Near-infrared light-emitting phosphor and light-emitting device

Abstract

To provide a near-infrared light-emitting phosphor having an emission component in the range of 1300 nm or more and 1650 nm or less, and a light-emitting device.SOLUTION: A near-infrared light-emitting phosphor according to the present invention is composed of an inorganic compound in which Cr is added to an inorganic crystal selected from the group consisting of Na2ZnGeO4 crystals, Na2ZnSiO4 crystals, K2ZnSiO4 crystals, and K2MgSiO4 crystals, wherein the phosphor emits near-infrared light having a peak in the wavelength range of 1300 nm or more and 1350 nm or less, where the full width at half maximum of the peak is 200 nm or more and 300 nm or less.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a near-infrared light-emitting phosphor and a light-emitting device including a light source and the phosphor. [Background technology]

[0002] Light-emitting diodes (LEDs) using GaAs-based or InP-based compound semiconductors such as InGaAs and AlGaAs are known as light-emitting devices that emit near-infrared light. These LEDs are widely used in various remote control sensors, security, in-vehicle cameras, and inspection of packages, contents, and foreign objects. In addition, light in the near-infrared region has excellent biological permeability, making it suitable for quality inspection applications in the medical, agricultural, and food fields, and for measuring vital information such as hemoglobin and oxygen concentration in blood.

[0003] In addition, in near-infrared spectroscopy, sensing of substances is performed using very weak light absorption due to overtones and combination tones, rather than the fundamental vibrations of the functional groups of organic compounds (CH, OH, NH, SH, C=O, etc.). For example, the bonds of organic functional groups have various absorption peaks in the wavelength range of 690 to 3000 nm. From the long wavelength side, return absorption peaks are seen, such as the first combination tone, the first overtone, the second combination tone, and the second overtone, and this is particularly important for light that corresponds to the second overtone of bonds such as water and CH, which appears in the 1350 to 1500 nm band, so a strong light source in this band is particularly important.

[0004] Recently, a light emitting device that emits near-infrared light has been developed (see, for example, Patent Document 1). Patent Document 1 discloses a light emitting device that uses a near-infrared light emitting phosphor in which Cr is added to M(1)2M(2)M(3)O4 crystal (wherein M(1) is a metal element that is Li and / or Na, M(2) is at least one metal element selected from the group consisting of Zn, Mg, Ca, and Sr, and M(3) is an element that is Si and / or Ge).

[0005] Light sensing using such a light emitting device using a near-infrared light emitting phosphor in combination with an InGaAs detector, which has a sensitivity band of 1300 nm to 1650 nm, is expected to become possible. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-1880044 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0007] In response to the above demand, an object of the present invention is to provide a near-infrared light-emitting phosphor having an emission component of 1300 nm or more and 1650 nm or less, and a light-emitting device. [Means for solving the problem]

[0008] The near-infrared light-emitting phosphor of the present invention comprises an inorganic compound in which Cr is added to an inorganic crystal selected from the group consisting of Na2ZnGeO4 crystal, Na2ZnSiO4 crystal, K2ZnSiO4 crystal, and K2MgSiO4 crystal, and has a peak in a wavelength range of 1300 nm or more and 1350 nm or less, and the half-width of the peak is 200 nm or more and 300 nm or less, thereby solving the above-mentioned problems. The Na2ZnGeO4 crystal and the Na2ZnSiO4 crystal may be monoclinic crystals having the symmetry of the space group Pc, and the K2ZnSiO4 crystal and the K2MgSiO4 crystal may be orthorhombic crystals having the symmetry of the space group Pca21. The inorganic compound is Na2ZnGe 1-x Cr x O4, Na2ZnSi 1-x Cr x O4, K2ZnSi 1-x Cr x O4 and K2MgSi 1-x Cr xO4 (wherein x satisfies 0.0005≦x≦0.1). The inorganic compound has the general formula Na2ZnGe 1-x Cr x O4 (where x satisfies 0.0005≦x≦0.1). The peak may fill the wavelength range of 1310 nm or more and 1330 nm or less. The half width of the peak may be 240 nm or more and 300 nm or less. The parameter x may satisfy 0.005≦x≦0.08. The emission intensity at the emission wavelength of 1650 nm is 1 / e 2 (e is Napier's constant). The Cr may be tetravalent. The light emitting device of the present invention comprises a light source and a phosphor, and the phosphor contains the near-infrared light emitting phosphor described above, thereby solving the above problems. Effect of the Invention

[0009] The near-infrared light-emitting phosphor of the present invention is made of an inorganic compound in which Cr is added to an inorganic crystal selected from the group consisting of Na2ZnGeO4 crystal, Na2ZnSiO4 crystal, K2ZnSiO4 crystal, and K2MgSiO4 crystal, and as a result, not only does the peak wavelength shift to the long wavelength side to a wavelength range of 1300 nm to 1350 nm, but the half-width of the peak becomes 200 nm to 300 nm. Since such a near-infrared light-emitting phosphor has a light-emitting component of 1300 nm to 1650 nm, it is possible to provide a light-emitting device that enables optical sensing in combination with an InGaAs detector. [Brief description of the drawings]

[0010] [Figure 1] Diagram showing the crystal structure of Na2ZnGeO4 crystal [Diagram 2] Powder X-ray diffraction using CuKα radiation calculated from the crystal structure of Na2ZnGeO4 crystal [Diagram 3]Schematic diagram illustrating the effectiveness of the near-infrared emitting phosphor of the present invention. [Figure 4] Schematic diagram showing a light-emitting device of the present invention. [Diagram 5] FIG. 1 is a schematic diagram showing another light-emitting device of the present invention. [Figure 6] FIG. 1 shows the powder X-ray diffraction pattern of the product of Example 1. [Figure 7] FIG. 1 shows the emission spectrum of the product of Example 1. [Figure 8] FIG. 1 shows another emission spectrum of the product of Example 1. [Figure 9] Figure showing the excitation spectrum of the product of Example 1 [Figure 10] FIG. 1 shows emission spectra of the products of Examples 1, 7, and 10 to 13. [Figure 11] FIG. 1 shows the emission spectra of the products of Examples 8, 9 and 16. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that similar elements are given similar numbers and their description will be omitted. In this specification, a numerical range expressed using "~" means a range including the numerical values ​​before and after "~" as the lower and upper limits.

[0012] (Embodiment 1) In the first embodiment, a near-infrared emitting phosphor and a method for producing the same of the present invention will be described.

[0013] The near-infrared light-emitting phosphor of the present invention is composed of an inorganic compound in which Cr (chromium) is added to an inorganic crystal selected from the group consisting of Na2ZnGeO4 crystal, Na2ZnSiO4 crystal, K2ZnSiO4 crystal, and K2MgSiO4 crystal, and is excited mainly with red light or near-infrared light having a wavelength range of 600 nm or more and 1200 nm or less to emit near-infrared light. The near-infrared light-emitting phosphor of the present invention is preferably efficiently excited with red light having a wavelength range of 600 nm or more and 800 nm or less to emit near-infrared light.

[0014] In detail, according to Patent Document 1, as described above, numerous host crystal possibilities are disclosed by combining a plurality of elements. However, the present inventors have discovered that, among these, an inorganic crystal selected from the group consisting of a specific Na2ZnGeO4 crystal, a Na2ZnSiO4 crystal, and a K2ZnSiO4 crystal and K2MgSiO4 crystal not disclosed in Patent Document 1 is used as a host crystal, and by adding Cr to this, the host crystal is excited by red light or near-infrared light, emits near-infrared light, and the emission peak wavelength is shifted to the longer wavelength side.

[0015] Specifically, the peak wavelength satisfies the range of 1300 nm to 1350 nm, and the half width of the peak wavelength is in the range of 200 nm to 300 nm. As a result, the near-infrared light-emitting phosphor of the present invention is excited by red light or near-infrared light, and the luminescent component of 1300 nm to 1650 nm is enhanced, so that a light-emitting device that realizes optical sensing in combination with an InGaAs detector can be provided.

[0016] Each host crystal will now be described in detail. (1) Na2ZnGeO4 crystal FIG. 1 is a diagram showing the crystal structure of a Na2ZnGeO4 crystal.

[0017] The Na2ZnGeO4 crystal belongs to the monoclinic system and the Pc space group (space group No. 7 in the International Tables for Crystallography), and has the crystal parameters and atomic coordinate positions shown in Table 1.

[0018] In Table 1, the lattice constants a, b, and c indicate the lengths of the axes of the unit cell, and α, β, and γ indicate the angles between the axes of the unit cell. The atomic coordinates indicate the position of each atom in the unit cell, with values ​​between 0 and 1 in the unit cell. In this crystal, Cr 4+ is incorporated into the crystal by substituting part of the Ge (germanium).

[0019] [Table 1]

[0020] Na2ZnGeO4 crystals are composed of Na (sodium), Zn (zinc), Ge (germanium) and O (oxygen), but the ratio of the constituent elements may vary and Na:Zn:Ge:O may not necessarily be 2:1:1:4. Even in such cases, as long as the crystal structure is maintained, it is called Na2ZnGeO4 crystal.

[0021] In the present invention, when the lattice constants and the lengths of the chemical bonds of Na-O and Zn-O calculated from the atomic coordinates obtained by Rietveld analysis of the results of X-ray diffraction or neutron diffraction in the Pc space group (the distance between adjacent atoms) are within ±5% of the lengths of the chemical bonds calculated from the lattice constants and atomic coordinates of the Na2ZnGeO4 crystal shown in Table 1, the crystal structure is defined as being the same, and it may be determined whether or not it is a Na2ZnGeO4 crystal.

[0022] Alternatively, there is the following simple method for identifying Na2ZnGeO4 crystals: When the lattice constant calculated from the X-ray diffraction results measured for a new substance and the diffraction peak position (2θ) calculated using the crystal structure data in Table 1 match for the main peak, the crystal structure can be identified as being the same.

[0023] FIG. 2 shows powder X-ray diffraction using CuKα radiation calculated from the crystal structure of Na2ZnGeO4 crystal.

[0024] By comparing the X-ray diffraction patterns of the substances to be compared with FIG. 2, it is possible to easily determine whether the substance is a Na2ZnGeO4 crystal or not. It is recommended to determine the main peaks of the Na2ZnGeO4 crystal by about 10 peaks with strong diffraction intensity. In that sense, Table 1 is important as a standard for identifying the Na2ZnGeO4 crystal. In addition, an approximate structure can be defined by using a crystal system other than the monoclinic system as the crystal structure of the Na2ZnGeO4 crystal. In that case, the expression will be made using a different space group, lattice constant, and plane index, but the X-ray diffraction results (e.g., FIG. 2) and the crystal structure (e.g., FIG. 1) will not change, and the identification method and identification results using them will also be the same. For this reason, in the present invention, the X-ray diffraction analysis will be performed as a monoclinic system.

[0025] (2) Na2ZnSiO4 crystals The Na2ZnSiO4 crystal belongs to the orthorhombic crystal system and the Pc space group (space group No. 7 in the International Tables for Crystallography), and has the crystal parameters and atomic coordinate positions shown in Table 2.

[0026] Table 2 a-c and α-γ are the same as Table 1. Cr 4+ is incorporated into the crystal by substituting part of the Si (silicon).

[0027] [Table 2]

[0028] Here too, as in the case of (1) Na2ZnGeO4 crystal, the deviation in the ratio of the constituent elements and the crystal structure may be identified.

[0029] (3) K2ZnSiO4 crystal The K2ZnSiO4 crystal belongs to the orthorhombic crystal system and the Pca21 space group (space group No. 29 in the International Tables for Crystallography), and has the crystal parameters and atomic coordinate positions shown in Table 3.

[0030] Table 3 a-c and α-γ are the same as Table 1. Cr 4+ is incorporated into the crystal by substituting part of the Si (silicon).

[0031] [Table 3]

[0032] Here too, as in the case of (1) Na2ZnGeO4 crystal, the deviation in the ratio of the constituent elements and the crystal structure may be identified.

[0033] (4) K2MgSiO4 crystal The K2ZnSiO4 crystal belongs to the orthorhombic crystal system and the Pca21 space group (space group No. 29 in the International Tables for Crystallography), and has the crystal parameters and atomic coordinate positions shown in Table 4.

[0034] Table 4 a-c and α-γ are the same as Table 1. Cr 4+ is incorporated into the crystal by substituting part of the Si (silicon).

[0035] [Table 4]

[0036] Here too, as in the case of (1) Na2ZnGeO4 crystal, the deviation in the ratio of the constituent elements and the crystal structure may be identified.

[0037] The inorganic compound contained in the near infrared emitting phosphor of the present invention is not particularly limited as long as it is an inorganic crystal selected from the group consisting of the above-mentioned Na2ZnGeO4 crystal, Na2ZnSiO4 crystal, K2ZnSiO4 crystal, and K2MgSiO4 crystal to which Cr has been added. However, it is preferably Na2ZnGe 1-x Cr x O4, Na2ZnSi 1-x Cr x O4, K2ZnSi 1-xCr x O4 and K2MgSi 1-x Cr x O4 (where x satisfies 0.0005≦x≦0.1). This results in a near-infrared phosphor with enhanced emission components in the wavelength range of 1300 nm to 1650 nm.

[0038] Among these, the inorganic compound is more preferably represented by the general formula Na2ZnGe 1-x Cr x O4 (0.0005≦x≦0.1). As a result, the emission peak particularly satisfies the range of 1310 nm or more and 1330 nm or less, and the peak half width particularly satisfies the range of 240 nm or more and 300 nm or less, resulting in a near-infrared phosphor in which the emission component of 1300 nm or more and 1650 nm or less is particularly enhanced.

[0039] The parameter x is the amount of Cr added, and within the above-mentioned range, the amount of luminescent ions is sufficient and there is no decrease in luminescence intensity due to concentration quenching. The parameter x preferably satisfies 0.005≦x≦0.08. Within this range, a near-infrared phosphor with high luminescence intensity can be obtained with a small amount of luminescent ions.

[0040] Cr may have various valences, but preferably contains tetravalent Cr. Therefore, the inorganic crystals in which Cr is added to each of Na2ZnGeO4 crystal, Na2ZnSiO4 crystal, K2ZnSiO4 crystal, and K2MgSiO4 crystal are called Na2ZnGeO4:Cr 4+ , Na2ZnSiO4:Cr 4+ , K2ZnSiO4:Cr 4+ , and K2MgSiO4:Cr 4+ It may also be expressed as:

[0041] FIG. 3 is a schematic diagram illustrating the effectiveness of the near-infrared light-emitting phosphor of the present invention.

[0042] FIG. 3 illustrates, using a typical emission spectrum of the near-infrared light-emitting phosphor of the present invention, how the emission peak is in the wavelength range of 1300 nm or more and 1350 nm or less, and the half-width of the peak is in the range of 200 nm or more and 300 nm or less, thereby enhancing the emission component in the emission spectrum from 1300 nm to 1650 nm or less, and enabling combination with an InGaAs detector.

[0043] FIG. 3 shows an emission spectrum 310 having a peak in the wavelength range of 1300 nm or more and 1350 nm or less and whose half-width falls within the range of 200 nm or more and 300 nm or less, emission spectra 320 and 330 having peaks in the wavelength range less than 1300 nm, and the photosensitivity curve (dotted line) of the InGaAs detector.

[0044] Emission spectrum 310 is the emission spectrum of the near-infrared light-emitting phosphor of the present invention and is the emission spectrum of Example 1 described below. Emission spectrum 320 is the emission spectrum of Example 10 described below, and emission spectrum 330 is the emission spectrum of Example E described below. Comparing emission spectrum 310 with emission spectra 320 and 330, it can be seen that the emission component of emission spectrum 310 between 1300 nm and 1650 nm (the region shown in gray in FIG. 3) is extremely large.

[0045] Moisture (HO) and organic functional groups (CH, OH, NH, etc.), which are important targets for measurement in this wavelength range, have significant absorption peaks in the 1400 to 1500 nm region, but the emission intensity in the above region of the emission spectrum 310 is more than half the peak intensity, so an extremely good signal-to-noise ratio can be obtained. According to the emission spectrum 310, the intensity at a wavelength of 1650 nm is 1 / e of the peak intensity. 2 (e is Napier's constant), so a good signal-to-noise ratio can be obtained.

[0046] In contrast, the emission spectra 320 and 330 are 1 / e 2 Naturally, the intensity at a wavelength of 1650 nm is 1 / e2 This makes it difficult to obtain a sufficient signal-to-noise ratio.

[0047] Even if the peak is in the wavelength range of 1300 nm or more and 1350 nm or less, if the half-width is less than 200 nm, it is difficult to obtain a good signal-to-noise ratio because the intensity is not more than half the peak intensity in the 1400-1500 nm region. Conversely, if the half-width exceeds 300 nm, the absolute value of the peak intensity becomes low for a certain quantum efficiency, making it difficult to obtain a sufficient signal-to-noise ratio. For this reason, it is desirable for the half-width to be in the range of 200-300 nm.

[0048] In this way, the near-infrared light-emitting phosphor of the present invention has a peak in the wavelength range of 1300 nm to 1350 nm, and the half-width is in the range of 200 nm to 300 nm, so that the emission component in the range of 1300 nm to 1650 nm is dramatically improved, and detection with high sensitivity is possible using an InGaAs detector. Preferably, the emission intensity at the emission wavelength of 1650 nm of the near-infrared light-emitting phosphor of the present invention is 1 / e of the intensity of the emission peak wavelength. 2 This results in a good signal / noise ratio. The upper limit of the emission intensity at the emission wavelength of 1650 nm is smaller than the emission peak wavelength, and is preferably half the emission peak wavelength.

[0049] If the near-infrared light-emitting phosphor of the present invention is composed of an inorganic compound that is a particle (single crystal particle or aggregate of single crystals) with a median average particle size of 0.1 μm to 50 μm, the light-emitting efficiency is high and the operability when mounting it in an LED is good, so it is preferable to control the particle size to this range. More preferably, the particles may have a median average particle size of 0.1 μm to 20 μm. This improves the dispersibility in the components (e.g., light-transmitting body) that constitute the LED, and enables highly efficient excitation.

[0050] The median average particle diameter d50 is defined as follows. In the case of measurement by the sedimentation method, the particle diameter is defined as the diameter of a sphere with an equivalent sedimentation velocity, and in the case of measurement by the laser scattering method, the particle diameter is defined as the diameter of a sphere with equivalent scattering characteristics. The distribution of particle diameters is called particle size (particle diameter) distribution. In the particle diameter distribution, the particle diameter when the total mass of particles larger than a certain particle diameter accounts for 50% of that of the total powder is defined as the average particle diameter d50. This definition and terminology are both well known to those skilled in the art, and are described in various documents, such as JIS Z8901 "Test Powders and Test Particles" or Chapter 1 of "Basic Properties of Powders" (ISBN4-526-05544-1) compiled by the Powder Technology Society. In the present invention, the sample was dispersed in water to which sodium hexamethacrylate was added as a dispersant, and the cumulative frequency distribution in volume terms for the particle diameter was measured using a laser scattering type measuring device. The volume-converted and weight-converted distributions are equal. The particle size corresponding to 50% in this cumulative frequency distribution was determined and taken as the median average particle size d50. It should be noted that in the following description, the average particle size is based on the median value (d50) of the particle size distribution measured by the particle size distribution measuring means using the laser scattering method described above. Regarding the means for determining the average particle size, various means other than those described above have been developed and are still being developed, and there may be slight differences in the measured values, but it should be understood that the meaning and significance of the average particle size itself is clear and is not necessarily limited to the means described above.

[0051] The near-infrared light-emitting phosphor of the present invention may preferably be made of a powder having an average aspect ratio of primary particles of 1 or more and 20 or less. This is preferable because it is easy to disperse in the light transmission constituting the LED, thereby increasing the emission intensity. The average aspect ratio of the primary particles is obtained by randomly selecting 100 particles in five fields of view of a scanning electron microscope photograph, measuring the major axis and minor axis of the particles, calculating the value of the major axis / minor axis as the aspect ratio, and calculating the proportion of particles with an aspect ratio of 20 or less.

[0052] The impurity elements Fe, Co, and Ni contained in inorganic compounds may reduce the emission intensity. By keeping the total content of these elements in the phosphor at 500 ppm or less, the effect of the reduction in emission intensity is reduced.

[0053] When the near-infrared light-emitting phosphor of the present invention alone does not provide the desired emission spectrum, it is advisable to add another phosphor. For example, in addition to the near-infrared light-emitting phosphor of the present invention, Li2CaSiO4:Cr 4+ Phosphor and Li2MgGeO4:Cr 4+ Phosphor and Li2ZnSiO4:Cr 4+ It is possible to add a fluorescent substance and combine it with a detector having a sensitivity band in the range of 950 nm to 1650 nm. Such modifications will be understood by those skilled in the art.

[0054] The near-infrared light-emitting phosphor of the present invention is excited not only by red light or near-infrared light having a peak in the wavelength range of 600 nm or more and 1200 nm or less as described above, but also by light (blue-purple and blue) having a peak in the wavelength range of 380 nm or more and 480 nm or less, and can emit near-infrared light having a peak in the wavelength range of 1300 nm or more and 1350 nm or less and having a half-width of 200 nm or more and 300 nm or less.

[0055] The method for producing the near-infrared emitting phosphor of the present invention is not particularly limited, but the phosphor can be obtained by firing a starting material prepared from a mixture of compounds containing the metal elements constituting the above-mentioned host crystal and Cr (chromium) such that the composition ratio of the metal elements is the composition ratio of the above-mentioned host crystal in an oxygen-containing atmosphere at a temperature range of more than 700°C to 1500°C.

[0056] The starting material varies depending on the host crystal, but here we will take the case of Na2ZnGeO4 crystal as an example. As the starting material, it is recommended to use a compound containing Na (sodium), a compound containing Zn (zinc), a compound containing Ge (germanium), and a compound containing Cr (chromium).

[0057] As the starting material, the Na-containing compound may be selected from the group consisting of a Na-containing metal (Na metal), a silicide, and a carbonate, the Na-containing compound may be selected from the group consisting of a Zn-containing metal (Na metal), a silicide, and a carbonate, the Ge-containing compound may be selected from the group consisting of a Ge-containing metal (Ge metal), a silicide, and a carbonate, and the Cr-containing compound may be selected from the group consisting of a Cr-containing metal (Cr metal), a silicide, and a carbonate. These raw materials are easy to obtain and have excellent stability.

[0058] The furnace used for sintering is not particularly limited as long as it is capable of sintering in an oxygen-containing atmosphere such as air, and an atmospheric furnace can be used. As for the sintering method, a sintering method that does not use hot pressing and does not apply mechanical pressure from the outside, such as normal pressure sintering or gas pressure sintering, is preferred as a method for obtaining a powder or aggregate product.

[0059] The firing temperature should be higher than 700°C and lower than 1500°C. At temperatures lower than 700°C, the reaction may not proceed sufficiently. At temperatures higher than 1500°C, the raw material powder and the compound may decompose. The firing time varies depending on the firing temperature, but is usually between 1 hour and 48 hours.

[0060] To manufacture phosphor in powder or aggregate form, it is recommended to fill the raw material in a container (e.g., an alumina crucible) with a bulk density of 40% or less and then sinter it. By keeping the bulk density at 40% or less, it is possible to avoid strong adhesion between particles. Here, the relative bulk density is the ratio of the mass of the powder filled in the container divided by the volume of the container (bulk density) to the true density of the powder material.

[0061] To manufacture phosphors in powder or aggregate form, it is preferable to set the average particle size of the raw material powder particles or aggregates to 500 μm or less, as this provides excellent reactivity and operability. As a method for setting the particle size of the particles or aggregates to 500 μm or less, it is preferable to use a spray dryer, sieving, or air classification, as these methods provide excellent work efficiency and operability.

[0062] The average particle size of the phosphor powder is preferably 0.1 μm or more and 50 μm or less in volume median diameter (d50) because it has high luminescence intensity. The volume average particle size can be measured, for example, by a microtrack or laser scattering method. The average particle size of the phosphor powder synthesized by firing can be adjusted to 0.1 μm or more and 50 μm or less by using one or more methods selected from pulverization, classification, and acid treatment.

[0063] The near-infrared light-emitting phosphor of the present invention can be obtained by firing in an oxygen-containing atmosphere, but since the valence-fluctuation Cr becomes tetravalent Cr and the luminescence intensity is improved, a reduction treatment may be performed. Such a reduction treatment is a heat treatment in a reducing atmosphere containing reducing gases such as hydrogen, carbon monoxide, hydrocarbons, and ammonia at a temperature range of 500°C to 1200°C.

[0064] The reducing atmosphere may be composed of a mixed gas of 2% by volume to 10% by volume of a reducing gas, and the remainder being an inert gas such as argon. The heat treatment time of the reduction treatment is not particularly limited, but is illustratively in the range of 1 hour to 24 hours.

[0065] (Embodiment 2) In the second embodiment, a light emitting device using the near infrared light emitting phosphor of the present invention will be described.

[0066] FIG. 4 is a schematic diagram showing a light emitting device of the present invention.

[0067] 4 shows a bullet-shaped light-emitting diode lamp as a specific example of the light-emitting device 1. The light-emitting diode lamp as the light-emitting device includes a light source 4 and at least a near-infrared light-emitting phosphor 7 as a phosphor, thereby emitting near-infrared light. The near-infrared light-emitting phosphor 7 is the near-infrared light-emitting phosphor of the present invention described in the first embodiment, and therefore a description thereof will be omitted.

[0068] In the light emitting device 1 in Fig. 4, a light emitting source 4 is placed in a recess 2a in a lead wire 2 for mounting an element, the lead wire 2 and a lower electrode 4a of the light emitting source 4 are electrically connected, and an upper electrode 4b of the light emitting source 4 and the lead wire 3 are electrically connected by a bonding wire 5. The light emitting source 4 is covered with a first resin 6 having a near-infrared light emitting phosphor 7 dispersed therein, and the entire element is sealed with a second resin 8. Although a specific configuration example is shown in Fig. 4, it is merely an example, and a person skilled in the art can easily modify it within a normal range.

[0069] The light emission source 4 applied to the light emitting device 1 is not particularly limited in wavelength as long as it can excite the near-infrared light emitting phosphor 7, but preferably emits light having a peak in the wavelength range of 600 nm to 1200 nm. This allows the near-infrared light emitting phosphor 7 of the present invention to efficiently absorb light in the range of 600 nm to 1200 nm, increasing the emission intensity.

[0070] The light emitting source 4 is preferably at least one selected from the group consisting of a light emitting diode (LED), a laser diode (LD), an inorganic electroluminescence (inorganic EL), and an organic electroluminescence (organic EL). These light emitting sources can emit light in the above-mentioned wavelength range.

[0071] More preferably, the light emission source 4 is an LED or laser diode that emits light having a peak in the wavelength range of 600 nm to 800 nm and uses at least one semiconductor selected from the group consisting of GaAs, AlGaAs, GaP, GaAlP, and AlGaInP. Among them, a red LED is preferable because it is inexpensive and has a high emission intensity. As such an LED or laser diode, GaAs, AlGaAs, GaP, GaAlP, and AlGaInP are preferable because they have strong red emission and are easy to excite the phosphor of the present invention.

[0072] When the light source 4 is an LED, the light emitting device can be manufactured by a known method such as those described in Japanese Patent Application Laid-Open Nos. 5-152609 and 7-99345 using an excitation LED and a phosphor.

[0073] In such a light emitting device 1, when electricity flows to the light emitting source 4 via the lead wire 2, the light emitting source 4 emits red light or near infrared light, for example, light having a peak in a wavelength range of 600 nm to 1200 nm. The near infrared light emitting phosphor 7 is excited by the red light or near infrared light emitted by the light emitting source 4, and emits near infrared light having a peak in a wavelength range of 1300 nm to 1350 nm and a half width of 200 nm to 300 nm. In this manner, the light emitting device 1 of the present invention operates.

[0074] FIG. 5 is a schematic diagram showing another light emitting device of the present invention.

[0075] 5 shows a chip-type light-emitting diode lamp for mounting on a substrate as a specific example of the light-emitting device 11. The light-emitting diode lamp as the light-emitting device 11 includes a light emission source 14 and a near-infrared light-emitting phosphor 17 that is excited as a phosphor to emit near-infrared light, thereby emitting near-infrared light.

[0076] In the light emitting device 11 of Fig. 5, a light emitting source 14 is placed on a lead wire 12 fixed on a substrate 19, the lead wire 12 is electrically connected to a lower electrode 14a of the light emitting source 14, and an upper electrode 14b of the light emitting source 14 is electrically connected to a lead wire 13 by a bonding wire 15. The light emitting source 14 is covered with a first resin 16 in which a near-infrared light emitting phosphor 17 is dispersed, and the entire element is sealed with a second resin 18. A wall member 20 having a hole in the center is fixed on the substrate 19. Although a specific configuration example is shown in Fig. 5, it is only one example, and a person skilled in the art can easily modify it within a normal range.

[0077] Here, the light emitting source 14 and the near-infrared light emitting phosphor 17 are similar to the light emitting source 4 and the near-infrared light emitting phosphor 7 described in Fig. 4, respectively, and therefore the description thereof will be omitted. Also, the same components as those in Fig. 4 are given the same names, and the description thereof will be omitted.

[0078] In such a light emitting device 11, when electricity flows to the light emitting source 14 via the lead wire 12, the light emitting source 14 emits red light or near infrared light, for example, light having a peak in a wavelength range of 600 nm to 1200 nm. The near infrared light emitting phosphor 17 is excited by the red light or near infrared light emitted by the light emitting source 14 and emits near infrared light having a peak in a wavelength range of 1300 nm to 1350 nm and a half width of 200 nm to 300 nm. In this manner, the light emitting device 11 of the present invention operates.

[0079] 4 and 5, the near-infrared light-emitting phosphor 17 is excited not only by red light or near-infrared light, but also by light having a peak in the wavelength range of 380 nm or more and 480 nm or less (blue-violet and blue), so a light-emitting source such as an LED or laser diode that emits light having a peak in the wavelength range of 380 nm or more and 480 nm or less (blue-violet and blue) may be used. Some of these light-emitting elements are made of nitride semiconductors such as GaN and InGaN, and by adjusting the composition, they can become a light source that emits light of a specified wavelength.

[0080] In this case, the difference between Figures 4 and 5 is that the light emitting sources 4 and 14 emit light having a peak in the wavelength range of 300 nm or more and 480 nm or less, and further contain, as the phosphor, a red phosphor that is excited by the light emitting source and emits red light, in addition to the near-infrared light emitting phosphors 7 and 17.

[0081] The light emitting source emits light having a peak in the wavelength range of 300 nm to 480 nm. Such a light emitting source is at least one selected from the group consisting of the above-mentioned light emitting diode, LD, inorganic EL, and organic EL. Among them, the light emitting source is preferably an LED or a laser diode. Some of these light emitting elements are made of nitride semiconductors such as GaN and InGaN, and can be used as a light source that emits light of a specified wavelength by adjusting the composition.

[0082] The red phosphor is excited by light emitted by the light source and having a peak in the wavelength range of 300 nm to 480 nm, and emits light (red light) having a peak in the wavelength range of 600 nm to 800 nm. As a result, the red light from the red phosphor excites the near-infrared light-emitting phosphor, which emits near-infrared light having a peak in the wavelength range of 1300 nm to 1350 nm and a half-width of 200 nm to 300 nm.

[0083] There are no restrictions on the material of the red phosphor as long as it can convert light in the wavelength range of 300 nm to 480 nm into light having a peak in the wavelength range of 600 nm to 800 nm, but among them, α-sialon:Eu (e.g., JP 2002-363554 A), Ca2Si5N8:Eu, (Ca,Sr)2Si5N8:Eu, CaAlSiN3:Eu (e.g., WO 2005 / 052087 pamphlet), (Ca,Sr)AlSiN3:Eu, etc. are preferred because of their high conversion efficiency. Here, ":Eu" means that Eu is added to each of the base materials.

[0084] For example, in the case of the light emitting device 1 shown in FIG. 4, when electricity flows through the light emitting source via the lead wire 2, the light emitting source emits blue light, for example, light having a peak in a wavelength range of 300 nm to 480 nm. The red phosphor is excited by this blue light and converts the blue light into light having a peak in a wavelength range of 600 nm to 800 nm. Next, the near-infrared light emitting phosphor 7 is excited by the converted light having a peak in a wavelength range of 600 nm to 800 nm, and emits near-infrared light having a peak in a wavelength range of 1300 nm to 1350 nm and a half width of 200 nm to 300 nm. In this way, the light emitting device 1 of the present invention operates.

[0085] Similarly, in the case of the light emitting device 11 shown in FIG. 5, when electricity flows through the light emitting source via the lead wire 12, the light emitting source emits blue light, for example, light having a peak in a wavelength range of 300 nm to 480 nm. The red phosphor is excited by this blue light and converts the blue light into light having a peak in a wavelength range of 600 nm to 800 nm. Next, the near-infrared light emitting phosphor 17 is excited by the converted light having a peak in a wavelength range of 600 nm to 800 nm, and emits near-infrared light having a peak in a wavelength range of 1300 nm to 1350 nm and a half width of 200 nm to 300 nm. In this way, the light emitting device 11 of the present invention operates.

[0086] In both of these light-emitting devices 1 and 11, the near-infrared light emitted by the light-emitting device 1 has a peak in the wavelength range of 1300 nm or more and 1350 nm or less, with a half-width of 200 nm or more and 300 nm or less, and the luminescent components of 1300 nm or more and 1650 nm or less are enhanced, making it possible to perform optical sensing in combination with an InGaAs detector, whose sensitivity range is 1300 nm or more and 1650 nm or less. EXAMPLES

[0087] The present invention will be described in more detail by the following examples. However, these examples are merely disclosed as an aid to easily understand the present invention, and the present invention is not limited to these examples.

[0088] [Raw materials used in synthesis] The raw material powders used in the synthesis were chromium oxide (Cr2O3, Kojundo Chemical Laboratory Co., Ltd.), lithium carbonate (Li2CO3, Kojundo Chemical Laboratory Co., Ltd.), sodium carbonate (Na2CO3, Kojundo Chemical Laboratory Co., Ltd.), potassium carbonate (K2CO3, Kojundo Chemical Laboratory Co., Ltd.), zinc oxide (ZnO, Kojundo Chemical Laboratory Co., Ltd.), magnesium oxide (MgO, Kojundo Chemical Laboratory Co., Ltd.), calcium carbonate (CaCO3, Kojundo Chemical Laboratory Co., Ltd.), strontium oxide (SrO, Kojundo Chemical Laboratory Co., Ltd.), germanium oxide (Ge2O, Kojundo Chemical Laboratory Co., Ltd.), and silicon dioxide powder (SiO2, Kojundo Chemical Laboratory Co., Ltd.).

[0089] [Near-infrared emitting phosphors: Examples 1 to 17] In Examples 1 to 17, near-infrared light-emitting phosphors were synthesized. Specifically, according to the design composition in Table 5, raw material powders were weighed out so as to satisfy the mixed composition in Table 6, and mixed for 25 minutes using a pestle and mortar made of sintered silicon nitride. The mixed powder obtained was then placed in an alumina crucible. The bulk density of the mixed powder (powder) was about 33%.

[0090] The crucible containing the mixed powder was placed in an atmospheric furnace and fired. The mixed powders of Examples 1 to 13 and Examples 15 to 17 were heated to 1000°C at a rate of 300°C per hour, held at 1000°C for 6 hours, and then allowed to cool to room temperature. The mixed powder of Example 14 was heated to 1200°C at a rate of 300°C per hour, held at 1200°C for 6 hours, and then allowed to cool to room temperature.

[0091] The fired product was thoroughly crushed, placed in an alumina crucible again, and then placed in an electric furnace for reduction treatment. Specifically, the products of Examples 1 to 17 were reduced at 700°C for 5 hours while flowing a mixed gas of 3 volume % hydrogen gas and the remainder argon gas at a flow rate of 1.0 L.

[0092] [Table 5]

[0093] [Table 6]

[0094] The products of Examples 1 to 17 were identified by powder X-ray diffraction (Ultima IV, manufactured by Rigaku Corporation). The excitation emission spectra of the obtained products were measured using a near-infrared spectrofluorometer (FP-8700, manufactured by JASCO Corporation). The results are shown in Figures 6 to 10 and Table 7.

[0095] FIG. 6 shows the powder X-ray diffraction pattern of the product of Example 1.

[0096] The XRD pattern in FIG. 6 matches well with the XRD pattern of Na2ZnGeO4 crystals by structural analysis shown in FIG. 2, and no secondary phase was confirmed. From this, it was confirmed that the product of Example 1 is a crystal having the same crystal structure as Na2ZnGeO4 crystals. Although not shown, it was also confirmed that the products of Examples 2 to 6 are crystals having the same crystal structure as Na2ZnGeO4 crystals. It was confirmed that the products of Examples 7 to 9 are crystals having the same crystal structure as Na2ZnSiO4 crystals, K2ZnSiO4 crystals, and K2MgSiO4 crystals, respectively.

[0097] FIG. 7 shows the emission spectrum of the product of Example 1. FIG. 8 shows another emission spectrum of the product of Example 1. FIG. 9 shows the excitation spectrum of the product of Example 1. FIG. 10 is a diagram showing the emission spectra of the products of Examples 1, 7, and 10 to 13. FIG. 11 shows the emission spectra of the products of Examples 8, 9 and 16.

[0098] FIG. 7 shows the emission spectrum when the product of Example 1 was irradiated with red light having a wavelength of 650 nm. According to FIG. 7, the product of Example 1 was excited with red light having a wavelength range of 600 nm to 800 nm, and emitted light having a peak at 1320 nm. This showed that the product of Example 1 is an inorganic compound in which Cr is added to Na2ZnGeO4 crystal, and functions as a near-infrared light-emitting phosphor. In addition, the half-width of the emission peak (1320 nm) of the product of Example 1 was 245 nm, as shown in Table 7. This showed that the added Cr was tetravalent. Furthermore, according to FIG. 7, the emission intensity at the emission peak (1320 nm) was 5590 in relative comparison, and the emission intensity at a wavelength of 1650 nm was 780, which was 1 / e of the emission intensity of the emission peak. 2 (about 0.135) exceeded.

[0099] Figure 8 shows the emission spectrum when the product of Example 1 is irradiated with blue light having a wavelength of 470 nm. According to Figure 8, it was shown that the product of Example 1 is excited by light (blue-purple and blue) having a peak in the wavelength range of 380 nm or more and 480 nm or less, and functions as a near-infrared light-emitting phosphor that emits near-infrared light having a peak at 1320 nm. In addition, the half-width of the peak of the product of Example 1 was 245 nm.

[0100] Figure 9 shows the excitation spectrum of the product of Example 1 when the emission wavelength is fixed at 1320 nm. According to Figure 9, it was found that the product of Example 1 can be excited with light having a wavelength range of 380 nm to 480 nm, is efficiently excited with light having a wavelength range of 600 nm to 800 nm, and emits near-infrared light having a peak at 1320 nm and a half-width of 200 nm to 300 nm. Although not shown, it was confirmed that the product of Example 1 can also be excited with light having a wavelength range of 800 nm to 1200 nm.

[0101] Fig. 10 shows the emission spectra when the products of Examples 7 and 10 to 13 are irradiated with red light having a wavelength of 650 nm. The emission spectrum of the product of Example 1 in Fig. 10 is the same as that in Fig. 7. Fig. 11 shows the emission spectra when the products of Examples 8, 9 and 16 are irradiated with red light having a wavelength of 650 nm.

[0102] According to Fig. 10, the product of Example 7 was excited with red light having a wavelength range of 600 nm to 800 nm and had a peak at 1310 nm. This shows that the product of Example 7 is an inorganic compound in which tetravalent Cr is added to Na2ZnSiO4 crystals, and functions as a near-infrared light-emitting phosphor. In addition, the half-width of the peak of the product of Example 7 was 245 nm, as shown in Table 7.

[0103] According to Fig. 11, the products of Example 8 and Example 9 were excited with red light having a wavelength range of 600 nm or more and 800 nm or less, and had a peak at 1310 nm. From this, it was shown that the products of Example 8 and Example 9 are inorganic compounds in which tetravalent Cr is added to K2ZnSiO4 crystal and K2MgSiO4 crystal, respectively, and function as near-infrared light-emitting phosphors. In addition, the half-width of the peak of the products of Example 8 and Example 9 was 240 nm, as shown in Table 7.

[0104] On the other hand, the products of Examples 10 to 13 and 16 were all excited by red light having a wavelength range of 600 nm to 800 nm, but had a peak wavelength of less than 1300 nm. Although not shown, it was confirmed that the products of Examples 14, 15 and 17 were also excited by red light having a wavelength range of 600 nm to 800 nm, but had a peak wavelength of less than 1300 nm.

[0105] The emission wavelengths (excitation wavelength: 650 nm) and emission intensities of the products of Examples 1 to 17 are summarized in Table 7. In Table 7, the emission intensities are shown as relative intensities to the emission intensity of the product of Example 1. Table 7 also shows the emission wavelengths and peak half-widths of phosphors A, B1 to B5, and C to F described in Patent Document 1.

[0106] [Table 7]

[0107] According to Table 7, the products of Examples 1 to 9 were shown to be near-infrared light-emitting phosphors that emit near-infrared light and are made of inorganic compounds in which tetravalent Cr is added to inorganic crystals selected from the group consisting of Na2ZnGeO4 crystals, Na2ZnSiO4 crystals, K2ZnSiO4 crystals, and K2MgSiO4 crystals, and have a peak in the wavelength range of 1300 nm to 1350 nm, with the half-width of the peak being 200 nm to 300 nm. 4+ It was found that the phosphors are near-infrared light-emitting phosphors with excellent emission intensity. Examples 10 to 17 and phosphors A, B1 to B5, and C to F described in Patent Document 1, in which Cr was added to the host crystal other than those described above, all had peaks in the wavelength range of less than 1300 nm, and no enhancement of the emission component in the wavelength range of 1300 nm or more and 1650 nm or less was confirmed. [Industrial Applicability]

[0108] The near-infrared light-emitting phosphor of the present invention has a peak in the wavelength range of 1300 nm to 1350 nm, and the half-width of the peak is 200 nm to 300 nm, so that the luminescent component of 1300 nm to 1650 nm is enhanced. A light-emitting device including such a near-infrared light-emitting phosphor enables optical sensing in combination with an InGaAs detector, the sensitivity band of which is the wavelength range of 1300 nm to 1650 nm. [Explanation of symbols]

[0109] 1. Light-emitting device (bullet-type light-emitting diode lamp) 2, 3 Lead Wires 4. Light Source 5 Bonding Wire 6. First Resin 7. Near-infrared emitting phosphors 8 Second Resin 11 Light-emitting device (chip-type white light-emitting diode lamp for board mounting) 12, 13 Lead wire 14 Luminous source 14a Lower electrode 14b Upper electrode 15 Bonding Wire 16 First Resin 17 Near-infrared emitting phosphors 18 Second Resin 19 Substrate 20 Wall components

Claims

1. Na ２ ZnGeO ４ Crystal, Na ２ ZnSiO ４ crystal, K ２ ZnSiO ４ Crystals, and K ２ MgSiO ４ It consists of an inorganic compound in which Cr is added to an inorganic crystal selected from the group consisting of crystals. It has a peak in the wavelength range of 1300 nm to 1350 nm. A near-infrared emitting phosphor that emits near-infrared light, wherein the full width at half maximum of the aforementioned peak is between 200 nm and 300 nm.

2. The aforementioned Na ２ ZnGeO ４ crystal and the aforementioned Na ２ ZnSiO ４ crystal are monoclinic crystals, having the symmetry of space group Pc, The aforementioned K ２ ZnSiO ４ Crystal and the K ２ MgSiO ４ The crystal is an orthorhombic crystal, and its space group is Pca2 １ A near-infrared emitting phosphor according to claim 1, having the symmetry of the following.

3. The inorganic compound is Na ２ ZnGe １－ｘ Cr ｘ O ４ Na ２ ZnSi １－ｘ Cr ｘ O ４ _K ２ ZnSi １－ｘ Cr ｘ O ４ , and, K ２ MgSi １－ｘ Cr ｘ O ４ The near-infrared emitting phosphor according to claim 1, which is represented by a general formula selected from the group consisting of (where x satisfies 0.0005 ≤ x ≤ 0.1).

4. The aforementioned inorganic compound is of the general formula Na ２ ZnGe １－ｘ Cr ｘ O ４ The near-infrared emitting phosphor according to claim 3, represented as (where x satisfies 0.0005 ≤ x ≤ 0.1).

5. The near-infrared emitting phosphor according to claim 4, wherein the peak satisfies a wavelength range of 1310 nm to 1330 nm.

6. The near-infrared emitting phosphor according to claim 4, wherein the full width at half maximum of the peak is 240 nm or more and 300 nm or less.

7. The near-infrared emitting phosphor according to claim 3, wherein parameter x satisfies 0.005 ≤ x ≤ 0.

08.

8. The emission intensity at an emission wavelength of 1650 nm is 1 / e of the emission intensity of the peak. ２ A near-infrared emitting phosphor according to claim 1, wherein e exceeds Napier's number.

9. The near-infrared emitting phosphor according to claim 1, wherein the Cr is tetravalent.

10. A light-emitting device comprising a light-emitting source and a phosphor, The light-emitting device comprises a near-infrared light-emitting phosphor according to any one of claims 1 to 9.

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