JP7345141B2 - Phosphors and light emitting devices using them - Google Patents

Description

The present invention relates to a phosphor that absorbs blue excitation light and emits red fluorescence, and a light emitting device using this phosphor.

Semiconductor light emitting devices such as light emitting diodes (hereinafter referred to as LEDs) have the advantages of being small, consuming little power, and being able to stably emit light with high brightness, and have become an alternative to lighting equipment such as incandescent lamps. 2. Description of the Related Art Many lighting fixtures are used that use light emitting devices made of LEDs that emit white light. As an LED that emits white light, for example, a combination of a blue LED and a Ce-activated YAG-based yellow phosphor represented by the composition formula Y ₃ Al ₅ O ₁₂ :Ce is known.

In the light emitting device with the above configuration, by coating the blue LED element with Ce-activated YAG phosphor, white light is achieved by mixing the blue light of the LED with the yellow light emitted from the Ce-activated YAG phosphor. . However, in this configuration, a bluish-white color develops due to the emission characteristics of the Ce-activated YAG phosphor. In store display lighting, medical field lighting, etc., a warm white color with a slight reddish tinge is required, and it is not suitable for emitting warm white light. For this reason, there is a need for a red phosphor that absorbs blue light and fluoresces red. Similar requirements apply not only to LEDs but also to light sources using laser diodes (LDs) used in projectors and the like.

As a general red phosphor, for example, in Patent Document 1, in addition to a blue LED and a Ce-activated YAG-based phosphor, an Eu-activated nitride phosphor having a composition formula of Ca ₂ Si ₅ N ₇ :Eu is further described. A light emitting device is disclosed that can emit reddish warm white color by combining the two.

Since the phosphor shown in Patent Document 1 has a peak wavelength of 600 nm or more, due to such a configuration, it exhibits a high color rendering index (Ra) at a color temperature in the bulb color range of 3,250 K or less, and particularly in red It becomes possible to provide a light-emitting device that emits white light with an excellent special color rendering index (R9) that indicates how the image appears.

Japanese Patent Application Publication No. 2003-321675

However, the phosphor of Patent Document 1 has the following problems. For example, when trying to realize a high-brightness, high-color-rendering light source by applying a high-output excitation light source such as a blue LD as an excitation light source, the phosphor described in Patent Document 1 activates Eu, which has a short luminescence lifetime, as the luminescence center. Therefore, under a high-output light source, the luminance cannot be increased due to brightness saturation, making it difficult to increase the output. Luminance saturation is a phenomenon in which the luminance of light emitted from a phosphor is not proportional to the output of a light source, and it is known that the longer the luminescence lifetime of a luminescent element, the more likely luminance saturation occurs. In the case of the aforementioned Ce-activated YAG-based phosphor, brightness saturation is less likely to occur because Ce has a longer luminescence lifetime than Eu. Further, the parent phase in which Eu is activated in Patent Document 1 is a nitride phosphor, and the manufacturing process thereof, especially the management of the firing step for performing the synthesis reaction, is complicated and costs tend to be high. For example, when Si ₃ N ₄ is used as a raw material, it is thermally decomposed at high temperatures, so a furnace with a high pressure environment is required during firing. Additionally, firing may be performed in an atmosphere of ammonia or the like, which can be a dangerous process. On the other hand, oxide phosphors do not require a high-pressure environment and can be synthesized in the atmosphere, depending on the material used. However, since the normal Ce-activated YAG phosphor has an emission peak wavelength around 550 nm, it cannot be used as is.

The present invention solves these conventional problems, and is capable of exhibiting high color rendering properties with little reduction in luminance due to luminance saturation under a high-output light source, as well as a light emission peak wavelength of 600 nm or more and 700 nm or less. An object of the present invention is to provide a Ce-activated oxide phosphor shown in FIG.

The phosphor according to the present disclosure is
The following composition formula (1)
Y _3-x-z A _{x Cez} Al _5-y Li _y O ₁₂ ...(1)
Contains a material with a garnet-type crystal structure represented by
A is any one of Yb, Eu, La,
x, y and z in formula (1) are the composition ratio of A, the composition ratio of Li, and the composition ratio of Ce, respectively,
x and y simultaneously satisfy x≦2.7 and 2.5≦y≦x+1.8,
The characteristic is that z is in the range of 0<z≦0.15.

Further, the light emitting device according to the present invention includes:
the phosphor; a light source having an emission peak wavelength of 400 nm or more and 500 nm or less;
It is characterized by having the following.

According to the phosphor according to the present invention, since its emission peak wavelength is 600 nm or more and 700 nm or less, it exhibits high color rendering properties in the long wavelength region within the visible light region. Furthermore, since Ce is used, there is little reduction in luminance due to luminance saturation under irradiation with a high-power light source. Therefore, in combination with a light source that emits blue light having an emission peak wavelength of 450 nm, for example, a light emitting device with high brightness and high color rendering can be obtained. Furthermore, since an oxide is used as the matrix for activating Ce, it is possible to provide a phosphor with reduced manufacturing costs without using a complicated process.

1 is a schematic diagram of a crystal structure of a phosphor host crystal according to Embodiment 1. FIG. FIG. 3 is a diagram showing a composition range in which the emission peak wavelength is 600 nm or more in Embodiment 1. 1 is a schematic diagram of an LED light emitting device according to Embodiment 1. FIG. 1 is a schematic diagram of an LD light emitting device according to Embodiment 1. FIG. FIG. 7 is a diagram showing a composition range in which the emission peak wavelength is 600 nm or more in Embodiment 2. FIG. 7 is a diagram showing a composition range in which the emission peak wavelength is 600 nm or more in Embodiment 3. Table 1 shows a list of x, y, z values and emission peak wavelengths in compositional formula (2) of Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-4. Table 2 shows a list of x, y, z values and emission peak wavelengths of compositional formula (3) of Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-4. Table 3 shows a list of x, y, z values and emission peak wavelengths of compositional formula (4) of Examples 3-1 to 3-12 and Comparative Examples 3-1 to 3-3.

The phosphor according to the first aspect has the following composition formula (1)
Y _3-x-z A _{x Cez} Al _5-y Li _y O ₁₂ ...(1)
Contains a material with a garnet-type crystal structure represented by
A is any one of Yb, Eu, La,
x, y and z in formula (1) are the composition ratio of A, the composition ratio of Zn, and the composition ratio of Ce, respectively,
x, y, and z are x≦2.7, 2.5≦y≦x+1.8, and
The range is 0<z≦0.15.

In the phosphor according to the second aspect, in the first aspect, the A is Yb,
The x and y may be 1.2≦x≦2.7, 2.5≦y≦x+1.8.

In the phosphor according to a third aspect, in the first aspect, the A is Eu,
The x and y may be 1.2≦x≦2.7, 2.5≦y≦x+1.8.

In the phosphor according to a fourth aspect, in the first aspect, the A is La;
The x and y may be x≦2.7, 2.5≦y≦x+1.8.

A light emitting device according to a fifth aspect includes the phosphor according to any one of the first to fourth aspects;
a light source having an emission peak wavelength of 400 nm or more and 500 nm or less;
It is equipped with

Hereinafter, phosphors and light emitting devices according to embodiments of the present disclosure will be described with reference to the drawings. Note that common constituent elements in each figure are designated by the same reference numerals, and their descriptions will be omitted as appropriate.

First, the features of the phosphor of the present invention that are common to each embodiment will be explained.

The optical properties of a phosphor are determined by the type of host crystal and luminescent center. For example, Y ₃ Al ₅ O ₁₂ :Ce, which is generally known as a yellow phosphor, has a garnet structure crystal belonging to the cubic system as a parent crystal, and the luminescent center is Ce. FIG. 1 shows a schematic diagram of this garnet type crystal 1. Among the sites constituting the garnet-type crystal 1, the oxygen ions of the O site 4 are coordinated with the cations entering the Y site 2 and the Al site 3, and the Y site 2 has a dodecahedral coordination, and the Al site 3 has a dodecahedral coordination. There are two types of coordination: octahedral coordination and tetrahedral coordination. In this embodiment as well, the mother crystal is a Y ₃ Al ₅ O ₁₂ type crystal having a garnet structure, and a part of Y site 2 in FIG. 1 is replaced with Ce, and Y site 2 and Al site 3 are replaced with Ce. The phosphor is partially substituted with another element. Note that Ce, which is the center of luminescence, is not shown because the total amount added is very small and it does not exist in all crystal lattices. By replacing part of Y site 2 and Al site 3, the crystal field around Ce, which is the luminescent center, changes. Then, the 5d orbital of Ce is split, the bandgap of Ce becomes smaller, and the emission wavelength shifts to the longer wavelength side.

Common elements in each of these embodiments can be represented by the following compositional formula (1).
In other words, the phosphor of the present disclosure is
Y _3-x-z A _{x Cez} Al _5-y Li _y O ₁₂ ...(1)
Contains a material having a garnet-type crystal structure represented by the composition formula (1),
A is any one of Yb, Eu, La,
x≦2.7, 2.5≦y≦x+1.8, and
It is characterized in that 0<z≦0.15.

In the above, x≦2.7 because the maximum possible composition ratio of Y site 2 as a garnet structure is 3, so if the composition ratio of A that replaces Y site 2 exceeds 2.7, This is because it is thought that the crystal becomes unstable.
In addition, y≧2.5 is because if the composition ratio of Si that replaces the Al site 3 is less than 2.5, the effect of the crystal field on Ce, which is the luminescent element shown above, becomes smaller and the luminescence peak This is because the influence on the wavelength is also reduced.
Furthermore, the reason why 0<z≦0.15 is satisfied is that in order to obtain light emission, it is necessary to include Ce, so the value of z is larger than 0. The value of z is preferably 0.0001 or more, more preferably 0.003 or more from the viewpoint of increasing the emission intensity. There is no particular restriction on the maximum value of z as long as the phosphor can emit light. However, when the value of z becomes too large, the emission intensity decreases due to concentration quenching. Therefore, by setting the value of z to 0.15 or less, it is possible to suppress a decrease in the emission intensity. Further, the value of z is desirably 0.1 or less from the viewpoint of increasing the emission intensity.

(Embodiment 1)
<Phosphor>
The phosphor according to Embodiment 1 has the following compositional formula (2)
Y _3-x-z Yb _{x Cez} Al _5-y Li _y O ₁₂ ...(2)
Contains a material with a garnet-type crystal structure represented by
x, y, and z in formula (2) are the composition ratio of Yb, the composition ratio of Li, and the composition ratio of Ce, respectively,
x and y simultaneously satisfy 1.2≦x≦2.7 and 2.5≦y≦x+1.8,
z is in the range of 0<z≦0.15.

In compositional formula (2), the value of z is greater than 0 because it is necessary to include Ce in order to obtain light emission. The value of z is preferably 0.0001 or more, more preferably 0.003 or more from the viewpoint of increasing the emission intensity. There is no particular restriction on the maximum value of z as long as the phosphor can emit light. However, when the value of z becomes too large, the emission intensity decreases due to concentration quenching. Therefore, by setting the value of z to 0.15 or less, it is possible to suppress a decrease in the emission intensity. Further, the value of z is desirably 0.1 or less from the viewpoint of increasing the emission intensity.

According to the phosphor according to Embodiment 1, it has a garnet-type crystal structure represented by the above compositional formula (2), and its emission peak wavelength is from 600 nm to 700 nm. Shows high color rendering properties in the wavelength range. Furthermore, since Ce is used, there is little reduction in luminance due to luminance saturation under irradiation with a high-power light source.

<Method for manufacturing phosphor>
Hereinafter, a method for manufacturing a phosphor material according to Embodiment 1 will be described.
(1) Raw materials include yttrium (Y), ytterbium (Yb), cerium (Ce), aluminum (Al), and lithium (Li), including yttrium oxide, ytterbium oxide, cerium oxide, aluminum oxide, and lithium oxide. Prepare. The raw materials do not have to be these oxides, but can also be metal salt compounds such as carbonates.
(2) Measure a predetermined amount of the powder of the raw material and mix thoroughly. The mixing method may be wet mixing in a solution or dry mixing of dry powders. Industrially used ball mills, medium stirring mills, planetary mills, vibration mills, jet mills, stirrers, etc. can be used. It is also possible to mix barium fluoride (BaF ₂ ) or strontium fluoride (SrF ₂ ) as a flux in an amount equivalent to 0.1% to 10% by weight of the mixed powder. The effect of flux is that it melts during firing, promotes the diffusion of each raw material, and is used to increase reactivity.

(3) Next, the mixed powder prepared as described above is fired. An electric furnace can be used for firing. For example, the mixed powder is placed in an alumina crucible, and the whole alumina crucible is heated and fired at 1200° C. or more and 1700° C. or less for 2 hours or more and 12 hours or less.
(4) After firing, the powder of the phosphor material can be obtained through steps such as cooling, crushing, and flux cleaning with acid.
Through the above steps, a phosphor can be obtained.

<Evaluation of luminescence characteristics>
The emission spectra of Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-4 are measured using a spectrofluorometer using an integrating sphere. The synthesized phosphor is placed in a predetermined position within an integrating sphere, the powder is irradiated with blue light emitted from a blue LED light source attached to the measuring device, and the emission spectrum is measured to obtain the emission peak wavelength.

(Judgment criteria)
In the emission spectrum, those whose emission peak wavelength is 600 nm or more and 700 nm or less are considered to have excellent emission characteristics in the long wavelength region. A sample having an emission peak wavelength of less than 600 nm is graded ◎ as being excellent, and a sample having an emission peak wavelength of less than 600 nm is graded as poor as having insufficient light emission characteristics in the long wavelength region.

A list of x, y, z values and emission peak wavelengths of compositional formula (2) of Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-4 is shown in Table 1 of FIG. show.

As shown in Table 1 of FIG. 7, by adjusting the composition ratio of Yb and Li, the emission peak wavelengths of Examples 1-1 to 1-11 became 600 nm or more, and all evaluations were ◎ or ○. Become. This is because by replacing the Y site with Yb and the Al site with Li, the influence of the crystal field on Ce, which is a luminescent ion, has changed compared to the mother crystal, Y ₃ Al ₅ O ₁₂ crystal. It is believed that there is.

The emission peak wavelengths of Comparative Examples 1-1 to 1-4 are less than 600 nm, and the evaluation is x.

FIG. 2 is a diagram showing the relationship between the Yb composition ratio and the Li composition ratio at which the emission peak wavelength is 600 nm or more in the first embodiment. The horizontal axis is the Yb composition ratio, which corresponds to x in compositional formula (2). The vertical axis is the Li composition ratio, which corresponds to y in compositional formula (2). The solid circles represent locations where the emission peak wavelength is 600 nm or more in Examples 1-1 to 1-11. The x portion represents a portion where the emission peak wavelength is less than 600 nm in Comparative Examples 1-1 to 1-4.

As shown in FIG. 2, in the relationship between the Yb composition ratio x and the Li composition ratio y, there is a boundary where the emission peak wavelength is 600 nm or more. When approximating lines along this boundary are found, it is found that x≦2.7, y≧2.5, y≦x+1.8, and x≧1.2, respectively. In other words, if the Yb composition ratio x and the Li composition ratio y exist within the solid line region surrounded by the approximate line in FIG. 2, the emission peak wavelength will be 600 nm or more. That is, composition formula (2)
Y _3-x-z Yb _{x Cez} Al _5-y Li _y O ₁₂ ...(2)
In the formula (2), x, y, and z are the composition ratio of Yb, the composition ratio of Ce, and the composition ratio of Li, respectively, and x and y are If 1.2≦x≦2.7 and 2.5≦y≦x+1.8 are satisfied at the same time, and z is in the range of 0<z≦0.15, the emission peak wavelength will be 600 nm or more.

Here, the values of z in Table 1 of FIG. 7 and FIG. 2 are all fixed at 0.09. Since Ce is an element that is the center of luminescence, it has a large effect on luminance, but it has a small effect on the emission peak wavelength. Similar results can be obtained with both.

<Light-emitting device>
<LED light emitting device>
FIG. 3 is a schematic diagram of an example of the LED light emitting device 10 according to Embodiment 1 of the present disclosure. An LED light emitting device 10 including a phosphor 18 represented by compositional formula (2) and an LED chip 11 as a light source will be described below. FIG. 3 is a schematic diagram showing one embodiment of the LED light emitting device 10. As shown in FIG. 3, in the LED light emitting device 10, the LED chip 11 is fixed onto a support 12 via solder 13 so that the light emitting surface does not come into contact with the support 12. Further, the LED chip 11 is electrically connected to an electrode 15 arranged on the support 12 by a bonding wire 14. Further, the LED chip 11 is covered with an LED wavelength conversion member 16, and the LED wavelength conversion member 16 includes an LED sealing body 17, a red phosphor 18, a yellow phosphor 19, and a green phosphor 20.

The LED chip 11 is, for example, one that emits light in the ultraviolet to yellow region, and has an emission spectrum peak at a wavelength of 400 nm or more and 500 nm or less. Specifically, as the LED chip 11, a blue LED chip or the like is used.

In the first embodiment, since the LED light emitting device 10 has a structure that allows surface mounting, the support body 12 is a substrate. For example, a substrate having high thermal conductivity can be used as the support body 12 so that the heat generated by the LED chip 11 can be efficiently radiated to the outside. For example, a ceramic substrate made of alumina, aluminum nitride, or the like can be used as the support 12.

Silicone resin is used for the LED sealing body 17 in the LED wavelength conversion member 16. The silicone resin may include, for example, dimethyl silicone, which has high color fastness. Furthermore, methylphenyl silicone or the like having high heat resistance can also be used as the silicone resin. The silicone resin may be a homopolymer having a main skeleton formed by siloxane bonds defined by one type of chemical formula. Further, it may be a copolymer containing a structural unit having a siloxane bond defined by two or more types of chemical formulas, or an alloy of two or more types of silicone polymers.

The phosphor in the LED wavelength conversion member 16 wavelength-converts the light emitted from the LED chip 11 into light with a longer wavelength. The phosphor included in the LED wavelength conversion member 16 is composed of a mixture of a red phosphor 18 and at least one of a yellow phosphor 19 and a green phosphor 20. As the red phosphor 18, the phosphor according to Embodiment 1 can be used. As the yellow phosphor 19, for example, Y ₃ Al ₅ O ₁₂ :Ce, α-SiAlON:Eu, etc. can be used. Further, as the green phosphor 20, Ca ₃ SiO _{4 Cl2} :Eu, β-SiAlON:Eu, etc. can be used. In particular, in FIG. 3, a case will be described in which the LED wavelength conversion member 16 is configured by mixing three types of red phosphor 18, yellow phosphor 19, and green phosphor 20. The mixing ratio of the three types of phosphors can be adjusted as appropriate depending on the desired color tone of white light, the emission intensity of each phosphor, and the like. For example, the three types of phosphors, the red phosphor 18, the yellow phosphor 19, and the green phosphor 20, are added to the LED encapsulant at a ratio of 3 parts by weight or more and 70 parts by weight or less, based on 100 parts by weight of the encapsulant. Included in 17. When the content is less than 3 parts by weight, sufficient intensity of fluorescence cannot be obtained, so it may become impossible to realize the LED light emitting device 10 that emits light of a desired wavelength. The weight ratio of the three types of phosphors can be appropriately determined depending on the desired color tone of white light and the emission intensity of each phosphor.

Note that by combining the red phosphor 18 with a phosphor of another color, the LED light emitting device 10 can be constructed as an LED light emitting device 10 that emits a color other than white.

Yellow phosphor 19 and green phosphor 20 other than red phosphor 18 according to Embodiment 1 can be manufactured according to known methods.

<LD light emitting device>
FIG. 4 is a schematic diagram of an example of a light emitting device 30 according to Embodiment 1 of the present disclosure. An LD light emitting device 30 including the phosphor 18 having the compositional formula (2) and the LD element 31 as a light source will be described below. FIG. 4 is a schematic diagram showing one embodiment of the LD light emitting device 30. As shown in FIG. 4, the LD light emitting device 30 includes an LD element 31, an incident optical system 32, and an LD wavelength conversion member 33. Further, the LD wavelength conversion member 33 includes a binder 34, a red phosphor 18, a yellow phosphor 19, and a green phosphor 20 similar to those shown in FIG.

The LD element 31 can emit light with a higher optical power density than the LED. Therefore, by using the LD element 31, a high output light emitting device can be constructed. The optical power density of the LD element 31 is, for example, 0.5 W/mm ² or more from the viewpoint of increasing the output of the LD light emitting device 30. Further, the optical power density may be 2 W/mm ² or more, 3 W/mm ² or more, or 10 W/mm ² or more. On the other hand, if the optical power density is too high, the amount of heat generated from the phosphor irradiated with light increases, which may adversely affect the LD light emitting device 30. Therefore, the optical power density may be 150 W/mm ² or less, 100 W/mm ² or less, 50 W/mm ² or less, or 20 W/mm ² or less. .

The LD element 31 is, for example, one that emits light in the ultraviolet to yellow region, and has an emission spectrum peak at a wavelength of 400 nm or more and 500 nm or less. For example, an LD element that emits blue-violet light or an LD element that emits blue light can be used. In the first embodiment, a case will be described in which the LD element 31 emits blue light.

The binder 34 in the LD wavelength conversion member 33 is, for example, a medium such as resin, glass, or transparent crystal. The binder 34 may be made of a single material or may be made of different materials depending on the location.

The phosphor in the LD wavelength conversion member 33 wavelength-converts the light emitted from the LD element 31 into light with a longer wavelength. The phosphor of the LD wavelength conversion member 33 is composed of a mixture of a red phosphor 18 and at least one of a yellow phosphor 19 and a green phosphor 20. As the red phosphor 18, the phosphor of Embodiment 1 is used. As the yellow phosphor 19 and the green phosphor 20, those illustrated in FIG. 3 can be used. In particular, in FIG. 4, a case will be described in which the LD wavelength conversion member 33 is configured by mixing three types of red phosphor 18, yellow phosphor 19, and green phosphor 20. The mixing ratio of the three types of phosphors can be adjusted as appropriate depending on the desired color tone of white light, the emission intensity of each phosphor, and the like.

The blue light emitted from the LD element 31 passes through the incident optical system 32 and is converted into red light, yellow light, and green light by the red phosphor 18, yellow phosphor 19, and green phosphor 20 in the LD wavelength conversion member 33, respectively. is converted to The blue light emitted from the LD element 31 that was not absorbed by the three types of phosphors mentioned above, and the red, yellow, and green light converted by the red phosphor 18, yellow phosphor 19, and green phosphor 20, respectively. When mixed together, white light is produced.

As described above, since the light emitting device of FIGS. 3 and 4 uses the phosphor according to Embodiment 1, high color rendering and color reproducibility can be achieved when configured as a white light emitting device.

(Embodiment 2)
<Phosphor>
The phosphor according to Embodiment 2 has the following compositional formula (3)
Y _3-x-z Eu _{x Cez} Al _5-y Li _y O ₁₂ ...(3)
Contains a material with a garnet-type crystal structure represented by
x, y, and z in formula (3) are the composition ratio of Eu, the composition ratio of Li, and the composition ratio of Ce, respectively,
x and y simultaneously satisfy 1.2≦x≦2.7 and 2.5≦y≦x+1.8,
z is in the range of 0<z≦0.15.

In the second embodiment as well, the host crystal is a Y ₃ Al ₅ O ₁₂ type crystal having a garnet structure, and a phosphor is obtained in which part of the Y site 2 and Al site 3 in FIG. 1 are replaced. That is, the Y site is replaced with Eu and Ce, and the Al site is replaced with Li.

In compositional formula (3), the value of z is greater than 0 because it is necessary to include Ce in order to obtain light emission. The value of z is preferably 0.0001 or more, more preferably 0.003 or more from the viewpoint of increasing the emission intensity. There is no particular restriction on the maximum value of z as long as the phosphor can emit light. However, when the value of z becomes too large, the emission intensity decreases due to concentration quenching. Therefore, by setting the value of z to 0.15 or less, it is possible to suppress a decrease in the emission intensity. Further, the value of z is desirably 0.1 or less from the viewpoint of increasing the emission intensity.

<Method for manufacturing phosphor>
Hereinafter, a method for manufacturing a phosphor material according to Embodiment 2 will be described.
(1) Raw materials include yttrium (Y), europium (Eu), cerium (Ce), aluminum (Al), and lithium (Li), including yttrium oxide, europium oxide, cerium oxide, aluminum oxide, and lithium oxide. Prepare. The raw materials do not have to be these oxides, but can also be metal salt compounds such as carbonates.
(2) Measure a predetermined amount of the powder of the raw material and mix thoroughly. The mixing method may be wet mixing in a solution or dry mixing of dry powders. Industrially used ball mills, medium stirring mills, planetary mills, vibration mills, jet mills, stirrers, etc. can be used. It is also possible to mix barium fluoride (BaF ₂ ) or strontium fluoride (SrF ₂ ) as a flux in an amount equivalent to 0.1% to 10% by weight of the mixed powder. The effect of flux is that it melts during firing, promotes the diffusion of each raw material, and is used to increase reactivity.

(3) Next, the mixed powder prepared as described above is fired. An electric furnace can be used for firing. For example, the mixed powder is placed in an alumina crucible, and the whole alumina crucible is heated and fired at 1200° C. or more and 1700° C. or less for 2 hours or more and 12 hours or less.
(4) After firing, the powder of the phosphor material can be obtained through steps such as cooling, crushing, and flux cleaning with acid.
Through the above steps, a phosphor can be obtained.

<Evaluation of luminescence characteristics>
The emission spectra of Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-4 are measured using a spectrofluorometer using an integrating sphere. The synthesized phosphor is placed in a predetermined position within an integrating sphere, the powder is irradiated with blue light emitted from a blue LED light source attached to the measuring device, and the emission spectrum is measured to obtain the emission peak wavelength.

(Judgment criteria)
In the emission spectrum, those whose emission peak wavelength is 600 nm or more and 700 nm or less are considered to have excellent emission characteristics in the long wavelength region. A sample having an emission peak wavelength of less than 600 nm is graded ◎ as being excellent, and a sample having an emission peak wavelength of less than 600 nm is graded as poor as having insufficient light emission characteristics in the long wavelength region.

A list of x, y, z values and emission peak wavelengths of composition formula (3) of Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-4 is shown in Table 2 of FIG. show.

As shown in Table 2 of FIG. 8, by adjusting the composition ratio of Eu and Li, the emission peak wavelengths of Examples 2-1 to 2-11 became 600 nm or more, and all evaluations were ◎ or ○. Become. This is because by replacing the Y site with Eu and the Al site with Li, the influence of the crystal field on Ce, which is a luminescent ion, has changed compared to the mother crystal, Y ₃ Al ₅ O ₁₂ crystal. It is believed that there is.

The emission peak wavelengths of Comparative Examples 2-1 to 2-4 are less than 600 nm, and the evaluation is x.

FIG. 5 is a diagram showing the relationship between the Eu composition ratio and the Li composition ratio at which the emission peak wavelength is 600 nm or more in the second embodiment. The horizontal axis represents the Eu composition ratio, which corresponds to x in compositional formula (3). The vertical axis is the Li composition ratio, which corresponds to y in compositional formula (3). The solid circles represent locations where the emission peak wavelength is 600 nm or more in Examples 2-1 to 2-11. The x portion represents a portion where the emission peak wavelength is less than 600 nm in Comparative Examples 2-1 to 2-4.

As shown in FIG. 5, in the relationship between the Eu composition ratio x and the Li composition ratio y, there is a boundary where the emission peak wavelength is 600 nm or more. When approximating lines along this boundary are found, it is found that x≦2.7, y≧2.5, y≦x+1.8, and x≧1.2, respectively. In other words, if the Eu composition ratio x and the Li composition ratio y exist within the solid line region surrounded by the approximate line in FIG. 5, the emission peak wavelength will be 600 nm or more. That is, composition formula (3)
Y _3-x-z Eu _{x Cez} Al _5-y Li _y O ₁₂ ...(3)
In the formula (3), x, y, and z are the composition ratio of Eu, the composition ratio of Ce, and the composition ratio of Li, respectively, and x and y are If 1.2≦x≦2.7 and 2.5≦y≦x+1.8 are satisfied at the same time, and z is in the range of 0<z≦0.15, the emission peak wavelength will be 600 nm or more.

Here, the values of z in Table 2 of FIG. 8 and FIG. 5 are all fixed at 0.09. Since Ce is an element that is the center of luminescence, it has a large effect on luminance, but it has a small effect on the emission peak wavelength. Similar results can be obtained with both.

<Light-emitting device>
The light emitting device according to the second embodiment has the same configuration as the light emitting devices 10 and 30 according to the first embodiment shown in FIGS. 3 and 4 except for the red phosphor, so the description thereof will be omitted. However, as the red phosphor 18, the phosphor shown in Embodiment 2 is used.

(Embodiment 3)
<Phosphor>
The phosphor according to Embodiment 3 is
The following composition formula (4)
Y _3-x-z La _{x Cez} Al _5-y Li _y O ₁₂ ...(4)
Contains a material with a garnet-type crystal structure represented by
x, y, and z in formula (4) are the composition ratio of La, the composition ratio of Li, and the composition ratio of Ce, respectively,
x and y simultaneously satisfy x≦2.7 and 2.5≦y≦x+1.8,
z is in the range of 0<z≦0.15.

In the third embodiment as well, the host crystal is a Y ₃ Al ₅ O ₁₂ type crystal having a garnet structure, and a phosphor is obtained in which part of the Y site 2 and Al site 3 in FIG. 1 are replaced. That is, the Y site is replaced with La and Ce, and the Al site is replaced with Li.

In compositional formula (4), the value of z is greater than 0 because it is necessary to include Ce in order to obtain light emission. The value of z is preferably 0.0001 or more, more preferably 0.003 or more from the viewpoint of increasing the emission intensity. There is no particular restriction on the maximum value of z as long as the phosphor can emit light. However, when the value of z becomes too large, the emission intensity decreases due to concentration quenching. Therefore, by setting the value of z to 0.15 or less, it is possible to suppress a decrease in the emission intensity. Further, the value of z is desirably 0.1 or less from the viewpoint of increasing the emission intensity.

<Method for manufacturing phosphor>
Hereinafter, a method for manufacturing a phosphor material according to Embodiment 3 will be described.
(1) Raw materials include yttrium (Y), lanthanum (La), cerium (Ce), aluminum (Al), and lithium (Li), including yttrium oxide, lanthanum oxide, cerium oxide, aluminum oxide, and lithium oxide. Prepare. The raw materials do not have to be these oxides, but can also be metal salt compounds such as carbonates.
(2) Measure a predetermined amount of the powder of the raw material and mix thoroughly. The mixing method may be wet mixing in a solution or dry mixing of dry powders. Industrially used ball mills, medium stirring mills, planetary mills, vibration mills, jet mills, stirrers, etc. can be used. It is also possible to mix barium fluoride (BaF ₂ ) or strontium fluoride (SrF ₂ ) as a flux in an amount equivalent to 0.1% to 10% by weight of the mixed powder. The effect of flux is that it melts during firing, promotes the diffusion of each raw material, and is used to increase reactivity.

(3) Next, the mixed powder prepared as described above is fired. An electric furnace can be used for firing. For example, the mixed powder is placed in an alumina crucible, and the whole alumina crucible is heated and fired at 1200° C. or more and 1700° C. or less for 2 hours or more and 12 hours or less.
(4) After firing, the powder of the phosphor material can be obtained through steps such as cooling, crushing, and flux cleaning with acid.
Through the above steps, a phosphor can be obtained.

<Evaluation of luminescence characteristics>
The emission spectra of Examples 3-1 to 3-12 and Comparative Examples 3-1 to 3-3 are measured using a spectrofluorometer using an integrating sphere. The synthesized phosphor is placed in a predetermined position within an integrating sphere, the powder is irradiated with blue light emitted from a blue LED light source attached to the measuring device, and the emission spectrum is measured to obtain the emission peak wavelength.

(Judgment criteria)
In the emission spectrum, those whose emission peak wavelength is 600 nm or more and 700 nm or less are considered to have excellent emission characteristics in the long wavelength region. A sample having an emission peak wavelength of less than 600 nm is graded ◎ as being excellent, and a sample having an emission peak wavelength of less than 600 nm is graded as poor as having insufficient light emission characteristics in the long wavelength region.

A list of x, y, z values and emission peak wavelengths of compositional formula (4) of Examples 3-1 to 3-12 and Comparative Examples 3-1 to 3-3 is shown in Table 3 of FIG. show.

As shown in Table 3 of FIG. 9, by adjusting the composition ratio of La and Li, the emission peak wavelengths of Examples 3-1 to 3-11 became 600 nm or more, and all judgments were ◎ or ○. Become. This is because by replacing the Y site with Eu and the Al site with Li, the influence of the crystal field on Ce, which is a luminescent ion, has changed compared to the mother crystal, Y ₃ Al ₅ O ₁₂ crystal. It is believed that there is.

The emission peak wavelengths of Comparative Examples 3-1 to 3-4 are less than 600 nm, and the evaluation is x.

FIG. 6 is a diagram showing the relationship between the La composition ratio and the Li composition ratio at which the emission peak wavelength is 600 nm or more in the second embodiment. The horizontal axis is the La composition ratio, which corresponds to x in compositional formula (4). The vertical axis is the Li composition ratio, which corresponds to y in compositional formula (4). The solid circles represent locations where the emission peak wavelength is 600 nm or more in Examples 3-1 to 3-12. The x portion represents a portion where the emission peak wavelength is less than 600 nm in Comparative Examples 3-1 to 3-3.

As shown in FIG. 6, in the relationship between the La composition ratio x and the Li composition ratio y, there is a boundary where the emission peak wavelength is 600 nm or more. When approximating lines along this boundary are found, it is found that x≦2.7, y≧2.5, and y≦x+1.8, respectively. In other words, if the La composition ratio x and the Li composition ratio y exist within the solid line region surrounded by the approximate line in FIG. 6, the emission peak wavelength will be 600 nm or more. That is, composition formula (4)
Y _3-x-z La _{x Cez} Al _5-y Li _y O ₁₂ ...(4)
In the formula (4), x, y, and z are the composition ratio of La, the composition ratio of Ce, and the composition ratio of Li, respectively, and x and y are If x≦2.7 and 2.5≦y≦x+1.8 are satisfied at the same time, and z is in the range of 0<z≦0.15, the emission peak wavelength will be 600 nm or more.

Here, the values of z in Table 3 of FIG. 9 and FIG. 6 are all fixed at 0.09. Since Ce is an element that is the center of luminescence, it has a large effect on luminance, but it has a small effect on the emission peak wavelength. Similar results can be obtained with both.

<Light-emitting device>
The light-emitting device according to the third embodiment has the same configuration as the light-emitting devices 10 and 30 according to the first embodiment shown in FIGS. 3 and 4 except for the red phosphor, so a description thereof will be omitted. However, as the red phosphor 18, the phosphor shown in Embodiment 3 is used.

Note that the present disclosure includes appropriate combinations of any of the various embodiments and/or examples described above, and includes the combination of the various embodiments and/or examples described above. The effects of the embodiments can be achieved.

The phosphor according to the present invention is a red phosphor that has an emission peak wavelength in a range of 600 nm or more and 700 nm or less, emits a large amount of light in a long wavelength region, and can suppress a decrease in luminescence rate under irradiation with a high-power light source. When this phosphor is applied to a light source that emits blue light, a light emitting device with excellent color rendering properties can be constructed, and it can be suitably used as a light source for illumination or the like.

1 Garnet type crystal 2 Y site 3 Al site 4 O site 10 LED light emitting device 11 LED chip 12 Support 13 Solder 14 Bonding wire 15 Electrode 16 LED wavelength conversion member 17 LED sealing body 18 Red phosphor 19 Yellow phosphor 20 Green Phosphor 30 LD light emitting device 31 LD element 32 Incident optical system 33 LD wavelength conversion member 34 Binder

Claims (5)

The following composition formula (1)
Y _3-x-z A _{x Cez} Al _5-y Li _y O ₁₂ ...(1)
Contains a material with a garnet-type crystal structure represented by
A is any one of Yb, Eu, La,
x, y and z in formula (1) are the composition ratio of A, the composition ratio of Zn, and the composition ratio of Ce, respectively,
x, y, and z are x≦2.7, 2.5≦y≦x+1.8, and
In the range of 0<z≦0.15,
phosphor. Said A is Yb,
The phosphor according to claim 1, wherein the x and y are 1.2≦x≦2.7 and 2.5≦y≦x+1.8. Said A is Eu,
The phosphor according to claim 1, wherein the x and y are 1.2≦x≦2.7 and 2.5≦y≦x+1.8. The above A is La,
The phosphor according to claim 1, wherein the x and y are x≦2.7 and 2.5≦y≦x+1.8. The phosphor according to any one of claims 1 to 4,
a light source having an emission peak wavelength of 400 nm or more and 500 nm or less;
A light-emitting device equipped with.