JP2020045432A - Adhesive sheet for battery and lithium ion battery - Google Patents

Abstract

To provide an adhesive sheet for a battery which can exhibit excellent adhesive force and has high insulation properties and to provide a lithium ion battery using such an adhesive sheet for a battery.SOLUTION: There is provided an adhesive sheet 1 for a battery which comprises a substrate 11, a first adhesive layer 12 containing inorganic fine particles 121 which is arranged on one surface side of the substrate 11 and a second adhesive layer 13 containing no inorganic fine particles 121 which is arranged on a surface side opposite to the substrate 11 in the first adhesive layer 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery pressure-sensitive adhesive sheet and a lithium-ion battery manufactured using the battery pressure-sensitive adhesive sheet.

  In some batteries, a band-like laminate in which a positive electrode, a negative electrode, and a separator located therebetween are laminated is housed inside in a wound state. Electrode extraction tabs made of a conductor are connected to the positive electrode and the negative electrode, respectively, and the positive electrode and the negative electrode are electrically connected to the positive electrode terminal and the negative electrode terminal of the battery via these electrode extraction tabs, respectively. .

  An adhesive sheet may be used for fastening the above-mentioned laminate and fixing the electrode take-out tab to the electrode. As such an adhesive sheet, a sheet composed of a substrate and an adhesive layer provided on one surface of the substrate is generally used. In addition, from the viewpoint of improving desired performance such as insulating properties, the surface of the base material opposite to the pressure-sensitive adhesive layer, or between the base material and the pressure-sensitive adhesive layer, contains an insulating material or the like. An adhesive sheet provided with an insulating layer may be used.

  However, providing the insulating layer as described above separately from the pressure-sensitive adhesive layer causes an increase in manufacturing cost. Therefore, attempts have been made to improve the insulating properties of the pressure-sensitive adhesive sheet without providing the above-mentioned insulating layer by including an insulating material or the like in the pressure-sensitive adhesive layer. For example, Patent Document 1 discloses a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer contains alumina. Patent Document 2 discloses an adhesive sheet in which an adhesive layer contains magnesium hydroxide, alumina, magnesium oxide, aluminum hydroxide, silica, boron nitride, titanium oxide, or magnesium carbonate.

International Publication No. WO 2017/038010 JP-A-2017-152372

  By the way, inside the battery, the pressure-sensitive adhesive sheet used for fastening the laminated body or fixing the electrode extraction tab to the electrode can exhibit good adhesive strength from the viewpoint of the battery exhibiting desired performance. Is important. In particular, such an adhesive sheet may come into contact with an electrolytic solution filled inside the battery, and it is required to maintain a sufficient adhesive force even in such a case. However, a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer containing an insulating material or the like as disclosed in Patent Documents 1 and 2 cannot exhibit sufficient adhesive strength.

  In recent years, a pressure-sensitive adhesive sheet used in a battery has been required to have higher insulating properties from the viewpoint of enhancing the safety of the battery. In particular, even when an internal short circuit occurs due to the entry of foreign matter into the battery or the like, high insulation properties capable of suppressing heat generation due to the internal short circuit are required.

  The present invention has been made in view of the above circumstances, and provides a pressure-sensitive adhesive sheet for a battery that can exhibit excellent adhesive strength and has high insulating properties, and a lithium-ion battery using the pressure-sensitive adhesive sheet for a battery. The purpose is to do.

  In order to achieve the above object, first, the present invention relates to a base material, a first pressure-sensitive adhesive layer provided on one surface side of the base material, the first pressure-sensitive adhesive layer containing inorganic fine particles, and the first pressure-sensitive adhesive. A pressure-sensitive adhesive sheet for a battery, comprising: a second pressure-sensitive adhesive layer not containing the inorganic fine particles, provided on a surface of the layer opposite to the base material (Invention 1).

  The battery pressure-sensitive adhesive sheet according to the invention (Invention 1) includes a first pressure-sensitive adhesive layer containing inorganic fine particles and a second pressure-sensitive adhesive layer containing no inorganic fine particles. The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are disposed so that the pressure-sensitive adhesive layers of the first and second pressure-sensitive adhesive layers are in contact with each other, thereby achieving both good adhesion to an adherend and high insulation. Can be.

  In the above invention (Invention 1), the content of the inorganic fine particles in the first pressure-sensitive adhesive layer is 50 parts by mass or more and 1000 parts by weight or more with respect to 100 parts by weight of the pressure-sensitive adhesive component contained in the first pressure-sensitive adhesive layer. It is preferable that the amount is not more than mass part (Invention 2).

  In the above inventions (Inventions 1 and 2), the thickness of the first pressure-sensitive adhesive layer is preferably 1 μm or more and 50 μm or less (Invention 3).

  In the above inventions (Inventions 1 to 3), the thickness of the second pressure-sensitive adhesive layer is preferably 1 μm or more and 50 μm or less (Invention 4).

  In the above inventions (Inventions 1 to 4), the adhesive strength of the adhesive sheet for a battery to an aluminum plate is preferably 0.5 N / 25 mm or more and 50 N / 25 mm or less (Invention 5).

  Secondly, the present invention is characterized in that two or more conductors are fixed in contact with each other using the pressure-sensitive adhesive sheet for a battery (Inventions 1 to 5) inside the battery. An ion battery is provided (Invention 6).

  ADVANTAGE OF THE INVENTION The adhesive sheet for batteries which concerns on this invention can exhibit the outstanding adhesive force, and has high insulation. Therefore, the lithium ion battery manufactured using the pressure-sensitive adhesive sheet for a battery can exhibit excellent performance.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the adhesive sheet for batteries which concerns on one Embodiment of this invention. 1 is an exploded perspective view, partly in section, of a lithium ion battery according to one embodiment of the present invention. 1 is an exploded perspective view of an electrode body of a lithium ion battery according to one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive sheet for battery]
As shown in FIG. 1, a pressure-sensitive adhesive sheet 1 for a battery according to one embodiment of the present invention includes a base material 11, a first pressure-sensitive adhesive layer 12 provided on one surface side of the base material 11, The second pressure-sensitive adhesive layer 13 provided on the surface of the pressure-sensitive adhesive layer 12 opposite to the substrate 11, and the peeling provided on the surface of the second pressure-sensitive adhesive layer 13 opposite to the substrate 11 And a seat 14. In the battery pressure-sensitive adhesive sheet 1 according to the present embodiment, the first pressure-sensitive adhesive layer 12 includes the inorganic fine particles 121. On the other hand, the second pressure-sensitive adhesive layer 13 does not include the inorganic fine particles 121.

  Here, the "pressure-sensitive adhesive sheet for a battery" in the present specification is a pressure-sensitive adhesive sheet used at a location where it may come into contact with an electrolytic solution in the production of a battery, and is preferably a pressure-sensitive adhesive sheet used inside a battery. It may be an adhesive sheet for battery interior. The battery is preferably a non-aqueous battery. Therefore, the electrolyte used for the battery is preferably a non-aqueous electrolyte. The pressure-sensitive adhesive sheet for a battery in the present specification is preferably a pressure-sensitive adhesive sheet that is stuck to a portion that may be immersed in an electrolytic solution or a portion that may come into contact with an electrolytic solution inside a nonaqueous battery. As the non-aqueous battery, a lithium ion battery is particularly preferred.

  In the pressure-sensitive adhesive sheet for a battery 1 according to the present embodiment, the first pressure-sensitive adhesive layer 12 includes the inorganic fine particles 121, so that the first pressure-sensitive adhesive layer 12 functions as an insulating layer. For this reason, the pressure-sensitive adhesive sheet 1 for a battery according to the present embodiment has excellent insulation in a normal state. In addition, since the battery pressure-sensitive adhesive sheet 1 according to the present embodiment includes the first pressure-sensitive adhesive layer 12, even when an internal short circuit occurs in a battery in which the battery pressure-sensitive adhesive sheet 1 is used, heat is generated. The amount can be kept low. Furthermore, since the battery pressure-sensitive adhesive sheet 1 according to the present embodiment includes the first pressure-sensitive adhesive layer 12, it can increase the total thickness of the pressure-sensitive adhesive layer together with the second pressure-sensitive adhesive layer 13, Excellent adhesive strength can be obtained.

  In the pressure-sensitive adhesive sheet 1 for a battery according to the present embodiment, the position where the second pressure-sensitive adhesive layer 13 containing no inorganic fine particles 121 is in contact with the adherend when the pressure-sensitive adhesive sheet 1 for a battery is adhered to the adherend. , Excellent adhesive strength can be exhibited. In particular, since the second pressure-sensitive adhesive layer 13 does not include the inorganic fine particles 121, the adhesive strength due to the presence of the inorganic fine particles 121 does not decrease, and thus the battery pressure-sensitive adhesive sheet 1 has excellent adhesive strength. Will be demonstrated. Therefore, according to the pressure-sensitive adhesive sheet for a battery 1 according to the present embodiment, it is possible to suppress the occurrence of a problem of the battery due to the peeling of the pressure-sensitive adhesive sheet inside the battery.

  As described above, in the battery pressure-sensitive adhesive sheet 1 according to the present embodiment, by providing the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13, the excellent pressure-sensitive adhesive strength, which has conventionally been difficult to achieve both, is provided. And high insulation properties can be satisfactorily compatible. Therefore, a highly safe battery can be manufactured by using the battery adhesive sheet 1 according to the present embodiment.

1. Each component 1-1. Substrate In the battery pressure-sensitive adhesive sheet 1 according to the present embodiment, the substrate 11 preferably has a high minimum voltage that causes dielectric breakdown. For example, the voltage is preferably 1 kV or more, and particularly preferably 2 kV or more. Preferably, it is more preferably 5 kV or more. When the voltage is 1 kV or more, dielectric breakdown of the base material 11 hardly occurs, and the reliability of the battery pressure-sensitive adhesive sheet 1 becomes higher.

  In addition, the base material 11 preferably has flame retardancy that satisfies the UL94 standard flame retardant level V-0. Since the base material 11 has such flame retardancy, even when heat is generated by use of a normal battery, denaturation and deformation of the base material 11 are suppressed. In addition, even if a problem occurs in the battery and excessive heat is generated, ignition and combustion of the base material 11 are suppressed, and a serious accident is prevented.

  The material of the base material 11 can be appropriately selected from the viewpoints of insulation properties, flame retardancy, heat resistance, reactivity with the electrolyte, permeability of the electrolyte, and the like. In particular, it is preferable to use a resin film as the substrate 11. Examples of the resin film include a polyester film such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; a polyolefin film such as a polyethylene film and a polypropylene film; a polyamide film, a polyimide film, and a polyamideimide film. Combined film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film , Polymethylpentene film, polysulfone film, polyether ether Ketone film, polyethersulfone film, polyetherimide film, fluororesin film, acrylic resin film, polyurethane resin film, norbornene-based polymer film, cyclic olefin-based polymer film, cyclic conjugated diene-based polymer film, vinyl alicyclic A resin film such as a hydrocarbon polymer film or a laminated film thereof is exemplified. In particular, from the viewpoint of insulating properties and flame retardancy, a polymer film containing nitrogen in the main chain (which may contain components other than the polymer; the same applies in the present specification) is preferable, and the main chain is particularly preferable. A polymer film having a nitrogen-containing ring structure is preferable, and a polymer film having a nitrogen-containing ring structure and an aromatic ring structure in the main chain is more preferable. Specifically, for example, a polyimide film, a polyetherimide film, or a polyetheretherketone film is preferable, and among these, a polyimide film particularly excellent in insulating properties and flame retardancy is preferable.

  The lower limit of the thickness of the base material 11 is preferably 5 μm or more, particularly preferably 10 μm or more, and further preferably 15 μm or more. When the lower limit of the thickness of the base material 11 is as described above, for example, the electrode body in which the electrode extraction tab is fixed by the battery adhesive sheet 1 is wound up, and a winding pressure is applied to the battery adhesive sheet 1. Even in this case, the breakage of the substrate 11 can be effectively suppressed. The upper limit of the thickness of the substrate 11 is preferably 200 μm or less, particularly preferably 100 μm or less, and further preferably 40 μm or less. When the upper limit value of the thickness of the base material 11 is as described above, the pressure-sensitive adhesive sheet 1 for a battery has appropriate flexibility, and is formed on a surface where a step is present as in the case where the electrode and the electrode take-out tab are fixed. Even when the battery adhesive sheet 1 is stuck, it is possible to favorably follow the step.

1-2. First Pressure-Sensitive Adhesive Layer (1) Inorganic Fine Particles The first pressure-sensitive adhesive layer 12 includes a pressure-sensitive adhesive component and inorganic fine particles 121. The inorganic fine particles 121 are not limited as long as a desired insulating property can be imparted to the first pressure-sensitive adhesive layer 12, and examples thereof include alumina, titania, calcium carbonate, silica, boehmite, talc, iron oxide, and silicon carbide. , Boron nitride, barium sulfate, zirconium oxide, and other powders, spherical beads of these, single crystal fibers, glass fibers, and the like can be used. These may be used alone or as a mixture of two or more. Among these, it is preferable to use at least one of alumina, titania, and calcium carbonate from the viewpoint of easily achieving high insulating properties.

  The average particle size of the inorganic fine particles 121 is preferably 0.01 μm or more, particularly preferably 0.1 μm or more, and further preferably 0.2 μm or more. When the average particle diameter of the inorganic fine particles 121 is 0.01 μm or more, the pressure-sensitive adhesive sheet 1 for a battery according to the present embodiment easily exhibits high insulating properties. Further, the average particle diameter of the inorganic fine particles 121 is preferably 10 μm or less, particularly preferably 5 μm or less, and further preferably 1.4 μm or less. When the average particle diameter of the inorganic fine particles 121 is 10 μm or less, the dispersibility of the inorganic fine particles 121 becomes more excellent, and when the first pressure-sensitive adhesive layer 12 is formed on the base material 11, the first adhesive Generation of unevenness on the surface of the agent layer 12 opposite to the substrate 11 can be effectively prevented. Further, by forming the second pressure-sensitive adhesive layer 13 on the surface, it is possible to obtain very high smoothness on the surface of the second pressure-sensitive adhesive layer 13 opposite to the first pressure-sensitive adhesive layer 12. it can. Thereby, the second pressure-sensitive adhesive layer 13 exhibits excellent adhesion to the adherend. Note that the average particle size of the inorganic fine particles 121 is measured by a laser diffraction / scattering method.

  The content of the inorganic fine particles 121 in the first pressure-sensitive adhesive layer 12 is preferably 50 parts by weight or more, and more preferably 100 parts by weight or more, based on 100 parts by weight of the pressure-sensitive adhesive component contained in the first pressure-sensitive adhesive layer 12. Is more preferable, particularly preferably 150 parts by mass or more, and further preferably 200 parts by mass or more. When the content is 50 parts by mass or more, the pressure-sensitive adhesive sheet 1 for a battery according to the present embodiment easily exhibits high insulating properties. Further, the content of the inorganic fine particles 121 in the first pressure-sensitive adhesive layer 12 is preferably 1,000 parts by mass or less based on 100 parts by mass of the pressure-sensitive adhesive component contained in the first pressure-sensitive adhesive layer 12, and particularly preferably 600 parts by mass. It is preferably at most 400 parts by mass, more preferably at most 400 parts by mass. When the content is 1000 parts by mass or less, excellent adhesion between the base material 11 and the first pressure-sensitive adhesive layer 12 and between the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 It is easy to achieve the property, and delamination can be effectively suppressed.

(2) Adhesive component The adhesive component contained in the first adhesive layer 12 is not particularly limited, and can be appropriately selected from the viewpoints of elution to an electrolytic solution, flame retardancy, heat resistance, insulation, and the like. In particular, as the adhesive component, it is preferable to use at least one of an acrylic adhesive component, a silicone adhesive component, a rubber adhesive component, and a urethane adhesive component. The pressure-sensitive adhesive component contained in the first pressure-sensitive adhesive layer 12 may be any of an emulsion type, a solvent type, and a non-solvent type, and may be a cross-linking type or a non-cross-linking type. Among the above, an acrylic adhesive component is preferable from the viewpoints of adhesion to the base material 11 and the second adhesive layer 13 and easiness of fine adjustment of adhesive force, and a cross-linkable acrylic adhesive component is particularly preferable. Preferably, a solvent-type crosslinkable acrylic pressure-sensitive adhesive component is used.

  The acrylic adhesive component described above is preferably composed of a (meth) acrylate polymer (A) and a crosslinking agent (B). In this case, the first pressure-sensitive adhesive layer 12 includes an acrylic pressure-sensitive adhesive component composed of the (meth) acrylate polymer (A) and the crosslinking agent (B), and the inorganic fine particles 121. Such a first pressure-sensitive adhesive layer 12 is formed of a first pressure-sensitive adhesive layer-containing pressure-sensitive adhesive composition containing a (meth) acrylate polymer (A), a cross-linking agent (B), and inorganic fine particles 121 (hereinafter referred to as “a pressure-sensitive adhesive composition”). Adhesive composition P1 ").).

  In addition, in this specification, a (meth) acrylic ester means both an acrylic ester and a methacrylic ester. The same applies to other similar terms. The term “polymer” also includes the concept of “copolymer”.

(2-1) (meth) acrylate polymer (A)
The (meth) acrylic acid ester polymer (A) is used from the viewpoint that the first pressure-sensitive adhesive layer 12 tends to have high adhesion to both the base material 11 and the second pressure-sensitive adhesive layer 13. It is preferable that the monomer unit constituting the polymer contains an alkyl (meth) acrylate having an alkyl group having 1 to 10 carbon atoms. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic acid. Examples include n-pentyl, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and n-decyl (meth) acrylate. Among these, alkyl acrylates having 3 to 9 carbon atoms in the alkyl group are preferable, and alkyl acrylates having 5 to 8 carbon atoms in the alkyl group are particularly preferable. These may be used alone or in combination of two or more.

  (Meth) acrylic acid ester polymer (A) preferably contains at least 50% by mass of a (meth) acrylic acid alkyl ester having 1 to 10 carbon atoms in the alkyl group as a monomer unit constituting the polymer. In particular, the content is preferably 60% by mass or more, more preferably 70% by mass or more. By containing the above (meth) acrylic acid alkyl ester in an amount of 50% by mass or more, the adhesion between the base material 11 and the first pressure-sensitive adhesive layer 12 and the adhesion between the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 are reduced. Is further improved. The (meth) acrylic acid ester polymer (A) contains 99% by mass or less of a (meth) acrylic acid alkyl ester having 1 to 10 carbon atoms in the alkyl group as a monomer unit constituting the polymer. Is preferably contained, particularly preferably 95% by mass or less, more preferably 90% by mass or less. When the amount of the alkyl (meth) acrylate is 99% by mass or less, a suitable amount of another monomer component can be introduced into the (meth) acrylate polymer (A).

  Further, the (meth) acrylic acid ester polymer (A) has an alkyl group as a monomer unit constituting the polymer from the viewpoint that the first pressure-sensitive adhesive layer 12 easily has excellent electrolytic solution resistance. It is preferable that the group contains an alkyl (meth) acrylate having 11 to 20 carbon atoms. Examples of such an alkyl (meth) acrylate include n-lauryl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, alkyl (meth) acrylate having 12 to 18 carbon atoms in the alkyl group is preferable. These may be used alone or in combination of two or more.

  (Meth) acrylic acid ester polymer (A) preferably contains 1% by mass or more of (meth) acrylic acid alkyl ester having 11 to 20 carbon atoms as a monomer unit constituting the polymer. More preferably, the content is 5% by mass or more, particularly preferably 10% by mass or more. When the content is 1% by mass or more, the obtained first pressure-sensitive adhesive layer 12 has higher hydrophobicity, thereby easily achieving excellent electrolytic solution resistance. On the other hand, the (meth) acrylate polymer (A) contains, as a monomer unit constituting the polymer, 40 mass% or less of a (meth) acrylate alkyl ester having 11 to 20 carbon atoms in the alkyl group. , Preferably 30% by mass or less, more preferably 20% by mass or less. When the content of the alkyl (meth) acrylate is 40% by mass or less, it becomes easy to introduce a suitable amount of another monomer component into the (meth) acrylate polymer (A).

  If desired, the (meth) acrylate polymer (A) may contain a monomer other than the above as a monomer unit constituting the polymer. The monomer may be a monomer containing a reactive functional group, or may be a monomer containing no reactive functional group.

  Examples of the monomer having a reactive functional group (reactive functional group-containing monomer) include a monomer having a carboxy group in the molecule (carboxy group-containing monomer), a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), And a monomer having an amino group (amino group-containing monomer). Among them, the (meth) acrylate polymer (A) preferably contains a hydroxyl group-containing monomer or a carboxy group-containing monomer as a monomer unit constituting the polymer, and particularly preferably contains a carboxy group-containing monomer. preferable. By containing the carboxy group-containing monomer, the polarity of the formed first pressure-sensitive adhesive layer 12 is increased, and the elution resistance to the electrolytic solution is further improved.

  Examples of the carboxy group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid. Among these, acrylic acid is preferred. According to acrylic acid, the above effects are more excellent. The carboxy group-containing monomers may be used alone or in combination of two or more.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and (meth) acrylate. ) Hydroxyalkyl (meth) acrylates such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. These may be used alone or in combination of two or more.

  Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  The (meth) acrylate polymer (A) preferably contains a reactive functional group-containing monomer in an amount of 0.5% by mass or more, and particularly preferably 1% by mass or more, as a monomer unit constituting the polymer. And more preferably 3% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer as a monomer unit constituting the polymer in an amount of 30% by mass or less, particularly preferably 20% by mass or less. And more preferably 9% by mass or less. When the (meth) acrylic acid ester polymer (A) contains the reactive functional group-containing monomer in the above amount as a monomer unit, a crosslinked structure is favorably formed by the reaction with the crosslinking agent (B) and is formed. The cohesive force of the first pressure-sensitive adhesive layer 12 is appropriately increased, and thereby, the elution resistance to the electrolytic solution is further improved.

  On the other hand, examples of the monomer having no reactive functional group include, for example, methoxyethyl (meth) acrylate, alkoxyalkyl (meth) acrylate such as ethoxyethyl (meth) acrylate, N- (meth) acrylate, Non-crosslinkable tertiary amino group-containing (meth) acrylates such as N-dimethylaminoethyl, N, N-dimethylaminopropyl (meth) acrylate, (meth) acryloylmorpholine, (meth) acrylamide, dimethylacrylamide , Vinyl acetate, styrene and the like. These may be used alone or in combination of two or more.

  The (meth) acrylate polymer (A) may be a solution polymerized polymer, a polymer obtained without solvent, or an emulsion polymerized polymer. Among them, a solution polymer obtained by a solution polymerization method is preferable. By being a solution polymer, a linear polymer having a high molecular weight can be easily obtained, and the first pressure-sensitive adhesive layer 12 can have more excellent electrolytic solution resistance.

  The polymerization mode of the (meth) acrylate polymer (A) may be a random copolymer or a block copolymer.

  The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 50,000 or more as a lower limit, more preferably 100,000 or more, particularly preferably 200,000 or more, and furthermore Is preferably 500,000 or more. When the lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is as described above, the first pressure-sensitive adhesive layer 12 to be formed has more excellent elution resistance to the electrolytic solution.

  The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2.5 million or less as an upper limit, more preferably 2 million or less, and particularly preferably 1.2 million or less. And more preferably 950,000 or less. When the upper limit of the weight average molecular weight of the (meth) acrylate polymer (A) is as described above, the adhesion between the first pressure-sensitive adhesive layer 12 and the base material 11 and the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer Of the adhesive layer 13 is more excellent. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method.

  In the pressure-sensitive adhesive composition P1, one type of the (meth) acrylate polymer (A) may be used alone, or two or more types may be used in combination.

(2-2) Crosslinking agent (B)
The crosslinking agent (B) may be any as long as it reacts with the reactive functional group of the (meth) acrylate polymer (A). For example, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, and an amine-based crosslinking agent , Melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, ammonium salt-based crosslinking agents, etc. Is mentioned. As the crosslinking agent (B), one type may be used alone, or two or more types may be used in combination.

  Among the above, the viewpoint of the reactivity with the reactive functional group of the (meth) acrylic acid ester polymer (A), particularly the carboxy group derived from the carboxy group-containing monomer, the electrolytic solution resistance after the reaction, the insulation performance and the like. Therefore, it is preferable to use an isocyanate-based crosslinking agent.

  The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. As the polyisocyanate compound, for example, aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, etc. And their biuret forms, isocyanurate forms, and adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Above all, from the viewpoint of reactivity with carboxy groups, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are preferred.

  The content of the crosslinking agent (B) in the adhesive composition P1 is preferably not less than 0.1 part by mass as a lower limit, based on 100 parts by mass of the (meth) acrylate polymer (A). In particular, it is preferably at least 0.5 part by mass, more preferably at least 1 part by mass. Further, the content is, as an upper limit value, preferably 20 parts by mass or less, particularly preferably 15 parts by mass or less, and further preferably 10 parts by mass or less. When the content of the cross-linking agent (B) is in the above range, a cross-linked structure is formed favorably, and the cohesive force of the formed first pressure-sensitive adhesive layer 12 becomes moderately high. Is more excellent in elution resistance.

(2-3) Various additives The pressure-sensitive adhesive composition P1 optionally contains various additives commonly used in acrylic pressure-sensitive adhesives, such as tackifiers, antioxidants, softeners, and fillers. be able to. In addition, the polymerization solvent and the diluting solvent described below are not included in the additives constituting the adhesive composition P1.

(3) Production of Adhesive Composition P1 Adhesive composition P1 produced (meth) acrylate polymer (A), and obtained (meth) acrylate polymer (A) was added with inorganic fine particles. 121 and, if desired, a crosslinking agent (B), an additive or the like.

  The (meth) acrylate polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a usual radical polymerization method. The polymerization of the (meth) acrylate polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator, if desired. However, the present invention is not limited to this, and polymerization may be performed without a solvent. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like, and two or more kinds may be used in combination.

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), , 2'-Azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate) 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2- (2-imidazolin-2-yl) Propane] and the like.

  Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxy dicarbonate, di-n-propyl peroxy dicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxy neodecanoate, t-butyl peroxy bivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In the above polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

  When the (meth) acrylate polymer (A) is obtained, the inorganic fine particles 121 and, if desired, a crosslinking agent (B) and additives are added to the solution of the (meth) acrylate polymer (A). Then, by sufficiently mixing, an adhesive composition P1 is obtained.

  In addition, in order to adjust the viscosity of the pressure-sensitive adhesive composition P1 to an appropriate level for coating or to adjust the first pressure-sensitive adhesive layer 12 to a desired film thickness, the pressure-sensitive adhesive composition P1 may be appropriately added to the above-described polymerization solvent and diluted with a diluting solvent or the like. It may be diluted to obtain a coating liquid described later. Examples of the diluting solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like, and two or more kinds may be used in combination.

(4) Crosslinking of Adhesive Composition P1 When the adhesive composition P1 contains a crosslinking agent (B), the first adhesive layer 12 can be formed by crosslinking the adhesive composition P1. . Crosslinking of the adhesive composition P1 can be usually performed by a heat treatment. In addition, this heat treatment can also serve as a drying treatment when a diluting solvent or the like is volatilized from the coating film of the adhesive composition P1 applied to a desired object.

  The heating temperature of the heat treatment is preferably from 50 to 150 ° C, particularly preferably from 70 to 120 ° C. Further, the heating time is preferably from 30 seconds to 10 minutes, and particularly preferably from 50 seconds to 5 minutes.

  After the heat treatment, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23 ° C., 50% RH) as necessary. When the curing period is required, the first pressure-sensitive adhesive layer 12 is formed after the curing period has elapsed, and when the curing period is not required, after the heat treatment is completed.

(5) Thickness of First Pressure-Sensitive Adhesive Layer The thickness of the first pressure-sensitive adhesive layer 12 (a value measured according to JIS K7130) is preferably 1 μm or more as a lower limit, more preferably 3 μm or more. Preferably, it is more preferably 5 μm or more. When the lower limit of the thickness of the first pressure-sensitive adhesive layer 12 is as described above, the battery pressure-sensitive adhesive sheet 1 easily exhibits high insulation properties. Further, the thickness of the first pressure-sensitive adhesive layer 12 is, as an upper limit, preferably 50 μm or less, particularly preferably 13 μm or less, and further preferably 9 μm or less. When the upper limit of the thickness of the first pressure-sensitive adhesive layer 12 is as described above, the amount of the electrolyte solution that enters from the end of the first pressure-sensitive adhesive layer 12 can be effectively reduced.

  Further, the thickness of the first pressure-sensitive adhesive layer 12 is preferably 1.1 times or more, more preferably 5 times or more, and more preferably 10 times or more of the average particle size of the inorganic fine particles 121. It is particularly preferable, and more preferably 15 times or more. When the thickness of the first pressure-sensitive adhesive layer 12 is 1.1 times or more the average particle diameter of the inorganic fine particles 121, the smoothness of the surface of the first pressure-sensitive adhesive layer 12 becomes more excellent, whereby It is possible to improve the smoothness of the surface of the second pressure-sensitive adhesive layer 13 that is laminated on the first pressure-sensitive adhesive layer 12 on the side opposite to the first pressure-sensitive adhesive layer 12 and effectively obtain a high adhesive force. it can. The upper limit of the magnification of the thickness of the first pressure-sensitive adhesive layer 12 based on the average particle size of the inorganic fine particles 121 is not particularly limited, but is preferably 100 times or less, more preferably 60 times or less. It is particularly preferably 30 times or less.

1-3. Second pressure-sensitive adhesive layer The second pressure-sensitive adhesive layer 13 contains a pressure-sensitive adhesive component. The pressure-sensitive adhesive component contained in the second pressure-sensitive adhesive layer 13 can be appropriately selected from the viewpoints of tackiness, elution to an electrolytic solution, flame retardancy, heat resistance, insulation, and the like. As the pressure-sensitive adhesive component contained in the second pressure-sensitive adhesive layer 13, those described above as the pressure-sensitive adhesive component contained in the first pressure-sensitive adhesive layer 12 can be used. The pressure-sensitive adhesive component contained in the second pressure-sensitive adhesive layer 13 may be the same or different from the pressure-sensitive adhesive component contained in the first pressure-sensitive adhesive layer 12. However, from the viewpoint that the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 are likely to have good adhesion, the pressure-sensitive adhesive component contained in the second pressure-sensitive adhesive layer 13 is the first pressure-sensitive adhesive layer. It is preferable that it is of the same kind as the pressure-sensitive adhesive component contained in the pressure-sensitive adhesive layer 12. Note that the second pressure-sensitive adhesive layer 13 does not include the inorganic fine particles 121 described above.

  When an acrylic pressure-sensitive adhesive component is used as the pressure-sensitive adhesive component contained in the second pressure-sensitive adhesive layer 13, the acrylic pressure-sensitive adhesive component includes the (meth) acrylate polymer (A) described above and the cross-linking agent (B) described above. ) Is preferable. The second pressure-sensitive adhesive layer 13 is formed of a second pressure-sensitive adhesive containing the (meth) acrylate polymer (A), the cross-linking agent (B), and, if desired, the various additives described above. It is preferably obtained from a pressure-sensitive adhesive composition for an agent layer (hereinafter sometimes referred to as “pressure-sensitive adhesive composition P2”). The adhesive composition P2 can be manufactured in the same manner as the adhesive composition P1. When the adhesive composition P2 contains the crosslinking agent (B), the adhesive composition P2 can be crosslinked in the same manner as the adhesive composition P1.

  The lower limit of the thickness of the second pressure-sensitive adhesive layer 13 (measured according to JIS K7130) is preferably 1 μm or more, particularly preferably 3 μm or more, and more preferably 5 μm or more. Is preferred. When the lower limit value of the thickness of the second pressure-sensitive adhesive layer 13 is as described above, the pressure-sensitive adhesive sheet 1 for a battery can easily exhibit excellent adhesive strength. The upper limit of the thickness of the second pressure-sensitive adhesive layer 13 is preferably 50 μm or less, particularly preferably 13 μm or less, and further preferably 9 μm or less. When the upper limit value of the thickness of the second pressure-sensitive adhesive layer 13 is as described above, the amount of the electrolyte that enters from the end of the second pressure-sensitive adhesive layer 13 can be effectively reduced.

1-4. Release Sheet The release sheet 14 protects the second pressure-sensitive adhesive layer 13 until the battery pressure-sensitive adhesive sheet 1 is used, and is peeled off when the battery pressure-sensitive adhesive sheet 1 is used. In the battery adhesive sheet 1 according to the present embodiment, the release sheet 14 is not always necessary.

  Examples of the release sheet 14 include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, and a polybutylene terephthalate film. , Polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film And a liquid crystal polymer film. These crosslinked films are also used. Further, these laminated films may be used.

  The release surface of the release sheet 14 (the surface in contact with the second pressure-sensitive adhesive layer 13) is preferably subjected to a release treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

  The thickness of the release sheet 14 is not particularly limited, but is usually about 20 to 150 μm.

2. Physical Properties of Battery Adhesive Sheet, etc. (1) Adhesive Force The adhesive force of the battery adhesive sheet 1 according to the present embodiment to an aluminum plate is preferably 0.5 N / 25 mm or more as a lower limit, and 1.0 N / 25 mm. It is more preferably at least 2.0 N / 25 mm, particularly preferably at least 2.5 N / 25 mm. When the lower limit value of the adhesive force of the battery pressure-sensitive adhesive sheet 1 is as described above, a problem that the battery pressure-sensitive adhesive sheet 1 peels off from an adherend (particularly a metal member) hardly occurs. Although the upper limit of the adhesive force is not particularly limited, it is usually preferably 50 N / 25 mm or less, particularly preferably 40 N / 25 mm or less, and further preferably 30 N / 25 mm or less. In addition, the adhesive force in this specification basically refers to the adhesive force measured by a 180 ° peeling method according to JIS Z0237: 2009, and the detailed measuring method is as shown in a test example described later.

(2) Insulation (temperature rise by forced internal short-circuit test)
With respect to the battery adhesive sheet 1 (excluding the release sheet 14), the temperature rise on the side of the battery when a forced internal short-circuit test of the battery was performed in accordance with JIS C8714: 2007 was a standard size (height: 0.2 mm, width: In the case of using a small piece of nickel having an L-shape of 0.1 mm and a side length of 1 mm and an angle of 90 °), the temperature is preferably 30 ° C or lower, particularly preferably 20 ° C or lower, and more preferably 15 ° C or lower. preferable. Further, when a nickel piece having a size larger than the standard size (height: 0.5, width: 0.2 mm, L-shaped side of 3 mm, angle 90 °) is used, the temperature is preferably 100 ° C or less, particularly 50 ° C or less. And more preferably 30 ° C. or lower. Details of the forced internal short-circuit test are as shown in a test example described later.

  Since the temperature rise in the forced internal short-circuit test is as described above, the battery pressure-sensitive adhesive sheet 1 can be said to have high insulation properties, and the battery using the battery pressure-sensitive adhesive sheet 1 has high safety. Since the battery pressure-sensitive adhesive sheet 1 according to the present embodiment includes the first pressure-sensitive adhesive layer 12 containing the inorganic fine particles 121, the temperature rise due to the forced internal short-circuit test can be suppressed as described above.

(3) Thickness of Battery Adhesive Sheet The thickness of the battery adhesive sheet 1 (excluding the thickness of the release sheet 14) is preferably 10 μm or more, particularly preferably 15 μm or more, and further preferably 20 μm. It is preferable that it is above. Further, the thickness of the battery pressure-sensitive adhesive sheet 1 is preferably 250 μm or less, particularly preferably 110 μm or less, and further preferably 45 μm or less. When the thickness of the battery pressure-sensitive adhesive sheet 1 is within the above range, it becomes easy to achieve both excellent adhesive strength and high insulating property.

3. Method for Manufacturing Pressure-Sensitive Sheet for Battery As a method for manufacturing the pressure-sensitive adhesive sheet 1 for a battery according to the present embodiment, a first pressure-sensitive adhesive layer 12 and a second pressure-sensitive adhesive layer 13 are formed in this order on one side of a substrate 11. There is no particular limitation as long as it can be performed. As an example, after preparing a first laminate including the base material 11 and the first pressure-sensitive adhesive layer 12, and a second laminate including the second pressure-sensitive adhesive layer 13 and the release sheet 14, respectively, By bonding these laminates so that the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 are in contact with each other, the battery pressure-sensitive adhesive sheet 1 can be manufactured.

  The first laminate including the base material 11 and the first pressure-sensitive adhesive layer 12 can be manufactured, for example, as follows. The coating liquid containing the above-mentioned adhesive composition P1 and, if desired, a solvent is applied to one surface of the substrate 11, and a heat treatment is performed to form a coating film. When the curing period is unnecessary, the formed coating film becomes the first pressure-sensitive adhesive layer 12 as it is, and when the curing period is required, it becomes the first pressure-sensitive adhesive layer 12 after the lapse of the curing period. Thereby, a first laminate in which the first pressure-sensitive adhesive layer 12 is formed on the base material 11 can be obtained.

  The above-mentioned heat treatment can also serve as a drying treatment for volatilizing a diluting solvent or the like of the coating solution. When performing a heat treatment, the heating temperature is preferably from 50 to 150 ° C, particularly preferably from 70 to 120 ° C. Further, the heating time is preferably from 30 seconds to 10 minutes, particularly preferably from 50 seconds to 2 minutes. After the heat treatment, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23 ° C., 50% RH) as necessary.

  The second laminate including the second pressure-sensitive adhesive layer 13 and the release sheet 14 can be manufactured in the same manner as the first laminate. However, when producing the second laminate, the above-mentioned coating film is formed by applying the coating composition containing the above-mentioned adhesive composition P2 and optionally a solvent to the release surface of the release sheet 14. I do.

  After laminating the first laminate and the second laminate, a curing period may be provided as necessary.

  As another method for producing the pressure-sensitive adhesive sheet 1 for a battery according to the present embodiment, the above-described pressure-sensitive adhesive composition P1 and pressure-sensitive adhesive composition P2 are simultaneously multi-layer coated on the release surface of the release sheet 14, and After preparing a laminate in which the second pressure-sensitive adhesive layer 13 and the first pressure-sensitive adhesive layer 12 are laminated in this order, one surface of the base material 11 is bonded to the surface of the laminate on the first pressure-sensitive adhesive layer 12 side. Then, the pressure-sensitive adhesive sheet 1 for a battery may be obtained. Alternatively, the above-mentioned pressure-sensitive adhesive composition P1 and pressure-sensitive adhesive composition P2 are simultaneously and multi-layer coated on one surface of the base material 11, and the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 are formed on the base material 11. By forming the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet 1 for a battery may be manufactured.

  The above-described simultaneous multilayer coating can be performed by a known method, for example, a curtain coating method, a die coating method, a slide beat coating method, or the like. Further, the pressure-sensitive adhesive composition P1 and the pressure-sensitive adhesive composition P2 may each be diluted with a desired solvent from the viewpoint of performing simultaneous multilayer coating well.

[Lithium ion battery]
A lithium-ion battery according to one embodiment of the present invention is a battery in which two or more conductors are in contact with each other using the above-mentioned battery adhesive sheet 1 inside the battery. Preferably, at least one of the two or more conductors is sheet-shaped, and at least one is linear or tape-shaped. Hereinafter, a lithium ion battery according to a preferred embodiment will be described.

  As shown in FIG. 2, the lithium ion battery 2 according to the present embodiment includes a bottomed cylindrical exterior body 21 having a bottom portion constituting a negative electrode terminal 23, and a positive electrode terminal 22 provided in an opening of the exterior body 21. And an electrode body 24 provided inside the exterior body 21. An electrolyte is sealed inside the lithium ion battery 2.

  The electrode body 24 includes a sheet-shaped (strip-shaped) positive electrode current collector 241 in which the positive electrode active material layers 241a are stacked, a negative electrode current collector 242 in which the negative electrode active material layers 242a are stacked, and And an intervening separator 243. Note that a stacked body of the positive electrode current collector 241 and the positive electrode active material layer 241a may be referred to as a positive electrode, and a stacked body of the negative electrode current collector 242 and the negative electrode active material layer 242a may be referred to as a negative electrode. It is sometimes called an electrode. The positive electrode, the negative electrode, and the separator 243 are respectively wound and inserted into the exterior body 21.

  As shown in FIG. 3, a linear or tape-shaped electrode extraction tab 244 is attached to the positive electrode current collector 241 by the above-described battery adhesive sheet 1, whereby the electrode extraction tab 244 is It is electrically connected to the positive electrode current collector 241. The electrode extraction tab 244 is also electrically connected to the positive terminal 22. Note that the negative electrode current collector 242 is electrically connected to the negative electrode terminal 23 via an electrode extraction tab (not shown).

  Generally, the positive electrode current collector 241 and the negative electrode current collector 242 are made of a metal such as aluminum, and the electrode extraction tab 244 is made of a metal such as aluminum or copper.

The electrolyte used in the lithium ion battery 2 is usually a non-aqueous electrolyte. As the non-aqueous electrolyte, for example, a solution in which a lithium salt as an electrolyte is dissolved in a mixed solvent of a cyclic carbonate and a lower chain carbonate is preferably exemplified. Examples of the lithium salt include fluorinated complex salts such as lithium hexafluorophosphate (LiPF ₆ ) and lithium borofluoride (LiBF ₄ ), and LiN (SO ₂ Rf) ₂ · LiC (SO ₂ Rf) ₃ (where Rf = CF ₃ , C ₂ F ₅ ) and the like are used. As the cyclic carbonate, ethylene carbonate, propylene carbonate and the like are used, and as the lower chain carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and the like are preferable.

  The lithium ion battery 2 according to the present embodiment can be manufactured by an ordinary method except that the above-mentioned battery adhesive sheet 1 is used for fixing the electrode take-out tab 244.

  In the lithium ion battery 2 according to the present embodiment, the electrode take-out tab 244 is attached to the positive electrode current collector 241 using the battery adhesive sheet 1. The battery pressure-sensitive adhesive sheet 1 is provided with the first pressure-sensitive adhesive layer 12 containing the inorganic fine particles 121 and the second pressure-sensitive adhesive layer 13 not containing the inorganic fine particles 121, thereby exhibiting excellent adhesive strength. And has high insulation properties. Thereby, the lithium ion battery 2 according to the present embodiment is unlikely to cause a problem such as a poor contact between the positive electrode current collector 241 and the electrode extraction tab 244, and even if an internal short circuit occurs in the battery adhesive sheet 1 portion, The temperature rise due to heat can be suppressed low, and high safety can be exhibited.

  The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the pressure-sensitive adhesive sheet 1 for a battery, the release sheet 14 may be omitted. In the pressure-sensitive adhesive sheet 1 for a battery, another layer is provided between the base material 11 and the first pressure-sensitive adhesive layer 12 or between the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13. It may be provided.

  Hereinafter, the present invention will be described more specifically with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]
1. Preparation of Coating Solution for Adhesive Composition 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of lauryl methacrylate and 5 parts by mass of acrylic acid were copolymerized by a solution polymerization method to prepare a (meth) acrylate polymer. . When the molecular weight of this polymer was measured using gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 750,000.

  Next, 100 parts by mass of the obtained (meth) acrylic acid ester polymer (in terms of solid content; the same applies hereinafter) and trimethylolpropane-modified tolylene diisocyanate as an isocyanate-based cross-linking agent (trade name “BHS8515, manufactured by Toyochem Co., Ltd.) )) And mixed with 3.72 parts by mass, and diluted with ethyl acetate to obtain a coating solution (solid content: 30%) of the second pressure-sensitive adhesive composition for a pressure-sensitive adhesive layer. The coating liquid contains the (meth) acrylic acid ester polymer and the isocyanate-based crosslinking agent as adhesive components.

  Further, with respect to the coating solution of the second pressure-sensitive adhesive layer-forming pressure-sensitive adhesive composition prepared in the same manner as above, 100 parts by mass of the above-mentioned pressure-sensitive adhesive component was added to alumina fine particles as inorganic fine particles (product name "ASFP" manufactured by Denka Corporation). -20 ", average particle size: 0.26 µm) 155 parts by mass were added and mixed to obtain a coating solution of the first pressure-sensitive adhesive layer-forming pressure-sensitive adhesive composition.

2. Formation of First Pressure-Sensitive Adhesive Layer One side of a polyimide film as a base material (trade name “Kapton 100H”, manufactured by Toray Dupont Co., Ltd., thickness 25 μm, UL94 standard flame retardant level V-0) Is applied with a knife coater, and the obtained coating film is dried at 120 ° C. for 1 minute to form a first pressure-sensitive adhesive layer having a thickness of 5 μm. Formed. As a result, a first laminate including the base material and the first pressure-sensitive adhesive layer was obtained.

3. Formation of Second Pressure-Sensitive Adhesive Layer A release sheet (Rintech Co., Ltd.) obtained by subjecting one side of a polyethylene terephthalate film to a coating treatment of the second pressure-sensitive adhesive layer-obtained pressure-sensitive adhesive composition obtained in the above step 1 with a silicone-based release agent (Trade name: “SP-PET251130”), was coated with a knife coater, and the obtained coating film was dried at 120 ° C. for 1 minute to form a second pressure-sensitive adhesive layer having a thickness of 5 μm. Thus, a second laminate including the release sheet and the second pressure-sensitive adhesive layer was obtained.

4. Production of Battery Pressure-Sensitive Sheet The surface of the first laminate obtained in the above step 2 on the first pressure-sensitive adhesive layer side and the surface of the second laminate obtained in the above step 3 on the second pressure-sensitive adhesive layer side And then cured at 23 ° C. and 50% RH for 7 days, whereby the base material, the first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and the release sheet are in this order. A laminated pressure-sensitive adhesive sheet for a battery was obtained.

Here, the above-mentioned weight average molecular weight (Mw) is a weight average molecular weight in terms of standard polystyrene measured (GPC measurement) using gel permeation chromatography (GPC) under the following conditions.
<Measurement conditions>
・ GPC measuring device: HLC-8320 manufactured by Tosoh Corporation
GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation
TSK gel super HM-H
TSK gel superH2000
-Measurement solvent: tetrahydrofuran-Measurement temperature: 40 ° C

[Examples 2 to 5]
A pressure-sensitive adhesive sheet for a battery was produced in the same manner as in Example 1, except that the type and amount of the inorganic fine particles were changed as shown in Table 1.

[Comparative Example 1]
A coating liquid of the first pressure-sensitive adhesive layer-forming pressure-sensitive adhesive composition obtained in Step 1 of Example 1 was applied to a polyimide film (trade name “Kapton 100H”, manufactured by Toray DuPont, thickness 25 μm, UL94) as a substrate. One surface of the standard flame retardant level V-0) was applied with a knife coater, and the obtained coating film was dried at 120 ° C. for 1 minute to form a first pressure-sensitive adhesive layer having a thickness of 10 μm.

  Subsequently, on the surface of the formed first pressure-sensitive adhesive layer opposite to the substrate, a release sheet (trade name “SP-PET251130”, manufactured by Lintec Co., Ltd.) obtained by releasing one surface of a polyethylene terephthalate film with a silicone-based release agent ), And then cured at 23 ° C. and 50% RH for 7 days, so that a substrate, a first pressure-sensitive adhesive layer, and a release sheet are laminated in this order for a battery. An adhesive sheet was obtained.

[Comparative Example 2]
A release sheet (trade name: “SP”, manufactured by Lintec Co., Ltd.) obtained by subjecting the coating liquid of the first pressure-sensitive adhesive layer adhesive composition obtained in step 1 of Example 1 to a release treatment on one side of a polyethylene terephthalate film with a silicone-based release agent -PET251130 ") was applied by a knife coater, and the obtained coating film was dried at 120 ° C for 1 minute to form a first pressure-sensitive adhesive layer having a thickness of 10 µm.

  Subsequently, on the surface of the formed first pressure-sensitive adhesive layer opposite to the release sheet, a polyimide film as a base material (manufactured by Toray DuPont, trade name “Kapton 100H”, thickness 25 μm, UL94 standard flame retardant) One side of Level V-0) is bonded, and then cured at 23 ° C. and 50% RH for 7 days, whereby the base material, the first pressure-sensitive adhesive layer, and the release sheet are laminated in this order. Was obtained.

[Comparative Example 3]
A release sheet (trade name, manufactured by Lintec Co., Ltd.) obtained by applying a coating solution of the second pressure-sensitive adhesive layer-obtained adhesive composition obtained in step 1 of Example 1 to a polyethylene terephthalate film on one side with a silicone-based release agent. SP-PET251130 ”) was applied to the release-treated surface with a knife coater, and the obtained coating film was dried at 120 ° C. for 1 minute to form a second pressure-sensitive adhesive layer having a thickness of 10 μm.

  Subsequently, on the surface of the formed second pressure-sensitive adhesive layer opposite to the release sheet, a polyimide film as a base material (trade name “Kapton 100H”, manufactured by Toray DuPont, thickness 25 μm, UL94 standard flame retardant) One side of the level V-0) is bonded, and then cured at 23 ° C. and 50% RH for 7 days, whereby the base material, the second pressure-sensitive adhesive layer, and the release sheet are laminated in this order. Was obtained.

[Test Example 1] (Measurement of adhesive strength)
The adhesive strength of the battery adhesive sheet according to this test example was measured according to JIS Z0237: 2009, except for the following operations.

  The test pieces were obtained by cutting the pressure-sensitive adhesive sheets for batteries obtained in Examples and Comparative Examples into a width of 25 mm and a length of 250 mm, and then peeling off the release sheet. 2 kg of the exposed second pressure-sensitive adhesive layer (the first pressure-sensitive adhesive layer for Comparative Examples 1 and 2) of this test piece was placed on an aluminum plate as an adherend in an environment of 23 ° C. and 50% RH. It was attached using a rubber roller. Immediately thereafter, the test piece was peeled off from the aluminum plate at a peeling angle of 180 ° and a peeling speed of 300 mm / min using a universal tensile tester (manufactured by Orientec, product name “Tensilon UTM-4-100”). The adhesive force (N / 25 mm) was measured. Table 1 shows the results.

[Test Example 2] (Evaluation of electrolytic solution resistance)
After the pressure-sensitive adhesive sheets for batteries obtained in Examples and Comparative Examples were cut into a width of 11 mm and a length of 30 mm, the release sheet was peeled off. Next, the exposed second pressure-sensitive adhesive layer (the first pressure-sensitive adhesive layer in Comparative Examples 1 and 2) was applied to an aluminum plate as an adherend by a 2 kg rubber roller under an environment of 23 ° C. and 50% RH. And was used as a test piece. This test piece was prepared together with an electrolytic solution prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) at a concentration of 1 mol / L in a mixed solution of ethylene carbonate and diethyl carbonate mixed at a volume ratio of 1: 1. It was sealed in an aluminum laminate bag and heated at 80 ° C. for 3 days. Thereafter, the test piece was taken out, and the adhesive sheet for a battery was peeled from the aluminum plate with tweezers, and the ease of peeling at that time was confirmed. Then, the electrolytic solution resistance was evaluated based on the following criteria. Table 1 shows the results.
3: peeled off at the interface between the second pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer for Comparative Examples 1 and 2) and the adherend.
2: The second pressure-sensitive adhesive layer (the first pressure-sensitive adhesive layer in Comparative Examples 1 and 2) swelled and was cohesively broken or transferred.
1: peeled off in an aluminum laminate bag.

[Test Example 3] (Evaluation of battery insulation)
(1) Production of Positive Electrode 100 parts by mass of LiNi _0.82 Co _0.15 Al _0.03 O ₂ , 1.0 part by mass of acetylene black, and 0.9 parts by mass of polyvinylidene fluoride as a positive electrode active material (Binder) and an appropriate amount of NMP were mixed to prepare a positive electrode paste. The obtained positive electrode paste was uniformly applied to both sides of a 20-μm-thick aluminum foil serving as a positive electrode current collector, dried, and then rolled to produce a 58 mm-wide strip-shaped positive electrode. However, on both surfaces near the center in the longitudinal direction of the positive electrode, a slit-shaped exposed portion from one end to the other end in the width direction of the positive electrode current collector was provided. At this time, the width W of the exposed portion was 6.5 mm.

  Next, a strip-shaped positive electrode lead made of aluminum having a width of 3.5 mm and a length of 68 mm is superimposed on the exposed portion of the positive electrode current collector so that the length of the lead portion becomes 15 mm and the length of the overlapping portion becomes 53 mm. And the overlapped portion was welded to the exposed portion.

  Thereafter, the pressure-sensitive adhesive sheets for batteries obtained in Examples and Comparative Examples were affixed to the positive electrode such that the entire surface of the exposed portion and the entire surface of the overlapping portion were covered. At this time, the battery adhesive sheet was protruded by 2 mm from both ends in the width direction of the positive electrode so that the exposed portion was surely covered with the battery adhesive sheet. Also, the battery adhesive sheet was protruded by 2 mm from the both ends in the width direction of the exposed portion onto the positive electrode active material layer.

(2) Preparation of Negative Electrode 100 parts by mass of flaky artificial graphite having an average particle diameter of about 20 μm, 1 part by mass of styrene butadiene rubber (SBR) (binder), and 1 part by mass of carboxy Methyl cellulose (thickener) and water were mixed to prepare a negative electrode paste. The obtained negative electrode paste was uniformly applied on both sides of a copper foil having a thickness of 8 μm as a negative electrode current collector, dried, and rolled to prepare a strip-shaped negative electrode having a width of 59 mm. However, exposed portions were provided on both surfaces of the end portion on the winding end side of the negative electrode, from the one end to the other end in the width direction of the negative electrode current collector.

  Next, a strip-shaped nickel negative electrode lead having a width of 3 mm and a length of 40 mm was overlaid on the exposed portion of the negative electrode current collector, aligned in the same manner as the positive electrode, and the overlapped portion was welded to the exposed portion.

(3) Preparation of electrode group The positive electrode and the negative electrode obtained above were laminated with a separator interposed therebetween, and wound to form an electrode group. At this time, the lead portion of the positive electrode lead protruded from one end surface of the electrode group, and the lead portion of the negative electrode lead protruded from the other end surface.

(4) Preparation of Nonaqueous Electrolyte LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 1: 1: 8) to a concentration of 1.4 mol / L. To prepare a non-aqueous electrolyte.

(5) Production of Battery An electrode group sandwiched between a lower insulating ring and an upper insulating ring was housed in an iron battery case (diameter: 18 mm, height: 65 mm) with nickel plating on the inner surface. At this time, the negative electrode lead was interposed between the lower insulating ring and the bottom of the battery case. Further, the center lead of the upper insulating ring was passed through the positive electrode lead. Next, one end of the negative electrode lead was welded to the inner bottom surface of the battery case by passing an electrode rod through a hollow portion at the center of the electrode group and a through hole at the center of the lower insulating ring. Further, one end of the positive electrode lead pulled out from the through hole of the upper insulating ring was welded to the inner surface of a sealing plate provided with a gasket on the periphery. Thereafter, a groove was formed in the vicinity of the opening of the battery case, a non-aqueous electrolyte was injected into the battery case, and the electrode group was impregnated. Next, the opening of the battery case is closed with a sealing plate, and the opening end of the battery case is swaged to the peripheral edge of the sealing plate via a gasket to form a cylindrical non-aqueous electrolyte secondary battery (energy density 700 Wh / L). Was completed.

(6) Implementation of forced internal short-circuit test Using the non-aqueous electrolyte secondary battery obtained above, a forced internal short-circuit test of the battery was performed in accordance with JIS C8714: 2007. Nickel pieces are available in standard sizes (height: 0.2 mm, width: 0.1 mm, L-shape with 1 mm on each side, angle 90 °) and in sizes larger than the standard size (height: 0.5, width: 0.2 mm, An L-shape having a side of 3 mm and an angle of 90 °) was prepared. These nickel pieces were arranged between the battery adhesive sheet and the separator such that the nickel pieces penetrated the battery adhesive sheet. Then, a forced internal short-circuit test was performed, and the temperature rise (° C.) on the side of the battery was measured with a thermocouple. Table 1 shows the results.

The details of the abbreviations and the like described in Table 1 are as follows.
[Inorganic fine particles]
Alumina: Alumina fine particles (manufactured by Denka Co., Ltd., product name “ASPP-20”, average particle size: 0.26 μm)
Titania: Titania fine particles (manufactured by Sakai Chemical Industry Co., Ltd., product name “R-310”, average particle size: 0.2 μm)
Calcium carbonate: calcium carbonate fine particles (Kamijima Chemical Co., Ltd., product name "light calcium carbonate", average particle size: 1.1 μm)

  As is clear from Table 1, the pressure-sensitive adhesive sheets for batteries of Examples have good adhesive strength and electrolytic solution resistance, and also have high insulating properties, and suppress the temperature rise due to the forced internal short-circuit test. Was completed.

  The pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet for a battery according to the present invention are suitable for use inside a lithium ion battery, and are particularly suitable for attaching an electrode extraction tab to an electrode.

DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet for batteries 11 ... Base material 12 ... First adhesive layer 121 ... Inorganic fine particles 13 ... Second adhesive layer 14 ... Release sheet 2 ... Lithium ion battery 21 ... Outer body 22 ... Positive electrode terminal 23 ... Negative electrode Terminal 24 ... Electrode body 241 ... Positive electrode current collector 241a ... Positive electrode active material layer 242 ... Negative electrode current collector 242a ... Negative electrode active material layer 243 ... Separator 244 ... Electrode extraction tab

Claims (6)

A substrate,
A first pressure-sensitive adhesive layer containing inorganic fine particles, provided on one surface side of the base material,
A pressure-sensitive adhesive sheet for a battery, comprising: a second pressure-sensitive adhesive layer that does not contain the inorganic fine particles and is provided on a surface of the first pressure-sensitive adhesive layer opposite to the base material.   The content of the inorganic fine particles in the first pressure-sensitive adhesive layer is not less than 50 parts by mass and not more than 1000 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive component contained in the first pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet for a battery according to claim 1, wherein   3. The pressure-sensitive adhesive sheet for a battery according to claim 1, wherein the thickness of the first pressure-sensitive adhesive layer is 1 μm or more and 50 μm or less. 4.   The pressure-sensitive adhesive sheet for a battery according to any one of claims 1 to 3, wherein the thickness of the second pressure-sensitive adhesive layer is 1 µm or more and 50 µm or less.   The adhesive sheet for a battery according to any one of claims 1 to 4, wherein the adhesive force of the adhesive sheet for a battery to an aluminum plate is 0.5 N / 25 mm or more and 50 N / 25 mm or less.   A lithium ion, wherein two or more conductors are fixed in contact with each other using the pressure-sensitive adhesive sheet for a battery according to any one of claims 1 to 5 inside the battery. battery.

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