Biological information measuring device

Abstract

To provide a reflection type photoelectric volume pulse wave sensor and a biological information measuring device capable of achieving both good wearing feelings and measurement accuracy by performing optimum design according to a thickness of the skin and the like in a measurement part.SOLUTION: A reflection type photoelectric volume pulse wave sensor is equipped with a planar light emission element and a planar light reception element. The light emission element and the light reception element are not opposed to each other in a vertical direction. When the shortest distance between the light emission element and the light reception element is represented as h (mm) and a thickness of the skin (epidermis and corium) of the body is represented as t (mm), and the thickness is in a range of 0.1-4 mm, the shortest distance h (mm) between at least one set of the light emission element and the light reception element satisfies a following formula (1): (t×0.7)2≤h≤(t×1.3)2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflective photoelectric volume pulse wave sensor and a biological information measuring device equipped with the same, and in particular to a reflective photoelectric volume pulse wave sensor that can achieve both a comfortable fit and measurement accuracy by performing an optimal design according to the thickness of the skin at the measurement site, etc. [Background technology]

[0002] Services that allow people to check their health conditions and receive medical care without going to the hospital are being actively considered, and photoplethysmography (PPG), which allows non-invasive acquisition of vital data (biological information), is attracting attention. PPG has traditionally been widely used as a pulse oximeter, and more recently has been adopted as an activity meter and used in systems that constantly record pulse rates. The former, pulse oximeter, uses the pulse wave to measure the difference in absorbance between red and infrared light, so high accuracy is required in detecting the pulse wave, whereas the latter, activity monitor, can tolerate relatively lower accuracy and uses green because it is less affected by positional deviation and is more convenient (see non-patent document 1).

[0003] In this specification, "vital data" refers to any biological information such as pulse wave, heart rate, electrocardiogram, blood oxygen concentration, respiratory rate, and blood pressure.

[0004] With the recent rise in health awareness, there has been a growing trend to use wearable devices to constantly collect vital signs data and use it for prevention and disease alerts. To achieve this, it is necessary to balance accuracy with comfort, and as medical data it is necessary to collect not only pulse but also pulse waves with high accuracy. At present, however, most conventional pulse oximeters use a translucent system that is placed on the fingertip.

[0005] However, this transmission method requires the sensor to be attached to an extremity such as the fingertip or base of the finger, making it unsuitable for continuous measurement. On the other hand, most activity monitors are reflective types that use green light and are usually worn on the wrist (back of the hand), but it is difficult to detect pulse waves with high accuracy at this location. High accuracy is not required if only pulse rate is to be measured.

[0006] In order to transmit light to the inside of a living body, light with a longer wavelength than red is required. Also, it is preferable to detect arteries deep inside the living body (arteries generate pulse waves), especially arterioles in the dermis.

[0007] In the case of the reflective type, the light source and the sensor are on the same plane, so in order for the light to reach the sensor, it must scatter inside the body, and only the light that returns backwards (the opposite side to the direction in which the light is emitted) can be detected. In this case, in order to reliably detect the light that has passed through the arteriole, it is necessary to place the light source and the sensor at a certain distance. However, there are individual differences and differences in skin thickness depending on the part of the body being measured, and the allowable size for attachment also differs, so there was a problem in that it was necessary to optimize the design for each measurement part.

[0008] In the case of a reflective type, it is preferable that the light source and the sensor are arranged on the same surface, and the technology described in Patent Document 1 is disclosed as a prior example. This is a combination of an organic EL element and an organic PD, and is suitable for improving adhesion and wearing comfort. Regarding the distance between the light source and the sensor, the technology disclosed in Non-Patent Document 2 states that increasing the distance increases the sensitivity. However, there is no mention of what the preferred distance is. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent Application Publication No. 2017 / 0156651 [Non-patent literature]

[0010] [Non-Patent Document 1] Maeda, Yuka et al.; Position dependence of reflection photoplethysmograph - Comparison of signal output between two adjacent points with different measurement light and location -; Life Support; Vol. 23 No. 3, 2011, 124-129 [Non-Patent Document 2] Japanese Journal of Optics Country of origin: Japan, Publication date: October 10, 2001, Volume 30, Issue 10, Pages 644-650 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in consideration of the above problems and circumstances, and its problem to be solved is to provide a reflective photoplethysmographic sensor and a biological information measuring device that can achieve both a comfortable fit and measurement accuracy by performing an optimal design according to the thickness of the skin at the measurement site, etc. [Means for solving the problem]

[0012] In the course of investigating the causes of the above problems in order to solve the above problems, the inventors discovered that by specifying the relationship between the distance between the light-emitting element and the light-receiving element and the thickness of the skin within a specific range, it is possible to provide a reflective photoplethysmographic sensor and the like that can achieve both a comfortable fit and measurement accuracy, and thus arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0013] 1. A reflective photoplethysmographic sensor having a planar light emitting element and a light receiving element, The light emitting element and the light receiving element do not face each other in the vertical direction, The shortest distance between the light-emitting element and the light-receiving element is h (mm), If the thickness of the human skin (epidermis + dermis) is t (mm) and the thickness is within the range of 0.1 to 4 mm, A reflective photoplethysmographic sensor, characterized in that the shortest distance h (mm) between at least one pair of the light-emitting element and the light-receiving element satisfies the following formula (1): Equation (1): (t×0.7) 2 ≦h≦(t×1.3) 2

[0014] 2. The reflective photoplethysmographic sensor according to claim 1, wherein the shortest distance between the light-emitting element and the light-receiving element is within a range of 2 to 25 mm.

[0015] 3. The reflective photoelectric volume pulse wave sensor according to claim 1 or 2, wherein the light-emitting element is an organic EL element.

[0016] 4. The reflective photoelectric volume pulse wave sensor according to any one of claims 1 to 3, wherein the light receiving element is an organic photodiode.

[0017] 5. A reflective photoelectric volume pulse wave sensor as described in any one of claims 1 to 4, characterized in that it comprises a plurality of the light-emitting elements, each of which is arranged on a roughly concentric circle centered on the center point of the light-receiving element.

[0018] 6. A light emitting device having a plurality of the light emitting elements, at least two of the plurality of light emitting elements emitting light of the same wavelength; 6. The reflective photoelectric volume pulse wave sensor according to any one of claims 1 to 5, wherein the plurality of light-emitting elements can emit light individually.

[0019] 7. A reflective photoelectric volume pulse wave sensor as described in claim 6, characterized in that information and data acquired based on light emitted from a light-emitting element located close to the light-receiving element and a light-emitting element located farther away from the light-emitting element among the plurality of light-emitting elements are processed.

[0020] 8. A reflective photoelectric volume pulse wave sensor as described in any one of claims 1 to 4, characterized in that it has a plurality of light receiving elements, each of which is arranged on a roughly concentric circle centered on the center point of the light emitting element.

[0021] 9. A reflective photoelectric volume pulse wave sensor as described in claim 8, characterized in that information and data obtained based on light received from a light receiving element located close to the light emitting element and a light receiving element located farther away from the light receiving element among the multiple light receiving elements are processed.

[0022] 10. There are a plurality of types of the shortest distance between the light emitting element and the light receiving element; 10. The reflective photoelectric volume pulse wave sensor according to any one of claims 1 to 9, characterized in that the light emitting element and the light receiving element having the shortest distance suitable for sensing are selected.

[0023] 11. A biological information measuring device comprising the reflective photoelectric volume pulse wave sensor according to any one of claims 1 to 10. Effect of the Invention

[0024] According to the above-mentioned aspects of the present invention, it is possible to provide a reflective photoplethysmographic sensor and a biological information measuring device that can achieve both a comfortable fit and high measurement accuracy. Although the mechanism by which the effects of the present invention are expressed or the mechanism by which the present invention works has not been clarified, it is believed that the problems associated with the present invention have been solved based on the findings described below.

[0025] When light is irradiated onto biological tissue, which is a strong scatterer, the irradiated light propagates in a hemispherical shape from the point of irradiation within the scattering body, but academic research has shown that the propagation path of the detected light is banana-shaped.

[0026] In the present invention, assuming the above-mentioned phenomenon, and through various trial-and-error experiments and studies, it has been found that when the thickness of human skin (epidermis + dermis) is within the range of 0.1 to 4 mm, and the light-emitting element and the light-receiving element are not opposed to each other in the vertical direction, i.e., are arranged so that the two elements do not overlap, and a reflective photoplethysmographic sensor is designed such that the shortest distance between the light-emitting element and the light-receiving element is within the range that satisfies formula (1), measurement variation can be suppressed and a good fit and measurement accuracy can be achieved at the same time.

[0027] As a result, it was possible to expand the number of measurement locations, while also enabling constant monitoring and increasing the flexibility of measurement locations. In addition, by making it a reflective type, it is possible to expand the measurement area and realize a device that causes less discomfort when worn. Therefore, the present invention provides a method for improving the measurement sensitivity of a reflective photoplethysmographic sensor and a method for measuring the measurement sensitivity of a reflective photoplethysmographic sensor. This contributes to suppressing variation. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic diagram for explaining the relationship between the minimum distance between the light-emitting element and the light-receiving element in a reflective photoplethysmography sensor and the thickness of the skin. [Diagram 2] FIG. 1 is a schematic diagram for explaining the arrangement of a light-emitting element and a light-receiving element that constitute a reflective photoelectric volume pulse wave sensor according to a first embodiment; [Diagram 3] FIG. 3 shows a modified example of the arrangement of FIG. 2. [Figure 4] FIG. 3 shows a modified example of the arrangement of FIG. 2. [Diagram 5] FIG. 3 shows a modified example of the arrangement of FIG. 2. [Figure 6] FIG. 3 shows a modified example of the arrangement of FIG. 2. [Figure 7] FIG. 13 is a schematic diagram for explaining the arrangement of light-emitting elements and light-receiving elements that constitute a reflective photoelectric volume pulse wave sensor according to a second embodiment. [Figure 8] FIG. 8 shows a modified example of the arrangement of FIG. 7. [Figure 9]FIG. 1 is a schematic diagram for explaining another example of a reflective photoplethysmographic sensor; [Figure 10] FIG. 1 is a diagram showing an example of the external configuration of a biological information measuring device; [Figure 11] FIG. 2 is a diagram showing an example of a functional configuration of a biological information measuring device; [Figure 12] FIG. 2 is a diagram showing an example of a functional configuration of an information processing device; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The reflective photoelectric volume pulse wave sensor of the present invention is a reflective photoelectric volume pulse wave sensor equipped with a planar light-emitting element and a light-receiving element, wherein the light-emitting element and the light-receiving element do not face each other in the vertical direction, and the shortest distance between the light-emitting element and the light-receiving element is h (mm), the thickness of human skin (epidermis + dermis) is t (mm) and the thickness is within a range of 0.1 to 4 mm, the shortest distance h (mm) between at least one pair of the light-emitting element and the light-receiving element satisfies the following formula (1): Equation (1): (t×0.7) 2 ≦h≦(t×1.3) 2 This feature is a technical feature common to or corresponding to each of the following embodiments.

[0030] As an embodiment of the present invention, it is preferable in terms of improving measurement accuracy that the shortest distance between the light emitting element and the light receiving element is within a range of 2 to 25 mm.

[0031] The light-emitting element is preferably an organic EL element, which is flexible, comfortable to wear, and capable of reducing wavelength variation and brightness variation. For the same reasons as above, it is preferable that the light receiving element is an organic photodiode.

[0032] The light-emitting element is provided in a plurality of types, and each of the light-emitting elements is arranged on a substantially concentric circle with the center point of the light-receiving element as the center, thereby improving robustness against misalignment. In particular, when an organic EL element is used as the light-emitting element, the amount of light per area can be reduced by becoming a surface light source compared to when an LED, which is a point light source, is used, so that low-temperature burns are less likely to occur.

[0033] Providing a plurality of the light-emitting elements, at least two of which emit light of the same wavelength, and being able to individually emit light from the plurality of light-emitting elements makes it possible to process data based on the light emitted from the plurality of light-emitting elements, and as a result, it is possible to calculate effective data minus noise, which is preferable in terms of improving measurement accuracy.

[0034] By processing information and data acquired based on light emitted from a light-emitting element disposed near the light-receiving element and a light-emitting element disposed farther away from the light-emitting element among the plurality of light-emitting elements, effective data from which noise has been subtracted can be calculated; This is preferable in terms of improving measurement accuracy.

[0035] Providing a plurality of the light receiving elements and arranging the light receiving elements approximately on concentric circles with the center point of the light emitting element as the center can improve robustness against misalignment.

[0036] Processing the information and data acquired based on the light received from the light receiving element located close to the light emitting element and the light receiving element located farther away from the light receiving element among the multiple light receiving elements is preferable in terms of improving measurement accuracy, since it makes it possible to calculate effective data with noise subtracted.

[0037] There are multiple types of shortest distance between the light-emitting element and the light-receiving element, and selecting the light-emitting element and the light-receiving element having the shortest distance suitable for sensing makes it possible to calculate effective data minus noise, which is preferable in terms of improving measurement accuracy.

[0038] The reflective photoplethysmographic sensor can be suitably used in various biological information measuring devices.

[0039] The present invention, its components, and embodiments for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as lower and upper limits.

[0040] 1. [Outline of the reflective photoplethysmographic sensor of the present invention] The reflective photoelectric volume pulse wave sensor of the present invention is a reflective photoelectric volume pulse wave sensor equipped with a planar light-emitting element and a light-receiving element, wherein the light-emitting element and the light-receiving element do not face each other in the vertical direction, and the shortest distance between the light-emitting element and the light-receiving element is h (mm), the thickness of human skin (epidermis + dermis) is t (mm) and the thickness is within a range of 0.1 to 4 mm, the shortest distance h (mm) between at least one pair of the light-emitting element and the light-receiving element satisfies the following formula (1): Equation (1): (t×0.7) 2 ≦h≦(t×1.3) 2

[0041] In addition, in terms of improving measurement accuracy, it is preferable that the shortest distance between the light-emitting element and the light-receiving element is within the range of 2 to 25 mm, and particularly taking into consideration the size of the device, it is preferable that the upper limit of the shortest distance is 17.5 mm or less, and most preferably 10 mm or less.

[0042] <Functions of the reflective photoplethysmography sensor> The reflective photoelectric volume pulse wave sensor of the present invention irradiates light onto the measured portion of the biological tissue using a light-emitting element such as a light-emitting diode as a light source, detects the light reflected from the measured portion of the biological tissue using a light-receiving element such as a photodiode as a light detection sensor, and measures changes in the volume pulse wave of the biological tissue based on the detected signal.

[0043] For example, light emitted from a light emitting element passes through the epidermis and reaches blood vessels deep inside the epidermis. The light that reaches the blood vessels is absorbed or reflected by the blood flowing through the blood vessels, or passes through the blood. Of this light, the light scattered by the blood vessel tissue and blood enters the photodetector. As a result, the photodetector outputs a photocurrent according to the amount of incident light. Here, the blood vessels repeatedly expand and contract with the same cycle as the heartbeat. Therefore, the amount of reflected light increases and decreases with the same cycle as the expansion and contraction of the blood vessels, so the change in the photocurrent output from the photodetector indicates the change in the volume of the blood vessels.

[0044] The reflective photoelectric volume pulse wave sensor of the present invention is a sensor for detecting the oxygen saturation of arterial blood. The hemoglobin in blood has different absorbances for red and infrared light depending on whether it is bound to oxygen or not. Therefore, by preparing multiple sets of elements with different emission and reception wavelengths, such as an element that emits and receives red light and an element that emits and receives infrared light, and measuring and analyzing the reflected light from these, oxygen saturation can be detected. The blood vessels are arteries.

[0045] It should be noted that the "volume pulse wave" is a waveform that appears when a change in pressure within a blood vessel due to pulsation causes a change in volume, and it allows the change in blood vessels to be directly grasped. Moreover, the "photoelectric volume pulse wave" is a waveform detected by utilizing the transmission or reflection of light through blood in order to detect the volume pulse wave.

[0046] <Calculation method of oxygen saturation> Generally, the reflective photoelectric volume pulse wave sensor (pulse oximeter) is used to measure the oxygen saturation in blood. A pulse oximeter irradiates a finger with light of two wavelengths in the red to near-infrared wavelength range and measures the transmittance and reflectance. Specifically, blood hemoglobin (Hb) exists in four states: oxygenated hemoglobin (O2Hb), reduced hemoglobin (HHb), methemoglobin (MetHb), and carboxyhemoglobin (COHb). MetHb and COHb are abnormal hemoglobins that increase in methemoglobinemia and carbon monoxide poisoning. Therefore, oxygen saturation is usually determined by the ratio of O2Hb to O2Hb+HHb. When red light is passed through hemoglobin (Hb), the absorbance of red light by HHb is significantly greater than that of O2Hb, and varies greatly depending on the wavelength of the red light. Also, when near-infrared light is passed through hemoglobin (Hb), the absorbance of near-infrared light by HHb is slightly lower than that of near-infrared light by O2Hb. Therefore, the ratio R of hemoglobin's red light absorbance to near-infrared light absorbance (red light absorbance / near-infrared light absorbance) changes depending on the oxygen saturation, which is the ratio of O2Hb to O2Hb+HHb in the blood.

[0047] In addition, in measurement sites such as fingers, wrists, backs of arms, chest, and abdomen, there are arterial blood, venous blood, tissues, and bones, which affect the absorbance of red light and the absorbance of near-infrared light. Among them, the part to which the volume change of the vascular volume pulse wave contributes is arterial blood. If the absorbance of the pulse wave part is AC, and the absorbance of the non-pulsatile part of arterial blood, venous blood, tissues, and bones is DC, for example, the AC component of the absorbance of red light with a wavelength of 660 nm is AC660, the DC component is DC660, and the AC component of the absorbance of near-infrared light with a wavelength of 940 nm is AC940, and the DC component is DC940, the ratio R of the absorbance of red light to the absorbance of near-infrared light (absorbance of red light / absorbance of near-infrared light) is expressed by the following formula (I).

number

[0048] The blood oxygen saturation can be calculated based on the R value calculated by the above formula (I) and a calibration curve showing the relationship between the R value and the percutaneous arterial oxygen saturation (SpO2) that has been empirically obtained in advance.

[0049] In addition, when red light and near-infrared light are usually irradiated onto the fingers, wrist (e.g., ulnar side, radial side), back of the arm, chest, and other parts of the body, and the absorbance is measured, the change in absorbance over time is measured as a waveform that reflects the pulse wave. Therefore, the AC component of the absorbance can be determined by calculating the difference between the maximum and minimum values ​​of the change in absorbance over time, and the DC component of the absorbance can be determined by calculating the average of the change in absorbance over time. In the embodiments described later, the value calculated in this manner is referred to as "AC / DC."

[0050] <Distance between the light emitting element and the light receiving element> The light-emitting element and the light-receiving element of the present invention are not opposed to each other in the vertical direction, and the shortest distance between the light-emitting element and the light-receiving element is h (mm), the thickness of the human skin (epidermis + dermis) is t (mm), and the thickness is within the range of 0.1 to 4 mm, the shortest distance h (mm) between at least one pair of the light-emitting element and the light-receiving element satisfies the following formula (1). Equation (1): (t×0.7) 2 ≦h≦(t×1.3) 2

[0051] The above formula (1) means that the shortest distance between the light-emitting element and the light-receiving element is within the range of ±30% squared of the skin thickness. In the above formula (1), h and t represent only numerical values.

[0052] "The light-emitting element and the light-receiving element are not opposed to each other (in the vertical direction)" means that the light-emitting element and the light-receiving element are not arranged so as to overlap and face each other in the vertical direction, but are arranged side by side in the planar direction.

[0053] FIG. 1 is a schematic diagram for explaining the relationship between the shortest distance between a light emitting element and a light receiving element and the thickness of the skin. In the present invention, the "thickness of human skin" refers to the total thickness of the epidermis and dermis of the human body, and the thickness of the skin is within the range of 0.1 to 4 mm. In addition, in the present invention, the "shortest distance between the light-emitting element and the light-receiving element" refers to the shortest distance h (mm) from the side edge of the light-receiving element 70 on the light-emitting element 80 side to the side edge of the light-emitting element 80 on the light-receiving element 70 side, as shown in Figure 1, in a side cross-sectional view.

[0054] Figure 1 shows an example in which multiple light-emitting elements 80, 90, and 90B are provided for one light-receiving element 70, and the shortest distance h (mm) between the light-receiving element 70 and the light-emitting element 80 is within a range that satisfies the above formula (1). It is to be noted that the shortest distance between the light receiving element 70 and the light emitting element 90 and the shortest distance between the light receiving element 70 and the light emitting element 90B are not within the range that satisfies the above formula (1). Therefore, as will be described later, biometric information (vital data) obtained based on light emitted from light-emitting elements 90, 90B that do not satisfy the shortest distance range defined in the present invention contains noise, and valid vital data can be calculated by subtracting the noisy vital data from the vital data obtained based on light emitted from light-emitting element 80 that satisfies the shortest distance range.

[0055] 1.1 [Arrangement of light-emitting and light-receiving elements] The arrangement of the light emitting element and the light receiving element according to the present invention is not limited as long as it satisfies the above conditions, but a preferred example of the arrangement will be described below. The first embodiment described below is a case where multiple light-emitting elements are arranged roughly concentrically around the center point of the light-receiving element, and the second embodiment is a case where multiple light-receiving elements are arranged roughly concentrically around the center point of the light-emitting element.

[0056] Here, "approximately concentric" means that the difference in distance (radius) from the center point of the light receiving element to the center point of each light emitting element is within 10%, preferably within 5%, and more preferably within 3%, and includes being identical. The "center point of the light receiving element" refers to the geometric center of the shape of the light receiving element when the light receiving element is viewed in a plan view. Also, the "center point of the light emitting element" refers to the geometric center of the light receiving element when the light emitting element is viewed in a plan view. The geometric center of the child shape. It should be noted that the term "planar view" refers to a view of the reflective photoplethysmographic sensor from the normal direction to the top surface of the substrate 41.

[0057] <First embodiment> FIG. 2 is a schematic diagram for explaining the arrangement of light-emitting elements and light-receiving elements that constitute the reflective photoelectric volume pulse wave sensor, in which FIG. 2(a) is a plan view, FIG. 2(b) is a plan view with each component disassembled, FIG. 2(c) is a cross-sectional view taken along the line AA', and FIG. 2(d) is a cross-sectional view taken along the line BB'. As shown in FIG. 2, the detection unit 14 has a light-transmitting substrate 41 on which a plurality of lead electrode portions 63a, 63b, 63c, and 63d of a light-transmitting first electrode (anode) 50 and a light-transmitting second electrode (cathode) 60 are formed.

[0058] It is preferable to use a substrate having a total light transmittance of 70% or more, more preferably 80% or more, and particularly preferably 90% or more, as the light-transmitting substrate 41. The total light transmittance can be measured according to JIS K 7375:2008 "Plastics - Determination of total light transmittance and total light reflectance". In addition, examples of opaque substrates (light-reflective substrates) include metal plates such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.

[0059] In Figure 2(b), the first electrode 50 includes a first central electrode portion 51 formed in the center of the light-transmitting substrate 41, and first circumferential electrode portions 52 and 52 arranged concentrically on the left and right sides of the first central electrode portion 51. The first circumferential electrode portions 52, 52 have an arc shape in a plan view, and are formed discontinuously so that the first circumferential electrode portions 52, 52 are not continuous with each other. The first central electrode portion 51 is formed so as to extend towards the lead electrode portion 63b. Furthermore, the two first circumferential electrode portions 52 and 52 are also formed so as to extend towards the lead electrode portion 63c.

[0060] The lead-out electrode portions 63 a , 63 b , 63 c , and 63 d are formed on the light-transmitting substrate 41 and serve as wiring for leading out to the side edge portions of the light-transmitting substrate 41 .

[0061] A light receiving element 70 is formed on the first central electrode portion 51 of the first electrode 50 so as to cover the first central electrode portion 51. The light receiving element 70 has a circular shape in a plan view. It is preferable to use a planar organic thin-film solar cell (OPV) or an organic photodiode (OPD) as the light receiving element 70, and it is particularly preferable to use an organic photodiode, which is flexible, comfortable to wear, and capable of reducing wavelength variation and brightness variation. The organic thin-film solar cell and the organic photodiode will be described in detail later.

[0062] Furthermore, light emitting elements 80, 80 are formed on the two left and right first circumferential electrode portions 52, 52 of the first electrode 50 so as to cover the first circumferential electrode portions 52, 52. The light emitting elements 80, 80 are not arcuate in plan view along the first circumferential electrode portions 52, 52, and are discontinuously formed so that the light emitting elements 80, 80 are not continuous with each other. In this manner, the two light emitting elements 80 and 80 formed on the first circumferential electrode portions 52 and 52 are arranged on a concentric circle with the central point of the light receiving element 70 as the center.

[0063] Moreover, the minimum width H of the light emitting element 80 in a plan view is preferably about 5 mm. Here, the "shortest width H" of the light emitting element 80 in plan view is, in the case where the light emitting element 80 has an arc shape in plan view, a tangent line is drawn to each of the outer peripheral surface and the inner peripheral surface of the arc shape, and a straight line is drawn between the tangent lines. It should be noted that, as shown in Fig. 6 described later, when the light emitting elements 81 and 82 are circular in plan view, the term refers to the diameter of the circle.

[0064] Here, the shortest distance h (mm) between at least one pair of the light-emitting element 80 and the light-receiving element 70 satisfies the above formula (1). As described above, the "shortest distance h" between the light-emitting element 80 and the light-receiving element 70 refers to the shortest distance h from the side edge of the light-receiving element 70 on the light-emitting element 80 side to the side edge of the light-emitting element 80 on the light-receiving element 70 side in the side cross-sectional view shown in FIG. 1. In FIG. 2, the light-receiving element 70 is circular in plan view, and the light-emitting element 80 is arc-shaped in plan view, so that the shortest distance h is between the outer peripheral surface of the light-receiving element 70 and the inner peripheral surface of the light-emitting element 80. Note that, as shown in FIG. 6 described later, when the light-emitting element 80 is circular in plan view, the shortest distance h is between the outer peripheral surface of the light-receiving element 70 and the outer peripheral surfaces of the light-emitting elements 81 and 82.

[0065] As the light emitting element 80, it is preferable to use a light emitting diode (LED) or an organic electroluminescence element (OLED), and it is particularly preferable to use an organic electroluminescence element in that variations in wavelength and brightness can be reduced. It is preferable that the two light emitting elements 80 and 80 emit light of the same wavelength.

[0066] A second electrode 60 is further formed on the light receiving element 70 and the light emitting element 80 . The second electrode (cathode) 60 comprises a second central electrode portion 61 formed at a position corresponding to the first central electrode portion 51 of the first electrode 50, and two second circumferential electrode portions 62 and 62 which are formed around the second central electrode portion 61 at positions corresponding to the first circumferential electrode portions 52 and 52 and surround the second central electrode portion 61 in an arc-like shape in a plan view without being interrupted. An extraction electrode portion 63a is connected to the second central electrode portion 61, and the extraction electrode portion 63a is formed on the translucent substrate 41, between the second circumferential electrode portions 62, and extends around one of the second circumferential electrode portions 62 to the side edge portion of the translucent substrate 41. The lead electrode portions 63d, 63d are also connected to the respective ends of the two second circumferential electrode portions 62, 62. The lead electrode portions 63d, 63d are formed to extend toward the side edge portions of the light-transmitting substrate 41.

[0067] In this manner, the first electrode 50, the extraction electrode portions 63a to 63d, the light receiving element 70, the light emitting element 80 and the second electrode 60 are formed on the light-transmitting substrate 41, and a light-transmitting substrate 42 is further provided on the second electrode 60, and the space between the two light-transmitting substrates 41 and 42 is sealed with a sealing material 43.

[0068] (Layout variation 1) FIG. 3 is a diagram showing a modified arrangement of the light-emitting elements and light-receiving elements of FIG. 2, and is a plan view for explaining the arrangement of the light-emitting elements and light-receiving elements that constitute the reflective photoelectric volume pulse wave sensor. Modification 1 shown in Fig. 3 is a case where the number of light-emitting elements shown in Fig. 2 is further increased. That is, a first light-emitting element 90 is further disposed between the light-receiving element 70 and the light-emitting element (hereinafter also referred to as the "second light-emitting element") 80 shown in Fig. 2, resulting in a structure in which the light-emitting elements 90 and 80 are disposed in a double configuration.

[0069] Of the multiple light-emitting elements 90 and 80, the first light-emitting element 90 arranged at a position close to the light-receiving element 70 is formed on two first circumferential electrode portions 52 and 52 of the first electrode 50 so as to cover the first circumferential electrode portions 52 and 52, similar to the second light-emitting element 80 shown in Fig. 2. Each of the first light-emitting elements 90 and 90 has an arc shape in a plan view along the first circumferential electrode portions 52 and 52, and is non-contiguous with the first light-emitting elements 90 and 90 so that they are not continuous with each other. It is formed intermittently.

[0070] Here, among the multiple light-emitting elements 90 and 80, the second light-emitting element 80 disposed at a position farther from the light-receiving element 70 has a shortest distance h between the second light-emitting element 80 and the light-receiving element 70 within a range that satisfies the above-mentioned formula (1). Note that the shortest distance between the light-receiving element 70 and the first light-emitting element 90 is not within a range that satisfies the above-mentioned formula (1).

[0071] Moreover, the minimum width of the first light emitting element 90 in a plan view is preferably about 5 mm. Here, when the first light-emitting element 90 has an arc shape in plan view, the shortest width of the first light-emitting element 90 refers to the length of a line perpendicular to the tangents drawn on the outer peripheral surface and the inner peripheral surface of the arc shape. When the light-emitting element has a circular shape in plan view, the shortest width of the first light-emitting element 90 refers to the diameter of the circle. Furthermore, in terms of ease of fabrication, it is preferable to place the first light-emitting element 90 at the midpoint of the distance h between the second light-emitting element 80 and the light-receiving element 70. Note that in Fig. 3, the first light-emitting element 90 is not placed at the midpoint due to the nature of the drawing.

[0072] Of the multiple first and second light-emitting elements 90 and 80, it is preferable that the first light-emitting elements 90 and 90 emit light of the same wavelength, and the second light-emitting elements 80 and 80 also emit light of the same wavelength, and it is also preferable that the first and second light-emitting elements 90 and 80 emit light of different wavelengths. Furthermore, it is preferable that the multiple first and second light-emitting elements 90 and 80 are controlled to be turned on individually.

[0073] In addition, it is preferable that the vital data (biological information) obtained based on the light emitted from the first light-emitting element 90, which is located close to the light-receiving element 70 among the multiple light-emitting elements 90 and 80, is processed by the information processing device 3 described later on the vital data obtained based on the light emitted from the second light-emitting element 80, which is located farther away than the first light-emitting element 90. Here, the light emitted from the second light-emitting element 80 is irradiated onto an artery deep in the skin, and the light reflected by the artery is received by the light-receiving element 70. As a result, the vital data acquired by the light-receiving element 70 contains noise because the light passes through a shallow part of the skin.

[0074] On the other hand, the vital data acquired based on the light emitted from the first light-emitting element 90 arranged in a position close to the light-receiving element 70 is data containing noise caused by light not being irradiated to the artery but to the capillaries located in the shallow part of the skin. Therefore, by subtracting this noisy data (vital data acquired based on the light emitted from the first light-emitting element 90) from the vital data acquired based on the light emitted from the second light-emitting element 80 and processing the data, it is possible to calculate valid data from which noise has been subtracted.

[0075] In addition, in Figure 2, the extraction electrode portions 63a, 63b, 63c, and 63d are arranged to be extracted to only one side edge portion of the light-transmitting substrate 40, but in the first modification shown in Figure 3, the extraction electrode portions 63a, 63b, 63c, and 63d are arranged to be extracted to both opposing side edges of the light-transmitting substrate 40.

[0076] (Layout variation 2) FIG. 4 is a modification of FIG. 2 and is a plan view for explaining the arrangement of light emitting elements and light receiving elements that constitute the reflective photoelectric volume pulse wave sensor. In variant example 2 shown in FIG. 4, the shortest horizontal width (symbol H in FIG. 4) in a planar view of the light-emitting element 80 shown in FIG. 2 is made thicker. Since the other configurations are similar, similar components are given similar symbols and their descriptions are omitted.

[0077] (Layout variation 3) FIG. 5 is a modification of FIG. 2 and is a plan view for explaining the arrangement of light emitting elements and light receiving elements that constitute the reflective photoelectric volume pulse wave sensor. 5, two types of second light-emitting elements 81 and 82 having different emission wavelengths are used, and a plurality of these two types of second light-emitting elements 81 and 82 are alternately arranged on a concentric circle centered on the light-receiving element 70. Each of the second light-emitting elements 81 and 82 has an arc shape in a plan view.

[0078] Furthermore, a plurality of first light-emitting elements 91 and 92 are further disposed between the plurality of second light-emitting elements 81 and 82 and the light-receiving element 70. These plurality of first light-emitting elements 91 and 92 emit two types of light with different emission wavelengths, similar to the second light-emitting elements 81 and 82. Each of the first light-emitting elements 91 and 92 also has an arc shape in a plan view. Furthermore, it is preferable that the plurality of first and second light emitting elements 91, 92, 81 and 82 are controlled to emit light (light up) individually. Here, among the multiple first and second light-emitting elements 91, 92, 81, and 82, the second light-emitting elements 81 and 82 arranged at positions far from the light-receiving element 70 have a shortest distance h between the second light-emitting elements 81 and 82 and the light-receiving element 70 within a range that satisfies the above-mentioned formula (1). Note that the shortest distance between the light-receiving element 70 and the first light-emitting elements 91 and 92 is not within a range that satisfies the above-mentioned formula (1). In addition, it is preferable that the information processing device 3 processes vital data (biological information) obtained based on light emitted from the first light-emitting elements 91 and 92, which are located closer to the light receiving element 70, based on vital data (biological information) obtained based on light emitted from the second light-emitting elements 81 and 82, which are located farther away than the first light-emitting elements 91 and 92, among the multiple light-emitting elements 91, 92, 81 and 82.

[0079] (Layout variation 4) FIG. 6 is a modification of FIG. 2 and is a plan view for explaining the arrangement of light emitting elements and light receiving elements that constitute the reflective photoelectric volume pulse wave sensor. 6, two types of second light-emitting elements 81 and 82 having different emission wavelengths are used, and these two types of second light-emitting elements 81 and 82 are alternately arranged on a concentric circle centered on the light-receiving element 70. The second light-emitting elements 81 and 82 have a circular shape in plan view, unlike the arc shape in plan view shown in FIG. Moreover, the second light emitting elements 81 and 82 have the shortest distance h between the second light emitting elements 81 and 82 and the light receiving element 70 within a range that satisfies the above-mentioned formula (1). Moreover, it is preferable that the plurality of second light emitting elements 81 and 82 are controlled so as to emit light (light up) individually.

[0080] 5 and 6, only the light-emitting elements 81, 82, 91, 92 and the light-receiving element 70 are shown, but similar to FIG. 2, the device includes two light-transmissive substrates 41, 42, a first electrode 50, extraction electrode portions 93a, 93b, 93c, 93d, a second electrode 60, and a sealing material 43.

[0081] <Second embodiment> As described above, the second embodiment is a case in which a plurality of light receiving elements are arranged concentrically around a light emitting element, and the other configurations are the same as those of the first embodiment. FIG. 7 is a schematic diagram for explaining the arrangement of the light-emitting elements and light-receiving elements that make up the reflective photoelectric volume pulse wave sensor, where FIG. 7(a) is a plan view, FIG. 7(b) is a plan view with each component disassembled, FIG. 7(c) is a cross-sectional view taken along the CC' arrow, and FIG. 7(d) is a cross-sectional view taken along the DD' arrow. As shown in FIG. 7, the detection unit 14 has a light-transmitting substrate 41 on which a plurality of lead electrode portions 63a, 63b, 63c, and 63d of a light-transmitting first electrode (anode) 50 and a light-transmitting second electrode (cathode) 60 are formed.

[0082] The first electrode 50 comprises a first central electrode portion 51 formed in the center of the light-transmitting substrate 41, and first circumferential electrode portions 52 and 52 arranged on a concentric circle with the first central electrode portion 51 as the center. The first circumferential electrode portions 52, 52 have an arc shape in a plan view, and are formed discontinuously so that the first circumferential electrode portions 52, 52 are not continuous with each other. The first central electrode portion 51 is formed so as to extend towards the lead electrode portion 63b. Furthermore, the two first circumferential electrode portions 52 and 52 are also formed so as to extend towards the lead electrode portion 63c.

[0083] The lead-out electrode portions 63 a , 63 b , 63 c and 63 d are formed on the light-transmitting substrate 41 and are configured as wiring for leading out to the side edge portions of the light-transmitting substrate 41 .

[0084] A light emitting element 80 is formed on the first central electrode portion 51 of the first electrode 50 so as to cover the first central electrode portion 51. The light emitting element 80 has a circular shape in a plan view.

[0085] Furthermore, light receiving elements 70, 70 are formed on two first circumferential electrode portions 52, 52 of the first electrode 50 so as to cover the first circumferential electrode portions 52, 52. Each of the light receiving elements 70, 70 has an arc shape in a plan view along the first circumferential electrode portions 52, 52, and is formed discontinuously so that the light receiving elements 70, 70 are not continuous with each other. In this manner, the two light receiving elements 70, 70 formed on the first circumferential electrode portions 52, 52 are arranged on a concentric circle with the light emitting element 80 at the center.

[0086] In addition, in FIG. 7, the shortest horizontal width W of the light receiving element 70 in a planar view is greater than the shortest distance h between the light receiving element 70 and the light emitting element 80. However, in terms of improving measurement accuracy, it is preferable that the shortest horizontal width W of the light receiving element 70 is the same as the shortest distance h between the light receiving element 70 and the light emitting element 80. Here, the shortest width W of the light receiving element 70 in plan view refers to the length of a line perpendicular to the tangents drawn on the outer peripheral surface and the inner peripheral surface of the arc shape when the light receiving element 70 is arc-shaped in plan view, similarly to the shortest width H of the light emitting element 80 described in Fig. 2. Note that when the light receiving element is circular in plan view, the shortest width W refers to the diameter of the circle.

[0087] A second electrode 60 is further formed on the light receiving element 70 and the light emitting element 80 . The second electrode (cathode) 60 comprises a second central electrode portion 61 formed at a position corresponding to the first central electrode portion 51 of the first electrode 50, and two second circumferential electrode portions 62, 62 which are formed around the second central electrode portion 61 at positions corresponding to the first circumferential electrode portions 52, 52 and surround the second central electrode portion 61 in an arc-like shape in a plan view without being interrupted. An extraction electrode portion 63a is connected to the second central electrode portion 61, and the extraction electrode portion 63a is formed on the translucent substrate 41, between the second circumferential electrode portions 62, and extends around one of the second circumferential electrode portions 62 to the side edge portion of the translucent substrate 41. The lead electrode portions 63d, 63d are also connected to the respective ends of the two second circumferential electrode portions 62, 62. The lead electrode portions 63d, 63d are formed to extend toward the side edge portions of the light-transmitting substrate 41.

[0088] In this manner, the first electrode 50, the extraction electrode portions 63a to 63d, the light receiving element 70, the light emitting element 80 and the second electrode 60 are formed on the light-transmitting substrate 41, and a light-transmitting substrate 42 is further provided on the second electrode 60, and the space between the two light-transmitting substrates 41 and 42 is sealed with a sealing material 43.

[0089] (Layout variation 5) FIG. 8 is a modification of FIG. 7 and is a plan view for explaining the arrangement of light emitting elements and light receiving elements that constitute the reflective photoelectric volume pulse wave sensor. In the fifth modification shown in Fig. 8, the number of light receiving elements shown in Fig. 7 is further increased. That is, a first light receiving element 90A is further disposed between the light receiving element 80 and the light receiving element (hereinafter also referred to as the "second light emitting element") 70 shown in Fig. 7, resulting in a structure in which the light receiving elements 70 and 90A are disposed in a double arrangement. Note that Fig. 8 shows a case in which the light receiving element and the light emitting element shown in Fig. 3 are disposed in reverse, and the rest of the configuration is the same, so a description thereof will be omitted.

[0090] It is preferable that the vital data (biological information) obtained based on the light received by the first light receiving element 90A, which is located near the light emitting element 80 among the multiple light receiving elements 70 and 90A, is processed by the information processing device 3 described later based on the vital data (biological information) obtained based on the light received by the second light receiving element 70, which is located farther away than the first light receiving element 90A.

[0091] In addition, in the second embodiment, the above-mentioned variants 2 to 4 can also be applied to an arrangement in which the light receiving element and the light emitting element are reversed (i.e., a configuration in which the light receiving element is arranged on a concentric circle with the light emitting element at the center).

[0092] In addition, in the reflective photoelectric volume pulse wave sensor of the present invention, there may be multiple types of shortest distance between the light-emitting element and the light-receiving element, and the light-emitting element and the light-receiving element having the shortest distance suitable for sensing may be selected. In other words, it is preferable to use a device that has multiple light-emitting elements and / or multiple light-receiving elements and that has multiple variations in the shortest distance between the light-emitting elements and the light-receiving elements, and to be provided with a mechanism for extracting the shortest distance that is most suitable for sensing.

[0093] For example, as shown in Fig. 9(a), there is a device in which a plurality of light-emitting elements 180 are arranged on a concentric circle with one light-receiving element 170 at the center, and there are a plurality of variations in the shortest distance, and as shown in Fig. 9(b), there is a device in which a plurality of light-receiving elements 170 and a plurality of light-emitting elements 180 are arranged in a matrix shape. Then, each pixel is configured to be driven individually. In addition, whether it is most suitable for sensing is determined by whether the inflection points (indicated by the arrow in the figure) can be clearly confirmed in the waveform of the vital data obtained from the light receiving element, as shown in Figure 9(c). For example, if there is a lot of noise, the inflection points will be hidden, so in order to obtain a more accurate waveform, it is necessary to increase the amplitude (height), and it is effective to capture the points where the volume change is large according to the principle of PPG.

[0094] 1.2 [Overall configuration example of a reflective photoplethysmography sensor] The overall configuration of the reflective photoplethysmographic sensor can take on a variety of forms and configurations. For example, the basic overall configuration preferably includes a light-emitting element that is driven to flash and emit light at a frequency higher than the frequency of the volume pulse wave of the living body based on a signal from an oscillator, a light-receiving element that receives the light emitted from the light-emitting element and the light reflected by the living tissue of the measurement target from the external light, and generates a signal having a signal level corresponding to the amount of received light, an extraction means that extracts a signal component due to the external light from the signal generated by the light-receiving element, a reduction means that reduces a noise signal caused by external light, etc. in the signal generated by the light-receiving element by subtracting the signal component extracted by the extraction means from the signal generated by the light-receiving element, and a means for generating a signal representing the volume pulse wave of the living body of the measurement target based on the signal after the noise signal component caused by external light, etc. is reduced by the reduction means.

[0095] 1.3 [Components of the reflective photoplethysmography sensor] Among the various components of the reflective photoplethysmogram sensor, the main components, the light-emitting element and the light-receiving element, will be described in detail below.

[0096] <Light emitting element> In the present invention, the light emitting element is used as a light source for irradiating the living tissue with light. As the light-emitting element, both an organic light-emitting diode (OLED) and an inorganic light-emitting diode (LED) can be used, and there is no particular limitation. However, as the light-emitting element according to the present invention, it is preferable to use an organic electroluminescent element (also called "OLED", "organic EL element", or "organic photodiode"), which is a light-emitting element composed of a planar organic layer, because it is flexible, has a good wearing feeling, and can reduce wavelength variation and brightness variation. In particular, a configuration in which a wavelength conversion filter that converts the visible light of the organic EL element to near infrared light (IR) is disposed on the organic EL element that emits red light is preferable. Alternatively, LEDs and a light guide plate may be used as planar light emitting elements. In display backlights, LEDs are placed on the edge of the light guide plate, and light is incident on the side edge of the light guide plate. Furthermore, micro LEDs may be used with a resolution that can be considered as a surface. It is more preferable to provide a scattering layer to reduce the localized increase in brightness of the LEDs.

[0097] (Organic EL element) An organic EL element suitable for the present invention may have, for example, an anode and a cathode on a flexible resin substrate, and an organic functional layer group including a light-emitting layer is sandwiched between the anode and the cathode at opposing positions. Furthermore, depending on the purpose, each functional layer such as a sealing member, a gas barrier layer, and a light extraction layer may be appropriately combined to configure the organic EL element.

[0098] Representative examples of the structure of the organic EL element according to the present invention are listed below, but the structure of the organic EL element applicable to the present invention is not limited to these exemplified structures.

[0099] (1) Anode / light-emitting layer / cathode (2) Anode / light-emitting layer / electron transport layer / cathode (3) Anode / hole transport layer / light emitting layer / cathode (4) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (5) Anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (6) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode (7) Anode / hole injection layer / hole transport layer / (electron blocking layer / )light-emitting layer / (hole blocking layer / )electron transport layer / electron injection layer / cathode

[0100] In an organic EL element, an electric field is applied from the outside, holes are injected from the anode into the hole transport layer, and electrons are injected from the cathode into the electron transport layer. The injected carriers move between molecules by hopping. In the light-emitting layer, the holes and electrons recombine to generate electrically neutral excitons. The excitons emit light according to the luminescence quantum efficiency and are deactivated by radiation. The light generated in the organic layer is extracted. The gas is then extracted from the bottom surface into the air.

[0101] The details of each of the specific constituent layers constituting the organic EL element applicable to the present invention and the manufacturing method thereof are not particularly limited, and known constituent materials and manufacturing methods can be applied. For example, the contents described in JP-A-2013-089608, JP-A-2014-120334, JP-A-2015-201508, WO 2018 / 51617, etc. can be referred to.

[0102] (wavelength conversion filter) The organic EL element according to the present invention is preferably provided with a wavelength conversion filter that converts visible light of the organic EL element into near-infrared light.

[0103] The wavelength conversion filter according to the present invention preferably contains a luminescent material (e.g., a luminescent pigment) having wavelength conversion ability. The wavelength conversion filter according to the present invention is not particularly limited in shape or manufacturing method, so long as it contains a luminescent pigment having wavelength conversion ability, and is appropriately determined depending on the intended use.

[0104] The wavelength conversion filter according to the present invention preferably has a function of absorbing light from an organic EL element that emits light within the visible light region including the near-infrared light region (380 to 780 nm), preferably the green to red region including the near-infrared light region (495 to 750 nm), particularly preferably the red region (600 to 700 nm), and converting the light into near-infrared light, for example, light emitted in a region exceeding 700 nm and not exceeding 1500 nm, or further having an emission maximum around 850 nm.

[0105] The wavelength conversion filter and the organic EL element may be separately manufactured and then laminated together, or the wavelength conversion filter may be directly coated on the organic EL element to form a laminate. If necessary, a cut filter for removing light emitted without being wavelength converted may be laminated or included.

[0106] From the viewpoint of miniaturization and maintaining flexibility, the thickness of the wavelength conversion filter according to the present invention is preferably in the range of 0.01 to 1000 μm, more preferably in the range of 1 to 500 μm, and even more preferably in the range of 10 to 300 μm.

[0107] The wavelength conversion filter according to the present invention may contain, in addition to the luminescent dye, various well-known additives such as a colorant, a light stabilizer, an antioxidant, a surfactant, a flame retardant, an inorganic additive, a clarifying agent, an ultraviolet absorber, a filler, and light-scattering particles, as necessary.

[0108] <Photodetector> The light receiving element according to the present invention functions as a sensor that detects light reflected by biological tissue out of light irradiated onto the biological tissue from the light emitting element and converts the light into electricity. As the light receiving element, it is preferable to use a planar organic photo diode (OPD) or organic photovoltaics (OPV). In particular, it is preferable to use an OPD, which is flexible, has a good wearing comfort, and can reduce wavelength variation and brightness variation.

[0109] (1) Organic photodiode As the light receiving element according to the present invention, a conventionally known organic photodiode (OPD) can be used. For example, an organic photodiode is a transparent conductive material such as ITO (Indium-Tin Oxide) formed on a substrate of light-transmitting resin or glass by sputtering or resistance heating deposition. The basic components of this photoelectric conversion element are an anode made of a conductive film, a photoelectric conversion layer formed by depositing an electron donating layer and an electron accepting layer on the anode by a method such as resistance heating deposition, and a cathode made of a metal formed on top of the layer by the same method such as resistance heating deposition.

[0110] When an organic photodiode having such a structure is irradiated with light, light absorption occurs in the photoelectric conversion region, and excitons are formed. Then, the carriers are separated, and the electrons move to the cathode through the electron-accepting layer, and the holes move to the anode through the electron-donating layer. This creates a current between the two electrodes. An electromotive force is generated, and by connecting an external circuit, an electrical signal can be extracted.

[0111] The photoelectric conversion layer may be composed of a single layer or multiple layers. The photoelectric conversion layer may have various combinations such as an intrinsic layer (I layer), a p-type layer / I layer, an I layer / n-type layer, a p-type layer / I layer / n-type layer, or a p-type layer / n-type layer.

[0112] For example, a structure shown in Fig. 13D of US Patent Publication No. 2017 / 0156651 can be used. For various organic materials used in organic photodiodes, see JP-T-2017-532546 and JP-A-2006-261172.

[0113] (2) Organic thin film solar cells As the light receiving element according to the present invention, various types of conventionally known organic thin film solar cells (OPV) can also be used. For example, a bulk heterojunction type organic photoelectric conversion element having a basic structure in which an anode which is a transparent electrode, a hole transport layer, a photoelectric conversion layer which is a bulk heterojunction layer, an electron transport layer, and a cathode are sequentially stacked on one surface of a substrate can be used. In addition, other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.

[0114] The photoelectric conversion layer is a layer that converts light energy into electrical energy, and is configured to have a bulk heterojunction layer in which p-type semiconductor material and n-type semiconductor material are uniformly mixed. The p-type semiconductor material functions relatively as an electron donor, and the n-type semiconductor material functions relatively as an electron acceptor. Here, the electron donor and electron acceptor are "electron donors and electron acceptors that, upon absorbing light, transfer electrons from the electron donor to the electron acceptor to form a hole-electron pair (charge-separated state)", and do not simply donate or accept electrons like an electrode, but donate or accept electrons through a photoreaction.

[0115] Furthermore, for the purpose of further improving the solar light utilization rate (photoelectric conversion efficiency), such photoelectric conversion elements may be stacked to form a tandem structure (a structure having a plurality of bulk heterojunction layers).

[0116] Examples of p-type semiconductor materials include various condensed polycyclic aromatic compounds and conjugated compounds. Examples of n-type semiconductor materials include fullerene, octaazaporphyrin, perfluorinated p-type semiconductors, and polymer compounds containing aromatic carboxylic anhydrides or imidized products thereof as a skeleton, such as naphthalene tetracarboxylic anhydride, naphthalene tetracarboxylic diimide, perylene tetracarboxylic anhydride, and perylene tetracarboxylic diimide.

[0117] 2. [Biometric information measuring device] The reflective photoelectric volume pulse wave sensor of the present invention can be applied to various types of biological information measuring devices depending on the purpose. An application example will be described below.

[0118] (Application example 1) FIG. 10 is a perspective view of a biological information measuring device using a reflective photoelectric volume pulse wave sensor that can be worn around the wrist. The biological information measuring device 1 has a main body 10 that is worn on the patient's wrist like a wristwatch. Specifically, the main body 10 has a belt 20 and is worn on the patient's wrist by the belt 20. It is possible. In addition, a detection unit 14 including a light emitting element 80 and a light receiving element 70, which will be described later, is disposed inside the belt 20, and the detection unit 14 and the main body 10 are electrically connected.

[0119] A constant amount of light is constantly output from the light emitting element 80 and irradiated inside the living body, and the amount of light reflected varies depending on the amount of hemoglobin that binds to oxygen circulating in the blood. The light receiving element 70 outputs a signal to the main body that depends on the amount of reflected light received, and is able to measure the oxygen concentration in the patient's blood.

[0120] The main body 10 is formed in a flat shape, and is provided on its periphery and surface with an operation unit 12 and a display unit 15. Also housed inside is an electric circuit and the like (see FIG. 11) that performs functions equivalent to the control unit 11, the recording unit 13, and the like.

[0121] The operation unit 12 includes, for example, a power switch 12a, a timing switch (operation switch) 12b, and the like.

[0122] (Application example 2) Fig. 11 is a diagram showing an example of a functional configuration of the biological information measuring device 1. As shown in Fig. 11, the biological information measuring device 1 is configured to include a control unit 11, an operation unit 12, a recording unit 13, a detection unit 14, a display unit 15, a wireless communication unit 16, an acceleration detection unit 17, a power supply unit 18, and the like.

[0123] The control unit 11 includes a CPU (Central Processing Unit), a RAM (Random Access Memory The CPU of the control unit 11 reads out various programs such as a system program and a processing program recorded in the recording unit 13, loads them into the RAM, and executes various processes according to the loaded programs. The control unit 11 also has a clock function unit, from which the date and time of measurement of the vital data can be obtained.

[0124] The operation unit 12 is a detection unit that detects instructions from an operator, and includes various switches, various function buttons, etc., and outputs operation signals from these to the control unit 11.

[0125] The recording unit 13 is composed of a semiconductor non-volatile memory, etc. In the recording unit 13, a system program and various programs required for the functioning of the biological information measuring device 1 in this embodiment, parameters and files required for executing the programs, etc. are recorded. For example, the recording unit 13 continuously records the measured vital data from the start to the end of the measurement. Note that the vital data may be recorded at regular intervals from the start to the end of the measurement.

[0126] The detection unit 14 is a data acquisition unit that acquires vital data of a patient by applying the reflective photoelectric volume pulse wave sensor of the present invention, and as described above, is equipped with a light-emitting element and a light-receiving element, etc., and is configured to be wearable on a biological part such as the wrist. The detection unit 14 controls the light-emitting element drive circuit 14b via the measurement control unit 14a, causes the light-emitting element provided in the detection unit 14 to emit red light and infrared light toward the biological part, and the analog signal of the reflected light from the biological part received by the light-receiving element provided in the detection unit 14 is subjected to noise removal and signal amplification via the analog front-end circuit 14c, prepared as a voltage signal to be input into the AD converter 14d, and then converted into digital data by the AD converter 14d.

[0127] After being converted into digital data by the AD converter 14d, the digital data Based on this, the control unit 11 calculates vital data such as SpO2 and pulse rate. The calculated vital data is recorded in the recording unit 13.

[0128] The display unit 15 is configured to include, for example, an LCD (Liquid Crystal Display) and performs display using, for example, a dot matrix method, and performs display according to an instruction of a display signal input from the control unit 11.

[0129] The wireless communication unit 16 has a wireless interface for transmitting and receiving data to and from the information processing device 3 via wireless communication such as Bluetooth (registered trademark) or Wi-Fi (registered trademark).

[0130] The acceleration detection unit 17 detects the movement of the patient based on a change in acceleration. Specifically, the acceleration detection unit 17 generates an acceleration signal corresponding to the acceleration applied to itself due to the patient's body movement, etc., and outputs the acceleration signal to the control unit 11.

[0131] The power supply unit 18 supplies the power required for the operation of each part of the vital information measuring device 1 to the relevant part. The power supply unit 18 supplies the power output from a battery (not shown) at an operating voltage for each part.

[0132] (Configuration of Biometric Information Processing Device) The information processing device 3 is a device capable of analyzing the vital data transmitted from the biological information measuring device 1. As the information processing device 3, for example, a smartphone, a tablet, a PC (Personal Computer), etc. can be applied, but is not particularly limited.

[0133] Fig. 12 shows an example of a functional configuration of the information processing device 3. As shown in Fig. 12, the information processing device 3 includes, for example, a control unit 31, an operation unit 32, a recording unit 33, a display unit 34, a communication unit 35, and the like.

[0134] The control unit 31 is composed of a CPU, a RAM, etc. The CPU of the control unit 31 reads out various programs such as a system program and a processing program recorded in the recording unit 33, expands them in the RAM, and executes various processes according to the expanded programs.

[0135] Specifically, in the case where the first and second light-emitting elements 90, 80 (91, 92, 81 and 82) are arranged on a concentric circle centered on the light-receiving element 70 at different distances from the light-receiving element 70 in the vital information measuring device 1 (for example, in the case of the arrangement shown in Figures 3 and 5), the control unit 31 performs a process of subtracting the vital data obtained based on the light emitted from the first light-emitting element 90 (91 and 92) from the vital data obtained based on the light emitted from the second light-emitting element 80 (81, 82) among the vital data output from the vital information measuring device 1, to calculate valid vital data with noise removed.

[0136] In addition, when the first and second light receiving elements 70, 90A are arranged on a concentric circle centered on the light emitting element 80 at different distances from the light emitting element 80 (for example, in the case of the arrangement in Figure 8), a process is performed to calculate valid vital data with noise removed by subtracting the vital data obtained based on light received by the first light receiving element 90A from the vital data obtained based on light received by the second light receiving element 70 among the vital data output from the vital information measuring device 1.

[0137] The operation unit 32 includes various switches, various function buttons, a touch panel, etc., and outputs operation signals from these to the control unit 31.

[0138] The recording unit 33 is composed of a semiconductor non-volatile memory, etc. In the recording unit 33, system programs, various programs, parameters and files required for executing the programs, etc. are recorded.

[0139] For example, in the recording unit 33, vital data output from the biological information measuring device 1 is recorded. Specifically, in the bioinformation measuring device 1, when the first and second light-emitting elements 90, 80 (91, 92, 81, 82) are arranged on a concentric circle centered on the light-receiving element 70 at different distances from the light-receiving element 70 (for example, in the case of the arrangement shown in Figures 3 and 5), vital data based on the first light-emitting element 90 (91, 92), vital data based on the second light-emitting element 80 (81, 82), and valid vital data obtained by subtracting the vital data obtained based on the light emitted from the first light-emitting element 90 (91, 92) from the vital data obtained based on the light emitted from the second light-emitting element 80 (81, 82), etc. are recorded.

[0140] Furthermore, when the first and second light receiving elements 70, 90A are arranged on a concentric circle centered on the light emitting element 80 at different distances from the light emitting element 80 (for example, in the case of the arrangement in Figure 8), vital data obtained based on the light received by the first light receiving element 90A, vital data obtained based on the light received by the second light receiving element 70, and valid vital data obtained by subtracting the vital data obtained based on the light received by the first light receiving element 90A from the vital data obtained based on the light received by the second light receiving element 70 are recorded.

[0141] The display unit 34 is configured to include a monitor such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display), and displays various screens according to instructions of a display signal input from the control unit 31.

[0142] The communication unit 35 communicates with the biological information measuring device via wireless communication such as Bluetooth or Wi-Fi. The communication unit 35 has an interface for transmitting and receiving data to and from the computer 1. The communication unit 35 may have a wired interface such as a USB. EXAMPLES

[0143] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.

[0144] Reflective photoplethysmography sensors 1 to 11 were designed, each with a different minimum distance h (mm) between the light-emitting element and the light-receiving element, and each sensor was attached to the back of the arm, the ulnar side of the wrist, the radial side of the wrist, the abdomen, and the chest to measure the AC / DC values ​​described below.

[0145] Specifically, the light receiving element used was "KPD30S (manufactured by Kyoto Semiconductor Co., Ltd.)". As the light emitting element, a wavelength conversion film was attached onto a 60 x 80 mm OLED panel (peak wavelength 630 nm), and a masked ring-shaped light source was obtained on the device that obtained a peak wavelength of 790 nm so that light other than the ring part was cut off, and this ring-shaped light source was used. The light receiving element was placed and fixed at the center of the ring-shaped light source, and the ring diameter was adjusted so that the shortest distance h between the light receiving element and the ring-shaped light source was as shown in Tables I and II below, thereby obtaining reflective photoplethysmographic sensors 1 to 11 having the structure shown in Figure 2. The width of the ring-shaped light source was 2 mm, and the light intensity was 25 to 100 mA / m 2 The sensitivity of the sensor was adjusted according to the amount of light. The sampling frequency was 500Hz, and the measurements were taken for 60 seconds, and the data was analyzed offline. The pulling was obtained using an analog front end (AFE) "AFE4403EVM (Texas Instruments)". The AC / DC was calculated as described below, and was calculated as the average value of 10 measurements for the back of the arm, ulnar side of the wrist, radial side of the wrist, abdomen, and chest. A band-pass filter and a low-pass filter were used on the circuit side, and moving average and frequency domain methods were used for data processing.

[0146] In addition, the thickness t of the skin (epidermis + dermis) on the back of the arm where the device was worn was 4 mm, the thickness t of the skin on the ulnar side of the wrist was 3.5 mm, the thickness t of the skin on the radial side of the wrist was 3 mm, the thickness t of the skin on the abdominal area was 2.5 mm, and the thickness t of the skin on the chest was 2 mm.

[0147] <AC / DCについて> As explained in the above "<Calculation method of oxygen saturation>", the AC component of absorbance was determined by calculating the difference between the maximum and minimum values ​​of the change in absorbance over time, and the DC component of absorbance was determined by calculating the average value of the change in absorbance over time. The AC / DC value was then calculated by dividing the AC component of absorbance by the DC component of absorbance, and is shown in Tables I and II below.

[0148] In the present invention, it is practically preferable that the AC / DC value is within the range of 0.20%, and particularly preferable that it is 0.30% or more. In addition, in consideration of the size of the device, it is practically preferable that it is 0.80% or less.

[0149] [Table 1]

[0150] [Table 2]

[0151] As shown in the above results, it can be confirmed that the AC / DC value increases by increasing the shortest distance h. However, if the shortest distance h is made too large, the attenuation of the light amount becomes large, power consumption increases, and the signal strength itself decreases, making it more susceptible to noise. Therefore, the reflective photoelectric volume pulse wave sensor of the present invention, which satisfies the above formula (1), is less susceptible to attenuation of the amount of light, does not increase power consumption, and does not decrease signal strength itself, making it less susceptible to noise, compared to the reflective photoelectric volume pulse wave sensor of the comparative example. Therefore, it is recognized that the measurement accuracy is excellent. [Explanation of symbols]

[0152] 1. Biometric information measuring device 14 Detection section 41,42 Transparent substrate 43 Encapsulating materials 50 1st electrode 60 2nd electrode 70 Light receiving element (second light receiving element) 80 Light-emitting element (second light-emitting element) 81, 82 Second light-emitting element 90A First light receiving element 90, 91, 92 First light emitting element h The shortest distance between the light-emitting element and the light-receiving element H Minimum width of the light-emitting element in plan view W: Minimum width of the light receiving element in plan view

Claims

1. A reflective photoplethysmographic sensor having a planar light emitting element and a light receiving element, The light emitting element and the light receiving element do not face each other in the vertical direction, The shortest distance between the light-emitting element and the light-receiving element is h (mm), If the thickness of the human skin (epidermis + dermis) is t (mm) and the thickness is within the range of 0.1 to 4 mm, A reflective photoplethysmographic sensor, characterized in that the shortest distance h (mm) between at least one pair of the light-emitting element and the light-receiving element satisfies the following formula (1): Formula (1): (t×0.7) ２ ≦h≦(t×1.3) ２

2. 2. The reflective photoelectric volume pulse wave sensor according to claim 1, wherein the shortest distance between the light emitting element and the light receiving element is within a range of 2 to 25 mm.

3. 3. The reflective photoelectric volume pulse wave sensor according to claim 1, wherein the light emitting element is an organic electroluminescence (EL) element.

4. 4. The reflective photoplethysmographic sensor according to claim 1, wherein the light receiving element is an organic photodiode.

5. 5. The reflective photoelectric volume pulse wave sensor according to claim 1, further comprising a plurality of the light-emitting elements, each of the light-emitting elements being arranged on a substantially concentric circle centered on the center point of the light-receiving element.

6. A plurality of the light-emitting elements are provided, and at least two of the plurality of light-emitting elements emit light of the same wavelength; 6. The reflective photoplethysmographic sensor according to claim 1, wherein the light emitting elements are each capable of emitting light individually.

7. The reflective photoelectric volume pulse wave sensor according to claim 6, characterized in that information and data acquired based on light emitted from a light-emitting element that is located close to the light-receiving element and a light-emitting element that is located farther away from the light-emitting element are processed.

8. 5. The reflective photoelectric volume pulse wave sensor according to claim 1, further comprising a plurality of the light receiving elements, each of the light receiving elements being arranged on a substantially concentric circle centered on the center point of the light emitting element.

9. 9. The reflective photoelectric volume pulse wave sensor according to claim 8, characterized in that information and data acquired based on light received from a light receiving element located close to the light emitting element and a light receiving element located farther away from the light receiving element are processed.

10. There are a plurality of types of shortest distances between the light emitting element and the light receiving element, 10. The reflective photoelectric volume pulse wave sensor according to claim 1, wherein the light emitting element and the light receiving element having the shortest distance suitable for sensing are selected.

11. A biological information measuring device comprising the reflective photoelectric volume pulse wave sensor according to any one of claims 1 to 10.

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