1. An adhesive sheet for use in a battery, characterized in that,

the adhesive sheet is provided with: a base material, a hard coat layer provided on one surface side of the base material, and an adhesive layer provided on the surface side of the hard coat layer opposite to the base material,

the hard coat layer is formed of a material obtained by curing a composition containing an active energy ray-curable component,

the adhesive constituting the adhesive layer has a gel fraction of 70 to 100% after being immersed in a solvent of a nonaqueous electrolyte at 60 ℃ for 24 hours,

the adhesive is an acrylic adhesive.

2. The adhesive sheet according to claim 1, wherein the pencil hardness of the hard coat layer provided on the base material is HB or more as measured in accordance with JIS K5600-5-4.

3. The adhesive sheet according to claim 1, wherein the substrate has flame retardancy of flame retardancy grade V-0 satisfying the UL94 standard.

4. The adhesive sheet according to claim 1, wherein the adhesive sheet attached to an aluminum plate has an adhesive force to the aluminum plate of 0.1 to 15N/25mm after being immersed in a solvent for a nonaqueous electrolyte at 100 ℃ for 6 hours.

5. The adhesive sheet according to claim 1, wherein the storage modulus of the adhesive layer at 120 ℃ is 1 to 500 kPa.

Background

In some batteries, a strip-shaped laminate body in which a positive electrode, a separator, and a negative electrode are laminated in this order is housed in a wound state. Electrode extraction tabs (tab) formed of an electric conductor are connected to the positive electrode and the negative electrode, respectively, and the positive electrode and the negative electrode are electrically connected to a positive electrode terminal and a negative electrode terminal of the battery, respectively, through the electrode extraction tabs.

An adhesive tape was used for stopping the winding of the laminate and fixing the electrode lead tab to the electrode. Such adhesive tapes are disclosed in patent documents 1 and 2. These adhesive tapes are composed of a base material and an adhesive layer provided on one surface of the base material.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5639733

Patent document 2: japanese patent laid-open publication No. 2011-138632

Disclosure of Invention

Technical problem to be solved by the invention

The adhesive tape used inside the battery may come into contact with an electrolyte filled inside the battery or be exposed to heat generated during charging and discharging. In particular, in recent years, small and high-performance batteries have been developed, and the adhesive tapes used in the interior of the batteries are exposed to more severe conditions.

In order to exhibit the performance as a battery, it is required that the adhesive tape maintain high adhesion to an adherend even when exposed to severe conditions as described above. However, conventional adhesive tapes sometimes do not sufficiently satisfy such a requirement.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive sheet capable of suppressing peeling from an adherend while maintaining an adhesive force well even when the adhesive sheet is in contact with an electrolytic solution.

Means for solving the problems

In order to achieve the above object, according to a first aspect of the present invention, there is provided an adhesive sheet for use in a battery, comprising: a substrate, a hard coat layer provided on one surface side of the substrate, and an adhesive layer provided on the surface side of the hard coat layer opposite to the substrate (invention 1).

In the adhesive sheet according to the invention (invention 1), the hard coat layer is provided between the base material and the adhesive agent layer, whereby the hard coat layer blocks permeation of the electrolyte even when the adhesive sheet is in contact with the electrolyte. Thus, the adhesive layer maintains the adhesive force well, and the adhesive sheet is difficult to peel off from the adherend. Thus, in the battery using the adhesive sheet, the performance reduction caused by the adhesive sheet is suppressed.

In the above invention (invention 1), it is preferable that: the hard coat layer provided on the base material has a pencil hardness of HB or more as measured in accordance with JIS K5600-5-4 (invention 2).

In the above invention (inventions 1 and 2), it is preferable that: the substrate has flame retardancy of flame retardancy grade V-0 satisfying UL94 standard (invention 3).

In the above inventions (inventions 1 to 3), it is preferable that: the adhesive constituting the adhesive layer has a gel fraction of 20 to 100% after being immersed in a solvent of a nonaqueous electrolyte at 60 ℃ for 24 hours (invention 4).

In the above inventions (inventions 1 to 4), it is preferable that: the adhesive sheet to be attached to an aluminum plate is immersed in a solvent for a nonaqueous electrolyte at 100 ℃ for 6 hours, and the adhesive force of the adhesive sheet to the aluminum plate is 0.1 to 15N/25mm (invention 5).

In the above invention (inventions 1 to 5), it is preferable that: the adhesive layer has a storage modulus at 120 ℃ of 1 to 500kPa (invention 6).

Effects of the invention

According to the present invention, there is provided an adhesive sheet capable of suppressing peeling from an adherend while maintaining an adhesive force well even when the adhesive sheet is in contact with an electrolytic solution.

Drawings

Fig. 1 is a sectional view of an adhesive sheet according to an embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

[ adhesive sheet ]

As shown in fig. 1, the adhesive sheet 1 according to the present embodiment is composed of a substrate 11, a hard coat layer 12 provided on one surface side of the substrate 11, an adhesive layer 13 provided on the hard coat layer 12 on the side opposite to the substrate 11, and a release sheet 14 provided on the adhesive layer 13 on the side opposite to the hard coat layer 12.

According to the adhesive sheet 1 of the present embodiment, since the electrolyte solution that has entered the base material 11 is blocked by the hard coat layer 12, the electrolyte solution is prevented from penetrating through the hard coat layer 12 and reaching the adhesive layer 13. This reduces the amount of the electrolyte that enters the adhesive layer 13.

In addition, even in a structure in which the hard coat layer 12 is laminated on the surface of the substrate 11 opposite to the adhesive agent layer 13, rather than being laminated between the substrate 11 and the adhesive agent layer 13, it can be expected that the intrusion of the electrolytic solution is reduced to some extent. However, even with such a configuration, the electrolyte solution that has entered from the end of the substrate 11 reaches the adhesive layer 13 that is in contact with the substrate 11 through the inside of the substrate 11. In general, a material having very high permeability of the electrolyte solution is also present as a material of the substrate 11, and when such a material is used, a predetermined amount of the electrolyte solution is impregnated into the substrate 11 only from the end portion, and then is impregnated into the adhesive layer 13.

In contrast, in the adhesive sheet 1 according to the present embodiment, since the hard coat layer 12 is provided between the base material 11 and the adhesive layer 13, not only the electrolyte solution that has entered the base material 11 from the main surface is blocked by the hard coat layer 12, but also the electrolyte solution that has entered the base material 11 from the end portion is blocked by the hard coat layer 12, and thus the electrolyte solution can be prevented from reaching the adhesive layer 13.

As described above, in the adhesive sheet 1 according to the present embodiment, the amount of the electrolytic solution that enters the adhesive layer 13 is reduced, whereby the adhesive force is favorably maintained, and the peeling of the adhesive sheet 1 from the adherend is suppressed. Thus, in the battery using the adhesive sheet 1, the performance deterioration caused by the adhesive sheet is suppressed. Further, by reducing the amount of the electrolytic solution that enters the adhesive layer 13, the amount of the components of the adhesive layer 13 that elute into the electrolytic solution is reduced. This can suppress failure, thermal runaway, and short circuit of the battery using the adhesive sheet 1.

1. Base material

In the pressure-sensitive adhesive sheet 1 according to the present embodiment, the substrate 11 preferably has flame retardancy of flame retardancy grade V-0 that satisfies the UL94 standard. By providing the substrate 11 with such flame retardancy, even when heat is generated by the use of a normal battery, the substrate 11 can be prevented from being denatured or deformed. In addition, even when the battery is in a bad condition and generates excessive heat, the ignition and combustion of the base material 11 can be suppressed, thereby preventing serious accidents.

The material of the substrate 11 can be appropriately selected from the viewpoints of flame retardancy, heat resistance, insulation properties, reactivity with an electrolytic solution, permeability of an electrolytic solution, and the like. In particular, a resin film is preferably used as the substrate 11. Examples of the resin film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films such as polyethylene films and polypropylene films; a resin film such as cellophane (cellophane), a diacetylcellulose film, a triacetyl cellulose film, an acetylcellulose butyrate film, a polyvinyl chloride film, a polyvinylidene chloride film, a polyvinyl alcohol film, an ethylene-vinyl acetate copolymer film, a polystyrene film, a polycarbonate film, a polymethylpentene film, a polysulfone film, a polyetheretherketone film, a polyethersulfone film, a polyetherimide film, a fluororesin film, a polyamide film, a polyimide film, a polyamideimide film, an acrylic resin film, a polyurethane resin film, a norbornene polymer film, a cyclic olefin polymer film, a cyclic conjugated diene polymer film, a vinyl alicyclic hydrocarbon polymer film, or a laminate film thereof. In particular, a polyimide film, a polyetherimide film, or a polyetheretherketone film, which exhibits excellent flame retardancy and heat resistance, is preferably used, and among them, a polyimide film exhibiting higher heat resistance is preferably used. In the present specification, "polymer" also includes the concept of "copolymer".

The thickness of the substrate 11 is preferably 5 to 200 μm, particularly preferably 10 to 100 μm, and further preferably 15 to 40 μm. By setting the thickness of the substrate 11 to 5 μm or more, appropriate rigidity is imparted to the substrate 11, and even when curing shrinkage occurs when the hard coat layer 12 is formed on the substrate 11, the occurrence of warpage can be effectively suppressed. Further, by setting the thickness of the base material 11 to 200 μm or less, the adhesive sheet 1 has appropriate flexibility, and even when the adhesive sheet 1 is stuck to a surface having a level difference as in the case of fixing an electrode and an electrode tab, the level difference can be satisfactorily followed.

2. Hard coating

(1) Physical Properties of hard coat layer

In the adhesive sheet 1 according to the present embodiment, the pencil hardness of the hard coat layer 12 in a state of being provided on the base material 11, measured in accordance with JIS K5600-5-4, is preferably HB or more, and particularly preferably H or more. If the hard coat layer 12 has such pencil hardness, the penetration of the hard coat layer 12 by the electrolyte solution can be effectively blocked, and even when the adhesive sheet 1 is in contact with the electrolyte solution, the adhesive layer 13 can maintain the adhesive force well, and the peeling of the adhesive sheet 1 from the adherend can be effectively suppressed. The upper limit of the pencil hardness of the hard coat layer is not particularly limited, but is preferably 9H or less, particularly preferably 6H or less, and further preferably 3H or less, from the viewpoint of obtaining excellent followability to the level difference.

(2) Composition of hard coating

The hard coat layer is preferably formed from a composition containing an organic component and an inorganic filler (hereinafter sometimes referred to as "composition for hard coat layer"). In particular, the hard coat layer is preferably formed 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 an active energy ray and exhibits a desired hardness.

Specific examples of the active energy ray-curable component include polyfunctional (meth) acrylate monomers, (meth) acrylate prepolymers, and active energy ray-curable polymers, and among them, polyfunctional (meth) acrylate monomers and/or (meth) acrylate prepolymers are preferable. The polyfunctional (meth) acrylate monomer and the (meth) acrylate prepolymer may be used alone or in combination. In the present specification, the term (meth) acrylate refers to both acrylate and methacrylate. Other similar terms are also the same.

Examples of the polyfunctional (meth) acrylate monomer include 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, and the like, Polyfunctional (meth) acrylates such as tris (acryloyloxyethyl) isocyanurate, propionic acid-modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and caprolactone-modified dipentaerythritol hexa (meth) acrylate. These may be used alone or in combination of two or more.

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

As the active energy ray-curable polymer, for example, a (meth) acrylate polymer having an active energy ray-curable group in a side chain (hereinafter referred to as "active energy ray-curable (meth) acrylate polymer (a)") can be used. The active energy ray-curable (meth) acrylate polymer (a) is preferably obtained by reacting an acrylic polymer (a1) having a functional group-containing monomer unit with an unsaturated group-containing compound (a2) having a substituent bonded to the functional group thereof. Examples of the unsaturated group include a (meth) acryloyl group and the like.

The active energy ray-curable component constituting the hard coat layer 12 of the present embodiment is preferably an active energy ray-curable component having a glass transition point after curing of 130 ℃ or higher, more preferably 150 ℃ or higher, and particularly preferably one having no glass transition point observed. By making the glass transition point of the active energy ray-curable component as described above, the heat resistance of the hard coat layer 12 becomes excellent, and the performance and safety of a battery including the adhesive sheet 1 provided with such a hard coat layer 12 also become excellent.

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

(2-2) other organic Components

Examples of the organic component that can be used in addition to the active energy ray-curable component include thermosetting resins, thermoplastic resins, and the like. By blending this component, the adhesion between the hard coat layer 12 and the substrate 11 can be further improved. Specific examples of the organic component include polyamide-imide resins, polyether-imide resins, polyimide resins, polyarylate resins, polyether ether ketone resins, polysulfone resins, melamine resins, phenol resins, and the like. Among them, polyamide imide resins having excellent heat resistance are preferable.

(2-3) inorganic Filler

The composition for hard coat layer constituting the hard coat layer 12 of the present embodiment preferably contains an inorganic filler. The hard coat layer 12 of the present embodiment is provided with high surface hardness by containing an inorganic filler.

Preferred examples of the inorganic filler include powders of silica, alumina, boehmite, talc, calcium carbonate, titanium oxide, iron oxide, silicon carbide, boron nitride, zirconium oxide, and the like; beads, single crystal fibers, glass fibers, and the like obtained by spheroidizing these can be used alone or in combination of two or more. Among these inorganic fillers, silica, alumina, boehmite, titania, zirconia and the like are preferable, and silica and alumina are preferable from the viewpoint of hardness, and silica is particularly preferable.

Further, it is preferable that the inorganic filler is surface-modified. As such a particularly preferred inorganic filler, reactive silica can be exemplified.

In the present specification, "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 the organic compound having an active energy ray-curable unsaturated group can be obtained, for example, in general by: the silanol group on the surface of the silica fine particles having an average particle diameter of about 0.5 to 500nm, preferably 1 to 200nm, is reacted with an active energy ray-curable unsaturated group-containing organic compound having a functional group (e.g., isocyanate group, epoxy group, carboxyl group, etc.) capable of reacting with the silanol group. The active energy ray-curable unsaturated group preferably includes a (meth) acryloyl group or a vinyl group.

As the active energy ray-curable unsaturated group-containing organic compound having a functional group reactive with a silanol group, for example, a compound represented by the general formula (I) or the like is preferably used.

[ chemical formula 1]

In the formula, R¹Is a hydrogen atom or a methyl group, R²Is a halogen atom [ chemical formula 2]]The group shown.

[ chemical formula 2]

-OCH₂CH₂OH, -OH or-O (CH)₂)₃-Si(OCH₃)₃

Examples of such compounds include (meth) acrylic acid derivatives such as (meth) acrylic acid, (meth) acryloyl chloride, (meth) acryloyloxyethyl isocyanate, glycidyl (meth) acrylate, 2, 3-iminopropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and acryloyloxypropyltrimethoxysilane. These (meth) acrylic acid derivatives may be used alone or in combination of two or more.

As the organic-inorganic composite material (silicone sol) containing such reactive silica and the above-mentioned polyfunctional (meth) acrylate monomer and/or (meth) acrylate prepolymer, for example, the trade names "OPSTAR Z7530", "OPSTAR Z7524", "OPSTAR TU 4086", "OPSTAR Z7537" (manufactured by JSR Corporation) and the like can be used.

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

The average particle diameter of the inorganic filler used in the present embodiment is preferably 1 to 1000nm, particularly preferably 10 to 500nm, and further preferably 20 to 200 nm. By setting the average particle diameter of the inorganic filler to 1nm or more, the hard coat layer 12 obtained by curing the composition for a hard coat layer has a higher surface hardness. Further, by setting the average particle size of the inorganic filler to 1000nm or less, the dispersibility of the inorganic filler in the composition for a hard coat layer becomes excellent, and when the hard coat layer 12 is formed on the substrate 11, it is possible to effectively prevent the generation of irregularities on the surface of the hard coat layer 12 opposite to the substrate 11. Further, by forming the adhesive agent layer 13 on this surface, it is possible to obtain very high smoothness on the surface of the adhesive agent layer 13 opposite to the hard coat layer 12. This allows the adhesive layer 13 to exhibit excellent adhesion to an adherend. The average particle diameter of the inorganic filler is a value measured by zeta potential measurement.

The content of the inorganic filler in the hard coat layer 12 of the present embodiment is preferably 0 to 90 wt% (90 wt% or less), more preferably 30 to 85 wt%, particularly preferably 40 to 80 wt%, and further preferably 45 to 70 wt% with respect to the hard coat layer 12. When the inorganic filler is contained, the surface hardness of the hard coat layer 12 is increased by setting the content of the inorganic filler to 30% by weight or more. On the other hand, when the content of the inorganic filler is 90% by weight or less, a layer using the composition for a hard coat layer can be easily formed.

(2-4) other Components

The composition for forming the hard coat layer 12 of the present embodiment may contain various additives in addition to the above components. Examples of the various additives include photopolymerization initiators, antioxidants, antistatic agents, silane coupling agents, aging inhibitors, thermal polymerization inhibitors, colorants, surfactants, storage stabilizers, plasticizers, lubricants, defoaming agents, and organic fillers.

When the hard coat layer 12 is formed using an active energy ray-curable component, a photopolymerization initiator is preferably used. 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 examples thereof include acylphosphine oxide compounds, benzoin compounds, acetophenone compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and the like. Specific examples thereof include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-dimethoxy-1, 2-diphenylethan-1-one, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfide (benzyl phenyl sulfite), tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, diacetyl, and β -chloroanthraquinone.

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

(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. By making the thickness of the hard coat layer 12 0.1 μm or more, permeation of the hard coat layer 12 by the electrolytic solution is effectively blocked. Further, by setting the thickness of the hard coat layer 12 to 10 μm or less, the adhesive sheet 1 has appropriate flexibility, and even when the adhesive sheet 1 is stuck to a surface having a level difference as in the case of fixing an electrode and an electrode tab, the adhesive sheet 1 can satisfactorily follow the level difference.

3. Adhesive layer

(1) Physical Properties of adhesive/adhesive layer

In the adhesive sheet 1 according to the present embodiment, the gel fraction of the adhesive after the adhesive constituting the adhesive layer 13 is immersed in a solvent of a nonaqueous electrolyte at 60 ℃ for 24 hours is preferably 20 to 100%. In particular, when the adhesive constituting the adhesive layer 13 is an acrylic adhesive described later, the gel fraction is preferably 20 to 98%, particularly preferably 50 to 95%, and further preferably 70 to 85%. By setting the gel fraction to 20% or more, even when the adhesive layer 13 is in contact with the electrolytic solution, the elution amount of components from the adhesive layer 13 is suppressed to be low, and thus, failure, thermal runaway, and short-circuiting of the battery using the adhesive sheet 1 can be effectively suppressed. Further, by setting the gel fraction to 98% or less, the adhesive sheet 1 has appropriate flexibility, and even when the adhesive sheet 1 is stuck to a surface having a level difference as in the case of fixing an electrode and an electrode tab, the level difference can be satisfactorily followed. The solvent of the nonaqueous electrolyte here is a preparation solution obtained by mixing ethylene carbonate and diethyl carbonate at a mass ratio of 1:1, and the test method of gel fraction is shown in test examples described later.

In the adhesive sheet 1 according to the present embodiment, the storage modulus at 120 ℃ of the adhesive layer 13 is preferably 1 to 500kPa, particularly preferably 10 to 200kPa, and further preferably 40 to 100 kPa. By setting the storage modulus to the above range, the adhesive layer 13 has sufficient hardness even under relatively high temperature conditions. Therefore, even at the temperature of the electrolyte expected when the battery is actually used, swelling of the adhesive layer 13 is effectively prevented, and a predetermined adhesive force can be maintained. Further, even when pressure is applied to the adhesive sheet 1 as in the case where the adhesive sheet 1 is used for fixing the electrode and the electrode lead tab and winding pressure is applied to the adhesive sheet 1, the adhesive layer 13 is less likely to be deformed, and the adhesive layer 13 is less likely to be extruded from the base material 11 and the hard coat layer 12. This prevents an increase in the contact area with the electrolyte solution, and suppresses the elution amount of components from the adhesive layer 13 to be low. This effectively suppresses failure, thermal runaway, and short-circuiting of the battery using the adhesive sheet 1. The storage modulus was measured as shown in test examples described below.

(2) Composition of adhesive layer

The adhesive constituting the adhesive layer 13 is not particularly limited, and may be appropriately selected from the viewpoint of elution into an electrolytic solution, flame retardancy, heat resistance, insulation, and the like. In particular, as the adhesive constituting the adhesive layer 13, an acrylic adhesive, a silicone adhesive, a rubber adhesive, and a urethane adhesive are preferable. Among these, acrylic adhesives are particularly preferable from the viewpoints of adhesion to the hard coat layer 12, electrodes, and the like, and easiness of fine adjustment of the storage modulus and the adhesive force at 120 ℃ of the adhesive layer 13.

(2-1) acrylic adhesive

The acrylic pressure-sensitive adhesive preferably contains a (meth) acrylate polymer, and particularly preferably contains a polymer obtained by crosslinking the (meth) acrylate polymer with a crosslinking agent.

The (meth) acrylate polymer preferably contains an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group as a monomer constituting the polymer. Thus, the obtained adhesive can exhibit good adhesion. Further, the (meth) acrylate polymer is particularly preferably: a copolymer of an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms, a monomer having a functional group that reacts with a crosslinking agent (a reactive functional group-containing monomer), and other monomers used as needed.

Examples of the alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. Among these, alkyl (meth) acrylates having an alkyl group of 1 to 8 carbon atoms are preferable from the viewpoint of further improving the adhesion, and methyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are particularly preferable. These may be used alone or in combination of two or more.

The (meth) acrylate polymer preferably contains 40 to 99 mass%, particularly preferably 50 to 90 mass%, and further preferably 75 to 85 mass% of an alkyl (meth) acrylate having 1 to 20 carbon atoms and an alkyl group as a monomer unit constituting the polymer.

The reactive functional group-containing monomer preferably includes a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), and the like. These may be used alone or in combination of two or more.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable from the viewpoint of reactivity of the hydroxyl group in the obtained (meth) acrylate polymer with a crosslinking agent and copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the carboxyl 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 preferable because of reactivity of the carboxyl group in the obtained (meth) acrylate polymer with a crosslinking agent and copolymerizability with other monomers. 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 preferably contains 0.1 to 40% by mass, particularly preferably 0.5 to 20% by mass, and further preferably 1.0 to 4.0% by mass of a reactive functional group-containing monomer as a monomer unit constituting the polymer. By setting the content of the reactive functional group-containing monomer to 0.1% by mass or more, the cohesive force of the adhesive obtained by building a crosslinked structure with a crosslinking agent described later can be effectively increased. Further, by setting the content to 40 mass% or less, the affinity of the adhesive layer 13 with the electrolyte solution can be prevented from becoming excessively high, and swelling of the adhesive in the adhesive layer 13 due to the electrolyte solution can be prevented.

Examples of the other monomer include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; alicyclic ring-containing (meth) acrylates such as cyclohexyl (meth) acrylate; non-crosslinkable acrylamides such as acrylamide and methacrylamide; (meth) acrylic esters having a non-crosslinkable tertiary amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate; vinyl acetate; styrene, and the like. These may be used alone or in combination of two or more.

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

The weight average molecular weight of the (meth) acrylate polymer is preferably 30 to 250 ten thousand, particularly preferably 40 to 190 ten thousand, and further preferably 70 to 160 ten thousand. When the weight average molecular weight of the (meth) acrylate polymer is 30 ten thousand or more, the adhesive layer 13 is excellent in durability. Further, when the weight average molecular weight of the (meth) acrylate polymer is 250 ten thousand or less, good coatability can be obtained. 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 acrylic pressure-sensitive adhesive, one kind of the (meth) acrylate polymer may be used alone, or two or more kinds may be used in combination.

The crosslinking agent may be a crosslinking agent that reacts with a reactive functional group of the (meth) acrylate polymer, and examples thereof include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, and ammonium salt crosslinking agents. In addition, one kind of the crosslinking agent may be used alone, or two or more kinds may be used in combination.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret and isocyanurate forms thereof; further, adducts with a reactant of a low molecular active hydrogen-containing compound such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, and the like are exemplified. Among them, trimethylolpropane-modified aromatic polyisocyanates are preferable from the viewpoint of reactivity with hydroxyl groups, and trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are particularly preferable.

The amount of the crosslinking agent used is preferably 0.001 to 10 parts by mass, particularly preferably 0.01 to 5 parts by mass, and further preferably 1 to 3 parts by mass, based on 100 parts by mass of the (meth) acrylate polymer.

When the adhesive composition containing the (meth) acrylate polymer and the crosslinking agent is heated or the like, the crosslinking agent reacts with the reactive functional group of the reactive functional group-containing monomer constituting the (meth) acrylate polymer containing the reactive functional group-containing monomer as a monomer unit constituting the polymer. Thus, the crosslinking agent forms a structure in which the (meth) acrylate polymer is crosslinked, and the gel fraction of the obtained adhesive can be set to a desired value, whereby the cohesive force of the adhesive can be increased, and the strength and durability can be improved.

To the acrylic pressure-sensitive adhesive, various additives generally used, for example, a refractive index adjuster, an antistatic agent, a tackifier, a silane coupling agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a softening agent, a filler, a light curing agent, a photopolymerization initiator, and the like may be added as necessary.

(2-2) Silicone adhesive

The silicone-based adhesive preferably contains organopolysiloxane (organopolysiloxane), and particularly preferably contains (a cured product of) addition-type organopolysiloxane. The addition-type organopolysiloxane is preferably an addition-type organopolysiloxane obtained by reacting an organopolysiloxane having a siloxane bond as a main skeleton and having an alkenyl group with an organohydrogenpolysiloxane (organohydrogen polysiloxane).

The organopolysiloxane having an alkenyl group and a siloxane bond as a main skeleton is a compound represented by the following average unit formula (II), and is preferably a compound having at least two alkenyl groups in a molecule.

R¹ _aSiO_(4-a)/2···(II)

In the formula, R¹The monovalent hydrocarbon groups are the same or different and each have 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, and a is a positive number in the range of 1.5 to 2.8, preferably 1.8 to 2.5, more preferably 1.95 to 2.05.

As the above-mentioned R¹Examples of the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom include a vinyl group, an allyl group, and a propenyl groupAlkenyl groups such as isopropenyl, butenyl, hexenyl, cyclohexenyl and octenyl; alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, decyl and the like; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenethyl, and phenylpropyl; examples of the group include those in which some or all of the hydrogen atoms are substituted with a halogen atom such as fluorine, bromine or chlorine, a cyano group, and the like, for example, chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group, and the like. The alkenyl group is preferably a vinyl group, because of the length of the curing time and productivity.

The organohydrogenpolysiloxane has SiH groups in the molecule. The addition reaction between the alkenyl group of the organopolysiloxane and the SiH group of the organohydrogenpolysiloxane proceeds to obtain an addition-type organopolysiloxane.

The silicone adhesive preferably contains a platinum catalyst because the addition-type organopolysiloxane cures well in the presence of a platinum catalyst. Examples of the platinum catalyst include platinum black, platinum tetrachloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, and platinum diacetylacetate.

The content of the platinum catalyst in the silicone adhesive is preferably 0.01 to 3 parts by mass, and particularly preferably 0.05 to 2 parts by mass, per 100 parts by mass of the addition-type organopolysiloxane. When the content of the platinum catalyst is within the above range, the addition type organopolysiloxane can be cured without hindering the application, and the adhesive agent layer 13 can be formed.

In order to improve the adhesion, the addition-type organopolysiloxane may be made to contain an organopolysiloxane (silicone resin) containing 3-functional or 4-functional siloxane units in the molecule.

The content of the organopolysiloxane containing 3-or 4-functional siloxane units in the silicone-based adhesive is preferably 0 to 100 parts by mass, particularly preferably 5 to 70 parts by mass, and more preferably 10 to 50 parts by mass, relative to 100 parts by mass of the addition-type organopolysiloxane.

(2-3) rubber adhesive

The rubber adhesive preferably contains an a-B-a type block copolymer as a rubber elastic component, a tackifier, and an antioxidant for preventing deterioration, which is further contained as necessary.

Examples of the a-B-a type block copolymer include a styrene-isoprene-styrene copolymer, a styrene-butylene-styrene copolymer, a styrene-ethylene-butylene-styrene copolymer, a styrene-olefin-styrene copolymer, polyisoprene, polybutene, and polyisobutylene.

The content of the rubber elastic component in the rubber adhesive is preferably 5 to 50% by mass, and particularly preferably 7 to 45% by mass. If the content of the rubber elastic component is less than 5 mass%, the cohesive force of the rubber adhesive is reduced, and if the content of the rubber elastic component exceeds 45 mass%, the adhesive force of the adhesive layer may be too low.

Examples of the tackifier include rosin-based resins, polyterpene-based resins, coumarone-indene resins, petroleum-based resins, terpene-phenol resins, alkylphenol resins, styrene-based resins, phenol-based resins, xylene resins, and the like.

The content of the tackifier in the rubber adhesive is preferably 10 to 70% by mass, and particularly preferably 15 to 60% by mass. If the content of the thickener is less than 10 mass%, the adhesive force of the adhesive layer is lowered, and if the content of the thickener exceeds 70 mass%, the cohesive force of the rubber adhesive may become too low.

Examples of the antioxidant include butylhydroxytoluene, 2, 6-di-t-butyl-4-methylphenol, 2, 5-di-t-butylhydroquinone, mercaptobenzimidazole, 1-bis (4-hydroxyphenyl) cyclohexane, and phenyl- β -naphthylamine.

When an antioxidant is used, the content of the antioxidant in the rubber adhesive is preferably 0.1 to 10% by mass, and particularly preferably 0.2 to 5% by mass.

(3) Thickness of adhesive layer

The thickness of the adhesive layer 13 is preferably 1 to 50 μm, particularly preferably 3 to 15 μm, and further preferably 4 to 9 μm. By setting the thickness of the adhesive layer 13 to 1 μm or more, the adhesive sheet 1 can exhibit sufficient adhesive force. Further, by setting the thickness of the adhesive layer 13 to 50 μm or less, the amount of the electrolyte solution entering from the end portion of the adhesive layer 13 can be effectively reduced.

4. Release sheet

The release sheet 14 protects the adhesive layer until the use of the adhesive sheet 1, and is released when the adhesive sheet 1 is used. In the adhesive sheet 1 according to the present embodiment, the release sheet 14 is not necessarily required.

As the release sheet 14, for example, a polyethylene film, a polypropylene film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene vinyl acetate film, an ionomer resin film, an ethylene- (meth) acrylic acid copolymer film, an ethylene- (meth) acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, a fluorine resin film, a liquid crystal polymer film, or the like can be used. In addition, crosslinked films thereof may also be used. Further, a laminated film thereof is also possible.

The release surface (surface in contact with the adhesive layer 13) of the release sheet 14 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.

5. Physical properties of the adhesive sheet

In the adhesive sheet 1 according to the present embodiment, the adhesive force of the adhesive sheet 1 to an aluminum plate after immersing the adhesive sheet 1 attached to the aluminum plate in a solvent of a nonaqueous electrolyte at 100 ℃ for 6 hours is preferably 0.1 to 10N/25mm, particularly preferably 0.5 to 5N/25mm, and further preferably 1 to 3N/25 mm. The adhesive sheet 1 according to the present embodiment can achieve an adhesive force in the above range by providing the hard coat layer 12 between the substrate 11 and the adhesive layer 13. Here, the solvent of the nonaqueous electrolytic solution is a preparation solution obtained by mixing ethylene carbonate and diethyl carbonate at a mass ratio of 1: 1. Further, the adhesive force referred to herein means an adhesive force substantially in accordance with JIS Z0237: the adhesive force measured by the 180 ° peel method of 2009 is shown in the test examples described later.

The thickness of the adhesive sheet 1 (the thickness of the release sheet 14) is preferably 10 to 250. mu.m, particularly preferably 15 to 110 μm, and further preferably 20 to 45 μm. By setting the thickness of the adhesive sheet 1 to 10 to 250 μm, the adhesive sheet 1 is a more suitable adhesive sheet having both adhesive force and heat resistance.

[ method for producing adhesive sheet ]

The adhesive sheet 1 according to the present embodiment can be produced, for example, by: a laminate of the substrate 11 and the hard coat layer 12 and a laminate of the adhesive layer 13 and the release sheet 14 were prepared, and these laminates were bonded so that the hard coat layer 12 and the adhesive layer 13 were in contact with each other. From the viewpoint of improving the adhesion between the hard coat layer 12 and the adhesive layer 13, it is also preferable to apply a surface treatment such as corona treatment or plasma treatment to the surface to be bonded of either one or both of them, and then bond the two layers.

The laminate of the substrate 11 and the hard coat layer 12 can be produced, for example, in the following manner. First, a coating agent containing a composition for a hard coat layer and a solvent which is further contained as necessary is applied to one main surface of the substrate 11 and dried. The coating agent may be applied by a conventional method, for example, a bar coating method, a doctor coating method, a meyer bar method, a roll coating method, a blade coating method, a die coating method, or a gravure coating method. The drying can be performed, for example, by heating at 80 to 150 ℃ for about 30 seconds to 5 minutes.

Then, the layer obtained by drying the coating agent is irradiated with active energy rays to cure the layer, thereby forming the hard coat layer 12. As the active energy ray, for example, an active energy ray having an energy quantum in an electromagnetic wave or a charged particle beam can be used, and specifically, an ultraviolet ray or an electron beam can be usedAnd the like. Ultraviolet rays which are easy to handle are particularly preferable. The ultraviolet ray irradiation may be carried out by a high-pressure mercury lamp, a xenon lamp or the like, and the irradiation amount of the ultraviolet ray is preferably 50 to 1000mW/cm in illuminance²Left and right. In addition, the light quantity is preferably 50 to 10000mJ/cm²More preferably 80 to 5000mJ/cm²Particularly preferably 200 to 2000mJ/cm². On the other hand, the electron beam irradiation may be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 krad.

The laminate of the adhesive layer 13 and the release sheet 14 can be produced, for example, in the following manner.

In forming the adhesive layer 13 using an acrylic adhesive, a coating solution containing the acrylic adhesive and a solvent contained as necessary is applied to the release surface of the release sheet 14, and heat treatment is performed to form a coating film. The formed coating film becomes the adhesive layer 13 as it is without requiring a curing period, and becomes the adhesive layer 13 after the curing period when a curing period is required.

The drying treatment when the diluting solvent or the like of the coating solution is volatilized may be used as the heating treatment. When the heating treatment is performed, the heating temperature is preferably 50 to 150 ℃, and particularly preferably 70 to 120 ℃. The heating time is preferably 30 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes. After the heat treatment, a curing period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH) as required. When the acrylic pressure-sensitive adhesive contains a (meth) acrylate polymer having a reactive functional group and a crosslinking agent, the crosslinking agent is heated to form a structure in which the (meth) acrylate polymer is crosslinked.

When the adhesive layer 13 is formed using a silicone adhesive, for example, the adhesive layer 13 can be formed by: the addition-type organopolysiloxane, organopolysiloxane containing 3-or 4-functional siloxane units, and platinum catalyst, which are contained as needed, are diluted to about 10 to 60 mass% with a solvent such as methyl ethyl ketone, toluene, ethyl acetate, or xylene to obtain a coating solution, and the coating solution is applied to the release surface of the release sheet 14 and heated to cure the coating solution. The heating temperature is preferably about 90-180 ℃, and the heating time is preferably about 1-5 minutes.

As another method for producing the adhesive sheet 1 according to the present embodiment, the adhesive sheet 1 may be produced by forming the hard coat layer 12 and the adhesive layer 13 on the substrate 11 in this order.

[ method of Using adhesive sheet ]

The adhesive sheet 1 according to the present embodiment can be used for a battery. In particular, the adhesive sheet 1 can be used inside a battery.

For example, the adhesive sheet 1 according to the present embodiment can be used to fix 2 or more conductors in contact with each other inside a battery. At least one of the electrical conductors may be larger in volume than the other electrical conductors. For example, at least one of the conductors is in the form of a sheet, and at least one of the conductors may be in the form of a wire or a rod. As a specific example, in a battery containing a band-shaped laminate of a positive electrode, a separator, and a negative electrode, a linear or rod-shaped electrode lead tab can be used to fix a sheet-shaped positive electrode and/or negative electrode. In general, such a positive electrode and a negative electrode are made of a metal such as aluminum, and an electrode lead tab is made of a metal such as aluminum or copper.

The adhesive sheet 1 according to the present embodiment can be used in a battery in which an electrolyte solution is sealed, in a state of being in contact with the electrolyte solution. The electrolyte may be an aqueous electrolyte using water as a main solvent, or may be a non-aqueous electrolyte not using water as a main solvent. Examples of the nonaqueous electrolytic solution include an electrolytic solution used for a lithium ion battery, and examples of the electrolytic solution include an electrolytic solution obtained by dissolving a lithium salt as a solute in a mixed solvent of a cyclic carbonate and a lower chain carbonate. As the lithium salt, for example, lithium hexafluorophosphate (LiPF) is used₆) Lithium fluoroborate (LiBF)₄) Fluorine complex salt of (2), or LiN (SO)₂Rf)₂·LiC(SO₂Rf)₃(wherein Rf ═ CF₃，C₂F₅) And the like. In addition, as the cyclic carbonate, ethylene carbonate and propylene carbonate are usedThe lower chain carbonate preferably includes dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and the like. Examples of the other electrolytic solution include an aqueous electrolytic solution such as a zinc sulfate aqueous solution, a copper sulfate aqueous solution, a dilute sulfuric acid aqueous solution, an ammonium chloride aqueous solution, and a zinc chloride aqueous solution.

In the adhesive sheet 1 according to the present embodiment, the hard coat layer 12 is provided between the base material 11 and the adhesive layer 13, and thus the amount of the electrolyte that enters the adhesive layer 13 is reduced, and thus the adhesive strength can be maintained well, and the peeling of the adhesive sheet 1 from an adherend can be suppressed. Thus, in the battery using the adhesive sheet 1, the performance deterioration caused by the adhesive sheet is suppressed. Further, by reducing the amount of the electrolytic solution that enters the adhesive layer 13, the amount of the components of the adhesive layer 13 that elute into the electrolytic solution is reduced. This can suppress failure, thermal runaway, and short circuit of the battery using the adhesive sheet 1. Further, in the battery using the adhesive sheet 1 according to the present embodiment, excellent temperature stability can be expected even under a large current condition.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

For example, the release sheet 14 may be omitted from the adhesive sheet 1. In the adhesive sheet 1, another layer may be provided between the base material 11 and the hard coat layer 12.

Examples

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. Formation of a hard coating on a substrate

A coating liquid for a hard coat layer having a solid content of 20 mass% was prepared by mixing 40 parts by mass of dipentaerythritol hexaacrylate (a material of which glass transition point was not observed after curing) as an active energy ray-curable component, 5 parts by mass of hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and 60 parts by mass (a value converted into a solid content; the same applies hereinafter) of an organic silica sol (manufactured by NISSAN CHEMICAL INDUSTRIES. LT D, trade name "MEK-ST"; average particle diameter 30nm) as an inorganic filler, and diluting with methyl ethyl ketone.

The coating liquid was applied to one surface of a polyimide film (trade name "KAPTON 100H" manufactured by LTD., DU PONT-TORAY CO., LTD., thickness 25 μm, flame retardant grade V-0 according to UL 94) as a substrate by means of a blade coater, and then dried at 70 ℃ for 1 minute. Then, the coating film was irradiated with ultraviolet rays (illuminance: 230 mW/cm)²The quantity of light was 510mJ/cm²) And curing the coating film. Thus, a first laminate having a hard coat layer having a thickness of 2 μm formed on one surface of the substrate was obtained.

2. Formation of adhesive layer on Release sheet

A (meth) acrylate polymer was prepared by copolymerizing 77 parts by mass of butyl acrylate, 20 parts by mass of methyl acrylate, and 3 parts by mass of acrylic acid. The molecular weight of the polymer was measured by Gel Permeation Chromatography (GPC) described later, and the weight average molecular weight (Mw) was 90 ten thousand. Then, 100 parts by mass of the (meth) acrylate polymer, 2.2 parts by mass of trimethylolpropane-modified toluene diisocyanate (manufactured by TOYOCHEM co., LTD, trade name "BHS 8515") as a crosslinking agent, and 0.3 parts by mass of aluminum tris (acetylacetonate) (manufactured by Soken Chemical & Engineering co., LTD., trade name "M-5A") as a crosslinking agent were mixed and diluted with methyl ethyl ketone, thereby preparing a coating liquid for a pressure-sensitive adhesive layer having a solid content concentration of 20 mass%.

The obtained coating liquid was applied to a release-treated surface of a release sheet (manufactured by linetec corporation io n., product name "PET 251130") obtained by release-treating one surface of a polyethylene terephthalate film with a silicone-based release agent by a blade coater, and then heat-treated at 120 ℃ for 1 minute. Thus, a second laminate was obtained in which an adhesive layer made of an acrylic adhesive having a thickness of 5 μm was laminated on the release-treated surface of the release sheet.

3. Production of adhesive sheet

The surface on the hard coat layer side of the first laminate produced as described above was bonded to the surface on the adhesive layer side of the second laminate produced as described above to obtain an adhesive sheet.

[ example 2]

A coating liquid for a hard coat having a solid content of 20 mass% was prepared by mixing 25 parts by mass of dipentaerythritol hexaacrylate, 1 part by mass of hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, 20 parts by mass of a polyamideimide resin (TOYOBO co., ltd., product name "VYLOMAX CHX 02"), and 60 parts by mass of an organic silica sol (NISSAN CHEMICAL industries. ltd., product name "MEK-ST") as an inorganic filler, and diluting with methyl ethyl ketone. An adhesive sheet was produced in the same manner as in example 1, except that this coating liquid for a hard coat layer was used.

[ example 3]

A coating liquid for an adhesive layer having a solid content of 20 mass% was prepared by mixing 100 parts by mass of a Silicone adhesive (product name "SD-4584" manufactured by Dow Corning Toray Silicone co., ltd.) with 0.5 part by mass of a catalyst (product name "CAT-SRX-212" manufactured by Dow Corning Toray Silicone co., ltd.) and diluting the mixture with methyl ethyl ketone. An adhesive sheet was produced in the same manner as in example 1, except that the coating liquid for an adhesive layer was used, and a release sheet (manufactured by Lintec corporation, trade name "PET 50 FD") in which one surface of a polyethylene terephthalate film was subjected to a release treatment with a fluorine-based release agent.

[ example 4]

A coating liquid for an adhesive layer having a solid content of 20 mass% was prepared by mixing 100 parts by mass of polyisobutylene (manufactured by JAPAN BUTYL co. LTD., trade name "Exxon BUTYL 268"), 5 parts by mass of a methacryloyl group-containing polyisoprene rubber (manufactured by KURARAY co., LTD., trade name "UC-203"), and 20 parts by mass of an aliphatic petroleum resin (manufactured by Zeon Corporation, trade name "Quintone a 100") and diluting the mixture with toluene. An adhesive sheet was produced in the same manner as in example 1, except that this coating liquid for an adhesive layer was used.

[ example 5]

A coating liquid for a hard coat layer having a solid content of 20 mass% was prepared by mixing 40 mass parts of dipentaerythritol hexaacrylate as an active energy ray-curable component, 5 mass parts of hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and 60 mass parts of alumina ceramic nanoparticles (manufactured by BYK Japan KK., trade name "NANOBYK-3601") as an inorganic filler, and diluting with methyl ethyl ketone. An adhesive sheet was produced in the same manner as in example 1, except that this coating liquid for a hard coat layer was used.

[ example 6]

A (meth) acrylate polymer was prepared by copolymerizing 60 parts by mass of butyl acrylate, 20 parts by mass of methyl acrylate, and 20 parts by mass of acrylic acid. The molecular weight of the polymer was measured by Gel Permeation Chromatography (GPC) described later, and the weight average molecular weight (Mw) was 60 ten thousand. A coating liquid for an adhesive layer having a solid content of 20 mass% was prepared by mixing 100 mass parts of the (meth) acrylate polymer and 2.2 mass parts of trimethylolpropane-modified toluene diisocyanate (TOYOCHEM co., LTD, product name "BHS 8515") as a crosslinking agent, and diluting with methyl ethyl ketone. An adhesive sheet was produced in the same manner as in example 1, except that this coating liquid for an adhesive layer was used.

[ example 7]

A (meth) acrylate polymer was prepared by copolymerizing 99 parts by mass of butyl acrylate and 1 part by mass of 4-hydroxybutyl acrylate. The molecular weight of the polymer was measured by Gel Permeation Chromatography (GPC) described later, and the weight average molecular weight (Mw) was 150 ten thousand. A coating liquid for an adhesive layer having a solid content of 20 mass% was prepared by mixing 100 mass parts of the (meth) acrylate polymer and 2.2 mass parts of trimethylolpropane-modified toluene diisocyanate (TOYOCHEM co., LTD, product name "BHS 8515") as a crosslinking agent, and diluting with methyl ethyl ketone. An adhesive sheet was produced in the same manner as in example 1, except that this coating liquid for an adhesive layer was used.

[ example 8]

A coating liquid for a hard coat layer having a solid content of 20 mass% was prepared by mixing 40 parts by mass of dipentaerythritol hexaacrylate as an active energy ray-curable component, 5 parts by mass of hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and 60 parts by mass of reactive silica as an inorganic filler (silica fine particles having an acryloyl group on the surface, the average particle diameter of the silica fine particles before surface modification being 15nm), and diluting with methyl ethyl ketone. An adhesive sheet was produced in the same manner as in example 1, except that this coating liquid for a hard coat layer was used.

Comparative example 1

An adhesive sheet was produced in the same manner as in example 1, except that a polyimide film (product name "KAPTON 100H", manufactured by ltd., product name) as a base material was used instead of the first laminate, and one surface of the base material was attached to the surface of the second laminate on the adhesive layer side.

[ test example 1] (measurement of adhesion before and after immersion in electrolyte solvent)

In accordance with JIS Z0237, except for the operations shown below: 2009 the adhesion of the adhesive sheet was measured.

The adhesive sheet obtained in example or comparative example was cut into a width of 25mm and a length of 250mm, and then the release sheet was peeled off to obtain a test piece. The adhesive layer exposed from the test piece was attached to an aluminum plate as an adherend using a 2kg rubber roller in an environment of 23 ℃ and 50% RH, and then left to stand in the same environment for 20 minutes. Then, the test piece was peeled from the above aluminum plate at a peel angle of 180 ℃ and a peel speed of 300 mm/min using a universal tensile tester (ORIENTEC Co., LTD, Tensilon UTM-4-100), and the adhesion (N/25mm) was measured. The measured value was defined as the adhesion before immersion in the electrolyte solvent. The results are shown in Table 1.

The test piece obtained in the same manner as described above was attached to an aluminum plate under the same conditions as described above, and left to stand for 20 minutes. Then, the test piece was immersed in a preparation solution prepared by mixing ethylene carbonate and diethyl carbonate at a mass ratio of 1:1 as an electrolyte solvent for 6 hours at 100 ℃. Then, the test piece was immersed in ethanol, the adhered electrolyte solvent was dissolved and removed, and the piece was left to stand at 23 ℃ and 50% RH for 3 hours after wiping off the ethanol. Then, the adhesive force (N/25mm) was measured in the same manner as described above. The measured value was defined as the adhesion after immersion in the electrolyte solvent. The results are shown in Table 1.

[ test example 2] (evaluation of peeling caused by immersion in electrolyte solution)

The adhesive sheet obtained in example or comparative example was cut into a width of 25mm and a length of 250mm, and then the release sheet was peeled off to obtain a test piece. The adhesive layer exposed from the test piece was attached to an aluminum plate as an adherend using a 2kg rubber roller in an environment of 23 ℃ and 50% RH, and left to stand in the same environment for 20 minutes. Then, the test piece was immersed in a preparation solution prepared by mixing ethylene carbonate and diethyl carbonate at a mass ratio of 1:1 as an electrolyte solvent for 6 hours at 100 ℃. Then, the presence or absence of peeling of the test piece due to the dipping was visually confirmed, and when peeling occurred, the maximum length (mm) of the peeled portion was measured. These results are shown in table 1.

[ test example 3] (measurement of gel fraction by immersion in electrolyte solution)

In the production of the adhesive sheets of examples and comparative examples, the surface on the adhesive layer side of the second laminate was bonded to the release-treated surface of a release sheet (product name "PET 251130" manufactured by linetec corporation) obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment with a silicone-based release agent, to obtain a measurement sheet composed of an adhesive layer having both surfaces protected by the release sheet alone.

The obtained measurement piece was cut into a size of 80mm × 80mm, the release sheets on both sides of the protective adhesive layer were peeled off, and wrapped in a polyester net (mesh size 200), and the mass thereof was weighed with a precision balance, and the mass of the net alone was subtracted to calculate the mass of the adhesive itself. The mass at this time was denoted as M1. Next, the adhesive wrapped in the polyester net was immersed in a preparation solution obtained by mixing ethylene carbonate and diethyl carbonate at a mass ratio of 1:1 as an electrolyte solvent at 60 ℃ for 24 hours. Then, the adhesive layer was taken out and immersed in ethanol once to dissolve and remove the adhering electrolyte solvent, followed by air-drying at 23 ℃ and a relative humidity of 50% for 24 hours and further drying in an oven at 80 ℃ for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the adhesive itself was calculated by subtracting the mass of the web alone. The mass at this time was denoted as M2. The gel fraction (%) was calculated from the formula (M2/M1). times.100. The results are shown in Table 1.

[ test example 4] (measurement of storage modulus)

The release sheet was peeled off from the second laminate obtained in the example or comparative example, and the adhesive layer having a plurality of layers was laminated so that the thickness became 0.6 mm. A cylindrical body (height: 0.6mm) having a diameter of 8mm was punched out from the laminate of the obtained adhesive layers, and this was used as a sample.

For the above sample, the storage modulus (MPa) was measured by a torsional shear method (ね bending method りせ one end) under the following conditions using a viscoelasticity measuring apparatus (MCR 300 manufactured by Physica Co., Ltd.) according to JIS K7244-6. The measurement results are shown in table 1.

Measuring frequency: 1Hz

Measuring temperature: 120 deg.C

[ test example 5] (evaluation of Pencil hardness)

The hard coat layers in the first laminates obtained in the production of the adhesive sheets of examples and comparative examples were measured for pencil hardness in accordance with JIS K5600-5-4. A pencil scratch hardness tester (product name "No. 553-M" manufactured by YASUDA SEIKI SEISAKUSHO, LTD.) was used for the measurement, and the scratching speed was set to 1 mm/sec. The results are shown in Table 1.

[ Table 1]

As is clear from table 1, the adhesive sheets according to examples showed higher adhesive force and less peeling amount after being immersed in the solvent of the electrolytic solution than the adhesive sheets according to comparative examples.

Industrial applicability

The adhesive sheet of the present invention is suitable as an adhesive sheet used in a state of being in contact with an electrolyte inside a battery.

Description of the reference numerals

1 … adhesive sheet

11 … base material

12 … hard coating

13 … adhesive layer

14 … Release sheet