Ultraviolet wavelength conversion element and ultraviolet spectrometry device

Abstract

To provide an ultraviolet spectrometry device having an excellent wavelength resolution by the manner of a new ultraviolet wavelength conversion element.SOLUTION: The ultraviolet wavelength conversion element according to the present invention converts an input ultraviolet ray into at least two visible lights with different wavelengths. The wavelength of the ultraviolet ray is calculated from the intensity ratio information of the visible lights formed through the conversion. Also, obtaining the wavelength of the input ultraviolet ray from the intensity ratio of visible lights with different wavelengths can realize an ultraviolet spectrometry device with an excellent wavelength resolution.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultraviolet wavelength conversion element having excellent wavelength resolution, and an ultraviolet spectroscopic measuring device having excellent wavelength resolution. [Background technology]

[0002] Ultraviolet rays are electromagnetic waves with wavelengths of 10-400 nm, shorter than visible light and longer than X-rays. Due to its short wavelength, ultraviolet rays are known to have a more significant chemical effect on substances than visible light. The near-ultraviolet region, with wavelengths of 200-380 nm, is classified more finely from the perspective of its impact on human health and the environment. Specifically, the UVA region, with wavelengths of 320-400 nm, causes sunburn on the human body and is used industrially to harden resin hardeners and paints. Next, the UVB region, with wavelengths of 280-320 nm, is known to activate skin cells in the human body and cause inflammation. Furthermore, the UVC region, with wavelengths of 200-280 nm, is characterized by its strong bactericidal effect.

[0003] In recent years, advances in medicine and biology have revealed that UVC rays, especially those in the wavelength range around 265 nm, react specifically with DNA, which contains the genetic information of living organisms and viruses. As a result, it has been confirmed that UVC rays have a strong bactericidal effect and a high inactivating effect on viruses by destroying the DNA replicating function. In addition, since this is a wavelength range that also affects the human body, it is expected that the wavelengths will be detected more accurately.

[0004] However, due to its invisibility, the technology for detecting ultraviolet light is generally inferior to that for visible light. Therefore, in the field of ultraviolet light detection methods, many techniques have been considered for converting ultraviolet light into the visible light range using fluorescent materials and the like, and many patents have been disclosed.

[0005] Among them, perovskite oxides doped with rare earth ions are expected to be a phosphor material with thermal and chemical stability. For example, Patent Document 1 discloses a technique for converting ultraviolet light with a wavelength of 200 to 400 nm into visible light with a wavelength of 600 nm or more by doping a small amount of praseodymium ions into a perovskite oxide containing calcium, strontium, and titanium, and then forming the oxide into nanoparticles. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP2014-34609 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology of Patent Document 1 absorbs ultraviolet light in a wide range of wavelengths, from 220 to 370 nm. Therefore, it is currently difficult to distinguish between the UVC region, which has a strong sterilizing effect, and other wavelengths. In other words, the conventional technology does not have sufficient wavelength resolution in the ultraviolet wavelength region that is expected by the market. An object of the present invention is to provide an ultraviolet spectrometry device with excellent wavelength resolution by using a novel ultraviolet wavelength conversion element. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention has the following features. An ultraviolet wavelength conversion element according to an embodiment of the present invention includes a light input section that receives ultraviolet light, and a light conversion section that converts the ultraviolet light received by the light input section into visible light. The visible light has at least two or more different wavelengths specific to the light conversion section, and the wavelength of the ultraviolet light is calculated from intensity ratio information of the converted visible light having different wavelengths.

[0009] In addition, an ultraviolet spectrometry device according to an embodiment of the present invention includes the ultraviolet wavelength conversion element, a spectroscopic unit that divides the visible light output from the ultraviolet wavelength conversion element into wavelengths, a first photodetector that measures the intensity of a first wavelength among the visible light divided by the spectroscopic unit, and a second photodetector that measures the intensity of a second wavelength among the visible light.The output of the second photodetector is divided by the output of the first photodetector, and the wavelength of the input ultraviolet light is calculated from the division result. Effect of the Invention

[0010] According to the embodiment of the present invention, an ultraviolet wavelength conversion element having a new function of calculating the wavelength of ultraviolet light from the intensity ratio information of visible light having two or more different wavelengths is realized. In addition, by using the ultraviolet wavelength conversion element, an ultraviolet spectroscopic measurement device with excellent wavelength resolution can be realized. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of an ultraviolet wavelength conversion element according to the present invention; [Diagram 2] FIG. 1 is a diagram showing the configuration of an ultraviolet spectrometry device according to the present invention. [Diagram 3] FIG. 1 is a diagram showing an example of a crystal lattice of a phosphor material used in an ultraviolet wavelength conversion element of the present invention. [Figure 4] A graph showing an example of the wavelength spectrum of ultraviolet light input to an ultraviolet wavelength conversion element of the present invention and the wavelength spectrum of visible light output. [Diagram 5] Graph showing an example of the intensity ratio between an input ultraviolet wavelength and two output visible light wavelengths when using the ultraviolet ray measuring device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (First embodiment) The first embodiment of the present invention will be described in detail below with reference to the drawings. The ultraviolet wavelength conversion element in the first embodiment of the present invention aims to calculate the wavelength of incident ultraviolet light from intensity ratio information of two or more visible light beams having different wavelengths.

[0013] The configuration of a wavelength conversion element in this embodiment is shown in Fig. 1. As shown in the figure, this wavelength conversion element includes a light input section 11 that receives irradiation of ultraviolet light, and a light conversion section 12 that converts ultraviolet light 31 irradiated by the light input section into visible light 32. In the above configuration, the wavelength of the ultraviolet light 31 is calculated from intensity ratio information of two or more visible light beams having different wavelengths (in FIG. 1, visible light beam 32a having a first wavelength and visible light beam 32b having a second wavelength).

[0014] A phosphor material can be used as a material for forming the light conversion unit 12 to realize the above function. The phosphor material is excited by the input ultraviolet light 31, and emits visible light 32 when it returns to the ground state after a certain time. The phosphor material has a plurality of excited states that emit visible light 32 after excitation and cause radiative relaxation. Furthermore, a material is used that has a characteristic that the ratio of the probability of the phosphor material taking two specific excited states depends on the energy of the ultraviolet light 31 that causes the excitation.

[0015] As an example of such a material, the inventors conducted extensive research and found that a material in which a perovskite-type oxide composed of zirconium, an alkaline earth metal, and oxygen is doped with a rare earth element such as europium as a luminescent center can achieve this function.

[0016] Specifically, it is presumed that in the phosphor material, one-photon excitation by ultraviolet light 31 includes interband excitation and charge transfer state excitation of the rare earth element that is the luminescence center. Furthermore, it is presumed that the energy of the input ultraviolet light 31 affects the excited state.

[0017] Specifically, therefore, a phosphor material in which input ultraviolet light 31 is absorbed and excited by a substance constituting the material, and which emits visible light 32 when it returns to the ground state, and which emits different visible light 32 when excited by ultraviolet light 31 of different wavelengths, is suitable as a material for realizing this embodiment. The above is an overall description of the first embodiment of the present invention. Next, each component will be described in detail with an example.

[0018] The light input unit 11 limits the incident angle, intensity, and wavelength of the input ultraviolet light 31 in order to obtain the wavelength of the input ultraviolet light 31 with good reproducibility from the intensity ratio of the converted visible light 32. If the incident angle of the ultraviolet light 31 absorbed by the light conversion unit 12 is large, the probability of the ultraviolet light 31 being absorbed and excited by the light conversion unit 12, which has a finite size, decreases. Therefore, a problem occurs in that the wavelength cannot be obtained with good reproducibility. Similarly, in order to ensure the reproducibility of the light intensity, it is preferable that the light conversion unit 12 has a shape in which the ultraviolet light 31 is input only to a certain area so that the ultraviolet light 31 is input from a specific area of ​​the light conversion unit 12. As a specific shape of this kind, a hollow cylinder or a square pillar, i.e., a circular pipe or a square pipe, can be used. For the above purpose, the material constituting the pipe is preferably a material that does not transmit the ultraviolet light 31, such as a metal.

[0019] This embodiment only functions if most of the visible light 32 output from the light conversion unit 12 originates from ultraviolet light 31. Therefore, it is preferable that light close to the wavelength of visible light 32 is not input to the light conversion unit 12. Therefore, it is preferable that the light input unit 11 has a function of a spectral filter that blocks a specific visible light wavelength range or transmits a specific ultraviolet wavelength range.

[0020] The light conversion unit 12 includes a material that has a function of converting the wavelength of the incident ultraviolet light 31 into intensity ratio information of two or more visible light beams having different wavelengths. An example of such a material found by the inventors is a perovskite oxide composed of zirconium, an alkaline earth metal, and oxygen, doped with a rare earth element as a luminescence center.

[0021] The perovskite structure is based on close packing. This structure is characterized by its high density and durability. Figure 3 shows the arrangement of elements that make up a typical crystal lattice of the perovskite structure. A typical example of a substance with a perovskite structure is barium titanate. In general, transition metal oxides consisting of a ternary system called RMO3, such as barium titanate, often have a perovskite structure. In terms of atomic arrangement, metal R41 is located at the vertices of a simple cubic lattice, metal M42 is located at the center of the lattice, and oxygen O43 is located at the center of each face.

[0022] The arrangement of the metal R41, which is the outer frame of the crystal lattice, is stable because the crystal lattice is based on close packing as mentioned above. On the other hand, the oxygen O43 and metal M42 contained inside the structure, MO6, form an octahedron, and the balance of the ionic radii of the metal R41 and metal M42 has a large effect on the crystal structure that is realized. This balance of ionic radii is generally called the tolerance factor. Depending on the value of the tolerance factor, the orientation of the MO6 octahedron with respect to the outer frame of the lattice with the metal R41 as the vertex can easily be distorted, and the phase transition occurs to a less symmetric orthorhombic or tetragonal crystal. Due to this phase transition, transition metal oxides with a perovskite structure often have various special physical properties. A typical example of a special physical property is the manifestation of the ferroelectricity of barium titanate mentioned above. This special property is also used in oxide high-temperature superconductors, solar cells, etc.

[0023] The fluorescent material used in the first embodiment of the present invention uses an alkaline earth metal as the metal R41, zirconium as the metal M42, and further substitutes a part of the alkaline earth metal with a rare earth element as a trace impurity element. This rare earth element functions as a luminescence center, and therefore functions as a phosphor material.

[0024] Generally, calcium, strontium, barium, etc. can be used as alkaline earth metals. According to the inventors' research, among these, those using calcium or strontium were able to convert the wavelength of ultraviolet light 31 into an intensity ratio of two or more visible lights with different wavelengths. On the other hand, those using barium did not have the conversion function.

[0025] The above difference in perovskite structures in which alkaline earth metals are arranged as metal R41 lies in the presence or absence of inversion symmetry at the metal R41 site. In other words, it was found that those using calcium or strontium as metal R41 have inversion symmetry with respect to the metal M42 (i.e. zirconium) site, but have a rectangular structure without inversion symmetry with respect to the metal R41 (i.e. calcium or strontium) site. On the other hand, it was found that those using barium as metal R41 have a cubic structure with inversion symmetry with respect to both the metal M42 (i.e. zirconium) site and the metal R41 (i.e. barium) site.

[0026] It is believed that the inversion symmetry of these crystal structures acts on the unique distortion of the octahedron present inside the perovskite structure described above, producing the effect. Therefore, in the phosphor material used in the embodiment of the present invention, it is necessary that the crystal structure does not have inversion symmetry with respect to the site where the alkaline earth metal is located. Therefore, even when barium is used as the alkaline earth metal, the effect of the present invention can be realized as long as a crystal structure without inversion symmetry can be realized.

[0027] The rare earth elements added to form the luminescence center can be praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, or ytterbium, among the 15 commonly known elements called lanthanoids. These elements are characterized by having an inner 4f orbital in which electrons enter the outer orbital first and then the inner orbital, and function favorably as the luminescence center. Among these, europium is particularly preferred.

[0028] There are no particular restrictions on the amount of rare earth element substituted for the alkaline earth metal, so long as the perovskite structure is maintained and the element functions as a luminescence center. However, if the concentration is too high, a decrease in efficiency called concentration quenching is generally caused. The region in which concentration quenching occurs depends on the rare earth element, but the inventors' investigations have shown that a concentration of 2 mol% or less is particularly preferable.

[0029] The method for synthesizing the fluorescent material is not particularly limited as long as the desired element ratio and crystal structure can be realized, but among these, the complex polymerization method, which has high reproducibility of the element ratio, is particularly preferable.

[0030] The complex polymerization method is a material synthesis method that generally follows the following procedure. First, a metal salt is dissolved in a solution of glycols, generally ethylene glycol or propylene glycol, containing an excess of oxycarboxylic acid such as citric acid, to form a metal oxycarboxylic acid complex. Next, this solution system is heated at a temperature of about 120 to 150°C to promote a deesterification reaction between the carboxyl group of the oxycarboxylic acid and the hydroxyl group of the glycol, to generate a polyester polymer gel. This polymer gel can be thermally decomposed at high temperature to generate metal oxide powder. The feature of this method is that the distribution of metal ions is kept almost constant during the process. Due to the above features, the element ratio and crystal structure required in the embodiment of the present invention can be realized with high reproducibility.

[0031] The fluorescent material thus created is in powder form, and so needs to be fixed into a specific shape in order for it to function as the light conversion section 12. The material to be used for fixing is preferably one that has sufficient transparency to visible light 32 and ultraviolet light 31 and that can maintain its shape. Examples of such materials include glass and resin materials. However, care must be taken as the transmittance may decrease, especially for ultraviolet light 31 with a short wavelength.

[0032] (Second embodiment) Next, a second embodiment of the present invention will be described in detail with reference to the drawings. The device in the second embodiment of the present invention includes the ultraviolet wavelength conversion element according to the first embodiment, and aims to realize an ultraviolet spectrometry device with excellent wavelength resolution.

[0033] 2 shows the configuration of the ultraviolet spectrometry device in this embodiment. As shown in the figure, this ultraviolet spectrometry device includes an ultraviolet wavelength conversion element 21 according to the first embodiment, a spectroscopic unit 22 that divides the visible light 32 output from the ultraviolet wavelength conversion element 21 into wavelengths, a first photodetector 23a that measures the intensity of visible light 32a having a first wavelength among the visible light 32 divided by the spectroscopic unit 22, and a second photodetector 23b that measures the intensity of visible light 32b having a second wavelength among the visible light. Then, the output of the second photodetector 23b is divided by the output of the first photodetector 23a, and the wavelength of the input ultraviolet light 31 is calculated from the division result.

[0034] The ultraviolet wavelength conversion element 21 for realizing the above functions can be realized as described in the first embodiment.

[0035] The first photodetector 23a and the second photodetector 23b respectively detect the intensity of the visible light 32a having a first wavelength among the visible light 32 output from the ultraviolet wavelength conversion element 21, and the light intensity of the visible light 32b having a second wavelength among the visible light 32. For this purpose, a photoelectric conversion element such as a photodiode is suitable in that it can process the light intensity with high sensitivity. However, since the sensitivity of the photodetector 23 such as a photodiode generally differs depending on the wavelength, it is necessary to correct the difference in each sensitivity when calculating the light intensity ratio.

[0036] The spectroscopic unit 22 splits the visible light 32 output from the ultraviolet wavelength conversion element 21 so that the light intensity can be measured for each different wavelength. In the example of Fig. 2, a prism is used as the spectroscopic unit 22, and the visible light 32a having a first wavelength and the visible light 32b having a second wavelength are separated by changing the angle due to the difference in the refractive index. The prism is made of a transparent dielectric material such as glass or resin. There are no restrictions on the material or shape of the prism that splits the visible light 32, but it is necessary to use a material with a refractive index necessary to allow sensors at different positions to receive the difference in the split wavelengths.

[0037] When the angle of the spectroscopic section 22 is changed using a prism or the like, the photodetector 23 may have multiple pixels and simultaneously detect the light intensity from different angles. In this case, the configuration of the photodetector 23 can be simplified, but attention must be paid to restrictions due to the pixel size and non-uniform sensitivity between elements.

[0038] In the second embodiment of the present invention, the output of the second photodetector 23b is divided by the output of the first photodetector 23a, and the wavelength of the input ultraviolet ray 31 is calculated from the division result. The wavelength of the ultraviolet ray 31 can be calculated from the division result because, as described above, the light conversion unit 12 included in the ultraviolet wavelength conversion element 21 has the function of converting the wavelength of the ultraviolet ray 31 into intensity ratio information of the converted visible light 32 having a different wavelength.

[0039] The relationship between the division result and the wavelength of the ultraviolet ray 31 is specific to the phosphor material constituting the light conversion unit 12. Therefore, the relationship needs to be measured in advance before measuring the ultraviolet ray 31, the wavelength of which is unknown, using the ultraviolet spectroscopic measurement device.

[0040] Furthermore, when the ultraviolet spectrometry device is used for a long period of time, the phosphor material constituting the light conversion unit 12 may be partially deteriorated by the ultraviolet rays 31. Furthermore, the detection sensitivity of the first photodetector 23a or the second photodetector 23b may change. Therefore, it is preferable to obtain the relationship between the division result and the wavelength of the ultraviolet rays 31 again at a necessary period during the long period of use, and correct the calculation formula.

[0041] The second embodiment described above is a configuration including one each of the first photodetector 23a and the second photodetector 23b, but it is also possible to arrange multiple detectors to obtain a two-dimensional image of the object to be measured. EXAMPLES

[0042] Examples using an ultraviolet wavelength conversion element and an ultraviolet spectrometry device according to an embodiment of the present invention will be described in detail below, but the present invention is not limited to the following examples. EXAMPLES

[0043] Below, as an example of an element according to an embodiment of the present invention, a setup was carried out based on the configuration of FIG. First, the phosphor material to be used in the light conversion section 12 was prepared. Zirconyl oxychloride octahydrate (chemical formula ZrCl2O·8H2O, Fujifilm Wako Pure Chemical Industries, Ltd.), strontium carbonate (chemical formula SrCO3, Rare Metallic Co., Ltd.), and europium (III) oxide (chemical formula Eu2O3, Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out and placed in a beaker to achieve the desired molar weight ratio. After adding dilute nitric acid to dissolve, citric acid was added in an amount twice the amount of the substance of the metal ions in the target sample, and ethylene glycol was added to this, and the mixture was dissolved while rotating at 500 rpm with a magnetic stirrer.

[0044] After dissolving, the mixture was heated at 150°C, whereupon the water content decreased and the deesterification reaction proceeded to produce a polymer gel, increasing its viscosity. The resulting polymer gel was further heated to evaporate excess water. The resulting polymer gel powder was placed in an electric furnace and fired in air at 700°C for 3 hours. The fired powder was then crushed in an agate mortar, and similarly fired in air at 1000°C for 12 hours and 1200°C for 12 hours, followed by crushing in an agate mortar, was repeated alternately to finally obtain SrZrO3:Eu-doped powder.

[0045] In order to confirm the function of the above powder as an ultraviolet wavelength conversion element, it was resin-encapsulated and made into an element according to the following procedure. First, 1g each of liquid A and B of two-part liquid rubber (general electrical, potting use, product number KE-109E, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed in a resin container, and 0.1g of the prepared SrZrO3:Eu doped powder was added. This was mixed with a stirrer for 4 minutes, and then vacuum degassed, and heated at 60°C for 5 hours to harden.

[0046] The resin containing the SrZrO3:Eu doped powder obtained above was used as the light conversion part 12 to evaluate the characteristics as an ultraviolet wavelength conversion element. The wavelengths of ultraviolet light 31 input to the ultraviolet wavelength conversion element ranged from 250 nm to 350 nm in 10 nm increments, and the optical spectrum of the output visible light 32 in the wavelength range of 450 nm to 750 nm is shown in Figure 4.

[0047] From this result, it was found that the wavelength of the visible light 32 is limited to only two places, approximately 595 nm (hereinafter referred to as 32a) and approximately 615 nm (hereinafter referred to as 32b), regardless of the wavelength of the input ultraviolet light 31. Furthermore, it was found that the shorter the wavelength of the input ultraviolet light 31, i.e., the higher the energy, the higher the intensity of 32a, i.e., the visible light with high energy.

[0048] Next, the light intensities of the two obtained visible light beams 32a and 32b having different wavelengths were measured and digitized by the first photodetector 23a and the second photodetector 23b, respectively, based on the configuration of Fig. 2. Furthermore, the ratio was calculated by (output of the second photodetector 23b)÷(output of the first photodetector 23a), and plotted against the wavelength of the input ultraviolet light 31, as shown in Fig. 5.

[0049] As a result, it was found that the wavelength of the ultraviolet light 31 and the output ratio of the first photodetector 23a and the second photodetector 23b were in good agreement. Therefore, it was made clear that the configuration of Fig. 2 can realize an ultraviolet spectrometry device with excellent wavelength resolution. [Industrial Applicability]

[0050] The present invention relates to an ultraviolet wavelength conversion element having a new function, and an ultraviolet spectroscopic measuring device having excellent wavelength resolution. [Explanation of symbols]

[0051] 11 Optical input section 12 Optical conversion section 21 Ultraviolet wavelength conversion element 22 Spectroscopic section 23a First photodetector 23b Second photodetector 31 Ultraviolet Rays 32a Visible light having a first wavelength 32b Visible light having a second wavelength 41 Metal R 42 Metal M 43 Oxygen

Claims

1. an optical input section that receives ultraviolet light; a light conversion unit that converts the ultraviolet light irradiated by the light input unit into visible light, the visible light has at least two or more different wavelengths specific to the optical conversion unit, An ultraviolet wavelength conversion element, wherein the wavelength of the ultraviolet light is calculated from intensity ratio information of the converted visible light having different wavelengths.

2. 2. The ultraviolet wavelength conversion element according to claim 1, wherein the light conversion portion includes a perovskite oxide comprising zirconium, an alkaline earth metal, and oxygen, doped with a rare earth element.

3. 3. The ultraviolet wavelength conversion element according to claim 2, wherein the perovskite oxide has a crystal structure that does not have inversion symmetry with respect to the site where the alkaline earth metal is located.

4. 4. The ultraviolet wavelength conversion element according to claim 2, wherein the rare earth element is europium.

5. An ultraviolet wavelength conversion element according to any one of claims 1 to 3, A spectroscopic unit that separates the visible light output from the ultraviolet wavelength conversion element into wavelengths; a first photodetector that measures an intensity of a first wavelength of the visible light split by the spectroscopic unit; a second photodetector for measuring an intensity of a second wavelength of the visible light; An ultraviolet spectrometry device that divides the output of the second photodetector by the output of the first photodetector and calculates the wavelength of the input ultraviolet ray from the division result.

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