JP7777459B2 - Stretchable food freshness sensor module, food packaging wrap and food container equipped with the same - Google Patents

Description

The present invention relates to an expandable food freshness sensor module, and a food packaging wrap and food container equipped with the same.

Food waste has been highlighted in the SDGs (Sustainable Development Goals) and is attracting growing attention worldwide.

A food freshness label is known that can detect amines produced when fresh food spoils, and confirm the freshness or state of spoilage of the food (Patent Document 1).

Patent No. 6621624 Japanese Patent Application Laid-Open No. 2020-165958 International Publication No. 2013/182542

The food freshness label in Patent Document 1 allows consumers to easily know whether or not fresh food is edible. However, it is difficult for retailers and distributors that handle fresh food to manage the freshness or spoilage state of each individual fresh food item.

The present invention was made in consideration of the above circumstances, and provides a stretchable food freshness sensor module that can measure and manage the freshness or state of spoilage of individual fresh foods and can be easily attached and detached from fresh food packaging wrap or containers, as well as food packaging wrap and food containers equipped with the same.

To solve the above problems, the present invention provides the following means.

The stretchable food freshness sensor module according to the first aspect of the present invention comprises a stretchable resin substrate, a food freshness sensor capable of detecting the freshness of food, a wireless communication unit that transmits freshness information data detected by the food freshness sensor to the outside, and a battery that supplies power to the food freshness sensor and the wireless communication unit, and the food freshness sensor, the wireless communication unit, and the battery are disposed directly or indirectly on the stretchable resin substrate.

In the stretchable food freshness sensor module according to the above aspect, the stretchable resin substrate may have a breaking elongation of 13% or more.

The stretchable food freshness sensor module according to the above aspect may include two or more types of food freshness sensors.

In the stretchable food freshness sensor module according to the above aspect, the two or more types of food freshness sensors may be able to detect two or more types of gas components emitted from food.

In the stretchable food freshness sensor module according to the above aspect, the two or more gas components may be selected from the group consisting of ammonia, diethylamine, trimethylamine, ethylene, alcohol, lower fatty acids, aldehydes, hydrogen sulfide, hydrogen ions, methane, and carbon dioxide.

In the stretchable food freshness sensor module according to the above aspect, the battery may be a solar cell.

In the stretchable food freshness sensor module according to the above aspect, the electrode wiring connecting the functional devices of the food freshness sensor, the wireless communication unit, and the battery may have a breaking elongation rate of 40% or more.

The food packaging wrap according to the second aspect of the present invention is provided with the stretchable food freshness sensor module according to the above aspect adhered to it.

A food container according to a third aspect of the present invention has an opening, and the stretchable food freshness sensor module covers the opening and is positioned facing the food.

The stretchable food freshness sensor module of the present invention can measure and manage the freshness or state of spoilage of individual fresh foods, and can provide a stretchable food freshness sensor module that can be easily attached and detached from the packaging wrap or container of fresh foods.

1 is a plan view showing a schematic configuration of an expandable food freshness sensor module according to an embodiment of the present invention. FIG. FIG. 1 is a functional block diagram showing the schematic configuration of essential components of an expandable food freshness sensor module according to this embodiment. 1. FIG. 4 is a schematic plan view showing the general configuration of a modified example of the stretchable food freshness sensor module shown in FIG. FIG. 4 is a functional block diagram of the extendable food freshness sensor module shown in FIG. 3. 2 is a plan view of an example of the configuration of a solar cell in the stretchable food freshness sensor module shown in FIG. 1 . FIG. FIG. 6 is an exploded cross-sectional view schematically illustrating a cross section taken along line I-I' in FIG. 5, with the solar cell, the stretchable resin substrate, and the stretchable electrode disassembled. FIG. 6 is a schematic plan view showing a state in which solar cells are removed from the solar cell module 40 shown in FIG. 5 . 1. FIG. 4 is a plan view schematically illustrating another example of the configuration of the solar cell module in the stretchable food freshness sensor module shown in FIG. 1. FIG. 11 is a plan view schematically illustrating yet another example of the configuration of the solar cell module in the stretchable food freshness sensor module shown in FIG. 10 is a diagram for explaining the breaking elongation required for the stretchable food freshness sensor module. FIG. FIG. 2 is an exploded cross-sectional view showing a solar cell, a stretchable conductive adhesive, a stretchable resin substrate, and a stretchable electrode in an exploded manner. These are figures for explaining the action and effect of the stretchable food freshness sensor module of this embodiment, where (a) is a schematic diagram of the stretchable food freshness sensor module 10 of this embodiment, and (b) is a figure for explaining the principle. FIG. 10 is a diagram for explaining the effects. 1A and 1B are conceptual diagrams of a food packaging wrap to which the stretchable food freshness sensor module of this embodiment is adhered, where (a) is a longitudinal cross-sectional view and (b) is a plan view. 1A and 1B are conceptual diagrams of a food container to which the stretchable food freshness sensor module of this embodiment is adhered, where FIG. 1A is a longitudinal cross-sectional view and FIG. 1B is a plan view.

The present invention will now be described in detail, with appropriate reference to the drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual proportions. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them. Appropriate modifications can be made within the scope of the present invention's effectiveness.

(Stretchable food freshness sensor module)
Fig. 1 is a plan view showing the general configuration of a stretchable food freshness sensor module according to this embodiment. Fig. 2 is a functional block diagram showing the general configuration of essential components of the stretchable food freshness sensor module according to this embodiment. Fig. 3 is a plan view showing the general configuration of a modified example of the stretchable food freshness sensor module shown in Fig. 1. Fig. 4 is a functional block diagram of the stretchable food freshness sensor module shown in Fig. 3.

The stretchable food freshness sensor module 100 shown in Figure 1 comprises a stretchable resin substrate 10, a food freshness sensor 20 capable of detecting the freshness of food, a wireless communication unit 30 that transmits freshness information data detected by the food freshness sensor 20 to an external device 200, and a battery 40 that supplies power to the food freshness sensor 20 and the wireless communication unit 30, and the food freshness sensor 20, the wireless communication unit 30 and the battery 40 are arranged on the stretchable resin substrate 10.
In addition to the above essential components, the stretchable food freshness sensor module 100 further includes a sensor 21 other than the food freshness sensor 20 on the stretchable resin substrate 10 .
The stretchable food freshness sensor module 100 may further include a power storage unit 50 as shown in FIG.

The stretchable food freshness sensor module 100 enables retailers and distributors that handle fresh food to manage the freshness or spoilage state of each fresh food item. It also makes it possible to grasp the freshness or spoilage state of each fresh food item in real time.

The stretchable food freshness sensor module 100 is a stretchable electronic component that includes functional devices such as a food freshness sensor 20, a wireless communication unit 30, and a battery 40 mounted on a stretchable resin substrate 10. Therefore, it can be attached to wrapping film or food containers (food packages) by providing an adhesive layer as needed.
As will be described in detail later, the degree of stretchability can be increased by adjusting the arrangement of the functional devices, resulting in a stretchable sheet with greater flexibility in stretching.

<Food freshness sensor>
The food freshness sensor 20 can detect the freshness of food.
In this specification, "food freshness" refers to the freshness (liveliness) and degree of spoilage of fresh foods such as vegetables, fish, and meat, and can be evaluated directly or indirectly by measuring the amounts of ammonia, diethylamine, trimethylamine, ethylene, alcohol, lower fatty acids, aldehydes, hydrogen sulfide, hydrogen ions, methane, carbon dioxide, humidity, etc., and using these amounts as evaluation indicators.

The food freshness sensor 20 may be a gas sensor, a pH sensor, a biosensor (antigen-antibody, enzyme), an image sensor, a temperature sensor, an ultrasonic sensor, a visible UV sensor, or the like.
Two or more types of food freshness sensors operating under different principles may be provided as the food freshness sensor 20. Also, the food freshness sensor 20 may include a plurality of food freshness sensors operating under the same principle.

When an ammonia sensor that detects ammonia is used as the food freshness sensor 20, the sensor is represented by the following general formula (1):
M1 _x Fe _y (pyrazine) _s [Ni _1-t M2 _t (CN) ₄ ].zH ₂ O ... (1)
(M1=Co, Cu; 0.6≦x≦1.05; 0≦y≦0.4; 0≦s≦1; M2=Pd, Pt; 0≦t<0.15; 0≦z≦6)
An ammonia detector using a metal complex represented by the formula (1) as an ammonia detecting material may be used (see Patent Document 2). Prior art materials for detecting ammonia gas also detect gases such as alcohol and acetone, making it impossible to selectively detect ammonia gas. However, by using the ammonia detecting material represented by the formula (1), it becomes possible to selectively detect ammonia, for example, by utilizing the color change from pink to yellow. By using the metal complex represented by the formula (1), ammonia is selectively adsorbed, resulting in a color change.
Examples of such ammonia detectors include optical sensors (image sensors), resonance sensors, and electrical resistance sensors. Optical sensors can detect color changes before and after adsorption of ammonia gas using a CCD camera or the like. In this case, an image of the ammonia detection material taken by the CCD camera or the like is transmitted to an external device via wireless communication. Resonance sensors can detect the amount of adsorption of ammonia gas by capturing it as a change in the resonance frequency of a resonantly driven piezoelectric material. Electrical resistance sensors can detect the amount of adsorption of ammonia by supporting an ammonia detection material between electrodes provided on a substrate, applying a voltage between the electrodes, and capturing the amount of adsorption of ammonia as a change in the electrical resistance between the electrodes.
Specific examples of metal complexes represented by general formula (1) include _Co0.9Fe0.1 [Ni(CN) ₄ ] _.3.2H2O , _Co0.8Fe0.2 [Ni(CN) _{4 ].3.2H2O, Co[Ni(CN)4 ] .2.7H2O , and} Co(pyrazine)[Ni(CN) ₄ ].

The stretchable food freshness sensor module according to the present invention may include a sensor 21 other than the food freshness sensor 20 .
For example, a humidity sensor may be provided as a sensor 21 other than the food freshness sensor 20. The humidity sensor may be a resistive or capacitive humidity sensor.
As a humidity sensor, for example, a graphene sensor using graphene for electrodes can be used (see Patent Document 3).
A sensor 21 other than the food freshness sensor 20 may be used to correct the freshness information data obtained by the food freshness sensor 20. For example, in a configuration including an ammonia sensor as the food freshness sensor 20 and a humidity sensor in addition to the ammonia sensor, the amount of ammonia measured by the ammonia sensor that depends on humidity may be corrected based on the humidity value measured by the humidity sensor, thereby achieving more accurate measurements. In this case, the correction processing unit that performs the correction processing may be provided in the stretchable food freshness sensor module itself or in the external device 200.

The stretchable food freshness sensor module of the present invention may include a storage unit (memory) that stores freshness information data obtained by the food freshness sensor 20 and data corrected by the correction processing unit, a control circuit that controls and drives each sensor, and a power control circuit that controls the operation of sending power generated by the solar cell described below to the power storage unit for charging. Furthermore, an external device may be configured to include a processor that controls and manages the entire stretchable food freshness sensor module, including the storage unit and control circuit.

<Wireless communication section>
The wireless communication unit 30 wirelessly transmits the freshness information data obtained by the food freshness sensor 20 to, for example, an external device 200 (see FIG. 2). If the stretchable food freshness sensor module is equipped with a memory unit, the freshness information data stored in the memory unit is wirelessly transmitted to the external device 200.

The wireless communication method used between the wireless communication unit 30 and the external device 200 is arbitrary, and may be, for example, a wireless communication method related to a wireless LAN (Local Area Network) such as Wi-Fi (registered trademark), or a wireless communication method related to short-range wireless communication such as Bluetooth (registered trademark).

<External device>
The external device 200 may be, for example, a smartphone, a personal computer, or the like, which is equipped with a storage unit (memory) for storing freshness information data and an information processing unit for processing the freshness information data.

<Battery>
The battery 40 supplies power to the food freshness sensor 20 and the wireless communication unit 30 .
The battery 40 is preferably a solar cell, since it is a stand-alone or self-powered power source that can generate electricity by receiving light.

When the battery 40 is a solar cell, which is a self-power generating power source, it is preferable to have a power storage section 50 as shown in FIG.
If the stretchable food freshness sensor module has a power storage unit 50, power from the battery 40 is supplied to the power storage unit 50, and power is supplied from the power storage unit 50 to the food freshness sensor 20 and the wireless communication unit 30 (see Figure 4).

<Electricity storage unit>
The power storage unit 50 is, for example, an electric double layer capacitor (EDLC) or a secondary battery, and stores the power generated by the solar cell.

<<Solar Cells>>
The solar cell is not particularly limited, and any known solar cell can be used.
For example, in terms of electrode arrangement, either a double-sided electrode solar cell or a back-side electrode solar cell can be used.
Furthermore, as described above, even from the viewpoint of classifying solar cells into three types, silicon-based, compound semiconductor-based, and organic-based, any type of solar cell can be used.
The solar cell may have a single cell or multiple cells, but the following description will be given taking the multiple cell configuration as an example.

Fig. 5 is a plan view schematic diagram of an example of the configuration of the solar cell 40 in the stretchable food freshness sensor module 10 shown in Fig. 1. Hereinafter, the solar cell 40 may be referred to as the solar cell module 40.
Fig. 6 is an exploded cross-sectional view showing a cross section taken along II' in Fig. 5, with the solar cell, the stretchable resin substrate, and the stretchable electrode disassembled. Fig. 7 is a plan view showing the solar cell module 40 shown in Fig. 5 with the solar cell removed.

The solar cell module 40 shown in Figure 5 comprises, on the surface of an elastic resin substrate 10, 15 individual solar cell pieces 40A and an elastic electrode 40B formed in a pattern that electrically connects the 15 individual solar cell pieces 40A.
Hereinafter, the "stretchable electrode" may be referred to as a stretchable electrode pattern.

Here, "individual solar cell" means that the solar cells are not connected to each other. Each solar cell is bonded to the stretchable resin substrate via a stretchable electrode, or via a stretchable electrode and a stretchable conductive adhesive (described below). Conventional solar cell modules are structured so that multiple non-stretchable (or very small stretchability) solar cells are connected to each other, making the conventional solar cell modules non-stretchable. In contrast, in the solar cell module 40 shown in Figure 5, the multiple solar cells are not connected to each other, but rather each solar cell is bonded to the stretchable resin substrate via a stretchable electrode, or via a stretchable electrode and a stretchable conductive adhesive. As a result, the unbonded portions between adjacent solar cells are stretchable, improving the stretchability (stretchability) of the portion comprising the solar cell module 40.

Even for solar cell modules that can generate the same amount of power, a small-sized type composed of many solar cells has a larger number of stretchable parts per unit length than a larger-sized type composed of fewer solar cells, resulting in a higher density of bends, allowing for finer deformations and improving stretchability.The "bend density" (the number of parts (bends) that can be bent per unit length) can be used as an indicator of stretchability.
For example, when the size of each solar cell shown in FIG. 5 is Lx = 1 mm and Ly = 1 mm in the x and y directions, respectively, and the spacing between adjacent solar cells is 0.2 mm, the density of bends in the x direction is 0.86 [pieces/mm] (= 5 pieces/5.8 mm), and the density of bends in the y direction is 0.88 [pieces/mm] (= 3 pieces/3.4 mm).
The density of bends in the portion where the solar cell module 40 is provided is preferably 0.05/mm or more.

When the food freshness sensor sheet of the present invention is applied to wrapping film or food containers and then peeled off for reuse, the area with the highest density of bends, which is a highly flexible part, can be used as the detachment initiation point, and the sheet can be peeled off from this point.

The arrangement of the individual solar cells may be regular or irregular, or some parts may be regular and other parts may be irregular.

In the solar cell module 40 shown in Figure 5, 15 back electrode type solar cells 40A are arranged in the Y direction as multiple solar cell rows connected in series in the X direction, with the ends of the solar cell rows connected together, creating a meandering electrical current path, making them electrically connected in series.

As shown in FIG. 6 , each solar cell 40A has an electrode 25 electrically connected to the p-type semiconductor (hereinafter referred to as the p-type electrode) and an electrode 26 electrically connected to the n-type semiconductor (hereinafter referred to as the n-type electrode). The p-type electrode (first conductive electrode) 25 of each solar cell 40A is electrically connected to the n-type electrode (second conductive electrode) 26 of the next solar cell 40A via a stretchable electrode 40B, and the p-type electrode 25 of one solar cell 40A is electrically connected to the n-type electrode 26 of the next solar cell 40A via the stretchable electrode 40B. In this way, the p-type electrodes 25 and n-type electrodes 26 of each solar cell 40A are electrically connected alternately, thereby connecting the 15 individual solar cell segments in series.

7, the stretchable electrode pattern 40B is formed such that 15 individual solar cell segments are connected in series. Specifically, for the 15 individual solar cell segments, the stretchable electrode pattern 40B is made up of 14 spaced apart stretchable electrodes (40Ba to 40Bn) in order to connect adjacent solar cell segments in sequence.
In the solar cell module 40, the stretchable electrode pattern 40B can have any electrode pattern shape as long as the pattern is formed so that the individual solar cell segments are connected in series. Also, even when the individual solar cell segments are connected in parallel, the stretchable electrode pattern 40B can have any electrode pattern shape accordingly.

Fig. 8 is a plan view schematic diagram of another example of the configuration of a solar cell module. This solar cell module differs from the solar cell modules shown in Figs. 5 to 7 in that it includes a plurality of cell strings, each of which has a plurality of solar cells connected in series, and the stretchable electrode patterns are formed so that the cell strings are connected in series.
A cell string is a series connection of solar cells.

The solar cell module 40-1 shown in Figure 8 includes, on the surface of the stretchable resin substrate 10, four cell strings 40AL1 to 40AL4 in which solar cells 40A are connected in series, and a stretchable electrode 40B formed in a pattern such that the solar cells 40A are connected in series by connecting adjacent cell strings 40AL1 to 40AL4 to each other in series.
The stretchable electrode 40B shown in Figure 8 consists of a stretchable electrode 40BA that connects the cell string 40AL1 and the cell string 40AL2, a stretchable electrode 40BB that connects the cell string 40AL2 and the cell string 40AL3, and a stretchable electrode 40BC that connects the cell string 40AL3 and the cell string 40AL4.

Figure 9 is a plan view schematic diagram of yet another example of the configuration of a solar cell module. The solar cell module shown in Figure 9 differs from the solar cell module shown in Figure 5 in that it includes multiple cell strings in which multiple solar cells are connected in series, and the stretchable electrode pattern is formed so that the cell strings are connected in parallel. The solar cell module shown in Figure 9 also has in common with the solar cell module shown in Figure 8 in that it includes multiple cell strings in which multiple solar cells are connected in series, but differs from the solar cell module shown in Figure 8 in that the stretchable electrode pattern is formed so that the cell strings are connected in parallel.

The solar cell module 40-2 shown in Figure 9 includes two cell strings 40ALL1 and 40ALL2, in which solar cells 40A are connected in series, on the surface of the stretchable resin substrate 10, and a stretchable electrode 40B formed in a pattern that connects the solar cells 40A by connecting the cell strings 40ALL1 and 40ALL2 in parallel with each other.
The stretchable electrode 40B shown in FIG. 9 is made up of stretchable electrodes 40BA1 and 40BA2 that connect cell strings 40ALL1 and 40ALL2 in parallel.

A plurality of cell strings connected in series or in parallel is called a cell array.
The solar cell can be attached to the stretchable resin substrate via a stretchable electrode as an individual solar cell, as a cell string consisting of a plurality of solar cells, as a cell array consisting of a plurality of cell strings, or as a combination of two or more of the individual solar cell, the cell string, and the cell array.

<Stretchable resin base material>
The elastic resin substrate 10 preferably has a breaking elongation of 13% or more.
The elongation at break is defined as {(length at break - length before stretching) / length before stretching} x 100. The elongation at break can be measured in each specified direction, but in this specification, "elongation at break of 13% or more" refers to the elongation at break in the direction in which the elongation at break is greatest. If there is no anisotropy in the elongation at break, the elongation at break will be equal in all directions, and if the anisotropy in the elongation at break is small, the elongation at break will be close in all directions. The elongation at break can be measured, for example, as follows: Five strip-shaped measurement samples, each 10 mm wide and 35 mm long, are cut out from an elastic resin substrate material. The elongation of each measurement sample is calculated using the method described below, and the average value is taken as the elongation. A metal substrate is clamped between the upper and lower grips of the measuring device, and the measurement sample is fixed to the metal substrate with double-sided tape so that the measurement point is 10 mm wide and 10 mm long. The measurement sample is then pulled at a pulling rate of 10 mm/min using a tensile tester (for example, Autograph AGS-5kNX, product name, manufactured by Shimadzu Corporation). The length of the measurement sample at the time of breakage is measured, and the length (10 mm) before pulling is subtracted from the measured length to calculate the elongation.
The definition and measurement method of the breaking elongation percentage also apply to wiring (electrode wiring) and stretchable electrodes described below.

The reason why the elongation at break of the elastic resin substrate 10 is preferably 13% or more will be explained below.
The stretchable food freshness sensor module is intended to be used by adhering it to packaging films such as Saran Wrap (registered trademark) and Krewrap (registered trademark) or food containers. In the case of food containers, it is usually intended to be used by adhering it to the transparent packaging on the lid side.
For reuse, the stretchable food freshness sensor module needs to be stretchable so that it can be easily and quickly attached and detached from packaging wrap films and food containers multiple times. To determine the required level of stretchability, we will consider the breaking elongation using Figure 10.

As shown in FIG. 10, consider a case where a device such as a food freshness sensor is fixed with an L-shaped metal terminal.
The stretchable resin substrate must be stretchable to prevent damage to devices such as food freshness sensors when bent at 180° or greater. For example, when a device with an L-shaped metal terminal and a high terminal shape is bent at 180° or greater (see FIGS. 10( a) and 10(b)), for example, when the device is bent quickly from the side of the L-shaped metal terminal with a force of 10 N or greater, tensile stress is applied to the stretchable resin substrate portion in contact with the L-shaped metal terminal. Assuming that the stretchable food freshness sensor module is peeled off (when bent) at a high speed or with a high force, the stretch rate required for sufficient stress can be calculated as (c-a)/a (×100 in the case of %), where a is the width of the L-shaped metal terminal, b is the length, and c is the oblique side (see FIG. 10(c)). This is because the stretch rate in the oblique side direction of the L-shaped metal terminal is considered to be the stretch rate that will not cause damage to the stretchable resin substrate portion even under conditions of high speed and high force (e.g., 10 N or greater). Assuming that a device with a = 1 and b = 0.525 is mounted, the elongation at break of the elastic resin substrate is 13% or more when c = 1.129. If the elastic resin substrate does not have the elongation required for sufficient stress, the elastic resin substrate will be damaged by the stress generated at the portion in contact with the L-shaped metal terminal.

The breaking elongation of the stretchable resin substrate can be set appropriately depending on the breaking elongation required for the stretchable food freshness sensor module. The breaking elongation can be increased, for example, by increasing the amount of stretchable resin. It can also be adjusted by increasing the mol% of bonds in the resin that have a high breaking elongation. For example, the breaking elongation of the stretchable resin substrate can be increased by increasing the proportion of urethane bonds in the resin.

There are no particular limitations on the resin used for the elastic resin substrate 10, and any known elastic resin can be used. Examples include epoxy resins, urethane resins, urea resins, polyurethane urea resins, methacrylic acid resins, polyacrylic resins, silicone resins, diene resins, polyester resins, polyether resins, polyamide resins, and polystyrene resins.

The resin used in the stretchable resin substrate 10 is preferably soluble in one or more solvents selected from the group consisting of N,N-dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate (BCA), diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, acetone, ethanol, methanol, ethyl lactate, butyl lactate, toluene, isopropyl alcohol, isobutyl alcohol, ethyl acetate, and butyl acetate.

The stretchable resin substrate 10 can be formed by applying and solidifying a resin composition containing the resin used in the stretchable resin substrate 10 and a solvent.

Among the above resins, urethane-based resins are preferred because they can be molded by simply coating and drying the resin composition without undergoing a curing reaction. If a resin requires a curing reaction, the composition and degree of cure may vary in the resin sheet if the curing reaction does not proceed uniformly, resulting in a resin sheet that does not have the desired elasticity, strength, and resistance to deterioration over time.
Furthermore, when a urethane resin is used, it is preferable that the resin component contains a siloxane bond, because in this case the resin composition has appropriate water repellency and hydrolysis of the urethane bond is suppressed.

Hereinafter, the characteristics of the stretchable resin substrate 10 will be described while giving specific examples of resin compositions for producing the stretchable resin substrate 10.
A specific example is a resin composition containing a resin component (sometimes referred to in this specification as "resin component (II)"), in which the resin component has a group represented by the following general formula (11), (21), or (31) and a urethane bond.

(In the formula, Z1 represents an alkyl group, and one or more hydrogen atoms in the alkyl group may be substituted with a cyano group, a carboxy group, or a methoxycarbonyl group, and the two or more substituents may be the same or different. Z2 represents an alkyl group. Z3 represents an aryl group. R4 represents a hydrogen atom or a halogen atom. The bond marked with * is formed between the bond recipient of the group represented by general formula (11), (21), or (31).)

The resin component (II) contained in this resin composition has a urethane bond, and therefore has high flexibility.
Furthermore, resin component (II) is obtained by carrying out a polymerization reaction using a resin having a urethane bond and a polymerizable unsaturated bond and a RAFT agent for carrying out reversible addition-fragmentation chain transfer polymerization (sometimes abbreviated as "RAFT polymerization" herein), from which the group represented by general formula (11), (21), or (31) is derived. By carrying out the polymerization reaction in this manner, gelation of the polymerized resin during the process of forming a crosslinked structure is avoided, and a resin component with the desired degree of polymerization and crosslinked state is obtained. In other words, resin component (II) having a group represented by general formula (11), (21), or (31) has small variation in degree of polymerization and crosslinked state.
Furthermore, resin component (II) may have a siloxane bond, in which case the resin composition has appropriate water repellency and the hydrolysis of the urethane bond in resin component (II) is suppressed. Such resin component (II) can be obtained by carrying out a polymerization reaction using a resin having a siloxane bond and a polymerizable unsaturated bond.
The method for producing the resin component (II) by RAFT polymerization will be described in detail separately.

The resin having a urethane bond and a polymerizable unsaturated bond used in the production of resin component (II) is an oligomer and may be referred to as "resin (a)."
The resin having a siloxane bond and a polymerizable unsaturated bond used in producing the resin component (II) is an oligomer, and in this embodiment, may be referred to as "resin (b)."
Resin component (II) is a polymer formed by polymerizing resins (a) together at their polymerizable unsaturated bonds. When resin (b) is used, resin component (II) is a polymer formed by polymerizing resins (a) and (b) at their polymerizable unsaturated bonds.

When resin (b) is used, the resin component (II) preferably has both a urethane bond and a siloxane bond in one molecule.

The resin (a) is not particularly limited as long as it has a urethane bond and a polymerizable unsaturated bond.
Examples of the resin (a) include those having a urethane bond and a (meth)acryloyl group as a group having a polymerizable unsaturated bond, and more specifically, urethane (meth)acrylates and the like.
In this specification, the term "(meth)acrylate" encompasses both "acrylate" and "methacrylate." The same applies to terms similar to (meth)acrylate. For example, the term "(meth)acryloyl group" encompasses both "acryloyl group" and "methacryloyl group."

The resin (b) is not particularly limited as long as it has a siloxane bond and a polymerizable unsaturated bond.
Examples of the resin (b) include various known silicone resins having a (meth)acryloyl group as the group having a polymerizable unsaturated bond, and more specifically, examples thereof include modified polydialkylsiloxanes in which a (meth)acryloyl group is bonded to one or both ends of a polydialkylsiloxane such as polydimethylsiloxane.

Resin component (II) has high solubility in solvents due to its composition, and therefore the resin composition containing resin component (II) also has high solubility in solvents.
Such a highly soluble resin composition can be easily formed into a resin composition layer by, for example, printing it onto an object to be applied using various printing methods. Then, by solidifying the resin composition layer by drying without curing, a layer (resin layer, resin sheet) similar to the resin sheet can be produced. This method is suitable for forming electrodes or wiring using the resin composition containing a conductive component.

Such a resin composition having high solubility is used to form a resin sheet having stretchability, and a stretchable device constructed using this resin sheet has the great advantage of being able to suppress breakage during stretching.
From the viewpoint of materials, possible causes of breakage of ordinary stretchable devices during stretching include (i) structural defects such as voids and interfacial peeling caused by shrinkage due to heat or curing reaction, (ii) uneven hardness caused by uneven composition, and (iii) deterioration of materials over time caused by light irradiation, oxidation, etc.
Therefore, by suppressing structural defects such as voids, interfacial peeling, compositional irregularities, and deterioration of materials over time, it is possible to suppress breakage of stretchable devices when they are stretched.
Although stretchable substrates are generally processed by molding using thermal melting or crosslinking using thermal or photo-curing reactions, there are concerns that the reliability of stretchable devices may be reduced when considering microfabrication due to the reasons (i) to (iii) above. In contrast, if there were a resin that could be molded by simply coating and drying the resin composition, compatible with lamination methods, it would be expected that good results could be obtained.

The stretchable resin substrate 10 is obtained by drying and solidifying the resin composition of the specific example to obtain a stretchable resin substrate in the form of a resin sheet (hereinafter, sometimes referred to as a "resin sheet"). A plurality of resin sheets may be stacked to produce the stretchable resin substrate.
The resin sheet contains resin component (II) as a main component and therefore has good stretchability. When resin (b) is used, the resin sheet also has moderate water repellency, which suppresses deterioration over time due to hydrolysis. The resin sheet having such properties is particularly suitable for constructing various stretchable devices, including wearable devices.

The resin sheet can be formed simply by solidifying the resin composition through drying, as described above, without undergoing a curing reaction. Therefore, there are no problems associated with undergoing a curing reaction.

For example, it is extremely difficult to uniformly cure a material that is not transparent to ultraviolet light in a photocurable resin sheet. For example, when ultraviolet light is irradiated around a mounted device or electronic component in a photocurable resin sheet, the transmittance of ultraviolet light varies, resulting in areas with different degrees of cure, and the resin sheet is prone to breakage in areas with low crosslink density. Furthermore, non-crosslinked areas are prone to deterioration due to oxidation.
On the other hand, the thermosetting reaction tends to cause differential shrinkage in the resin sheet due to heat distribution during curing. Such differential shrinkage can easily cause separation at the interface between different constituent materials, such as between a device and a sealant. Furthermore, if regions with different degrees of cure occur in the resin sheet due to heat distribution, repeated expansion and contraction can easily cause deterioration.
Furthermore, in both the photocuring reaction and the thermosetting reaction, it is difficult for the reaction to proceed uniformly within the resin sheet, which causes variations in the composition and degree of cure within the resin sheet, resulting in the cured resin sheet lacking the desired elasticity and strength. Furthermore, since the resin contains a curing agent, it is prone to deterioration over time due to heat and light.
In contrast, the resin sheet obtained by solidifying the resin composition of the specific example by drying does not have such a problem.

The resin sheet can be produced, for example, by applying the resin composition to the desired location and solidifying it by drying, without undergoing a curing reaction.

The resin composition can be applied by known methods, such as using various coaters or wire bars, or by various printing methods, including inkjet printing.

When producing a resin sheet, the drying temperature for the resin composition is preferably 25 to 150°C, and more preferably 25 to 120°C. A drying temperature of 25°C or higher allows for more efficient production of the resin sheet. A drying temperature of 150°C or lower prevents the drying temperature from becoming excessively high, reducing deformation of the release sheet and damage to the resin sheet, and suppressing deterioration of the resin sheet.

When producing the resin sheet, the drying time for the resin composition can be set appropriately depending on the drying temperature, but is preferably 10 to 120 minutes, and more preferably 30 to 90 minutes. When the drying time is within this range, a resin sheet with excellent properties can be efficiently produced.

Completion of solidification (formation of a resin sheet) through drying of the resin composition can be confirmed, for example, by the fact that no clear change in the mass of the resin composition being dried is observed.

The thickness of the elastic resin substrate is not particularly limited, but for example, a thickness of 10 to 5000 μm can be used.

<Wiring (electrode wiring), stretchable electrode>
The electrode wiring (not shown) that connects the functional devices of the stretchable food freshness sensor module and the stretchable electrode 40B used in the solar cell modules 40, 40-1, and 40-2 preferably have a breaking elongation of 40% or more.
The reason why the breaking elongation percentage of the wiring and the stretchable electrode is preferably 40% or more will be explained with reference to FIG.
Referring to FIG. 10(c), assuming that wiring and stretchable electrodes with a=1 and b=1 are implemented, c=√2, and the value of (c−a)/a (×100 in the case of %) requires a stretch rate of 41%.

The electrode wiring that connects each functional device in the stretchable food freshness sensor module and the stretchable electrode 40B used in the solar cell modules 40, 40-1, and 40-2 can be made of a material containing a stretchable resin and a conductive filler.
The elastic resin is not particularly limited, and any known elastic resin can be used, such as epoxy resins, urethane resins, urea resins, polyurethane urea resins, methacrylic acid resins, polyacrylic resins, silicone resins, diene resins, polyester resins, polyether resins, polyamide resins, polystyrene resins, and polyimide resins.

The conductive filler is not particularly limited, and any known conductive filler can be used. Examples include silver (Ag) powder, carbon (C), copper (Cu) powder, palladium (Pd) powder, gold (Au) powder, and platinum (Pt) powder. Of these, silver is preferred due to its low resistance.

The resin used for the electrode wiring and the stretchable electrode 40B is preferably soluble in one or more solvents selected from diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate (BCA), diethylene glycol monoethyl ether acetate, and α-terpineol.

Of the above resins, urethane-based resins are preferred because they can be solidified without undergoing a curing reaction. Furthermore, urethane-based resins have excellent elasticity, making it possible to create electrode wiring and stretchable electrodes that are elastic and conductive.

When producing electrode wiring or a stretchable electrode pattern, a conductive filler is added as a conductive component to the resin composition exemplified above to produce an electrode wiring paste or a stretchable electrode paste. The electrode wiring paste or stretchable electrode paste is then applied to a stretchable resin substrate. The solvent is then removed and the resulting paste is dried and solidified to produce the electrode wiring paste or stretchable electrode pattern. When the resin component (II) described above is used, solidification can be achieved without a curing reaction.

The thickness of the electrode wiring paste and the stretchable electrode is not particularly limited, but can be, for example, 3 to 50 μm.

The breaking elongation rate of the electrode wiring and stretchable electrodes can be set appropriately depending on the breaking elongation rate required for the stretchable food freshness sensor module. The breaking elongation rate can be increased, for example, by increasing the amount of stretchable resin. It can also be adjusted by increasing the mol% of bonds with high breaking elongation rates in the resin. For example, the breaking elongation rate of the electrode wiring and stretchable electrodes can be increased by increasing the proportion of urethane bonds in the resin.

<Stretchable conductive adhesive>
Each functional device included in the stretchable food freshness sensor module may be bonded to the electrode wiring using a stretchable conductive adhesive.
A case where a solar cell, a stretchable resin substrate, and a stretchable electrode are joined using a stretchable conductive adhesive will be described with reference to FIG.

FIG. 11 is an exploded cross-sectional view showing a solar cell, a stretchable conductive adhesive, a stretchable resin substrate, and a stretchable electrode.
As shown in Fig. 11, it is preferable to bond a solar cell 40A and a stretchable electrode 40B together using a stretchable conductive adhesive 40C. The stretchable conductive adhesive 40C can be solidified by drying.
A specific bonding method is, for example, to use a known method such as screen printing to apply an elastic conductive adhesive 40C to each position of the elastic electrode pattern 40B, and then to install the back electrode type solar cell 40A by arranging the electrode patterns 25, 26 on the back electrode type solar cell 40A side on the elastic conductive adhesive 40C that has been applied in the same pattern as the elastic electrode pattern 40B, and then to install the back electrode type solar cell 40A, and then to remove the solvent from the elastic conductive adhesive 40C and dry and solidify it.

The stretchable conductive adhesive 40C contains a stretchable resin and a conductive filler.
The elastic resin is not particularly limited, and any known elastic resin can be used, such as epoxy resins, urethane resins, urea resins, polyurethane urea resins, methacrylic acid resins, polyacrylic resins, silicone resins, diene resins, polyester resins, polyether resins, polyamide resins, polystyrene resins, and polyimide resins.

The conductive filler is not particularly limited, and any known conductive filler can be used. Examples include silver (Ag) powder, carbon (C), copper (Cu) powder, palladium (Pd) powder, gold (Au) powder, and platinum (Pt) powder. Of these, silver powder is preferred because it has low resistance and is less susceptible to oxidation.

The resin used in the stretchable conductive adhesive 40C is preferably soluble in one or more solvents selected from methyl ethyl ketone (MEK), methyl isobutyl ketone, butyl acetate, propylene glycol monomethyl ether acetate (PGMEA), and diethylene glycol monomethyl ether acetate (BCA).

The breaking elongation rate of the stretchable conductive adhesive 40C can be set appropriately according to the breaking elongation rate required for the stretchable food freshness sensor module.
In addition, when the resin constituting the stretchable conductive adhesive 40C is the same as the resin constituting the stretchable electrode 40B, the breaking expansion rate of the stretchable conductive adhesive 40C will be approximately the same as the breaking expansion rate of the stretchable electrode 40B.

Of the above resins, urethane-based resins are preferred, as they can be solidified without undergoing a curing reaction.

The thickness of the elastic conductive adhesive is not particularly limited, but can be, for example, 10 to 1500 μm.

<Action and effect>
The function and effect of the stretchable food freshness sensor module according to this embodiment will be described with reference to Figures 12(a) and (b).

As shown in Figure 12(b), when a substrate that is not thin enough is bent, only the center of the substrate is free of stress, but when bent, compressive stress acts on the inside of the substrate and tensile stress acts on the outside. In other words, contracting stress acts on the inside of the substrate and stretching stress acts on the outside.

Figure 12(a) is a schematic diagram of the stretchable food freshness sensor module 10 according to this embodiment. The direction and length of the double-headed arrows in the figure conceptually indicate the direction and magnitude of the tensile stress in the vicinity. The stretchable electrodes and stretchable conductive adhesive are not shown.

In the stretchable food freshness sensor module 100 shown in Figure 12(a), the stretchable portion is only the portion of the stretchable resin substrate 10 where no functional devices are bonded. The portion of the stretchable resin substrate 10 where each functional device is bonded does not stretch.
This point will be conceptually explained using FIG. 13, taking as an example the portion where the solar cell 40 is arranged.

In FIG. 13, the stretchable electrodes and the stretchable conductive adhesive are omitted from the illustration.
When the stretchable resin substrate 10 is divided into three portions 10a, 10b, and 10c as viewed from the direction in which the stretchable resin substrate 10, stretchable electrode 40B, stretchable conductive adhesive 40C, and solar cell 40A are stacked, portions 10a and 10c are stretchable because they do not have a non-stretchable solar cell 40AA bonded thereon. In contrast, portion 10b is bonded to a non-stretchable solar cell 40AA, so its stretching is suppressed. Here, because a stretchable electrode 40BAA and a stretchable conductive adhesive 40A are disposed between portion 10a and the solar cell 40AA, peeling between portion 10b, which attempts to stretch, and the non-stretchable solar cell 40AA is suppressed.

In addition, in the stretchable food freshness sensor module, the food freshness sensor can be replaced with a sensor other than a food freshness sensor to create a stretchable sensor module.

<Food packaging wrap>
FIG. 14 is a conceptual diagram of a food packaging wrap to which the stretchable food freshness sensor module of this embodiment is adhered, where (a) is a vertical cross-sectional view and (b) is a plan view.

14 includes a stretchable food freshness sensor module 100 on the surface of the wrap 1001 facing the fresh food. The stretchable food freshness sensor module 100 includes, on a stretchable resin substrate 10, a food freshness sensor 20 capable of detecting the freshness of food, a sensor 21 other than the food freshness sensor, a wireless communication unit 30 that transmits freshness information data detected by the food freshness sensor 20 to an external device, a battery 40 that supplies power to the food freshness sensor 20 and the wireless communication unit 30, and a power storage unit 50.
14 illustrates an example in which fresh food is placed in a container for placing fresh food, and the container is then covered with food packaging wrap 1000. BLE stands for Bluetooth Low Energy. The food freshness sensor 20 may be, for example, an ammonia sensor, and the sensor 21 other than the food freshness sensor may be, for example, a graphene sensor.

<Food containers>
FIG. 15 is a conceptual diagram of a food container to which the stretchable food freshness sensor module of this embodiment is attached, where (a) is a vertical cross-sectional view and (b) is a plan view.

15 includes a stretchable food freshness sensor module 100 at an opening 2001a on the surface of the container 2001 facing the fresh food. The stretchable food freshness sensor module 100 includes, on a stretchable resin substrate 10, a food freshness sensor 20 capable of detecting the freshness of food, a sensor 21 other than the food freshness sensor, a wireless communication unit 30 that transmits freshness information data detected by the food freshness sensor 20 to an external device, a battery 40 that supplies power to the food freshness sensor 20 and the wireless communication unit 30, and a power storage unit 50.
FIG. 15 illustrates the stretchable food freshness sensor module 100 being peeled off for reuse.

REFERENCE SIGNS LIST 10 Stretchable resin substrate 20 Food freshness sensor 21 Sensor 30 Wireless communication unit 40 Battery 50 Power storage unit 100 Stretchable food freshness sensor module 1000 Food packaging wrap 2000 Food container 2001 Opening

Claims (8)

an elastic resin substrate;
a food freshness sensor capable of detecting the freshness of food;
a wireless communication unit that transmits freshness information data detected by the food freshness sensor to an external device;
a battery that supplies power to the food freshness sensor and the wireless communication unit;
Equipped with
The food freshness sensor, the wireless communication unit, and the battery are disposed directly or indirectly on the stretchable resin substrate,
The stretchable food freshness sensor module has a breaking elongation of the stretchable resin substrate of 13% or more . an elastic resin substrate;
a food freshness sensor capable of detecting the freshness of food;
a wireless communication unit that transmits freshness information data detected by the food freshness sensor to an external device;
a battery that supplies power to the food freshness sensor and the wireless communication unit;
Equipped with
The food freshness sensor, the wireless communication unit, and the battery are disposed directly or indirectly on the stretchable resin substrate,
The stretchable food freshness sensor module, wherein the battery is a solar cell. The stretchable food freshness sensor module of claim 1 or 2, comprising two or more types of food freshness sensors. The stretchable food freshness sensor module of claim 3, wherein the two or more types of food freshness sensors can detect two or more types of gas components emitted from food. The stretchable food freshness sensor module of claim 4, wherein the two or more gas components are selected from the group consisting of ammonia, diethylamine, trimethylamine, ethylene, alcohol, lower fatty acids, aldehydes, hydrogen sulfide, hydrogen ions, methane, and carbon dioxide. The stretchable food freshness sensor module according to any one of claims 1 to 5 , wherein the electrode wiring connecting the functional devices of the food freshness sensor, the wireless communication unit, and the battery has a breaking elongation rate of 40% or more. A wrap for packaging food, comprising the stretchable food freshness sensor module according to any one of claims 1 to 6 adhered thereto. A food container having an opening, wherein the stretchable food freshness sensor module according to any one of claims 1 to 6 is arranged to cover the opening and face the food side.