methods, devices such as lamps and lighting, light-emitting modules, light sources, etc. are also valid aspects of the present invention.

The present invention provides a novel phosphor.

1 is a chromaticity diagram (CIE 1931) showing the chromaticity of the emission color of a conventional yellow phosphor and a blue LED. FIG. 4 is a diagram for explaining a range of dominant wavelengths targeted by a yellow phosphor according to the present embodiment. FIG. 4 is a diagram showing the relationship between the amount of P contained in the yellow phosphor and the dominant wavelength in the yellow phosphor according to the embodiment. FIG. 13 is a graph showing the relationship between the amount of P charged and the emission intensity. FIG. 13 is a graph showing the relationship between the amount of P charged and the temperature characteristics (luminescence intensity maintenance rate). 1 is a schematic diagram of a light-emitting module according to an embodiment of the present invention; 11 is a diagram for explaining the relationship between the chromaticity of the emitted color of the light-emitting modules according to Examples 11 to 14 and the concentration of the contained yellow phosphor. FIG.

The present invention will be described below with reference to the drawings based on preferred embodiments. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and duplicated descriptions will be omitted as appropriate. Furthermore, the embodiments do not limit the invention but are merely examples, and all of the features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[Phosphor]
The phosphor according to the present embodiment is a phosphor that is efficiently excited by blue light and emits light. Specifically, it is a phosphor that is strongly excited by blue light having a peak wavelength in the range of 430 to 480 nm, and emits yellow light having a dominant wavelength in the range of 567 to 572 nm. In addition, the phosphor according to the present embodiment has a garnet-type crystal structure, and achieves yellow light emission by doping with an activator such as Ce ³⁺ ions.

Next, the phosphor according to this embodiment will be described in detail. The phosphor according to this embodiment is represented by the general formula M _a Y _3-a-b Al _5-a/2 P _a/2 O ₁₂ : Ce _b (wherein M represents at least one element selected from the group consisting of alkaline earth metals Ba, Sr, Ca, and Mg, a satisfies 0<a<1.5, and b satisfies 0<b<0.12). The circumstances by which the present inventors arrived at this phosphor are as follows.

(1) Dominant wavelength shift Cerium (Ce ³⁺ ), a light-emitting ion of YAG phosphor, forms a dodecahedral structure factor (Ce site) with oxygen (O) in the crystal. At that time, the Ce site shares edges with SiO ₄ tetrahedrons (side length 1.60 Å) or AlO ₄ tetrahedrons (side length 1.74 Å) at two places. By replacing the Si (ionic radius 0.26 Å) of this SiO ₄ tetrahedron with phosphorus (P) (ionic radius 0.17 Å) with a smaller ionic radius than Si, a PO ₄ tetrahedron (side length 1.48 Å) smaller than the SiO ₄ tetrahedron is generated. As a result, the edge shared with the Ce site is reduced, causing distortion in the Ce site, and the crystal field energy is increased, leading to the possibility of realizing a phosphor whose dominant wavelength is shifted to the long wavelength side.

Figure 1 is a chromaticity diagram (CIE 1931) showing the chromaticity of the emission color of a conventional yellow phosphor and a blue LED. Point C1 shown in Figure 1 is the chromaticity coordinate of a known phosphor ( _{BaY1.92Al4SiO12} : _Ce0.08 ) in which Ba and _Si are solid-dissolved in a YAG phosphor, and _the dominant wavelength of this known phosphor is 566.3 nm. Meanwhile, point C2 is the chromaticity coordinate of an example of a blue LED whose peak wavelength is in the range of 430 to 480 nm.

Range R1 is the chromaticity range defined as the white light for a specific application (vehicle headlights). Specifically, range R1 is the range bounded by chromaticity coordinates (cx, cy) = (0.311, 0.339), (0.313, 0.342), (0.331, 0.354), (0.331, 0.338), (0.319, 0.315), (0.311, 0.309).

Mixed light that combines yellow light from a known phosphor with blue light from an LED has a chromaticity on the line connecting points C1 and C2. Therefore, as shown in Figure 1, if the dominant wavelength of the yellow light is on the long wavelength side, white light falling within range R1 cannot be achieved unless the blue LED is changed. Therefore, there is a demand for a phosphor whose dominant wavelength is shifted to the long wavelength side compared to conventional yellow phosphors, such as the yellow light phosphor of the present invention.

(2) Suppression of thermal quenching The cause of thermal quenching is thought to be the increase in lattice vibration when the temperature rises. More specifically, the excitation energy absorbed by Ce is absorbed by the vibration of oxygen ions coordinated to Ce due to the fluctuation (expansion-contraction) of the coordination structure of Ce, which is a luminescent element, and is deactivated.

In the crystals of a conventional phosphor in which Ba and Si are dissolved in a YAG phosphor, the AlO ₄ tetrahedron formed by Al and O and the SiO ₄ tetrahedron formed by Si and O have equivalent bonds between Al and O (Al-O) and Si and O (Si-O), so that the positions of Al and Si are fixed and a strong tetrahedral unit is formed. This tetrahedral unit vibrates as a strong tetrahedron when the temperature rises, so that the Ce sites sharing the edges are subjected to large lattice vibration.

On the other hand, in a _PO4 tetrahedron formed by P and O, one of the bonds (P-O) with four O coordinated to P forms a double bond, so the position of P is not equivalent to the four O. Therefore, P can vibrate (change position) in the _PO4 tetrahedron. As a result, the influence of thermal vibration on the Ce site sharing the edge is reduced, and the present inventors have conceived the possibility of suppressing thermal quenching.

The following provides a more detailed explanation using examples, but the following descriptions of the phosphor raw materials, manufacturing method, and chemical composition of the phosphor do not in any way limit the embodiments of the phosphor of the present invention.

Example 1
The phosphor according to Example 1 is a phosphor represented by Ba _0.80 Y _2.14 Al _4.60 P _0.40 :Ce ³⁺ _0.06 . The phosphor according to Example 1 is manufactured by the following method. First, powder raw materials of BaCO ₃ (99.9%: manufactured by Kanto Chemical Co., Ltd.), Y ₂ O ₃ (99.9%: manufactured by High Pure Chemical Laboratory Co., Ltd.), CeO ₂ (99.99%: manufactured by High Pure Chemical Laboratory Co., Ltd.), α-Al ₂ O ₃ (99.99%: manufactured by High Pure Chemical Laboratory Co., Ltd.), and AlPO ₄ (manufactured by High Pure Chemical Laboratory Co., Ltd.) are prepared. Then, each powder raw material is weighed so that the molar ratio is Ba=0.80, Y=2.14, Al=4.60, P=0.40, and Ce=0.06.

BaF ₂ (99%: manufactured by Kojundo Chemical Laboratory Co., Ltd.) was weighed as a flux at 5 wt% of the total weight of the powder raw material, and was combined with the powder raw material and uniformly mixed in a mortar. Then, it was placed in an alumina crucible (SSA-S B1: manufactured by Nikkato Co., Ltd.) and heated and sintered at 1550°C for 4 hours in a reducing atmosphere (H ₂ :N ₂ = 5/95 (vol ratio)). After cooling to room temperature, it was crushed in a mortar, and the emission characteristics of the phosphor excited by light with a wavelength of 460 nm were measured using a spectrophotometer (FP-8500: manufactured by JASCO Corporation).

As a result, the dominant wavelength of the phosphor of Example 1 was 569.0 nm, and the emission intensity was 1.15 times that of the comparative example not containing P, which will be described later. In terms of temperature characteristics, the emission intensity maintenance rate when the temperature was raised from 25°C to 200°C was evaluated and found to be 95.0%.

The results of the light emission characteristics and temperature characteristics of the phosphors of each Example and Comparative Example are summarized in Table 1. Note that in Table 1, the results are listed in order starting from Example 8, which has the smallest amount of P.

Example 2
The phosphor according to Example 2 is a phosphor represented _{by Ba1.00Y1.94Al4.50P0.50} :Ce3 ⁺ _0.06 . The phosphor was produced under the same conditions as in Example ₁ , except that the _raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba=1.00, Y=1.94, Al=4.50, P=0.50, and Ce=0.06, and the luminescence characteristics and temperature characteristics were evaluated.

Example 3
The phosphor according to Example 3 is a phosphor represented _{by Ba0.60Y2.34Al4.70P0.30} : _Ce3 ⁺ _0.06 . The phosphor was produced under the same conditions as in Example 1, except that the _raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba = 0.60, Y = 2.34, Al = 4.70, P = 0.30, and Ce = 0.06, and the light emission characteristics and temperature characteristics were evaluated.

Example 4
The phosphor according to Example 4 is a phosphor represented _{by Ba0.50Y2.44Al4.75P0.25} : _Ce3 ⁺ _0.06 . The phosphor was produced under the same conditions as in Example 1, except that the _raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba = 0.50, Y = 2.44, Al = 4.75, P = 0.25, and Ce = 0.06, and the light emission characteristics and temperature characteristics were evaluated.

Example 5
The phosphor according to Example 5 is a phosphor represented _{by Ba0.20Y2.77Al4.90P0.10} : ^Ce3+ _{0.03 .} The phosphor was produced under the same conditions as in Example 1, except that the _raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba = 0.20, Y = 2.77, Al = 4.90, P = 0.10, and Ce = 0.03, and the light emission characteristics and temperature characteristics were evaluated.

Example 6
The phosphor according to Example 6 is a phosphor represented _{by Ba1.20Y1.72Al4.40P0.60} :Ce3 ⁺ _0.08 . The phosphor was produced under the same conditions as in Example ₁ , except that the _raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba=1.20, Y=1.72, Al=4.40, P=0.60, and Ce=0.08, and the luminescence characteristics and temperature characteristics were evaluated.

(Example 7)
The phosphor according to Example 7 is a phosphor represented _{by Ba1.30Y1.60Al4.35P0.65} : _Ce3 ⁺ _0.10 . The phosphor was produced under the same conditions as in Example 1, except that the _raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba=1.30, Y=1.60, Al=4.35, P=0.65, and Ce=0.10, and the light emission characteristics and temperature characteristics were evaluated.

(Example 8)
The phosphor according to Example 8 is a phosphor represented by _{Ba0.10Y2.87Al4.95P0.05} : _Ce3 ⁺ _0.03 . The same raw material powders _as those in Example 1 were weighed out in the molar ratios _of Ba=0.10, Y=2.87, Al=4.95, P=0.05, and Ce=0.03, but the phosphor was produced under the same conditions as those in Example 1, and the luminescence characteristics were evaluated. The results of the luminescence characteristics and temperature characteristics are shown in Table 1.

Example 9
The phosphor according to Example 9 is a phosphor represented _{by Ba1.50Y1.38Al4.25P0.75} : _Ce3 ⁺ _0.12 . The phosphor was produced under the same conditions as in Example 1, except that the _raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba=1.50, Y=1.38, Al=4.25, P=0.75, and Ce=0.12, and the light emission characteristics and temperature characteristics were evaluated.

Example 10
The phosphor according to Example 10 is a phosphor represented _{by Ba1.10Y1.84Al4.45P0.55} : _Ce3 ⁺ _0.06 . The phosphor was produced under the same conditions _as in Example 1, except that the raw material powders similar to those in Example 1 were weighed to have molar ratios of Ba=1.10, Y=1.84, Al=4.45, P=0.55, and Ce=0.06, and the luminescence characteristics and temperature characteristics were evaluated.

Comparative Example
The phosphor according to the comparative example is a phosphor represented by Ba _1.00 Y _1.92 Al _4.00 Si _1.00 : Ce ³⁺ _0.08 . The phosphor according to the comparative example is manufactured by the following method. First, powder raw materials of BaCO ₃ (99.9%: manufactured by Kanto Chemical Co., Ltd.), Y ₂ O ₃ (99.9%: manufactured by High Purity Chemical Laboratory Co., Ltd.), CeO ₂ (99.99%: manufactured by High Purity Chemical Laboratory Co., Ltd.), α-Al ₂ O ₃ (99.99%: manufactured by High Purity Chemical Laboratory Co., Ltd.), and SiO ₂ (99.9%: manufactured by Tokuyama Corporation) are prepared. Then, each powder raw material is weighed so that the molar ratio is Ba = 1.00, Y = 1.92, Al = 4.00, Si = 1.00, and Ce = 0.08. Thereafter, phosphors were produced under the same conditions as in Example 1, and the light emission characteristics and temperature characteristics were evaluated.

Figure 2 is a diagram for explaining the range of dominant wavelengths targeted by the yellow phosphor of this embodiment. In order to achieve the chromaticity range defined as the white light of a vehicle headlight in combination with a blue LED, the yellow phosphor of this embodiment requires that the straight line connecting the chromaticity of the blue LED (cx2, cy2) and the chromaticity of the yellow phosphor (cx1, cy1) pass through range R1.

According to the inventors' studies, when a line connecting the chromaticity (cx2, cy2) of the blue LED at point C2 and the chromaticity (cx1', cy1') of the yellow phosphor at point C1' meets at the top of the chromaticity range R1, the dominant wavelength is 567.4 nm. Similarly, when a line connecting the chromaticity (cx2, cy2) of the blue LED at point C2 and the chromaticity (cx1", cy1") of the yellow phosphor at point C1" meets at the bottom of the chromaticity range R1, the dominant wavelength is 570.6 nm.

Therefore, the yellow phosphor according to this embodiment has a dominant wavelength in the range of 567 to 572 nm, and preferably has a dominant wavelength in the range of 567.4 to 570.6 nm.

Figure 3 is a diagram showing the relationship between the amount of P and the dominant wavelength in the yellow phosphor according to this embodiment. Note that Figure 3 illustrates Examples 1 to 4, which have the same amount of Ce, 0.06 mol, but as shown in Table 1, it can be seen that in all of the yellow phosphors of Examples 1 to 10, the dominant wavelength of 566.3 nm, which is the dominant wavelength of a known yellow phosphor, is shifted to the longer wavelength side. In addition, the dominant wavelength of the yellow phosphors of each Example except Example 8 is in the range of 567 to 572 nm. In addition, the dominant wavelength of the yellow phosphors of each Example except Examples 8 and 9 is in the range of 567.4 to 570.6 nm.

That is, in the general formula M _a Y _3-a-b Al _5-a/2 P _a/2 O ₁₂ :Ce _b of the yellow phosphor according to this embodiment, a is preferably in the range of 0<a≦1.5, more preferably 0.10≦a≦1.50, and further preferably 0.20≦a≦1.30. Also, b is preferably in the range of 0<b≦0.12.

Figure 4 is a diagram showing the relationship between the amount of P charged and the emission intensity. Figure 5 is a diagram showing the relationship between the amount of P charged and the temperature characteristics (emission intensity maintenance rate). As shown in Figure 4, when the amount of P charged is in the range of 0.20 to 0.50 mol, the emission intensity of the yellow phosphor according to this embodiment is improved by about 10 to 15% compared to the comparative example. In other words, when focusing on the emission intensity, a in the general formula representing the yellow phosphor according to this embodiment is preferably in the range of 0.40≦a≦1.00.

As shown in FIG. 5 and Table 1, taking into consideration the decrease in temperature characteristics in Examples 7 and 9 (the emission intensity at 200°C decreases to 0.88 to 0.90 times that at 25°C), it is preferable that a in the general formula representing the yellow phosphor according to this embodiment is in the range of 0.10≦a≦1.20 and b is in the range of 0.03≦b<0.10. Preferably, if a is in the range of 0.50≦a≦0.80, an emission intensity maintenance rate of about 95% can be achieved.

As described above, the yellow phosphor according to this embodiment is a novel phosphor with good light emission and temperature characteristics. In addition, it is preferable that this yellow phosphor emits light whose chromaticity coordinates (cx, cy) satisfy 0.414≦cx≦0.453 and 0.532≦cy≦0.558. This makes it possible to realize a white light source by combining it with a light emitting element that emits blue light with a peak wavelength in the range of 430 to 480 nm, for example.

[Light emitting module]
FIG. 6 is a schematic diagram of a light emitting module according to the present embodiment. The light emitting module 10 according to the present embodiment includes a mounting substrate 12, an LED 14 which is a light emitting element mounted on the mounting substrate 12, and a light wavelength conversion layer 16 in which a phosphor is dispersed in a resin. The LED 14 emits blue light with a peak wavelength in the range of 430 to 480 nm. The light wavelength conversion layer 16 includes a fluorescent member in which the yellow phosphor according to the present embodiment is dispersed in a silicone resin which is transparent to visible light. The light wavelength conversion layer 16 contains 0.1 to 30 vol % of the yellow phosphor and has a thickness t of 0.01 to 5 mm. The thickness may be in the range of 0.1 to 2 mm. The volume concentration of the yellow phosphor may be 10 vol % or less. This makes it possible to realize a light emitting module in which the desired light emitting efficiency is achieved while the light emitting color has a chromaticity in the range suitable for the headlamp described above.

The light emission characteristics of the white light emitting modules combining the phosphors of Examples 1, 4, 5, and 7, which produced yellow light of the desired dominant wavelength, with a blue LED, were evaluated below. Figure 7 is a diagram for explaining the relationship between the chromaticity of the emitted color of the light emitting modules of Examples 11 to 14 and the concentration of the yellow phosphor contained therein.

(Example 11)
The light wavelength conversion layer, in which the phosphor according to Example 1 (P content 0.40) was mixed in an arbitrary concentration with a transparent silicone resin, was potted with a thickness of t=0.5 mm so as to cover the light emission surface of a blue LED with a peak wavelength of 460 nm, to produce a white light emitting module. As a result of evaluating the emission color of the light emitting module with different concentrations of the yellow phosphor, the chromaticity of the emission color changed on a straight line connecting the chromaticity of the yellow phosphor and the chromaticity of the blue LED. In the case of the light emitting module according to Example 11, when the concentration of the phosphor according to Example 1 was 3, 4, 5, 6, and 7 vol%, the chromaticity of the emission color of the light emitting module fell within the desired chromaticity range R1 suitable for a headlamp.

Example 12
The phosphor according to Example 4 (P content 0.25) was mixed in an arbitrary concentration in a transparent silicone resin to form a light wavelength conversion layer, which was potted with a thickness of t=0.5 mm so as to cover the light emission surface of a blue LED with a peak wavelength of 460 nm, to produce a white light emitting module. As a result of evaluating the emission color of the light emitting module with different concentrations of the yellow phosphor, the chromaticity of the emission color changed on a straight line connecting the chromaticity of the yellow phosphor and the chromaticity of the blue LED. In the case of the light emitting module according to Example 12, when the concentration of the phosphor according to Example 4 was 3.5 vol%, the chromaticity of the emission color of the light emitting module fell within the desired chromaticity range R1 suitable for headlamps.

(Example 13)
The light wavelength conversion layer, in which the phosphor according to Example 5 (P content 0.10) was mixed in an arbitrary concentration with a transparent silicone resin, was potted with a thickness of t=0.5 mm so as to cover the light emission surface of a blue LED with a peak wavelength of 460 nm, to produce a white light emitting module. As a result of evaluating the emission color of the light emitting module with different concentrations of the yellow phosphor, the chromaticity of the emission color changed on the straight line connecting the chromaticity of the yellow phosphor and the chromaticity of the blue LED. In the case of the light emitting module according to Example 13, when the concentration of the phosphor according to Example 4 was 3 vol%, the chromaticity of the emission color of the light emitting module fell within the desired chromaticity range R1 suitable for a headlamp.

(Example 14)
The phosphor according to Example 7 (P content 0.65) was mixed in an arbitrary concentration in a transparent silicone resin to form a light wavelength conversion layer, which was potted with a thickness of t=0.5 mm so as to cover the light emission surface of a blue LED with a peak wavelength of 460 nm, to produce a white light emitting module. As a result of evaluating the emission color of the light emitting module with different concentrations of the yellow phosphor, the chromaticity of the emission color changed on a straight line connecting the chromaticity of the yellow phosphor and the chromaticity of the blue LED. In the case of the light emitting module according to Example 14, when the concentration of the phosphor according to Example 4 was 5, 6, and 7 vol%, the chromaticity of the emission color of the light emitting module fell within the desired chromaticity range R1 suitable for a headlamp.

[Sintered body containing phosphor powder]
In the following, a sintered body, which is an example of a fluorescent member containing a phosphor powder that is a powder of the above-mentioned phosphor, will be described. The sintered body may be produced using various known sintering techniques. For example, the phosphor powder may be filled into a mold and molded, and the obtained molded body may be subjected to CIP (Cold Isostatic Pressing) and HIP (Hot Isostatic Pressing), etc., to produce a sintered body.

The sintered body may contain various materials as necessary in addition to the phosphor powder, for example, a thermally conductive powder, which is a powder of a material having a thermal conductivity higher than that of the phosphor. This material may be, for example, aluminum nitride (AlN), which is a dielectric material having a thermal conductivity of about 170 W/mK, or aluminum oxide (Al ₂ O ₃ ), which has a thermal conductivity of about 20 W/mK. By including a thermally conductive powder in addition to the phosphor powder, the heat generated when the sintered body emits light can be diffused more quickly than when the sintered body does not include a thermally conductive powder. According to this embodiment, the heat dissipation property of the sintered body can be improved, so that even when the sintered body is mounted on a high-luminance LED, the temperature rise during light emission can be suppressed, and the deterioration of the light-emitting performance at high temperatures can be suppressed.

The volume ratio of the phosphor powder and the thermally conductive powder contained in the sintered body is preferably 90:10 to 60:40. By making the volume ratio of the thermally conductive powder 10 vol% or more and the volume ratio of the phosphor powder 90 vol% or less, the heat dissipation of the sintered body can be further improved. By making the volume ratio of the thermally conductive powder 40 vol% or less and the volume ratio of the phosphor powder 60 vol% or more, the light absorption rate (e.g., blue light with a peak wavelength of 450 nm) and light transmittance (e.g., yellow light with a wavelength of 550 to 600 nm) of the sintered body can be increased. In this specification, the volume ratio means the volume ratio to the total volume of the phosphor powder and the thermally conductive powder contained in the fluorescent member such as the sintered body.

The shape of the sintered body is not particularly limited, and the sintered body can be processed into various shapes, but for example, the shape of the sintered body may be a plate shape having a predetermined thickness. Also, the shape of the sintered body may be, for example, a shape having a predetermined thickness used as an optical wavelength conversion layer as shown in FIG. 6.

The thickness of the sintered body is not particularly limited, but is preferably 120 to 300 μm (0.12 to 0.30 mm). By making the thickness of the sintered body 120 μm or more, the mechanical strength of the sintered body can be increased. This makes the sintered body less likely to break and easier to handle. In addition, by making the thickness of the sintered body 300 μm or less, leakage of light irradiated from the LED to the sintered body from the side of the sintered body is suppressed, making it possible to increase the effective luminous flux of the sintered body.

The sintered body may transmit light of various wavelengths, for example light with a wavelength of 550 to 600 nm. The transmittance of the sintered body for light (for example light with a wavelength of 550 to 600 nm) may be 70% or more. The sintered body (more specifically, the phosphor contained in the sintered body) may absorb light of various wavelengths, for example blue light with a peak wavelength of 450 nm. The absorptance of the sintered body for blue light may be, for example, 75 to 85%. This allows a light source that emits white light suitable for a desired application (for example a headlamp) to be realized by combining a light source that emits blue light (for example an LED) with a fluorescent member. For example, by combining a blue LED with a fluorescent material, it is possible to realize a light source that emits white light with a chromaticity in the range surrounded by chromaticity coordinates (cx, cy) = (0.311, 0.339), (0.313, 0.342), (0.331, 0.354), (0.331, 0.338), (0.319, 0.315), and (0.311, 0.309).

The following provides a more detailed explanation of the sintered body containing phosphor powder using examples.

(Example 15)
The phosphor used in the sample according to Example 15 is a phosphor represented _{by Ba0.04Y2.91Al4.98P0.02O12:Ce3+0.05 . First ,} powder raw materials _of BaO3 ( _99.9 % ₎ , _Y2O3 (99.9%), α- _Al2O3 (99.99%), _{AlPO4 (} 99.99%), and _CeO2 (99.99%) were prepared. ^Then , each powder raw material was weighed so as to have a molar ratio of Ba=0.04, _Y =2.91, Al=4.98, P=0.02, and Ce=0.05.

BaF ₂ (99%) was weighed as a flux at 5 wt% of the total weight of the powder raw materials, and the BaF ₂ was combined with the weighed powder raw materials, and they were uniformly mixed in a mortar to obtain a mixed powder. The mixed powder was then placed in an alumina crucible (SSA-S B1: manufactured by Nikkato Corporation), and heated and sintered at 1550°C for 4 hours in a reducing atmosphere (H ₂ :N ₂ = 5/95 (vol ratio)) to obtain a phosphor. The phosphor was then cooled to room temperature and crushed using a mortar to obtain a phosphor powder with a particle size of 1 to 30 μm.

The resulting phosphor powder and AlN powder (99.9%) were weighed out so that the volume ratio was 90:10. Next, the phosphor powder and AlN powder were mixed and pulverized using a ball mill so that the particle size of these powders was 3 μm or less.

The powder obtained by mixing and pulverization was filled into a φ20 mm mold, and the powder was molded at a molding pressure of 10 MPa to obtain a primary molded body. Next, the primary molded body was compression molded at a molding pressure of 98 MPa using CIP to obtain a secondary molded body. Next, the secondary molded body was heated at 1650°C for 24 hours in a nitrogen atmosphere of ^1x10-3 Pa using a heating furnace. Furthermore, the heated secondary molded body was heated by HIP under conditions of 196 MPa and 1550°C for 24 hours to obtain a sintered body. Next, the obtained sintered body was ground and polished using sandpaper to adjust the thickness to 100 μm, and cut into a size of 1 mm square to prepare a plate-shaped sintered body sample.

The thermal conductivity of the samples was measured using a thermal conductivity meter by the steady-state method. The standard value for thermal conductivity was set to 30 W/mK, and if the measured value was equal to or greater than this standard value, the sample was evaluated as having good thermal conductivity.

The transmittance of the samples was measured using a spectrophotometer (Hitachi). The wavelength of the excitation light was 460 nm, and the measurement light was yellow light with a wavelength of 600 nm. If the transmittance of the yellow light was 70% or more, the sample was evaluated as having good transmittance.

The absorbance of the samples was measured using an integrating sphere. The excitation light was blue light with a wavelength of 460 nm. A sample was evaluated as having good absorbance when the absorbance of blue light was 75% to 85%.

In addition, the effective luminous flux of the sample was measured using a luminometer. Specifically, a plate-shaped sample was mounted on an LED chip that emits 460 nm excitation light, and the LED chip was made to emit excitation light. Measurements were taken only directly above and on the sides of the sample, and the effective luminous flux was calculated. If the amount of light leaking from the sides of the sample was 10% or less, the effective luminous flux of the sample was evaluated as good.

In addition, a sample was evaluated as having good handleability if it was not damaged when handled with tweezers.

Furthermore, if the thermal conductivity, transmittance, absorptance, ease of handling, and effective luminous flux of a sample were all evaluated as good, the overall evaluation of that sample was deemed to be good.

The preparation conditions and evaluation results for the samples in each example are summarized in Table 2.

(Examples 16 to 20)
In Examples 16 to 20, sintered body samples were prepared in the same manner as in Example 15, except that the thickness of the sample was changed to 120, 180, 240, 300 or 360 μm.

(Examples 21 to 38)
In Examples 21 to 38, sintered body samples were produced in the same manner as in Example 15, except that the volume ratio of the phosphor powder to the AlN powder and the thickness of the sample were changed to the values shown in Table 2. Specifically, the volume ratio of the phosphor powder to the AlN powder was set to 70:30, 60:40, or 50:50, and for each volume ratio, the thickness of the sample was set to 100, 120, 180, 240, 300, or 360 μm, and sintered body samples were produced.

(Example 39)
In Example 39, the mixed powder was heated and sintered in the same manner as in Example 15, and the resulting phosphor was pulverized in a mortar to obtain a phosphor powder. This phosphor powder was not mixed with AlN powder, but was pulverized using a ball mill.

Next, the phosphor powder pulverized using a ball mill was filled into a φ20 mm mold, and the phosphor powder was molded at a molding pressure of 10 MPa to obtain a primary molded body. Thereafter, a sintered body sample was produced in the same manner as in Example 15.

(Example 40)
In Example 40, a sintered body sample was prepared in the same manner as in Example 23, except that Al ₂ O ₃ powder was mixed into the phosphor powder instead of AlN powder, i.e., the volume ratio of the phosphor powder to the thermal conductive powder was 70:30, and the thickness of the sample was 180 μm.

The above describes the method for producing the samples in the examples. The evaluation results are described below.

The thermal conductivity of the samples containing AlN powder according to Examples 15 to 38 all exceeded the reference value and were good. Furthermore, in Examples in which the volume fraction of AlN powder was 10 to 40 vol% and the sample thickness was 120 to 300 μm, all of the evaluation items of thermal conductivity, transmittance, absorptance, handleability, and effective luminous flux were good. The evaluation results are described in more detail below.

In the sample of Example 39 that does not contain the thermally conductive powder, the transmittance, the absorptance, the handling and the effective light flux were evaluated as good, but the thermal conductivity was not evaluated as good. The sample of Example 40 contains _Al2O3 powder, which has a thermal conductivity higher than that of the phosphor. Therefore, the thermal conductivity of the sample of Example ₄₀ is higher than that of the sample of Example 39, but it was not evaluated as good.

In the sample according to Example 23, the thermally conductive powder is changed from _Al2O3 powder to AlN powder, as compared with the sample according to Example _40. Since the thermal conductivity of AlN is higher than that of _Al2O3 , the thermal conductivity of the sample according to Example ₂₃ is higher than that of Example 40, and is a good value.

Furthermore, all of the samples according to Examples 15 to 38, which contain AlN powder, had good thermal conductivity (>30 W/mK). Therefore, it was found that the thermal conductivity of the sample was good if the volume fraction of the AlN powder was at least 10 vol% or more.

In addition, among Examples 21 to 38 in which the volume fraction of the AlN powder was 30 vol% or more, the transmittance was less than 70% in the Examples in which the sample thickness was 360 μm, but the transmittance was good in the Examples in which the sample thickness was 300 μm or less.

Furthermore, among Examples 33 to 38 in which the volume fraction of the AlN powder is 50 vol%, the examples in which the sample thickness is 100 to 300 μm had an absorption rate of less than 75%, but the example in which the thickness is 360 μm showed good results in terms of absorption rate. Furthermore, in the examples in which the thickness is 100 to 300 μm, light leakage from the side surfaces of the sample was suppressed, and good results were obtained in terms of effective luminous flux.

Furthermore, in examples where the sample thickness was less than 120 μm, the mechanical strength was low and good results were not obtained in terms of handleability, but in examples where the thickness was 120 μm or more, the sample did not break even when handled with tweezers, and good results were obtained in terms of handleability.

[Light emitting module]
(Example 41)
In Example 41, the light-emitting module described with reference to Fig. 6 was produced. Specifically, a sintered body containing phosphor powder and AlN powder produced under the same conditions as the sample of Example 22 was used as an optical wavelength conversion layer, and the optical wavelength conversion layer was room temperature bonded to a sapphire mounting substrate so that the optical wavelength conversion layer covered the light emission surface of a blue LED (peak wavelength: 460 nm), thereby producing a white light-emitting module.

In Example 41, the chromaticity of the emitted color of the light-emitting module was within the chromaticity range suitable for headlamps, with chromaticity (cx, cy) = (0.32, 0.33). Therefore, in this example, by mounting a fluorescent material according to one embodiment of the present invention on a blue LED, it can be said that a white LED with excellent high-temperature characteristics suitable for specific applications (such as vehicle headlights) was produced.

Although the present invention has been described above with reference to the above-mentioned embodiments and examples, the present invention is not limited to the above-mentioned embodiments and examples, and suitable combinations and substitutions of the configurations of the embodiments and examples are also included in the present invention. Furthermore, it is possible to suitably rearrange the combinations and processing order in the embodiments and examples based on the knowledge of those skilled in the art, and to make modifications such as various design changes to the embodiments and examples, and embodiments with such modifications are also included in the scope of the present invention.

In the above embodiment, a sintered body was described as an example of a fluorescent member containing phosphor powder and thermally conductive powder. However, the present invention is not limited to this, and the fluorescent member may be, for example, a resin in which phosphor powder and thermally conductive powder are dispersed.

10 Light emitting module, 12 Mounting substrate, 14 LED, 16 Light wavelength conversion layer.

Claims (10)

A phosphor characterized by being represented by the general formula M _a Y _3-a-b Al _5-a/2 P _a/2 O ₁₂ :Ce _b (wherein M represents at least one element selected from the group consisting of Ba, Sr, Ca, and Mg, a satisfies 0<a≦1.5, and b satisfies 0<b≦0.12). The phosphor according to claim 1, characterized in that the crystal structure is a garnet type. The phosphor according to claim 1 or 2, characterized in that it is excited by blue light having a peak wavelength in the range of 430 to 480 nm and emits yellow light having a dominant wavelength in the range of 567 to 572 nm. The phosphor according to any one of claims 1 to 3, characterized in that it is excited by blue light having a peak wavelength in the range of 430 to 480 nm and emits light whose chromaticity coordinates (cx, cy) satisfy 0.414≦cx≦0.453 and 0.532≦cy≦0.558. A phosphor powder which is a powder of the phosphor according to any one of claims 1 to 4;
a thermally conductive powder, which is a powder of a material having a thermal conductivity higher than that of the phosphor;
A fluorescent member comprising: The fluorescent member according to claim 5, characterized in that the volume ratio of the phosphor powder to the thermally conductive powder is 90:10 to 60:40. The phosphor powder absorbs light having a peak wavelength of 450 nm,
The thickness of the fluorescent member is 0.12 to 0.30 mm.
7. The fluorescent member according to claim 5, wherein the transmittance of the fluorescent member for light having a wavelength of 550 to 600 nm is 70% or more. The phosphor powder absorbs blue light having a peak wavelength of 450 nm;
8. The fluorescent member according to claim 5, wherein the absorptance of the blue light of the fluorescent member is 75 to 85%. A fluorescent member comprising a resin transparent to visible light and the phosphor according to claim 1 encapsulated in the resin,
The phosphor is contained in the resin at 0.1 to 30 vol %;
The fluorescent member has a thickness of 0.01 to 5 mm. An LED that emits blue light with a peak wavelength in the range of 430 to 480 nm;
and a light wavelength conversion layer including the fluorescent member according to claim 5 , which is excited by the blue light emitted by the LED and emits yellow light,
A light-emitting module, characterized in that the emitted light color obtained by mixing the blue light and the yellow light has a chromaticity in the range surrounded by chromaticity coordinates (cx, cy) = (0.311, 0.339), (0.313, 0.342), (0.331, 0.354), (0.331, 0.338), (0.319, 0.315), and (0.311, 0.309).

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