JP2023007710A - Light emission measuring device and light emission measuring method - Google Patents

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 The present invention relates to a luminescence measuring apparatus and a luminescence measuring method for minute luminescent materials such as phosphors.

Measurements of excitation/emission spectra and quantum efficiencies are widely used to characterize luminescent materials such as phosphors.
FIG. 1 is a schematic diagram showing the state of measurement using a square cell made of quartz.

These measurements typically measure the luminescence of a sample with an area greater than 1 mm square. Typical examples include the bottom surface of a 10 mm×10 mm quartz square cell 1 as shown in FIG. is used as a sample form, and fluorescence emission 3 obtained by irradiating this with excitation light 2 such as spectroscopic xenon light is detected by a spectrometer (not shown) for measurement.

The value of the quantum efficiency of powdered phosphors used in light-emitting devices is important, and is calculated using the measured number of photons by the following equation.

The absorptance is the ratio of photons absorbed by the sample to the photons emitted by the excitation light. Normally, the number of photons in the excitation light measured by irradiating the excitation light onto a standard white plate, etc., and the number of photons in the scattered light (reflected light) measured by irradiating the excitation light on the sample (scattered photon number) are measured. Then, it is obtained by the formula (1a).

Internal quantum efficiency is the fraction of absorbed photons converted to internal emission. Normally, the number of photons in the excitation light measured by irradiating the excitation light onto a standard white plate, etc., and the number of photons in the scattered light measured by irradiating the excitation light onto the sample (the number of scattered photons) are measured, and the formula The absorptance is determined by (1a), the number of photons of fluorescence emitted by the sample is measured, and the internal quantum efficiency is determined by equation (1b). In calculating the number of scattered photons, it is necessary to divide the scattered light intensity by the diffuse reflectance of the standard white sample.

External quantum efficiency is the fraction of photons in the excitation light that are converted to emitted light. The absorptance is determined by the formula (1a), the internal quantum efficiency is determined by the formula (1b), and the external quantum efficiency is determined by the product of the absorptivity and the internal quantum efficiency by the formula (1c).

A method using an integrating sphere (hereinafter referred to as an integrating sphere method. See, for example, Non-Patent Document 1) is generally used for measuring quantum efficiency. Get and calculate. A method for measuring internal quantum efficiency is standardized using this method (ISO20351/JIS R1697).
FIG. 2 is a schematic diagram showing a spectroscopic measurement device that implements the integrating sphere method.
FIG. 3 shows exemplary emission and scattering spectra.

Using the spectrometer shown in FIG. 2, the internal quantum efficiency is calculated as follows.
(1) A standard diffusion white plate (not shown) is placed on the bottom surface of the integrating sphere 8, and excitation light 9 from an excitation light irradiation unit 7 equipped with a xenon lamp 5 and a spectroscope 6 is applied to the standard diffusion white plate. Thereby, the spectrum of the excitation light 9 homogenized within the integrating sphere 8 is measured by spectroscopic means having an optical fiber 14 and a multichannel photodetector 13 .
(2) By placing a phosphor sample 12 on the bottom surface of the integrating sphere 8 and irradiating the phosphor sample 12 with the excitation light 9, a part of the excitation light 9 is reflected and a part of the excitation light 9 is emitted. It emits fluorescence 11 that is absorbed by the body sample 12 and wavelength-converted.
(3) The spectrum of the mixed light of the reflected excitation light (scattered light 10) and wavelength-converted fluorescence 11 homogenized within the integrating sphere 8 is measured by spectroscopic means.
(4) Using the measured number of photons, calculate the internal quantum efficiency with equation (1b).

Quantum efficiency is a good index for knowing how much efficiency a light-emitting material has in the research and development stage compared to conventional products, or how much it can be improved in the future. In addition, at the stage of practical use such as white LED applications, it is often used for determining specifications for commercial transactions of light-emitting materials and for quality control in each manufacturing process. Especially in the latter case, the quantum efficiency measurements must be very precise. It goes without saying that the measurement accuracy of the emission spectrum is the most important factor for the accuracy of the quantum efficiency, but a particularly large uncertainty factor is the energy calibration accuracy over a wide wavelength range.

In a luminescent material such as a phosphor, the wavelength of excitation light to which energy is input and the wavelength of fluorescent light to be output are greatly different. In the case of a white LED, excitation at a wavelength of 405 nm or 450 nm is often wavelength-converted into fluorescence in a wide wavelength range from 500 to 800 nm. Generally used optical systems using integrating spheres and spectrophotometers use a combination of many optical components, so calibrating the energy over a wide wavelength range as described above requires caution, and the installation conditions Variations and changes over time are also likely sources of uncertainty in measurement accuracy.

FIG. 4 is a schematic diagram showing a spectrometer that implements another integrating sphere method.

A light distribution spectrometer as shown in FIG. 4 is used to measure the quantum efficiency with higher precision to solve the above problems (established in ISO23946). According to FIG. 4, the 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, and the excitation optical axis 22 and the phosphor sample 20 emit light. Light emission is measured by a multi-channel spectrometer 18 via an optical fiber 17 for light reception while changing the angle formed by the light receiving axis 23 of emitted light. By rotating 24 the phosphor sample 20 around the excitation optical axis 22 and changing 21 the angle formed by the excitation optical axis 22 and the light receiving axis 23, the distribution of luminescence depending on the emission angle is measured. By integrating this over the entire space, it is a method of measuring the amount of radiant light in the entire space. As a result, 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 the quantum efficiency can be obtained.

On the other hand, the development of phosphors in recent years has become more sophisticated, and a method of developing new substances by evaluating a single microscopic crystal (single particle) contained in synthesized powder has been put to practical use. (See, for example, Non-Patent Document 2). In this case as well, it is necessary to evaluate the optical properties of the crystal. It was difficult to perform the evaluation with high accuracy.

Toshiaki Okubo, Yasuo Nakagawa, Journal of the Illuminating Engineering Institute of Japan No.95 Complete No.8A (2011) p431 Naoto Hirosaki et al., Chem. Mater. 2014, 26, 4280-4288

In view of the above, an object of the present invention is to provide a luminescence measuring apparatus and a luminescence measuring method capable of evaluating the optical properties of even minute single particles.

A luminescence measurement apparatus according to the present invention includes an excitation light irradiation unit for irradiating excitation light, a test sample holding unit for holding a test sample irradiated with the excitation light, and a light receiving unit for receiving luminescence from the test sample. and 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 test of the light receiving unit The distance between the end on the sample side and the surface of the test sample held by the test sample holding part is 0 mm or more and 10 mm or less, thereby solving the above problem.
A distance between an end of the excitation light irradiation section on the test sample side and the surface of the test sample held by the test sample holding section may be 0 mm or more and 5 mm or less.
A distance between an end portion of the light receiving portion on the test sample side and the surface of the test sample held by the test sample holding portion may be 0 mm or more and 5 mm or less.
The test sample may be particles 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 to 200 times the maximum diameter of the test sample. , 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 0.1 to 200 times the maximum diameter of the test sample, and good.
The test sample holding section may have a recess for holding the test sample.
The test sample holding section other than the recess may be black to absorb the excitation light, and the excitation light irradiation section may completely include the recess and irradiate the excitation light to the outside of the recess.
The excitation light irradiation section may include a light source and an optical fiber, and the light receiving section may include a spectroscopic detector and an optical fiber.
The diameter of each of the optical fibers on the side of the test sample may be 1 to 200 times the maximum diameter of the test sample.
Each of the optical fibers may have a tip diameter of 50 μm or more and 5 mm or less on the side of the test sample.
Each of the optical fibers may be a single-wire single fiber.
The tip of each of the optical fibers on the side of the test sample may be bundled.
A straight line (excitation optical 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 the tip of the light receiving unit on the test sample side and a straight line (light-receiving axis) connecting the center of the test sample held by the test sample holding portion.
Light-receiving unit rotation for rotating the light-receiving unit around a straight line (excitation optical 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 Further mechanisms may be provided.
Holding by rotating the test sample holding unit about a straight line (excitation optical 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 part rotation mechanism may be further provided.
A luminescence measuring method according to the present invention uses the above-described luminescence measuring apparatus, irradiates a test sample with excitation light, and measures luminescence from the test sample, thereby solving the above problems.
The test sample holding part of the luminescence measuring device has a recess for holding the test sample, the recess is filled with a white reference sample, and the test sample holding part other than the recess is black for absorbing the excitation light. and, prior to measuring the luminescence from the test sample, irradiating the excitation light to a range that completely includes the white reference sample, and measuring the reflected light from the white reference sample. good.
The test sample holding portion other than the recess reflects the excitation light in the range of 0% or more and 10% or less, and the white reference sample reflects the excitation light in the measurement wavelength range in the range of 90% or more and 100% or less. hold the test sample on the white reference sample, irradiate the excitation light in a range that completely includes the white reference sample and the test sample, reflect light from the white reference sample and the test sample, and It may further comprise simultaneously measuring luminescence from the test sample.
Measuring the reflected light is calculating the number of photons W1 of the excitation light from the reflected light, and simultaneously measuring the excitation light from the reflected light from the white reference sample and the test sample is to calculate the photon number W2 of the light emission from the test sample, and the photon number W1 and W2 of the excitation light and the photon number L of the light emission are used to calculate the absorptance, the internal It may further comprise calculating an optical property selected from the group consisting of quantum efficiency and external quantum efficiency.
Measuring the luminescence is a straight line (excitation optical axis) connecting the center of the tip of the excitation light irradiation unit of the luminescence measurement device on the side of the test sample and the center of the test sample held in the test sample holding unit. while changing the angle formed by a straight line (light receiving axis) connecting the center of the tip of the light receiving unit of the luminescence measuring device on the test sample side and the center of the test sample held by the test sample holding unit. may
Measuring the luminescence is a straight line (excitation optical axis) connecting the center of the tip of the excitation light irradiation unit of the luminescence measurement device on the side of the test sample and the center of the test sample held in the test sample holding unit. may be measured while rotating the light-receiving part around .
Measuring the luminescence is a straight line (excitation optical axis) connecting the center of the tip of the excitation light irradiation unit of the luminescence measurement device on the side of the test sample and the center of the test sample held in the test sample holding unit. may be measured while rotating the test sample holder around .

By limiting the distance between the excitation light irradiation unit and the test sample and the distance between the light receiving unit and the test sample, the luminescence measurement apparatus of the present invention can measure even a minute sample such as a single particle. Allows for optical measurements. Since the fluorescence from the test sample is emitted almost uniformly, it is inversely proportional to the square of the distance between the light receiving section and the test sample, and a similar tendency occurs between the excitation light irradiation section and the test sample. This enables optical measurements, especially quantum efficiency measurements, even on particles as small as a single particle.

Schematic diagram showing the state of measurement using a quartz square cell Schematic diagram showing a spectrophotometer that implements the integrating sphere method Diagram showing exemplary emission and scattering spectra Schematic diagram showing a spectrometer that implements another integrating sphere method Schematic diagram showing the luminescence measuring device of the present invention Schematic diagram showing an enlarged test sample holder Schematic diagram showing part of another luminescence measuring device of the present invention A diagram showing an exemplary configuration of the data analysis unit Schematic diagram showing the luminescence measuring device used in Example 1 Figure showing the excitation and emission spectra of the microparticles of Example 1 A diagram showing the light-receiving distance dependence (A) and the excitation distance dependence (B) of the luminescence intensity from microparticles. Schematic diagram showing the test sample holding part of Example 2 Schematic diagram showing part of the luminescence measuring device used in Example 2 A diagram showing the scattering and emission spectra of the microparticles of Example 2 FIG. 4 is a diagram showing the orientation distribution of the luminescence intensity of the fine particles of Example 2.

The present invention will be described in detail below with reference to the drawings.
FIG. 5 is a schematic diagram showing the luminescence measuring device of the present invention.

A luminescence measurement apparatus 500 of the present invention includes an excitation light irradiation unit 510 for irradiating excitation light, a test sample holding unit 520 for holding a test sample S to which the excitation light is irradiated, and light emitted from the test sample S. and a light receiving portion 530 for receiving light.

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

By measuring in close proximity in this way, it is possible to accurately measure the emission spectrum of even a very small test sample S in particular. Such a minute test sample S may preferably be particles having a maximum diameter in the range of 0.1 μm or more and 100 μm or less. Within this range, the test sample can be irradiated with the excitation light, and the amount of light required for the measurement can be obtained, so the measurement can be performed with high accuracy.

The distance D1 is preferably 0 mm or more and 5 mm or less. As a result, the amount of excitation light with which the test sample S is irradiated can be increased. The distance D2 is preferably greater than or equal to 0 mm and less than or equal to 5 mm. Thereby, the luminescence from the test sample S can be efficiently taken in, and the amount of light can be increased. Although the distances D1 and D2 may be 0 mm, they may be larger than 0 mm in consideration of the operation of various rotating mechanisms, which will be described later, from the viewpoint of ease of handling between various components.

The distances D1 and D2 are preferably in the range of 0.1 to 200 times the maximum diameter of the test sample S. As a result, the amount of excitation light irradiated onto the test sample S can be increased, and the amount of light emitted from the test sample S can be increased, so that the test sample S having a maximum diameter of 50 μm or less can be measured with high accuracy. .

The excitation light irradiation unit 510 preferably includes a light source 511 and an optical fiber 512 optically coupled to the light source 511, guides the excitation light from the light source 511 to the optical fiber 512, The test sample S is irradiated from the

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 is a mercury lamp, a deuterium lamp, a xenon lamp, or a halogen A lamp selected from a group consisting of lamps and a spectroscope for dispersing light from the lamp may be provided. This allows the excitation light to have a single wavelength.

The light receiving section 530 preferably includes an optical fiber 531 that guides light emitted from the test sample S, and a photodetector 532 that is optically coupled to the optical fiber 531 . The photodetector 532 is not particularly limited as long as it can receive light emitted from the test sample S and obtain a wavelength spectrum, but for example, a multichannel spectroscope can be employed.

As the optical fibers 512 and 531, commonly known optical fibers having a core and a clad can be adopted, and those that guide the wavelength of excitation light and those that guide the wavelength of emitted light can be appropriately used.

In particular, when performing luminescence measurement of a very small test sample S, the diameter of the tip of the optical fibers 512 and 531 on the test sample S side is preferably in the range of 50 μm or more and 5 mm or less. As a result, the tips of the optical fibers 512 and 321 can be brought closer to the test sample S, and accurate measurement can be performed.

The tip diameters of the optical fibers 512 and 531 are more preferably in the range of 50 μm or more and 1 mm or less. As a result, it is possible to accurately irradiate a minute test sample S (for example, particles having a maximum diameter of 100 μm or less) with the excitation light, and collect the emitted light with high accuracy. The diameter of the tips of the optical fibers 512, 531 is still more preferably in the range of 100 μm to 500 μm. Smaller fiber diameters can reduce interference.

The diameters of the tips of the optical fibers 512 and 531 are preferably in the range of 1 to 200 times the maximum diameter of the test sample S. As a result, highly accurate luminescence measurement can be performed even for a very small test sample S.

Each of the optical fibers 512, 531 may be a solid single fiber. In the optical measurement of a relatively large test sample S, a bundle fiber that bundles optical fibers is often used to increase the amount of light. Optical fibers are suitable. The excitation light emitted from the optical fiber spreads while being applied to the test sample S, but the use of a single-wire type single fiber not only increases the uniformity but also facilitates handling of the luminescence measuring apparatus.

The ends of the optical fibers 512 and 531 on the side of the test sample S may be bundled. By bundling, it is possible to irradiate and receive excitation light with one component, and handling such as position adjustment of the excitation light irradiation unit 510, the test sample holding unit 520, and the light receiving unit 530 at the time of measurement is improved.

The test sample holding part 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 test sample holder.

FIG. 6 shows a test sample holder 600 with recesses 610 . By providing the concave portion 610, it becomes easier to set the white reference sample 620 and the test sample S when calculating the number of photons. The shape and size of the recess 610 can be set in consideration of the amount and size of the test sample S, but when handling a test sample of 100 μm or less, the area of the recess 610 is set to 1 square in order to improve the measurement accuracy. mm or less is suitable, and about 0.01 square mm is more preferable.

The shape of the concave portion may be circular, rectangular, or the like for ease of machining, but is not particularly limited. If more precise machining such as ion etching is employed, the degree of freedom in shape will also increase.

FIG. 6 shows that the white reference sample 620 is filled in the concave portion 610 of the test sample holding part 600, and the test sample S is held thereon. The test sample holding part 600 is preferably black so that the part other than the concave part 610 absorbs the excitation light. In this case, the test sample holding part 600 other than the concave portion preferably reflects the excitation light in a range of 0% or more and 10% or less. This allows accurate measurement. Examples of such materials include carbon materials and materials whose surfaces are alumite-blackened. More preferably, it should be made of a material whose reflectance is in the range of 0% or more and 5% or less.

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 unit 510 preferably emits the excitation light over a sufficiently wide range including the recess 610 to the outside of the recess 610. (indicated by the dashed-dotted line in FIG. 6) is irradiated. Since the outside of the recess 610 is black with low reflectance, the excitation light emits reflected light only from the sample (the white reference sample 620 or the white reference sample 620 and the test sample S) placed in the recess 610 . As a result, the reflected light from only the sample can be detected, so the measurement can be performed with high accuracy.

The white reference sample 620 preferably reflects between 90% and 100% of the excitation light in the measurement wavelength range. This allows accurate measurement. Such materials include barium sulfate, Teflon (registered trademark), and the like. These materials have a diffuse reflectance of about 96% to 99%.

By using the black test sample holding part 600 shown in FIG. 6, the entire area including the black region beyond the concave portion 610 can be uniformly irradiated without narrowing down the excitation light to be smaller than the minute test sample S. . As a result, the measurement area is always limited to the upper surface area of the concave portion 610, so compared to the case where the excitation light is narrowed down, the uncertainty of the optical measurement with respect to the positional error can be reduced. can be measured.

In addition, since the excitation light is not narrowed down to be smaller than the minute sample S to be tested, there is no need to use a laser light source and a lens that have a limited wavelength. As a result, the above-described lamp and spectroscope, which do not require consideration of the influence of polarized light, can be used and an arbitrary excitation wavelength can be set, which is highly versatile and advantageous.

FIG. 7 is a schematic diagram showing part of another luminescence measuring device of the present invention.

In the luminescence measuring apparatus of the present invention, the center of the tip of the excitation light irradiation unit (only the optical fiber 512 is shown for simplicity) on the side of the test sample S and the center of the test sample S held in the test sample holding unit 520 are measured. , the center of the tip of the light receiving unit (here, only the optical fiber 531 is shown for simplicity) on the test sample S side and the center of the test sample S held by the test sample holding unit 520 may be provided with an angle variable mechanism 710 that changes the angle formed with a straight line (light-receiving axis) connecting . Thereby, the distribution of reflected light or emitted light from the test sample S can be measured. In particular, using the black test sample holder 600 shown in FIG. 6 increases the certainty of the measurement position accuracy.

The luminescence measuring apparatus of the present invention may include a light receiving section rotating mechanism 720 that rotates the light receiving section around the excitation optical axis. Thereby, the distribution of reflected light from the test sample S around the excitation optical axis can be measured. In particular, using the black test sample holder 600 shown in FIG. 6 increases the certainty of the measurement position accuracy.

The luminescence measuring apparatus of the present invention may include a holder rotation mechanism 730 that rotates the test sample holder 520 around the excitation optical axis. Since the light emission characteristics in directions other than the direction of the excitation optical axis are averaged by the holder rotating mechanism 730, average light emission can be measured for samples having different light emission characteristics. Examples of such samples include flat crystals and acicular crystals. In particular, if the black test sample holder 600 shown in FIG. 6 is used, the uncertainty of the amount of irradiation light to the test sample S can be ignored.

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

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

The data analysis unit 540 essentially includes a photon number calculation unit 541 and an optical property calculation unit 542, but may further include a data input unit 543 and a data output unit 544 as shown in FIG.

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

The photon number calculation unit 541 receives emission spectrum data from the data input unit 543 and calculates the number of photons. For example, a case of calculating the internal quantum efficiency of a test sample S using a test sample holding part 600 in which a recess 610 is filled with a white reference sample 620 as shown in FIG. 6 will be described.

The photon number calculator 541 calculates the number of photons (intensity) W1 of the excitation light reflected from the white reference sample 620, and then calculates the number of photons W2 of the excitation light when the test sample S is held on the white reference sample 620. Then, the number of photons L of light emitted at a wavelength different from that of the excitation light when the test sample S is held on the white reference sample 620 is calculated.

The optical property calculator 542 uses the number of photons calculated by the photon number calculator 541 to calculate the internal quantum efficiency E as the optical property. Specifically, using the photon number A (=W1-W2) of the excitation light absorbed by the test sample S and the photon number L, E=L/A is used to calculate the internal quantum efficiency. In this way, by adopting the test sample holder 600 shown in FIG. 6, the number of photons of the excitation light absorbed by the test sample S can be accurately obtained, so optical measurement can be performed with high accuracy.

In addition, when wavelength spectrum data having various dependencies is acquired, the optical characteristic calculator 542 can obtain an integrated value over the entire space, so optical measurement can be performed with high accuracy.

The optical property calculator 542 may use W1, W2 and L to calculate the absorptivity and the external quantum efficiency according to the following equations.
Absorption rate = (W1-W2)/W1
External quantum efficiency = L/W1 = absorption rate x internal quantum efficiency

The optical characteristics such as the internal quantum efficiency calculated in this way may be sent to the data output unit 544 and displayed on the external display unit 810 or output by a printer or the like.

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), and the like.

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

The optical measurement method of the present invention uses the luminescence measuring apparatus 500 of the present invention, irradiates the test sample S with excitation light, and measures the luminescence from the test sample S. Since the luminescence measuring apparatus of the present invention is used, the luminescence of phosphors, which are particularly fine particles, can be measured with high accuracy, and an excitation luminescence spectrum can be obtained.

Hereinafter, an optical measurement method using the test sample holder 600 described with reference to FIG. 6 will be described. When measuring the intensity (number of photons) per area of excitation light in the present invention, as shown in FIG. The part 600 is made black to absorb the excitation light, and by irradiating the excitation light to the range outside the white reference sample 620 placed in the recess 610, the reflected light from the white reference sample 620 may be measured. Since the excitation light is irradiated widely beyond the concave portion 610, the test sample is irradiated with relatively uniform light among the excitation light, and it can be said that the deviation is small.

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 to the outside of the concave portion 610, the excitation light can be applied to the entire surface of the sample, and reflected light from the entire surface of the sample 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, a Teflon (registered trademark) compact, or the like can be used. These materials have a diffuse reflectance of about 96-99%. Such a measurement of the reflected light of the white reference sample 620 may be performed prior to the measurement of the luminescence of the test sample S.

Based on the common sense of optical measurement for powder samples so far, the idea is to narrow down the excitation light to a small test sample such as a single particle and irradiate it. led to the opposite idea of irradiating a wider area than the tiny test sample. Furthermore, the inventors of the present application adopt a black test sample holding part having a recess and irradiate the excitation light widely to the outside beyond the recess, so that the measurement area can always be limited to the area of the recess. It was found that more reliable and highly accurate measurement is possible than when the light is narrowed down.

Following (1) measuring the reflected light of the white reference sample 620 (calculating the number of photons), (2) holding the test sample S on the white reference sample 620, Excitation light is applied to a completely enclosing range, and the reflected light from the white reference sample 620 and the test sample S and the emission from the test sample are simultaneously measured.

Here, by making the outside of the concave portion 610 black, the light effective for excitation can be irradiated only to the inside of the concave portion 610. Therefore, by measuring the reflected light from the white reference sample 620 in step (1), , 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, part of the excitation light is absorbed by the test sample S, and the rest is It 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 fluorescent substance of the test sample S, and is emitted outside the sample.

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

Next, the internal quantum efficiency E may be calculated from the photon numbers W1 and W2 of the excitation light and the photon number L of the light emission using the following equation.
A = W1 - W2
E = L/A
Here, A is the number of photons of the excitation light absorbed by the test sample S. In this manner, since the number of photons of the excitation light absorbed by the test sample S can be accurately obtained, accurate optical measurement can be performed.

Of course, W1, W2, and L may be used to calculate the absorptance and the external quantum efficiency from the following equations.
Absorption rate = (W1-W2)/W1
External quantum efficiency = L/W1 = absorption rate x internal quantum efficiency

In the measurement of the quantum efficiency described above, depending on the form and crystal type of the sample, there is a possibility that there are directions in which light is easily reflected and directions in which light is easily emitted, so it is desirable to obtain an integrated value over the entire space.

When measuring luminescence, a straight line (excitation optical axis) connecting the center of the tip of the test sample side of the excitation light irradiation unit of the luminescence measurement device and the center of the test sample held in the test sample holding unit, and the light receiving unit of the luminescence measurement device. Measurement may be performed while changing the angle between the straight line (light receiving axis) connecting the center of the tip of the test sample side and the center of the test sample held by the test sample holding part. Thus, the distribution in the longitudinal direction can be averaged by integrating the intensity in the longitudinal direction of the spherical surface. By applying this method to the method of measuring the quantum efficiency in the two steps (1) and (2) described above, the quantum efficiency using the light distribution spectrometry method can be measured with high accuracy.

When measuring luminescence, the light receiving unit is rotated around a straight line (excitation optical axis) that connects the center of the tip of the excitation light irradiation unit of the luminescence measurement device on the side of the test sample and the center of the test sample held in the test sample holding unit. You can measure while As a result, the distribution in the latitudinal direction can be averaged by integrating the intensity in the latitudinal direction. By applying this method to the method of measuring the quantum efficiency in the two steps (1) and (2) described above, the quantum efficiency using the light distribution spectrometry method can be measured with high accuracy.

When measuring luminescence, the test sample is held around a straight line (excitation optical axis) that connects the center of the tip of the excitation light irradiation unit of the luminescence measuring device on the test sample side and the center of the test sample held in the test sample holding unit. You may measure while rotating a part. Thereby, the distribution in the latitudinal direction can be averaged. By applying this method to the method of measuring the quantum efficiency in the two steps (1) and (2) described above, the quantum efficiency using the light distribution spectrometry method can be measured with high accuracy.

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

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

The luminescence measurement apparatus shown in FIG. 9 includes an excitation light irradiation unit equipped with an optical fiber 26 and a xenon lamp (output 150 W, not shown), a test sample holding unit consisting of a glass rod, an optical fiber 25 and a spectroscope (Otsuka an electronic, multi-channel spectrometer (MCPD2480 type), not shown). A quartz bundle optical fiber was used as the optical fiber. As a test sample, fine particles of a phosphor having a maximum diameter of 15 μm (a phosphor produced by the same procedure as in Example 2 described in WO2010/110457) were adhered to the tip of a glass rod with a resin. Fluorescence measurement was performed by changing the light receiving distance (distance D2 in FIG. 5) between the optical fiber 25 and the sample and the excitation distance (distance D1 in FIG. 5) between the optical fiber 26 and the sample. The results are shown in FIGS. 10 and 11. FIG.

10 is a diagram showing excitation and emission spectra of microparticles of Example 1. FIG.

FIG. 10 shows the excitation/emission spectra of microparticles when the excitation distance is 3 mm and the light reception distance is 1 mm. Conventional measurement methods measure the fluorescence from powder, which is a collection of many particles, so sufficient signal intensity can be obtained even when observed from a distance of 1 to several cm. Although it was impossible, good excitation and emission spectra were obtained by observation at a distance of 1 cm or less, as shown in FIG.

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

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

As shown in FIG. 11, by integrating the observation distance (light receiving distance) and excitation distance dependence of light intensity with an exposure time of 1 second and exposure times of 4 times, good excitation and emission can be obtained in about 30 minutes even with an excitation wavelength interval of 2 nm. A spectrum was obtained. From this, it was shown that shortening the observation distance and/or the excitation distance is effective for efficient and highly accurate spectrum measurement. According to FIG. 10, since the fluorescence emitted from the test sample (microparticle) is almost uniformly dispersed, it is considered that the intensity increased in inverse proportion to the square of the distance from the light-receiving optical fiber 25 . Such tendency is the same for the excitation optical fiber and the test sample, and can be said to be inversely proportional to the square of the distance.

Xenon lamps with powers of 100 W to 450 W are commonly used in such measurements. Even if the output of the lamp is tripled, if the distance from the light-receiving optical fiber is tripled, the signal becomes less than 1/3, which is undesirable because the sensitivity is lowered. For this reason, the distance between the light receiving fiber and the test sample (corresponding to the distance D2 in FIG. 5) is desirably 10 mm or less. Such tendency is the same for the distance between the excitation optical fiber and the test sample (distance D1 in FIG. 5). For this reason, it is desirable that the distance between the optical fiber for excitation and the test sample is 10 mm or less. Although there is no particular lower limit, it may be 0 mm or more.

[Example 2]
In Example 2, the test sample holder shown in FIG. 12 was used, and the luminescence measurement apparatus shown in FIG. 13 was used to measure the emission spectrum of a minute test sample.

FIG. 12 is a schematic diagram showing a test sample holder of Example 2. FIG.

The test sample holding part of Example 2 has a surface alumite blackened, has a cylindrical structure with a diameter of about 3 mm and a length of about 20 mm, and the tip part (the left part in this figure has a diameter of 0.5 mm A thin cylindrical shape (described below) was provided with a recess of a circular hole with a diameter of 0.1 mm or less. The area of the recess was 0.0079 square mm.

Barium sulfate powder as a white reference sample 29 (FIG. 13) was filled into the concave portion of the test sample holding part, and the same phosphor microparticles as in Example 1 as the test sample 30 (FIG. 13) were appropriately placed thereon. , was used as a sample for measurement.

FIG. 12 shows a test sample holding part having a circular recess with a diameter of 0.1 mm (100 μm). bottom.

FIG. 13 is a schematic diagram showing part of the luminescence measuring apparatus used in Example 2. FIG.

The luminescence measuring apparatus of FIG. 13 is the same as the light distribution spectrometer described with reference to FIG. 12). The distance between the optical fiber 31 and the test sample 30 (corresponding to the distance D1) was 1 mm, and the distance between the optical fiber 32 and the test sample 30 (corresponding to the 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). As in Example 1, a xenon lamp (output 150 W) and a multichannel spectrometer were used.

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

The quantum efficiency of test sample 30 was measured as follows.
(1) Reflected light from the white reference sample 29 was measured.
Specifically, the excitation light emitted from the excitation optical fiber 31 spreads and irradiates a range that completely includes the white reference sample 29 , and the reflected light from the white reference sample 29 is 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, the reflected light of the white reference sample 29 was measured while moving the test sample holder 28 along the circumference 34 . In this way, the light distribution spectrometry of the excitation light in the range covering the hemisphere on the test sample holder 28 was performed for the white reference sample 29 .

(2) Hold the test sample 30 on the white reference sample 29, irradiate the excitation light to the range completely including the white reference sample 29 and the test sample 30, and reflect the reflected light (scattered light) from the white reference sample 29 and the test sample 30 light) and luminescence from the test sample were measured simultaneously. Here too, the light receiving optical fiber 32 was measured while moving on the circumference 33 . Subsequently, measurement was performed while moving the test sample holder 28 along the circumference 34 . In this manner, light distribution spectrometry of scattered light and fluorescence in a range covering the hemisphere on the test sample holding portion 28 was performed for the white reference sample 29 and the test sample 30 .

Next, the orientation distribution thus obtained was subjected to spherical volume fraction (same as the method specified in ISO23946), and the scattered emission spectrum and internal quantum efficiency were calculated.

14 is a diagram showing the scattering/luminescence spectrum of the microparticles of Example 2. FIG.

FIG. 14 shows scattering and light emission when the test sample holder having a circular hole with a diameter of 100 μm shown in FIG. 12 is used, the excitation distance and the light receiving distance are 1 mm, and the angle formed by the excitation optical axis and the light receiving axis is 45 degrees. Spectra are shown. As shown in FIG. 10, even with fine particles having a maximum diameter of 15 μm, sufficient signal intensity for achieving quantum efficiency was obtained, demonstrating the effectiveness of the device and method of the present invention.

15 is a diagram showing the orientation distribution of emission intensity of the fine particles of Example 2. FIG.

FIG. 15 shows the orientation distribution when the test sample holder having a circular hole with a diameter of 100 μm shown in FIG. is shown. According to FIG. 15, similar to the measurement of the powder sample, a distribution close to uniform light distribution was obtained, but some points deviating from the smooth curve were also observed. This is thought to be due to the non-spherical crystal shape of the microparticles, but accurate measurement is possible by dividing the entire hemisphere into spherical volumes.

Next, Table 1 shows the results of optical measurements obtained using test sample holders having recesses of various sizes.

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

On the other hand, when the diameter of the circular hole was 20 μm, the number of excitation light photons: the number of scattered photons: the number of fluorescence photons was 158:97:49. In this case, the number of absorbed photons was 61, and an internal quantum efficiency of about 80% was derived.

Furthermore, when the diameter of the circular hole is 15 μm, which is approximately equal to the particle size of the sample, the number of excitation light photons: number of scattered photons: number of fluorescence photons was 82:22:49. In this case, the number of absorbed photons was 60, and an internal quantum efficiency of about 82% was derived. The absorptance and external quantum efficiency at this time were derived to be 73% and 60%, respectively.

On the other hand, the absorptance, internal quantum efficiency and external quantum efficiency of the same sample measured by powder measurement were 80%, 65% and 81%, respectively. Although the results of powder measurement and microparticle (single particle) measurement do not necessarily match, it was found that optical measurement is possible even from 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. can be determined to have been obtained.

As described above, in this apparatus, the light emitted from the optical fiber 31 for excitation light spreads slightly and a part of the light is irradiated onto the white reference sample 29 . Therefore, the uncertainty with respect to the positional error of the circular hole portion (recess) is small. In addition, the uncertainty of the amount of irradiation light when the phosphor, which is the test sample 30, is rotated can also be ignored. As a general method, it can be said that this method is superior to the case where a test sample is excited by condensing a laser beam or the like with a lens or the like. A remarkable effect is seen especially when measuring a non-spherical sample. The certainty of the measurement position accuracy is high even compared to the case where the test sample is fixed and the light receiving optical fiber 32 is rotated for measurement. In addition, since the xenon light is dispersed and used, there are many advantages such as the ability to arbitrarily set the excitation wavelength and the need to consider the influence of polarized light.

INDUSTRIAL APPLICABILITY The present invention can be used for a luminescence measuring device and an optical measuring method that can be suitably used for evaluating luminescent materials such as phosphors, and in particular enables measurement of minute particles.

500 luminescence measuring device 510 excitation light irradiation section 511 light source 512, 531 optical fiber 520 test sample holding section 530 light receiving section 532 photodetector 540 data analysis section 541 photon number calculation section 542 optical characteristic calculation section 543 data input section 544 data output section 600 test sample holder 610 recess 620 white reference sample 710 variable angle mechanism 720 light receiving unit rotation mechanism 730 holder rotation mechanism 810 display unit S test sample

Claims (22)

an excitation light irradiation unit that irradiates excitation light;
a test sample holder for holding a test sample irradiated with the excitation light;
a light receiving unit that receives light emitted 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,
The luminescence measurement apparatus according to claim 1, wherein a distance between an end portion of the light-receiving section on the test sample side and a surface of the test sample held by the test sample holding section is 0 mm or more and 10 mm or less. 2. The luminescence measuring apparatus according to claim 1, wherein a distance between an end portion of said excitation light irradiating section on the side of said test sample and a surface of said test sample held by said test sample holding section is 0 mm or more and 5 mm or less. 3. The luminescence measuring apparatus according to claim 1, wherein a distance between an end portion of said light receiving portion on the side of said test sample and a surface of said test sample held by said test sample holding portion is 0 mm or more and 5 mm or less. The luminescence measuring apparatus according to any one of claims 1 to 3, wherein said test sample is particles having a maximum diameter in the range of 0.1 µm to 100 µm. 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 to 200 times the maximum diameter of the test sample. ,
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 0.1 times or more and 200 times or less of the maximum diameter of the test sample. Item 5. The luminescence measuring device according to any one of Items 1 to 4. The test sample holding part has a recess for holding the test sample,
The luminescence measuring device according to any one of claims 1 to 5. The test sample holding portion other than the recess is black to absorb the excitation light,
7. The luminescence measurement apparatus according to claim 6, wherein said excitation light irradiation unit completely includes said recess and irradiates said excitation light to the outside of said recess. The excitation light irradiation unit includes a light source and an optical fiber,
The luminescence measurement device according to any one of claims 1 to 7, wherein said light receiving unit comprises a spectroscopic detector and an optical fiber. 9. The luminescence measurement apparatus according to claim 8, wherein the diameter of each of said optical fibers on the side of said test sample is 1 to 200 times the maximum diameter of said test sample. 10. The luminescence measuring apparatus according to claim 8, wherein the tip of each of said optical fibers on the side of said test sample has a diameter of 50 [mu]m or more and 5 mm or less. The luminescence measuring device according to any one of claims 8 to 10, wherein each of said optical fibers is a single-wire type single fiber. The luminescence measuring apparatus according to any one of claims 8 to 10, wherein the tip of each of said optical fibers on the side of said test sample is bundled. A straight line (excitation optical 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 the tip of the light receiving unit on the test sample side The light emission according to any one of claims 1 to 12, further comprising an angle variable mechanism that changes an angle formed by a straight line (light receiving axis) connecting the center of the test sample held by the test sample holding unit and the center of the test sample. measuring device. Light-receiving unit rotation for rotating the light-receiving unit around a straight line (excitation optical 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 measuring device according to any one of claims 1 to 13, further comprising a mechanism. Holding by rotating the test sample holding unit about a straight line (excitation optical 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 device according to any one of claims 1 to 14, further comprising a part rotation mechanism. A luminescence measuring method comprising irradiating a test sample with excitation light using the luminescence measuring device according to any one of claims 1 to 15 and measuring luminescence from the test sample. The test sample holding unit of the luminescence measuring device includes a recess for holding the test sample,
The recess is filled with a white reference sample,
The test sample holding portion other than the recess is black to absorb the excitation light,
Prior to measuring luminescence from the test sample,
17. The method of claim 16, further comprising illuminating the excitation light in an area that completely contains the white reference sample and measuring reflected light from the white reference sample. The test sample holding portion other than the recess reflects the excitation light in a range of 0% or more and 10% or less,
The white reference sample reflects the excitation light in the measurement wavelength range in a range of 90% or more and 100% or less,
holding the test sample on the white reference sample, irradiating the excitation light in a range completely including the white reference sample and the test sample, and reflecting light from the white reference sample and the test sample and the test sample 18. The method of claim 17, further comprising simultaneously measuring emissions from. Measuring the reflected light is to calculate the number of photons W1 of the excitation light from the reflected light,
The simultaneous measurement 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 L of photons emitted from the test sample,
Further comprising calculating an optical characteristic selected from the group consisting of absorptance, 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 emitted light. Item 19. The method of Item 18. Measuring the luminescence is a straight line (excitation optical axis) connecting the center of the tip of the excitation light irradiation unit of the luminescence measurement device on the side of the test sample and the center of the test sample held in the test sample holding unit. while changing the angle formed by a straight line (light receiving axis) connecting the center of the tip of the light receiving unit of the luminescence measuring device on the test sample side and the center of the test sample held by the test sample holding unit. , the method according to any one of claims 16-19. Measuring the luminescence is a straight line (excitation optical axis) connecting the center of the tip of the excitation light irradiation unit of the luminescence measurement device on the side of the test sample and the center of the test sample held in the test sample holding unit. 21. The method according to any one of claims 16 to 20, wherein the measurement is performed while rotating the light receiving unit about . Measuring the luminescence is a straight line (excitation optical axis) connecting the center of the tip of the excitation light irradiation unit of the luminescence measurement device on the side of the test sample and the center of the test sample held in the test sample holding unit. 22. The method according to any one of claims 16 to 21, wherein the measurement is performed while rotating the test sample holder around the .

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