JP7487816B2 - Light-emitting device and phosphor - Google Patents

Description

The present invention relates to an infrared-emitting phosphor and a light-emitting device including a semiconductor light-emitting element and an infrared-emitting phosphor.

2. Description of the Related Art Infrared light emitting diodes made of GaAs-based compound semiconductors are known as light emitting devices that emit infrared light, and infrared light emitting diodes are widely used in the field of sensors and the like.
However, GaAs-based compound semiconductor light-emitting diodes have problems such as poor temperature characteristics and low versatility. Furthermore, infrared light-emitting diodes made of GaAs-based compound semiconductors have problems such as fluctuations in emission wavelength between products due to subtle changes in manufacturing conditions, and in order to obtain a specified emission wavelength, the yield of infrared light-emitting diodes decreases and the price increases. Therefore, a better infrared light-emitting device that can solve these problems has been desired. Therefore, attempts have been made to manufacture an infrared light-emitting device by combining a GaN-based compound semiconductor light-emitting diode element, which is highly versatile, with an infrared light-emitting phosphor.

Patent Document 1 discloses a light emitting device comprising a GaN-based compound semiconductor blue light emitting diode element, a YAG:Ce, Er-based phosphor that absorbs blue light and emits yellow and infrared light, and a filter that blocks ultraviolet light or visible light.
Patent Document 2 discloses an infrared emitting LED using an infrared emitting phosphor material on the light source. Specifically, the document shows an example of combining an infrared emitting phosphor material using Cr as a sensitizer and Nd, Yb, and Er as luminescent ions in yttrium gallium garnet (YGG) with an LED element that emits light at 660 nm.

On the other hand, Patent Document 3 describes an infrared emitting material, YAG:Fe,Er, which has both magnetic properties and infrared emitting properties, as a luminescent compound used in a specific authentication system.

As another example of an infrared emitting phosphor, Non-Patent Document 1 discloses a phosphor having LaMgAl ₁₁ O ₁₉ as a host crystal and activated with Cr ³⁺ , which emits light at 692 nm.
Non-Patent Document 2 discloses a fluorescent material having La ₃ GaGe ₅ O ₁₆ as a host crystal and activated with Cr ³⁺ , as a material that emits light at 700 nm.
As another example of an infrared emitting phosphor, Non-Patent Document 3 discloses a phosphor having LaMgAl ₁₁ O ₁₉ as a host crystal and co-activated with Cr ³⁺ and Nd ³⁺ , which emits light at 1060 nm and 1080 nm.
On the other hand, Non-Patent Document 4 discloses a fluorescent material having LaMgAl ₁₁ O ₁₉ as a host crystal and co-activated with Tm ³⁺ and Dy ³⁺ as a material that emits visible light at 450 nm and 570 nm.
Furthermore, Non-Patent Document 5 discloses an infrared emitting material in which germanium fluoride glass is co-activated with Cr ³⁺ and Tm ³⁺ .

JP 2011-233586 A JP 2012-531043 A JP 2013-508809 A

Materials Research Bulletin, 60: 397-400 (2014) Optical Materials Express, 6: 1247-1255 (2016) Materials Research Bulletin, 74: 9-14 (2016) J. Am. Ceram. Soc., 98(3): 788-794 (2015) AIP ADVANCES 4, 107145 (2014)

The infrared-emitting phosphor YAG:Ce,Er disclosed in Patent Document 1 has an emission wavelength of around 1500 nm, which means that even if the light received is a wavelength longer than the range that the Si light-receiving element of the detector can detect, it cannot be detected by the detector. There is also the problem that this phosphor can only be excited by blue light. Furthermore, because a phosphor that strongly emits visible light is used, it is necessary to use means such as a filter to create a light-emitting device that can only obtain infrared light, which creates the problem of a complex structure for the light-emitting device.

The infrared-emitting phosphor materials used in Patent Document 2 all emit light in the wavelength region of 1000 nm or more, which poses the problem of emitting light in a wavelength region where the detection sensitivity of Si detectors is low. In addition, the technical literature related to phosphors only lists types of transition metal elements and rare earth elements that are generally known as sensitizers and luminescent ions, and it is completely unclear which sensitizers and luminescent ions should be combined to obtain a phosphor with excitation and emission characteristics suited to the purpose.

The infrared emitting material described in Patent Document 3 has an issue in that the host lattice contains a very large amount of elements such as Fe, which also has magnetic properties, resulting in a significant decrease in luminescence properties. In addition, because the emission of Er is around 1500 nm, as mentioned above, the wavelength is longer than the detection range of the detector and cannot be detected by the detector.

The infrared-emitting phosphors described in Non-Patent Documents 1 and 2 have emission wavelengths of 692 nm and 700 nm, and therefore have a problem in that they are difficult to distinguish from visible light. Conventionally known phosphors using Cr ³⁺ as an activator ion are generally not affected by visible light emission, and none of them are known to emit light in a wavelength range suitable for detection by a Si detector, and therefore they cannot be said to be suitable for infrared light-emitting devices.

The infrared-emitting phosphor described in Non-Patent Document 3 has an emission wavelength of 1000 nm or more, so there is a problem that the detector cannot detect light that is longer than the range that the Si light-receiving element of the detector can detect.

The luminescent materials described in Non-Patent Document 4 have emission wavelengths of 450 nm and 570 nm, and are luminescent materials for white light applications that emit visible light upon ultraviolet excitation. Therefore, they cannot be excited into visible light when combined with blue light-emitting diodes, and furthermore cannot be used for infrared emission applications.

The infrared emitting material described in Non-Patent Document 5 has an emission wavelength of 1500 nm or 1800 nm, so there is a problem that the detector cannot detect the received light even if the wavelength is longer than the range that the detector's light receiving element, Si, can detect. Furthermore, because glass is used as the host, the behavior of the activation ions within the crystal structure of the single crystal cannot be predicted. Therefore, when other single crystals are used as the host, the excitation characteristics and emission characteristics of the combination of these activation ions cannot be predicted.

The present invention has been made in consideration of the above problems, and has an object to provide a novel infrared-emitting phosphor that emits light in a wavelength range for which a Si detector has high sensitivity, and an infrared-emitting device that includes a semiconductor light-emitting element that emits light in the ultraviolet or visible wavelength range, and the infrared-emitting phosphor.

As a result of intensive research aimed at solving the above-mentioned problems, the inventors discovered an infrared-emitting phosphor that emits infrared light in a wavelength range for which a Si detector has high sensitivity, and that can be excited by light emitted from any of ultraviolet, blue, green and red semiconductor light-emitting elements, and found that this could solve the above-mentioned problems, thereby arriving at the present invention.
That is, the gist of the present invention lies in the following [1] to [22].
[1] A light-emitting device including a semiconductor light-emitting element that emits ultraviolet light or visible light, and a phosphor that absorbs the ultraviolet light or visible light emitted from the semiconductor light-emitting element and emits light in the infrared region, wherein the phosphor that emits light in the infrared region has an emission peak wavelength in the infrared region between 700 and 1000 nm, and the half-width of the waveform of the emission peak is less than 60 nm.
[2] The light emitting device according to [1], wherein the phosphor that emits light in the infrared region contains at least Tm or Cr as an activation element.
[3] The light-emitting device according to [1] or [2], wherein the phosphor that emits light in the infrared region contains at least Tm as an activator element, and further contains at least one element selected from the group consisting of rare earth metal elements and transition metal elements.
[4] The light emitting device according to [3], wherein the at least one element selected from the group consisting of rare earth metal elements and transition metal elements is at least one element of Cr, Mn, Sm, and Cu.
[5] The light emitting device according to [4], wherein the at least one element selected from the group consisting of rare earth metal elements and transition metal elements is Cr.
[6] The light emitting device according to any one of [1] to [5], wherein the minimum reflectance (%) of the phosphor emitting light in the infrared region in the wavelength range of 350 to 700 nm is lower than the minimum reflectance (%) in the wavelength range of 700 to 800 nm, and the difference is 20% or more.
[7] The light emitting device according to any one of [1] to [6], wherein the peak emission wavelength of ultraviolet light or visible light emitted from the semiconductor light emitting element is between 300 and 700 nm.
[8] A phosphor comprising a crystalline phase having a chemical composition represented by the following formula (1-2), absorbing ultraviolet or visible light, and having an emission peak wavelength in the range of 750 to 950 nm:
(M1 _a-b M2 _b ) ₃ (M3 _c-d M4 _d ) ₅ O ₁₂ ... (1-2)
Here, M1 represents one or more metal elements selected from the group consisting of rare earth metal elements (excluding Tm and Sc) and alkaline earth metal elements, M2 represents one or more rare earth metal elements (excluding Sc) different from M1 as the rare earth metal element, which essentially requires Tm, M3 represents one or more metal elements selected from B, Al, Ga, In, Sc, Si, Ge, Ti, Sn, Zr, and Hf, M4 represents one or more metal elements selected from Cr and Mn, and O represents oxygen, and 0<a<1, 0<b≦0.5, 0<c<1, 0<d≦0.5.
[9] The phosphor according to [8], wherein the crystal phase has a garnet structure.
[10] A phosphor comprising a crystalline phase having a chemical composition represented by the following formula (2-1), absorbing ultraviolet or visible light, and having an emission peak wavelength in the range of 750 to 950 nm:
(A1 _1-a A2 _a ) ₂ (A3 _1-b A4 _b ) ₂ O ₆ ... (2-1)
wherein A1 represents one or more metal elements selected from the group consisting of rare earth metal elements other than Tm and alkaline earth metal elements other than Mg, A2 represents one or more metal elements different from A1 as the rare earth metal element, essentially consisting of Tm or Nd, A3 represents one or more metal elements selected from Mg, Co, and Zn, A4 represents two or more metal elements including one or more metal elements selected from Cr, Mn, Ni, Fe, and Cu, essentially consisting of Cr or Mn, and one or more metal elements selected from B, Al, Ga, In, Si, Ge, Ti, Sn, Zr, and Hf, and O represents oxygen, 0<a≦0.5, 0<b≦0.75.
[11] The phosphor according to [10], wherein the crystal phase has a double perovskite structure.
[12] The phosphor according to [10] or [11], wherein in the formula (2-1), A4 is two or more metal elements including Mn and Ge.
[13] A phosphor comprising a crystalline phase having a chemical composition represented by the following formula (3-1), absorbing ultraviolet or visible light, and having an emission peak wavelength in the range of 750 to 1000 nm:
(D1 _1-a-b D2 _a D3 _b ) (D4 _1-a D5 _11+a-c D6 _c ) O ₁₉ ... (3-1)
wherein D1 represents one or more rare earth metal elements selected from rare earth metal elements (excluding Tm and Sc), D2 represents one or more metal elements selected from Ca, Sr, and Ba, D3 represents one or more rare earth metal elements (excluding Sc) different from D1 as a rare earth metal element, which essentially requires Tm, D4 includes one or more metal elements selected from Mg and Zn, D5 represents one or more metal elements selected from Al, Ga, In, and Sc, D6 represents one or more metal elements selected from Cr, Mn, Ni, Fe, and Cu, and O represents oxygen, with 0≦a≦0.99, 0<b≦0.2, and 0<c≦2.2.
[14] The phosphor according to [13], wherein the crystal phase is a crystal phase having a magnetoplumbite structure.
[15] The phosphor according to [13] or [14], wherein in the formula (3-1), D6 contains at least Cr.
[16] A phosphor comprising a crystalline phase having a chemical composition represented by the following formula (4-1), absorbing ultraviolet or visible light, and having an emission peak wavelength in the range of 700 to 1000 nm:
E1 ₅ (E2 _1-a E3 _a ) ₄ O ₁₅ ... (4-1)
Here, E1 represents one or more metal elements selected from the group consisting of rare earth metal elements, Ca, Sr, and Ba; E2 represents one or more metal elements selected from Al, Ga, In, Sc, Y, Ti, Zr, Si, Ge, Sn, Mg, Zn, V, Nb, Ta, Mo, and W; E3 represents one or more metal elements different from E2 selected from transition metal elements; O represents oxygen, and 0<a<0.2.
[17] The phosphor according to [16], wherein the crystal phase has a hexagonal perovskite structure.
[18] The phosphor according to [16] or [17], wherein, in the formula (4-1), E2 contains at least Al.
[19] The phosphor according to any one of [16] to [18], wherein, in the formula (4-1), E3 contains at least Cr.
[20] A phosphor comprising a crystalline phase having divalent samarium (Sm) and trivalent thulium (Tm) as activation elements in a host crystal, absorbing ultraviolet or visible light, and having an emission peak wavelength in the range of 800 to 1000 nm.
[21] The phosphor according to [20], wherein the host crystal further contains one or more metal elements selected from the group consisting of alkali metal elements and alkaline earth metal elements, one or more metal elements selected from B, Al, Ga, Si, Ge, and P, and one or more elements selected from O, F, Cl, and Br.
[22] The phosphor according to [20] or [21], wherein the host crystal contains a crystal phase having a chemical composition represented by the following formula (5-1):
G1 _1-a G2 _a G3 _b O ₅ ... (5-1)
Here, G1 represents one or more metal elements selected from alkaline earth metal elements, G2 represents two or more metal elements selected from rare earth metal elements, essentially including Sm and Tm, G3 represents two or more metal elements selected from B, Al, Ga, Si, Ge, and P, O represents oxygen, and 0<a<0.2 and 1.5<b<2.5.

According to the present invention, it is possible to provide a novel infrared-emitting phosphor that emits light in a wavelength range where the detection sensitivity of a Si detector is high, specifically, a novel infrared-emitting phosphor whose emission peak wavelength in the infrared range is between 700 and 1000 nm and whose waveform half-width of the emission peak is less than 60 nm, and an infrared light-emitting device including a semiconductor light-emitting element that emits light in the ultraviolet or visible wavelength range and the infrared-emitting phosphor.It is also possible to provide a light-emitting device that can obtain only the desired infrared emission without using a complicated configuration such as a filter.
The infrared light-emitting phosphor emits infrared light at a desired wavelength and emits very little light at other wavelengths, and therefore has high luminous efficiency. In addition, the emission wavelength of the infrared light-emitting phosphor is determined by the type of activation element and does not change, so that when the infrared light-emitting phosphor is used in a light-emitting device, it is possible to provide an infrared light-emitting device that emits light at a predetermined emission wavelength at low cost without causing wavelength fluctuation between light-emitting devices.

1 shows the emission spectra of the phosphors of Example 1-1 and Comparative Example 1-1. 1 shows the excitation spectra of the phosphors of Example 1-1 and Comparative Example 1-1. 1 shows an XRD pattern of the phosphor of Example 1-1. 1 shows the emission spectrum of Example 1-2. 1 shows the emission spectra of the phosphors of Example 2-1 and Comparative Example 2-1. 2 shows the excitation spectra of the phosphors of Example 2-1 and Comparative Example 2-1. 1 shows an XRD pattern of the phosphor of Example 2-1. 1 shows the emission spectrum of the phosphor of Example 2-2. 1 shows the excitation spectrum of the phosphor of Example 2-2. 1 shows an XRD pattern of the phosphor of Example 2-2. 1 shows the emission spectrum of the light emitting device of Example 2-3. 1 shows the emission spectrum of the light emitting device of Example 2-4. 1 shows the emission spectrum of the phosphor of Example 3-1. 1 shows the excitation spectrum of the phosphor of Example 3-1. 1 shows an XRD pattern of the phosphor of Example 3-1. 1 shows the emission spectrum of the phosphor of Example 4-1. 1 shows the excitation spectrum of the phosphor of Example 4-1. 1 shows an XRD pattern of the phosphor of Example 4-1. 1 shows the excitation spectrum (dotted line) and emission spectrum (solid line) of the phosphor of Example 5-1. 1 shows an XRD pattern of the phosphor of Example 5-1.

Hereinafter, the embodiments of the present invention will be described in detail. Note that the present invention is not limited to the contents described below, and can be implemented with any modifications within the scope of the present invention.
In this specification, a numerical range expressed using "~" means a range including the numerical values written before and after "~" as the lower and upper limits. In addition, in the composition formula of the phosphor in this specification, each composition formula is separated by a comma (,). In addition, when multiple elements are listed separated by a comma (,), it indicates that one or more of the listed elements may be contained in any combination and composition.

{Phosphor}
The phosphor according to the first embodiment of the present invention is an infrared phosphor that absorbs ultraviolet light or visible light emitted from a semiconductor light emitting element and emits light in the infrared region, and is characterized in that the emission peak wavelength in the infrared region is between 700 and 1000 nm. In this specification, the phosphor according to the first embodiment of the present invention may be referred to as an "infrared phosphor" or an "infrared emitting phosphor".
Here, the emission peak in the infrared region means the largest emission peak among the emission peaks in the wavelength range from 730 nm to 1000 nm. Therefore, the emission peak wavelength in the infrared region means the wavelength at which the largest emission peak occurs among the emission peaks in the wavelength range from 730 nm to 1000 nm.
In this specification, ultraviolet light means light with a wavelength of less than 400 nm, and visible light means light with a wavelength of 400 nm to 700 nm.

[Emission spectrum]
The infrared phosphor according to the first embodiment preferably has the following characteristics when the emission spectrum is measured by exciting the phosphor with light having a peak wavelength of 300 nm or more, 700 nm or less, or 650 nm or less. The peak wavelength refers to the wavelength at which the largest emission peak occurs among emission peaks having wavelengths of 300 nm or more, 700 nm or less, or 650 nm or less.

The emission peak wavelength λp (nm) in the above-mentioned emission spectrum is usually 700 nm or more, preferably 730 nm or more, more preferably 750 nm or more, even more preferably 770 nm or more, even more preferably 780 nm or more, still more preferably 800 nm or more, and usually 1000 nm or less, preferably 950 nm or less, more preferably 940 nm or less, even more preferably 930 nm or less, still more preferably 900 nm or less, still more preferably 880 nm or less, still more preferably 870 nm or less, and still more preferably 850 nm or less.
A value within the above range is preferred in terms of providing suitable infrared emission.

Furthermore, the infrared phosphor according to the first embodiment has a half-width of the waveform of an emission peak in the infrared region that is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 60 nm or less, still more preferably less than 60 nm, even more preferably 50 nm or less, and preferably 1 nm or more.
When the half-width of the waveform of the emission peak in the infrared region is within the above range, it is preferable because it tends to be highly compatible with a light receiving element that detects infrared emission emitted from the infrared phosphor, and it is also preferable because it tends to have a particularly high emission intensity at a desired emission wavelength.

In addition, in order to excite the above infrared phosphor with light having a peak wavelength of 300 nm or more, 700 nm or less, or 650 nm or less, for example, a xenon light source can be used. Furthermore, the emission spectrum of the phosphor obtained in the first embodiment can be measured using, for example, a fluorescence spectrophotometer F-4500 or F-7000 (manufactured by Hitachi, Ltd.). The emission peak wavelength and the half-width of the emission peak waveform in the infrared region can be calculated from the obtained emission spectrum.
The half-width of the waveform of the emission peak in the infrared region may be measured by measuring the half-width of the waveform of the largest emission peak among the emission peaks between wavelengths 700 and 1000 nm, but when the largest emission peak is observed overlapping with multiple peaks, the half-width is the interval between two wavelengths at half the value of the largest emission peak. For example, in the emission spectrum of the phosphor of Example 1-1 in FIG. 1-1, the peak having a peak top at 794 nm (peak indicated by a black triangle) is the largest emission peak, and the half-width was calculated by measuring the interval between two wavelengths at 782.8 nm and 832.4 nm at half the value of the emission peak (point indicated by a black circle).

[Excitation spectrum]
The infrared phosphor according to the first embodiment has an excitation peak in a wavelength range of usually 300 nm or more, preferably 350 nm or more, more preferably 400 nm or more, and usually 700 nm or less, preferably 650 nm or less, more preferably 600 nm or less, and even more preferably 550 nm or less. That is, it is excited by light in the near ultraviolet to red to deep red region.

[Quantum efficiency/absorption efficiency]
The external quantum efficiency (η _o ) of the infrared phosphor according to the first embodiment is usually 3% or more, preferably 4% or more, more preferably 6% or more, even more preferably 25% or more, still more preferably 40% or more, and even more preferably 50% or more. The higher the external quantum efficiency, the higher the luminous efficiency of the phosphor, which is therefore preferable.
The internal quantum efficiency (η _i ) in the infrared phosphor according to the first embodiment is usually 5% or more, preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, even more preferably 30% or more, even more preferably 50% or more, much more preferably 70% or more, and even more preferably 90% or more. The internal quantum efficiency means the ratio of the number of emitted photons to the number of photons of excitation light absorbed by the infrared phosphor. Therefore, the higher the internal quantum efficiency, the higher the luminous efficiency and luminous intensity of the infrared phosphor, which is preferable.

The absorption efficiency of the infrared phosphor according to the first embodiment is usually 20% or more, preferably 25% or more, more preferably 30% or more, even more preferably 35% or more, even more preferably 40% or more, even more preferably 50% or more, and most preferably 60% or more. The higher the absorption efficiency, the higher the luminous efficiency of the phosphor and the less the amount of infrared phosphor required, which is preferable.

[composition]
The composition of the infrared phosphor according to the first embodiment is not particularly limited as long as it has a desired emission peak wavelength. The composition of the infrared phosphor can be confirmed by a commonly known method. For example, X-ray fluorescence analysis, high-frequency inductively coupled plasma (ICP) emission analysis, X-ray photoelectron spectroscopy, etc. can be mentioned.
In order to make the infrared phosphor according to the first embodiment have an emission peak wavelength in the infrared region of 700 to 1000 nm, it is preferable to include an element selected from rare earth metal elements and transition metal elements as an activator element, and more preferably to include at least two elements selected from rare earth metal elements and transition metal elements. This is because, when the infrared phosphor emits light using ultraviolet light or visible light emitted from a semiconductor light-emitting element as excitation light, it is difficult to lengthen the emission wavelength to a desired wavelength with only one activator element. Therefore, it is preferable to use, as an activator element, a combination of an element that acts as a sensitizer and an element that acts as a light-emitting ion that is excited by the energy supplied from the sensitizer and emits light. It is also preferable to include at least one element of Tm, Cr, and Sm as an activator element.
In addition, since it is easy to obtain a phosphor with a particularly high emission intensity at a desired emission wavelength by narrowing the half-width of the waveform of the emission peak in the infrared region, it is preferable to appropriately combine the following sensitizers and activating elements that act as luminescent ions. This makes it possible to obtain an infrared phosphor with high luminous efficiency without losing excitation energy from the semiconductor light-emitting element. Examples of elements that act as sensitizers include Ce, Eu, Cr, Mn, Cu, and Sm. Examples of elements that act as luminescent ions include Tm, Nd, Cr, and Sm. From the viewpoint of the wavelength of the emission peak of the infrared phosphor, it is more preferable to include at least thulium (Tm) as an activating element, and further include at least one element selected from rare earth metal elements and transition metal elements. This is because Tm is preferable as an element that acts as a luminescent ion.

The activating element other than Tm is preferably at least one of Cr, Mn, Sm, and Cu. These elements are particularly preferable as sensitizers that absorb light ranging from ultraviolet to visible light and allow Tm to function as a luminescent ion, and in combination with Tm, energy transition can be performed with high efficiency. Of these, the most preferable combination of activating elements is Tm and Cr.

[Crystal structure]
By selecting appropriate elements based on the above description, the infrared phosphor according to the first embodiment can be adjusted to have a desired emission peak wavelength, regardless of the type and composition of elements of the lattice crystals constituting the crystalline phase of the infrared phosphor, or the crystal structure.
The infrared phosphor according to the first embodiment can have various crystal structures as a crystal phase, for example, a perovskite structure, a double perovskite structure, a hexagonal perovskite structure, a garnet structure, a magnetoplumbite structure, and the like.

[Reflectance]
From the viewpoint of wavelength conversion efficiency, the minimum reflectance (%) of the phosphor emitting in the infrared region according to the first embodiment in the wavelength range of 350 to 700 nm is lower than the minimum reflectance (%) in the wavelength range of 700 to 800 nm, and the difference between the two minimum reflectances is usually 20% or more, preferably 30% or more, more preferably 50% or more, and is usually less than 90%.

[Preferred embodiment 1-1]
The infrared phosphor according to the first embodiment includes a phosphor that contains a crystalline phase having a chemical composition represented by the following formula (1-1), absorbs ultraviolet light or visible light, and has an emission peak wavelength between 750 and 950 nm. The crystalline phase is preferably a crystalline phase having a garnet structure.
(M1 _a-b M2 _b ) ₃ (M3 _c-d M4 _d ) ₅ O ₁₂ ... (1-1)
however,
M1 represents one or more metal elements selected from the group consisting of rare earth metal elements (excluding Tm and Sc) and alkaline earth metal elements;
M2 represents one or more rare earth metal elements (excluding Sc) different from M1 as the rare earth metal element;
M3 represents one or more metal elements selected from B, Al, Ga, In, Sc, Si, Ge, Ti, Sn, Zr, and Hf;
M4 represents one or more metal elements selected from Cr, Mn, Fe, Ni, and Cu;
O represents oxygen;
0<a<1, 0<b≦0.5, 0<c<1, and 0<d≦0.5.

M1 represents one or more metal elements selected from the group consisting of rare earth metal elements (excluding thulium (Tm) and scandium (Sc)) and alkaline earth metal elements.
Examples of rare earth metal elements include yttrium (Y) and lanthanum (La). In view of the low cost of the raw material, it is preferable to contain at least Y, more preferably 50 mol % or more of M1 is Y, and further preferably 80 mol % or more of M1 is Y.
Examples of alkaline earth metal elements include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).
In addition, M1 may be partially substituted with other elements, such as sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), within the scope that does not impair the effect of the infrared phosphor according to this embodiment.

M2 represents one or more rare earth metal elements (excluding scandium (Sc)) different from M1 as the rare earth metal element. Such rare earth metal elements include cerium (Ce), europium (Eu), and thulium (Tm), and are not particularly limited as long as they are elements different from M1. However, it is preferable that at least Tm is included because of infrared emission, and it is more preferable that 10 mol % or more of M2 is Tm, and even more preferable that 50 mol % or more of M2 is Tm.

M3 represents one or more metal elements selected from boron (B), aluminum (Al), gallium (Ga), indium (In), scandium (Sc), silicon (Si), germanium (Ge), titanium (Ti), tin (Sn), zirconium (Zr), and hafnium (Hf). Because it is easy to activate the sensitizer, it preferably contains at least Al or Ga, and more preferably 10 mol % or more of M3 is Al and/or Ga, and even more preferably Al or Ga.

M4 represents one or more metal elements selected from chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), and copper (Cu). Because of their tendency to absorb ultraviolet and visible light, it is preferable that at least Cr or Mn is included, and it is preferable that 10 mol% or more of M4 is Cr and/or Mn, and it is even more preferable that it is Cr or Mn. In addition, it is preferable that the metal element having magnetic properties, such as Fe, is 50 mol% or less.

O represents oxygen, which may be partially substituted with other elements as long as the effect of the infrared phosphor according to this embodiment is not impaired. Examples of other elements include chlorine (Cl), fluorine (F), bromine (Br), iodine (I), sulfur (S), and nitrogen (N).

a represents the content of M1, and the range is usually 0<a<1, with the lower limit being preferably 0.7 or more, more preferably 0.8 or more, and the upper limit being preferably 0.999 or less, more preferably 0.990 or less.
b represents the content of M2, and the range is usually 0<b≦0.5, with the lower limit being preferably 0.001 or more, more preferably 0.005 or more, and the upper limit being preferably 0.3 or less, more preferably 0.2 or less.
c indicates the content of M3, and the range is usually 0<c<1. The lower limit is preferably 0.7 or more, more preferably 0.8 or more, and the upper limit is preferably 0.999 or less, more preferably 0.990 or less.
d indicates the content of M4, and the range is usually 0<d≦0.5. The lower limit is preferably 0.001 or more, more preferably 0.005 or more, and the upper limit is preferably 0.3 or less, more preferably 0.2 or less.

[Preferred embodiment 1-2]
Another preferred embodiment of the infrared phosphor according to the first embodiment is a phosphor that contains a crystalline phase having a chemical composition represented by the following formula (1-2), absorbs ultraviolet or visible light, and has an emission peak wavelength between 750 and 950 nm. The crystalline phase is preferably a crystalline phase having a garnet structure.
(M1 _a-b M2 _b ) ₃ (M3 _c-d M4 _d ) ₅ O ₁₂ ... (1-2)
however,
M1 represents one or more metal elements selected from the group consisting of rare earth metal elements (excluding Tm and Sc) and alkaline earth metal elements;
M2 represents one or more rare earth metal elements (excluding Sc) different from M1 as the rare earth metal element, which essentially contains Tm;
M3 represents one or more metal elements selected from B, Al, Ga, In, Sc, Si, Ge, Ti, Sn, Zr, and Hf;
M4 represents one or more metal elements selected from Cr and Mn;
O represents oxygen;
0<a<1, 0<b≦0.5, 0<c<1, and 0<d≦0.5.

In this embodiment, the explanation of the above "Preferred embodiment 1-1" is incorporated herein by reference, except for the explanation of M2 and M4 below.
M2 represents one or more rare earth metal elements (excluding scandium (Sc)) different from M1 as the rare earth metal element, essential for which is thulium (Tm).
Such rare earth metal elements include cerium (Ce) and europium (Eu), and are not particularly limited as long as they are an element different from M1. However, Tm is essential for the purpose of emitting infrared light, and it is more preferable that 10 mol % or more of M2 is Tm, and even more preferable that 50 mol % or more of M2 is Tm.
M4 represents one or more metal elements selected from chromium (Cr) and manganese (Mn). Because of the tendency to absorb ultraviolet light and visible light, it is preferable that at least Cr or Mn is included, and it is preferable that 10 mol % or more of M4 is Cr and/or Mn, and more preferably Cr or Mn. In addition, it is preferable that the metal element having magnetic properties, such as iron (Fe), is 50 mol % or less.

[Preferred embodiment 1-3]
The phosphor according to the preferred aspect 1-2 is more preferably such that M2 in the formula (1-2) is Tm. That is, it is a Tm3+-activated infrared phosphor having a chemical composition represented by the following formula ( ^1-3 ), containing a crystal phase having a garnet structure, absorbing ultraviolet light or visible light, and having an emission peak wavelength within the wavelength range of 750 to 950 nm.
(M1 _a-b M2 _b ) ₃ (M3 _c-d M4 _d ) ₅ O ₁₂ ... (1-3)
however,
M1 represents one or more metal elements selected from rare earth metal elements (excluding Tm and Sc) and alkaline earth metal elements;
M2 indicates Tm,
M3 represents one or more metal elements selected from B, Al, Ga, In, Sc, Si, Ge, Ti, Sn, Zr, and Hf;
M4 represents one or more metal elements selected from Cr and Mn;
O represents oxygen;
0<a<1, 0<b≦0.5, 0<c<1, and 0<d≦0.5.

In this embodiment, the explanation of the above "Preferred embodiment 1-1" is incorporated herein by reference, except for the explanation of M2 and M4 below.
M2 represents Tm. By including Tm as an activator element, it is possible to obtain a high-quality infrared phosphor having an emission peak in the wavelength range of 750 to 950 nm.
M4 represents one or more metal elements selected from chromium (Cr) and manganese (Mn). It is more preferable that 10 mol% or more of M4 is Cr, and it is even more preferable that M4 is Cr. Cr and Mn have strong absorption in ultraviolet or visible light, and are particularly preferable as sensitizers for Tm to function as a luminescent ion, and energy transfer can be performed with high efficiency in combination with Tm.

[Preferred embodiment 2-1]
Another preferred embodiment of the infrared phosphor according to the first embodiment is a phosphor that contains a crystalline phase having a chemical composition represented by the following formula (2-1), absorbs ultraviolet or visible light, and has an emission peak wavelength between 750 and 950 nm. The crystalline phase is preferably a crystalline phase having a double perovskite structure.
(A1 _1-a A2 _a ) ₂ (A3 _1-b A4 _b ) ₂ O ₆ ... (2-1)
however,
A1 represents one or more metal elements selected from the group consisting of rare earth metal elements other than Tm and alkaline earth metal elements other than Mg;
A2 represents one or more metal elements different from A1 as the rare earth metal element, essentially including Tm or Nd;
A3 represents one or more metal elements selected from Mg, Co, and Zn;
A4 represents two or more metal elements including one or more metal elements selected from Cr, Mn, Ni, Fe, and Cu, with Cr or Mn being essential, and one or more metal elements selected from B, Al, Ga, In, Si, Ge, Ti, Sn, Zr, and Hf;
O represents oxygen;
0<a≦0.5 and 0<b≦0.75.

A1 represents one or more metal elements selected from the group consisting of rare earth metal elements other than thulium (Tm) and alkaline earth metal elements other than magnesium (Mg).
Examples of rare earth metal elements other than thulium (Tm) include scandium (Sc), yttrium (Y), and lanthanum (La). In view of the low cost of the raw material, it is preferable that at least La is contained, and it is more preferable that 50 mol % or more of A1 is La, furthermore preferably that 80 mol % or more of A1 is La, and it is particularly preferable that A1 is La.
Examples of alkaline earth metal elements other than Mg include calcium (Ca), strontium (Sr), and barium (Ba).
In addition, A1 may be partially substituted with other elements within a range that does not impair the effect of the infrared phosphor according to this embodiment, such as sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

A2 represents one or more metal elements different from A1 as the rare earth metal element, with at least thulium (Tm) or neodymium (Nd) being essential. By having Tm or Nd as an activating element, it is possible to obtain a high-quality infrared phosphor with an emission peak in the wavelength range of 750 to 950 nm. Furthermore, when the activating element contains one or more metal elements different from A1 as the rare earth metal element, such as cerium (Ce) or europium (Eu), these act as sensitizers and can enhance the emission at the desired wavelength.

A3 represents one or more metal elements selected from magnesium (Mg), cobalt (Co), and zinc (Zn). Because they are not heavy metals and have low toxicity, it is preferable that A3 contains at least Mg or Zn, and it is more preferable that A3 contains 10 mol % or more of Mg and/or Zn, and even more preferable that A3 contains Mg or Zn, and it is particularly preferable that A3 contains Mg.

A4 represents two or more metal elements, including one or more metal elements selected from chromium (Cr), manganese (Mn), nickel (Ni), iron (Fe) and copper (Cu), with chromium (Cr) or manganese (Mn) being essential, and one or more metal elements selected from boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), titanium (Ti), tin (Sn), zirconium (Zr) and hafnium (Hf).

By containing at least Cr or Mn as an activating element, A4 acts as a sensitizer and can increase the emission peak intensity between wavelengths of 750 and 950 nm. Cr and Mn have strong absorption in ultraviolet or visible light, and are particularly preferable as sensitizers for Tm to act as a luminescent ion, and in combination with Tm, energy transition can be performed with high efficiency. A4 preferably contains Cr or Mn, and more preferably contains Mn. In addition, the content of Cr and Mn in A4 is preferably 0.1 mol % or more, more preferably 0.2 mol % or more, and even more preferably 0.5 mol % or more, based on the total amount of Cr and Mn.

Furthermore, A4 can constitute a host crystal that is easy to activate the sensitizer by containing one or more metal elements selected from B, Al, Ga, In, Si, Ge, Ti, Sn, Zr, and Hf. Because it is easier to activate the sensitizer, A4 preferably contains Ge or Ti, and more preferably contains Ge. Furthermore, the content of Ge and Ti in A4 is preferably 10 mol% or more, more preferably 50 mol% or more, and even more preferably 90 mol% or more, based on the total amount of Ge and Ti.
Therefore, A4 is preferably two or more metal elements including Mn and Ge.

Ni, Fe, and Cu are also activating elements that act as sensitizers.
The molar ratio of the activation elements (Cr, Mn, Ni, Fe, Cu) in A4 to the metal elements (B, Al, Ga, In, Si, Ge, Ti, Sn, Zr, Hf) constituting the host crystal is preferably 0.1:99.9 to 50:50, more preferably 0.2:99.8 to 20:80, and particularly preferably 0.5:99.5 to 10:90.

O represents oxygen, which may be partially substituted with other elements as long as the effect of the infrared phosphor according to this embodiment is not impaired. Examples of other elements include chlorine (Cl), fluorine (F), bromine (Br), iodine (I), sulfur (S), and nitrogen (N).

a represents the content of A2, and the range is usually 0<a≦0.5, with the lower limit being preferably 0.001 or more, more preferably 0.005 or more, and the upper limit being preferably 0.3 or less, more preferably 0.2 or less.
b represents the content of A4 and is usually in the range of 0<b≦0.75, with the lower limit being preferably 0.1 or more, more preferably 0.4 or more, and the upper limit being preferably 0.7 or less, more preferably 0.6 or less.

[Preferred embodiment 3-1]
Another preferred embodiment of the infrared phosphor according to the first embodiment is a phosphor that contains a crystalline phase having a chemical composition represented by the following formula (3-1), absorbs ultraviolet light or visible light, and has an emission peak wavelength between 750 and 1000 nm. The crystalline phase is preferably a crystalline phase having a magnetoplumbite structure.
(D1 _1-a-b D2 _a D3 _b ) (D4 _1-a D5 _11+a-c D6 _c ) O ₁₉ ... (3-1)
however,
D1 represents one or more rare earth metal elements selected from rare earth metal elements (excluding Tm and Sc);
D2 represents one or more metal elements selected from Ca, Sr, and Ba;
D3 represents one or more rare earth metal elements (excluding Sc) different from D1 as a rare earth metal element, which is essential for Tm;
D4 contains one or more metal elements selected from Mg and Zn;
D5 represents one or more metal elements selected from Al, Ga, In, and Sc;
D6 represents one or more metal elements selected from Cr, Mn, Ni, Fe, and Cu;
O represents oxygen;
0≦a≦0.99, 0<b≦0.2, and 0<c≦2.2.

D1 represents one or more metal elements selected from rare earth metal elements (excluding Tm and Sc). Examples of rare earth metal elements other than thulium (Tm) and scandium (Sc) include yttrium (Y), gadolinium (Gd), lutetium (Lu), lanthanum (La), etc., but due to the low cost of raw materials, it is preferable to contain at least La, more preferably 50 mol % or more of D1 is La, even more preferably 80 mol % or more of D1 is La, and particularly preferably D1 is La.
D1 may be partially substituted with other elements, such as sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), within the scope of not impairing the effect of the infrared phosphor according to the present embodiment.

D2 represents one or more metal elements selected from calcium (Ca), strontium (Sr), and barium (Ba). Because it is easy to form a single crystalline phase, it preferably contains at least Ca or Sr, more preferably 10 mol % or more of D2 is Ca and/or Sr, and even more preferably 50 mol % or more of D2 is Ca or Sr.

D3 indicates one or more rare earth metal elements (excluding scandium (Sc)) different from D1 as a rare earth metal element, with thulium (Tm) as an essential element. By having Tm as an activating element, a high-quality infrared phosphor having an emission peak between wavelengths of 750 and 1000 nm can be obtained. Examples of one or more rare earth metal elements (excluding Sc) different from D1 as a rare earth metal element include cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb), etc. When such elements other than Tm are included as activating elements, they act as sensitizers and can enhance the emission at the desired wavelength.

D4 represents one or more metal elements selected from magnesium (Mg) and zinc (Zn), and it is more preferable that 10 mol% or more of D4 is Mg, even more preferable that 50 mol% or more of D4 is Mg, and it is particularly preferable that D4 is Mg.

D5 represents one or more metal elements selected from aluminum (Al), gallium (Ga), indium (In), and scandium (Sc), and it is more preferable that D5 is 10 mol% or more Al, even more preferable that D5 is 50 mol% or more Al, and it is particularly preferable that D5 is Al.

D6 represents one or more metal elements selected from chromium (Cr), manganese (Mn), nickel (Ni), iron (Fe) and copper (Cu), and it is more preferable that D6 is 10 mol% or more of Cr or Mn, more preferably 20 mol% or more of Cr or Mn, and particularly preferably 50 mol% or more of Cr or Mn.

O represents oxygen, which may be partially substituted with other elements as long as the effect of the infrared phosphor according to this embodiment is not impaired. Examples of other elements include chlorine (Cl), fluorine (F), bromine (Br), iodine (I), sulfur (S), and nitrogen (N).

a represents the content of D2, and the range is usually 0≦a≦0.99. The lower limit is preferably 0.01 or more, more preferably 0.1 or more, and the upper limit is preferably 0.98.
It is preferably 0.9 or less, and more preferably 0.9 or less.
b represents the content of D3, and is usually in the range of 0<b≦0.2. The lower limit is preferably 0.001 or more, more preferably 0.005 or more, and the upper limit is preferably 0.15 or less, more preferably 0.10 or less.
c indicates the content of D6, and its range is usually 0<c≦2.2, with the lower limit being preferably 0.01 or more, more preferably 0.1 or more, and the upper limit being preferably 2.0 or less, more preferably 1.5 or less.

[Preferred embodiment 4-1]
Another preferred embodiment of the infrared phosphor according to the first embodiment is a phosphor that contains a crystalline phase having a chemical composition represented by the following formula (4-1), absorbs ultraviolet light or visible light, and has an emission peak wavelength between 700 and 1000 nm. The crystalline phase is preferably a crystalline phase having a hexagonal perovskite structure.
E1 ₅ (E2 _1-a E3 _a ) ₄ O ₁₅ ... (4-1)
however,
E1 represents a rare earth metal element and one or more metal elements selected from the group consisting of Ca, Sr, and Ba;
E2 represents one or more metal elements selected from Al, Ga, In, Sc, Y, Ti, Zr, Si, Ge, Sn, Mg, Zn, V, Nb, Ta, Mo, and W;
E3 represents one or more metal elements different from E2 selected from transition metal elements;
O represents oxygen;
0<a<0.2.

E1 represents one or more metal elements selected from the group consisting of rare earth metal elements, calcium (Ca), strontium (Sr), and barium (Ba). Examples of rare earth metal elements include lanthanum (La), gadolinium (Gd), and lutetium (Lu). In view of the low cost of raw materials, it is preferable to contain at least La, more preferably 40 mol % or more of E1 is La, even more preferably 60 mol % or more of E1 is La, and particularly preferably E1 is La.
In addition, E1 may be partially substituted with other elements, such as sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), within the scope that does not impair the effect of the infrared phosphor according to this embodiment.

E2 represents one or more metal elements selected from aluminum (Al), gallium (Ga), indium (In), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), silicon (Si), germanium (Ge), tin (Sn), magnesium (Mg), zinc (Zn), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
More preferably, 10 mol % or more of E2 is Al, even more preferably, 20 mol % or more of E2 is Al, and particularly preferably, 25 mol % or more of E2 is Al.
More preferably, E2 comprises 10 mol % or more of Ti, further preferably, E2 comprises 30 mol % or more of Ti, and particularly preferably, E2 comprises 50 mol % or more of Ti.
Also, it is preferable that 50 mol % or more of E2 is Al and Ti, it is more preferable that 70 mol % or more of E2 is Al and Ti, and it is even more preferable that 90 mol % or more of E2 is Al and Ti.
When the element acting as the activator is trivalent, such as Cr3 ⁺ , the activator is introduced by replacing a portion of Al, and therefore it is preferable that the proportion of Al in E2 is greater than that of Ti. However, for reasons such as the ease of formation of a crystal phase, the proportion of Ti may be greater than that of Al.
From the viewpoint of charge compensation, in the above-mentioned preferable ratio, a part of Al may be replaced with Ga, In, Sc, or Y, and a part of Ti may be replaced with Zr, Si, Ge, or Sn.

E3 represents one or more metal elements different from E2, selected from transition metal elements. E3 acts as an activating element. Examples of E3 include chromium (Cr), manganese (Mn), vanadium (V), etc. It is more preferable that 10 mol% or more of E3 is Cr, it is more preferable that 20 mol% or more of E3 is Cr, and it is particularly preferable that 50 mol% or more of E3 is Cr.

O represents oxygen, which may be partially substituted with other elements as long as the effect of the infrared phosphor according to this embodiment is not impaired. Examples of other elements include chlorine (Cl), fluorine (F), bromine (Br), iodine (I), sulfur (S), and nitrogen (N).

a represents the content of E3, and its range is usually 0<a<0.2, with the lower limit being preferably 0.001 or more, more preferably 0.005 or more, and the upper limit being preferably 0.15 or less, more preferably 0.10 or less.

The phosphor according to the present embodiment is excellent in that it has a suitable infrared emission in the above range, even when Cr3 ⁺ , which did not show infrared emission at a suitable wavelength in conventional phosphors, is used as an activator ion. In the phosphor having the chemical composition represented by the above formula (4-1), it is not clear how the emission wavelength of the activator ion is adjusted, but it is thought that this is related to the fact that the E2 site activated by Cr3 ⁺ is shared by multiple metal cations with different valences, and the volume and symmetry of the polyhedron formed by the anion coordinated to Cr3 ⁺ .

[Preferred embodiment 5-1]
Another preferred embodiment of the infrared phosphor according to the first embodiment is a phosphor that contains a crystalline phase having divalent samarium (Sm) and trivalent thulium (Tm) as activation elements in a host crystal, absorbs ultraviolet light or visible light, and has an emission peak wavelength within the wavelength range of 750 to 1000 nm.

[Preferred embodiment 5-2]
In the phosphor according to the above-mentioned preferred aspect 5-1, it is more preferable that the host crystal further contains one or more elements selected from the group consisting of alkali metal elements and alkaline earth metal elements, one or more metal elements selected from boron (B), aluminum (Al), gallium (Ga), silicon (Si), germanium (Ge), and phosphorus (P), and one or more elements selected from oxygen (O), fluorine (F), chlorine (Cl), and bromine (Br).

[Preferred embodiment 5-3]
In addition, the phosphor according to the above-mentioned preferred aspect 5-1 or the phosphor according to the above-mentioned preferred aspect 5-2 is more preferably a phosphor in which the host crystal contains a crystalline phase having a chemical composition represented by the following formula (5-1):
G1 _1-a G2 _a G3 _b O ₅ ... (5-1)
however,
G1 represents one or more metal elements selected from alkaline earth metal elements;
G2 represents two or more metal elements selected from rare earth metal elements, essentially including Sm and Tm;
G3 represents two or more metal elements selected from B, Al, Ga, Si, Ge, and P;
O represents oxygen;
0<a<0.2 and 1.5<b<2.5.

G1 represents one or more alkaline earth metal elements selected from Mg, Ca, Sr, and Ba, and preferably 50 mol% or more of G1 is Sr and/or Ba, more preferably 70 mol% or more of Sr and/or Ba, and particularly preferably 90 mol% or more of Sr and/or Ba. G1 may be partially substituted with other elements within a range that does not impair the effect of the infrared phosphor according to this embodiment. Examples of other elements include sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).
G2 represents two or more rare earth metal elements, essentially including Sm and Tm, and preferably 50 mol % or more of G2 is Sm and Tm, more preferably 70 mol % or more of G2 is Sm and Tm, and particularly preferably 90 mol % or more of G2 is Sm and Tm.
G3 represents two or more metal elements selected from B, Al, Ga, Si, Ge, and P, and it is preferable that 50 mol % or more of G3 is B and P, more preferably 70 mol % or more of G3 is B and P, and particularly preferably 90 mol % or more of G3 is B and P.

<Light Emitting Device>
A light emitting device according to a second embodiment of the present invention comprises a semiconductor light emitting element that emits ultraviolet light or visible light, and a phosphor that absorbs the ultraviolet light or visible light emitted from the semiconductor light emitting element and emits light in the infrared region, wherein the phosphor that emits light in the infrared region has an emission peak wavelength in the infrared region between 700 and 1000 nm, and the half-width of the waveform of the emission peak is less than 60 nm.

The light emitting device according to the second embodiment is a light emitting device including a semiconductor light emitting element described below as a first light emitting body (excitation light source), and an infrared phosphor among the infrared phosphors according to the first embodiment described above as a second light emitting body that emits infrared light by irradiation with light from the first light emitting body, the infrared phosphor having an emission peak wavelength in the infrared region between 700 and 1000 nm and a half-width of the waveform of the emission peak being less than 60 nm. As the infrared phosphor, any one of the infrared phosphors may be used alone, or two or more of them may be used in any combination and ratio.

[Composition of phosphor]
A specific aspect of the infrared phosphor according to this embodiment refers to the first embodiment described above.
In order for the infrared phosphor according to this embodiment to have an emission peak wavelength in the infrared region between 700 and 1000 nm and a half-width of the waveform of the emission peak less than 60 nm, it is preferable to include at least two elements selected from rare earth metal elements and transition metal elements as activating elements. This is because, when the infrared phosphor emits light using ultraviolet light or visible light emitted from a semiconductor light-emitting element as excitation light, it is difficult to lengthen the emission wavelength to a desired wavelength with only one activating element. Therefore, it is preferable to use, as the activating element, a combination of an element that acts as a sensitizer and an element that acts as a light-emitting ion that is excited by the energy supplied from the sensitizer and emits light.

Among the activating elements, elements that act as sensitizers include, for example, Ce, Eu, Cr, Mn, Cu, and Sm. Elements that act as luminescent ions include, for example, Tm and Nd. By appropriately combining these elements, it is possible to obtain an infrared phosphor with high luminous efficiency without losing excitation energy from the semiconductor light-emitting element. From the viewpoint of the emission peak wavelength of the infrared phosphor, it is more preferable that the activating element contains at least thulium (Tm) and further contains at least one element selected from rare earth metal elements and transition metal elements. This is because Tm is a preferable element that acts as a luminescent ion.

The activating element other than Tm is preferably at least one of Cr, Mn, and Cu. These elements are particularly preferable as sensitizers that absorb light ranging from ultraviolet to visible light and allow Tm to function as a luminescent ion, and in combination with Tm, energy transition can be performed with high efficiency. Of these, the most preferable combination of activating elements is Tm and Cr.

[Characteristics of phosphor]
For specific characteristics of the infrared phosphor according to this embodiment, the above-mentioned first embodiment is used.
In particular, from the viewpoint of wavelength conversion efficiency, the minimum reflectance (%) of a phosphor emitting light in the infrared region between 350 and 700 nm is lower than the minimum reflectance (%) between 700 and 800 nm, and the difference between the two minimum reflectances is usually 20% or more, preferably 30% or more, more preferably 50% or more, and is usually less than 90%.

[Configuration of the Light-Emitting Device]
The light emitting device has a first light emitting body (excitation light source) and uses at least the infrared phosphor according to the present embodiment described above as a second light emitting body, but other than this, the configuration of the light emitting device is not limited and may take any known device configuration.
An example of the device configuration and the embodiment of the light emitting device is described in JP-A-2007-291352.
Other examples of the form of the light emitting device include a bullet type, a cup type, a chip-on-board type, and a remote phosphor type.

{Use of the light-emitting device}
The light emitting device can be used in any field in which a normal infrared light emitting device is used, for example, as a light source for an infrared monitoring device, a light source for an infrared sensor, an infrared light source for a medical diagnostic device, a light source for a transmitting element such as a photoelectric switch or a joystick for a video game, etc.

{Semiconductor light-emitting element}
The semiconductor light-emitting element included in the light-emitting device according to this embodiment is not particularly limited as long as it emits ultraviolet light or visible light and functions as an excitation light source. Since it is widely used as a semiconductor light-emitting element, it is inexpensive and easy to obtain, so it is preferable that the emission peak wavelength of the ultraviolet light or visible light emitted from the semiconductor light-emitting element is between 300 and 700 nm. The wavelength is more preferably 300 to 650 nm or 350 to 680 nm, and even more preferably 300 to 400 nm, 420 to 600 nm, 420 to 480 nm, or 600 to 650 nm.

<Method of manufacturing phosphor>
The method for producing an infrared phosphor according to the first embodiment can include a step of mixing raw materials such as chlorides, fluorides, oxides, carbonates, and nitrates of each element, a step of firing, a step of crushing, and a step of washing and classifying.

[Phosphor raw materials]
As the phosphor raw material used in the method for producing the phosphor according to the first embodiment, any known material can be used as long as it does not impair the effect of the phosphor according to the first embodiment produced by this embodiment. For example, chlorides, fluorides, oxides, carbonates, nitrates, etc. of each element can be used, but are not limited to these.

[Mixing process]
The phosphor raw materials are weighed out so as to obtain the target composition, thoroughly mixed using a ball mill or the like, then packed into a container, fired at a predetermined temperature and in a predetermined atmosphere, and the fired product is crushed and washed. For example, the chlorides, fluorides, oxides, carbonates, nitrates, etc. of the above elements are weighed out and mixed so that the molar ratios of the elements match those in the target composition formula.

The above mixing method is not particularly limited, and may be either a dry mixing method or a wet mixing method.
An example of the dry mixing method is a ball mill.
The wet mixing method is, for example, a method in which a solvent or dispersion medium is added to the above-mentioned phosphor raw material, mixed using a mortar and pestle to form a solution or slurry, and then dried by spray drying, heat drying, natural drying, or the like.
Examples of the solvent or dispersion medium include acetone, methanol, ethanol, 1-propanol, and 1-butanol, among which ethanol is preferred. The time for wet mixing is usually 5 minutes or more, preferably 15 minutes or more, and more preferably 30 minutes or more. Mixing may be repeated multiple times, usually once or more, preferably twice or more, and more preferably three times or more. In particular, mixing for 15 minutes or more, or mixing twice or more, is preferred because it allows the phosphor according to the first embodiment of the present invention to be obtained as the main phase.

[Firing process]
The mixture thus obtained is filled into a container made of a material having low reactivity with each of the phosphor raw materials. The material of the container used in such firing is not particularly limited as long as it does not impair the effect of the phosphor according to the first embodiment produced by this embodiment, and may be, for example, an alumina container.
The firing temperature varies depending on other conditions such as pressure, but firing can usually be performed within a temperature range of 300° C. or higher and 2000° C. or lower. The maximum temperature reached in the firing step is usually 300° C. or higher, preferably 1000° C. or higher, more preferably 1300° C. or higher, and usually 2000° C. or lower, preferably 1700° C. or lower. In particular, firing within a temperature range of 1400° C. or higher and 1600° C. or lower is preferable because it may be possible to obtain the phosphor according to the first embodiment of the present invention as the main phase.

If the firing temperature is too high, atomic deficiencies in the phosphor can induce defects in the crystal structure, tending to significantly reduce the luminescence characteristics. Conversely, if the firing temperature is too low, the solid-phase reaction can tend to proceed slowly, making it difficult for the target phase to be generated and for grain growth to proceed.
The pressure during the firing step varies depending on the firing temperature, etc., but is usually 0.01 MPa or more, preferably 0.05 MPa or more, and is usually 200 MPa or less, preferably 190 MPa or less.

The firing atmosphere in the firing step may be any as long as the desired phosphor is obtained, but specific examples include air, nitrogen, and reducing atmospheres containing hydrogen or carbon, among which a reducing atmosphere is preferred. The number of firings may be any as long as the desired phosphor is obtained, but after firing once, the resulting fired body may be crushed and then fired again, and there is no particular limit to the number of firings. In addition, when firing multiple times, the atmosphere for each firing may be different.

The firing time varies depending on the temperature and pressure during firing, but is usually at least 1 minute, preferably at least 30 minutes, and usually at most 72 hours, preferably at most 12 hours. If the firing time is too short, the particles will not grow, and a phosphor with good properties will not be obtained. If the firing time is too long, the constituent elements will volatilize, causing atomic deficiencies that induce defects in the crystal structure, making it impossible to obtain a phosphor with good properties.

[Cleaning process]
A step of washing the fired phosphor before dispersion and classification (washing step) may be included.
Impurities, mainly unreacted residues, and unreacted raw materials used in synthesizing the phosphor tend to remain in the phosphor, and by-reaction products tend to be generated in the phosphor slurry.
To improve the characteristics, it is necessary to remove as much of the unreacted residue and impurities generated during firing as possible. There are no particular limitations on the cleaning method as long as the impurities can be removed. For example, the generated phosphor can be cleaned with any liquid, such as acids such as hydrochloric acid, hydrofluoric acid, nitric acid, acetic acid, and sulfuric acid, water-soluble organic solvents, alkaline solutions, and mixtures thereof. The cleaning liquid may contain a reducing agent such as hydrogen peroxide, or the cleaning liquid may be heated or cooled within a range that does not significantly deteriorate the luminescence characteristics.

The time for immersing the phosphor in the cleaning solution varies depending on the stirring conditions, etc., but is usually 10 minutes or more, preferably 1 hour or more, and usually 72 hours or less, preferably 48 hours or less. Cleaning may be performed multiple times, and the type or concentration of the cleaning solution may be changed.
In the washing process, the phosphor is immersed in the solution and washed, then filtered and dried to produce the phosphor. Washing with ethanol, acetone, methanol, etc. may also be performed in between.

{Phosphor-containing composition}
The phosphor according to the first embodiment can be used by mixing with a liquid medium. In particular, when the phosphor according to the first embodiment is used for applications such as a light emitting device, it is preferable to use it in a form dispersed in a liquid medium.

[Phosphor]
When the phosphor according to the first embodiment is contained in a composition containing the phosphor, the type of the phosphor is not limited and can be selected from the phosphors according to the first embodiment described above. The phosphor may be only one type, or two or more types may be used in any combination and ratio. Furthermore, the composition may contain a phosphor other than the phosphor according to the first embodiment as long as the effect of the phosphor according to the first embodiment is not significantly impaired.

[Liquid medium]
The liquid medium used in the composition is not particularly limited as long as it does not impair the performance of the phosphor according to the first embodiment within the desired range. For example, any inorganic and/or organic material can be used as long as it exhibits liquid properties under desired use conditions, suitably disperses the phosphor according to the first embodiment, and does not cause undesirable reactions, such as silicone resin, epoxy resin, polyimide silicone resin, etc.

[Liquid medium and phosphor content]
The content of the phosphor according to the first embodiment and the liquid medium in the composition may be any content as long as it does not significantly impair the effect of the phosphor according to the first embodiment, but the content of the liquid medium is usually 30% by weight or more, preferably 50% by weight or more, and usually 99% by weight or less, preferably 95% by weight or less, based on the entire composition.

[Other ingredients]
In addition, the composition may contain other components in addition to the phosphor and the liquid medium, as long as the effects of the phosphor according to the first embodiment are not significantly impaired. In addition, the other components may be used alone or in any combination and ratio of two or more.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.
In addition, the values of various manufacturing conditions and evaluation results in the following examples are meant as preferred upper or lower limit values in each embodiment of the present invention, and a preferred range may be a range defined by a combination of the upper or lower limit value and the values of the following examples or values between the examples.

{Measuring method}
[Emission spectrum]
The emission spectrum was measured using a fluorescence spectrophotometer F-7000 (manufactured by Hitachi, Ltd.). More specifically, an emission spectrum was obtained within a wavelength range of 500 nm to 900 nm (in the case of Comparative Example 1-1 and Example 1-1), or 750 nm to 850 nm (in the case of Comparative Example 2-1, Examples 3-1 to 3-3, Examples 4-1 and 4-2) by irradiating with excitation light of 455 nm at room temperature (25° C.). The emission peak wavelength was read from the obtained emission spectrum.

[Measurement of light emitting device]
In Examples 1-2, 2-3, and 2-4, the emission spectrum of the infrared light-emitting device was measured using a small fiber optic spectrometer USB2000 (manufactured by Ocean Optics, Inc.) More specifically, the light-emitting device was turned on, and the emission spectrum of the light-emitting device was obtained in the wavelength range of 300 nm to 900 nm.

[Excitation spectrum]
The excitation spectrum was measured using a fluorescence spectrophotometer F-7000 (manufactured by Hitachi, Ltd.) More specifically, the infrared emission peak was monitored at room temperature (25° C.) to obtain an excitation spectrum in a wavelength range of 300 nm to 750 nm (in the case of Comparative Example 1-1 and Example 1-1) or 300 nm to 600 nm (in the case of Comparative Example 2-1, Examples 3-1 to 3-3, Examples 4-1 and 4-2).

[Powder X-ray diffraction measurement]
The powder X-ray diffraction was precisely measured using a powder X-ray diffractometer D8 ADVANCE ECO (manufactured by BRUKER) under the following measurement conditions.

CuKα tube used X-ray output = 40 kV, 25 mA
Divergence slit = automatic Detector = semiconductor array detector LYNXEYE, Cu filter used Scanning range 2θ = 5 to 90 degrees (in the case of Comparative Example 1-1 and Example 1-1), or 5 to 90 degrees (in the case of Comparative Example 2-1, Examples 3-1 to 3-3, Examples 4-1 and 4-2)
Reading width = 0.025 degrees

[Reflectance measurement]
In Examples 1-1, 2-1, 3-1, and 4-1, the reflectance was measured using a spectrophotometer U-3310 (manufactured by Hitachi, Ltd.). More specifically, BaSO ₄ particles and the phosphor particles of the examples were each spread in a quartz cell. Using BaSO ₄ particles as a reference sample, the reflectance (%) of the phosphor particles of the examples was measured as a relative value to the reflectance of BaSO ₄ particles in the wavelength range of 300 nm to 900 nm.

(Comparative Example 1-1: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be Y _2.97 Tm _0.03 Ga ₅ O ₁₂ , and a YGG:Tm ³⁺ phosphor was produced.
The raw materials were commercially available Y ₂ O ₃ powder (SY-OR-P-1622 manufactured by Shin-Etsu Chemical Co., Ltd.),
_A2O3 powder ( _Mitsui Metals 90402) and _Tm2O3 powder (Shin-Etsu Chemical TM-04-001) were used. Each raw material was weighed so that the molar ratio of the cations was _Y :Ga:Tm = 2.97:5.00:0.03. These raw materials were mixed in an alumina mortar after adding ethanol, and the ethanol was naturally dried before being placed in an alumina container. The container containing the mixed raw materials was placed in a small electric furnace (Motoyama Superburn) and heated at 1500 ° C for 8 hours in air to obtain a fired body. The fired body was crushed in the alumina mortar until no large lumps remained, obtaining a phosphor.

The emission spectrum of the obtained phosphor is shown by a thin line in Figure 1-1, and the excitation spectrum is shown by a thin line in Figure 1-2. Note that the excitation light wavelength of the emission spectrum was 463 nm, and the emission wavelength of the excitation spectrum was 808 nm. Figure 1-1 shows that the phosphor of this comparative example has an infrared emission peak around 800 nm.

(Example 1-1: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be Y _2.97 Tm _0.03 Ga _4.75 Cr _0.25 O ₁₂ , and a YGG:Cr ³⁺ ,Tm ³⁺ phosphor was produced.
As raw materials, commercially available Y ₂ O ₃ powder (SY-OR-P-1622 manufactured by Shin-Etsu Chemical Co., Ltd.), Ga ₂ O ₃ powder (90402 manufactured by Mitsui Metals Co., Ltd.), Cr ₂ O ₃ powder (B58840N manufactured by Kishida Chemical Co., Ltd.), and Tm ₂ O ₃ powder (TM-04-001 manufactured by Shin-Etsu Chemical Co., Ltd.) were used. Each raw material was weighed so that the molar ratio of the cations was Y:Ga:Cr:Tm = 2.97:4.75:0.25:0.03, and other than that, the mixture was mixed and heated in the same manner as in Comparative Example 1-1 to obtain a phosphor.

The XRD pattern obtained by performing powder X-ray diffraction measurement on this phosphor is shown in FIG. 1-3. It can be seen that this phosphor is composed of single-phase YGG. The emission spectrum of this phosphor is shown in FIG. 1-1, and the excitation spectrum is shown in FIG. 1-2, both of which are shown by thick lines. The excitation light wavelength of the emission spectrum was 440 nm, and the emission wavelength of the excitation spectrum was 825 nm. From FIG. 1-1, it can be seen that the phosphor of this example has a strong infrared emission peak around 800 nm, which is six times stronger than the phosphor of Comparative Example 1-1. Specifically, the wavelengths at which peaks are observed in the emission spectrum around 800 nm are 794 nm and 825 nm, and the waveforms of these peaks are observed overlapping, but the half-widths were 27.4 nm and 16.3 nm, respectively. The overlapping emission peaks were regarded as one emission peak, and the half-widths of the waveforms of the emission peaks were measured. As a result, the emission peak wavelength was 794 nm, and the half-width of the waveform of the emission peak was 49.5 nm. Also, from FIG. 1-2, it can be seen that the phosphor of this example is excited by light in a wide wavelength band from blue to red, and emits infrared light.
Furthermore, the minimum reflectance R1 (%) of this phosphor in the wavelength range of 350 to 700 nm and the minimum reflectance R2 (%) in the wavelength range of 700 to 800 nm were measured, and the difference R1-R2 (%) was calculated. The results are shown in Table 1.

(Example 1-2: Manufacturing of a light-emitting device)
An infrared light emitting device was fabricated by combining YGG:Cr ³⁺ , Tm ³⁺ with a blue LED.
The phosphor obtained in Example 1-1 and thermosetting silicone resin were used as raw materials. Each raw material was weighed so that the weight ratio of phosphor to thermosetting silicone resin was 15:85. These raw materials were mixed using an EME V-mini300, and the mixture was applied to a package equipped with a commercially available blue LED (Showa Denko K.K.) and cured to obtain a light-emitting device. The emission spectrum of the light-emitting device is shown in FIG. 1-4. It can be seen that the light-emitting device has an ambient infrared emission peak at approximately 800 nm.

(Comparative Example 2-1: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be La _1.98 Tm _0.02 MgGeO ₆ , and a La ₂ MgGeO ₆ :Tm ³⁺ phosphor was produced.
As raw materials, commercially available La ₂ O ₃ powder (LA-04-153 manufactured by Shin-Etsu Chemical Co., Ltd.), MgO powder (LKG5947 manufactured by Wako Pure Chemical Industries, Ltd.), GeO ₂ powder (313826 manufactured by High Purity Chemical Laboratory Co., Ltd.), and Tm ₂ O ₃ powder (TM-04-001 manufactured by Shin-Etsu Chemical Co., Ltd.) were used. Each raw material was weighed so that the molar ratio of the cations was La:Mg:Ge:Tm = 1.98:1.00:1.00:0.02. These raw materials were mixed in an alumina mortar after adding ethanol, and then placed in an alumina container after naturally drying the ethanol. The container containing the mixed raw materials was placed in a small electric furnace (Superburn manufactured by Motoyama Co., Ltd.) and heated at 1400 ° C. in air for 8 hours to obtain a fired body. The fired body was crushed in the alumina mortar until no large lumps remained, to obtain a phosphor.

The emission spectrum of the obtained phosphor is shown by a thin line in Figure 2-1, and the excitation spectrum is shown by a thin line in Figure 2-2. Note that the excitation light wavelength of the emission spectrum was 455 nm, and the emission wavelength of the excitation spectrum was 798 nm. From Figure 2-1, it can be seen that the phosphor of this comparative example does not have an infrared emission peak around 800 nm.

(Example 2-1: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be La _1.98 Tm _0.02 MgGe _0.99 Mn _0.01 O ₆ , and a La ₂ MgGeO ₆ :Mn ⁴⁺ ,Tm ³⁺ phosphor was produced.
As raw materials, commercially available La ₂ O ₃ powder (LA-04-153 manufactured by Shin-Etsu Chemical Co., Ltd.), MgO powder (LKG5947 manufactured by Wako Pure Chemical Industries, Ltd.), GeO ₂ powder (313826 manufactured by Kojundo Chemical Laboratory Co., Ltd.), Tm ₂ O ₃ powder (TM-04-001 manufactured by Shin-Etsu Chemical Co., Ltd.), and MnO ₂ powder (194474 manufactured by Kojundo Chemical Laboratory Co., Ltd.) were used. Each raw material was weighed so that the molar ratio of cations was La:Mg:Ge:Tm:Mn = 1.98:1.00:0.99:0.02:0.01, and the mixture was mixed and heated in the same manner as in Comparative Example 2-1 to obtain a phosphor.

The XRD pattern obtained by performing powder X-ray diffraction measurement on this phosphor is shown in Figure 2-3. It is clear that this phosphor is composed of single- _{phase La2MgGeO6} .
The emission spectrum of this phosphor is shown by a thick line in FIG. 2-1, and the excitation spectrum is shown by a thick line in FIG. 2-2. The excitation light wavelength of the emission spectrum was 455 nm, and the emission wavelength of the excitation spectrum was 798 nm. From FIG. 2-1, it can be seen that the phosphor of this example has a strong infrared emission peak around 800 nm. The emission peak wavelength was 798 nm, and the half-width of the waveform of the emission peak was 14.4 nm. From FIG. 2-2, it can be seen that the phosphor of this example is excited by light in a wide wavelength band from ultraviolet to blue, and emits infrared light.
Furthermore, the minimum reflectance R1 (%) of this phosphor in the wavelength range of 350 to 700 nm and the minimum reflectance R2 (%) in the wavelength range of 700 to 800 nm were measured, and the difference R1-R2 (%) was calculated. The results are shown in Table 1.

(Example 2-2: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be La _1.98 Tm _0.02 MgTi _0.99 Mn _0.01 O ₆ , and a La ₂ MgTiO ₆ :Mn ⁴⁺ ,Tm ³⁺ phosphor was produced.
As raw materials _, commercially available _La2O3 powder (LA-04-153 manufactured by Shin-Etsu Chemical Co., Ltd.), Mg(OH) ₂ powder (83480D manufactured by Kojundo Chemical Laboratory Co., Ltd.), _TiO2 powder (LAG1626 manufactured by Wako _Pure Chemical Industries Co., Ltd.), _Tm2O3 powder (TM-04-001 manufactured by Shin-Etsu Chemical Co., Ltd.), and _MnO2 powder (194474 manufactured by Kojundo Chemical Laboratory Co., Ltd.) were used. Each raw material was weighed so that the molar ratio of the cations was La:Mg:Ti:Tm:Mn = 1.98:1.00:0.99:0.02:0.01. Other than that, the mixture was mixed and heated in the same manner as in Example 2-1 to obtain a phosphor.
The XRD pattern obtained by performing powder X-ray diffraction measurement on this phosphor is shown in Figure 2-6, _which shows that this phosphor is composed of single-phase _La2MgTiO6 .
The emission spectrum of this phosphor is shown by a thick line in FIG. 2-4, and the excitation spectrum is shown by a thick line in FIG. 2-5. The excitation light wavelength of the emission spectrum was 455 nm, and the emission wavelength of the excitation spectrum was 804 nm. From FIG. 2-4, it can be seen that the phosphor of this example has a strong infrared emission peak around 800 nm. The emission peak wavelength was 804 nm, and the half-width of the waveform of the emission peak was 26.2 nm. From FIG. 2-5, it can be seen that the phosphor of this example is excited by light in a wide wavelength band from ultraviolet to blue, and emits infrared light.

(Example 2-3: Production of a light-emitting device)
An infrared light emitting device was fabricated by combining the phosphor La ₂ MgGeO ₆ :Mn ⁴⁺ , Tm ³⁺ obtained in Example 2-1 with a blue LED.
The phosphor obtained in Example 2-1 and thermosetting silicone resin were used as raw materials. Each raw material was weighed so that the weight ratio of phosphor to thermosetting silicone resin was 15:85. These raw materials were mixed using an EME V-mini300, and the mixture was applied to a package equipped with a commercially available blue LED (Showa Denko K.K.) and cured to obtain a light-emitting device. The emission spectrum of the light-emitting device is shown in FIG. 2-7. It can be seen that the light-emitting device has an infrared emission peak around 800 nm.

(Example 2-4: Production of a light-emitting device)
An infrared light emitting device was produced by combining the phosphor La ₂ MgTiO ₆ :Mn ⁴⁺ , Tm ³⁺ obtained in Example 2-2 with a blue LED.
The phosphor obtained in Example 2-2 and a thermosetting silicone resin were used as raw materials. Other than that, the same weighing, coating, and curing were performed as in Example 2-3 to obtain a light-emitting device. The emission spectrum of the light-emitting device is shown in Figure 2-8. It can be seen that the light-emitting device has an infrared emission peak around 800 nm.

(Example 3-1: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be La _0.95 Tm _0.05 MgAl _10.67 Cr _0.33 O ₁₉ , and a LaMgAl ₁₁ O ₁₉ :Cr ³⁺ ,Tm ³⁺ phosphor was produced.
The raw materials used _were commercially available La(OH) ₃ powder (manufactured by High Purity Chemical Research Institute), MgO powder (manufactured by Wako Pure Chemical Industries, Ltd.), _Al2O3 powder (manufactured by Sumitomo Chemical Co., Ltd.), _Cr2O3 powder (manufactured by Kishida Chemical Co. _, Ltd.), and _{Tm2O3 powder} (manufactured by Shin-Etsu Chemical Co., Ltd.). Each raw material was weighed so that the molar ratio of the cations was La:Tm:Mg:Al:Cr = 0.95:0.05:1.00:10.67:0.33. After adding 5 wt% of _H3BO3 powder (manufactured by _Wako Pure Chemical Industries, Ltd.) to these raw materials externally, ethanol was added in an alumina mortar and then wet-mixed, the ethanol was naturally dried, and then the mixture was placed in an alumina container. The container containing the mixed raw materials was placed in a small electric furnace (Superburn manufactured by Motoyama Co., Ltd.) and heated at 1500 ° C. in air for 8 hours to obtain a sintered body. The fired body was crushed in an alumina mortar until no large lumps remained, to obtain a phosphor.
Furthermore, the minimum reflectance R1 (%) of this phosphor in the wavelength range of 350 to 700 nm and the minimum reflectance R2 (%) in the wavelength range of 700 to 800 nm were measured, and the difference R1-R2 (%) was calculated. The results are shown in Table 1.

The emission spectrum of the obtained phosphor is shown by a solid line in Fig. 3-1, and the excitation spectrum is shown by a dotted line in Fig. 3-2. The excitation light wavelength of the emission spectrum was 455 nm, and the emission wavelength of the excitation spectrum was 809 nm.
It can be seen from Fig. 3-1 that the phosphor of this example has an infrared emission peak with a narrow half-width at 809 nm. Also, it can be seen from Fig. 3-2 that the phosphor of this example is excited by light in a wide wavelength band from ultraviolet to blue, and emits infrared light. The half-width of the emission peak waveform at the emission peak wavelength of 809 nm was 50 nm.
The XRD pattern obtained by carrying out powder X-ray diffraction measurement of the phosphor of this example is shown in Fig. 3-3. It is found that the phosphor of this example is made of LaMgAl ₁₁ O ₁₉ .

(Example 3-2: Production of phosphor)
The phosphor of Example 3-2 was obtained in the same manner as in Example _{3-1 ,} except that the raw materials were mixed so that the phosphor obtained after synthesis had _a composition of _{La0.95Tm0.05MgAl10.89Cr0.11O19} . According to the emission spectrum when the obtained phosphor was irradiated with _excitation light having a wavelength of 455 nm, it was confirmed that the phosphor of this example had an infrared emission peak with a narrow half-width at 801 nm.

(Example 3-3: Production of phosphor)
The phosphor of Example 3-3 was obtained in the same _manner as in Example _{3-1 ,} except that the raw materials were mixed so that the phosphor obtained after synthesis would have a structure of _{La0.99Tm0.01MgAl10.67Cr0.33O19} . According to the emission spectrum when the obtained phosphor was _irradiated with excitation light having a wavelength of 455 nm, the phosphor of this example was confirmed to have an infrared emission peak with a narrow half-width at 798 nm.

(Example 4-1: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be La ₅ Al _0.99 Cr _0.01 Ti ₃ O ₁₅ , and a La ₅ AlTi ₃ O ₁₅ :Cr ³⁺ phosphor was produced.
The raw materials used were commercially available La(OH) ₃ powder (manufactured by Kojundo Kagaku Kenkyusho ₎ , _TiO2 powder (manufactured by Furuuchi Chemical), _Al2O3 powder (manufactured by Sumitomo Chemical), and _Cr2O3 powder (manufactured by Kishida Chemical). Each raw material was weighed so that the molar ratio of the cations was La:Al:Cr:Ti = ₅ :0.99:0.01:3. After adding ₂ wt% _H3BO3 powder (manufactured by Wako Pure Chemical Industries) to these raw materials externally, ethanol was added in an alumina mortar and then wet-mixed. The ethanol was naturally dried and then placed in an alumina container. The container containing the mixed raw materials was placed in a small electric furnace (Superburn, manufactured by Motoyama Co., Ltd.) and heated at 1500 ° C. for 8 hours in air to obtain a fired body. The fired body was crushed in the alumina mortar until no large lumps remained, obtaining a phosphor.

The emission spectrum of the obtained phosphor is shown by a solid line in Fig. 4-1, and the excitation spectrum is shown by a dotted line in Fig. 4-2. The excitation light wavelength of the emission spectrum was 455 nm, and the emission wavelength of the excitation spectrum was 753 nm.
It can be seen from Fig. 4-1 that the phosphor of this example has an infrared emission peak with a narrow half-width at 753 nm. Also, it can be seen from Fig. 4-2 that the phosphor of this example is excited by light in a wide wavelength band from ultraviolet to blue, and emits infrared light. The half-width of the emission peak waveform at the emission peak wavelength of 753 nm was 41 nm.

The XRD pattern obtained by performing powder X-ray diffraction measurement of the phosphor of this example is shown in Figure 4-3. It can be seen that the phosphor of this example is mainly composed of La ₅ AlTi ₃ O _15. The peak indicated by the arrow in Figure 4-3 is LaAlO ₃ by-produced as an impurity phase. Since the peak intensity in Figure 4-3 is small, and further, the emission of LaAlO ₃ :Cr usually has a maximum emission peak at about 737 nm and has multiple weak emission peaks between 735 nm and 755 nm, it can be said that the infrared emission peak with a narrow half-width at 753 nm observed above is derived from La ₅ AlTi ₃ O ₁₅ .
Furthermore, the minimum reflectance R1 (%) of this phosphor in the wavelength range of 350 to 700 nm and the minimum reflectance R2 (%) in the wavelength range of 700 to 800 nm were measured, and the difference R1-R2 (%) was calculated. The results are shown in Table 1.

(Example 4-2: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be La ₅ Al _0.95 Cr _0.05 Ti ₃ O ₁₅ , and a La ₅ AlTi ₃ O ₁₅ :Cr ³⁺ phosphor was produced.
The raw materials used were commercially available La(OH) ₃ powder (manufactured by Kojundo Kagaku Kenkyusho ₎ , _TiO2 powder (manufactured by Showa Denko), _Al2O3 powder (manufactured by Sumitomo Chemical), and _Cr2O3 powder (manufactured by Kishida Chemical). Each raw material was weighed so that the molar ratio of the cations was La:Al:Cr:Ti = ₅ :0.95:0.05:3. Ethanol was added to an alumina mortar and then wet mixed, the ethanol was naturally dried, and the mixture was placed in an alumina container. The container containing the mixed raw materials was placed in a small electric furnace (Superburn, manufactured by Motoyama Co., Ltd.) and heated at 1600 ° C. for 8 hours in air to obtain a fired body. The fired body was crushed in the alumina mortar until no large lumps remained, to obtain a phosphor.
According to the emission spectrum when the obtained phosphor was irradiated with excitation light having a wavelength of 455 nm, it was confirmed that the phosphor of this example had an infrared emission peak with a narrow half-value width at 752 nm.

(Example 5-1: Production of phosphor)
The raw materials were mixed so that the phosphor obtained after synthesis would be Sr _0.96 Sm _0.03 Tm _0.01 BPO ₅ , and a SrBPO ₅ :Sm ²⁺ ,Tm ³⁺ phosphor was produced.
The raw materials used were commercially available _SrHPO4 powder (Hakutatsu Chemical Co., Ltd.), _Sm2O3 powder ₍ Mitsuwa Chemical Co., Ltd.), _Tm2O3 powder (Shin-Etsu Chemical Co., Ltd.), and _H3BO3 powder ( _Wako Pure Chemical Industries, Ltd.). Each raw material was weighed so that the molar ratio of the cations was _Sr :Sm:Tm = 0.96:0.03:0.01, mixed, and then placed in an alumina container. The container containing the mixed raw materials was placed in a tubular furnace and heated at 950 ° C. for 8 hours in a reducing atmosphere ( _N2 (96%) + _H2 (4%)) to obtain a fired body. The fired body was crushed in an alumina mortar until no large lumps remained, to obtain a phosphor.
The emission spectrum of the obtained phosphor when irradiated with light having a wavelength of 455 nm is shown by a solid line in Figure 5-1, and the excitation spectrum for an emission wavelength of 810 nm is shown by a dotted line. In Figure 5-1, the half-width of the emission peak waveform between wavelengths of 800 nm and 850 nm was 23 nm. As can be seen from Figure 5-1, the phosphor of this example is excited in a wide range of wavelengths from 300 nm to 600 nm, and has an infrared emission peak with a narrow half-width between wavelengths of 800 nm and 850 nm.

5-2 shows the XRD pattern obtained by carrying out powder X-ray diffraction measurement of the phosphor of this example. It is clear that the phosphor of this example is made of _SrBPO5 .

Claims (4)

The host crystal contains a crystalline phase having divalent samarium (Sm) and trivalent thulium (Tm) as activation elements, absorbs ultraviolet light or visible light, and has an emission peak wavelength within a wavelength range of 800 to 1000 nm ,
A phosphor, characterized in that the host crystal contains a crystalline phase having a chemical composition represented by the following formula (5-1):
G1 _1-a G2 _a G3 _b O ₅ ... (5-1)
however,
G1 represents one or more metal elements selected from alkaline earth metal elements;
G2 represents two or more metal elements selected from rare earth metal elements, essentially including Sm and Tm;
G3 represents two or more metal elements selected from B, Al, Ga, Si, Ge, and P;
O represents oxygen;
0<a<0.2 and 1.5<b<2.5. A semiconductor light emitting element that emits ultraviolet light or visible light;
a phosphor that absorbs ultraviolet light or visible light emitted from the semiconductor light emitting element and emits light in the infrared region,
The phosphor emitting light in the infrared region includes the phosphor according to claim 1 ,
A light emitting device, characterized in that the phosphor emitting light in the infrared region has an emission peak wavelength in the infrared region between 700 and 1000 nm, and the half-value width of the waveform of the emission peak is less than 60 nm. 3. The light emitting device according to claim 2, wherein the minimum reflectance (%) of the phosphor emitting light in the infrared region in the wavelength range of 350 to 700 nm is lower than the minimum reflectance (%) in the wavelength range of 700 to 800 nm, the difference being 20 % or more. 4. The light emitting device according to claim 2, wherein the peak emission wavelength of ultraviolet light or visible light emitted from said semiconductor light emitting element is between 300 and 700 nm.

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