JP6855415B2 - Adhesive sheet for batteries and lithium-ion batteries - Google Patents

Description

The present invention relates to an adhesive sheet for a battery, an adhesive composition for forming an adhesive layer of the adhesive sheet for a battery, and a lithium ion battery manufactured by using the adhesive composition.

In some batteries, a strip-shaped laminate in which a positive electrode, a negative electrode, and a separator located between them are laminated is housed inside in a wound state. An electrode take-out tab made of a conductor is 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, respectively, through these electrode take-out tabs. ..

Adhesive tape is used for winding the laminate and fixing the electrode take-out tab to the electrode. Patent Document 1 discloses such an adhesive tape. This adhesive tape is composed of a base material and a pressure-sensitive adhesive layer provided on one surface of the base material, and the pressure-sensitive adhesive layer is made of rubber, particularly butyl rubber as a main component.

Japanese Unexamined Patent Publication No. 2011-138632

The adhesive tape used inside the battery may come into contact with the electrolytic solution filled inside the battery, or may be exposed to heat generated during charging / discharging or the like. Particularly in recent years, the development of small and high-performance batteries has been promoted, and the adhesive tape used inside the batteries is exposed to more severe conditions.

In order to achieve good battery performance, the adhesive tape should maintain high adhesion to the adherend even when exposed to the harsh conditions described above, and the adhesive should be used. It is required that it does not elute into the electrolytic solution and does not adversely affect the battery performance. However, conventional adhesive tapes may not be able to sufficiently meet such requirements.

The present invention has been made in view of such an actual situation, and even when the adhesive sheet comes into contact with the electrolytic solution, it exhibits good adhesive force to the adherend and the adhesive is electrolyzed. It is an object of the present invention to provide an adhesive composition which is difficult to elute into a liquid, an adhesive sheet for a battery, and a lithium ion battery.

In order to achieve the above object, first, the present invention is a pressure-sensitive adhesive sheet for a battery including a base material and a pressure-sensitive adhesive layer laminated on one surface side of the base material. A film made of a polymer having a nitrogen-containing ring structure in the main chain, and the pressure-sensitive adhesive layer is a (meth) acrylic having 6 or more and 20 or less carbon atoms of an alkyl group as a monomer unit constituting the polymer. It is formed from an acid alkyl ester and a tacky composition containing a (meth) acrylic acid ester polymer containing a monomer having a carboxy group in the molecule and having a weight average molecular weight of 50,000 or more and 2.5 million or less. It is characterized in that the gel content of the pressure-sensitive adhesive after immersing the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer in a solvent of a non-aqueous electrolyte solution at 80 ° C. for 72 hours is 80% or more and 100% or less. Provided is an adhesive sheet for a battery (Invention 1). In this specification, the sheet also includes the concept of tape.

In the above invention (Invention 1), the (meth) acrylic acid ester polymer is a (meth) acrylic acid having an alkyl group having 6 or more carbon atoms and 20 or less carbon atoms as a monomer unit constituting the polymer. By containing an alkyl ester, it exhibits good adhesiveness and also has excellent electrolytic solution resistance due to its hydrophobicity. Therefore, when the pressure-sensitive adhesive layer of the battery pressure-sensitive adhesive sheet is formed by the pressure-sensitive adhesive composition according to the above invention (Invention 1), the pressure-sensitive adhesive layer swells even when the battery pressure-sensitive adhesive sheet comes into contact with the electrolytic solution. It suppresses coagulation and fracture, exerts excellent adhesive strength to the adherend, and makes it difficult for the adhesive to elute into the electrolytic solution.

In the above invention (Invention 1), it is preferable that the (meth) acrylic acid ester polymer contains a monomer having an alicyclic structure in the molecule as a monomer unit constituting the polymer (Invention 2).

The adhesive composition according to the above inventions (Inventions 1 and 2) preferably contains a metal chelate-based cross-linking agent (Invention 3).

In the above inventions (Inventions 1 to 3), it is preferable that a hard coat layer is formed on the surface of the base material on the pressure-sensitive adhesive layer side (Invention 4). The hard coat layer in the present specification means a layer made of a material harder than the base material, and does not mean a layer existing on the outermost layer of the film.

Secondly, the present invention is characterized in that two or more conductors are fixed in contact with each other inside the battery by using the battery adhesive sheet (Invention 1 to 4). An ion battery is provided (Invention 5).

According to the adhesive composition, the adhesive sheet for batteries, and the lithium ion battery according to the present invention, even when the adhesive sheet for batteries comes into contact with the electrolytic solution, the adhesive layer is suppressed from being coagulated and broken due to swelling. , The adhesive sheet for batteries exerts excellent adhesive strength to the adherend, and the adhesive is difficult to elute into the electrolytic solution.

It is sectional drawing of the adhesive sheet for a battery which concerns on one Embodiment of this invention. It is a partial cross-sectional exploded perspective view of the lithium ion battery which concerns on one Embodiment of this invention. It is a developed perspective view of the electrode body of the lithium ion battery which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive composition]
The adhesive composition according to one embodiment of the present invention is an adhesive composition for forming an adhesive layer of an adhesive sheet for a battery. The "adhesive sheet for a battery" in the present specification is an adhesive sheet used in a place where it may come into contact with an electrolytic solution in the manufacture of a battery, and is preferably an adhesive sheet used inside the battery. It may be an adhesive sheet for battery interior. The battery is preferably a non-aqueous battery. Therefore, the electrolytic solution used for the battery is preferably a non-aqueous electrolytic solution. The adhesive sheet for batteries in the present specification is preferably an adhesive sheet attached to a portion of the non-aqueous battery that may be immersed in the electrolytic solution or a portion that may come into contact with the electrolytic solution. As the non-aqueous battery, a lithium ion battery is particularly preferable.

The adhesive composition according to the present embodiment (hereinafter, may be referred to as “adhesive composition P”) has an alkyl group having 6 or more carbon atoms and 20 or less carbon atoms as a monomer unit constituting the polymer (hereinafter, may be referred to as “adhesive composition P”). A metal chelate-based cross-linking agent (B) containing a (meth) acrylic acid alkyl ester and a (meth) acrylic acid ester polymer (A) containing a monomer having a carboxy group in the molecule (carboxy group-containing monomer), preferably further. Is contained, and particularly preferably, a silane coupling agent (C) is further contained. In addition, in this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. In addition, the concept of "polymer" shall be included in "polymer".

(1) Each component (1-1) (meth) acrylic acid ester polymer (A)
The (meth) acrylic acid ester polymer (A) has a (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms as an alkyl group as a monomer unit constituting the polymer, and a carboxy group in the molecule. Contains a monomer (carboxy group-containing monomer).

The (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms of the alkyl group imparts good adhesiveness to the obtained pressure-sensitive adhesive and exhibits hydrophobicity due to the large number of carbon atoms of the alkyl group. This hydrophobicity has a property of having a low affinity for an electrolytic solution (including a non-aqueous electrolytic solution). Therefore, the obtained pressure-sensitive adhesive exhibits good adhesive strength and also has excellent electrolytic solution resistance due to the above-mentioned hydrophobicity. Therefore, when the pressure-sensitive adhesive layer of the battery pressure-sensitive adhesive sheet is formed by the pressure-sensitive adhesive composition P containing the (meth) acrylic acid ester polymer (A), when the battery pressure-sensitive adhesive sheet comes into contact with the electrolytic solution (immersed). Even in the case of), the pressure-sensitive adhesive layer is suppressed from being coagulated and broken due to swelling, and the battery pressure-sensitive adhesive sheet exhibits excellent adhesive strength to the adherend. Further, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is difficult to elute into the electrolytic solution, and the pressure-sensitive adhesive does not adversely affect the battery performance. As a result, malfunction, thermal runaway and short circuit of the battery caused by the adhesive sheet for the battery are suppressed.

The alkyl group of the (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms of the alkyl group may be linear or branched. From the viewpoint of hydrophobicity, the alkyl group needs to have 6 or more carbon atoms, preferably 7 or more, and particularly preferably 8 or more. On the other hand, the number of carbon atoms of the alkyl group needs to be 20 or less from the viewpoint of adhesiveness, preferably 18 or less, particularly preferably 15 or less, and further 10 or less. Is preferable.

Examples of the (meth) acrylic acid alkyl ester having an alkyl group having 6 to 20 carbon atoms include (meth) acrylic acid n-hexyl, (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid isooctyl, and (meth) acrylic acid. ) N-decyl acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate and the like. Among the above (meth) acrylic acid alkyl esters, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl acrylate and the like from the viewpoint of adhesiveness and hydrophobicity. Is preferable, and 2-ethylhexyl acrylate and isooctyl acrylate are particularly preferable. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) may contain 50% by mass or more of the (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms of the alkyl group as the monomer unit constituting the polymer. It is preferably contained in an amount of 60% by mass or more, particularly preferably 70% by mass or more, and further preferably 75% by mass or more. When the (meth) acrylic acid alkyl ester is contained in an amount of 50% by mass or more, the (meth) acrylic acid ester polymer (A) can exhibit more excellent adhesiveness and electrolytic solution resistance. Further, the (meth) acrylic acid ester polymer (A) contains 99% by mass or less of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. It is more preferable to contain 97% by mass or less, particularly 90% by mass or less, and further preferably 85% by mass or less. By adjusting the amount of the (meth) acrylic acid alkyl ester to 99% by mass or less, a suitable amount of other monomer components can be introduced into the (meth) acrylic acid ester polymer (A).

On the other hand, the carboxy group-containing monomer contained in the (meth) acrylic acid ester polymer (A) as a monomer unit constituting the polymer has an effect of improving the adhesive strength of the obtained pressure-sensitive adhesive. When the adhesive composition P contains the metal chelate-based cross-linking agent (B) described later, the carboxy group derived from the carboxy group-containing monomer is a metal chelate when the (meth) acrylic acid ester polymer (A) is cross-linked. It reacts with the system cross-linking agent (B), thereby forming a cross-linked structure which is a three-dimensional network structure. The pressure-sensitive adhesive having a crosslinked structure by the reaction of the carboxy group and the metal chelate-based crosslinking agent (B) has high resistance to an electrolytic solution, particularly a non-aqueous electrolytic solution, and is difficult to elute even if it comes into contact with the electrolytic solution. Therefore, in combination with the electrolytic solution resistance of the (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms of the alkyl group, the obtained pressure-sensitive adhesive is difficult to elute by the electrolytic solution.

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. Of these, acrylic acid is preferable. According to acrylic acid, the above effect is more excellent. The above-mentioned carboxy group-containing monomers may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains a carboxy group-containing monomer as a lower limit value of 0.5% by mass or more, particularly 1% by mass or more, as a monomer unit constituting the polymer. It is preferable that the content is 3% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains a carboxy group-containing monomer as an upper limit value of 30% by mass or less, and particularly 20% by mass or less, as a monomer unit constituting the polymer. It is preferable that the content is 10% by mass or less. When the (meth) acrylic acid ester polymer (A) contains the carboxy group-containing monomer in the above amount as the monomer unit, the above effect becomes more excellent in the obtained pressure-sensitive adhesive.

Further, the (meth) acrylic acid ester polymer (A) preferably contains a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer) as a monomer unit constituting the polymer. This alicyclic structure-containing monomer exhibits hydrophobicity due to its bulkiness. Therefore, the obtained pressure-sensitive adhesive is more excellent in electrolytic solution resistance in combination with the hydrophobicity of the (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms in the alkyl group. Therefore, even when the battery adhesive sheet comes into contact with the electrolytic solution, the adhesive layer is more effectively suppressed from coagulating and breaking due to swelling, and the battery adhesive sheet is more excellent with respect to the adherend. Demonstrates adhesive strength. Further, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is difficult to be eluted by the electrolytic solution.

The alicyclic structure carbon ring in the alicyclic structure-containing monomer may have a saturated structure or may have an unsaturated bond as a part. Further, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as two rings or three rings. From the viewpoint of the above-mentioned hydrophobicity and the resistance to the electrolytic solution, the alicyclic structure is preferably a polycyclic alicyclic structure (polycyclic structure). Further, in consideration of the compatibility between the (meth) acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic to tetracyclic. In addition, from the viewpoint of effectively exerting electrolyte resistance, the number of carbon atoms in the alicyclic structure (referring to the total number of carbon atoms in the portion forming the ring, and when a plurality of rings exist independently) , The total number of carbon atoms) is usually preferably 5 or more, and particularly preferably 7 or more. On the other hand, the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, but from the viewpoint of compatibility as described above, it is preferably 15 or less, and particularly preferably 10 or less.

Examples of the alicyclic structure include a cyclohexyl skeleton, a dicyclopentadiene skeleton, an adamantan skeleton, an isobornyl skeleton, and a cycloalkane skeleton (cycloheptane skeleton, cyclooctane skeleton, cyclononan skeleton, cyclodecane skeleton, cycloundecane skeleton, cyclododecane skeleton, etc.). , Cycloalkane skeleton (cycloheptene skeleton, cyclooctene skeleton, etc.), norbornen skeleton, norbornadien skeleton, Cuban skeleton, Basquetan skeleton, Hausan skeleton, Spiro skeleton, etc. Those containing a dicyclopentadiene skeleton (carbon number of alicyclic structure: 10), adamantan skeleton (carbon number of alicyclic structure: 10) or isobornyl skeleton (carbon number of alicyclic structure: 7) are preferable, and particularly Those containing an isobornyl skeleton are preferable.

As the alicyclic structure-containing monomer, a (meth) acrylic acid ester monomer containing the above skeleton is preferable, and specifically, cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, (meth). Examples include adamantyl acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, etc. Among them, (meth) acrylic, which exhibits more excellent durability. Dicyclopentanyl acid, adamantyl (meth) acrylate or isobornyl (meth) acrylate are preferred, and isobornyl (meth) acrylate is particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type.

When the (meth) acrylic acid ester polymer (A) contains an alicyclic structure-containing monomer as a monomer unit constituting the polymer, the (meth) acrylic acid ester polymer (A) becomes more hydrophobic. From the viewpoint of enhancing, the alicyclic structure-containing monomer is preferably contained in an amount of 5% by mass or more, particularly preferably 7.5% by mass or more, and further preferably 10% by mass or more. Further, the (meth) acrylic acid ester polymer (A) is from the viewpoint of preventing the electrolytic solution resistance from being lowered due to insufficient amount of the (meth) acrylic acid ester polymer having 6 to 20 carbon atoms in the alkyl group. Therefore, the monomer unit constituting the polymer preferably contains 35% by mass or less of the alicyclic structure-containing monomer, particularly preferably 30% by mass or less, and further preferably 20% by mass or less. preferable. When the content of the alicyclic structure-containing monomer is in the above range, the above-mentioned electrolytic solution resistance becomes more excellent.

If desired, the (meth) acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer. The other monomer may be a monomer containing a reactive functional group (excluding a carboxy group) or a monomer containing no reactive functional group.

Examples of the monomer containing a reactive functional group include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), and the like.

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). ) Acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. These may be used alone or in combination of two or more.

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

The monomer containing a reactive functional group is limited to the above-mentioned carboxy group-containing monomer so as not to inhibit the effect obtained by the cross-linking structure obtained by the reaction of the carboxy group and the metal chelate-based cross-linking agent (B). Is preferable.

On the other hand, examples of the reactive functional group-free monomer include carbons of alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. (Meta) acrylic acid alkoxyalkyl esters such as (meth) acrylic acid alkyl esters, (meth) acrylic acid methoxyethyl, (meth) acrylic acid ethoxyethyl, and (meth) acrylic acid N, N- (Meta) acrylic acid ester having a non-crosslinkable tertiary amino group such as dimethylaminoethyl, N, N-dimethylaminopropyl (meth) acrylate, (meth) acryloylmorpholin, (meth) acrylamide, dimethylacrylamide, acetic acid Examples include vinyl and styrene. These may be used alone or in combination of two or more.

The polymerization mode of the (meth) acrylic acid ester 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, more preferably 100,000 or more, particularly preferably 200,000 or more, and further preferably 200,000 or more. 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 at least the above value, the elution resistance of the obtained pressure-sensitive adhesive to the electrolytic solution becomes more excellent.

The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2.5 million or less, more preferably 2 million or less, and particularly preferably 1.5 million or less, as an upper limit value. Further, it is preferably 1.2 million or less. When the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is not more than the above, the adhesive strength of the obtained pressure-sensitive adhesive becomes more excellent. The weight average molecular weight in the present specification is a standard polystyrene-equivalent value measured by a gel permeation chromatography (GPC) method.

The glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) is preferably less than 20 ° C., particularly preferably less than 0 ° C., and further less than −40 ° C. as an upper limit value. It is preferable to have. When the upper limit of the glass transition temperature of the (meth) acrylic acid ester polymer (A) is as described above, the tack of the pressure-sensitive adhesive at room temperature is high, and it is difficult to peel off when immersed in the electrolytic solution. On the other hand, the lower limit of the glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) is not particularly limited, but is usually −70 ° C. or higher from the viewpoint of improving the durability in the electrolytic solution. The temperature is preferably −62.5 ° C. or higher, and more preferably −55 ° C. or higher. Here, the glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) is the glass transition temperature (Tg) as a homopolymer of each monomer constituting the (meth) acrylic acid ester polymer (A). Based on the above, it is assumed that the calculation is performed by the FOX formula.

In the adhesive composition P, the (meth) acrylic acid ester polymer (A) may be used alone or in combination of two or more.

(1-2) Metal chelate cross-linking agent (B)
The adhesive composition P preferably contains a metal chelate-based cross-linking agent (B). When the adhesive composition P contains the metal chelate-based cross-linking agent (B), a pressure-sensitive adhesive in which the (meth) acrylic acid ester polymer (A) is cross-linked by the metal chelate-based cross-linking agent (B) is obtained. The pressure-sensitive adhesive having this crosslinked structure has high resistance to an electrolytic solution, particularly a non-aqueous electrolytic solution, and is electrolyzed in combination with the electrolytic solution resistance of the (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms of the alkyl group. It becomes difficult to elute depending on the liquid.

As the metal chelate-based cross-linking agent (B), a metal chelate compound having a metal atom of aluminum, zirconium, titanium, zinc, iron, tin or the like can be used. Of these, aluminum chelate compounds are particularly preferable. The aluminum chelate compound exhibits the above-mentioned elution resistance to the electrolytic solution particularly effectively.

Examples of the aluminum chelate compound include diisopropoxyaluminum monooleylacetate, monoisopropoxyaluminum bisoleylacetate, monoisopropoxyaluminum monooleate monoethylacetate, diisopropoxyaluminum monolaurylacetate, and diisopropoxy. Aluminum monostearyl acetoacetate, diisopropoxyaluminum monoisostearyl acetoacetate, monoisopropoxyaluminum mono-N-lauroyl-β-alanate monolauryl acetoacetate, aluminum tris (acetylacetate), monoacetylacetonate aluminum bis ( Isobutylacetate) chelate, monoacetylacetonate aluminum bis (2-ethylhexylacetate) chelate, monoacetylacetonate aluminum bis (dodecylacetacetate) chelate, monoacetylacetonate aluminum bis (oleylacetacetate) chelate and the like. .. Among these, aluminum tris (acetylacetonate) is preferable from the viewpoint of the above effects. These may be used alone or in combination of two or more.

Examples of other metal chelate compounds include titanium tetrapropionate, titanium tetra-n-butyrate, titanium tetra-2-ethylhexanoate, zirconium sec-butyrate, zirconium diethoxy-tert-butyrate, and triethanol. Examples thereof include amine titanium dipropionate, an ammonium salt of titanium lactate, and tetraoctylene glycol titanate. These may be used alone or in combination of two or more.

The above-mentioned metal chelate-based cross-linking agent (B) may be used alone or in combination of two or more.

The content of the metal chelate-based cross-linking agent (B) in the pressure-sensitive adhesive composition P according to the present embodiment is 0.1 mass by mass as a lower limit with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferably parts or more, more preferably 0.3 parts by mass or more, particularly preferably 0.5 parts by mass or more, and further preferably 1.2 parts by mass or more. The content of the metal chelate-based cross-linking agent (B) is preferably 5 parts by mass or less, particularly preferably 4 parts by mass or less, and further preferably 3 parts by mass or less as an upper limit value. .. When the content of the metal chelate-based cross-linking agent (B) is in the above range, the above-mentioned effect becomes more excellent.

(1-3) Silane coupling agent (C)
The adhesive composition P preferably further contains a silane coupling agent (C). When the adhesive composition P contains the silane coupling agent (C), even when the adhesive sheet for the battery comes into contact with the electrolytic solution (including the case where it is immersed), it is applied to the adherend (particularly the metal member). Exhibits excellent adhesiveness. As a result, the (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms in the alkyl group constituting the (meth) acrylic acid ester polymer (A) exerts a superposed effect on the adhesiveness and the electrolyte resistance. Therefore, the adhesive strength is further improved, and the peeling of the battery adhesive sheet from the adherend is effectively suppressed. As a result, the deterioration of the battery performance caused by the adhesive sheet for the battery is suppressed. Further, even when the hard coat layer is formed on the surface of the pressure-sensitive adhesive sheet for a battery on the side of the pressure-sensitive adhesive layer of the base material, the pressure-sensitive adhesive layer has high adhesion to the hard coat layer. Therefore, it is possible to prevent peeling or the like from occurring at the interface between the hard coat layer and the pressure-sensitive adhesive layer due to immersion of the battery adhesive sheet in the electrolytic solution, and to improve the adhesive strength after immersion in the electrolytic solution solvent. .. Further, when the release sheet is peeled from the pressure-sensitive adhesive layer, it is possible to prevent the pressure-sensitive adhesive layer from being transferred to the release sheet and peeling from the hard coat layer.

The silane coupling agent (C) is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule and having good compatibility with the (meth) acrylic acid ester polymer (A).

Examples of the silane coupling agent (C) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and the like. Silicon compounds having an epoxy structure such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, mercapto groups such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane Contains amino groups such as silicon compound, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Contains silicon compound, 3-chloropropyltrimethoxysilane, 3-isocyanuspropyltriethoxysilane, or at least one of them and an alkyl group such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, etc. Examples thereof include a condensate with a silicon compound. Among these, a silicon compound having an epoxy structure is preferable from the viewpoint of the above effects, and 3-glycidoxypropyltrimethoxysilane is particularly preferable. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the silane coupling agent (C) in the adhesive composition P is preferably 0.01 part by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), and is 0. It is more preferably 0.05 parts by mass or more, particularly preferably 0.1 parts by mass or more, and further preferably 0.4 parts by mass or more. The content is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, particularly preferably 3 parts by mass or less, and further preferably 1.5 parts by mass or less. Is preferable. When the content of the silane coupling agent (C) is in the above range, the adhesive strength after immersion in the electrolytic solution solvent becomes more excellent.

(1-4) Various Additives Various additives usually used for acrylic pressure-sensitive adhesives, such as tackifiers, antioxidants, softeners, and fillers, are added to the pressure-sensitive adhesive composition P, if desired. can do. The polymerization solvent and the diluting solvent described later are not included in the additives constituting the adhesive composition P.

(2) Production of Adhesive Composition The adhesive composition P produces a (meth) acrylic acid ester polymer (A), and the obtained (meth) acrylic acid ester polymer (A) is optionally added to the obtained (meth) acrylic acid ester polymer (A). It can be produced by adding a metal chelate-based cross-linking agent (B), a silane coupling agent (C), an additive and the like.

The (meth) acrylic acid ester 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) acrylic acid ester polymer (A) can be carried out by a solution polymerization method or the like using a polymerization initiator, if desired. 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 of them 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 (cyclohexane1-carbonitrile), and 2 , 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-butylperbenzoate, cumenehydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butylperoxyneodecanoate, t-butylperoxyvivarate, (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.

Once the (meth) acrylic acid ester polymer (A) is obtained, a metal chelate-based cross-linking agent (B), a silane coupling agent (C), and the like, if desired, are added to the solution of the (meth) acrylic acid ester polymer (A). An adhesive composition P is obtained by adding an additive or the like and mixing the mixture sufficiently.

The adhesive composition P is appropriately diluted with a diluting solvent or the like in addition to the above-mentioned polymerization solvent in order to adjust the viscosity to an appropriate level for coating and to adjust the pressure-sensitive adhesive layer to a desired film thickness. It may be used as 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.

[Adhesive sheet for batteries]
The pressure-sensitive adhesive sheet for a battery according to an embodiment of the present invention includes a base material and a pressure-sensitive adhesive layer laminated on one surface side of the base material, and the pressure-sensitive adhesive layer is derived from the above-mentioned pressure-sensitive adhesive composition P. It is formed. Hereinafter, the battery adhesive sheet according to the preferred embodiment will be described.

As shown in FIG. 1, the battery adhesive sheet 1 according to the present embodiment includes a base material 11, a hard coat layer 12 provided on one surface side of the base material 11, and a base material 11 in the hard coat layer 12. It is composed of a pressure-sensitive adhesive layer 13 provided on the opposite side of the pressure-sensitive adhesive layer 13 and a release sheet 14 provided on the side opposite to the hard coat layer 12 in the pressure-sensitive adhesive layer 13. The pressure-sensitive adhesive layer 13 is formed from the above-mentioned pressure-sensitive adhesive composition P. In the present invention, the hard coat layer 12 and the release sheet 14 are not essential components and may be omitted respectively.

The battery pressure-sensitive adhesive sheet 1 having the pressure-sensitive adhesive layer 13 formed from the pressure-sensitive adhesive composition P described above is a (meth) acrylic acid ester polymer even when it comes into contact with an electrolytic solution (including when it is immersed). Due to the good adhesiveness and electrolytic solution resistance of the (meth) acrylic acid alkyl ester having 6 to 20 carbon atoms in the alkyl group constituting (A), the pressure-sensitive adhesive layer 13 is suppressed from being coagulated and broken by swelling. , The battery adhesive sheet 1 exhibits excellent adhesive strength to the adherend. Further, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 13 is difficult to elute into the electrolytic solution, and the pressure-sensitive adhesive does not adversely affect the battery performance. As a result, malfunction, thermal runaway, and short circuit of the battery caused by the adhesive sheet 1 for the battery are suppressed.

Further, the adhesive sheet 1 for a battery according to the present embodiment is provided with the hard coat layer 12, so that the insulating property can be ensured even when the base material 11 and the adhesive layer 13 are carbonized, and the battery can be secured. The safety of the battery can be improved.

1. 1. Base material In the battery adhesive sheet 1 according to the present embodiment, the base material 11 preferably has a flame retardancy that satisfies the flame retardancy level V-0 of the UL94 standard. Since the base material 11 has such flame retardancy, denaturation and deformation of the base material 11 are suppressed even when heat is generated by using a normal battery. Further, even if a problem occurs in the battery and excessive heat generation occurs, 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 flame retardancy, heat resistance, insulating property, reactivity with the electrolytic solution, permeability of the electrolytic solution, and the like. In particular, it is preferable to use a resin film as the base material 11. Examples of the resin film include polyester films such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyolefin films such as polyethylene film and polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film and poly. Vinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulphon film, polyether ether ketone film, polyether sulfone film, polyether Iimide film, fluororesin film, polyamide film, polyimide film, polyamideimide film, acrylic resin film, polyurethane resin film, norbornene-based polymer film, cyclic olefin-based polymer film, cyclic conjugated diene-based polymer film, vinyl alicyclic type Examples thereof include a resin film such as a hydrocarbon polymer film or a laminated film thereof. In particular, from the viewpoint of exhibiting excellent flame retardancy and heat resistance, a polymer film containing nitrogen in the main chain (may contain components other than the polymer; the same applies herein) is preferable. In particular, a polymer film having a nitrogen-containing ring structure in the main chain is preferable, and a polymer film having a nitrogen-containing ring structure and an aromatic ring structure in the main chain is further preferable. Specifically, for example, a polyimide film, a polyetherimide film or a polyetheretherketone film is preferable, and among these, a polyimide film showing higher heat resistance is preferable.

The thickness of the base material 11 is preferably 5 to 200 μm, particularly preferably 10 to 100 μm, and further preferably 15 to 40 μm. When the thickness of the base material 11 is 5 μm or more, appropriate rigidity is imparted to the base material 11, and even when curing shrinkage occurs when the hard coat layer 12 is formed on the base material 11, the curl Occurrence is effectively suppressed. Further, since the thickness of the base material 11 is 200 μm or less, the adhesive sheet 1 for a battery has appropriate flexibility, and is provided on a surface having a step as in the case of fixing an electrode and an electrode take-out tab. Even when the battery adhesive sheet 1 is attached, it can follow the step well.

2. Hard coat layer (1) Physical characteristics of the hard coat layer In the battery adhesive sheet 1 according to the present embodiment, the hard coat layer 12 in the state of being provided on the base material 11 is 250 g / cm using # 0000 steel wool. It is preferable that the hard coat layer 12 is rubbed 10 cm 10 times with a load of ^{2 so that no scratches are generated.} Having such an evaluation of steel wool resistance effectively blocks the permeation of the electrolytic solution through the hard coat layer 12, and effectively suppresses the escape of the inorganic filler due to the swelling of the hard coat layer 12.

(2) Composition of Hard Coat Layer The hard coat layer 12 is preferably formed from a composition containing an organic component and an inorganic filler (hereinafter, may be referred to as a “composition for a hard coat layer”). In particular, the hard coat layer 12 is preferably made of a material obtained by curing a composition containing an active energy ray-curable component and an inorganic filler.

(2-1) Active energy ray-curable component The active energy ray-curable component is not particularly limited as long as it is cured by irradiation with active energy rays and exhibits a desired hardness.

Specific examples of the active energy ray-curable component include a polyfunctional (meth) acrylate-based monomer, a (meth) acrylate-based prepolymer, an active energy ray-curable polymer, and the like. Among them, the polyfunctional (meth) acrylate. It is preferably a based monomer and / or a (meth) acrylate-based prepolymer. The polyfunctional (meth) acrylate-based monomer and the (meth) acrylate-based prepolymer may be used alone or in combination of both. In addition, in this specification, (meth) acrylate means both acrylate and methacrylate. The same applies to other similar terms.

Examples of the polyfunctional (meth) acrylate-based monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol di. (Meta) acrylate, neopentyl glycol di (meth) acrylate of hydroxypivalate, dicyclopentanyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified di (meth) acrylate of phosphate, allylated Cyclohexyldi (meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropantri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate ) Acrylate, propylene oxide-modified trimethylolpropantri (meth) acrylate, tris (acryloxyethyl) isocyanurate, propionic acid-modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol Examples thereof include polyfunctional (meth) acrylates such as hexa (meth) acrylates. These may be used individually by 1 type, and may be used in combination of 2 or more type. The polyfunctional (meth) acrylate-based monomer is not particularly limited, but is more preferably one having a molecular weight of less than 1000 from the viewpoint of preventing the inorganic filler from coming out from the hard coat layer 12 under immersion in the electrolytic solution.

On the other hand, examples of the (meth) acrylate-based prepolymer include polyester acrylate-based, epoxy acrylate-based, urethane acrylate-based, and polyol acrylate-based prepolymers. One type of prepolymer may be used alone, or two or more types may be used in combination.

The active energy ray-curable component constituting the hard coat layer 12 of the present embodiment preferably has a glass transition point of 130 ° C. or higher after curing, more preferably 150 ° C. or higher, and the glass transition point is observed. It is particularly preferable that it is not used. Since the glass transition point of the active energy ray-curable component is as described above, the heat resistance of the hard coat layer 12 becomes excellent, and the battery adhesive sheet 1 provided with such a hard coat layer 12 is included. The performance and safety of the battery will also be excellent.

When two or more types of active energy ray-curable components are used in the hard coat layer 12 of the present embodiment, it is preferable that the active energy ray-curable components have excellent compatibility with each other.

(2-2) Inorganic Filler The composition for the hard coat layer constituting the hard coat layer 12 of the present embodiment preferably contains an inorganic filler. By containing the inorganic filler, the hard coat layer 12 of the present embodiment is imparted with rigidity, and the battery adhesive sheet 1 is torn or punctured due to an impact at a high temperature or under immersion in an electrolytic solution. Can be prevented.

Preferred inorganic fillers include powders of silica, alumina, boehmite, talc, calcium carbonate, titanium oxide, iron oxide, silicon carbide, boron nitride, zirconium oxide and the like, spherical beads, single crystal fibers and glass fibers. These can be used alone or in admixture of two or more. Among these, silica, alumina, boehmite, titanium oxide, zirconium oxide and the like are preferable, and silica, alumina and zirconium oxide are preferable from the viewpoint of dispersibility in the active energy ray-curable component. In addition, these inorganic fillers can also be used in the form of a sol dispersed in a dispersion medium.

It is also preferable that the inorganic filler is surface-modified. Reactive silica can be exemplified as such an inorganic filler.

As used herein, the term "reactive silica" refers to silica fine particles surface-modified with an organic compound having an active energy ray-curable unsaturated group. The silica fine particles (reactive silica) surface-modified with an organic compound having an active energy ray-curable unsaturated group are usually, for example, a silanol group on the surface of silica fine particles having an average particle size of 1 to 200 nm, and the silanol group. It can be obtained by reacting an active energy ray-curable unsaturated group-containing organic compound having a reactive functional group (for example, an isocyanate group, an epoxy group, a carboxy group, etc.). As the active energy ray-curable unsaturated group, a (meth) acryloyl group or a vinyl group can be preferably mentioned.

As an organic-inorganic hybrid material (organosilica sol) containing such a reactive silica and the above-mentioned polyfunctional (meth) acrylate-based monomer and / or (meth) acrylate-based prepolymer, for example, the trade name "Opstar Z7530". , "Opstar Z7524", "Opstar TU4086", "Opstar Z7537" (all manufactured by JSR Corporation) and the like can be used.

Other examples of preferred inorganic fillers include alumina ceramic nanoparticles, silica sol in which silica fine particles with exposed silanol groups on the silica surface are suspended in a colloidal state in a dispersion medium, and silanol groups on the silica surface are silane coupling. Examples thereof include organosilica sol surface-treated with an agent or the like.

The inorganic filler used in the present embodiment preferably has an average particle size of 1 to 1000 nm, particularly preferably 10 to 500 nm, and even more preferably 15 to 200 nm. When the average particle size of the inorganic filler is 1 nm or more, the hard coat layer 12 obtained by curing the composition for the hard coat layer has higher rigidity. Further, since the average particle size of the inorganic filler is 1000 nm or less, the dispersibility of the inorganic filler in the composition for the hard coat layer becomes excellent, and when the hard coat layer 12 is formed on the base material 11, the hard coat layer 12 is formed. It is possible to effectively prevent the occurrence of unevenness on the surface of the hard coat layer 12 opposite to the base material 11. Further, by forming the pressure-sensitive adhesive layer 13 on the surface, it is possible to obtain extremely high smoothness on the surface of the pressure-sensitive adhesive layer 13 opposite to the hard coat layer 12. As a result, the pressure-sensitive adhesive layer 13 can exhibit excellent adhesion to the adherend. The average particle size of the inorganic filler is measured by a laser diffraction / scattering type particle size distribution measuring device.

The content of the inorganic filler in the hard coat layer 12 of the present embodiment is preferably 0 to 90% by mass (90% by mass or less), more preferably 30 to 85% by mass, based on the hard coat layer 12. It is preferably 40 to 80% by mass, more preferably 45 to 70% by mass. When the inorganic filler is contained, the rigidity imparted to the hard coat layer 12 becomes higher when the content is 30% by mass or more. On the other hand, when the content of the inorganic filler is 90% by mass or less, layer formation using the composition for the hard coat layer becomes easy.

(2-3) Other Components The composition for forming the hard coat layer 12 of the present embodiment may contain various additives in addition to the above-mentioned components. Examples of various additives include photopolymerization initiators, antioxidants, antistatic agents, silane coupling agents, antioxidants, thermal polymerization inhibitors, colorants, surfactants, storage stabilizers, plasticizers, and lubricants. , Antifoaming agents, organic fillers and the like.

When the hard coat layer 12 is formed by using ultraviolet rays as active energy rays, it is preferable to use a photopolymerization initiator. The photopolymerization initiator is not particularly limited as long as it functions as a photopolymerization initiator of the active energy ray-curable component used, and for example, an acylphosphine oxide compound, a benzoin compound, an acetophenone compound, a titanosen compound, and a thioxanthone. Examples include compounds and peroxide compounds. Specifically, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, benzoin, benzoin Examples thereof include methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfate, tetramethylthium monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloranthraquinone and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the photopolymerization initiator in the composition for a hard coat layer is usually preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the active energy ray-curable component, and particularly 1 to 20 parts by mass. It is preferably 15 parts by mass.

(3) Thickness of Hard Coat Layer The thickness of the hard coat layer 12 is preferably 0.1 to 10 μm, particularly preferably 0.5 to 7 μm, and further preferably 1 to 4 μm. preferable. When the thickness of the hard coat layer 12 is 0.1 μm or more, the permeation of the hard coat layer 12 by the electrolytic solution is effectively blocked. Further, since the thickness of the hard coat layer 12 is 10 μm or less, the adhesive sheet 1 for a battery has appropriate flexibility, and a surface having a step as in the case of fixing an electrode and an electrode take-out tab. Even when the battery adhesive sheet 1 is attached to the battery adhesive sheet 1, the battery adhesive sheet 1 can follow the step well.

3. 3. Adhesive layer The adhesive layer 13 is formed from the adhesive composition P described above. The method for forming the pressure-sensitive adhesive layer 13 will be described later.

(1) Physical Properties of Adhesive / Adhesive Layer In the battery adhesive sheet 1 according to the present embodiment, the adhesive constituting the adhesive layer 13 is immersed in a solvent of a non-aqueous electrolyte solution at 80 ° C. for 72 hours and then adhered. The gel fraction of the agent is preferably 70% or more, particularly preferably 80% or more, and further preferably 90% or more as the lower limit value. When the lower limit of the gel fraction is the above, the elution amount of the pressure-sensitive adhesive when the pressure-sensitive adhesive layer 13 comes into contact with the electrolytic solution can be suppressed to a low level. Thereby, malfunction, thermal runaway and short circuit of the battery using the battery adhesive sheet 1 are more effectively suppressed.

On the other hand, the upper limit of the gel fraction is preferably 100% or less, particularly preferably 99% or less, and further preferably 98% or less. When the upper limit of the gel fraction is 98% or less, the adhesive sheet 1 for a battery has appropriate flexibility, and is used for a battery on a surface having a step, as in the case of fixing an electrode and an electrode extraction tab. Even when the adhesive sheet 1 is attached, it is possible to follow the step well.

The solvent of the non-aqueous electrolyte solution here is a prepared solution obtained by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1. The method for testing the gel fraction is as shown in a test example described later. ..

(2) Thickness of Adhesive Layer The thickness of the adhesive layer 13 (value measured according to JIS K7130) is preferably 1 to 50 μm, particularly preferably 3 to 15 μm, and further 4 It is preferably ~ 9 μm. When the thickness of the pressure-sensitive adhesive layer 13 is 1 μm or more, the pressure-sensitive adhesive sheet 1 for a battery can exhibit more excellent adhesive strength. Further, when the thickness of the pressure-sensitive adhesive layer 13 is 50 μm or less, the amount of the electrolytic solution that infiltrates from the end portion of the pressure-sensitive adhesive layer 13 can be effectively reduced.

4. Peeling Sheet The peeling sheet 14 protects the adhesive layer until the battery adhesive sheet 1 is used, and is peeled off when the battery 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 polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, and 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 , Liquid crystal polymer film and the like are used. In addition, these crosslinked films are also used. Further, these laminated films may be used.

It is preferable that the peeling surface (the surface in contact with the pressure-sensitive adhesive layer 13) of the peeling sheet 14 is subjected to a peeling 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.

5. Physical Properties of Adhesive Sheet for Batteries, etc. The adhesive force (adhesive force before immersion in the electrolyte solvent) of the adhesive sheet 1 for batteries according to the present embodiment is preferably 0.5 N / 25 mm or more as a lower limit value. It is more preferably 0.75 N / 25 mm or more, particularly preferably 1.0 N / 25 mm or more, and further preferably 2.0 N / 25 mm or more. Since the lower limit of the adhesive strength of the battery adhesive sheet 1 before immersion in the electrolytic solution solvent is as described above, the battery adhesive sheet 1 is attached to an adherend (particularly metal) before the battery adhesive sheet 1 comes into contact with the electrolytic solution. It is unlikely that the problem of peeling from the member) will occur. The upper limit of the adhesive strength before immersion in the electrolytic solution solvent is not particularly limited, but is usually preferably 50 N / 25 mm or less, more preferably 40 N / 25 mm or less, and particularly preferably 30 N / 25 mm or less. It is preferable, and more preferably 10 N / 25 mm or less. The adhesive strength in the present specification basically refers to the adhesive strength measured by the 180 ° peeling method according to JIS Z0237: 2009, and the detailed measurement method is as shown in the test example described later.

Further, after the battery adhesive sheet 1 according to the present embodiment is attached to an aluminum plate and immersed in a solvent of a non-aqueous electrolytic solution at 80 ° C. for 72 hours, the adhesive strength (electrolysis) of the battery adhesive sheet 1 to the aluminum plate. The lower limit of the adhesive strength after immersion in the liquid solvent is preferably 0.5 N / 25 mm or more, more preferably 0.75 N / 25 mm or more, and particularly preferably 1.0 N / 25 mm or more. Furthermore, it is preferably 2.0 N / 25 mm or more. Since the lower limit of the adhesive strength of the battery adhesive sheet 1 after being immersed in the electrolytic solution solvent is as described above, the battery adhesive sheet 1 can be used even after the battery adhesive sheet 1 is in contact with (immersed) in the electrolytic solution. The problem of peeling from the adherend (especially metal member) is unlikely to occur. The upper limit of the adhesive strength after immersion in the electrolytic solution solvent is not particularly limited, but is usually preferably 40 N / 25 mm or less, more preferably 30 N / 25 mm or less, and particularly 20 N / 25 mm or less. It is preferable, and more preferably 10 N / 25 mm or less. The battery pressure-sensitive adhesive sheet 1 according to the present embodiment contains the above-mentioned (meth) acrylic acid ester polymer (A), preferably a metal chelate-based cross-linking agent (B), and particularly preferably a silane coupling agent (C). By having the pressure-sensitive adhesive layer 13 formed by using the pressure-sensitive adhesive composition P contained therein, excellent adhesive strength in the above range can be achieved. The solvent of the non-aqueous electrolytic solution here is a prepared solution obtained by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1.

The adhesive strength after immersion in the electrolytic solution solvent is preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more, based on the adhesive strength before immersion in the electrolytic solution solvent. Further, it is preferably 100% or more.

The thickness of the battery adhesive sheet 1 (excluding the thickness of the release sheet 14) is preferably 10 to 250 μm, particularly preferably 15 to 110 μm, and further preferably 20 to 45 μm. When the thickness of the battery adhesive sheet 1 is within the above range, the battery adhesive sheet 1 becomes more suitable because it has both adhesive strength and heat resistance.

6. Method for Manufacturing Adhesive Sheet for Battery The adhesive sheet 1 for a battery according to the present embodiment is, for example, a laminate of a base material 11 and a hard coat layer 12, and a laminate of a coating film of the adhesive composition P and a release sheet 14. Each body is prepared, and these laminates are laminated so that the hard coat layer 12 and the coating film of the adhesive composition P are in contact with each other, and then cured, and the pressure-sensitive adhesive layer is applied from the coating film of the adhesive composition P. It can be manufactured by forming 13. From the viewpoint of improving the adhesion between the hard coat layer 12 and the pressure-sensitive adhesive layer 13, corona treatment, plasma treatment, etc. are performed on the surface to which any one of these layers is bonded or the surface to which both layers are bonded. It is also preferable to bond the two layers after performing the surface treatment of.

The laminate of the base material 11 and the hard coat layer 12 can be produced, for example, as follows. First, a coating liquid containing a composition for a hard coat layer and, if desired, a solvent is applied to one main surface of the base material 11 and dried. The coating liquid may be applied by a conventional method, for example, by a bar coating method, a knife coating method, a Meyer bar method, a roll coating method, a blade coating method, a die coating method, or a gravure coating method. Drying can be performed, for example, by heating at 80 to 150 ° C. for about 30 seconds to 5 minutes.

Then, the layer obtained by drying the coating liquid is irradiated with active energy rays to cure the layer and form the hard coat layer 12. As the active energy ray, for example, an electromagnetic wave or a charged particle beam having an energy quantum can be used, and specifically, an ultraviolet ray, an electron beam, or the like can be used. In particular, ultraviolet rays that are easy to handle are preferable. The irradiation of ultraviolet rays can be performed by a high-pressure mercury lamp, a xenon lamp, or the like, and the irradiation amount of ultraviolet rays is preferably about ^{50 to 1000 mW / cm 2.} Further, the light quantity is preferably 50~10000mJ / cm ^2, more preferably 80~5000mJ / cm ^2, and particularly preferably 200~2000mJ / cm ^2. On the other hand, the irradiation of the electron beam can be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 grad.

The laminate of the coating film of the adhesive composition P and the release sheet 14 can be produced, for example, as follows. The above-mentioned adhesive composition P and a coating liquid containing a solvent if desired are applied to the peeling surface of the release sheet 14 and heat-treated to form a coating film.

The heat treatment can also be used as a drying treatment for volatilizing the diluting solvent or the like of the coating liquid. When the heat treatment is performed, the heating temperature is preferably 50 to 150 ° C, particularly preferably 70 to 120 ° C. The heating time is preferably 30 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes.

After the hard coat layer 12 on the base material 11 and the coating film of the adhesive composition P on the release sheet 14 are bonded together, curing is performed. This curing is usually carried out at room temperature (for example, 23 ° C., 50% RH) for about 1 to 2 weeks. As a result, the coating film of the adhesive composition P becomes the adhesive layer 13, and the adhesive sheet 1 for a battery is manufactured.

As another method for producing the battery pressure-sensitive adhesive sheet 1 according to the present embodiment, the battery pressure-sensitive adhesive sheet 1 may be manufactured by forming the hard coat layer 12 and the pressure-sensitive adhesive layer 13 on the base material 11 in this order.

[Lithium-ion battery]
The lithium ion battery according to the embodiment of the present invention is fixed inside the battery in a state where two or more conductors are in contact with each other by using the above-mentioned adhesive sheet for a battery. At least one of the two or more conductors is preferably in the form of a sheet and at least one in the form of a line or tape. Hereinafter, the lithium ion battery according to the preferred embodiment will be described.

As shown in FIG. 2, the lithium ion battery 2 according to the present embodiment includes a bottomed cylindrical outer body 21 whose bottom portion constitutes a negative electrode terminal 23, and a positive electrode terminal 22 provided in an opening of the outer body 21. The electrode body 24 provided inside the exterior body 21 is provided. Further, an electrolytic solution is sealed inside the lithium ion battery 2.

The electrode body 24 is a sheet-shaped (strip-shaped) positive electrode current collector 241 on which the positive electrode active material layer 241a is laminated, and a negative electrode current collector 242 on which the negative electrode active material layer 242a is laminated, and between them. It is provided with an intervening separator 243. The laminate of the positive electrode current collector 241 and the positive electrode active material layer 241a may be referred to as a positive electrode, and the laminate of the negative electrode current collector 242 and the negative electrode active material layer 242a may be referred to as a negative electrode. It may be called an electrode. The positive electrode, the negative electrode, and the separator 243 are each wound and inserted into the exterior body 21.

Further, as shown in FIG. 3, a linear or tape-shaped electrode take-out tab 244 is attached to the positive electrode current collector 241 by the battery adhesive sheet 1 described above, whereby the electrode take-out tab 244 is attached. It is electrically connected to the positive electrode current collector 241. The electrode extraction tab 244 is also electrically connected to the positive electrode terminal 22. 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 electrolytic solution used in the lithium ion battery 2 is usually a non-aqueous electrolytic solution. As the non-aqueous electrolyte solution, for example, a solution in which a lithium salt as an electrolyte is dissolved in a mixed solvent of a cyclic carbonate ester and a lower chain carbonate ester is preferable. Lithium salts include fluorine-based complex salts such as _{lithium hexafluorophosphate (LiPF 6} ) and lithium borofluoride (LiBF _{4 ), LiN (SO 2} Rf) ₂ , LiC (SO ₂ Rf) ₃ (however, Rf = CF ₃ , C ₂ F ₅ ) etc. are used. Further, 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 preferably mentioned.

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

In the lithium ion battery 2 according to the present embodiment, the electrode extraction tab 244 is attached to the positive electrode current collector 241 by the battery adhesive sheet 1. Even when the pressure-sensitive adhesive sheet 1 for a battery is immersed in a non-aqueous electrolyte solution, the pressure-sensitive adhesive layer 13 is prevented from coagulating and breaking due to swelling, and the positive electrode current collector 241 and the electrode take-out tab 244 are separated from each other. Demonstrates excellent adhesive strength. Further, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 13 is difficult to elute into the electrolytic solution, and the pressure-sensitive adhesive does not adversely affect the battery performance.

Further, since the battery pressure-sensitive adhesive sheet 1 includes the hard coat layer 12, the insulating property can be ensured even when the base material 11 and the pressure-sensitive adhesive layer 13 are carbonized.

From the above, the lithium ion battery 2 according to the present embodiment suppresses performance deterioration, malfunction, thermal runaway and short circuit caused by the battery adhesive sheet 1, and also has a temperature even under a large current condition. It is expected to have excellent stability and safety.

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 battery adhesive sheet 1, the hard coat layer 12 and / or the release sheet 14 may be omitted. Further, in the battery adhesive sheet 1, another layer may be provided between the base material 11 and the hard coat layer 12.

Hereinafter, the present invention will be described in more detail 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. 1. Formation of hard coat layer on substrate 40 parts by mass of dipentaerythritol hexaacrylate (material in which no glass transition point is observed after curing) as an active energy ray-curable component and 5 parts by mass of hydroxycyclohexylphenyl ketone as a photopolymerization initiator 20 parts by mass (solid content conversion value; the same applies hereinafter) of organosilica sol (manufactured by Nissan Chemical Co., Ltd., trade name "MEK-ST"; average particle size 30 nm) as an inorganic filler is mixed and diluted with methyl ethyl ketone. Prepared a coating solution for the hard coat layer.

After applying the above coating liquid to one surface of a polyimide film as a base material (manufactured by Toray DuPont, trade name "Kapton 100H", thickness 25 μm, flame retardant level V-0 of UL94 standard) with a knife coater, It was dried at 70 ° C. for 1 minute. Next, the coating film was cured by irradiating the coating film with ultraviolet rays (illuminance 230 mW / cm ² , light intensity 510 mJ / cm ^2). As a result, a first laminate in which a hard coat layer having a thickness of 2 μm was formed on one surface of the base material was obtained.

In the obtained first laminate, as a steel wool resistance test, the surface of the hard coat layer was rubbed 10 cm 10 times with a load of ^{250 g / cm 2 using # 0000 steel wool.} As a result, it was confirmed that no scratches due to steel wool were formed on the surface of the hard coat layer.

2. Formation of a coating film of an adhesive composition on a release sheet 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of isobornyl acrylate and 5 parts by mass of acrylic acid are copolymerized by a solution polymerization method to (meth) acrylic acid ester. A polymer (Tg: −50 ° C.) was prepared. When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000.

Next, 100 parts by mass of the obtained (meth) acrylic acid ester polymer and aluminum tris (acetylacetoneate) as a metal chelate-based cross-linking agent (manufactured by Soken Kagaku Co., Ltd., trade name "M-5A") 1.55 By mixing 0.5 parts by mass and 0.5 parts by mass of 3-glycidokipropylmethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") as a silane coupling agent and diluting with methyl ethyl ketone, adhesion is achieved. A coating solution for the agent layer was prepared.

The obtained coating liquid is applied to the peeling surface of a release sheet (manufactured by Lintec Corporation, trade name "PET251130") in which one side of a polyethylene terephthalate film is peeled with a silicone-based release agent, and then applied with a knife coater, and then at 120 ° C. Heat treated for minutes. As a result, a second laminate in which the coating film of the adhesive composition was laminated on the peeled surface of the release sheet was obtained.

3. 3. Preparation of Adhesive Sheet for Batteries The surface of the first laminate prepared as described above on the hard coat layer side and the surface of the second laminate prepared as described above on the coating film side of the adhesive composition are bonded together. Then, it was cured at 23 ° C. and 50% RH for 7 days. As a result, an adhesive sheet for a battery was obtained in which the coating film of the adhesive composition was an adhesive layer. The thickness of the pressure-sensitive adhesive layer was 7 μm. The thickness of the pressure-sensitive adhesive layer was calculated by determining the total thickness of the pressure-sensitive adhesive sheet for batteries and subtracting the thicknesses of the first laminate and the release sheet from the total thickness.

[Example 2]
A (meth) acrylic acid ester polymer (Tg: −44 ° C.) was prepared by copolymerizing 75 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of isobornyl acrylate and 5 parts by mass of acrylic acid by a solution polymerization method. When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000. A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the (meth) acrylic acid ester polymer obtained above was used as the (meth) acrylic acid ester polymer.

[Example 3]
A (meth) acrylic acid ester polymer (Tg: −38 ° C.) was prepared by copolymerizing 70 parts by mass of 2-ethylhexyl acrylate, 25 parts by mass of isobornyl acrylate and 5 parts by mass of acrylic acid by a solution polymerization method. When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000. A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the (meth) acrylic acid ester polymer obtained above was used as the (meth) acrylic acid ester polymer.

[Example 4]
87.5 parts by mass of 2-ethylhexyl acrylate, 7.5 parts by mass of isobornyl acrylate and 5 parts by mass of acrylic acid are copolymerized by a solution polymerization method to obtain a (meth) acrylic acid ester polymer (Tg: -58 ° C.). Was prepared. When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000. A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the (meth) acrylic acid ester polymer obtained above was used as the (meth) acrylic acid ester polymer.

[Example 5]
79 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of isobornyl acrylate and 1 part by mass of acrylic acid were copolymerized by a solution polymerization method to prepare a (meth) acrylic acid ester polymer (Tg: −49 ° C.). When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000. A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the (meth) acrylic acid ester polymer obtained above was used as the (meth) acrylic acid ester polymer.

[Example 6]
80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of cyclohexyl acrylate and 5 parts by mass of acrylic acid were copolymerized by a solution polymerization method to prepare a (meth) acrylic acid ester polymer (Tg: −55 ° C.). When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000. A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the (meth) acrylic acid ester polymer obtained above was used as the (meth) acrylic acid ester polymer.

[Example 7]
80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of n-dodecyl acrylate and 5 parts by mass of acrylate are copolymerized by a solution polymerization method to prepare a (meth) acrylic acid ester polymer (Tg: -28 ° C.). did. When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000. A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the (meth) acrylic acid ester polymer obtained above was used as the (meth) acrylic acid ester polymer.

[Example 8]
95 parts by mass of 2-ethylhexyl acrylate and 5 parts by mass of acrylic acid were copolymerized by a solution polymerization method to prepare a (meth) acrylic acid ester polymer (Tg: −65 ° C.). When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 700,000. A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the (meth) acrylic acid ester polymer obtained above was used as the (meth) acrylic acid ester polymer.

[Comparative Example 1]
60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate and 20 parts by mass of 2-hydroxyethyl acrylate are copolymerized by a solution polymerization method to obtain a (meth) acrylic acid ester polymer (Tg: -38 ° C.). Was prepared. When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 500,000.

Next, 100 parts by mass of the obtained (meth) acrylic acid ester polymer and aluminum tris (acetylacetonate) as a metal chelate-based cross-linking agent (manufactured by Soken Kagaku Co., Ltd., trade name "M-5A") 0.93 Adhesive by mixing 0.5 parts by mass with 0.5 parts by mass of 3-glycidoxypropylmethyldimethoxysilane (manufactured by Shinetsu Chemical Co., Ltd., trade name "KBM-403") as a silane coupling agent and diluting with methyl ethyl ketone. A coating solution for the agent layer was prepared. An adhesive sheet for a battery was produced in the same manner as in Example 1 except that the obtained coating liquid for the pressure-sensitive adhesive layer was used as the coating liquid for the pressure-sensitive adhesive layer.

[Comparative Example 2]
76.8 parts by mass of n-butyl acrylate, 19.2 parts by mass of methyl acrylate and 4 parts by mass of acrylic acid are copolymerized by a solution polymerization method to obtain a (meth) acrylic acid ester polymer (Tg: -40 ° C). Was prepared. When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 1 million.

Next, 100 parts by mass of the obtained (meth) acrylic acid ester polymer and aluminum tris (acetylacetonate) as a metal chelate-based cross-linking agent (manufactured by Soken Kagaku Co., Ltd., trade name "M-5A") 0.31 By mass, 2.35 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., trade name "BHS8515") as an isocyanate-based cross-linking agent, and 3-glycidoxypropylmethyldimethoxysilane as a silane coupling agent ( A coating liquid for an adhesive layer was prepared by mixing 0.5 parts by mass with 0.5 parts by mass of Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") and diluting with methyl ethyl ketone. An adhesive sheet for a battery was produced in the same manner as in Example 1 except that the obtained coating liquid for the pressure-sensitive adhesive layer was used as the coating liquid for the pressure-sensitive adhesive layer.

[Comparative Example 3]
96 parts by mass of n-butyl acrylate and 4 parts by mass of acrylic acid were copolymerized by a solution polymerization method to prepare a (meth) acrylic acid ester polymer (Tg: −50 ° C.). When the molecular weight of this polymer was measured by gel permeation chromatography (GPC) described later, the weight average molecular weight (Mw) was 1 million.

Next, 100 parts by mass of the obtained (meth) acrylic acid ester polymer and aluminum tris (acetylacetonate) as a metal chelate-based cross-linking agent (manufactured by Soken Kagaku Co., Ltd., trade name "M-5A") 0.93 Adhesive by mixing 0.5 parts by mass with 0.5 parts by mass of 3-glycidoxypropylmethyldimethoxysilane (manufactured by Shinetsu Chemical Co., Ltd., trade name "KBM-403") as a silane coupling agent and diluting with methyl ethyl ketone. A coating solution for the agent layer was prepared. An adhesive sheet for a battery was produced in the same manner as in Example 1 except that the obtained coating liquid for the pressure-sensitive adhesive layer was used as the coating liquid for the pressure-sensitive adhesive layer.

Here, the above-mentioned weight average molecular weight (Mw) is a standard polystyrene-equivalent weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
-GPC measuring device: HLC-8020 manufactured by Tosoh Corporation
-GPC column (passed in the following order): TSK guard volume HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
TSK gel G2000HXL
-Measurement solvent: tetrahydrofuran-Measurement temperature: 40 ° C

[Test Example 1] (Measurement of gel fraction by immersion in electrolyte solvent)
In the production of the adhesive sheet for batteries of Examples and Comparative Examples, a release sheet (Lintec) in which the surface of the adhesive composition of the second laminate on the coating film side and one side of the polyethylene terephthalate film were peeled with a silicone-based release agent. It was bonded to the peeled surface of the company, trade name "PET251130"). Then, it was cured at 23 ° C. and 50% RH for 7 days to obtain a measurement sheet composed of an adhesive layer alone whose both sides were protected with a release sheet.

The obtained measurement sheet was cut into a size of 80 mm × 80 mm, the release sheet protecting both sides of the adhesive layer was peeled off, wrapped in a polyester mesh (mesh size 200), and the mass was weighed with a precision balance. By subtracting the mass of the mesh alone, the mass of the adhesive alone was calculated. The mass at this time is M1. Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in a preparation solution prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1 as an electrolytic solution solvent at 80 ° C. for 72 hours. After that, the pressure-sensitive adhesive layer is taken out and once immersed in ethanol to dissolve and remove the adhered electrolyte solvent, and then air-dried for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and further in an oven at 80 ° C. It was dried in the oven for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is M2. The gel fraction (%) was calculated from the formula (M2 / M1) × 100. The results are shown in Table 1.

[Test Example 2] (Measurement of Adhesive Strength Before Immersion in Electrolyte Solution Solvent)
The adhesive strength of the battery adhesive sheet according to this test example was measured according to JIS Z0237: 2009 except for the operations shown below.

The battery adhesive sheets obtained in Examples and Comparative Examples were cut into a width of 25 mm and a length of 250 mm, and then the release sheet was peeled off to obtain a test piece. The exposed adhesive layer of this test piece was attached to an aluminum plate as an adherend using a 2 kg rubber roller in an environment of 23 ° C. and 50% RH. Immediately after that, the test piece is peeled 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, trade name “Tencilon UTM-4-100”). The adhesive strength (N / 25 mm) was measured. This measured value was taken as the adhesive strength before immersion in the electrolytic solution solvent. The results are shown in Table 1.

[Test Example 3] (Measurement of Adhesive Strength After Immersion in Electrolyte Solution Solvent)
The adhesive strength of the battery adhesive sheet according to this test example was measured according to JIS Z0237: 2009 except for the operations shown below.

The battery adhesive sheets obtained in Examples and Comparative Examples were cut into a width of 25 mm and a length of 250 mm, and then the release sheet was peeled off to obtain a test piece. The exposed adhesive layer of the test piece was attached to an aluminum plate as an adherend using a 2 kg rubber roller in an environment of 23 ° C. and 50% RH, and then left in the same environment for 20 minutes. Then, with the test piece attached to the aluminum plate, it was immersed in a preparation solution prepared by mixing ethylene carbonate and diethyl carbonate as an electrolytic solution solvent at a volume ratio of 1: 1 at 80 ° C. for 72 hours. Immediately after taking out from the prepared liquid, the adhesive strength (N / 25 mm) was measured in the same manner as described above. This measured value was taken as the adhesive strength after immersion in the electrolytic solution solvent. The results are shown in Table 1.

In the above test, the pressure-sensitive adhesive sheet for batteries of the example did not cause cohesive failure of the pressure-sensitive adhesive layer, but the pressure-sensitive adhesive sheet for batteries of the comparative example caused cohesive failure of the pressure-sensitive adhesive layer.

[Test Example 4] (Evaluation of electrolyte resistance)
The release sheet was peeled off from the battery adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer was attached to an aluminum plate (thickness: 1 mm), which was used as a test piece. _{The obtained test piece was prepared by dissolving lithium hexafluorophosphate (LiPF 6} ) at a concentration of 1 mol / L in a mixed solution of ethylene carbonate and diethyl carbonate as an electrolytic solution in a volume ratio of 1: 1. It was sealed in an aluminum laminate bag together with the liquid and heated in an environment of 80 ° C. for 3 days. Then, the adhesive sheet for the battery was peeled off from the aluminum plate with tweezers. Check the state of the battery adhesive sheet during immersion in the electrolytic solution, the strength of the adhesive force when the battery adhesive sheet is peeled off, and the state when the battery adhesive sheet is peeled off, and withstand electrolysis based on the following criteria. The liquid property was evaluated. Pass 3 or higher. The results are shown in Table 1.
5 ... Peeled off at the interface between the adhesive / adherend (high adhesive strength).
4 ... Peeled off at the adhesive / adherend interface (during adhesive strength).
3 ... Peeled off at the adhesive / adherend interface (low adhesive strength).
2 ... The adhesive swelled and coagulated and destroyed.
1 ... Peeled off during immersion in the electrolytic solution.

As is clear from Table 1, the adhesive sheet for batteries of the examples does not cause cohesive failure in the adhesive layer even when immersed in the electrolytic solution solvent and the electrolytic solution, and has high adhesive strength (adhesion before immersion in the electrolytic solution solvent). 70% or more with respect to force) was shown. Further, it was found that the adhesive of the battery adhesive sheet of the example showed a high gel fraction even after being immersed in the electrolytic solution solvent and was difficult to elute in the electrolytic solution solvent.

The adhesive composition and the adhesive sheet for a battery according to the present invention are suitable for attaching an electrode extraction tab to an electrode (current collector) inside a lithium ion battery.

1 ... Adhesive sheet for batteries 11 ... Base material 12 ... Hard coat layer 13 ... Adhesive layer 14 ... Release sheet 2 ... Lithium ion battery 21 ... Exterior body 22 ... Positive electrode terminal 23 ... Negative electrode terminal 24 ... Electrode body 241 ... Positive electrode current collection Body 241a ... Positive electrode active material layer 242 ... Negative electrode current collector 242a ... Negative electrode active material layer 243 ... Separator 244 ... Electrode extraction tab

Claims (4)

An adhesive sheet used inside a battery including a base material and an adhesive layer laminated on one surface side of the base material.
The base material is a film made of a polymer having a nitrogen-containing ring structure in the main chain.
The pressure-sensitive adhesive layer
The monomer unit constituting the polymer includes (meth) acrylic acid alkyl ester having 6 or more carbon atoms and 20 or less carbon atoms in the alkyl group, and a monomer having a carboxy group in the molecule, and has a weight average molecular weight of 50,000 or more. , 2.5 million or less, formed from an adhesive composition containing a (meth) acrylic acid ester polymer.
The glass transition temperature of the (meth) acrylic acid ester polymer (A) is −70 ° C. or higher and lower than 0 ° C.
Wherein the gel fraction of the pressure-sensitive adhesive after providing a pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer was immersed for 72 hours at 80 ° C. in a solvent non-aqueous electrolyte solution, 80% state, and are 100% or less,
An adhesive sheet used inside a battery , wherein the adhesive has a crosslinked structure. The (meth) acrylic acid ester polymer is used inside the battery according to claim 1, wherein the (meth) acrylic acid ester polymer contains a monomer having an alicyclic structure in the molecule as a monomer unit constituting the polymer. Adhesive sheet to be done. The pressure-sensitive adhesive sheet used inside a battery according to claim 1 or 2, wherein a hard coat layer is formed on the surface of the base material on the side of the pressure-sensitive adhesive layer. Lithium ion characterized in that two or more conductors are fixed in contact with each other using the battery adhesive sheet according to any one of claims 1 to 3 inside the battery. battery.

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