Flexible sensor module and method of manufacturing the same

Abstract

To provide a flexible sensor module having improved adhesion between a print layer and a base material sheet, and to provide a method of manufacturing the same.SOLUTION: The flexible sensor module includes: a base material sheet containing a silicone rubber as a main agent and an amphipathic substance compatible with the silicone rubber as an additive; and a print layer formed on at least one surface of the base material sheet; wherein the amphipathic substance is a reaction product of a first additive and a second additive, the first additive is a methyl silicate oligomer, the second additive is a compound having a dimethylpolysiloxane skeleton and a terminal alkoxy group, and the print layer is formed of a cured product of a conductive ink for screen printing and forms at least one detection electrode constituting a sensor.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flexible sensor module including silicone rubber and a method for manufacturing the same. [Background technology]

[0002] Conventionally, flexible sensor modules using silicone rubber as a base sheet have been proposed (see, for example, Patent Document 1). However, when a printing layer is formed by depositing ink or paint on the surface of silicone, which has low surface free energy, there is a problem in that it is difficult to ensure adhesion between the base and the printing layer. To solve this problem, a method is known in which the surface of the base sheet is activated to improve adhesion (see, for example, Patent Document 2). However, this process is complicated, and there are problems such as the effectiveness of the surface treatment gradually decreasing over time.

[0003] Meanwhile, a method is known in which the hydrophilicity of a substrate sheet is enhanced by adding a hydrophilic group-containing compound made of polyether-modified silicone oil to the silicone rubber, which is the main component of the substrate sheet (see, for example, Patent Document 3). However, this method requires the use of a separate dry surface treatment process, and there are problems in that the adhesion of the printing layer is not sufficiently improved by adding the compound alone.

[0004] Incidentally, polyalkoxysiloxane compounds (especially tetramethoxysilane having four methoxy groups, which are more reactive than ethoxy groups) obtained by partial hydrolysis and condensation of low-molecular-weight alkoxysilanes having alkoxy groups have been used for purposes such as making powder surfaces hydrophilic (e.g., Patent Documents 4 and 5).

[0005] Furthermore, compounds having a dimethylpolysiloxane skeleton are used as water-repellent-imparting components that have affinity for silicone rubber (see, for example, Patent Documents 6 and 7). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-113851 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-181407 [Patent Document 3] International Publication No. 2020 / 137065 [Patent Document 4] International Publication No. 1998 / 036016 [Patent Document 5] Japanese Patent Application Laid-Open No. 2002-265924 [Patent Document 6] Japanese Patent Publication No. 2022-008048 [Patent Document 7] Japanese Patent Publication No. 2023-054516 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a flexible sensor module with improved adhesion between a printing layer and a base sheet, and a method for manufacturing the same. [Means for solving the problem]

[0008] [1] A flexible sensor module comprising: a base sheet containing silicone rubber as a main component and an amphiphilic substance compatible with the silicone rubber as an additive; and a printed layer formed on at least one surface of the base sheet, wherein the amphiphilic substance is a reaction product of a first additive and a second additive, the first additive being a methyl silicate oligomer, and the second additive being a compound having a dimethylpolysiloxane skeleton and terminal alkoxy groups; the printed layer being made of a cured product of a conductive ink for screen printing, and forming at least one detection electrode that constitutes a sensor. [2] The silicone rubber is a thermosetting liquid silicone rubber that is an addition curing type silicone rubber, or a millable silicone rubber that is a peroxide curing type or an addition curing type. [1] The flexible sensor module according to [1]. [3] The flexible sensor module according to [1] or [2], wherein the first additive is a partially hydrolyzed oligomer of tetramethoxysilane, the SiO2 content of which is 50 to 60 mass %, and the degree of polymerization of which is 2 to 200, the methylsilicate oligomer is soluble in the silicone rubber but not reactive with the silicone rubber, and the amphiphilic substance has silanol groups, at least a part of which is exposed on the surface of the base sheet. [4] A flexible sensor module according to any one of [1] to [3], wherein the Si atom at one end of the dimethylpolysiloxane skeleton in the second additive is bonded to three functional groups, two of which are methyl groups, and the remaining one is a methyl group or any monovalent organic group bonded via an ether group; the Si atom at the other end is bonded to three functional groups, one of which is a methoxy group bonded via an optional methylene group (-CH2-) and the remaining two are functional groups each arbitrarily selected from a methoxy group and a methyl group; and the second additive is soluble in the silicone rubber but not reactive with the silicone rubber. [5] A flexible sensor module according to any one of [1] to [4], wherein the base sheet contains 5 to 20 parts by mass of the first additive and the second additive in total per 100 parts by mass of the silicone rubber, and the content ratio expressed as the second additive / the first additive is 0.2 to 0.4 by weight. [6] The flexible sensor module according to any one of [1] to [5], wherein the conductive ink for screen printing is a carbon ink containing graphite and carbon black, ethylene glycol, a first polyvinylpyrrolidone, a second polyvinylpyrrolidone, a third polyvinylpyrrolidone, and a thermally reactive water-based urethane resin having a blocked isocyanate group and a urethane skeleton, the first to third polyvinylpyrrolidones having different molecular structures from one another, the first polyvinylpyrrolidone having only repeating units derived from vinylpyrrolidone in its molecular structure, the second polyvinylpyrrolidone having repeating units derived from vinylpyrrolidone and repeating units derived from an α-olefin having 3 to 6 carbon atoms, and the third polyvinylpyrrolidone is a copolymer of polyvinylpyrrolidone and polyvinyl alcohol, and a three-dimensional crosslinked structure is formed in the cured product of the conductive ink for screen printing by isocyanate groups formed by unblocking the blocked isocyanate groups. [7] A flexible sensor module according to any one of [1] to [6], wherein when the contact angle on the surface of the base sheet is measured in accordance with JIS R3257:1999 (Test method for wettability of substrate glass surfaces: sessile drop method), the contact angle is 80° or less for water and 80° or less for ethylene glycol. [8] The flexible sensor module according to any one of [1] to [7], wherein the base sheet is transparent or translucent. [9] A method for manufacturing a flexible sensor module, comprising the steps of: blending a first additive and a second additive into a raw material of silicone rubber, which is a main component; kneading and stirring the mixture; and curing the mixture into a sheet while heating to obtain a base sheet; and screen-printing a conductive ink for screen printing on at least one surface of the base sheet to form at least one detection electrode that constitutes a sensor, wherein the first additive is a methyl silicate oligomer, and the second additive is a compound having a dimethylpolysiloxane skeleton and a terminal alkoxy group, and the first additive and the second additive react to form an amphiphilic substance that is compatible with the silicone rubber when obtaining the base sheet.

[10] The method for manufacturing a flexible sensor module according to [9], wherein the conductive ink for screen printing does not contain silicone having a dimethylsiloxane skeleton and uses ethylene glycol as the main solvent. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a flexible sensor module in which the adhesion between the printing layer and the base sheet is improved, and a method for manufacturing the same.

[0010] This invention is believed to contribute to SDG Goal 12, "Responsible Consumption and Production." [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph showing the contact angle of water measured over time on the surface of the substrate sheet produced in each example. [Figure 2] 1 is a graph showing the contact angle of ethylene glycol measured over time on the surface of the substrate sheet produced in each example. [Figure 3] Photographs showing the results of tests on the adhesion of the printed layer in the sheets with printed layers produced in each example, and evaluation of the results. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Flexible sensor module> A first aspect of the present invention is a flexible sensor module comprising a base sheet containing silicone rubber as a main component and an amphiphilic substance compatible with the silicone rubber as an additive, and a printed layer formed on at least one surface of the base sheet.

[0013] <Base sheet> The shape and thickness of the substrate sheet of this embodiment are not particularly limited, and are set appropriately depending on the application of the flexible sensor module.

[0014] [Silicone rubber raw materials] The silicone rubber raw material used in this embodiment is a material that becomes silicone rubber after curing, and can be appropriately selected from known silicone rubber compounds, silicone raw rubber, liquid silicone rubber, etc. that are used in the manufacture of silicone rubber molded products. One type of silicone rubber raw material may be used alone, or two or more types may be used in combination. An example of the silicone rubber compound is KE951U (product name of Shin-Etsu Chemical Co., Ltd.). Examples of silicone raw rubber include KE76VBS (product name of Shin-Etsu Chemical Co., Ltd.), KE77VBS (product name of Shin-Etsu Chemical Co., Ltd.), KE78VBS (product name of Shin-Etsu Chemical Co., Ltd.), KE79VBS (product name of Shin-Etsu Chemical Co., Ltd.), and KE80VB (product name of Shin-Etsu Chemical Co., Ltd.). An example of the liquid silicone rubber is KE-1950-70A / B (product name of Shin-Etsu Chemical Co., Ltd.).

[0015] The silicone rubber raw material is preferably a thermosetting liquid silicone rubber, which is an addition-curing type silicone rubber, or a millable silicone rubber, which is a peroxide-curing type or an addition-curing type.

[0016] The content of the silicone rubber material relative to the total mass of the base sheet is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more. Since the base sheet contains additives described below, the content of the silicone rubber material may be part or all of the remainder excluding the additives. Within the above range, a flexible sensor module with excellent rigidity and elasticity is obtained.

[0017] [First additive] The first additive is a methyl silicate oligomer. The silicate oligomer generally has the formula A: [—Si(OR)—O—] m It is an oligomer having a linear skeleton represented by the formula: In formula A, R represents a methyl group or an ethyl group, and m represents an integer of 2 to 300, preferably 2 to 200.

[0018] The first additive of this embodiment is preferably a methyl silicate oligomer in which R is a methyl group, and more preferably a methyl silicate oligomer represented by the following formula A-1. In the following formula A-1, m is the same as above. The SiO2 content of the first additive is preferably 40 to 70 mass%, more preferably 45 to 65 mass%, and even more preferably 50 to 60 mass%. The first additive is preferably soluble in the raw materials of the silicone rubber but not reactive with the silicone rubber. A specific example of a preferred first additive is a partially hydrolyzed oligomer of tetramethoxysilane (TMOS) manufactured by Mitsubishi Chemical Corporation.

[0019] [ka]

[0020] [Second additive] The second additive is a compound having a dimethylpolysiloxane skeleton and an alkoxy group at at least one of its terminals. The dimethylpolysiloxane skeleton is generally represented by the formula B: [—Si(—CH3)2—O—] nIn formula B, n is a desired integer of 2 or more, and is adjusted according to the desired viscosity. The second additive is preferably one that is soluble in the raw materials of the silicone rubber but does not have reactivity with the silicone rubber.

[0021] The second additive is more preferably a linear dimethylpolysiloxane compound represented by the following formula B-1: In the formula, R1 to R3 each independently represent a hydrogen atom or any monovalent organic group (preferably an alkyl group having 1 to 2 carbon atoms). n in the following formula B-1 is the same as above.

[0022] [ka]

[0023] Of the two ends of the linear dimethylpolysiloxane skeleton of the second additive, the Si atom at one end is bonded to three functional groups, two of which are methyl groups, and the remaining one is preferably any monovalent organic group (excluding alkoxy groups) or a methyl group. The Si atom at the other end is bonded to three functional groups, one of which is a methoxy group bonded via an optional methylene group (-CH-), and the remaining two are preferably functional groups arbitrarily selected from methoxy groups and methyl groups. Here, "optionally intervening a methylene group" means that the bond may be via an intermediate methylene group, or may be a single bond without an intermediate methylene group.

[0024] The second additive is preferably a compound having a so-called terminal alkoxy group from the viewpoint of controlling reactivity and achieving a balance between the hydrophilic and hydrophobic moieties in the molecule of the reaction product. A specific example of a preferred second additive is a one-terminated alkoxy-modified silicone oil (KR-4000A) manufactured by Shin-Etsu Silicone Co., Ltd.

[0025] In the substrate sheet of this embodiment, the total content of the first additive and the second additive per 100 parts by mass of silicone rubber is preferably 5 to 20 parts by mass, more preferably 7 to 15 parts by mass, and even more preferably 9 to 12 parts by mass. When the content is at least as large as the lower limit of the above range, the adhesion of the printing layer can be further improved. When the content is equal to or less than the upper limit of the above range, the physical properties of the silicone rubber are sufficiently maintained, and a substrate that is flexible and has excellent chemical resistance can be obtained.

[0026] Furthermore, the content ratio expressed as (second additive / first additive) is preferably 0.2 to 0.4 by weight, which can further improve the adhesion of the printing layer.

[0027] [Amphiphilic substances] It is believed that the first and second additives are first hydrolyzed as represented by the following reaction formula while being compatible with the silicone rubber during the stage of forming the substrate sheet.

[0028] [ka]

[0029] Next, the above hydrolysates undergo dehydration condensation with each other, forming an amphiphilic substance having both hydrophilic and hydrophobic parts in the molecule as a reaction product, as represented by the following structural formula C-1.

[0030] [ka]

[0031] It is believed that at least a portion of the amphiphilic substance has its hydrophilic portion exposed on the surface of the substrate sheet and its hydrophobic portion embedded in the silicone rubber during the formation of the substrate sheet. In other words, the silanol groups (Si-OH) of the hydrophilic portion of the amphiphilic substance are exposed on the surface of the sheet. When an ink containing an isocyanate group is then printed on the surface of the formed substrate sheet, the hydroxyl groups of the silanol groups on the surface of the substrate sheet are thought to react with the isocyanate group to form a urethane bond. This process can be represented by the following formula D-1. In the formula, R6 represents the chemical structure of any compound containing an isocyanate group contained in the ink.

[0032] [ka]

[0033] [Contact angle] When the contact angle on the surface of the substrate sheet of this embodiment is measured in accordance with JIS R3257:1999 (testing method for wettability of substrate glass surfaces: sessile drop method), it is preferable that the contact angle for water is 80° or less and the contact angle for ethylene glycol is 80° or less. The contact angle can be measured at any time after the formation of the base sheet, and is preferably measured, for example, one to two days after production. It is preferable to measure the contact angle several days after production rather than immediately after production, because the surface condition of the base sheet becomes more stable. A low contact angle increases the wettability of the ink to the substrate sheet, thereby enabling the adhesion of the printed layer to be further improved.

[0034] [Light transparency] From the viewpoint of being applicable to a variety of uses, the substrate sheet of this embodiment is preferably transparent or translucent. Here, "transparent or translucent" means that the light transmittance measured in accordance with JIS K7136:2000 is 50% or more.

[0035] <Print layer> The print layer of this embodiment is made of a cured product of a conductive ink for screen printing, and forms at least one detection electrode that constitutes the sensor.

[0036] [Conductive ink for screen printing] Hereinafter, the conductive ink for screen printing may be simply referred to as “ink.” Examples of ink materials include a solvent, a binder component, and conductive particles.

[0037] Examples of the solvent include methanol, ethanol, propanol, isopropanol, butanol, secondary butanol, amyl alcohol, 2-ethylhexanol, cyclohexanol, phenol, ethylene glycol, 1,3-butanediol, 1,4-butanediol, glycerin, diacetone alcohol, formic acid, acetic acid, propionic acid, glycol ether, diethylene glycol, triethylene glycol, hexamethylene glycol, polyethylene glycol 400, 2,2-thiodiethanol, γ-butyrolactone, and milk. Examples of solvents include ethyl acetate, methylcyclohexanone, dichloromethane, dichloroethane, chloroform, 2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), N-vinyl-2-pyrrolidone, butylamine, cyclohexylamine, aniline, ethylenediamine, pyridine, morpholine, 2-aminoethanol, diethanolamine, triethanolamine, aminoethylethanolamine, 2-hydroxyethylmorpholine, 2-amino-2-methyl-1-propanol, nitromethane, nitroethane, and dimethyl sulfoxide. Water may also be contained as a solvent. The ink material may contain one or more solvents.

[0038] Among the above solvents, ethylene glycol is preferred because it is easy to sufficiently disperse the conductive particles and binder components to form an ink suitable for high-resolution screen printing, and it also has good wettability to the surface of the substrate sheet of this embodiment, resulting in excellent adhesion between the printed layer formed after drying and curing and the substrate sheet.

[0039] Examples of binder components include polyvinylpyrrolidone, polyester resins, acrylic resins, and cellulose resins. The ink material may contain one or more binder components. From the viewpoint of improving printability, it is preferable that the ink material does not contain silicone having a dimethylsiloxane skeleton.

[0040] When polyvinylpyrrolidone (PVP) is contained as a binder component, it is preferable to contain two or more types of polyvinylpyrrolidone having different molecular structures from the viewpoint of increasing the strength of the printed layer.

[0041] Preferred examples of polyvinylpyrrolidones include a "first polyvinylpyrrolidone" having only repeating units derived from vinylpyrrolidone in its molecular structure, a "second polyvinylpyrrolidone" having repeating units derived from vinylpyrrolidone and repeating units derived from an α-olefin having 3 to 6 carbon atoms, and a "third polyvinylpyrrolidone" which is a copolymer of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0042] Examples of the first polyvinylpyrrolidone include unmodified PVPs manufactured by Ashland, such as K-120 and K-90. An example of the second polyvinylpyrrolidone is P-904LC, an alkylated polyvinylpyrrolidone manufactured by Ashland. An example of the third polyvinylpyrrolidone is Pitzcol V-7154, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., which is a PVA-PVP graft copolymer in which polyvinylpyrrolidone is grafted onto polyvinyl alcohol.

[0043] A preferred combination of polyvinylpyrrolidones is one or more types arbitrarily selected from the above first to third polyvinylpyrrolidones, more preferably two or more types, and even more preferably three types (i.e., including all of the first to third polyvinylpyrrolidones).

[0044] Examples of conductive particles include particles made of carbon particles, silver or silver compounds, copper or copper compounds, aluminum, nickel, etc. The conductive particles may be particles made of one type of material, or may have a core-shell structure made of multiple materials.

[0045] When carbon particles are used as conductive particles, it is preferable to use a combination of two or more types of carbon particles. For example, when both graphite powder and Ketjen black (carbon black) are used, the difference in particle shape between them can be utilized to easily form wiring patterns and detection electrodes with excellent conductivity.

[0046] The ink preferably contains a thermally reactive water-based urethane resin with a urethane skeleton and a blocked isocyanate group. The resin forms a urethane bond, such as the structural formula D-1, and can further enhance adhesion between the printed layer and the substrate surface. An example of such a thermally reactive water-based urethane resin is Elastron H-15, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

[0047] The content of the solvent relative to the total mass of the ink is preferably 40 to 70 mass%. When the ink contains ethylene glycol as a solvent, the content of ethylene glycol relative to the total mass of the ink is preferably 30 to 60 mass%, more preferably 40 to 60 mass%, and even more preferably 50 to 60 mass%. When the content is within the above range, the conductive particles and binder components are sufficiently dispersed, making it easy to prepare an ink suitable for high-resolution screen printing, and the ink has good wettability to the surface of the substrate sheet of this embodiment, and the adhesion between the printed layer formed after drying and curing and the substrate sheet is also excellent.

[0048] The content of the binder component relative to the total mass of the ink is preferably 1 to 40% by mass. When one or more of the first to third polyvinylpyrrolidones described above are included as the binder component, the total content thereof relative to the total mass of the ink is preferably 5 to 30% by mass, more preferably 7 to 20% by mass, and even more preferably 9 to 15% by mass. When the content is within the above range, it is easy to prepare an ink suitable for high-resolution screen printing, the ink has good wettability to the surface of the substrate sheet of this embodiment, and the ink has excellent adhesion between the printed layer formed after drying and curing and the substrate sheet.

[0049] The content of conductive particles relative to the total mass of the ink is preferably 1 to 50 mass%. When the ink contains one or more types of carbon particles such as carbon black, the total content is preferably 10 to 40 mass% relative to the total mass of the ink, more preferably 20 to 35 mass%, and even more preferably 25 to 30 mass%. When the content is within the above range, it is easy to prepare an ink suitable for high-resolution screen printing, the ink has good wettability to the surface of the substrate sheet of this embodiment, and the ink has excellent adhesion between the printed layer formed after drying and curing and the substrate sheet.

[0050] When the ink contains the thermally reactive water-based urethane resin, the content of the nonvolatile matter is, for example, preferably 0.1 to 10 mass %, more preferably 1.0 to 5.0 mass %, and even more preferably 2.0 to 3.0 mass %, relative to the total mass of the ink. When the content is within the above range, it is easy to prepare an ink suitable for high-resolution screen printing, the ink has good wettability to the surface of the substrate sheet of this embodiment, and the adhesion between the printed layer formed after heat curing and the substrate sheet is particularly excellent.

[0051] [Detection electrode] The detection electrodes formed by the print layer of this embodiment constitute sensors, such as known capacitance touch sensors (e.g., JP 2023-22590 A) and strain sensors (e.g., JP 2023-116138 A). The printed layer of this embodiment preferably forms one or more wirings associated with the detection electrodes. The printed layer of this embodiment may also be referred to as a conductive pattern.

[0052] ≪Manufacturing method≫ A second aspect of the present invention is a method for manufacturing a flexible sensor module, comprising the steps of: blending a first additive and a second additive into a raw material of silicone rubber as a main component, kneading and stirring the mixture, and then curing the mixture into a sheet while heating to obtain a base sheet (base sheet preparation step); and screen-printing a conductive ink for screen printing onto at least one surface of the base sheet to form at least one detection electrode that constitutes a sensor (printing step). By this aspect, the flexible sensor module of the first aspect can be manufactured.

[0053] [Base sheet production process] The silicone rubber raw material, the first additive, and the second additive used in this step are as described in the first embodiment. It is preferable to mix the respective materials in the suitable ratios described in the first embodiment. The material composition obtained by blending, kneading, and stirring the various materials may be formed into a sheet by a desired molding method and cured. During curing, the material composition is preferably heated to promote hydrolysis of the first additive and the second additive. The material composition may also contain additives other than the silicone rubber raw materials, the first additive, and the second additive.

[0054] [Printing process] The method for screen-printing the conductive ink for screen printing onto at least one surface of the substrate sheet is not particularly limited, and any known screen printing method can be used. A printing plate having a pattern of the detection electrodes and wiring to be formed is used. [Example]

[0055] [Preparation of base sheet] The materials were mixed in a mixer using the formulation shown in Table 1, and then a 0.35 mm thick PET frame was placed between two flat metal plates, with the mixed material sandwiched between the frame. The mixture was then cured at 135°C for 5 minutes to obtain a 0.35 mm thick silicone rubber substrate sheet.

[0056] [Table 1]

[0057] The details of each material listed in Table 1 are as follows: Main ingredient: Silicone rubber (Shin-Etsu Chemical Co., Ltd.) First additive: Methyl silicate oligomer (Mitsubishi Chemical Corporation; partially hydrolyzed oligomer of tetramethoxysilane (TMOS); SiO2 content = 58.0 ± 1.0%; TMOS content = 0.2% or less; degree of polymerization = 2 to 200) Second additive: A compound with a dimethylpolysiloxane skeleton and a terminal alkoxy group (Shin-Etsu Silicone Co., Ltd.; terminal alkoxy-modified silicone oil; KR-4000A) In the formulations in Table 1, the weight ratio represented by second additive / first additive was set in the range of 0.2 to 0.4.

[0058] <Contact angle evaluation> The water contact angle of the surface of the substrate sheet prepared in each of the above examples was measured using ion-exchanged water in accordance with JIS R3257:1999 (Test method for wettability of substrate glass surfaces: sessile drop method). Five measurements (n=5) were taken for each substrate sheet, and the average value was calculated. The water contact angle was measured every day starting immediately after the preparation of each substrate sheet (day 0), and the changes over time were investigated. The results are shown in the graph in Figure 1.

[0059] The change in contact angle over time was investigated using ethylene glycol instead of water, with reference to the JIS standard. Five measurements (n=5) were taken for each substrate sheet, and the average value was calculated. The contact angle was measured every 1000 milliseconds, starting immediately after ethylene glycol was dropped onto the surface of each substrate sheet (0 milliseconds), and the results of the change over time are shown in the graph in Figure 2.

[0060] From the above, it was found that Substrate 3, which contained the first additive and the second additive, was more hydrophilic than Substrate 1, which did not contain the first additive or the second additive. On the other hand, Substrate 3 was less hydrophilic than Substrate 2, which contained only the first additive, especially within one day after production. Considering the overall picture, it was found that the affinity (i.e., hydrophilicity) for ink containing a hydrophilic substance such as ethylene glycol was in the following order: Substrate 1 << Substrate 3 < Substrate 2.

[0061] [Ink preparation] Inks 1 to 3 were obtained by mixing the materials according to the formulations in Table 2. The numerical values ​​indicating the blend amounts in the table are in grams (g).

[0062] [Table 2]

[0063] The details of each material listed in Table 2 are as follows: Main resin: Polyvinylpyrrolidone (Ashland, unmodified PVP, model number: K-120, K value of 1% viscosity solution = 114-130, absolute molecular weight measured by GPC / MALS: 3,470,000, Tg: 176°C) Dispersant: Alkylated polyvinylpyrrolidone (Ashland Corporation, copolymer consisting of 90% repeating units derived from vinylpyrrolidone and 10% repeating units derived from 1-butene, model number: P-904LC, Tg: 155°C, water soluble) Polyol: PVA-PVP graft copolymer (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., a water-soluble polymer in which polyvinyl alcohol is grafted with polyvinylpyrrolidone, model number: Pitzcol V-7154) Urethane curing agent: a thermally reactive water-based urethane resin with a urethane skeleton and a blocked isocyanate group (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., model number: Elastron H-15, non-volatile content 27.0 to 29.0% by mass) Catalyst: Dibutyltin dilaurate (DBTDL) Conductive particles: graphite powder (manufactured by Nippon Graphite Co., Ltd., model number: CSP-E, shape: scaly, average particle size 8 μm) Conductive particles: Ketjenblack (manufactured by Lion Specialty Chemicals, model number: Carbon ECP, average primary particle size 30 nm)

[0064] [Preparation of sheet with printed layer] Using inks 1 to 3, wiring patterns were screen-printed on the above sheets of substrates 1 to 3 with a 325 mesh, and then dried at 150°C for 30 minutes to obtain sheets with a printed layer made of the cured product of each ink. The combinations of ink and substrate were as shown in Table 3.

[0065] [Table 3]

[0066] <Evaluation of Adhesion> The adhesion of the printed layer to the surface of the substrate sheet was evaluated visually for the sheets with printed layer obtained in each example and by an adhesive tape peeling test in accordance with JIS K5600-5-6:1999 (general testing method for paints: cross-cut method). As a result, as shown in Figure 3, peeling was observed in the printed layers (coatings) of Comparative Examples 1 to 4, indicating low adhesion, whereas no peeling was observed in the printed layer (coating) of Example 1, indicating high adhesion.

[0067] From the above, it is clear that the flexible sensor module of the present invention, in which the detection electrode is a printed layer made of a cured product of an ink containing a heat-reactive curing agent having a blocked isocyanate group on a sheet made of a base material 3 containing a first additive and a second additive, has high adhesion of the detection electrode to the silicone rubber base material sheet.

Claims

1. a substrate sheet containing a silicone rubber as a main component and an amphiphilic substance compatible with the silicone rubber as an additive; a printed layer formed on at least one surface of the base sheet, the amphiphile is a reaction product of a first additive and a second additive; the first additive is a methyl silicate oligomer; the second additive is a compound having a dimethylpolysiloxane skeleton and an alkoxy group at one end, the printed layer is made of a cured product of a conductive ink for screen printing and forms at least one detection electrode that constitutes a sensor; A flexible sensor module, wherein a three-dimensional cross-linked structure is formed in the printed layer by isocyanate groups obtained by unblocking the blocked isocyanate groups contained in the conductive ink for screen printing.

2. The silicone rubber is a thermosetting liquid silicone rubber, which is an addition curing type silicone rubber, or a millable silicone rubber, which is a peroxide curing type or an addition curing type. The flexible sensor module according to claim 1 .

3. The first additive is a partially hydrolyzed oligomer of tetramethoxysilane, and its SiO ２ The content is 50 to 60 mass % and the degree of polymerization is 2 to 200, the methyl silicate oligomer has solubility in the silicone rubber but does not have reactivity with the silicone rubber, the amphiphilic substance has silanol groups, and at least a portion of the silanol groups are exposed on the surface of the base sheet; The flexible sensor module according to claim 2 .

4. One end and the other end of the dimethylpolysiloxane skeleton in the second additive the Si atom at one end is bonded to three functional groups, two of which are methyl groups, and the remaining one is any monovalent organic group (excluding an alkoxy group) or a methyl group; The Si atom at the other end is bonded to three functional groups, one of which is a methylene group (-CH ２ the other two are functional groups each arbitrarily selected from a methoxy group and a methyl group; the second additive is soluble in the silicone rubber but not reactive with the silicone rubber; The flexible sensor module according to claim 3 .

5. In the base sheet, the first additive and the second additive are contained in a total amount of 5 to 20 parts by mass per 100 parts by mass of the silicone rubber, and The content ratio of the second additive to the first additive is 0.2 to 0.4 by weight. The flexible sensor module according to claim 4 .

6. the conductive ink for screen printing is a carbon ink containing graphite and carbon black, ethylene glycol, a first polyvinylpyrrolidone, a second polyvinylpyrrolidone, a third polyvinylpyrrolidone, and a thermally reactive water-based urethane resin having a blocked isocyanate group and a urethane skeleton; the first to third polyvinylpyrrolidones have molecular structures different from one another, the first polyvinylpyrrolidone has only repeating units derived from vinylpyrrolidone in its molecular structure, the second polyvinylpyrrolidone has a repeating unit derived from vinylpyrrolidone and a repeating unit derived from an α-olefin having 3 to 6 carbon atoms; the third polyvinylpyrrolidone is a copolymer of polyvinylpyrrolidone and polyvinyl alcohol; In the cured product of the conductive ink for screen printing, a three-dimensional crosslinked structure is formed by the isocyanate groups obtained by unblocking the blocked isocyanate groups. The flexible sensor module according to claim 5 .

7. When the contact angle on the surface of the base sheet is measured in accordance with JIS R3257:1999 (Test method for wettability of substrate glass surfaces: sessile drop method), the contact angle for water is 80° or less, and the contact angle for ethylene glycol is 80° or less. The flexible sensor module according to claim 5 .

8. The flexible sensor module according to claim 5 , wherein the base sheet is transparent or translucent.

9. a step of blending a first additive and a second additive into a raw material of silicone rubber as a main component, kneading and stirring the mixture, and then curing the mixture into a sheet while heating to obtain a substrate sheet; and screen-printing a conductive ink for screen printing on at least one surface of the base sheet to form at least one detection electrode constituting the sensor. A method for manufacturing a flexible sensor module, comprising: the first additive is a methyl silicate oligomer; the second additive is a compound having a dimethylpolysiloxane skeleton and an alkoxy group at one end, when the base sheet is obtained, the first additive and the second additive react to form an amphiphilic substance that is compatible with the silicone rubber; the conductive ink for screen printing contains a blocked isocyanate group; A method for manufacturing a flexible sensor module, wherein a three-dimensional cross-linked structure is formed in the detection electrode by the isocyanate groups obtained by unblocking the blocked isocyanate groups.

10. The method for manufacturing a flexible sensor module according to claim 9 , wherein the conductive ink for screen printing does not contain silicone having a dimethylsiloxane skeleton, and contains ethylene glycol as a main solvent.

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