Stacked lithium-ion secondary battery and method for measuring shear adhesion strength of tape

Abstract

To provide a stacked lithium-ion secondary battery in which even if being used at high temperatures, shrinkage of a separator can be prevented and a short circuit between positive and negative electrodes can be prevented.SOLUTION: A tape adhered from a front surface to a rear surface of an electrode group across a side surface thereof includes a base material made of a synthetic resin and an adhesive layer fixed to the base material, and a ratio (c / A) of a maximum value (a) of a shear adhesion strength at 0°C to a maximum value (c) of the shear adhesion strength at 130°C is 1.8 or more. In a method for measuring the shear adhesion strength, a test piece 70 with a width of 10 mm and a length of 50 mm or more is used; 10 mm of one end portion in a longitudinal direction is adhered to one surface of a metal plate 82 fixed on a base 81; the other end portion in the longitudinal direction is attached to a chuck 83 of a tensile testing machine; a tensile testing is performed while the length of an intermediate portion 72 is set to 30 mm; and the highest tensile strength shown during testing is measured as a shear adhesion strength [N / 10 mm].SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a laminated lithium ion secondary battery and a method for measuring the shear adhesive strength of a tape. [Background technology]

[0002] Lithium-ion secondary batteries have traditionally been used as power sources for a wide range of electronic devices, including portable devices, electric vehicles, homes, drones, robots, and storage batteries for commercial facilities. Lithium-ion secondary batteries for drones, in particular, are required to have both high power density and high energy density. However, achieving both of these properties with current lithium-ion secondary batteries can lead to deterioration in cycle characteristics and battery swelling, so improved reliability is also required.

[0003] A stacked lithium-ion secondary battery includes an electrode group in which multiple positive and negative electrode plates are alternately stacked with separators interposed therebetween, and an exterior housing to house the electrode group, with the electrode group sealed within the exterior housing and positive and negative terminals extending to the outside of the exterior housing. In stacked lithium-ion secondary batteries, in order to prevent the electrode plates (positive and negative electrode plates) in the electrode group from shifting position, tape is applied from the front surface of the electrode group across the side surfaces to the back surface, and the electrode group is pressed in the stacking direction (see Patent Documents 1 and 2, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-170636 [Patent Document 2] Patent No. 6413758 Summary of the Invention [Problem to be solved by the invention]

[0005] Stacked lithium-ion secondary batteries must not ignite or explode in the heating test of IEC (International Electrotechnical Commission) 62133-2 (a test in which the temperature is raised to 130°C at a rate of 5°C / min and maintained at 130°C for 30 minutes.) However, with conventional products, there is a risk that they will not pass the above test because the separator shrinks when used at high temperatures, causing a short circuit between the positive and negative electrodes. An object of the present invention is to provide a stacked lithium ion secondary battery in which separator shrinkage is prevented and short circuits between positive and negative electrodes are prevented even when used at high temperatures. [Means for solving the problem]

[0006] A first aspect of the present invention is a method for measuring the shear adhesive strength of a tape comprising a synthetic resin substrate and an adhesive layer fixed to the substrate, the method comprising the steps of: using a test piece made of the tape having a width of 10 mm and a length of 50 mm or more; attaching one longitudinal end of the test piece over a length of 10 mm to one side of a metal plate fixed on a table; attaching the other longitudinal end of the test piece to the chuck of a tensile testing machine; setting the length of the test piece from the attachment position to the bottom end of the chuck to 30 mm; conducting a tensile test under conditions of a tensile direction of 180 degrees and a tensile speed of 50 mm / min; and measuring the highest tensile strength exhibited during the test as the shear adhesive strength [N / 10 mm].

[0007] In order to solve the above problems, the present invention also provides a stacked lithium ion secondary battery having the following configuration (1) and configuration (2) or (3).

[0008] (1) An electrode assembly in which multiple positive and negative electrode plates are alternately stacked with separators interposed therebetween, an exterior housing that hermetically houses the electrode assembly, positive and negative terminals that are continuous with the positive and negative electrode plates, respectively, and extend outside the exterior housing, and tape that is affixed from the surface (the uppermost surface when the stacking direction is vertical) of the electrode assembly across the side surfaces and to the back surface (the lowermost surface when the stacking direction is vertical). The tape consists of a synthetic resin substrate and an adhesive layer fixed to the substrate.

[0009] (2) The tape has a ratio (c / a) of 1.8 or more between the measured shear adhesive strength (a) at 0° C. and the measured shear adhesive strength (c) at 130° C. The method for measuring the shear adhesive strength is the method for measuring the shear adhesive strength of the tape of the first embodiment.

[0010] (3) The tape has a shear adhesive strength of 60 N / 10 mm or more measured at 130° C. The method for measuring the shear adhesive strength is the same as the method for measuring the shear adhesive strength of the tape of the first embodiment. [Effects of the Invention]

[0011] According to the present invention, it is expected to provide a stacked lithium ion secondary battery in which the shrinkage of the separator is prevented even when used at high temperatures, and short circuits between the positive and negative electrodes can be prevented. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a stacked lithium ion secondary battery according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 3] 1 is a perspective view showing an electrode group of a stacked lithium ion secondary battery according to an embodiment of the present invention; [Figure 4] 1 is a diagram illustrating a method for measuring the shear adhesive strength of a tape according to an embodiment. [Figure 5] 1 is a graph showing the relationship between the shear adhesive strength of the tape measured by performing a tensile test on each sample of the Examples and the test temperature. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. In the following embodiments, technically preferable limitations are imposed for carrying out the present invention, but these limitations are not essential requirements for the present invention. (1) [Overall structure] First, the overall configuration of the stacked lithium ion secondary battery of this embodiment will be described. 1 and 2, the stacked lithium-ion secondary battery 1 of this embodiment includes an exterior body 2, an electrode group 3 housed inside the exterior body 2, and a positive electrode terminal 4 and a negative electrode terminal 5 extending outside the exterior body 2. The exterior body 2 is composed of two laminate films 21 and 22 that have the same rectangular planar shape. One laminate film 21 is a rectangular flat plate, and the other laminate film 22 has a shape in which a central portion forms an accommodation recess 221 and its peripheral portion forms a flange 222.

[0014] 2, the laminate films 21 and 22 are formed by laminating, in this order from the inside to the outside, heat-sealable resin layers 21a and 22a, metal layers 21b and 22b, and protective layers 21c and 22c. The laminate films 21 and 22 are arranged so that the heat-sealable resin layers 21a and 22a face each other, and the electrode group 3 is housed in the space formed by the laminate film 21 and the housing recess 221 of the laminate film 22 (between the heat-sealable resin layer 21a and the heat-sealable resin layer 22a). The exterior body 2 has a sealing portion 20 formed by heat-sealing the peripheral edges of the heat-sealable resin layers 21a and 22a of the two laminate films 21 and 22 together (the flange portion 222 of the laminate film 21).

[0015] 2, the electrode group 3 is formed by alternately stacking a plurality of positive electrode plates 31 and negative electrode plates 32 with separators 33 interposed therebetween. The positive electrode plate 31 is formed by forming a positive electrode active material layer 312 on one or both surfaces of a positive electrode current collector plate 311. The negative electrode plate 32 is formed by forming a negative electrode active material layer 322 on one or both surfaces of a negative electrode current collector plate 321.

[0016] 2 and 3 , a positive electrode lead 313 and a negative electrode lead 323 are continuous from the positive electrode current collector plate 311 and the negative electrode current collector plate 321 that constitute the positive electrode plate 31 and the negative electrode plate 32. One end of the positive electrode terminal 4 and one end of the negative electrode terminal 5 are joined and electrically connected to the bundled portion where all the positive electrode leads 313 and the negative electrode leads 323 are bundled by ultrasonic welding, resistance welding, or the like. The other ends of the positive electrode terminal 4 and the negative electrode terminal 5 extend outside the exterior body 2. In other words, the positive electrode terminal 4 and the negative electrode terminal 5 are continuous from the positive electrode plate 31 and the negative electrode plate 32, respectively, and extend outside the exterior body 2. The positive electrode terminal 4 and the negative electrode terminal 5 are fixed to the sealing portion 20 of the exterior body 2 in a state where they are sandwiched between the sealant portion 6 .

[0017] That is, the electrode group 3 is housed in the exterior body 2 in a sealed state. 3, tape 7 is attached to two locations on each of two of the four side surfaces of the electrode group 3 that do not have the positive electrode lead 313 and the negative electrode lead 323. The tape 7 is attached from the front surface of the electrode group 3 (the uppermost surface when the stacking direction is the vertical direction) across the side surfaces to the back surface (the lowermost surface when the stacking direction is the vertical direction).

[0018] The tape 7 comprises a synthetic resin substrate and an adhesive layer fixed to the substrate. The tape 7 has a shear adhesive strength ratio (c / a) of 1.8 or more between the measured value (a) at 0°C and the measured value (c) at 130°C, as determined by the following tape shear adhesive strength measurement method.

[0019] <Method for measuring the shear adhesive strength of tape> Using a test piece 10 mm wide and 50 mm long or more, attach one end of the test piece in the longitudinal direction for a length of 10 mm to one side of a metal plate fixed on a table, and attach the other end of the test piece in the longitudinal direction to the chuck of a tensile testing machine. The length of the test piece from the attachment point to the bottom end of the chuck is 30 mm, and a tensile test is carried out under conditions of a tensile direction of 180 degrees and a tensile speed of 50 mm / min, and the highest tensile strength displayed during the test is measured as the shear adhesive strength [N / 10 mm].

[0020] In this embodiment, as shown in Fig. 4, a test piece 70 is prepared by cutting tape 7 to a width of 10 mm and a length of 50 mm. One longitudinal end of the test piece 70, a length of 10 mm (attachment portion 71), is attached by a conventional attachment method to one surface of a metal plate 82, which is a Cu plate (Ni / Cu plate) with a Ni-plated surface, fixed on a stand 81. The other longitudinal end of the test piece 70 is attached to a chuck 83 of a tensile tester so that the length of an intermediate portion 72 (the portion from the attachment position of the test piece to the bottom end of the chuck) is 30 mm. In this state, a tensile test is performed under the above-mentioned conditions.

[0021] The surface roughness of the metal plate 82 is Ra: 0.25±0.15 μm, and before the test, it is cleaned using acetone in accordance with JIS Z 0237:2009 10.2.3. After the metal plate 82 and the test piece 70 are kept at 0°C or 130°C for one hour, they are brought into a test space kept at 25°C and the test is immediately carried out.

[0022] As described above, in the laminated lithium ion secondary battery 100 of the embodiment, by using as the tape 7 a tape in which the ratio (c / a) of the measured shear adhesive strength (a) at 0°C to the measured shear adhesive strength (c) at 130°C obtained by carrying out the above method is 1.8 or more, shrinkage of the separator can be prevented even when the battery is used at a high temperature (130°C), and short circuits between the positive and negative electrodes can be prevented.

[0023] Furthermore, in the laminated lithium ion secondary battery 100 of the embodiment, by using as the tape 7 a tape obtained by carrying out the above-mentioned method and having a measured shear adhesive strength at 130°C of 60 N / 10 mm or more, shrinkage of the separator can be prevented even when the battery is used at high temperatures (130°C), and short circuits between the positive and negative electrodes can be prevented. [Example]

[0024] The present invention will be further described below with reference to specific examples. As the laminated lithium ion secondary battery 1 of the embodiment, prototype batteries No. 1 to No. 3, all of which had the same structure except for the tape 7, were fabricated.

[0025] [About the composition of Tape 7 other than the material] [Preparation of positive electrode plate] A positive electrode slurry was prepared by dispersing 93.7 mass% of lithium cobalt oxide (LiCoO2) as the positive electrode active material, 2 mass% of polyvinylidene fluoride (PVDF) as the binder, 4 mass% of carbon black as the conductive agent, and 0.3 mass% of polyvinylpyrrolidone (PVP) as the dispersant in N-methyl-2-pyrrolidone (NMP) as the solvent.

[0026] Next, the positive electrode slurry was applied to both sides of an aluminum foil (thickness: 12 μm) serving as a positive electrode current collector plate 311 in an amount of 31.6 g / m 2 The mixture was coated with a coater so that the thickness became 1.58 g / cc, and then dried at 80 to 130° C. Thereafter, the mixture was pressed until the electrode density became 3.58 g / cc. In this way, a positive electrode plate 31 was produced in which positive electrode active material layers 312 were formed on both sides of a positive electrode current collector plate 311.

[0027] In addition, a positive electrode plate 31 in which a positive electrode active material layer 312 was formed on one side of the positive electrode current collector 311 was produced in the same manner, except that the positive electrode slurry was applied to one side of the aluminum foil (thickness 12 μm) that served as the positive electrode current collector 311. The positive electrode current collector plate 311 used had a rectangular planar shape and was provided with a positive electrode lead 313 protruding by a predetermined width from the center of one side of the rectangular planar shape.

[0028] [Preparation of negative electrode plate] Anode active materials (94.92 mass % graphite and 2.68 mass % silicon oxide) and binders (1 mass % styrene butadiene rubber (SBR) and 1.4 mass % carboxymethyl cellulose (CMC)) were dispersed in ion-exchanged water as a solvent to prepare anode slurry.

[0029] Next, the negative electrode slurry was applied to both sides of a copper foil (thickness 6 μm) serving as the negative electrode current collector plate 321 in an amount of 16.0 g / m2 The mixture was coated with a coater so that the thickness became 1.52 g / cc, and then dried at 80 to 110° C. Thereafter, the mixture was pressed until the electrode density became 1.52 g / cc. In this way, a negative electrode plate 32 was produced in which a negative electrode active material layer 322 was formed on both sides of a negative electrode current collector plate 321. The negative electrode current collector plate 321 used had a rectangular planar shape and was provided with a negative electrode lead 323 protruding by a predetermined width from the center of one side of the rectangular planar shape.

[0030] [Separator] The separator 33 used was a separator having a 9 μm thick microporous membrane made of polyethylene (PE) resin and a 3 μm thick coating layer made of AlO(OH) on one side thereof.

[0031] [Preparation of electrode groups] The positive electrode plate 31, the negative electrode plate 32, and the separator 33 were cut into a rectangle of a predetermined area. Next, as shown in Fig. 2, n positive electrode plates and (n+1) negative electrode plates were alternately stacked with separators 33 interposed therebetween to obtain an electrode group 3. Here, n=9. The thickness of the electrode group 3 was 7 mm.

[0032] 2 and 3, the positive electrode leads 313 and the negative electrode leads 323 were bundled at their tip ends and joined together by ultrasonic welding. An aluminum tab was joined to the joint of the positive electrode lead 313 by ultrasonic welding as the positive electrode terminal 4. A copper tab was joined to the joint of the negative electrode lead 323 by ultrasonic welding as the negative electrode terminal 5. Next, as shown in Fig. 3, tape 7 was attached to two locations on each of the two side surfaces, from the surface of the electrode group 3 (the uppermost surface when the stacking direction is vertical) across the side surfaces to the back surface (the lowermost surface when the stacking direction is vertical). Tape 7 was 10 mm wide and 27 mm long.

[0033] [Exterior body] The laminate films 21 and 22 of the exterior package 2 were prepared with the following layers: The heat-sealable resin layers 21a and 22a were polyolefin resin films with a thickness of 80 μm. The metal layers 21b and 22b were aluminum foils with a thickness of 40 μm. The protective layers 21c and 22c were polyamide films with a thickness of 25 μm.

[0034] [Nonaqueous electrolyte] The non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF6) as an electrolyte at a concentration of 1.3 mol / L in a solvent made by mixing ethylene carbonate (EC), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP) in a volume ratio of 30:10:45:15 (=EC:DEC:EP:PP).

[0035] In addition, as additives, 2.25 mass% of vinylene carbonate (VC), 1.0 mass% of allylsuccinic anhydride (ASAh), 1.0 mass% of 1,3-dioxane (DO), 1.25 mass% of adiponitrile (ADN), 1.25 mass% of suberonitrile (SBN), and 0.15 mass% of lithium tetrafluoroborate (LiBF) were added relative to the total mass of the electrolyte (EC+DEC+EP+PP+LiPF).

[0036] [Prototype battery assembly] The electrode group 3 to which the positive electrode terminal 4 and the negative electrode terminal 5 are welded is placed in the accommodation recess 221 of the other laminate film 22, and one laminate film 21 is placed over it, and the peripheral edge of one laminate film 21 is overlapped with the flange 222 of the other laminate film 22. As a result, the tip of the sealant portion 6 protrudes from the laminate films 21 and 22, and the positive electrode terminal 4 and the negative electrode terminal 5 extend from the tip of the sealant portion 6.

[0037] Next, the overlapping flange 222 of the laminate films 21, 22 was heat-sealed to seal the three sides, including the two sides from which the positive electrode terminal 4 and the negative electrode terminal 5 extended. Next, 2.4 g / Ah of nonaqueous electrolyte was injected through the portion corresponding to the unsealed side. The portion of the flange 222 corresponding to this side was then heat-sealed under a reduced pressure of 1 hPa to 100 hPa to obtain a prototype battery after the injection of the nonaqueous electrolyte. The theoretical capacity of this prototype battery was 3.85 Ah.

[0038] After the non-aqueous electrolyte was poured into the prototype battery, the battery was left standing for 12 hours to allow the non-aqueous electrolyte to permeate the constituent members of the electrode group. Next, the positive and negative terminals of the prototype battery were connected to a power source, and the prototype battery was initially charged to 10% of its rated capacity at a current of 0.25 ItA. After that, the prototype battery was placed in a decompression chamber with part of the sealing part of the exterior body open, to vent the gas generated inside the prototype battery.

[0039] The exterior was then sealed again, and the battery was charged a second time at a current of 0.5 ItA to 10-100% of its rated capacity. After leaving the battery in a high-temperature environment for 3 hours, it was charged at a constant current of 0.5 ItA to 4.45 V, and then charged at a constant voltage of 0.02 ItA. Thereafter, the rated capacity was measured at a current value of 0.2 ItA, and the battery was charged to a state of charge (SOC) of 10% of the rated capacity to obtain a prototype battery.

[0040] [About Tape 7] The following tape 7 was prepared as the tape 7 for constituting each of the prototype batteries No. 1 to No. 3. <No.1> Teraoka Manufacturing Co., Ltd.'s "Kapton (registered trademark) Film Adhesive Tape No. 653S" Overall thickness 0.055mm Base material: 30 μm thick polyimide resin, adhesive layer: 25 μm thick acrylic resin <No.2> Teraoka Manufacturing Co., Ltd.'s "Kapton (registered trademark) Film Adhesive Tape No. 650S" Overall thickness 0.055mm Base material: 30 μm thick polyimide resin, adhesive layer: 25 μm thick silicone resin <No.3> Nitto Denko Corporation "Polypropylene Adhesive Tape No. 370F" Overall thickness 0.065mm Base material: 40 μm thick polypropylene resin, adhesive layer: 25 μm thick acrylic resin The shear adhesive strength of each of tapes No. 1 to No. 3 was measured at 0°C, 25°C, and 130°C using the shear adhesive strength test described above. The tensile tester used was a Nidec-Shimpo FGS-100VC. The results are shown in the graph in Figure 5.

[0041] For tapes 7 No. 2 and No. 3, the shear adhesive strength was measured by peeling the adhesive layer from metal plate 82 at all temperatures: 0°C, 25°C, and 130°C. For tape 7 No. 1, the shear adhesive strength was measured by peeling the adhesive layer from metal plate 82 in the tests at 0°C and 25°C, but at 130°C, the shear adhesive strength was measured by breaking the substrate.

[0042] In addition, the ratio (c / a) of the maximum value of the shear adhesive strength at 0°C (a) to the maximum value at 130°C (c) was calculated.

[0043] [About the heating test] The obtained prototype batteries No. 1 to No. 3 were subjected to a heating test in accordance with IEC (International Electrotechnical Commission) 62133-2 (a test in which the temperature was raised to 130°C at a rate of 5°C / min and then held at 130°C for 30 minutes).Prototype battery No. 1, which used No. 1 tape 7, did not ignite or explode, but prototype batteries No. 2 and No. 3, which used No. 2 and No. 3 tape 7, did ignite and explode. These results are summarized in Table 1.

[0044] [Table 1]

[0045] As can be seen from the results in Table 1, the ratio (c / a) of the shear adhesive strength measured at 0°C (a) to the shear adhesive strength measured at 130°C (c), obtained using the above-mentioned tape shear adhesive strength measurement method for tape 7, was 1.87. The No. 1 prototype battery, which used tape with a shear adhesive strength measured at 130°C of 60.9 N / 10 mm, was able to prevent separator shrinkage and short circuits between the positive and negative electrodes even when used at high temperatures (130°C).

[0046] In contrast, prototype batteries No. 2 and No. 3, which used tapes with a ratio (c / a) of less than 1.8 (1.15, 1.07) and a measured shear adhesive strength at 130°C of less than 60 (40.1, 27.8) N / 10 mm, experienced separator shrinkage when used at high temperatures (130°C), resulting in failure to prevent short circuits between the positive and negative electrodes. [Explanation of symbols]

[0047] 1. Stacked lithium-ion secondary battery 2. Exterior body 3 electrode groups 31 Positive electrode plate 32 negative electrode plate 311 Positive current collector plate 321 Negative current collector plate 312 Cathode active material layer 322 Negative electrode active material layer 33 Separator 313 Positive lead 323 Negative lead 4 Positive terminal 5 Negative terminal 6 Sealant section 7. Tape 70 tape specimens 71 Adhesive part 72 Middle section 81 units 82 Metal plate

Claims

1. an electrode group in which a plurality of positive electrode plates and negative electrode plates are alternately stacked with separators interposed therebetween; an exterior body that houses the electrode group in a sealed state; a positive electrode terminal and a negative electrode terminal that are continuous with the positive electrode plate and the negative electrode plate, respectively, and extend outside the exterior body; a tape attached from the front surface of the electrode group across the side surface to the rear surface; Including, The tape comprises a synthetic resin substrate and an adhesive layer fixed to the substrate, The tape has a ratio (c / a) of the shear adhesive strength measured at 0°C (a) to the shear adhesive strength measured at 130°C (c) of 1.8 or more, The method for measuring the shear adhesive strength is to use a test piece made of the tape having a width of 10 mm and a length of 50 mm or more, attach one end of the test piece in the longitudinal direction by a length of 10 mm to one side of a metal plate fixed on a stand, and attach the other end of the test piece in the longitudinal direction to the chuck of a tensile testing machine, set the length of the test piece from the attachment position to the bottom end of the chuck to 30 mm, and perform a tensile test under conditions of a tensile direction of 180 degrees and a tensile speed of 50 mm / min, and measure the highest tensile strength displayed during the test as the shear adhesive strength [N / 10 mm] for this laminated lithium ion secondary battery.

2. an electrode group in which a plurality of positive electrode plates and negative electrode plates are alternately stacked with separators interposed therebetween; an exterior body that houses the electrode group in a sealed state; a positive electrode terminal and a negative electrode terminal that are continuous with the positive electrode plate and the negative electrode plate, respectively, and extend outside the exterior body; a tape attached from the front surface of the electrode group across the side surface to the rear surface; Including, The tape comprises a synthetic resin substrate and an adhesive layer fixed to the substrate, The tape has a shear adhesive strength measured at 130°C of 60 N / 10 mm or more, The method for measuring the shear adhesive strength is to use a test piece made of the tape having a width of 10 mm and a length of 50 mm or more, attach one end of the test piece in the longitudinal direction by a length of 10 mm to one side of a metal plate fixed on a stand, and attach the other end of the test piece in the longitudinal direction to the chuck of a tensile testing machine, set the length of the test piece from the attachment position to the bottom end of the chuck to 30 mm, and perform a tensile test under conditions of a tensile direction of 180 degrees and a tensile speed of 50 mm / min, and measure the highest tensile strength displayed during the test as the shear adhesive strength [N / 10 mm] for this laminated lithium ion secondary battery.

3. A method for measuring the shear adhesive strength of a tape comprising a synthetic resin substrate and an adhesive layer fixed to the substrate, comprising: A method for measuring the shear adhesive strength of a tape, comprising: using a test piece made of the tape having a width of 10 mm and a length of 50 mm or more; attaching one longitudinal end of the test piece by a length of 10 mm to one side of a metal plate fixed on a table; attaching the other longitudinal end of the test piece to the chuck of a tensile testing machine; setting the length of the test piece from the attachment position to the bottom end of the chuck to 30 mm; conducting a tensile test under conditions of a tensile direction of 180 degrees and a tensile speed of 50 mm / min; and measuring the highest tensile strength displayed during the test as the shear adhesive strength [N / 10 mm].

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