Luminescence measurement device and luminescence measurement method

Abstract

To provide a light emission measuring device and a light emission measuring method that can evaluate optical characteristics of even a fine single particle.SOLUTION: A light emission measuring device comprises an exciting light irradiation part which emits exciting light, a test sample holding part which holds a test sample irradiated with the exciting light, and a light reception part which receives light emitted by the test sample, wherein the distance between a test sample-side end part of the exciting light irradiation part and a surface of the test sample held at the test sample holding part is 0 to 10 mm, and the distance between a test sample-side end part of the light reception part and the surface of the test sample held at the test sample holding part is 0 to 10 mm.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a luminescence measurement apparatus and a luminescence measurement method for a minute luminescent material such as a phosphor.

Background Art

[0002] In the evaluation of the characteristics of a luminescent material such as a phosphor, measurement of excitation-emission spectra and quantum efficiency is widely used. FIG. 1 is a schematic diagram showing a state of measurement using a quartz right-angle cell.

[0003] In these measurements, generally, luminescence of a sample having an area larger than 1 square mm is measured. Typically, as shown in FIG. 1, the bottom surface of a 10 mm × 10 mm quartz right-angle cell 1, the side surface of a 10 mm × 30 mm quartz cell, a circular indentation with a diameter of 10 mm filled with phosphor powder 4, etc. are used as sample forms, and fluorescence emission 3 obtained by irradiating this with excitation light 2 such as xenon light dispersed by a spectroscope (not shown) is detected by a spectroscope to perform measurement.

[0004] The value of the quantum efficiency of the powdery phosphor used for a light-emitting device is important and is calculated by the following formula using the measured value of the number of photons.

[0005]

Equation

[0006] The absorption rate is the ratio of the photons absorbed by the sample among the photons emitted by the excitation light. Usually, the number of photons of the excitation light measured by irradiating the excitation light on a standard white plate or the like and the number of photons of scattered light (reflected light) measured by irradiating the excitation light on the sample are measured, and it is obtained by Equation (1a).

[0007] The internal quantum efficiency is the ratio of the photons converted to internal emission among the absorbed photons. Usually, the number of photons of the excitation light measured by irradiating the excitation light onto a standard white plate or the like, and the number of photons of the scattered light (scattered photon number) measured by irradiating the excitation light onto the sample are measured, the absorption rate is obtained by Equation (1a), and further the number of photons of the fluorescence emitted by the sample is measured, and the internal quantum efficiency is obtained by Equation (1b). Note that in calculating the scattered photon number, it is necessary to divide the scattered light intensity by the diffuse reflectance of the standard white sample.

[0008] The external quantum efficiency is the ratio of the photons of the excitation light converted to emission. The absorption rate is obtained by Equation (1a), the internal quantum efficiency is obtained by Equation (1b), and the external quantum efficiency is obtained by the product of the absorption rate and the internal quantum efficiency according to Equation (1c).

[0009] A method using an integrating sphere for measuring the quantum efficiency (hereinafter referred to as the integrating sphere method; see, for example, Non-Patent Document 1) is common, and using the apparatus shown in FIG. 2, a spectrum as shown in FIG. 3 is acquired and calculated. The measuring method of the internal quantum efficiency has been standardized using this method (ISO20351 / JIS R1697). FIG. 2 is a schematic diagram showing a spectroscopic measuring apparatus for carrying out the integrating sphere method. FIG. 3 is a diagram showing an exemplary emission / scattering spectrum.

[0010] The internal quantum efficiency is calculated as follows using the spectroscopic measuring apparatus shown in FIG. 2. (1) A standard diffuse white plate (not shown) is installed on the bottom surface of the integrating sphere 8, and the excitation light 9 from the excitation light irradiation unit 7 equipped with the xenon lamp 5 and the spectroscope 6 is irradiated onto the standard diffuse white plate, and the spectrum of the excitation light 9 homogenized in the integrating sphere 8 is measured by the spectroscopic means equipped with the optical fiber 14 and the multi-channel photodetector 13. (2) The phosphor sample 12 is installed on the bottom surface of the integrating sphere 8, and by irradiating the excitation light 9 onto the phosphor sample 12, a part of the excitation light 9 is reflected, and a part of the excitation light 9 is absorbed by the phosphor sample 12 and emits fluorescence 11 whose wavelength is converted. (3) The spectral means measures the spectrum in which the mixed light of the reflected excitation light (scattered light 10) and the wavelength-converted fluorescence 11 is homogenized within the integrating sphere 8. (4) Using the measured value of the photon number, the internal quantum efficiency is calculated by Equation (1b).

[0011] The quantum efficiency is a good indicator for knowing how efficient a luminescent material is compared to conventional products at the research and development stage, or how much potential for improvement there is in the future. Also, at the practical application stage such as for white LEDs, it is often used for determining the specifications of commercial transactions of luminescent materials and for quality control in each manufacturing process. Especially in the latter case, very high accuracy is required for the measured value of the quantum efficiency. Needless to say, the measurement accuracy of the emission spectrum is most important for the accuracy of the quantum efficiency, but a particularly large factor of uncertainty is the energy calibration accuracy over a wide wavelength range.

[0012] For luminescent materials such as phosphors, the wavelength of the excitation light that inputs energy and the wavelength of the fluorescence that outputs energy are significantly different. In the case of white LEDs, it is often excited at wavelengths of 405 nm or 450 nm and wavelength-converted to fluorescence in a wide wavelength range from 500 to 800 nm. In an optical system using a generally used integrating sphere or a spectrophotometer, etc., since many optical components are combined and used, energy calibration in the above-mentioned wide wavelength range requires caution, and changes in the installation situation and time-dependent changes are also likely to cause uncertainty in the measurement accuracy.

[0013] FIG. 4 is a schematic diagram showing a spectroscopic measurement apparatus for implementing another integrating sphere method.

[0014] For more accurate measurement of quantum efficiency to solve the above problems, a distribution photometry measurement device as shown in Fig. 4 is used (specified in ISO23946). According to Fig. 4, excitation light from the spectral xenon light 16 through the excitation optical fiber 15 hits the phosphor sample 20 held in the test sample holding part 19. While changing the angle formed by the excitation light axis 22 and the light receiving axis 23 along which the phosphor sample 20 emits light, the light emission is measured by the multi-channel spectroscope 18 through the light receiving optical fiber 17. By rotating the phosphor sample 20 24 around the excitation light axis 22 and changing 21 the angle formed by the excitation light axis 22 and the light receiving axis 23, the light emission distribution according to the emission angle is measured. By integrating this over the entire space, it is a method of measuring the total amount of emitted light in the entire space. Thereby, the total amount of excitation light received by the sample, the total amount of light absorbed by the sample, and the total amount of fluorescence emitted by the sample can be calculated, and thereby the quantum efficiency can be obtained.

[0015] On the other hand, in recent years, the development of phosphors has become more advanced, and a method of developing new substances by evaluating minute single crystals (single particles) contained in the synthesized powder has been put into practical use (see, for example, Non-Patent Document 2). Also in this case, it is required to evaluate the optical properties of the crystals. However, since the general particle size of a single particle is as fine as 10 to 30 μm, it has been difficult to accurately evaluate fine particles by the measurement methods developed for powders as in the past.

Prior Art Documents

Non-Patent Documents

[0016]

Non-Patent Document 1

Non-Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0017] As described above, an object of the present invention is to provide a luminescence measurement device and a luminescence measurement method capable of evaluating the optical properties of even minute single particles.

Means for Solving the Problems

[0018] The luminescence measurement device according to the present invention includes an excitation light irradiation unit that irradiates excitation light, a test sample holding unit for holding a test sample to be irradiated with the excitation light, and a light receiving unit that receives luminescence from the test sample. The distance between the end of the excitation light irradiation unit on the test sample side and the surface of the test sample held by the test sample holding unit is 0 mm or more and 10 mm or less, and the distance between the end of the light receiving unit on the test sample side and the surface of the test sample held by the test sample holding unit is 0 mm or more and 10 mm or less, thereby solving the above problems. The distance between the end of the excitation light irradiation unit on the test sample side and the surface of the test sample held by the test sample holding unit may be 0 mm or more and 5 mm or less. The distance between the end of the light receiving unit on the test sample side and the surface of the test sample held by the test sample holding unit may be 0 mm or more and 5 mm or less. The test sample may be a particle having a maximum diameter in the range of 0.1 μm or more and 100 μm or less. The distance between the end of the excitation light irradiation unit on the test sample side and the surface of the test sample held by the test sample holding unit is 0.1 times or more and 200 times or less the maximum diameter of the test sample, and the distance between the end of the light receiving unit on the test sample side and the surface of the test sample held by the test sample holding unit may be 0.1 times or more and 200 times or less the maximum diameter of the test sample. The test sample holding unit may have a recess for holding the test sample. The test sample holding unit other than the recess is black and absorbs the excitation light. The excitation light irradiation unit completely includes the recess and may irradiate the excitation light up to the outside of the recess. The excitation light irradiation unit may include a light source and an optical fiber, and the light receiving unit may include a spectroscopic detector and an optical fiber. The diameter of each of the optical fibers on the test sample side may be 1 time or more and 200 times or less the maximum diameter of the test sample. The diameter of the tip of each of the optical fibers on the test sample side may be 50 μm or more and 5 mm or less. Each of the optical fibers may be a single-strand single fiber. The tips of the optical fibers on the test sample side may be bundled. An angle variable mechanism may be further provided for changing the angle formed by a straight line (excitation light axis) connecting the center of the tip of the excitation light irradiation unit on the test sample side and the center of the test sample held by the test sample holding unit, and a straight line (light reception axis) connecting the center of the tip of the light reception unit on the test sample side and the center of the test sample held by the test sample holding unit. A light reception unit rotation mechanism may be further provided for rotating the light reception unit about a straight line (excitation light axis) connecting the center of the tip of the excitation light irradiation unit on the test sample side and the center of the test sample held by the test sample holding unit. A holding unit rotation mechanism may be further provided for rotating the test sample holding unit about a straight line (excitation light axis) connecting the center of the tip of the excitation light irradiation unit on the test sample side and the center of the test sample held by the test sample holding unit. The luminescence measurement method according to the present invention includes irradiating a test sample with excitation light and measuring the luminescence from the test sample using the above-described luminescence measurement device, thereby solving the above problems. The test sample holding unit of the luminescence measurement device includes a concave portion for holding the test sample, the concave portion is filled with a white reference sample, and the test sample holding unit other than the concave portion is black and absorbs the excitation light. Prior to measuring the luminescence from the test sample, it may further include irradiating the excitation light over a range completely covering the white reference sample and measuring the reflected light from the white reference sample. The test sample holding part other than the concave part reflects the excitation light in the range of 0% or more and 10% or less, the white reference sample reflects the excitation light in the measurement wavelength range in the range of 90% or more and 100% or less, holds the test sample on the white reference sample, irradiates the excitation light on the range completely including the white reference sample and the test sample, and may further include simultaneously measuring the reflected light from the white reference sample and the test sample and the light emission from the test sample. Measuring the reflected light is to calculate the number of photons W1 of the excitation light from the reflected light, and the simultaneous measurement is to calculate the number of photons W2 of the excitation light from the reflected light from the white reference sample and the test sample, and calculate the number of photons L of the light emission from the test sample, and may further include calculating the optical properties selected from the group consisting of absorption rate, internal quantum efficiency, and external quantum efficiency using the number of photons W1 and W2 of the excitation light and the number of photons L of the light emission. Measuring the light emission may be performed while changing the angle formed by a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation part of the light emission measuring device and the center of the test sample held by the test sample holding part, and a straight line (light receiving axis) connecting the center of the tip on the test sample side of the light receiving part of the light emission measuring device and the center of the test sample held by the test sample holding part. Measuring the light emission may be performed while rotating the light receiving part around a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation part of the light emission measuring device and the center of the test sample held by the test sample holding part. Measuring the light emission may be performed while rotating the test sample holding part around a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation part of the light emission measuring device and the center of the test sample held by the test sample holding part.

Advantages of the Invention

[0019] The luminescence measurement device of the present invention enables optical measurement even for a minute sample such as a single particle by restricting the distance between the excitation light irradiation unit and the test sample and the distance between the light receiving unit and the test sample. Since the fluorescence from the test sample is emitted almost uniformly, it is inversely proportional to approximately the square of the distance between the light receiving unit and the test sample, and a similar tendency occurs between the excitation light irradiation unit and the test sample. Thereby, even a minute particle such as a single particle enables optical measurement, particularly quantum efficiency measurement.

Brief Description of the Drawings

[0020]

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Figure 15

Best Mode for Carrying Out the Invention

[0021] Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 5 is a schematic diagram showing the luminescence measurement apparatus of the present invention.

[0022] The luminescence measurement apparatus 500 of the present invention includes an excitation light irradiation unit 510 that irradiates excitation light, a test sample holding unit 520 that holds a test sample S to be irradiated with the excitation light, and a light receiving unit 530 that receives the luminescence from the test sample S.

[0023] Here, in the luminescence measurement apparatus 500 of the present invention, the distance D1 between the end on the test sample S side of the excitation light irradiation unit 510 and the surface of the test sample S held by the test sample holding unit 520 is maintained at 0 mm or more and 10 mm or less, and the distance D2 between the end on the test sample S side of the light receiving unit 530 and the surface of the test sample S held by the test sample holding unit 520 is maintained at 0 mm or more and 10 mm or less.

[0024] In this way, by measuring in close proximity, it is possible to accurately measure the luminescence spectrum, especially for even a minute test sample S. Such a minute test sample S may preferably be a particle having a maximum diameter in the range of 0.1 μm or more and 100 μm or less. Within this range, the excitation light can be irradiated onto the test sample, and since the amount of light required for measurement can be obtained, accurate measurement can be performed.

[0025] The distance D1 is preferably 0 mm or more and 5 mm or less. Thereby, the amount of excitation light irradiated onto the test sample S can be increased. The distance D2 is preferably 0 mm or more and 5 mm or less. Thereby, the luminescence from the test sample S can be efficiently captured, and the amount of light can be increased. Note that the distances D1 and D2 may be 0 mm, but considering the operations of various rotation mechanisms described later, they may be larger than 0 mm for better handling between various components.

[0026] The distances D1 and D2 are preferably in the range of 0.1 times or more and 200 times or less the maximum diameter of the test sample S. Thereby, the amount of excitation light irradiated to the test sample S can be increased, and the amount of light emitted from the test sample S can be increased. Therefore, it is possible to perform highly accurate measurement particularly for a test sample S having a maximum diameter of 50 μm or less.

[0027] The excitation light irradiation unit 510 preferably includes a light source 511 and an optical fiber 512 optically coupled to the light source 511. The excitation light from the light source 511 is guided to the optical fiber 512 and irradiated onto the test sample S from the tip of the optical fiber 512.

[0028] Here, the light source 511 is not particularly limited as long as it can irradiate the test sample S and excite the test sample S. Preferably, the light source 511 may include a lamp selected from the group consisting of a mercury lamp, a deuterium lamp, a xenon lamp, and a halogen lamp, and a spectroscope for spectroscopically analyzing the light from the lamp. Thereby, the excitation light can have a single wavelength.

[0029] The light receiving unit 530 preferably includes an optical fiber 531 that guides the light emitted from the test sample S and a photodetector 532 optically coupled to the optical fiber 531. The photodetector 532 is not particularly limited as long as it can receive the light emitted from the test sample S and acquire a wavelength spectrum. Exemplarily, a multi-channel spectroscope can be employed.

[0030] As the optical fibers 512 and 531, optical fibers having a generally known core and cladding can be employed, and those for guiding the wavelength of the excitation light and those for guiding the wavelength of the emitted light can be appropriately employed.

[0031] In particular, when measuring the light emission of a minute test sample S, the diameters of the tips of the optical fibers 512 and 531 on the test sample S side are preferably in the range of 50 μm or more and 5 mm or less. Thereby, the tips of the optical fibers 512 and 321 can be brought close to the test sample S, and highly accurate measurement can be performed.

[0032] The diameter of the tips of the optical fibers 512 and 531 is more preferably in the range of 50 μm or more and 1 mm or less. Thereby, the excitation light can be accurately irradiated onto a minute test sample S (for example, a particle having a maximum diameter of 100 μm or less), and the emitted light can be accurately collected. The diameter of the tips of the optical fibers 512 and 531 is even more preferably in the range of 100 μm or more and 500 μm or less. When the diameter of the optical fiber is small, the interference can be reduced.

[0033] The diameter of the tips of the optical fibers 512 and 531 is preferably in the range of 1 to 200 times the maximum diameter of the test sample S. Thereby, the luminescence measurement can be performed with high precision even for a minute test sample S.

[0034] The optical fibers 512 and 531 may each be a single-line single fiber. In optical measurements for a relatively large test sample S, a bundle fiber in which optical fibers are bundled is often used to increase the amount of light. However, for a minute test sample S, a single-line optical fiber with a thin diameter is suitable. The excitation light irradiated from the optical fiber irradiates the test sample S while spreading. By using a single-line single fiber, not only the uniformity is increased, but also the handling of the luminescence measurement device becomes better.

[0035] The ends of the optical fibers 512 and 531 on the test sample S side may be in a bundled form. By bundling, it becomes possible to irradiate and receive the excitation light with a single component, and the handling such as the position adjustment between the excitation light irradiation unit 510, the test sample holding unit 520, and the light receiving unit 530 during measurement becomes better.

[0036] The test sample holding unit 520 is not particularly limited as long as it can hold the test sample S as shown in FIG. 5, but preferably has a concave portion. FIG. 6 is a schematic diagram showing an enlarged view of the test sample holding unit.

[0037] FIG. 6 shows a test sample holding part 600 having a recess 610. By providing the recess 610, when calculating the number of photons, it becomes easier to place the white reference sample 620 and the test sample S. The shape and size of the recess 610 can be set in consideration of the amount and size of the test sample S. However, when handling a test sample of 100 μm or less, in order to improve the measurement accuracy, the area of the recess 610 is preferably 1 square mm or less, and more preferably about 0.01 square mm.

[0038] As the shape of the recess, it may be circular, rectangular, etc. for ease of machining, but there is no particular limitation. If more precise machining such as ion etching is adopted, the degree of freedom in shape also increases.

[0039] FIG. 6 shows a state where the recess 610 of the test sample holding part 600 is filled with the white reference sample 620 and the test sample S is held thereon. The test sample holding part 600 is preferably black, with the part other than the recess 610 absorbing the excitation light. In this case, the test sample holding part 600 other than the recess preferably reflects the excitation light in the range of 0% or more and 10% or less. Thereby, accurate measurement can be performed. Examples of such materials include carbon materials and materials with the surface anodized and blackened. More preferably, it is made of a material with a reflectance in the range of 0% or more and 5% or less.

[0040] When measuring the reflection of the white reference sample 620, or the white reference sample 620 and the test sample S, the excitation light irradiation part 510 preferably irradiates the excitation light (indicated by the dashed-dotted line in FIG. 6) over a sufficiently wide range including the recess 610 and extending outside the recess 610. Since the outside of the recess 610 is black with a low reflectance, the excitation light emits only the reflected light from the sample placed in the recess 610 (the white reference sample 620, or the white reference sample 620 and the test sample S). Thereby, the reflected light from only the sample can be detected, and accurate measurement can be performed.

[0041] The white reference sample 620 preferably reflects 90% or more and 100% or less of the excitation light in the measurement wavelength range. Thereby, accurate measurement can be performed. Examples of such materials include barium sulfate and Teflon (registered trademark). These materials have a diffuse reflectance of about 96% to 99%.

[0042] By using the black test sample holding part 600 shown in FIG. 6, the entire area including the black area beyond the concave part 610 can be uniformly irradiated without narrowing the excitation light to be smaller than the minute test sample S. Thereby, since the measurement area is always limited to the upper surface area of the concave part 610, the uncertainty of the optical measurement with respect to the position error can be reduced compared to the case where the excitation light is narrowed, and in particular, accurate measurement can be performed in the calculation of the number of photons.

[0043] In addition, since it is not necessary to narrow the excitation light to be smaller than the minute test sample S, it is not necessary to use a laser light source and a lens with wavelength limitations. As a result, since the above-described lamp and spectroscope that do not require consideration of the influence of polarization are adopted and an arbitrary excitation wavelength can be set, it has high versatility and is advantageous.

[0044] FIG. 7 is a schematic diagram showing a part of another luminescence measurement apparatus of the present invention.

[0045] The luminescence measurement apparatus of the present invention includes a straight line (excitation light axis) connecting the center of the tip on the test sample S side of the excitation light irradiation part (here, only the optical fiber 512 is shown for simplicity) and the center of the test sample S held by the test sample holding part 520, and a straight line (light receiving axis) connecting the center of the tip on the test sample S side of the light receiving part (here, only the optical fiber 531 is shown for simplicity) and the center of the test sample S held by the test sample holding part 520. An angle variable mechanism 710 for changing the angle formed therebetween may be provided. Thereby, the distribution according to the direction of the reflected light or luminescence from the test sample S can be measured. In particular, when the black test sample holding part 600 shown in FIG. 6 is used, the certainty of the measurement position accuracy is high.

[0046] The luminescence measurement device of the present invention may include a light-receiving unit rotation mechanism 720 that rotates the light-receiving unit around the excitation light axis. Thereby, the distribution due to the reflected light around the excitation light axis from the test sample S can be measured. In particular, if the black test sample holding unit 600 shown in FIG. 6 is used, the certainty of the measurement position accuracy is high.

[0047] The luminescence measurement device of the present invention may include a holding unit rotation mechanism 730 that rotates the test sample holding unit 520 around the excitation light axis. Since the holding unit rotation mechanism 730 averages the luminescence characteristics in directions other than the excitation light axis direction, it is possible to measure the average luminescence for samples with different luminescence characteristics. Examples of such samples include crystals having a flat or needle-like shape. In particular, if the black test sample holding unit 600 shown in FIG. 6 is used, the uncertainty of the amount of irradiation light to the test sample S can be ignored.

[0048] Returning to FIG. 5 again, the luminescence measurement device 500 of the present invention may include a data analysis unit 540. The data analysis unit 540 acquires the data of the luminescence spectrum acquired by the light-receiving unit 530 and calculates optical characteristics such as the quantum efficiency.

[0049] FIG. 8 is a diagram showing an exemplary configuration of the data analysis unit.

[0050] The data analysis unit 540 essentially includes a photon number calculation unit 541 and an optical characteristic calculation unit 542. However, as shown in FIG. 8, it may further include a data input unit 543 and a data output unit 544.

[0051] The data input unit 543 receives and stores the data of the luminescence spectrum acquired by the light-receiving unit 530. At this time, the data of the luminescence spectrum may have information such as the angular dependence between the excitation light axis and the light-receiving axis, and the distribution around the excitation light axis.

[0052] The photon number calculation unit 541 receives the data of the luminescence spectrum from the data input unit 543 and calculates the photon number. For example, the case of calculating the internal quantum efficiency of the test sample S using the test sample holding unit 600 in which the white reference sample 620 is filled in the concave portion 610 as shown in FIG. 6 will be described.

[0053] The photon number calculation unit 541 calculates the photon number (intensity) W1 of the excitation light reflected from the white reference sample 620. Next, it calculates the photon number W2 of the excitation light with the test sample S held on the white reference sample 620, and calculates the photon number L of the light emission with a wavelength different from that of the excitation light with the test sample S held on the white reference sample 620.

[0054] The optical property calculation unit 542 calculates the internal quantum efficiency E as an optical property using the photon numbers calculated by the photon number calculation unit 541. Specifically, using the photon number A (=W1 - W2) of the excitation light absorbed by the test sample S and the photon number L, the internal quantum efficiency is calculated using E = L / A. In this way, if the test sample holding unit 600 shown in FIG. 6 is adopted, the photon number of the excitation light absorbed by the test sample S can be accurately obtained, so that optical measurement can be performed with high accuracy.

[0055] Also, when acquiring data of a wavelength spectrum having various dependencies, since the optical property calculation unit 542 can obtain an integral value over the entire space, optical measurement can be performed with high accuracy.

[0056] The optical property calculation unit 542 may calculate the absorption rate and the external quantum efficiency by the following formula using W1, W2, and L. Absorption rate = (W1 - W2) / W1 External quantum efficiency = L / W1 = Absorption rate × Internal quantum efficiency

[0057] The optical properties such as the internal quantum efficiency calculated in this way may be sent to the data output unit 544 and displayed on an external display unit 810, or output by a printing device or the like.

[0058] The photon number calculation unit 541 and the optical property calculation unit 542 of the data analysis unit 540 are realized by, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc.

[0059] Next, a method for measuring the luminescence of a test sample using the luminescence measurement apparatus of the present invention described with reference to FIG. 5 of the present invention will be described.

[0060] The optical measurement method of the present invention is measured by irradiating a test sample S with excitation light and measuring the luminescence from the test sample S using the luminescence measurement apparatus 500 of the present invention. By using the luminescence measurement apparatus of the present invention, it is possible to accurately measure the luminescence of a phosphor, which is a particularly minute particle, and to obtain an excitation luminescence spectrum.

[0061] Hereinafter, an optical measurement method using the test sample holding unit 600 described with reference to FIG. 6 will be described. When measuring the intensity (number of photons) per area of the excitation light in the present invention, as shown in FIG. 6, the test sample holding unit has a recess 610 for installing the sample, and the test sample holding unit 600 other than the recess 610 is black for absorbing the excitation light. It is preferable to measure the reflected light from the white reference sample 620 by irradiating the excitation light up to the range outside the white reference sample 620 installed in the recess 610. Since it is irradiated widely beyond the recess 610, it can be said that relatively uniform light among the excitation light is irradiated to the test sample and the deviation is small.

[0062] When measuring a small amount of sample, the size of the recess 610 is preferably 1 square mm or less, more preferably 0.01 square mm or less. By applying light up to the outside of the recess 610, the excitation light can be applied to the entire sample surface, and the reflected light from the entire sample surface can be measured. At this time, the reflection of the excitation light is suppressed by the black color outside the sample surface. The white reference sample 620 preferably has a higher reflectance, and barium sulfate powder, Teflon (registered trademark) molded body, or the like can be used. These materials have a diffuse reflectance of about 96 to 99%. Measurement of the reflected light of such a white reference sample 620 may be performed prior to measurement of the luminescence of the test sample S.

[0063] Based on the common sense of optical measurement for powder samples up to now, when it comes to a minute test sample such as a single particle, the idea would be to narrow down and irradiate the excitation light to be smaller than the test sample. However, the inventors of the present application came up with the reverse idea of irradiating over a wider area than the minute test sample. Furthermore, the inventors of the present application adopted a black test sample holding part provided with a recess, and by irradiating the excitation light widely up to the outside beyond the recess, the measurement area can always be limited to the area of the recess, and it was found that more reliable and highly accurate measurement becomes possible than when the excitation light is narrowly narrowed down.

[0064] (1) Subsequently to measuring the reflected light of the white reference sample 620 (calculating the number of photons), (2) hold the test sample S on the white reference sample 620, irradiate the excitation light over a range that completely includes the white reference sample 620 and the test sample S, and simultaneously measure the reflected light from the white reference sample 620 and the test sample S and the light emission from the test sample.

[0065] Here, by making the outside of the recess 610 black, the light effective for excitation can be irradiated only inside the recess 610. Thus, in the step (1), by measuring the reflected light from the white reference sample 620, the number of photons of the excitation light irradiated to the white reference sample 620 can be measured. Next, in the step (2), by irradiating the excitation light with the minute test sample S placed on the white reference sample 620, a part of the excitation light is absorbed by the test sample S, and the rest is diffusely reflected by the white reference sample 620. The excitation light absorbed by the test sample S is converted into light (light emission) having a wavelength different from that of the excitation light by the action of the phosphor of the test sample S and is emitted outside the sample.

[0066] More specifically, in the step (1), calculate the number of photons W1 of the excitation light from the reflected light of the white reference sample 620. In the step (2), calculate the number of photons W2 of the excitation light from the reflected light from the white reference sample 620 and the test sample S, and calculate the number of photons L of the light emission from the test sample S.

[0067] Next, the internal quantum efficiency E may be calculated from the number of photons W1, W2 of the excitation light and the number of photons L of the light emission using the following formula. A = W1 - W2 E = L / A Here, A is the number of photons of the excitation light absorbed by the test sample S. Thus, since the number of photons of the excitation light absorbed by the test sample S can be accurately determined, optical measurement can be performed with high precision.

[0068] Naturally, the absorption rate and the external quantum efficiency may be calculated from the following formula using W1, W2, and L. Absorption rate = (W1 - W2) / W1 External quantum efficiency = L / W1 = Absorption rate × Internal quantum efficiency

[0069] In the measurement of the above quantum efficiency, depending on the form and crystal form of the sample, there may be a direction that is more likely to be reflected or emit light depending on the orientation. Therefore, it is desirable to obtain an integrated value over the entire space.

[0070] During luminescence measurement, measurement may be performed while changing the angle between the straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit of the luminescence measurement device and the center of the test sample held by the test sample holding unit, and the straight line (light receiving axis) connecting the center of the tip on the test sample side of the light receiving unit of the luminescence measurement device and the center of the test sample held by the test sample holding unit. Thereby, by integrating the intensity in the longitude direction of the spherical surface, the distribution in the longitude direction can be averaged. By applying this method to the method of measuring the quantum efficiency in the above two steps (1) and (2), the quantum efficiency using the distribution photometry method can be accurately measured.

[0071] During luminescence measurement, measurement may be performed while rotating the light receiving unit around the straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit of the luminescence measurement device and the center of the test sample held by the test sample holding unit. Thereby, by integrating the intensity in the latitude direction, the distribution in the latitude direction can be averaged. By applying this method to the method of measuring the quantum efficiency in the above two steps (1) and (2), the quantum efficiency using the distribution photometry method can be accurately measured.

[0072] When measuring luminescence, measurement may be performed while rotating the test sample holding unit about a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit of the luminescence measurement device and the center of the test sample held by the test sample holding unit. Thereby, the distribution in the latitude direction can be averaged. By applying this method to the method of measuring the quantum efficiency in the above two steps (1) and (2), the quantum efficiency using the distribution photometry method can be accurately measured.

[0073] Note that the orientation spectroscopy measurement for the above step (1) may be omitted when the orientation spectroscopy of the white reference sample 620 is the object of the central axis.

Example

[0074] [Example 1] In Example 1, the luminescence spectrum of a minute test sample was measured using the luminescence measurement device shown in FIG. 9. FIG. 9 is a schematic diagram showing the luminescence measurement device used in Example 1.

[0075] The luminescence measurement device shown in FIG. 9 includes an excitation light irradiation unit including an optical fiber 26 and a xenon lamp (output 150 W, not shown), a test sample holding unit made of a glass rod, and a light receiving unit including an optical fiber 25 and a spectroscope (manufactured by Otsuka Electronics Co., Ltd., multi-channel spectroscope (MCPD2480 type), not shown). A quartz bundle optical fiber was used for the optical fiber. As the test sample, phosphor microparticles having a maximum diameter of 15 μm (phosphors manufactured in the same procedure as in Example 2 described in WO2010 / 110457) were adhered to the tip of the glass rod with resin. The light receiving distance between the optical fiber 25 and the sample (distance D2 in FIG. 5), and the excitation distance between the optical fiber 26 and the sample (distance D1 in FIG. 5) were changed, and fluorescence measurement was performed. The results are shown in FIGS. 10 and 11.

[0076] FIG. 10 is a diagram showing the excitation and luminescence spectra of the microparticles of Example 1.

[0077] FIG. 10 shows the excitation and emission spectra of microparticles when the excitation distance is 3 mm and the light-receiving distance is 1 mm. In the conventional measurement method, since fluorescence from a powder, which is a collection of a large number of particles, was measured, sufficient signal intensity could be obtained even when observed at a distance of 1 to several centimeters. In contrast, it was impossible with single-particle measurement. However, as shown in FIG. 10, by observing at a distance of 1 cm or less, a good excitation and emission spectrum was obtained.

[0078] When the excitation distance was 1 mm and the light-receiving distance was 5 mm, an excitation emission spectrum with a sufficient S / N ratio was obtained by integrating the exposure time of 10 seconds and the number of exposures of 4 times for each excitation wavelength. The measurement time required when the excitation wavelength interval was 10 nm was about 60 minutes even including dark current measurement and the like.

[0079] FIG. 11 is a diagram showing the light-receiving distance dependence (A) and excitation distance dependence (B) of the emission intensity from microparticles.

[0080] As shown in FIG. 11, by integrating the observation distance (light-receiving distance) and excitation distance dependence of the light intensity with an exposure time of 1 second and the number of exposures of 4 times, a good excitation and emission spectrum was obtained in about 30 minutes even when the excitation wavelength interval was 2 nm. From this, it was shown that it is effective to shorten the observation distance and / or excitation distance in order to efficiently measure a high-precision spectrum. According to FIG. 10, since the fluorescence emitted from the test sample (microparticles) is emitted almost uniformly, it is considered that it becomes stronger in inverse proportion to approximately the square of the distance from the light-receiving optical fiber 25. Such a tendency is the same with respect to the excitation optical fiber and the test sample, and it can be said that it is in inverse proportion to approximately the square of the distance.

[0081] In such measurements, a xenon lamp with an output of usually 100 W to 450 W is typically used. Even if the output of the lamp triples, if the distance to the light-receiving optical fiber triples, the signal will be reduced to 1 / 3 or less, resulting in a decrease in sensitivity, which is not preferable. From this, the distance between the light-receiving optical fiber and the test sample (corresponding to distance D2 in Fig. 5) is preferably 10 mm or less. Such a tendency is the same regarding the distance between the excitation optical fiber and the test sample (distance D1 in Fig. 5). Therefore, the distance between the excitation optical fiber and the test sample is preferably 10 mm or less. There is no particular lower limit, but it may be 0 mm or more.

[0082] [Example 2] In Example 2, the test sample holding part shown in Fig. 12 was used, and the luminescence spectrum of a minute test sample was measured using the luminescence measuring device shown in Fig. 13.

[0083] Fig. 12 is a schematic diagram showing the test sample holding part of Example 2.

[0084] The test sample holding part of Example 2 has a cylindrical structure with a diameter of approximately 3 mm and a length of approximately 20 mm, and its surface is subjected to anodizing blackening treatment. A concave part with a circular hole having a diameter of 0.1 mm or less is provided at the tip (in this figure, the left part forms a thin cylindrical shape with a diameter of 0.5 mm or less). The area of the concave part was 0.0079 square mm.

[0085] Such a concave part of the test sample holding part was filled with barium sulfate powder as the white reference sample 29 (Fig. 13), and the same phosphor fine particles as in Example 1 were appropriately placed thereon as the test sample 30 (Fig. 13) to obtain a sample for measurement.

[0086] Fig. 12 shows a test sample holding part having a concave part with a circular hole having a diameter of 0.1 mm (100 μm), but test sample holding parts having concave parts with circular holes having diameters of 20 μm and 15 μm were also prepared.

[0087] Fig. 13 is a schematic diagram showing a part of the luminescence measuring device used in Example 2.

[0088] The luminescence measurement device of FIG. 13 is the same as the distribution spectroscope described with reference to FIG. 7, and the excitation optical fiber 31 and the light receiving optical fiber 32 are arranged to face a test sample holding unit 28 (FIG. 12) that holds the test sample 30. The distance between the optical fiber 31 and the test sample 30 (corresponding to distance D1) was 1 mm, and the distance between the optical fiber 32 and the test sample 30 (corresponding to distance D2) was 1 mm. The diameter of the excitation optical fiber 31 was 150 μm (core diameter: 120 μm), and the diameter of the light receiving optical fiber 32 was 370 μm (core diameter: 230 μm). Similar to Example 1, a xenon lamp (output 150 W) and a multi-channel spectroscope were used.

[0089] The excitation optical fiber 31 is arranged above the test sample 30, and the light receiving optical fiber 32 is attached to a light receiving unit rotation mechanism (not shown) that rotates around a straight line (excitation optical axis) connecting the optical fiber 31 and the test sample 30, and measurement was performed while moving on the circumference 33. The test sample holding unit 28 was attached to a holding unit rotation mechanism (not shown) that rotates around the excitation optical axis and was movable on the circumference 34.

[0090] The quantum efficiency of the test sample 30 was measured as follows. (1) The reflected light from the white reference sample 29 was measured. Specifically, the excitation light emitted from the excitation optical fiber 31 was irradiated in a range that completely included the white reference sample 29 while spreading, and the reflected light from the white reference sample 29 was measured by the light receiving optical fiber 32. At this time, the light receiving optical fiber 32 was measured while moving on the circumference 33. Subsequently, while moving the test sample holding unit 28 along the circumference 34, the reflected light of the white reference sample 29 was measured. In this way, the distribution spectro measurement of the excitation light in the range covering the hemisphere on the test sample holding unit 28 for the white reference sample 29 was performed.

[0091] (2) The test sample 30 was held on the white reference sample 29, and the excitation light was irradiated onto the range completely covering the white reference sample 29 and the test sample 30. The reflected light (scattered light) from the white reference sample 29 and the test sample 30 and the luminescence from the test sample were measured simultaneously. Also here, the light-receiving optical fiber 32 was measured while moving on the circumference 33. Subsequently, the measurement was performed while moving the test sample holding portion 28 along the circumference 34. In this way, the angular distribution measurement of the scattered light and fluorescence in the range covering the hemisphere on the test sample holding portion 28 was performed for the white reference sample 29 and the test sample 30.

[0092] Next, the orientation distribution thus obtained was spherically integrated (the same as the method defined in ISO23946), and the scattered emission spectrum and the internal quantum efficiency were calculated.

[0093] FIG. 14 is a diagram showing the scattering and emission spectra of the fine particles in Example 2.

[0094] FIG. 14 shows the scattering and emission spectra when the test sample holding portion of the circular hole with a diameter of 100 μm shown in FIG. 12 was used, the excitation distance and the light-receiving distance were 1 mm, and the angle formed by the excitation optical axis and the light-receiving optical axis was 45 degrees. As shown in FIG. 10, even for fine particles with a maximum diameter of 15 μm, a sufficient signal intensity for obtaining the quantum efficiency was obtained, indicating that the apparatus and method of the present invention are effective.

[0095] FIG. 15 is a diagram showing the orientation distribution of the luminescence intensity of the fine particles in Example 2.

[0096] FIG. 15 shows the orientation distribution when the test sample holding portion of the circular hole with a diameter of 100 μm shown in FIG. 12 was used, the excitation distance and the light-receiving distance were 1 mm, and the light-receiving optical fiber 32 was moved on the circumference 33. According to FIG. 15, a distribution close to uniform angular distribution similar to that in the measurement of the powder sample was obtained, but points deviating from the smooth curve were also observed. This is considered to be due to the crystal shape in which the fine particles are not spherical, but accurate measurement is possible by spherically integrating the entire hemisphere.

[0097] Next, Table 1 shows the results of optical measurements obtained using test sample holders with recesses of various sizes.

[0098]

Table 1

[0099] According to Table 1, it was found that by reducing the diameter of the recess, that is, by reducing the area, it is possible to bring the intensity ratio of scattering to fluorescence closer. The ratio of the number of excitation light photons:scattered photons:fluorescent photons in the case of a diameter of 100 μm was 3945:3893:49. The ratio of the number of absorbed photons calculated from this was 52. The internal quantum efficiency in this case was derived to be approximately 94%.

[0100] On the other hand, when the diameter of the circular hole was 20 μm, the number of excitation light photons:scattered photons:fluorescent photons was 158:97:49. The number of absorbed photons in this case was 61, and an internal quantum efficiency of approximately 80% was derived.

[0101] Furthermore, when the diameter of the circular hole was 15 μm, which was approximately equal to the particle size of the sample, the number of excitation light photons:scattered photons:fluorescent photons was 82:22:49. The number of absorbed photons in this case was 60, and an internal quantum efficiency of approximately 82% was derived. The absorption rate and external quantum efficiency at this time were derived to be 73% and 60% respectively.

[0102] On the other hand, when the quantum efficiency of the same sample was measured in powder form, the absorption rate, internal quantum efficiency, and external quantum efficiency were 80%, 65%, and 81% respectively. Although the measurement results of powder measurement and those of microparticles (single particles) do not always match, it was found that optical measurement is possible even for a single particle. Focusing on the number of absorbed photons, as the area of the recess is reduced, more of the excitation light is absorbed by the microparticles. Therefore, it can be judged that especially when the area of the recess is reduced, the results match well and reliable results are obtained.

[0103] As described above, in this apparatus, the light emitted from the excitation light optical fiber 31 spreads slightly, and a part of it irradiates the white reference sample 29. For this reason, the uncertainty with respect to the position error of the circular hole portion (recess) is small. In addition, the uncertainty of the irradiation light amount when the phosphor, which is the test sample 30, is rotated can also be ignored. It can be said that it has a higher superiority compared with the case of exciting a test sample by condensing laser light or the like with a lens or the like as a general method. Particularly, a remarkable effect is seen when measuring a non-spherical sample. The reliability of the measurement position accuracy is also high compared with the case where the test sample is fixed and the light receiving optical fiber 32 is rotated for measurement. Further, since xenon light is spectroscopically used, there are many advantages such as that the excitation wavelength can be arbitrarily set and that it is not necessary to consider the influence of polarization.

Industrial Applicability

[0104] The present invention can be used for a luminescence measurement apparatus and an optical measurement method that can be suitably used for evaluating luminescent materials such as phosphors, and particularly enables measurement of minute particles.

Explanation of Signs

[0105] 500 Luminescence measurement apparatus 510 Excitation light irradiation unit 511 Light source 512, 531 Optical fiber 520 Test sample holding unit 530 Light receiving unit 532 Photodetector 540 Data analysis unit 541 Photon number calculation unit 542 Optical property calculation unit 543 Data input unit 544 Data output unit 600 Test sample holding unit 610 Recess 620 White reference sample 710 Angle variable mechanism 720 Light receiving unit rotation mechanism 730 Holding unit rotation mechanism 810 Display unit S Test sample

Claims

1. An excitation light irradiation unit that irradiates excitation light, A test sample holding unit for holding a test sample irradiated with the excitation light, A light receiving unit that receives light emitted from the test sample Comprising, The distance between the end of the excitation light irradiation unit on the test sample side and the surface of the test sample held by the test sample holding unit is 0 mm or more and 10 mm or less, The distance between the end of the light receiving unit on the test sample side and the surface of the test sample held by the test sample holding unit is 0 mm or more and 10 mm or less, The test sample holding unit has a recess for holding the test sample, The recess is filled with a white reference sample, The test sample holding unit other than the recess is black and absorbs the excitation light, The test sample is a particle and is placed on the white reference sample, a luminescence measuring device.

2. The distance between the end of the excitation light irradiation unit on the test sample side and the surface of the test sample held by the test sample holding unit is 0 mm or more and 5 mm or less. The luminescence measuring device according to Claim 1.

3. The distance between the end of the light receiving unit on the test sample side and the surface of the test sample held by the test sample holding unit is 0 mm or more and 5 mm or less. The luminescence measuring device according to Claim 1 or 2.

4. The test sample is a particle having a maximum diameter in the range of 0.1 μm or more and 100 μm or less. The luminescence measuring device according to any one of Claims 1 to 3.

5. The excitation light irradiation unit completely includes the recess and irradiates the excitation light to the outside of the recess. The luminescence measuring device according to any one of Claims 1 to 4.

6. The excitation light irradiation unit includes a light source and an optical fiber, The light receiving unit includes a spectroscopic detector and an optical fiber. The luminescence measuring device according to any one of Claims 1 to 5.

7. The diameter of each of the optical fibers on the test sample side is 1 times or more and 200 times or less the maximum diameter of the test sample. The luminescence measuring device according to Claim 6.

8. The diameter of the tip of each of the optical fibers on the test sample side is 50 μm or more and 5 mm or less. The luminescence measuring device according to Claim 6 or 7.

9. Each of the optical fibers is a single-mode single fiber. The luminescence measuring device according to any one of Claims 6 to 8.

10. The tips of each of the optical fibers on the test sample side are bundled. The luminescence measuring device according to any one of Claims 6 to 8.

11. An angle variable mechanism for changing an angle formed by a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit and the center of the test sample held by the test sample holding unit, and a straight line (light reception axis) connecting the center of the tip on the test sample side of the light reception unit and the center of the test sample held by the test sample holding unit. The luminescence measurement device according to any one of claims 1 to 10, further comprising.

12. The luminescence measurement device according to any one of claims 1 to 11, further comprising a light reception unit rotation mechanism that rotates the light reception unit about a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit and the center of the test sample held by the test sample holding unit.

13. The luminescence measurement device according to any one of claims 1 to 12, further comprising a holding unit rotation mechanism that rotates the test sample holding unit about a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit and the center of the test sample held by the test sample holding unit.

14. A luminescence measurement method, comprising irradiating a test sample with excitation light and measuring luminescence from the test sample, using the luminescence measurement device according to any one of claims 1 to 13.

15. Prior to measuring the luminescence from the test sample, The method according to claim 14, further comprising irradiating the white reference sample with the excitation light in a range that completely includes the white reference sample and measuring reflected light from the white reference sample.

16. The test sample holding unit other than the concave portion reflects the excitation light in a range of 0% or more and 10% or less, The white reference sample reflects the excitation light in a range of 90% or more and 100% or less in the measurement wavelength range, The method according to claim 15, further comprising holding the test sample on the white reference sample, irradiating the white reference sample and the test sample with the excitation light in a range that completely includes the white reference sample and the test sample, and simultaneously measuring reflected light from the white reference sample and the test sample and luminescence from the test sample.

17. Measuring the reflected light is calculating the number of photons W1 of the excitation light from the reflected light, Simultaneously measuring is calculating the number of photons W2 of the excitation light from the reflected light from the white reference sample and the test sample, and calculating the number of photons L of the luminescence from the test sample. The method according to claim 16, further comprising calculating an optical property selected from the group consisting of an absorption rate, an internal quantum efficiency, and an external quantum efficiency, using the number of photons W1 and W2 of the excitation light and the number of photons L of the emission.

18. The measuring of the emission is performed while changing an angle formed between a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit of the emission measuring apparatus and the center of the test sample held by the test sample holding unit, and a straight line (light reception axis) connecting the center of the tip on the test sample side of the light reception unit of the emission measuring apparatus and the center of the test sample held by the test sample holding unit. The method according to any one of claims 14 to 17.

19. The measuring of the emission is performed while rotating the light reception unit about a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit of the emission measuring apparatus and the center of the test sample held by the test sample holding unit. The method according to any one of claims 14 to 18.

20. The measuring of the emission is performed while rotating the test sample holding unit about a straight line (excitation light axis) connecting the center of the tip on the test sample side of the excitation light irradiation unit of the emission measuring apparatus and the center of the test sample held by the test sample holding unit. The method according to any one of claims 14 to 19.

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