Photoelectric volume plethysmography sensor and pulse wave detection method

Abstract

This photoelectric volume pulse wave sensor (100A) is provided with a light-emitting element (500) and a light-receiving element (400). Electrodes constituting the light-emitting unit (500) or the light-receiving element (400) are surface electrodes, at least one of these electrodes being also used as an electrode for sensing body movement.

Description

[Technical Field]

[0001] The present invention relates to a photoplethysmography sensor and a method for detecting pulse waves, and more particularly to a photoplethysmography sensor that has fewer parts, can reduce costs, and can detect body movement and pulse waves more accurately. [Background technology]

[0002] In recent years, telemedicine, which involves measuring health status outside of hospitals and receiving medical services remotely, has been actively explored, and there is a need for devices that allow individuals to continuously measure their health themselves, even in remote locations. In particular, there is a demand for user-friendly devices that (1) allow for non-invasive measurement, (2) are easy to wear, and (3) can perform highly accurate and stable measurements to acquire vital data. Among these, photoplethysmography (PPG) sensors (hereinafter also simply referred to as "PPG sensors") are attracting particular attention, as they are being used in pulse oximeters and smartwatches. A PPG sensor consists of a light-emitting element and a light-receiving element. When light from the light-emitting element shines on the light-receiving element, a photoelectric effect occurs, and the sensor obtains a signal from the object being measured by converting the light into electricity. For example, if the object being measured is biological tissue including blood vessels, it can detect pulse waves caused by the pulsation of blood vessels as light passes through or reflects within the body.

[0003] However, when measuring pulse waves with a PPG sensor, changes in the measurement position due to skin stretching caused by body movement, and gaps between the device and the body causing the detection of ambient light, resulted in the inclusion of changes in light attenuation within the biological tissue and ambient light signals, making it difficult to accurately detect pulse waves. Conventionally, a method was employed in which a sensor for detecting body movement was provided separately from the PPG sensor, and the PPG signal and the body movement signal were processed to extract only the pulse wave signal. Accelerometers, capacitive sensors, and optical sensors are used as sensors for detecting body movement. Furthermore, it is known that a clearer pulse waveform can be obtained by preferably applying appropriate pressure to the measurement unit. However, these sensors have a separate motion sensor in addition to the PPG sensor, which increases the number of parts and leads to higher costs. Furthermore, there were problems such as the inability to accurately detect body movement because the positions of the PPG sensor and the motion sensor did not coincide. For example, Patent Document 1 discloses a method for removing noise from a PPG sensor using a PPG sensor and a capacitive motion sensor. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2014 / 0058217 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] This invention has been made in view of the above-mentioned problems and circumstances, and its objective is to provide a photoplethysmography sensor and a pulse wave detection method that have fewer parts, can reduce costs, and can detect body movement and pulse waves more accurately. [Means for solving the problem]

[0006] In order to solve the above problems, the inventors of the present invention, in the process of investigating the causes of the above problems, discovered that by using at least one electrode among the electrodes constituting the light-emitting element or light-receiving element as an electrode for detecting body movement, the number of parts can be reduced, costs can be lowered, and body movement and pulse waves can be detected more accurately, leading to the present invention. In other words, the above-mentioned problems according to the present invention are solved by the following means.

[0007] 1. A photoplethysmography sensor comprising a light-emitting element and a light-receiving element, The electrodes constituting the light-emitting element or the light-receiving element are surface electrodes, and the anode of the light-emitting element is used in combination as an electrode for detecting body movement. death, When measuring pulse waves, light emitted from the light-emitting element onto the living body is transmitted through or reflected within the living body and enters the light-receiving element, where it is converted into photoelectric energy to detect changes in the volume pulse wave. When detecting the aforementioned body movement, the change in capacitance between the electrode that detects the body movement and the living body is detected. The pulse wave and body movement are measured alternately at a frequency higher than the pulse wave frequency. The photoplethysmogram sensor to be used.

[0009] 2 . When the photoplethysmogram sensor is attached to a measurement site of a living body, a light-transmissive elastic dielectric layer that contacts the measurement site is Prepare, An electrode for detecting the body movement is provided on the upper surface of the measurement area via the elastic dielectric layer. The first In the section photoplethysmogram sensor described.

[0010] 3 . Item 1 or The In item 2 A method for detecting a pulse wave using the photoplethysmogram sensor described, wherein an electrode constituting the light-emitting element or the light-receiving element is a planar electrode, and body movement is also detected by using the anode of the light-emitting element among these electrodes, A method for detecting a pulse wave in which pulse wave data obtained by using the photoplethysmogram sensor and body movement data are each optimized and a difference is taken.

[0011] 4 . When the pulsating component in the signal corresponding to the absorbance of the light detected by the light-receiving element is defined as AC and the non-pulsating component is defined as DC, an error display is made when the perfusion index (PI) represented by the following formula (1) is less than 0.5%, and it is determined to be normal and measured when it is 0.5% or more. The 3 method for detecting a pulse wave according to item. Formula (1): PI(%) = AC / DC × 100

[0012] 5 . When the photoplethysmogram sensor is attached to a measurement site of a living body, a light-transmissive elastic dielectric layer that contacts the measurement site is Established, On the upper surface of the measurement area, via the elastic dielectric layer The electricity for detecting the body movement The extreme is provided to detect a pulse wave and body movement. The 3 method for detecting a pulse wave according to item or 4 item.

[0013] 6 . When viewed in a plan view, among the contact areas of the elastic dielectric layer that contacts the measurement site, the contact area of the portion that overlaps with the electrode for detecting the body movement is 200 mm 2 or more, according to the 5 method for detecting a pulse wave according to claim

[0014] 7 . The pressure applied to the measurement site of the living body equipped with the photoplethysmographic sensor is 0.02 N / cm 2 or more, according to any one of claims 3 to 6 of the method for detecting a pulse wave according to any one of claims

Advantages of the Invention

[0015] By the above means of the present invention, it is possible to provide a photoplethysmographic sensor and a method for detecting a pulse wave that have a small number of components, can reduce costs, and can detect body movement and pulse waves more accurately. Although the mechanism of manifestation or the mechanism of action of the effects of the present invention is not clearly defined, it is speculated as follows. In the photoplethysmographic sensor of the present invention, at least one of the electrodes constituting the light-emitting element or the light-receiving element is used in combination as an electrode for detecting body movement. Therefore, without separately providing a body movement sensor as in the conventional art, the number of components can be reduced, and pulse waves and body movement can be detected at a low cost. In addition, since the position for detecting the pulse wave and the position for detecting the body movement coincide, accurate body movement can be detected, and by subtracting the body movement data from the pulse wave data including noise and the like, the pulse wave excluding the body movement can be detected with high accuracy.

Brief Description of the Drawings

[0016] [Figure 1] Cross-sectional view showing an example of the configuration of the reflection-type photoplethysmographic sensor of the present invention [Figure 2] Cross-sectional view showing the details of the configuration of the reflection-type photoplethysmographic sensor of FIG. 1 [Figure 3] Cross-sectional view showing an example of the configuration of the transmission-type photoplethysmographic sensor of the present invention [Figure 4] Figure 3 is a cross-sectional view showing the detailed configuration of a transmissive photoplethysmography sensor. [Figure 5A] Schematic plan view of an organic EL element [Figure 5B] A schematic cross-sectional view showing an example of the configuration of an organic EL element. [Figure 6A] Schematic planar section of an organic photodiode. [Figure 6B] A schematic cross-sectional diagram showing an example of the configuration of an organic photodiode. [Figure 7A] Schematic cross-section of a reflective photoplethysmography sensor attached to the measurement site. [Figure 7B] Schematic cross-section of a reflective photoplethysmography sensor attached to the measurement site. [Figure 7C] Schematic cross-section of a reflective photoplethysmography sensor attached to the measurement site. [Figure 8] Perspective view of a biometric information measurement device using a reflective photoplethysmography sensor that can be worn on the wrist. [Figure 9] A diagram showing an example of the functional configuration of a biological information measurement device. [Figure 10] A flowchart showing an example of pulse wave detection processing. [Figure 11] This figure shows the driving method for the light-emitting element, light-receiving element, and motion detection electrode. [Figure 12] A diagram showing an example of the functional configuration of an information processing device. [Figure 13] Planar cross-sectional view illustrating the contact area in the motion detection electrode. [Figure 14] Figure showing the results of the example. [Figure 15A] Figure showing the results of the example. [Figure 15B] Figure showing the results of the example. [Figure 15C] Figure showing the results of the example. [Figure 16] Figure showing the results of the example. [Modes for carrying out the invention]

[0017] The photoplethysmography sensor of the present invention is a photoplethysmography sensor comprising a light-emitting element and a light-receiving element, wherein the electrodes constituting the light-emitting element or the light-receiving element are surface electrodes, and at least one of these electrodes is used in combination as an electrode for detecting body movement. This feature is a technical feature common to or corresponding to each of the embodiments described below.

[0018] In embodiments of the present invention, it is preferable that light irradiated onto a living body is transmitted through or reflected within the living body, enters the light-receiving element, and is converted into photoelectricity to detect pulse waves, that is, that is, both reflective and transmissive types can be effectively used.

[0019] Furthermore, when the photoplethysmography sensor is attached to a measurement site on a living body, it is preferable to provide a light-transmitting elastic dielectric layer that comes into contact with the measurement site on the surface of the electrode that detects body movement, as this can improve the detection accuracy of body movement and pulse waves.

[0020] The pulse wave detection method of the present invention is a pulse wave detection method using the photoplethysmography sensor, wherein the electrodes constituting the light-emitting element or the light-receiving element are surface electrodes, and body movement is also detected by using at least one of these electrodes in combination, and the pulse wave data obtained using the photoplethysmography sensor and the body movement data are optimized and the difference is taken. As a result, the number of parts is reduced, costs are reduced, and body movement and pulse waves can be detected more accurately.

[0021] Furthermore, when the pulsating component of the signal corresponding to the absorbance of light detected by the light-receiving element is defined as AC and the non-pulsating component as DC, it is preferable to display an error when the perfusion index (PI) represented by formula (1) is less than 0.5%, and to determine that it is normal when it is 0.5% or more, thereby improving the detection accuracy of body movement and pulse waves.

[0022] When the aforementioned photoplethysmography sensor is attached to a measurement site in a living body, it is preferable to provide a light-transmitting elastic dielectric layer that comes into contact with the measurement site on the surface of the electrode that detects body movement, thereby improving the detection accuracy of both the pulse wave and the pulse wave.

[0023] When viewed from above, the contact area of ​​the elastic dielectric layer that contacts the measurement area, specifically the area that overlaps with the electrode that detects the body movement, is 200 mm². 2 The above configuration is preferable because it ensures good adhesion to the measurement site and reduces measurement variability. Furthermore, the pressure applied to the measurement site of the biological body to which the photoplethysmography sensor is attached is set to 0.02 N / cm². 2 From (systolic blood pressure [N / cm²] 2 ]+0.4[N / cm 2 It is preferable to set the range to ]) in order to allow measurement without applying excessive pressure to the living body.

[0024] The present invention, its components, and embodiments for carrying out the present invention will be described below. In this application, "~" is used to mean that the numerical values ​​written before and after it are included as the lower limit and upper limit.

[0025] [Overview of the photoelectric volume pulse wave sensor of the present invention] The photoplethysmography sensor of the present invention is a photoplethysmography sensor comprising a light-emitting element and a light-receiving element, wherein the electrodes constituting the light-emitting element or the light-receiving element are surface electrodes, and at least one of these electrodes is used in combination as an electrode for detecting body movement.

[0026] In this invention, "surface electrode" refers to a flat, planar electrode. Furthermore, "body movement" refers to changes caused by the movement or vibration of the person being measured, and "body movement data" refers to the waveform data of electrical signals that capture these changes as waveforms. A "pulse wave" is a waveform representation of the volume change in blood vessels that occurs as the heart pumps blood, and "pulse wave data" refers to the waveform data of the electrical signal that captures the aforementioned volume change in blood vessels as a waveform. Furthermore, the photoplethysmography sensor of the present invention can be used in either a reflective or transmissive form. In the reflective type, light irradiated from a light-emitting element onto a living body is reflected within the living body and incident on a light-receiving element, where it is converted into photoelectricity to detect the pulse wave. In the transmissive type, light irradiated from a light-emitting element onto a living body is transmitted through the living body and incident on the light-receiving element, where it is converted into photoelectricity to detect the pulse wave. The following describes the configurations of reflective photoplethysmography sensors and transmissive photoplethysmography sensors, in that order.

[0027] [Reflective photoplethysmography sensor] Figure 1 is a cross-sectional view showing an example of the configuration of the reflective photoplethysmography sensor of the present invention, and Figure 2 is a cross-sectional view showing a detailed configuration of the reflective photoplethysmography sensor of Figure 1. As shown in Figure 1, a reflective photoplethysmography sensor (hereinafter also referred to as "reflective photoplethysmography sensor") 100A is attached to the measurement site of the biological body E. The measurement site of biological tissue E, although not shown in the diagram, consists of the epidermis, dermis, and subcutaneous tissue in that order from the surface. Capillaries flow between the epidermis and dermis, arterioles flow through the dermis and subcutaneous tissue, and arteries D flow below the arterioles. The reflective photoplethysmography sensor 100A preferably comprises a light-emitting element 500 and a light-receiving element 400, and further has a light-transmitting elastic dielectric layer 600. Specifically, the reflective photoplethysmography sensor 100A is arranged in the following order from the top surface of the measurement site of the biological tissue E: an elastic dielectric layer 600, a light-receiving element 400, and a light-emitting element 500. In this case, the measurement site could be, for example, a part of the body that cannot transmit light (such as the wrist). In Figure 1, the light-receiving element 400 is embedded approximately in the center of the elastic dielectric layer 600 in a plan view, but is not limited to this. Furthermore, the light-emitting element 500 is provided on the elastic dielectric layer 600 in which the light-receiving element 400 is embedded. Preferably, the size of the light-emitting element 500 and the elastic dielectric layer 600 in plan view is about the same, the size of the light-receiving element 400 in plan view is smaller than the size of the light-emitting element 500 in plan view, and preferably the size of the light-receiving element 400 is such that it fits inside the light-emitting element 500 in plan view. Furthermore, the light-emitting element 500, the light-receiving element 400, and the elastic dielectric layer 600 are housed within the housing 700. The plan view shape of the light-emitting element 500 and the light-receiving element 400 may be rectangular, circular, or any other shape.

[0028] Furthermore, in the reflective photoplethysmography sensor 100A equipped with a light-emitting element 500 and a light-receiving element 400, in Figure 2, reference numeral 50 denotes the light-emitting part and reference numeral 40 denotes the light-receiving part. Here, "light-emitting part 50" refers to the region inside the light-emitting element 500 that has a layer 50a that actually functions for light emission (light-emitting functional layer (specifically, electron injection layer 53, electron transport layer 54, light-emitting layer 55, hole transport layer 56, and hole injection layer 57 (see Figures 5A and 5B))) and electrodes (anode 58, cathode 52) that overlap with the layer, and is substantially incident into the living body. That is, in the light-receiving element 400, since the electrode on the light-emitting element 500 side (anode 42) is made of a light-reflecting material, the light emitted from the light-emitting element 500 passes through the parts other than the electrode 42 and is incident into the living body E, where it emits light. Furthermore, "light-receiving section 40" refers to the region inside the light-receiving element 400 that has a layer 40a (light-receiving functional layer) that actually functions for receiving light, and electrodes (anode 42 and cathode 46) that overlap with said layer. Details of the configuration of the light-emitting element 500 and the light-receiving element 400 (Figures 2, 5A, 5, 6A, and 6B) will be described later.

[0029] In this invention, at least one electrode (52, 58, 42, and 46) constituting the light-emitting element 500 or the light-receiving element 400 is used in combination as a motion detection electrode for detecting body movement. In particular, it is preferable to use the anode of the light-emitting element as a motion detection electrode. The motion detection electrode functions as a capacitive pressure sensor, using the body E as the other electrode, to detect the body movement of the person being measured. Specifically, an alternating current is passed through the motion detection electrode, and based on the value of the current flowing through the motion detection electrode, changes in capacitance between the motion detection electrode and the measurement site of the body are detected. When the contact area of ​​the photoplethysmography sensor with the measurement site changes, or when the pressure applied to the measurement site and the motion detection electrode changes, the capacitance between the motion detection electrode and the measurement site changes, and the changed capacitance information is output as motion data.

[0030] [Transmissive photoplethysmography sensor] Figure 3 is a cross-sectional view showing an example of the configuration of the transmissive photoplethysmography sensor of the present invention, and Figure 4 is a cross-sectional view showing a detailed configuration of the transmissive photoplethysmography sensor of Figure 3. As shown in Figure 3, a transmissive photoplethysmography sensor (also called a "transmissive photoplethysmography sensor") 100B is attached to the measurement site of biological tissue E. The transmissive photoplethysmography sensor 100B, like the reflective photoplethysmography sensor 100A described above, preferably comprises a light-emitting element 500 and a light-receiving element 400, and further preferably has a light-transmitting elastic dielectric layer 600. Specifically, the transmissive photoplethysmography sensor 100B has a light-emitting element 500 on the upper surface of the measurement site of a biological organism E via an elastic dielectric layer 600, and a light-receiving element 400 on the lower surface of the measurement site via an elastic dielectric layer 600. That is, the light-emitting element 500 and the light-receiving element 400 are arranged facing each other, and the measurement site of the biological organism E is positioned between these light-emitting element 500 and light-receiving element 400. Examples of measurement sites in this case include areas that can transmit light (such as fingertips or earlobes). In Figure 3, it is preferable that the size of the light-emitting element 500 and the light-receiving element 400 in a plan view is approximately the same, and at least, it is preferable that the light-receiving element 400 is small enough to fit inside the light-emitting element 500 in a plan view. Furthermore, the light-emitting element 500, the elastic dielectric layer 600, the light-receiving element 400, and the elastic dielectric layer 600 are housed within the housing 700. The plan view shape of the light-emitting element 500 and the light-receiving element 400 may be rectangular, circular, or any other shape. Details of the configuration of the light-emitting element 500 and the light-receiving element 400 (Figures 4, 5A, 5B, 6A, and 6B) will be described later.

[0031] Furthermore, in the transmissive photoplethysmography sensor 100B, at least one electrode (anode 42 and cathode 46) constituting the light-emitting element 500 or the light-receiving element 400 is also used as a motion detection electrode to detect body movement. In particular, it is preferable to use the anode of the light-emitting element as a motion detection electrode.

[0032] [Functions of the photoplethysmography sensor] The photoplethysmography sensor of the present invention irradiates the part of the biological tissue to be measured with light from a light-emitting element such as a light-emitting diode as a light source, and detects the light reflected or transmitted from the part of the biological tissue to be measured with a light-receiving element such as a photodiode as a light detection sensor, and measures changes such as the volume pulse wave of the biological tissue based on the detected signal. In particular, the photoplethysmography sensor of the present invention can detect body movement by using either the light-emitting element or the light-receiving element electrode as a body movement detection electrode, and by taking the difference between the pulse wave data obtained and the body movement data, it is possible to extract only the pulse wave data from which noise and other unwanted elements have been removed.

[0033] For example, light emitted from a light-emitting element penetrates the epidermis and reaches the blood vessels beneath it. The light that reaches the blood vessels is absorbed, reflected, or passes through the blood flowing through those vessels. Of this light, the light scattered by the vascular tissue and blood enters the photodetector. Therefore, the photodetector outputs a photocurrent corresponding to the amount of incident light. Here, blood vessels expand and contract in the same cycle as the heartbeat. Consequently, the amount of reflected light increases or decreases in the same cycle as the expansion and contraction of the blood vessels, so the change in the photocurrent output from the photodetector indicates a change in the volume of the blood vessels.

[0034] Furthermore, the photoplethysmography sensor of the present invention can also be used as a sensor to detect the oxygen saturation of arterial blood. Hemoglobin in the blood absorbs red light and infrared light differently depending on whether or not it is bound to oxygen. Therefore, by preparing multiple sets of elements with different emission and reception wavelengths, such as elements that emit and receive red light and elements that emit and receive infrared light, and then measuring and analyzing the reflected light from these sets, the oxygen saturation can be detected. By subtracting the aforementioned body movement data when detecting oxygen saturation in this way, a more accurate oxygen saturation can be detected. Furthermore, the blood vessels in question are arteries.

[0035] Furthermore, in this invention, "volume pulse wave" refers to the waveform that occurs when changes in pressure within a blood vessel due to pulsation cause changes in volume, and it allows for the direct assessment of changes in the blood vessel. Furthermore, "photoplethysmography" refers to a waveform detected by utilizing the transmission or reflection of light from the blood to detect volume pulse waves.

[0036] [Method for calculating oxygen saturation] Generally, a photoplethysmography sensor (pulse oximeter) is used to measure the oxygen saturation level in the blood. A pulse oximeter works by shining two wavelengths of light, ranging from red to near-infrared, onto the finger and measuring 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 transmitted through hemoglobin (Hb), the absorbance of red light by HHb is significantly higher than that of O2Hb, and it varies greatly depending on the wavelength of red light. Also, when near-infrared light is transmitted through hemoglobin (Hb), the absorbance of near-infrared light by HHb is slightly lower than that of O2Hb. Therefore, the ratio R (absorbance of red light / absorbance of near-infrared light) of hemoglobin to the absorbance of near-infrared light changes depending on the oxygen saturation, which is the ratio of O2Hb to O2Hb+HHb in the blood.

[0037] Furthermore, measurement sites such as fingers, wrists, back of arms, chest, and abdomen contain arterial blood, venous blood, tissue, and bone, which affect the absorbance of red light and near-infrared light. Of these, the portion to which the volume change of the vascular volume pulse wave contributes is arterial blood. The signals corresponding to absorbance detected by a photodetector can be broadly classified into two types: signals from the pulsation of arterial blood (also called the "pulsating component" or "AC") and signals absorbed by the non-pulsating portion of arterial blood, venous blood, biological tissue, bone, etc. (also called the "non-pulsating component" or "DC"). For example, if we assume that the pulsating component of the absorbance of red light with a wavelength of 660 nm is AC660 and the DC component is DC660, and for example, if we assume that the AC component of the absorbance of near-infrared light with a wavelength of 940 nm is AC940 and the DC component is DC940, then the ratio R (absorbance of red light / absorbance of near-infrared light) of the absorbance of red light to the absorbance of near-infrared light is expressed by the following equation (I).

number

[0038] Based on the R value calculated using equation (I) above and a calibration curve showing the relationship between the R value and transcutaneous arterial oxygen saturation (SpO2) obtained empirically beforehand, blood oxygen saturation can be determined.

[0039] Furthermore, when red light and near-infrared light are typically shone on the fingers, wrists (e.g., ulnar and radial sides), back of the arm, chest, etc., and absorbance is measured, the change in absorbance over time is measured as a waveform that reflects the pulse wave. Therefore, the AC component of absorbance can be identified by calculating the difference between the maximum and minimum values ​​of the change in absorbance over time, and the DC component of absorbance can be identified by calculating the average value of the change in absorbance over time. The perfusion index (PI), expressed by the following formula (1) using the pulsating component (AC) and non-pulsating component (DC) identified in this way, is preferably 0.5% or higher to minimize the influence of noise during measurement. In particular, for applications calculating oxygen saturation, a PI value of 1.0% or higher is more preferable. Formula (1): PI(%)=AC / DC×100

[0040] [Example of an overall configuration for a photoelectric pulse wave sensor] The overall configuration of a photoplethysmography sensor can take on various forms and configurations. For example, a preferred basic overall configuration includes: a light-emitting element that is driven to blink and emit light at a frequency higher than the frequency of the volume pulse wave of a living organism based on the signal of an oscillator; a light-receiving element that receives light emitted from the light-emitting element and light reflected or transmitted by the biological tissue to be measured, and generates a signal having a signal level corresponding to the amount of received light; an ambient light extraction means for extracting the ambient light signal component from the signal generated by the light-receiving element; a motion detection means for detecting the motion signal component due to body movement; a reduction means for reducing noise signals caused by ambient light and body movement in the signal generated by the light-receiving element by subtracting the ambient light signal component extracted by the ambient light extraction means and the motion detection signal component detected by the motion detection 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 organism to be measured based on the signal after the noise signal components caused by ambient light and body movement have been reduced by the reduction means.

[0041] [Components of a photoplethysmography sensor] This section describes the main components of a photoplethysmography sensor, namely the light-emitting element, the light-receiving element, and the elastic dielectric layer.

[0042] <hibi> In this invention, the light-emitting element is used as a light source for irradiating biological tissue. While both organic light-emitting diodes (OLEDs) and inorganic light-emitting diodes (LEDs) can be used as light-emitting elements, and are not particularly limited, it is preferable to use an organic electroluminescent diode (OLED, also called an "organic EL element" or "organic photodiode"), which is a light-emitting element composed of a planar organic layer, as it is flexible, comfortable to wear, and can reduce wavelength and brightness variations. In particular, a configuration is preferred in which a wavelength conversion filter that converts the visible light from the organic EL element to near-infrared light (IR) is placed on an organic EL element that emits red light. Alternatively, an LED and a light guide plate may be used as a planar light-emitting element. In display backlights, the LED is placed on the edge of the light guide plate, and light is incident from the side edge of the light guide plate. Furthermore, micro-LEDs may be used with a resolution sufficient to be considered a surface. To mitigate the localized increase in brightness directly above the LEDs, it is preferable to provide a scattering layer.

[0043] (Organic EL element) Figure 5A is a schematic plan view of an organic EL element, and Figure 5B is a schematic cross-sectional view showing an example of the configuration of an organic EL element.

[0044] Suitable organic EL elements 500 for the present invention include, for example, a configuration shown in Figures 2, 4, 5A, and 5B, in which an anode 58 and a cathode 52 are provided on a flexible resin substrate 51, and a group of light-emitting functional layers 50a (also called "organic functional layers" or "organic layers") including a light-emitting layer 55 are sandwiched between the anode 58 and cathode 52 at opposing positions. Furthermore, depending on the purpose, various functional layers such as a sealing member 59, a gas barrier layer (not shown), and a light extraction layer may be appropriately combined to form the configuration.

[0045] Typical configurations of the organic EL element according to the present invention are listed below, but the configurations of organic EL elements applicable to the present invention are not limited to these examples. Figure 5B is a cross-sectional view showing the case of configuration (7) below.

[0046] (1) Anode / Emitting layer / Cathode (2) Anode / Emitting layer / Electron transport layer / Cathode (3) Anode / Hole transport layer / Emitting layer / Cathode (4) Anode / Hole transport layer / Emitting layer / Electron transport layer / Cathode (5) Anode / Hole transport layer / Emitting layer / Electron transport layer / Electron injection layer / Cathode (6) Anode / Hole injection layer / Hole transport layer / Emitting layer / Electron transport layer / Cathode (7) Anode 58 / Hole injection layer 57 / Hole transport layer 56 / (Electron blocking layer / ) Emitting layer 55 / (Hole blocking layer / ) Electron transport layer 54 / Electron injection layer 53 / Cathode 52 In Figure 5A, reference numeral 501 denotes the extraction electrode.

[0047] In an organic light-emitting diode (OLED) device, an external electric field is applied, causing holes to be injected from the anode into the hole transport layer and electrons to be injected from the cathode into the electron transport layer. The injected carriers hop between molecules. In the light-emitting layer, the holes and electrons recombine to generate electrically neutral excitons. The excitons radiate and deactivate, emitting light according to their emission quantum efficiency. The light generated in the organic layer is extracted into the air through a light extraction surface.

[0048] There are no particular limitations on the specific details of each constituent layer that make up the organic EL element applicable to the present invention, nor on the manufacturing method thereof; known constituent materials and manufacturing methods can be applied. For example, the contents described in Japanese Patent Publication No. 2013-089608, Japanese Patent Publication No. 2014-120334, Japanese Patent Publication No. 2015-201508, International Publication No. 2018 / 51617, etc., can be referred to.

[0049] (Wavelength conversion filter) The organic EL element according to the present invention is preferably provided with a wavelength conversion filter that converts the visible light of the organic EL element into near-infrared light.

[0050] In the wavelength conversion filter according to the present invention, it is preferable to include a light-emitting material (for example, a light-emitting dye) that has wavelength conversion ability. As long as the wavelength conversion filter according to the present invention contains a light-emitting dye that has wavelength conversion ability, there are no particular restrictions on its form or manufacturing method, and it can be appropriately determined according to the intended use.

[0051] The wavelength conversion filter according to the present invention preferably has the function of absorbing light from an organic EL element that emits light in the visible light region including the near-infrared region (380 to 780 nm), preferably in the green to red region including the near-infrared region (495 to 750 nm), and particularly preferably in the red region (600 to 700 nm), and converting it into near-infrared light, for example, near-infrared light that emits light in the region above 700 nm and below 1500 nm, and further having an emission maximum around 850 nm.

[0052] The wavelength conversion filter and the organic EL element may be manufactured separately and then bonded together, or the wavelength conversion filter may be directly coated onto the organic EL element and then laminated. Additionally, a cut filter may be laminated or included as needed to filter out light that has been emitted without wavelength conversion.

[0053] 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.

[0054] The wavelength conversion filter according to the present invention may, if necessary, contain various well-known additives in addition to the luminescent dye, such as colorants, light stabilizers, antioxidants, surfactants, flame retardants, inorganic additives, clearing agents, ultraviolet absorbers, fillers, and light scattering particles.

[0055] <Photodetector> The light-receiving element according to the present invention functions as a sensor that detects light reflected by biological tissue from light-emitting elements and converts it into electricity. As the light-receiving element, a planar inorganic or organic photodiode (OPD) or organic thin-film solar cell (OPV) can be used. In particular, the use of an OPD is preferred because it is flexible, comfortable to wear, and can reduce wavelength and brightness variations.

[0056] (1) Organic photodiode As the light-receiving element according to the present invention, a conventionally known organic photodiode (also called "OPD" or "organic PD") can be used. Figures 6A and 6B are schematic diagrams of an organic photodiode, with Figure 6A being a plan view and Figure 6B being a cross view showing an example of its configuration. For example, as shown in Figures 2, 4, 6A, and 6B, the organic photodiode 400 has a structure in which a cathode 46 made of metal formed on a light-transmitting substrate 41 such as resin or glass by sputtering or resistance heating deposition, and a light-receiving functional layer 40a formed on the cathode 46 by resistance heating deposition, and further, an anode 42 made of a transparent conductive film such as ITO (Indium-Tin Oxide) formed on the light-receiving functional layer 40a by resistance heating deposition, etc. These are the basic components. Furthermore, depending on the purpose, various functional layers such as the sealing member 47 may be appropriately combined to form the structure. Also, in Figure 6A, reference numeral 401 represents the extraction electrode.

[0057] When light is shone onto an organic photodiode with this configuration, light absorption occurs in the photoelectric conversion region, and excitons are formed. Subsequently, the carriers are separated, and electrons move to the cathode through the photodetector layer, while holes move to the anode through the photodetector layer. This generates an electromotive force between the two electrodes, and by connecting an external circuit, it becomes possible to extract an electrical signal.

[0058] The light-receiving functional layer can consist of a single layer or multiple layers. The light-receiving functional layer can 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.

[0059] For example, a structure having the details shown in Figure 13D of U.S. Patent Publication 2017 / 0156651 can be used. Furthermore, for information on various organic materials used in organic photodiodes, please refer to Japanese Patent Publication No. 2017-532546, Japanese Patent Application Publication No. 2006-261172, and Nature Electronics volume 3, pages 113-121 (2020).

[0060] (2) Organic thin film solar cells As the light-receiving element according to the present invention, various forms of conventionally known organic thin-film solar cells (OPVs) can also be used. For example, a bulk heterojunction type organic photoelectric conversion element can be used, which has a basic configuration in which a transparent electrode anode, a hole transport layer, a bulk heterojunction photoelectric conversion layer, an electron transport layer, and a cathode are sequentially stacked on one side of a substrate. Furthermore, it may also have other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer.

[0061] The photoelectric conversion layer is a layer that converts light energy into electrical energy, and is composed of a bulk heterojunction layer in which p-type semiconductor material and n-type semiconductor material are uniformly mixed. p-type semiconductor materials function relatively as electron donors, while n-type semiconductor materials function relatively as electron acceptors. Here, electron donors and electron acceptors are defined as "electron donors and electron acceptors that, upon absorbing light, transfer electrons from the electron donor to the electron acceptor, forming a hole-electron pair (charge-separated state)." They do not simply donate or accept electrons like electrodes, but rather donate or accept electrons through a photoreaction.

[0062] Furthermore, in order to further improve the solar energy utilization rate (photoelectric conversion efficiency), a tandem configuration (a configuration having multiple bulk heterojunction layers) in which such photoelectric conversion elements are stacked may also be used.

[0063] Examples of p-type semiconductor materials include various condensed polycyclic aromatic compounds and conjugated compounds. Examples of n-type semiconductor materials include fullerenes, octa-azaporphyrins, perfluoro derivatives of p-type semiconductors, and polymer compounds containing aromatic carboxylic acid anhydrides or their imidides as a backbone, such as naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic diimide, perylenetetracarboxylic anhydride, and perylenetetracarboxylic diimide.

[0064] <Elastic dielectric layer> The elastic dielectric layer functions as a capacitor in a capacitive pressure sensor where at least one electrode (motion detection electrode) among the electrodes constituting the light-emitting or light-receiving element is used, and the measurement site of a living organism is used as the other electrode.

[0065] Figures 7A to 7C are schematic cross-sectional views of a reflective photoplethysmography sensor attached to the measurement site. Note that the symbols in Figures 7A to 7C have the same meaning as those in Figure 2, so their explanation is omitted. Here, when viewed from above, if S is the contact area of ​​the elastic dielectric layer 600 that contacts the measurement area and overlaps with the motion detection electrode, then as is clear from the following formula, the capacitance C increases as the contact area S increases. Also, if the thickness of the elastic dielectric layer 600 is d, the capacitance C increases as the thickness d of the elastic dielectric layer 600 decreases due to pressure. C = ε·S / d [ε: Permittivity of space (F / m), d: Thickness (distance) of the elastic dielectric layer (m), S: Contact area (m) of the elastic dielectric layer that contacts the measurement site when viewed from above, where it overlaps with the motion detection electrode. 2 )]

[0066] In the above formula, "the contact area S of the elastic dielectric layer that contacts the measurement site when viewed from above, which overlaps with the motion detection electrode" refers to the area portion S of the contact area M of the elastic dielectric layer 600 that contacts the measurement site, which overlaps with the motion detection electrode (for example, the anode 58 of the light-emitting element 500) when viewed from above, as shown in Figure 7A. Also, in the cases of Figures 7B and 7C, if the motion detection electrode is the anode 58 of the light-emitting element 500, the area portion of the elastic dielectric layer 600 represented by the symbol S is considered the contact area S. On the other hand, in the case of the transmissive photoplethysmography sensor shown in Figure 4, S refers to the area portion corresponding to the overlapping location of the elastic dielectric layer 600 and the motion detection electrode (for example, the anode 58 of the light-emitting element 500) when viewed from above. In the above explanation, the case in which the motion detection electrode is the anode 58 of the light-emitting element 500 was described. However, if the motion detection electrode is the cathode 52 of the light-emitting element 500, or the anode 42 or cathode 46 of the light-receiving element 400, the contact area S is defined as the area corresponding to the overlapping portion of the elastic dielectric layer 600 and each electrode. Furthermore, in the above formula, "thickness d of the elastic dielectric layer" refers to the distance from the surface of the elastic dielectric layer 600 that contacts the measurement site to the surface of the elastic dielectric layer 600 that contacts the substrate 41 (the part indicated by the symbol d in Figures 7A to 7C). In Figure 2, it also refers to the part indicated by the symbol d. Furthermore, in the case of the transmissive photoplethysmography sensor shown in Figure 4, if the motion detection electrode is the electrode of the light-emitting element 500 (anode 58 or cathode 52), the thickness of the elastic dielectric layer 600 on the light-emitting element side is set to "thickness d of the elastic dielectric layer" in the above formula. If the motion detection electrode is the electrode of the light-receiving element 400 (anode 42 or cathode 46), the thickness of the elastic dielectric layer 600 on the light-receiving element side is set to "thickness d of the elastic dielectric layer" in the above formula.

[0067] In Figure 7A, the entire surface of the elastic dielectric layer 600 is in contact with the measurement site, there is no poor adhesion, and no pressure is being applied. In FIG. 7B, compared with the elastic dielectric layer 600 in FIG. 7A, the contact area with respect to the measurement site is small, and there is poor adhesion. Also, it is in a state where no pressure is applied. Therefore, due to the poor adhesion, external light irradiates the living body, and since the area S becomes small and reflects from the skin surface, the pulsation component (AC) in the pulse wave data is less likely to increase. That is, the non-pulsation component (DC) increases and the capacitance decreases. In FIG. 7C, by applying pressure from the state of FIG. 7A, the thickness d1 of the elastic dielectric layer 600 and the thickness d2 of the biological tissue up to the artery D become thinner. Therefore, the absorption of light by the living body decreases and the capacitance increases.

[0068] As described above, the elastic dielectric layer 600 and the body motion detection electrode can detect the adhesion and pressure to the measurement site from the change in the capacitance C. Here, the contact area S is preferably 200 mm 2 or more, and more preferably within the range of 200 to 600 mm 2 Also, the pressure applied to the measurement site of the living body is preferably 0.02 N / cm 2 or more, and more preferably 3 N / cm 2 or less. Note that the pressure applied to the measurement site of the living body can be controlled, for example, by changing the thickness d of the elastic dielectric layer 600. Specifically, the thickness d is preferably within the range of 0.1 to 1 mm.

[0069] As the elastic dielectric layer 600, materials mainly used in flexible substrates for organic EL elements or soft, transparent resins can be used. Examples include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose esters such as cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate (CAP), cellulose acetate phthalate, and cellulose nitrate, or their derivatives, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide, polyethersulfone (PES), polyphenylene sulfide, polysulfones, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, silicone resin, polyurethane, polymethyl methacrylate, acrylic, or polyarylates, and cycloolefin resins such as Arton (trade name manufactured by JSR) or Apel (trade name manufactured by Mitsui Chemicals). Silicone resin and polyurethane are preferred.

[0070] [Biometric Information Measurement Device] The photoplethysmography sensor of the present invention can be applied to various forms of biological information measurement devices depending on the purpose. Examples of application will be explained below.

[0071] Figure 8 is a perspective view of a biometric information measurement device using a reflective photoplethysmography sensor that can be wrapped 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 is equipped with a belt 20, which allows it to be worn on the patient's wrist. A detection unit 14, which includes the aforementioned light-emitting element 500, light-receiving element 400, elastic dielectric layer 600, etc., is arranged inside the belt 20, and the detection unit 14 and the main body 10 are electrically connected.

[0072] The main body 10 is formed in a flat shape, and the operation unit 12 and display unit 15 are provided on its circumferential surface and surface. Inside, electrical circuits and the like that perform functions equivalent to the control unit 11 and recording unit 13 (see Figure 9) are housed.

[0073] The operating unit 12 is configured to include, for example, a power switch 12a, a timing switch (operating switch) 12b, and the like.

[0074] Figure 9 shows an example of the functional configuration of the biological information measuring device 1. As shown in Figure 9, the biological information measuring device 1 is composed of 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, a power supply unit 18, and the like.

[0075] The control unit 11 includes a CPU (Central Processing Unit) and RAM (Random Access Memory). It is composed of the following: The CPU of the control unit 11 reads various programs such as system programs and processing programs recorded in the recording unit 13, loads them into RAM, and executes various processes according to the loaded programs. The control unit 11 performs pulse wave detection processing as described later (see Figure 10). Specifically, it optimizes and takes the difference between pulse wave data obtained when light irradiated into the body from the light-emitting element 500 is reflected within the body and incident on the photodetector 400, and body motion data obtained from the body motion detection electrode and capacitance changes at the measurement site. Furthermore, the control unit 11, when the pulsating component of the signal corresponding to the absorbance of light detected by the photodetector 400 is defined as AC and the non-pulsating portion as DC, displays an error if the perfusion index (PI) represented by formula (1) is less than 0.5%, and determines that it is normal and performs measurement if it is 0.5% or more.

[0076] The operation unit 12 is a detection unit that detects the operator's instructions and is equipped with various switches, various function buttons, etc., and outputs these operation signals to the control unit 11.

[0077] The recording unit 13 is composed of a semiconductor non-volatile memory or the like. The recording unit 13 stores system programs and various programs necessary for operating the biological information measuring device 1 in this embodiment, as well as parameters and files necessary for executing those programs. For example, the recording unit 13 continuously records the vital data being measured from the start to the end of the measurement. Alternatively, vital data may be recorded at regular intervals from the start to the end of the measurement.

[0078] The detection unit 14 is a data acquisition unit that acquires patient vital data by applying the photoplethysmography sensor 100A or 100B of the present invention (see Figures 2, 4, etc.), and preferably comprises a light-emitting element 500 and a light-receiving element 400 as described above, and further comprises an elastic dielectric layer 600, and is configured to be attachable to a measurement site such as the wrist. In this case, the photoplethysmography sensor is of the reflective type, but it may also be of the transmissive type. The detection unit 14 controls the light-emitting element drive circuit 14b via the measurement control unit 14a, causing the light-emitting element 500 in the detection unit 14 to emit red light and infrared light toward the biological site. The analog signal of the reflected light from the measurement site, received by the light-receiving element 400 in the detection unit 14, is sent to the analog front-end circuit 14c. The detection unit 14 also controls the body motion detection electrode control circuit 14e via the measurement control unit 14a, causing current to flow through at least one electrode (body motion detection electrode) that constitutes the light-emitting element 500 or the light-receiving element 400 in the detection unit 14, and the analog signal of body motion detected by the body motion detection electrode is sent to the analog front-end circuit 14c. Based on the analog signals of reflected light and body motion, noise reduction and signal amplification are performed to prepare a voltage signal for input to the AD converter 14d, which then converts it into digital data.

[0079] After being converted to digital data by the AD converter 14d, the control unit 11 calculates vital data such as SpO2, pulse rate, and arteriosclerosis based on this digital data. The calculated vital data is recorded in the recording unit 13.

[0080] The display unit 15 is configured with, for example, an LCD (Liquid Crystal Display) and displays information using, for example, a dot matrix method, and displays information according to the instructions of the display signals input from the control unit 11.

[0081] The wireless communication unit 16 has a wireless interface for transmitting and receiving data with the information processing device 3 via wireless communication such as Bluetooth® or Wi-Fi®.

[0082] The power supply unit 18 supplies the power required for the operation of each part of the biological information measuring device 1 to each part. The power supply unit 18 supplies power output from a battery (not shown) at the operating voltage of each part.

[0083] Next, an example of processing performed by the control unit 11 in the biological information measuring device 1 configured as described above will be explained below with reference to Figure 10. Figure 10 is a flowchart of an example of pulse wave detection processing. Figure 11 is a diagram showing the driving method for the light-emitting element, light-receiving element and body motion detection electrode. First, the control unit 11 drives the light-emitting element 500 and the light-receiving element 400 to measure the pulse wave (PPG) (see step S1, step (a) in Figure 11). That is, light irradiated into the body from the light-emitting element 500 is reflected within the body and incident on the light-receiving element 400, thereby obtaining pulse wave data. Furthermore, after driving the light-emitting element 500 and the photodetector 400 to obtain pulse wave data, only the photodetector 400 is driven. As a result, the light-emitting element 500 is not driven, and only ambient light is received and measured by the photodetector 400 (see step (b) in Figure 11).

[0084] Next, body movement is measured (see step S2, step (c) in Figure 11). That is, body movement data is obtained by measuring the change in capacitance at the body movement detection electrode and the measurement site.

[0085] Then, it is determined whether the required number of pulse wave data and body movement data has been obtained (step S3). If it is determined that the required number of samples has not been obtained (step S3; NO), the steps (a) to (c) in Figure 11 are repeated, with each cycle consisting of steps (a) to (c) until the required number of samples is obtained (steps S1 and S2). Furthermore, the periods between steps (a) and (b) in Figure 11, and between steps (b) and (c), are designated as periods to avoid the effects of charge and discharge due to transient phenomena.

[0086] If it is determined that the required number of samples has been obtained (Step S3; YES), the following signal processing is performed (Step S4). Specifically, the process involves subtracting ambient light data obtained by receiving only ambient light with a photodetector in step 11(b) from the pulse wave data obtained in step 11(a) as described above (ambient light removal process). Furthermore, preprocessing is performed using image processing filters such as bandpass filters and moving average filters to remove electrical noise, and to equalize the signal strength of the pulse wave data obtained optically and the body motion data obtained capacitively. Finally, the difference between the preprocessed pulse wave data and the body motion data is taken. This results in accurate pulse wave data with the body motion data removed.

[0087] Next, in order to output more reliable pulse wave data, the pulsating component of the signal corresponding to the absorbance of light detected by the photodetector 400 is defined as AC, and the non-pulsating portion is defined as DC. AC and DC are then calculated, and the perfusion index (PI = AC / DC) is calculated (Step S5). Then, it is determined whether the PI is 0.5% or greater (step S6). If it is less than 0.5% (step S6; NO), an error is displayed, and the PPG measurement is performed again (step S1). If it is 0.5% or greater (step S6; YES), it is determined to be normal and the measurement is terminated.

[0088] (Configuration of a bio-information processing device) The information processing device 3 is a device capable of analyzing vital data transmitted from the biological information measurement device 1. The information processing device 3 can be, for example, a smartphone, tablet, or PC (Personal Computer), but is not particularly limited.

[0089] Figure 12 shows an example of the functional configuration of the information processing device 3. As shown in Figure 12, the information processing device 3 is configured to include, 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.

[0090] The control unit 31 is composed of a CPU, RAM, etc. The CPU of the control unit 31 reads various programs such as system programs and processing programs recorded in the recording unit 33, loads them into RAM, and executes various processes according to the loaded programs. Specifically, the control unit 31 performs processing to analyze vital data obtained based on light emitted from the light-emitting element 500 in the biological information measuring device 1.

[0091] The operation unit 32 is equipped with various switches, various function buttons, and a touch panel, and outputs the operation signals from these to the control unit 31.

[0092] The recording unit 33 is composed of semiconductor non-volatile memory, etc. The recording unit 33 stores system programs, various programs, parameters and files necessary for the execution of those programs, etc. For example, the recording unit 33 records vital data output from the biological information measuring device 1.

[0093] The display unit 34 is configured with a monitor such as a CRT (Cathode Ray Tube) or an LCD (Liquid Crystal Display), and displays various screens according to the instructions of the display signals input from the control unit 31.

[0094] The communication unit 35 communicates with a biological information measuring device via wireless communication such as Bluetooth or Wi-Fi. It has an interface for sending and receiving data with 1. The communication unit 35 may have a wired interface such as USB. [Examples]

[0095] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, the operations were carried out at room temperature (25°C).

[0096] [Example 1: Capacitance change due to body motion sensor] A reflective photoplethysmography sensor was prepared using the configuration shown in Figure 2, employing an organic EL element "A9F4C0A (manufactured by Konica Minolta)" as the light-emitting element, a silicon photodiode "KPD30S (manufactured by Kyoto Semiconductor)" as the light-receiving element, and connecting the anode of the organic EL element to an "Arduino Uno R3" as a motion detection electrode, with silicon resin used as the elastic dielectric layer. The area of ​​the motion detection electrode (anode of the organic EL element) in a plan view was 15.25 mm × 15.6 mm. The measurement site was the wrist (radial artery position). The light-emitting element was not illuminated, and current was passed through the motion detection electrode. Capacitance was measured under the following conditions (1) to (6), and the results are shown in Figure 14. Note that the capacitance value is automatically converted to an arbitrary signal intensity and displayed. Figure 13 is a plan cross-sectional view showing the motion detection electrode and substrate.

[0097] Condition (1): The elastic dielectric layer is not in contact with the measurement site (non-contact), and no pressure is applied. Condition (2): The elastic dielectric layer corresponding to 1 / 4 of the area of ​​the motion detection electrode (see Figure 13) is in contact with the measurement site, without pressurization. Condition (3): The elastic dielectric layer corresponding to half the area of ​​the motion detection electrode (see Figure 13) is in contact with the measurement site, without pressurization. Condition (4): An elastic dielectric layer corresponding to an area equivalent to (1x) the area of ​​the motion detection electrode (see Figure 13) is in contact with the measurement site, without pressurization. Condition (5): An elastic dielectric layer corresponding to an area equivalent to (1x) the area of ​​the motion detection electrode (see Figure 13) is brought into contact with the measurement site, and the wrist is bent backward. Condition (6): An elastic dielectric layer corresponding to an area equivalent to (1x) the area of ​​the motion detection electrode (see Figure 13) is brought into contact with the measurement site, the wrist is bent backward, and external pressure is applied with the fingers.

[0098] As shown in Figure 14, the results indicate that the signal strength increases from the non-contact case (condition (1)) to the case where the motion detection electrode is brought into contact with the measurement site, and the signal strength increases as the contact area increases (conditions (2) to (4)). Furthermore, it can be seen that the signal strength increases even more when pressure is applied (conditions (5) and (6)).

[0099] [Example 2: Changes in pulse wave due to pressure] A reflective photoplethysmography sensor, similar to the one used in Example 1, was prepared. The measurement site was the wrist (radial artery position), and the pulse wave was measured using the reflective photoplethysmography sensor while the wrist was alternately held straight and then bent backward. The results are shown in Figure 15. Figure 15B shows a detailed view of part b of Figure 15A, and Figure 15C shows a detailed view of part c of Figure 15A.

[0100] As shown in Figure 15, the pulse wave signal can be clearly measured when pressurized compared to when no pressurization is performed.

[0101] Figure 16 shows the pulse wave data and body movement data shown in Figure 15. In the waveforms of Figure 16, the data shown by dashed lines is pulse wave data, and the data shown by solid lines is body movement data. As shown in Figure 16, the capacitance increases when pressure is applied, and the capacitance when the reflective photoplethysmography sensor is in close contact with the measurement site was used as a threshold. If the capacitance is above the threshold, it was determined that the measurement was normal. Then, preprocessing such as the ambient light removal process and smoothing process described above was performed on the obtained pulse wave data, and the difference between the preprocessed pulse wave data and the body movement data was taken. Furthermore, AC / DC was calculated from the pulse wave data, and it was determined whether AC / DC was 0.5% or more. If it was 0.5% or more, it was measured as a normal pulse wave. By using at least one electrode among the electrodes constituting the light-emitting or light-receiving element as an electrode for detecting body movement, the number of parts can be reduced, costs can be lowered, and body movement and pulse waves can be detected more accurately. [Industrial applicability]

[0102] The present invention can be particularly used in a photoplethysmography sensor and a pulse wave detection method that have fewer parts, reduce costs, and can detect body movement and pulse waves more accurately. [Explanation of Symbols]

[0103] 1. Biological Information Measurement Device 14 Detection unit 40 Light receiving part 40a Light-receiving layer 42 Anode 46 Cathode 50 Light-emitting part 50a Light-emitting functional layer 52 Cathode 58 Anode 100A Reflective Photoplethysmography Sensor 100B Transmissive Photoplethysmography Sensor 400 light-receiving elements 500 light-emitting elements 600 Elastic dielectric layer 700 cabinets D Artery E Living organisms d. Thickness of the elastic dielectric layer S Contact area

Claims

1. A photoplethysmography sensor comprising a light-emitting element and a light-receiving element, The electrodes constituting the light-emitting element or the light-receiving element are surface electrodes, and the anode of the light-emitting element is used in combination as an electrode for detecting body movement. When measuring pulse waves, light emitted from the light-emitting element onto the living body is transmitted through or reflected within the living body and enters the light-receiving element, where it is converted into photoelectric energy to detect changes in the volume pulse wave. When detecting the aforementioned body movement, the change in capacitance between the electrode that detects the body movement and the living body is detected. A photoplethysmography sensor that alternately measures the pulse wave and the body movement at a frequency higher than the frequency of the pulse wave.

2. When the aforementioned photoplethysmography sensor is attached to a measurement site in a living body, it includes a light-transmitting elastic dielectric layer that comes into contact with the measurement site. The photoplethysmography sensor according to claim 1, wherein an electrode for detecting body movement is provided on the upper surface of the measurement area via the elastic dielectric layer.

3. A method for detecting pulse waves using a photoplethysmography sensor according to claim 1 or claim 2, The electrodes constituting the light-emitting element or the light-receiving element are made into surface electrodes, and body movement is also detected by using the anode of the light-emitting element among these electrodes. A method for detecting pulse waves by optimizing pulse wave data obtained using the aforementioned photoplethysmography sensor and body movement data, and then taking the difference between them.

4. The pulse wave detection method according to claim 3, wherein when the pulsating component of the signal corresponding to the absorbance of light detected by the light-receiving element is defined as AC and the non-pulsating component as DC, an error is displayed when the perfusion index (PI) represented by the following formula (1) is less than 0.5%, and it is determined to be normal when it is 0.5% or more, and the measurement is taken accordingly. Formula (1): PI (%) = AC / DC x 100

5. When the aforementioned photoplethysmography sensor is attached to a measurement site in a living body, a light-transmitting elastic dielectric layer is provided that comes into contact with the measurement site. A method for detecting pulse waves according to claim 3 or 4, wherein an electrode for detecting body movement is provided on the upper surface of the measurement area via the elastic dielectric layer, and the pulse wave and body movement are detected.

6. When viewed from above, the contact area of ​​the elastic dielectric layer that contacts the measurement area, specifically the area that overlaps with the electrode that detects the body movement, is 200 mm². ２ The pulse wave detection method according to claim 5, wherein the above is true.

7. The pressure applied to the measurement site of the living body to which the aforementioned photoplethysmography sensor is attached is set to 0.02 N / cm². ２ The pulse wave detection method according to any one of claims 3 to 6.

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