Wireless tag with temperature sensor function

Abstract

Provided is a wireless tag with a temperature sensor function capable of suppressing temperature rise of at least a part including the temperature sensor even when the tag is installed in a sunny place irradiated with sunlight. A wireless tag 10 comprising a semiconductor element 12 equipped with a temperature sensor includes: an antenna 14 that receives a wireless instruction from an external reader of the wireless tag 10 or transmits wireless signals to the reader; the semiconductor element 12 that wirelessly transmits temperature data measured by the temperature sensor from the antenna 14 to the reader in response to the wireless instruction from the reader received by the antenna 14; and a conductive pattern 16 that electrically connects the semiconductor element 12 and the antenna 14. The wireless tag is characterized in that the outer peripheral surface of a part including the temperature sensor is covered with a white resin containing white powder 24p so that when the wireless tag 10 is irradiated with sunlight, the sunlight is reflected and the temperature rise of at least the part including the temperature sensor can be suppressed.

Description

Wireless tag with temperature sensor function

[0001] The present invention relates to a wireless tag with a temperature sensor function, which is provided with a semiconductor element having a temperature sensor function.

[0002] Fields where fruits and other plants are grown are large, and there is variation in the cultivation environment, such as temperature and humidity, making it impossible to grasp the cultivation environment of the entire field by measuring the cultivation environment in one location. For this reason, as in Patent Document 1 below, multiple wireless tags are used in the field to measure the cultivation environment at multiple locations, making it possible to grasp the cultivation environment of the field. The wireless tags are equipped with environmental measurement sensors that measure temperature, humidity, etc., and can wirelessly transmit environmental data measured by the environmental measurement sensors to the reader in response to wireless instructions from a reader outside the wireless tags. Because wireless tags are small and lightweight and can be installed in multiple locations in the field, the environment of the entire field, including its variations, can be grasped, which can be useful for plant cultivation.

[0003] However, according to the inventors' investigations, it was found that wireless tags with temperature sensor functions installed in outdoor fields exposed to sunlight transmitted measurement data of temperatures higher than the ambient temperature, even when installed in the shade. In particular, it was found that in the case of wireless tags equipped with temperature sensors installed in sunny areas exposed to sunlight, the temperature of the part containing the temperature sensor rose, causing the transmitted measurement data to be significantly higher than the ambient temperature. The same was true in fields with greenhouses.

[0004] Japanese Patent Application Laid-Open No. 2020-137477

[0005] An object of the present invention is to provide a wireless tag with a temperature sensor function that can suppress a rise in temperature of at least the part of the temperature sensor contained therein, even when the tag is placed in a sunny location where sunlight is irradiated.

[0006] The wireless tag with temperature sensor function developed to achieve the above-mentioned object is a wireless tag having a semiconductor element with a temperature sensor, and contains an antenna that receives wireless instructions from a reader outside the wireless tag or transmits wireless signals to the reader, the semiconductor element that wirelessly transmits temperature data measured by the temperature sensor from the antenna to the reader in response to wireless instructions from the reader received by the antenna, and a conductive pattern that electrically connects the semiconductor element and the antenna, and is characterized in that when sunlight is irradiated onto the wireless tag, the outer surface of the portion containing the temperature sensor is covered with a white resin layer containing white powder so as to reflect the sunlight and suppress a rise in temperature of at least the portion containing the temperature sensor.

[0007] The white powder is preferably one or more selected from the group consisting of titanium oxide, alumina, barium sulfate, magnesium oxide, zinc oxide and calcium carbonate.

[0008] The thickness of the white resin layer is preferably 200 μm or more.

[0009] The white powder preferably has an average particle size of 0.1 to 10 μm as measured by the weight average method.

[0010] The amount of the white powder is preferably 1 to 30 parts by mass relative to the resin forming the white resin layer.

[0011] The white resin layer preferably reflects 80% or more of the light having a wavelength of 300 to 800 nm of the sunlight that is irradiated onto the white resin layer.

[0012] The resin forming the white resin layer is preferably silicone rubber.

[0013] It is preferable that the entire outer peripheral surface of the wireless tag is covered with the white resin layer.

[0014] The outer peripheral surface of the white resin layer is preferably covered with a hydrophilic coating.

[0015] According to the wireless tag with temperature sensor function of the present invention, at least the outer surface of the encapsulated part of the temperature sensor is covered with a white resin layer containing white powder, so that even when the tag is installed in a sunny location where sunlight is irradiated, the temperature rise of at least the encapsulated part of the temperature sensor can be suppressed, and temperature data that is as close as possible to the ambient temperature can be wirelessly transmitted.

[0016] FIG. 1(a) is a partial cross-sectional front view of a wireless tag with a temperature sensor function according to the present invention, and FIG. 1(b) is a cross-sectional view taken along plane A-A of FIG. 1(a). FIG. 2 is a cross-sectional view illustrating a method for manufacturing the wireless tag with a temperature sensor shown in FIG. 1. FIG. 3 is a graph showing the results of measuring the reflectance of various colored silicone rubber plates using an ultraviolet-visible-infrared spectrophotometer. FIG. 4 is a graph showing the results of measuring the transmittance and absorptance of various colored silicone rubber plates using an ultraviolet-visible-infrared spectrophotometer. FIG. 5 is a graph showing the results of measuring the reflectance, transmittance, and absorptance of white silicone rubber plates containing various white powders using an ultraviolet-visible-infrared spectrophotometer. FIG. 6 is a cross-sectional view illustrating another example of a wireless tag with a temperature sensor function according to the present invention. FIG. 7 is a cross-sectional view illustrating another example of a wireless tag with a temperature sensor function according to the present invention. FIG. 8 is a cross-sectional view illustrating another example of a wireless tag with a temperature sensor function according to the present invention. FIG. 9 is an explanatory diagram illustrating an example of using a wireless tag with a temperature sensor function according to the present invention in mango cultivation. FIG. 10 is a cross-sectional view illustrating a state in which the wireless tag with a temperature sensor function according to the present invention is covered with a hydrophilic coating.

[0017] Fig. 1(a) shows a partial cross-sectional front view of a wireless tag with a temperature sensor function according to the present invention, and Fig. 1(b) shows a cross-sectional view taken along plane A-A of Fig. 1. The wireless tag with a temperature sensor function 10 (hereinafter referred to as wireless tag 10) shown in Fig. 1 has an inlet portion 20 formed therein, which contains, as its inner portion, a flexible substrate 11 made of paper, PET, PVC, or the like, a semiconductor element 12 equipped with a contact-type temperature sensor such as a thermocouple on the upper surface of the substrate 11, an antenna 14 for receiving wireless instructions from a reader (described below) outside the wireless tag 10 or transmitting wireless signals to the reader, a conductive pattern 16 electrically connecting the semiconductor element 12 and the antenna 14, a protective layer 18a made of a resin such as polyethylene terephthalate that covers the semiconductor element 12, the antenna 14, and the conductive pattern 16 via an adhesive layer 18b, and an adhesive layer 28c provided on the underside of the substrate 11. Furthermore, the lower side of the inlet portion 20 is protected by being inserted into a recess in the lower protective layer 24a, and the upper side is protected by being inserted into a recess in the upper protective layer 24b. In the wireless tag 10 shown in Fig. 1, as shown in Fig. 1(b), the antenna 14 and the conductive pattern 16 are provided on both sides of the semiconductor element 12. One edge of such a wireless tag 10 is formed with a hole 26 through which a string or the like for hanging the wireless tag 10 in a predetermined position is inserted.

[0018] In the wireless tag 10 shown in FIG. 1 , the lower protective layer 24a and the upper protective layer 24b are white resin layers formed from a white resin. The white resin contains a white powder 24p that reflects sunlight, minimizing the temperature rise of the inlet portion 20 that forms the wireless tag 10 when the wireless tag 10 is irradiated with sunlight. The white powder 24p blended into the white resin can be one or more selected from titanium oxide, alumina, barium sulfate, magnesium oxide, zinc oxide, and calcium carbonate. The shape of the white powder 24p is preferably granular or rod-like, with rod-like titanium oxide being preferred. The particle size, measured by weight average, is preferably 0.1 to 10 μm, and even more preferably, the rod-like shape has a minor axis of 0.2 to 1.0 μm and a major axis of 1 to 10 μm. The amount of the white powder 24p is preferably 1 to 30 parts by mass per 100 parts by mass of the resin.

[0019] The resin forming the white resin is preferably one that has light resistance and flexibility, and examples thereof include silicone rubber, acrylic rubber, butyl rubber, ethylene propylene rubber, fluororubber, chloroprene rubber, polyurethane, chlorosulfonated polyethylene, polyvinyl chloride, etc. Silicone rubber is particularly preferred.

[0020] The lower protective layer 24a and upper protective layer 24b of the wireless tag 10, which are made of white resin, can be formed by any method. As shown in Fig. 2, the inlet portion 20 is sandwiched between the recesses of the lower protective layer 24a and the upper protective layer 24b, which are formed by compression molding or injection molding using a mold. The lower side of the inlet portion 20 is inserted into the recess of the lower protective layer 24a and fixed to the bottom surface of the recess of the lower protective layer 24a by the adhesive layer 28c of the inlet portion 20, and the upper side of the inlet portion 20 is inserted into the recess of the upper protective layer 24b. The lower protective layer 24a and the upper protective layer 24b can be formed by bonding their end surfaces by molecular adhesion or the like to form the wireless tag 10 shown in Fig. 1.

[0021] Figure 3 shows the results of an investigation into the ability of the white resin layer to sufficiently reflect sunlight. Figure 3 also shows the results of measuring the reflectance of various colored silicone rubber plates (0.8 mm thick) using an ultraviolet-visible-infrared spectrophotometer (UV-3600Plus, manufactured by Shimadzu Corporation). The colored silicone rubber plates shown in Figure 2 are as follows: "White": A white silicone rubber plate in which 2 parts by mass of titanium oxide with an average particle size (weight average method) of 0.1 to 10 μm as a white pigment is blended with the silicone rubber. "Yellow": A yellow silicone rubber plate in which 2 parts by mass of lead chromate as a yellow pigment is blended with the silicone rubber. "Green": A green silicone rubber plate in which 2 parts by mass of copper carbonate as a green pigment is blended with the silicone rubber. "Gray": A gray silicone rubber plate in which 0.3 parts by mass of titanium oxide as a white pigment and 0.1 parts by mass of carbon black as a black pigment are blended with the silicone rubber. "Pink": A pink silicone rubber plate in which 2 parts by mass of azo-based pink pigment is blended with the silicone rubber.

[0022] As is clear from FIG. 3, the white silicone rubber plate has a higher reflectivity of sunlight than silicone rubber plates of other colors, and the reflectivity is particularly high at 80% or more in the wavelength range of 300 to 800 nm, which is the wavelength range of sunlight that reaches the earth's surface.

[0023] The sunlight transmittance of the various colored silicone rubber plates shown in Figure 3 was measured using the ultraviolet-visible-infrared spectrophotometer described above. The results are shown in Figure 4(a) and the sunlight absorptance was measured in Figure 4(b).

[0024] As shown in Figure 4(a), the transmittance of the white silicone rubber plate in the wavelength region of 300 to 800 nm is slightly higher than that of the gray silicone rubber plate, but lower than that of the pink, yellow, and green silicone rubber plates. Similarly, as shown in Figure 3(b), the absorptance of the white silicone rubber plate in the wavelength region of 300 to 800 nm is also lower than that of the gray, pink, yellow, and green silicone rubber plates.

[0025] As is clear from FIGS. 3 and 4, in the wavelength range of 300 to 800 nm, which is the wavelength range of sunlight that reaches the earth's surface, the white silicone rubber plate has a higher reflectance and a lower transmittance and absorptance than silicone rubber plates of other hues.

[0026] The white silicone rubber plates shown in FIGS. 3 and 4 contain titanium oxide as the white powder. The reflectance, transmittance, and absorptance of silicone rubber plates containing the white powders shown in Table 1 below as the white powder were measured in the same manner as in FIGS. 2 and 3 in the wavelength range of 300 to 2000 nm. The results are shown in FIG. 5.

[0027]

[0028] As is clear from FIG. 5, the white silicone plates containing various white powders have a higher reflectance and lower transmittance and absorptance than the silicone rubber plates of other colors shown in FIGS. 3 and 4.

[0029] 1, by covering the outer periphery of the wireless tag 10 with a lower protective layer 24a and an upper protective layer 24b made of a white resin containing a white powder 24p, when sunlight is irradiated onto the wireless tag 10, the lower protective layer 24a and the upper protective layer 24b reflect the sunlight without transmitting or absorbing it, thereby suppressing an increase in the temperature of the inlet 20 of the wireless tag 10 and enabling temperature data as close as possible to the ambient temperature to be wirelessly transmitted from the antenna 14 to the reader. This is also evident from the fact that the surface temperature of the wireless tag 10 exposed to sunlight was measured at 35°C using a non-contact reader / writer. On the other hand, when a conventional wireless tag not covered with the lower protective layer 24a and the upper protective layer 24b was exposed to sunlight and its surface temperature was measured in the same manner, it rose to 42°C, indicating that the body temperature of the conventional wireless tag is higher than that of the wireless tag 10.

[0030] 1 and 2, the inlet portion 20 is covered with a lower protective layer 24a and an upper protective layer 24b made of a white resin, but as shown in Fig. 6, the peripheral surfaces of the lower protective layer 22a and the upper protective layer 22b that cover the inlet portion 20 and are made of a resin such as a silicone resin that does not contain white particles may be covered with a white resin coating 24 made of a white resin, or as shown in Fig. 7, the inlet portion 20 covered with the white resin coating 24 may be protected by a lower protective layer 22a and an upper protective layer 22b that are made of a resin such as a silicone resin that does not contain white particles.Also, as shown in Fig. 8, the inlet portion 20 may be covered with only the white resin coating 24.

[0031] The wireless tag 10 shown in Figures 1 to 8 may be a passive type in which the semiconductor element 12 is energized by radio waves from a reader and temperature data measured by a temperature sensor is transmitted to the reader, or an active type in which the semiconductor element 12 is driven by a built-in battery and temperature data measured by a temperature sensor is transmitted to the reader.The wireless tag 10 may be a passive type in general, or a semi-active type in which a built-in battery is used to power the tag when radio waves are received from a reader.

[0032] The wireless tag 10 shown in Figures 1 to 8 is used, for example, in greenhouse mango cultivation. In greenhouse mango cultivation, greenhouse temperatures are controlled to maintain a temperature suitable for mango cultivation, but maintaining a constant greenhouse temperature is difficult, and temperature variations are inevitable. Meanwhile, because the ripening of mangoes is guided by the accumulated temperature exceeding a predetermined temperature, the harvest time for each mango varies. Therefore, as shown in Figure 9, wireless tags 10 are hung near individual mangoes 32 by strings 30 inserted through holes 26. Temperature data measured from the ambient temperature of a given mango 32 is transmitted to a reader 28, and the accumulated temperature of the mango 32 is calculated to determine the harvest time. The wireless tag 10 can eliminate the influence of sunlight and wirelessly transmit temperature data to the reader 28 that is as close as possible to the temperature near the mango 32. The temperature data transmitted to the reader 28 is then transmitted from the reader 28 to a personal computer or the like, where the accumulated temperature is calculated and the harvest time for each mango 32 is determined. If necessary, the harvest time may be determined by adding light data of the light reception time and / or wavelength from a light sensor and / or humidity data from a humidity sensor to the temperature data.

[0033] As shown in Figure 9, to accurately measure the ambient temperature of each mango 32, if the surface of the wireless tag 10 is contaminated with dust or other contaminants, sunlight may be absorbed by the contaminants, potentially raising the temperature of the wireless tag 10. Therefore, it is preferable to cover the outer surface of the wireless tag 10 with a hydrophilic coating 34, as shown in Figure 10, to suppress the temperature rise of the wireless tag 10 while also achieving anti-fouling effects. Examples of hydrophilic coatings 34 include hydrophilic silane coupling agents, polysilazanes, titanium oxides, polyether-modified silicones, and sulfobetaine polymers. Sulfobetaine polymers are particularly preferred. The hydrophilic coating 34 containing sulfobetaine polymers is formed by adsorbing, reacting, or bonding the sulfobetaine polymer to the surface of the white resin layer 24 of the wireless tag 10. If necessary, the water-soluble electrolyte may be adsorbed, reacted, or bonded to a free sulfobetaine polymer and an ionized sulfobetaine polymer electrolyte salt.

[0034] The sulfobetaine polymer has the following chemical formula (1): (In formula (1), R １ is a hydrogen atom or a methyl group, and n1 and n2 are numbers from 2 to 6), and / or the following chemical formula (2): (In formula (2), R ２ is a hydrogen atom or a methyl group, n3, n5, n6 and n8 are numbers from 2 to 6, and n4 ａ and n7 ａ are all 0 or n4 ａ and n7 ａ is 1 and n4 ｂ and n7 ｂ is a number from 1 to 3), or a polymer comprising only repeating units having a sulfobetaine group represented by the chemical formula (1) and / or (2) and a repeating unit having a sulfobetaine group represented by the following chemical formula (3): (In formula (3), R ３ is a hydrogen atom or a methyl group, n9 is a number from 2 to 6, n10 is a number from 0 to 1, and R ４ is any active functional group selected from an azide group, a sulfo group, an alkoxysilyl group, and a hydroxyl group), or a repeating unit having an active functional group represented by the following chemical formula (4): (In formula (4), R 5 is a hydrogen atom or a methyl group, and R 6 is any functional group selected from a carboxyl group, an ethylene glycol group or an ethylene glycol oligomer, an acrylic group, and a methacrylic group).

[0035] A hydrophilic coating 34 containing a sulfobetaine polymer was formed on one surface of a resin plate made of the same resin as the white resin layer 24 of the wireless tag 10. After 14 days of outdoor exposure, the hydrophilicity of the hydrophilized surface of the resin plate was measured using a liquid drop method, and the hydrophilicity of the hydrophilized surface was found to be good, with a contact angle of 5° or less. A low contact angle of 5° or less means that the high hydrophilicity allows the hydrophilic coating 34 to be wetted without being repelled by water, and a water film spreads across the entire surface of the hydrophilic coating 34. As a result, the surface of the wireless tag 10, which has good hydrophilicity, is less susceptible to rainwater-induced dirt and dust. Even if dirt and dust do adhere, they are easily removed by wind or simple washing with water. A wireless tag 10 formed with a hydrophilic coating 34 having such excellent hydrophilicity and durability can resist dirt and rainwater contamination even when used outdoors for long periods of time, facilitating maintenance of the wireless tag 10.

[0036] To form the hydrophilic coating 34 containing the sulfobetaine polymer on the surface of the white resin layer 24 of the wireless tag 10, first, a hydrophilic aqueous solution in which at least a portion of the sulfobetaine polymer is dissolved is prepared, and then the surface of the white resin layer 24 of the wireless tag 10 is subjected to at least one dry treatment selected from plasma discharge treatment, corona discharge treatment, ultraviolet irradiation treatment, excimer irradiation treatment, electron beam irradiation treatment, and radiation irradiation treatment to generate functional groups that react with or bond to the sulfobetaine polymer, and then the prepared hydrophilic aqueous solution is applied to cause the sulfobetaine polymer to react with or bond to the functional groups, thereby forming the hydrophilic coating 34. Thereafter, the wireless tag 10 with the hydrophilic coating formed on its surface is washed with water.

[0037] Instead of at least one dry treatment selected from plasma discharge treatment, corona discharge treatment, ultraviolet irradiation treatment, excimer irradiation treatment, electron beam irradiation treatment, and radiation irradiation treatment that is applied to the surface of the white resin layer 24 of the wireless tag 10, a molecular adhesive made of a silane coupling agent having vinyl groups and / or amino groups as functional groups on the side chains and / or ends is applied to the surface of the white resin layer 24, making the surface of the white resin layer 24 a modified surface to which the molecular adhesive adsorbs, reacts, or bonds, and then this modified surface is subjected to a surface treatment that generates functional groups that react with or bond to free sulfobetaine polymers, and then a prepared hydrophilic aqueous solution is applied to this surface-treated surface to react with or bond to the sulfobetaine polymers and the functional groups, thereby forming a hydrophilic coating 34.

[0038] Here, when a silane coupling agent having a vinyl group as a functional group at a side chain and / or terminal is used as the molecular adhesive, it is preferable that the modified surface formed by adsorption, reaction, or bonding of the silane coupling agent on the surface of the white resin layer 24 of the wireless tag 10 includes at least one dry treatment selected from plasma discharge treatment, corona discharge treatment, ultraviolet irradiation treatment, excimer irradiation treatment, electron beam irradiation treatment, and radiation irradiation treatment. This is preferable because a large number of functional groups that react with or bond to the sulfobetaine polymer can be generated on the surface of the white resin layer 24 of the wireless tag 10 modified with the silane coupling agent having a vinyl group as a functional group at a side chain and / or terminal.

[0039] Furthermore, by subjecting the surface of the white resin layer 24 of the wireless tag 10 to at least one dry treatment selected from plasma discharge treatment, corona discharge treatment, ultraviolet irradiation treatment, excimer irradiation treatment, electron beam irradiation treatment, and radiation irradiation treatment, and then applying a molecular adhesive, functional groups or free radicals generated on the dry-treated surface react with or bond to vinyl groups and / or amino groups as functional groups on the side chains and / or ends of the silane coupling agent of the molecular adhesive, thereby firmly bonding the surface of the white resin layer 24 of the wireless tag 10 and the molecular adhesive, which is preferable. Furthermore, after the sulfobetaine polymer reacts with or bonds to the functional groups, the wireless tag 10 having the hydrophilic coating 34 formed on its surface is washed with water.

[0040] When a molecular adhesive is used that is a mixture of a silane coupling agent having a vinyl group as a functional group on the side chain and / or terminal and a silane coupling agent having an amino group as a functional group on the side chain and / or terminal, it is preferable to apply at least one dry treatment selected from plasma discharge treatment, corona discharge treatment, ultraviolet irradiation treatment, excimer irradiation treatment, electron beam irradiation treatment, and radiation irradiation treatment to the modified surface formed by adsorption, reaction, or bonding of the silane coupling agent to the surface of the white resin layer 24 of the wireless tag 10, thereby imparting sufficient hydrophilicity to the surface of the wireless tag 10.

[0041] As the above-mentioned silane coupling agent, those having a functional group of a vinyl group and / or an amino group and having at least one functional group selected from the group consisting of a silanol group, a methoxy group, an ethoxy group, an azide group, an isocyanate group and an epoxy group in the same molecule can be suitably used.

[0042] The wireless tag 10 is immersed in a hydrophilic aqueous solution in which at least a portion of the free sulfobetaine polymer is dissolved in a soluble electrolyte, and the free sulfobetaine polymer and / or sulfobetaine polyelectrolyte salt is reacted with or bonded to functional groups to form a hydrophilic coating 34 on the surface of the wireless tag 10. In this case, the wireless tag 10 having the hydrophilic coating formed thereon is preferably washed with water to desalinate the water-soluble electrolyte and / or sulfobetaine polyelectrolyte salt applied to the surface of the wireless tag 10, thereby sufficiently removing the electrolyte component from the hydrophilic coating 34 and preventing the sulfobetaine polymer from eluting from the hydrophilic coating 34 due to rainwater during use of the wireless tag 10.

[0043] The above description has been given of a wireless tag 10 formed with an inlet portion 20 including a resin sealing portion 18 in which an antenna 14, a semiconductor element 12 equipped with a temperature sensor, and a conductive pattern 16 electrically connected to the antenna 14 are sealed, a protective layer 22 covering the inlet portion 20, and a white resin layer 24 containing white powder 24a that reflects sunlight and that covers the protective layer 22. However, the white resin layer 24 containing white powder 24a that reflects sunlight may also serve as the protective layer 22. Furthermore, the white resin layer 24 may be formed to cover the outer surface of the portion containing the temperature sensor to prevent a temperature rise in the portion containing the temperature sensor. The wireless tag 10 may also be provided with an optical sensor and / or humidity sensor that can obtain optical data of the light reception time and / or wavelength by the optical sensor, so that the optical data of the light reception time and / or wavelength and / or humidity data can be transmitted from the antenna 24 to a reader 28 as needed.

[0044] Examples of the present invention will be described in detail below, but the scope of the present invention is not limited to these examples.

[0045] Example 1 (1) For the wireless tag 10 shown in FIG. 1 , lower and upper protective layers of various colors were produced by compression molding using a mold with the following silicone resins into shapes with recesses of the same size as the inlet portion 20. "White": White silicone resin in which 2 parts by mass of titanium oxide with an average particle size (weight average method) of 0.1 to 10 μm as a white pigment was blended with the silicone resin. "Yellow": Yellow silicone resin in which 2 parts by mass of lead chromate as a yellow pigment was blended with the silicone resin. "Green": Yellow silicone resin in which 2 parts by mass of copper carbonate as a green pigment was blended with silicone rubber. "Gray": Gray silicone resin in which 0.3 parts by mass of titanium oxide as a white pigment and 0.1 parts by mass of carbon black as a black pigment were blended with silicone rubber. "Pink": Pink silicone resin in which 2 parts by mass of azo-based pink pigment was blended with silicone rubber. (2) A corona discharge treatment was performed on the inner surfaces of the lower and upper protective layers of various colors, except for the recessed portions. The inlet portion 20 was sandwiched between the treated lower and upper protective layers, inserted into each recessed portion, and adhesively sealed to the lower and upper protective layers by heating and pressurizing, thereby producing a wireless tag 10. (3) Temperature measurements were performed using wireless tags 10 whose outer surfaces were covered with lower and upper protective layers of various colors in a room that was not exposed to sunlight. A stationary UHF reader / writer (product name, UTR-SU01-3CH (product model number)) manufactured by Takaya Co., Ltd. was used as the reader, and a "Ondotori" (product name) manufactured by T&D Co., Ltd. was used as the reference thermometer. The results are shown in Table 2. The indoor temperature measured with the reference thermometer was constant at 25.6°C.

[0046]

[0047] As is clear from Table 2, in a room free from the influence of sunlight, there was almost no variation in the temperatures measured by the wireless tags 10 with different surface hues.

[0048] Example 2 Temperature measurements were carried out in a shaded location under sunny conditions using the wireless tags 10 of different colors and the reference thermometer used in Example 1. The results are shown in Table 3 below. The illuminance in the shade was 10,190 lux (lx).

[0049]

[0050] As is clear from Table 3, the temperature measured with the white-surfaced wireless tag 10 had the smallest temperature difference from the reference temperature. Furthermore, even in the shade, where the white-surfaced wireless tag 10 is somewhat affected by sunlight, the temperature difference was approximately the same as the result obtained indoors, where the white-surfaced wireless tag 10 is not affected by sunlight (Example 1).

[0051] Example 3 Using the same wireless tag 10 of a different color as in Example 2 and a reference thermometer, temperature measurements were carried out in a sunny location under sunlight on the same day as in Example 2. The results are shown in Table 4 below. The illuminance in the sun exceeded the measurement range (99,999 lux (lx)).

[0052]

[0053] As is clear from Table 4, even when exposed to direct sunlight, the temperature measured with the wireless tag 10 having a white surface had the smallest temperature difference from the reference temperature.

[0054] Example 4 The lower and upper protective layers of the wireless tag 10 used in Example 1 were molded from silicone resin blended with various white powders shown in Table 1. Next, under sunny conditions, the wireless tag 10 was placed in a sunny location, and a reference thermometer was placed in the shade to measure the temperature. The results are shown in Table 5 below.

[0055]

[0056] As is clear from Table 5, even when the white powder used was changed, the temperature difference between the temperature measured by the wireless tag 10 with a white surface placed in the sun and the reference temperature measured by the reference thermometer placed in the shade was approximately the same.

[0057] Example 5 (Hydrophilic Treatment) Using a white silicone rubber plate formed from the white silicone resin used in Example 1 and a gray silicone rubber plate formed from the gray silicone resin used in Example 1, a hydrophilic treatment was carried out to form a hydrophilic coating containing the following sulfobetaine polymer on the surface of each rubber plate. For the hydrophilic treatment, first, a 1.0 mass % sulfobetaine solution was prepared. This sulfobetaine solution contains at least a portion of the following sulfobetaine polymer dissolved in water at 80°C. In addition, each of the white silicone rubber plate and the gray silicone rubber plate was exposed to an integrated light intensity of 600 mJ / cm2 on one surface. ２ After irradiating with ultraviolet light having a wavelength of 220 to 410 nm so as to obtain a film thickness of 1.0 mass %, the film was immersed in a prepared 1.0 mass % sulfobetaine solution at 80° C. for 1 minute, washed with ion-exchanged water, and then dried.

[0058] (Evaluation of Hydrophilicity) Each hydrophilically treated rubber plate was left outdoors for 14 days, and the change in contact angle over time was measured by the sessile drop method using an automatic contact angle meter (product number DM-501, manufactured by Kyowa Interface Science Co., Ltd.) The contact angle of a liquid droplet on the hydrophilically treated surface of each hydrophilically treated rubber plate was 5° or less, which was unmeasurable, throughout the 14 days, demonstrating hydrophilicity with good weather resistance.

[0059] Example 6: The wireless tag 10 coated with the white silicone resin (containing titanium oxide) used in Example 1 was subjected to the hydrophilic treatment performed in Example 5. Next, under sunny conditions, the wireless tag 10 coated with the white silicone that had been hydrophilically treated and the wireless tag 10 coated with the white silicone that had not been hydrophilically treated were placed in sunny locations, and a reference thermometer was placed in the shade to measure the temperature. The results are shown in Table 6 below.

[0060]

[0061] As is clear from Table 6, the measured temperatures of the wireless tag 10 coated with white silicone resin placed in the sun were similar regardless of whether or not the tag was hydrophilic, indicating that the hydrophilic treatment does not affect the suppression of temperature rise in the wireless tag 10. Therefore, by performing the hydrophilic treatment on the wireless tag 10 coated with white silicone resin, it is possible to suppress the temperature rise of the wireless tag 10 while also achieving an anti-fouling effect.

[0062] The wireless tag with temperature sensor function of the present invention can wirelessly transmit temperature data that is as close as possible to the ambient temperature, even when installed in a sunny location where sunlight is irradiated, and therefore can be used in agricultural applications where the tag is frequently exposed to sunlight.

[0063] 10: wireless tag, 11: substrate, 12: semiconductor element, 14: antenna, 16: conductive pattern, 18a: protective layer, 18b, 18c: adhesive layers, 20: inlet portion, 22a: lower protective layer not containing white powder, 22b: lower protective layer not containing white powder, 24: white resin coating, 24a: lower protective layer containing white powder, 24b: lower protective layer containing white powder, 24p: white powder, 26: hole, 28: leader, 30: string, 32: mango, 34: hydrophilic coating

Claims

1. A wireless tag with a temperature sensor function, which includes an antenna that receives wireless instructions from a reader outside the wireless tag or transmits wireless signals to the reader, the semiconductor element that wirelessly transmits temperature data measured by the temperature sensor from the antenna to the reader in response to wireless instructions from the reader received by the antenna, and a conductive pattern that electrically connects the semiconductor element and the antenna, and which is characterized in that when sunlight is irradiated onto the wireless tag, the outer surface of the part containing the temperature sensor is covered with a white resin layer containing white powder so that the sunlight is reflected and the temperature of at least the part containing the temperature sensor can be suppressed from rising.

2. A wireless tag with a temperature sensor function as described in claim 1, characterized in that the white powder is one or more selected from the group consisting of titanium oxide, alumina, barium sulfate, magnesium oxide, zinc oxide and calcium carbonate.

3. The wireless tag with temperature sensor function according to claim 1, wherein the thickness of the white resin layer is 200 μm or more.

4. The wireless tag with temperature sensor function according to claim 1, wherein the white powder has an average particle size of 0.1 to 10 μm as measured by the weight average method.

5. The wireless tag with temperature sensor function according to claim 1, characterized in that the amount of the white powder is 1 to 30 parts by mass relative to the resin forming the white resin layer.

6. The wireless tag with temperature sensor function according to claim 1, characterized in that the white resin layer reflects 80% or more of the light of wavelengths of 300 to 800 nm of the irradiated sunlight.

7. The wireless tag with temperature sensor function according to claim 1, wherein the resin forming the white resin layer is silicone rubber.

8. The wireless tag with temperature sensor function according to claim 1, wherein the entire outer peripheral surface of the wireless tag is covered with the white resin layer.

9. The wireless tag with temperature sensor function according to claim 1, wherein the outer surface of the white resin layer is covered with a hydrophilic coating.

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