JP7710328B2 - Phosphor, ceramic plate 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+c Si _a-2c P _c O ₁₂ :Ce _b (wherein M represents at least one element selected from the group consisting of Ba, Sr, Ca, and Mg; a and b are values included in the range surrounded by the lines represented by b = 0.1135a + 0.0754, b = 0.0816a + 0.02, a = 0.01, and b = 0.12; and c is a value satisfying 0≦c<a/2).

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 volume average particle size may be 1 to 30 μm.

a and c may satisfy the formulas a/c-2<8.0 and 0.01≦c≦0.16. This can reduce the amount of shift in the dominant wavelength when the phosphor is heated.

Yet 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 an optical wavelength conversion layer that is excited by the blue light emitted by the LED and emits yellow light. The optical wavelength conversion layer contains the above-mentioned phosphor. This light-emitting module emits light with a mixture of blue light and yellow light, and the chromaticity is 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 optical wavelength conversion layer may contain 0.1 to 30 vol% phosphor in a resin that is transparent to visible light, and may have a thickness of 0.01 to 5 mm. This makes it possible to realize a light-emitting module that achieves the desired light-emitting efficiency while producing light with a chromaticity in the above range.

The light wavelength conversion layer may be a ceramic plate having a thickness of 0.01 to 2.0 mm. This allows for the realization of a light emitting module whose emitted light has a chromaticity within the above range while achieving the desired light emitting efficiency.

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 emitted 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 amounts of Ba and Ce contained in the yellow phosphor according to the present embodiment and the dominant wavelength. FIG. 13 is a diagram showing the relationship between the amount of Ce charged (b) and the internal quantum efficiency (IQE). FIG. 1 is a graph showing the relationship between the amount of Ce charged (b) and the absorptance (Abs). FIG. 2 is a diagram showing preferred ranges of the amount of Ba (a) and the amount of Ce (b). 1 is a schematic diagram of a light-emitting module according to an embodiment of the present invention; 23 is a diagram for explaining the relationship between the chromaticity of the emitted color of the light-emitting modules according to Examples 19 to 21 and the thickness of the light wavelength conversion layer containing a yellow phosphor. FIG. 1 is a chromaticity diagram (CIE 1931) showing the chromaticity of the emitted color of a phosphor and a blue LED. FIG. 13 is a diagram showing the relationship between the amount of P and the shift amount of dominant wavelength in the phosphors according to Examples 22 to 26. FIG. 13 is a diagram showing the relationship between Si/P and the shift amount of dominant wavelength for each Ba content. A figure showing the light emission colors of the light-emitting modules of Examples 46 to 48.

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.

First Embodiment
[Phosphor]
The phosphor according to the present embodiment is a phosphor that is efficiently excited by blue light and emits light. Specifically, the phosphor 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. The phosphor according to the present embodiment has a garnet-type crystal structure, and is doped with an activator such as Ce ³⁺ ions to achieve yellow light emission.

Next, the phosphor according to the present embodiment will be described in detail. The phosphor according to the present embodiment is represented by the general formula Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ : Ce _b (where a and b are values included in the range surrounded by the straight lines b = 0.1135a + 0.0754, b = 0.0816a + 0.02, a = 0.01, and b = 0.12).

Figure 1 is a chromaticity diagram (CIE1931) 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), and (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.

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' investigations, 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.

The following provides a more detailed explanation using comparative examples and 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.

(Comparative Example 1)
The phosphor according to Comparative Example 1 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 Comparative 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 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.

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 mixed uniformly in a mortar. The mixture was then 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, the mixture was crushed in a mortar and the luminescence 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 λd of the phosphor according to Comparative Example 1 was 566.3 nm, and the luminous intensity maintenance rate (K) when the temperature was raised from 25°C to 200°C was evaluated to be 91.5%. In other words, the luminous intensity when the temperature was raised to 200°C decreased to 91.5% compared to the luminous intensity at 25°C. In addition, the internal quantum efficiency (IQE) was 95%, and the absorptance (Abs) of the yellow-emitting phosphor absorbing the blue light emitted by the LED was 80%, which is equivalent to the results of known phosphors.

The results of the light emission characteristics and temperature characteristics of the phosphors of each embodiment and each comparative example are summarized in Table 1. In Table 1, the results are listed in order from Comparative Example 2, which has the smallest amount of Ba. In Table 1, the dominant wavelength λd is marked with an O if it satisfies 567.4 nm≦λd≦570.6 nm, and marked with an X if it does not. In addition, the light emission intensity maintenance rate (K) is marked with an O if it is 90% or more, and marked with an X if it is less than 90%. In addition, the internal quantum efficiency (IQE) is marked with an O if it is 90% or more, and marked with an X if it is less than 90%. In addition, the absorptivity (Abs) is marked with an O if it is 80% or more, and marked with an X if it is less than 80%.

Example 1
The phosphor according to Example 1 is a phosphor represented _{by Ba0.05Y2.89Al4.95Si0.05} : _Ce3 ⁺ _0.06 . The phosphor was produced under the same conditions as in Comparative Example 1, except that the _raw material powders similar to those in Comparative Example 1 were weighed to have molar ratios of Ba=0.05, Y=2.89, Al=4.95, Si=0.05, and Ce=0.06, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the dominant wavelength of the phosphor of Example 1 was 569.0 nm, which is within the target wavelength range. In addition, the internal quantum efficiency was 97%, the absorptance was 84%, and the luminous intensity maintenance rate was 93.0%, exceeding the target values in all items, indicating improved performance compared to the phosphor of Comparative Example 1. The results are shown in Table 1.

The same luminescence characteristics were obtained for phosphors synthesized using raw materials mixed by liquid-phase mixing, such as the citrate sol-gel method, the hexamine method, and the urea method. Various methods can be used to manufacture the phosphor according to this embodiment. For example, when using the solid-phase method, the use of high-purity powder raw materials makes it difficult for impurities to be introduced, and mixing of the raw materials can be completed in a short time (about 10 minutes). Furthermore, when using the liquid-phase method, mixing at the atomic level is possible, making it possible to create phosphors with different compositions at the 1/100 mol level.

Example 2
The phosphor according to Example 2 is a phosphor represented _{by Ba0.05Y2.91Al4.95Si0.05} : _Ce3 ⁺ _0.04 . The phosphor was produced under the same conditions as in Comparative Example 1, except that the _raw material powders similar to those in Comparative Example 1 were weighed to have molar ratios of Ba = 0.05, Y = 2.91, Al = 4.95, Si = 0.05, and Ce = 0.04, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the dominant wavelength of the phosphor of Example 2 was 567.8 nm, which is within the target wavelength range. In addition, the internal quantum efficiency was 98%, the absorptance was 82%, and the luminous intensity maintenance rate was 95.0%, exceeding the target values in all items, indicating that the performance was improved over the phosphor of Comparative Example 1. The results are shown in Table 1.

Example 3
The phosphor according to Example 3 is a phosphor represented _{by Ba0.05Y2.87Al4.95Si0.05} : _Ce3 ⁺ _0.08 . The phosphor was produced under the same conditions as in Comparative Example 1, except that the _raw material powders similar to those in Comparative Example 1 were weighed to have molar ratios of Ba = 0.05, Y = 2.87, Al = 4.95, Si = 0.05, and Ce = 0.08, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the dominant wavelength of the phosphor of Example 3 was 570.5 nm, which is within the target wavelength range. In addition, the internal quantum efficiency was 97%, the absorptance was 85%, and the luminous intensity maintenance rate was 91.0%, exceeding the target values in all items, indicating improved performance compared to the phosphor of Comparative Example 1. The results are shown in Table 1.

(Examples 4 to 6)
The phosphors according to Examples 4 to 6 are represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.10, b = 0.04 (Example 4), 0.06 (Example 5), and 0.09 (Example 6). The phosphors were produced under the same conditions as in Comparative Example 1, except that the raw material powders similar to those in Comparative Example 1 were weighed out to achieve the desired molar ratio, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphors of Examples 4 to 6 achieved characteristics within the target range in all items, including dominant wavelength, internal quantum efficiency, absorptivity, and luminous intensity maintenance rate. The results are shown in Table 1.

(Examples 7 to 9)
The phosphors according to Examples 7 to 9 are represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.03, b = 0.03 (Example 7), 0.04 (Example 8), and 0.06 (Example 9). The phosphors were produced under the same conditions as in Comparative Example 1, except that the raw material powders similar to those in Comparative Example 1 were weighed out to achieve the desired molar ratio, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphors of Examples 7 to 9 achieved characteristics within the target range in all items, including dominant wavelength, internal quantum efficiency, absorptivity, and luminous intensity maintenance rate. The results are shown in Table 1.

(Examples 10 to 12)
The phosphors according to Examples 10 to 12 are represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.08, b = 0.03 (Example 10), 0.06 (Example 11), and 0.08 (Example 12). The phosphors were produced under the same conditions as in Comparative Example 1, except that the raw material powders similar to those in Comparative Example 1 were weighed out to achieve the desired molar ratio, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphors of Examples 10 to 12 achieved characteristics within the target range in all items, including dominant wavelength, internal quantum efficiency, absorptivity, and luminous intensity maintenance rate. The results are shown in Table 1.

(Examples 13 to 15)
The phosphors according to Examples 13 to 15 are represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.20, b = 0.04 (Example 13), 0.08 (Example 14), and 0.10 (Example 15). The phosphors were produced under the same conditions as in Comparative Example 1, except that the raw material powders similar to those in Comparative Example 1 were weighed out to achieve the desired molar ratio, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphors of Examples 13 to 15 achieved characteristics within the target range in all items, including dominant wavelength, internal quantum efficiency, absorptivity, and luminous intensity maintenance rate (K). The results are shown in Table 1.

(Examples 16 to 18)
The phosphors according to Examples 16 to 18 are represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.40, b = 0.06 (Example 16), 0.10 (Example 17), and 0.12 (Example 18). The phosphors were produced under the same conditions as in Comparative Example 1, except that the raw material powders similar to those in Comparative Example 1 were weighed out to achieve the desired molar ratio, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphors of Examples 16 to 18 achieved characteristics within the target range in all items, including dominant wavelength, internal quantum efficiency, absorptivity, and luminous intensity maintenance rate. The results are shown in Table 1.

(Comparative Example 2)
The phosphor according to Comparative Example 2 is a phosphor represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.01 and b = 0.02. Note that, except that the same raw material powders as those in Comparative Example 1 were weighed out to achieve the desired molar ratio, a phosphor was produced under the same conditions as those in Comparative Example 1, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphor of Comparative Example 2 had an internal quantum efficiency of 98%, which was within the target range, but did not achieve the target ranges for dominant wavelength, absorptance, or luminous intensity maintenance rate. The results are shown in Table 1.

(Comparative Example 3)
The phosphor according to Comparative Example 3 is a phosphor represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.01 and b = 0.04. Note that, except that the same raw material powders as those in Comparative Example 1 were weighed out to achieve the desired molar ratio, a phosphor was produced under the same conditions as those in Comparative Example 1, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphor of Comparative Example 3 had a dominant wavelength of 568.0 nm, an internal quantum efficiency (IQE) of 98%, and an absorptivity of 82%, which were within the target range for these items, but the luminous intensity maintenance rate was 87%, which was not within the target range. The results are shown in Table 1.

(Comparative Example 4)
The phosphor according to Comparative Example 4 is a phosphor represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.60 and b = 0.18. Note that a phosphor was produced under the same conditions as in Comparative Example 1, except that the same raw material powders as in Comparative Example 1 were weighed out to achieve the desired molar ratio, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphor of Comparative Example 4 achieved an absorption rate of 86%, which was within the target range, but did not achieve the target ranges for dominant wavelength, internal quantum efficiency, and luminous intensity maintenance rate. The results are shown in Table 1.

(Comparative Example 5)
The phosphor according to Comparative Example 5 is a phosphor represented by Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ :Ce _b , where a = 0.70 and b = 0.13. Note that a phosphor was produced under the same conditions as in Comparative Example 1, except that the same raw material powders as in Comparative Example 1 were weighed out to achieve the desired molar ratio, and the light emission characteristics and temperature characteristics were evaluated.

As a result, the phosphor of Comparative Example 5 had a dominant wavelength of 570.0 nm and an absorptance of 86%, which were within the target range for these characteristics, but the internal quantum efficiency was 87% and the luminous intensity maintenance rate was 89%, which were not within the target range for these characteristics. The results are shown in Table 1.

3 is a diagram showing the relationship between the amount of Ba and Ce charged in the yellow phosphor according to the present embodiment and the dominant wavelength. As shown in Table 1, the dominant wavelength λd of the phosphors according to Examples 3, 6, 15, and 18 is 570.6 nm, which is the upper limit of the target range, and the approximate straight line calculated based on the coordinates showing the charged amounts (a, b) of Ba and Ce in each of these Examples is the following formula L1.
Formula L1: b=0.1135a+0.0754

Similarly, the dominant wavelength λd of the phosphors of Examples 4, 7, 10, 13, and 16 is all 567.4 nm, which is the lower limit of the target range, and when an approximation line is calculated based on the coordinates indicating the Ba and Ce loading amounts (a, b) of each of these Examples, the following formula L1' is obtained.
Formula L1': b=0.0816a+0.02

If the amounts (a, b) of Ba and Ce are in the range between the two straight lines L1 and L1', the dominant wavelength λd is in the range of 567.4 nm≦λd≦570.6 nm. On the other hand, the phosphors according to Comparative Examples 1, 2, and 4, in which the amounts (a, b) of Ba and Ce are not in the range between the two straight lines L1 and L1', do not have a dominant wavelength λd in the range of 567.4 nm≦λd≦570.6 nm.

In addition, in the range enclosed by the straight lines of formula L1 and formula L1', the amount of Ce charged tends to increase as the amount of Ba charged increases. The reason for this is that in the phosphor according to this embodiment, the emission intensity on the short wavelength side near 530 nm tends to increase as the amount of Ba increases, which tends to shift the dominant wavelength to the short wavelength side. To alleviate this tendency, the amount of Ce charged is increased and multiple excitation is performed to increase the emission on the long wavelength side. As a result, the amount of Ce charged also increases as the amount of Ba charged increases.

Next, we consider the amount of Ce charged (b). Figure 4 shows the relationship between the amount of Ce charged (b) and the internal quantum efficiency (IQE).

As shown in Fig. 4, the phosphor according to Example 18, in which the Ce content (b) is 0.12 mol, has an internal quantum efficiency of 90%, and the characteristics are within the target range. On the other hand, the phosphor according to Comparative Example 5, in which the Ce content (b) is 0.13 mol, and the phosphor according to Comparative Example 4, in which the Ce content (b) is 0.18 mol, have an internal quantum efficiency of less than 90%, and the characteristics are not within the target range. Therefore, it is preferable that the Ce content (b) taking into account the internal quantum efficiency satisfies the following formula L2.
Formula L2: b≦0.12

In addition, as shown in FIG. 4, when the amount of Ce charged (b) is greater than 0.09 mol, the internal quantum efficiency drops sharply. When the amount of Ce charged (b) is 0.09 mol or more, it is believed that concentration quenching occurs. Therefore, from the viewpoint of internal quantum efficiency, it is more preferable that the amount of Ce charged (b) is less than 0.09 mol.

Figure 5 shows the relationship between the amount of Ce (b) and the absorptance (Abs). Since Ce is an element that absorbs blue light and emits yellow light, the absorptance increases as the amount of Ce is increased. For example, the absorptance of the phosphor according to Example 6 (b = 0.09) is 86%, which is the maximum value among the examples. On the other hand, even if the amount of Ce is further increased, the absorptance remains constant at 86%. This is thought to be because the absorption of blue light by Ce has reached saturation. In addition, when the amount of Ce is reduced, the absorptance of the phosphor according to Example 7 (b = 0.03) is 81%, and characteristics within the target range (≧80%) are obtained.

However, the absorptance of the phosphor of Comparative Example 2 (b = 0.02) was 78%, which did not achieve the target range of characteristics. This is thought to be due to an insufficient amount of Ce. Therefore, when the phosphor of Comparative Example 2 is combined with a blue LED to form a light-emitting module, a large amount of phosphor is required, which is thought to result in poor LED orientation. For these reasons, it is recommended that the amount of Ce (b) to be added, taking the absorptance into consideration, be greater than 0.02 mol.

Next, the amount (a) of Ba will be considered. As shown in Table 1, the luminous intensity maintenance rate of the phosphor according to Example 8 (a = 0.03, b = 0.04) is 94%, and the target range of characteristics is obtained. On the other hand, the amount of Ce (b = 0.04) is the same as that of the phosphor of Example 8, but the amount of Ba (a) is less than that of the phosphor of Example 8. The luminous intensity maintenance rate of the phosphor of Comparative Example 3 (a = 0.01) is 87%, and the target range of characteristics is not obtained. This is considered to be because when the amount of Ba (a) is as small as 0.01 mol, there is little effect of improving the luminous intensity maintenance rate by Ba being dissolved in solid solution. From the above, it is preferable that the amount of Ba (a) considering the luminous intensity maintenance rate satisfies the following L3.
Formula L3: a>0.01

Fig. 6 is a diagram showing the preferred ranges of the amount of Ba (a) and the amount of Ce (b). As shown in Fig. 6, the phosphor according to this embodiment is expressed by the general formula Ba _a Y _3-a-b Al _5-a Si _a O ₁₂ : Ce _b (where a and b are values included in the range surrounded by the straight lines b = 0.1135a + 0.0754, b = 0.0816a + 0.02, a = 0.01, and b = 0.12).

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 for a desired application 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. 7 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 an optical 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 optical wavelength conversion layer 16 is a silicone resin transparent to visible light in which the yellow phosphor according to the present embodiment is dispersed. The optical 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. The mean volume diameter (MV) of the yellow phosphor may be 1 to 30 μm.

This light-emitting module 10 includes an optical wavelength conversion layer 16 that is excited by the blue light emitted by the LED 14 and emits yellow light. The optical wavelength conversion layer 16 contains the above-mentioned phosphor. This light-emitting module 10 emits light with a color obtained by mixing blue light and yellow light, and the chromaticity is 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 makes it possible to realize a light-emitting module 10 that achieves the desired light-emitting efficiency while emitting light with a chromaticity in the range suitable for the headlamp described above.

The optical wavelength conversion layer 16 may be a ceramic plate having a thickness of 0.01 to 2.0 mm. This ceramic plate is transparent to visible light and is obtained by pressure molding a phosphor and then vacuum or pressure firing. The light-emitting module 10 may have the LED 14 and the optical wavelength conversion layer 16 bonded at room temperature.

The following describes the emission characteristics of white light-emitting modules that combine the phosphors of Examples 1, 4, and 6 with a blue LED to obtain yellow light of the desired dominant wavelength and have emission intensity maintenance rates, internal quantum efficiency, and absorptance within the target ranges. Figure 8 is a diagram for explaining the relationship between the chromaticity of the emission color of the light-emitting modules of Examples 19 to 21 and the thickness of the light wavelength conversion layer containing the yellow phosphor.

(Example 19)
5 g of the phosphor (λd=569.0 nm) according to Example 1, 0.5 wt% TEOS (tetraethoxysilane), and 50 g of φ1 mm alumina balls were placed in a 100 ml polypot and rotated for 24 hours, then removed to a fluororesin-coated aluminum tray and dried by heating. The dried product was loosened using a nylon 50 mesh pass, weighed out at 1 g each, placed in a φ20 mm mold, molded at 10 MPa, and further molded at 98 MPa using CIP (Cold Isostatic Pressing).

The molded product was heated in a vacuum furnace at 1× ^10-3 Pa, 1750°C, and 24 hours, and further heated in HIP (Hot Isostatic Pressing) at 196 MPa, 1650°C, and 2 hours to obtain a transparent sintered body (transparent ceramic plate) with a thickness of about 1 mm. The transparent sintered body was polished to an arbitrary thickness by mirror polishing, cut into pieces of 1 mm square, and bonded at room temperature onto a blue LED chip to produce a light-emitting module according to Example 19 that realizes white light.

In the light-emitting module according to Example 19, when the thickness of the transparent sintered body, which is the light wavelength conversion layer, is 0.10 mm (the leftmost mark among the five chromaticity coordinates included in Example 19 in FIG. 8), 0.12 mm, 0.18 mm, 0.25 mm, or 0.30 mm (similarly the rightmost mark), the chromaticity of the light-emitting color (the light-emitting color obtained by mixing blue light and yellow light) of the light-emitting module falls within the desired chromaticity range R1 suitable for a headlamp. Note that instead of a transparent ceramic plate, a transparent resin in which phosphor is dispersed may also be used as the light wavelength conversion layer.

(Example 20)
A light-emitting module according to Example 20 was produced by the same manufacturing method as in Example 19, except that the phosphor (λd=567.4 nm) according to Example 4 was used. In the light-emitting module according to Example 20, when the thickness of the transparent sintered body was 0.10 mm (the left mark of the two chromaticity coordinates included in Example 20 in FIG. 8 ) and 0.15 mm (similarly the right mark), the chromaticity of the emitted color of the light-emitting module fell within the desired chromaticity range R1 suitable for a headlamp.

(Example 21)
A light-emitting module according to Example 21 was produced by the same method as in Example 19, except that the phosphor (λd=570.5 nm) according to Example 6 was used. In the light-emitting module according to Example 21, when the thickness of the transparent sintered body was 0.15 mm (the leftmost mark among the three chromaticity coordinates included in Example 21 in FIG. 8), 0.20 mm, or 0.30 mm (similarly the rightmost mark), the chromaticity of the emitted color of the light-emitting module fell within the desired chromaticity range R1 suitable for a headlamp.

Second Embodiment
[background]
Cerium (Ce ³⁺ ), which is the luminescent ion of a phosphor in which Ba and Si are dissolved in a YAG phosphor (hereinafter also referred to as "BS-YAG phosphor"), forms a dodecahedral structure factor (Ce site) with oxygen (O) in the crystal. The Ce site shares edges with a SiO ₄ tetrahedron (side length 1.60 Å) or an AlO ₄ tetrahedron (side length 1.74 Å) at two points.

In the crystal of the BS-YAG phosphor, in the AlO ₄ tetrahedron formed by Al and O, and in the SiO ₄ tetrahedron formed by Si and O, the bond between Al and O (Al-O) and the bond between Si and O (Si-O) are equivalent. Therefore, the positions of Al and Si are fixed, and a strong tetrahedral unit is formed. Since this tetrahedral unit vibrates as a strong tetrahedron when the temperature rises, the Ce sites sharing the edges are subjected to large lattice vibration, which is presumed to result in a shift in the dominant wavelength.

By replacing the Si (ionic radius 0.26 Å) of this SiO ₄ tetrahedron with phosphorus (P) (ionic radius 0.17 Å) having a smaller ionic radius than Si, a PO ₄ tetrahedron (side length 1.48 Å) smaller than the SiO ₄ tetrahedron is formed. In the PO ₄ tetrahedron formed by P and O, one of the bonds (P-O) with four O coordinated to P forms a double bond. For this reason, the position of P is not equivalent to the four O, and P can vibrate (change position) in the PO ₄ tetrahedron. As a result, the influence of thermal vibration of the Ce site sharing the edge is reduced, and the present inventors have conceived the possibility of realizing a phosphor that can suppress the shift of the dominant wavelength.

[Phosphor]
In the second embodiment, a phosphor represented by the general formula M _a Y _3-a-b Al _5-a+c Si _a-2c P _c O ₁₂ :Ce _b (wherein M represents at least one element selected from the group consisting of Ba, Sr, Ca, and Mg, a and b are values included in the range surrounded by the lines represented by b=0.1135a+0.0754, b=0.0816a+0.02, a=0.01, and b=0.12, and c is a value satisfying 0≦c<a/2). Note that a>0 and b>0.

When the amount of Si in the above general formula according to this embodiment is not 0, a and c satisfy the relational expression a-2c>0 (i.e., a/2>c). When the amount of P increases (i.e., the value of c increases), the amount of Si decreases according to the increase. This achieves charge balance in the phosphor. In this embodiment, the value of a is 0.01<a<1.20. This makes it easier to achieve charge balance in the phosphor. In addition, it is preferable that the value of c is 0.01≦c≦0.16. Furthermore, when the molar ratio of Si to P is expressed as (a-2c)/c=a/c-2, this molar ratio is preferably 0<a/c-2<8.0. This reduces the amount of shift in the dominant wavelength of the phosphor. In addition, the value of b according to this embodiment is 0.02<b<0.12.

The phosphor according to this embodiment is a phosphor that emits light when excited by blue light. The phosphor may be, for example, a phosphor that is strongly excited by blue light with a peak wavelength in the range of 430 to 480 nm at 25°C and emits yellow light with a dominant wavelength in the range of 567 to 572 nm. The crystal structure of the phosphor according to this embodiment may be a garnet type with a space group of Ia3d. Furthermore, the volume average particle size of the powdered phosphor according to this embodiment may be, for example, 1 to 30 μm.

The phosphor according to this embodiment will be described below with reference to examples. In the following examples, the dominant wavelength at 200°C was measured for the prepared phosphor. The phosphor was evaluated by comparing the dominant wavelength shift amount (hereinafter also simply referred to as "shift amount"), which is the value obtained by subtracting the dominant wavelength at 25°C from the dominant wavelength at 200°C, with a target value.

The target value of the shift amount will be explained with reference to Figure 9. Figure 9 is a chromaticity diagram (CIE1931) showing the chromaticity of the emitted color of a phosphor and a blue LED. Range R1 shown in Figure 9 is the chromaticity range defined as white light for a specific application (vehicle headlights), and this range is the same as range R1 described with reference to Figure 1. Point C3 shown in Figure 9 is the chromaticity coordinate of an example of a blue LED with a peak wavelength in the range of 430 to 480 nm.

Here, let us assume that the dominant wavelength of the phosphor at 25°C is 569.0 nm, and that the chromaticity coordinates of that phosphor are point C4. Let us also assume that the dominant wavelength of that phosphor at 200°C is 570.5 nm, and that the chromaticity coordinates of that phosphor are point C5. In this case, the line connecting points C3 and C4 passes through the center of range R1. Also, the line connecting points C3 and C5 passes through the lower limit of range R1. Therefore, the target value for the shift amount is set to 1.5 nm (= 570.5 nm - 569.0 nm), and the goal is for the shift amount of the phosphor to be below this target value.

In the following examples, similar to the examples according to the first embodiment, the phosphors produced were evaluated for each of the target values of 90% for luminous intensity maintenance rate, 90% for internal quantum efficiency, and 80% for absorption rate.

(Example 22)
The phosphor according to Example 22 is a phosphor represented _{by Ba0.05Y2.89Al4.95Si0.05} : _Ce3 ⁺ _0.06 . In Example 22, a phosphor was produced under the same conditions as in Example 1, and the _light emission characteristics and temperature characteristics were evaluated.

In the phosphor of Example 22, the targets for the emission intensity maintenance rate, internal quantum efficiency, and absorptivity were achieved. However, in the phosphor of Example 22, the dominant wavelength at 25°C was 569.0 nm, and the dominant wavelength at 200°C was 570.5 nm. Therefore, in Example 22, the shift amount was 1.5 nm, and the target for the shift amount was not achieved.

The manufacturing conditions of the phosphors in the examples and the measurement results of their luminescence properties are summarized in Table 2.

(Example 23)
The phosphor according to Example 23 is a phosphor containing P. Specifically, the phosphor according to Example 23 is a phosphor expressed by Ba _a Y _3-a-b Al _5-a+c Si _a-2c P _c O ₁₂ :Ce _b , which satisfies a = 0.05, b = 0.06, and c = 0.01, that is, a phosphor expressed by Ba _0.05 Y _2.89 Al _4.96 Si _0.03 P _0.01 O ₁₂ :Ce _0.06 .

In Example 23, in addition to the raw materials used in Example 1 (BaCO ₃ , Y ₂ O ₃ , CeO ₂ , α-Al ₂ O ₃ , SiO ₂ ), AlPO ₄ (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was used as a raw material, and the molar ratios were measured to be Ba = 0.05, Y = 2.89, Al = 4.960, Si = 0.03, P = 0.010, and Ce = 0.06. Except for this, a phosphor was prepared under the same conditions as in Example 22, and the luminescence characteristics, temperature characteristics, and shift amount were evaluated.

In the phosphor of Example 23, the dominant wavelength at 25°C was 569.0 nm, and the dominant wavelength at 200°C was 570.0 nm. Therefore, in the phosphor of Example 23, the shift amount was 1.0 nm, which was 0.5 nm less than the phosphor of Example 22, in which no P was added. As a result, in Example 23, the shift amount was below the target value, and the target regarding the shift amount was achieved. In addition, in the phosphor of Example 23, the targets for the luminous intensity maintenance rate, internal quantum efficiency, and absorptance were also achieved.

(Example 24)
The phosphor according to Example 24 is a phosphor _{represented by Ba0.05Y2.89Al4.965Si0.02P0.015O12 : Ce0.06} . The phosphor was produced under the same conditions _as in Example 23, except that the raw material powders similar to those in Example 23 were weighed to have _the molar ratios of Ba=0.05, Y=2.89, Al=4.965, Si=0.02, P=0.015, and Ce=0.06, and the luminescence characteristics, temperature characteristics, and shift amount were evaluated.

In the phosphor of Example 24, the dominant wavelength at 25°C was 569.0 nm, and the dominant wavelength at 200°C was 569.5 nm. Therefore, in the phosphor of Example 24, the shift in the dominant wavelength was 0.5 nm, which was 0.5 nm less than that of the phosphor of Example 23.

(Example 25)
The phosphor according to Example 25 is a phosphor represented _{by Ba0.05Y2.89Al4.97Si0.01P0.02O12 : Ce0.06} . The phosphor was produced under the same conditions _as in Example ₂₃ , except that the raw material powders similar to those in Example 23 were weighed to have _the molar ratios of Ba=0.05, Y=2.89, Al=4.970, Si=0.01, P=0.020, and Ce=0.06, and the luminescence characteristics and temperature characteristics were evaluated.

For the phosphor of Example 25, the dominant wavelength at 25°C was 569.0 nm, and the dominant wavelength at 200°C was 570.0 nm. Therefore, for the phosphor of Example 25, the shift amount was 1.0 nm, and the target was achieved.

(Example 26)
The phosphor according to Example 26 is a phosphor represented _{by Ba0.05Y2.89Al4.975P0.025O12} : _Ce0.06 . In Example 26, a phosphor was produced under _the same conditions _as in Example 23, except that the molar ratios of Ba ₌ 0.05, Y=2.89, Al=4.975, Si=0.00, P=0.025, and Ce=0.06 were measured, and the light emission characteristics and temperature characteristics were evaluated.

In the phosphor of Example 26, the targets for the emission intensity maintenance rate, internal quantum efficiency, and absorptivity were achieved. However, in the phosphor of Example 26, the dominant wavelength at 25°C was 569.0 nm, and the dominant wavelength at 200°C was 570.5 nm. Therefore, in the phosphor of Example 26, the shift amount was 1.5 nm, and the target for the shift amount was not achieved.

(Examples 27, 31, 36, and 41)
In Examples 27, 31, 36, and 41, phosphors were produced under the same conditions as in Example 22, except that the raw material powders similar to those in Example 22 were weighed to have the molar ratios shown in Table 2, and the luminescence characteristics and temperature characteristics were evaluated. Therefore, in Examples 27, 31, 36, and 41, phosphors were produced without using raw materials containing P. In all of Examples 27, 31, 36, and 41, the shift amount was not less than 1.5 nm, and the target for the shift amount was not achieved. Note that, in the phosphors according to these Examples, the targets for the luminescence intensity maintenance rate, internal quantum efficiency, and absorptivity were achieved.

(Examples 28 to 30, 33 to 35, 38 to 40, 43 to 45)
In Examples 28 to 30, 33 to 35, 38 to 40, and 43 to 45, phosphors were produced under the same conditions as in Example 23, except that the raw material powders similar to those in Example 23 were weighed out to achieve the molar ratios shown in Table 2. For the phosphors according to all of the Examples, the shift amount was less than 1.5 nm, and the target for the shift amount was achieved. In addition, for the phosphors according to these Examples, the targets for the emission intensity maintenance rate, internal quantum efficiency, and absorptance were also achieved.

(Examples 32, 37, and 42)
In Examples 32, 37, and 42, phosphors were produced under the same conditions as in Example 23, except that the raw material powders similar to those in Example 23 were weighed to have the molar ratios shown in Table 2. In Examples 32, 37, and 42, the raw material powders were weighed so that the molar ratio of P to Si was smaller than in other Examples, specifically, the molar ratio of Si to P was 8.00. For the phosphors according to all of the Examples, the shift amount of the dominant wavelength was 1.5 nm, and the target for the shift amount was not achieved. Note that, for the phosphors according to these Examples, the targets for the luminous intensity maintenance rate, internal quantum efficiency, and absorptivity were achieved.

The above describes the manufacturing method and shift amount evaluation for the phosphors of Examples 22 to 45. The evaluation results of Examples 22 to 45 are described in more detail below.

As shown in Table 2, in all examples, the targets for luminous intensity maintenance rate, internal quantum efficiency, and absorptivity were achieved. The targets for these items were also achieved in Examples 22, 27, 31, 36, and 41, in which the phosphor did not contain P, and in Examples 32, 37, and 42, in which the molar ratio of P to Si was small.

Furthermore, among the examples in which the phosphor contains P, examples in which c satisfies 0.01≦c≦0.16 were evaluated as being good for the amount of shift in addition to the luminous intensity maintenance rate, internal quantum efficiency, and absorptance.

Among the examples in which the phosphor does not contain P, the composition of Example 22 (Ba = 0.05, Ce = 0.06) has a dominant wavelength of 569.0 nm at 25°C and the highest internal quantum efficiency, absorptivity, and luminous intensity maintenance rate. The relationship between the amount of P and the shift in the dominant wavelength is examined.

Figure 10 shows the relationship between the amount of P and the shift amount of the dominant wavelength in the phosphors of Examples 22 to 26. In all of Examples 22 to 26, Ba = 0.05 and Ce = 0.06. As shown in Figure 10, when P = 0.015 (Example 24), the shift amount was 0.4 nm, the smallest value among the shift amounts in Examples 22 to 26.

When the amount of P was increased from Example 24 to P = 0.02 (Example 25), the shift amount increased to 1.0 nm. When the amount of P was further increased to P = 0.025 and Si = 0.00 (i.e., Si/P = 0), the shift amount became 1.5 nm, and the target was not achieved. From the above, from the viewpoint of reducing the shift amount, c (i.e., the amount of P) in the above general formula of the phosphor is preferably less than 0.025, and more preferably less than 0.016.

Next, we will examine how the relationship between Si/P and shift amount changes depending on the Ba content.

Figure 11 shows the relationship between Si/P and the shift amount for each Ba content. In Figure 11, Si/P is plotted for examples with each Ba content (Ba = 0.05, 0.08, 0.10, 0.20, 0.40).

As shown in FIG. 11, regardless of the Ba content, in the range of Si/P from 0 to 1.33, the shift amount decreased as Si/P increased. Furthermore, in the range of Si/P from 0 to 8.0, the shift amount reached its minimum value when Si/P was 1.33. For example, in Example 24, the shift amount reached its minimum value of 0.4. As Si/P increased from 1.33, the shift amount increased, and when Si/P was 8.0, the shift amount reached 1.5 nm, failing to achieve the target. From the above, from the viewpoint of reducing the shift amount, it is preferable that Si/P is greater than 0, and less than 8.0.

[Light emitting module]
Even if the phosphor according to the second embodiment is used, it is possible to realize the light emitting module 10 with reference to Fig. 7. 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 an optical wavelength conversion layer 16.

The light wavelength conversion layer 16 contains the above-mentioned phosphor, and is excited by the blue light emitted by the LED 14 and has a wavelength of 430 to 480 nm to emit yellow light. Therefore, the light emitting module 10 can emit an emission color that is a mixture of the blue light emitted by the LED 14 and the yellow light emitted by the light wavelength conversion layer 16. The chromaticity of this emitted light may be in the range surrounded by the 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 allows the light emitting module 10 to emit light whose emission color has a chromaticity in the above-mentioned range suitable for the headlamp while achieving the desired light emitting efficiency.

The light wavelength conversion layer 16 may be configured by dispersing the yellow phosphor according to this embodiment in a silicone resin that is transparent to visible light. The light wavelength conversion layer 16 may contain, for example, 0.1 to 30 vol % of the phosphor. The thickness t of the light wavelength conversion layer 16 may be, for example, about 0.01 to 5 mm. The thickness may be in the range of 0.1 to 2 mm.

The optical wavelength conversion layer 16 may be a ceramic plate having a thickness of 0.01 to 5.0 mm. This ceramic plate may be transparent to visible light and is obtained by pressure molding a phosphor and then vacuum or pressure firing. The light-emitting module 10 may have the LED 14 and the optical wavelength conversion layer 16 bonded at room temperature.

(Example 46)
In Example 46, a light-emitting module was produced using the phosphor of Example 24. The phosphor of Example 46 was the phosphor that had the smallest shift amount among the above-mentioned Examples, and achieved the target values for the luminous intensity maintenance rate, internal quantum efficiency, and absorptance.

First, the phosphor according to Example 24 was placed in a φ20 mm × 1.5 mm mold and molded to obtain a molded product. The molded product was then fired at 1550°C for 4 hours, and further pressurized and fired at 50 MPa at 1500°C × 1 hour to produce a sintered body (ceramic plate). The sintered body was then processed into 1 mm square pieces, and the thickness of the sintered body was adjusted to 0.3 mm by polishing the sintered body. The light-emitting module according to Example 46 that realizes white light was produced by bonding this sintered body to a blue LED chip at room temperature as a light wavelength conversion layer, and the light-emitting color of the light-emitting module was measured.

(Examples 47 and 48)
In Examples 47 and 48, light-emitting modules were produced in the same manner as in Example 46 except that the thicknesses of the optical wavelength conversion layers were 0.1 and 0.05 mm, respectively, and the light emission colors of the light-emitting modules were measured.

Figure 12 is a diagram showing the emission colors of the light-emitting modules according to Examples 46 to 48. The square marks shown in Figure 12 are the chromaticity coordinates of the emission colors of the light-emitting modules according to Examples 46 to 48 at 25°C. The triangular marks shown in Figure 12 are the chromaticity coordinates of the emission colors of the light-emitting modules according to Examples 46 to 48 at 200°C.

As shown in Figure 12, the chromaticity coordinates of the emitted colors of Examples 46 to 48 at 25°C all fell within the desired chromaticity range R1 suitable for headlamps. More specifically, these chromaticity coordinates passed through approximately the center of range R1 and varied on a straight line connecting the chromaticity coordinates of the phosphor and the chromaticity coordinates of the blue LED.

In addition, the chromaticity coordinates of the emitted colors of Examples 46 to 48 at 200°C all fell within the desired chromaticity range R1 suitable for headlamps. More specifically, these chromaticity coordinates passed inside range R1 rather than the lower limit, and varied on a straight line connecting the chromaticity coordinates of the phosphor and the chromaticity coordinates of the blue LED.

From Examples 46 to 48, it can be said that by adding P to BS-YAG, it is possible to realize a white LED that increases the light emission intensity maintenance rate when the temperature is raised from 25°C to 200°C while reducing the amount of shift in the dominant wavelength.

[Method of manufacturing phosphor using liquid phase method]
In the above embodiment, a method for manufacturing a phosphor by a solid phase method using a raw material powder has been mainly described. The method for manufacturing a phosphor is not limited to the solid phase method, and the phosphor may be manufactured by, for example, a liquid phase method. For example, the phosphor may be manufactured by a liquid phase method such as a citric acid sol-gel method, a hexamine method, or a uric acid method.

(Example 49)
In Example 49, a phosphor having the same composition as the phosphor of Example 24 was produced by utilizing a citric acid sol-gel method.

First, yttrium nitrate hexahydrate was prepared as a 1 mol/l yttrium nitrate aqueous solution, barium acetate was prepared as a 1 mol/l aqueous solution, cerium nitrate hexahydrate was prepared as a 1 mol/l cerium nitrate aqueous solution, and water-soluble silica was prepared as a 1 mol/l aqueous solution. In addition, trimethyl phosphate was prepared as a 0.5 mol/l aqueous solution, and citric acid was prepared as a 2 mol/l aqueous solution.

4.502 g of aluminum nonahydrate was placed in a 100 ml beaker, and 6.98 ml of the prepared yttrium nitrate aqueous solution, 0.12 ml of the prepared barium acetate aqueous solution, 0.05 ml of the prepared water-soluble silica aqueous solution, 0.07 ml of the prepared trimethyl phosphate dihydrate, and 38.7 ml of the prepared citric acid aqueous solution were added to obtain a mixed aqueous solution.

The resulting mixed aqueous solution was heated to 80°C and stirred at a stirring speed of 400 rpm for 1 hour. Next, while the mixed aqueous solution was being stirred, 5.7 ml of propylene glycol was added to the mixed aqueous solution, and the mixed aqueous solution was heated to 130°C. After the mixed aqueous solution was heated to 130°C, stirring was stopped and the mixed aqueous solution was maintained in that state for 6 hours to synthesize a gel-like substance (citric acid ester).

With the gel-like substance in the beaker, the beaker was placed in an electric furnace and the gel-like substance was heated at 500°C for 2 hours. This caused the gel-like substance to decompose, and an ashed substance (hereinafter also referred to as "ashed material") was synthesized. This ashed material was placed in an alumina crucible and heated in air at 800°C for 12 hours to decarbonize the ashed material, synthesizing approximately 1.5 g of phosphor raw material powder.

[supplement]
Although the present invention has been described above with reference to the above-mentioned embodiment and each example, the present invention is not limited to the above-mentioned embodiment and each example, and suitable combinations and substitutions of the configurations of the embodiment and each example are also included in the present invention. In addition, it is possible to suitably rearrange the combinations and processing order in the embodiment and each example based on the knowledge of a person skilled in the art, and to add modifications such as various design changes to the embodiment and each example, and the embodiment with such modifications can also be included in the scope of the present invention.

In the above first and second embodiments, an example has been described in which M in the general formula M _a Y _3-a-b Al _5-a+c Si _a-2c P _c O ₁₂ :Ce _b is Ba. However, without being limited thereto, M may be another alkaline earth metal such as Sr, Ca or Mg, or may be a combination of two or more elements selected from the group consisting of Ba, Sr, Ca and Mg.

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

Claims (7)

The general formula is M _a Y _3-a-b Al _5-a+c Si _a-2c P _c O ₁₂ : Ce _b (wherein M represents at least one element selected from the group consisting of Ba, Sr, Ca, and Mg; a and b are values included in the range surrounded by the lines represented by b = 0.1135a + 0.0754, b = 0.0816a + 0.02, a = 0.01, and b = 0.12; and c is a value satisfying 0 ≦ c < a/2) ,
A phosphor characterized in that a and c satisfy the formulae a/c-2<8.0 and 0.01≦c≦0.16 . 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 the volume average particle size is 1 to 30 μm. an LED that emits blue light with a peak wavelength in the range of 430 to 480 nm;
a light wavelength conversion layer that is excited by the blue light emitted by the LED and emits yellow light;
The light wavelength conversion layer comprises the phosphor according to claim 1 ,
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). 6. The light emitting module according to claim 5 , wherein the optical wavelength conversion layer contains 0.1 to 30 vol % of the phosphor in a resin that is transparent to visible light, and has a thickness of 0.01 to 5 mm. 6. The light-emitting module according to claim 5 , wherein the optical wavelength conversion layer is a ceramic plate having a thickness of 0.01 to 2.0 mm.