Adhesive sheet

Abstract

To provide an adhesive sheet having an adhesion layer capable of exhibiting excellent hot water resistance while having sufficient initial adhesion even with an adherend being a solid electrolyte membrane of a solid polymer fuel cell.SOLUTION: An adhesive sheet includes a substrate layer and an adhesion layer overlapping at least one side of the substrate layer, and composed of an adhesive agent. The adhesive agent includes a (meth)acrylate having an oxetane group, a polycarbonate urethane (meth)acrylate and a photoinitiator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet. [Background technology]

[0002] Conventionally, polyurethane adhesives have been widely used as adhesives for various plastics due to their adhesive stability in low temperature ranges (e.g., -10°C to 15°C), as well as their adhesiveness, flexibility, processability, and ease of various molecular designs in room temperature ranges (25±10°C). The polyurethane-based adhesives include those that contain polyester polyol or acrylic polyol as a main component and polyisocyanate as a crosslinking agent, and are used by generating urethane bonds by promoting a crosslinking reaction between the main component and the crosslinking agent, and those that contain polyurethane having a certain chain length (so-called polyurethane prepolymer) as a main component and an isocyanate-based crosslinking agent as a crosslinking agent, and are used by promoting a crosslinking reaction between the main component and the crosslinking agent to harden the adhesive.

[0003] Furthermore, Patent Document 1 below describes an adhesive that has excellent moisture and heat resistance as a two-component adhesive that contains a polyurethane resin as a base agent, an epoxy resin, and an isocyanate-based crosslinking agent. Compared to liquid adhesives such as those described in Patent Document 1 below, adhesives are increasingly being used to bond members, particularly from the viewpoint of their superior ease of handling. The adhesive is often used in the form of an adhesive sheet, particularly from the viewpoint of ease of handling. The adhesive sheet generally comprises a base layer formed of a polymer sheet, and an adhesive layer laminated on the base layer and formed of the adhesive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 157604 Summary of the Invention [Problem to be solved by the invention]

[0005] Improvement in moisture and heat resistance (hot water resistance) is required not only for two-component adhesives such as those described in Patent Document 1, but also for adhesive layers of adhesive sheets.

[0006] Furthermore, the adhesive layer of the adhesive sheet is required to be able to ensure sufficient adhesion to the adherend by thermocompression bonding, that is, to ensure sufficient initial adhesion to the adherend. However, when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell, it is difficult to say that this demand is necessarily fully met.

[0007] In view of the problems associated with the prior art, an object of the present invention is to provide an adhesive sheet having an adhesive layer that has sufficient initial adhesion even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell, and that exhibits good hot water resistance. [Means for solving the problem]

[0008] The adhesive sheet according to the present invention comprises: a base layer; and an adhesive layer formed of an adhesive and overlapping at least one surface of the base layer; The adhesive contains a (meth)acrylate having an oxetane group, a polycarbonate-based urethane (meth)acrylate, and a photopolymerization initiator. [Effects of the Invention]

[0009] According to the present invention, an adhesive sheet can be provided which has an adhesive layer that has sufficient initial adhesion even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell, and which also exhibits good hot water resistance. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a schematic cross-sectional view showing the configuration of an adhesive sheet according to an embodiment. [Figure 2] 1 is a schematic cross-sectional view showing an adhesive sheet according to an embodiment attached to a solid electrolyte membrane of a polymer electrolyte fuel cell; DETAILED DESCRIPTION OF THE INVENTION

[0011] An adhesive sheet according to one embodiment of the present invention will be described below with reference to the drawings. Hereinafter, one embodiment of the present invention may be simply referred to as the present embodiment.

[0012] As shown in Fig. 1, the adhesive sheet 10 according to this embodiment is an adhesive sheet in which an adhesive layer 10b formed of an adhesive is laminated on one surface of a base material layer 10a. In the adhesive sheet 10 shown in Fig. 1, the adhesive layer 10b is laminated on only one surface of the base material layer 10a, but the adhesive layer 10b may also be laminated on the other surface of the base material layer 10a. That is, in the adhesive sheet 10, the adhesive layer 10b may be laminated on each of both surfaces of the base material layer 10a.

[0013] In the adhesive sheet 10 according to this embodiment, the adhesive contains a (meth)acrylate having an oxetane group in its molecule, a polycarbonate-based urethane (meth)acrylate, and a photopolymerization initiator. Hereinafter, the acrylate having an oxetane group in its molecule will be referred to as an oxetane group-containing (meth)acrylate (a), the polycarbonate-based urethane acrylate will be referred to as a polycarbonate-based urethane (meth)acrylate (b), and the photopolymerization initiator will be referred to as a photopolymerization initiator (c). In this specification, the term "(meth)acrylate" encompasses both "acrylate" and "methacrylate." The same applies to the term "(meth)acryloyl group."

[0014] [Oxetane group-containing (meth)acrylate (a)] The oxetane group-containing (meth)acrylate (a) has an oxetane group and a (meth)acryloyl group in the molecule. The oxetane ring is a cyclic ether having a saturated four-membered ring structure. That is, the four-membered ring structure contains one oxygen atom. The oxetane group-containing (meth)acrylate (a) may be a monomer or an oligomer, but is preferably a monomer. Examples of the oxetane group-containing (meth)acrylate (a) include (3-methyl-3-oxetanyl)methyl acrylate, (3-ethyloxetan-3-yl)methyl acrylate, (3-methyl-3-oxetanyl)methyl methacrylate, and (3-ethyloxetan-3-yl)methyl methacrylate. Among the various oxetane group-containing (meth)acrylates (a) mentioned above, it is preferable to use (3-ethyloxetan-3-yl)methyl acrylate. An example of a commercially available product of the (3-ethyloxetan-3-yl)methyl acrylate is "OXE-10" manufactured by Osaka Organic Chemical Industry Ltd.

[0015] [Polycarbonate-based urethane (meth)acrylate (b)] The polycarbonate-based urethane (meth)acrylate (b) is an oligomer obtained by radically polymerizing a (meth)acrylic monomer using a radical polymerization initiator on a structural unit of a polycarbonate-based polyurethane obtained by reacting a polycarbonate diol with a diisocyanate. Examples of the diisocyanate include aromatic isocyanates, aliphatic isocyanates, alicyclic isocyanates, and adducts or polymers thereof. As the diisocyanate, one of the above may be used alone, or two or more of them may be used in combination. The diisocyanate is preferably an aliphatic isocyanate such as hexamethylene diisocyanate, or an alicyclic isocyanate such as isophorone diisocyanate or hydrogenated xylylene diisocyanate. Examples of the (meth)acrylic monomer include (meth)acrylic acid and (meth)acrylic acid alkyl esters having an alkyl group with about 1 to 6 carbon atoms. As the acrylic monomer, one of the above may be used alone, or two or more of them may be used in combination.

[0016] In the polycarbonate-based urethane (meth)acrylate (b), the mass ratio of the acrylic component to the urethane component is not particularly limited, but the mass ratio of the urethane component to the acrylic component is preferably in the range of 80:20 to 20:80, and more preferably in the range of 70:30 to 30:70.

[0017] The polycarbonate-based urethane (meth)acrylate (b) is an oligomer obtained as described above, and therefore has, in the molecule, a (meth)acryloyl group derived from the (meth)acrylic monomer, and also has a carbonate bond and a urethane bond derived from the structural unit of the polycarbonate-based polyurethane.

[0018] The polycarbonate-based urethane (meth)acrylate (b) may have the (meth)acryloyl group at one end of the molecular chain or at both ends of the molecular chain, i.e., the polycarbonate-based urethane (meth)acrylate (b) may be monofunctional or bifunctional. The polycarbonate-based urethane (meth)acrylate (b) may have one or more (meth)acryloyl groups in addition to the molecular terminals, i.e., the polycarbonate-based urethane (meth)acrylate (b) may be tri- or higher functional. The polycarbonate-based urethane (meth)acrylate (b) is preferably a bifunctional or higher functional compound having (meth)acryloyl groups at least at both ends of the molecular chain. Examples of commercially available products of the polycarbonate-based urethane (meth)acrylate (b) include "UF-8001G" manufactured by Kyoeisha Chemical Co., Ltd. and "UF-A7-52" manufactured by Kyoeisha Chemical Co., Ltd. Both "UF-8001G" and "UF-A7-52" have acryloyl groups at both ends of the molecular chain.

[0019] The molar ratio R of the amount of the oxetane group to the total amount of (meth)acryloyl groups contained in the adhesive M is preferably 20% or more, and more preferably 25% or more. The molar ratio R M is preferably 50% or less, more preferably 40% or less, and even more preferably 35% or less. When adhesive sheet 10 is subjected to a curing treatment, at least a part of the double bonds of the (meth)acryloyl groups may disappear. M The (meth)acryloyl group in the above also includes a structure derived from the (meth)acryloyl group after the polymerization reaction (a (meth)acryloyl group residue). The molar ratio R M When is in the above numerical range, the adhesive layer 10b can exhibit more sufficient initial adhesion and better hot water resistance even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell. The molar ratio R M can be determined by appropriately combining general analytical methods such as various spectroscopic methods such as infrared spectroscopy, nuclear magnetic resonance spectroscopy, and ion mass spectrometry.

[0020] [Photopolymerization initiator (c)] The photopolymerization initiator (c) promotes the photopolymerization reaction between the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) in the adhesive layer 10b.

[0021] Commercially available photopolymerization initiators (c) include, for example, the Omnirad (registered trademark) series manufactured by IGM Resins. Examples of the Omnirad (registered trademark) series include products under the trade names "Omnirad (registered trademark) EDB," "Omnirad (registered trademark) BMS," "Omnirad (registered trademark) DETX," "Omnirad (registered trademark) TPO," "Omnirad (registered trademark) 380," and "Omnirad (registered trademark) 907." These photopolymerization initiators (c) may be used singly or in combination of two or more. Among the various photopolymerization initiators mentioned above, it is preferable to use a combination of three types: "Omnirad (registered trademark) EDB," "Omnirad (registered trademark) BMS," and "Omnirad (registered trademark) DETX." The chemical compound name of "Omnirad (registered trademark) EDB" is ethyl-4-(dimethylamino)benzobenzoate, the chemical compound name of "Omnirad (registered trademark) BMS" is 4-(4-methylphenylthio)benzophenone, and the chemical compound name of "Omnirad (registered trademark) DETX" is 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1propane.

[0022] The adhesive preferably contains 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more of the photopolymerization initiator (c) per 100 parts by mass in total of the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b). The adhesive may contain 10 parts by mass or less, 7 parts by mass or less, or 5 parts by mass or less of the photopolymerization initiator (c) per 100 parts by mass in total of the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b). Furthermore, when the adhesive contains three types of photopolymerization initiators (c), namely, "Omnirad (registered trademark) EDB" (hereinafter referred to as the first photopolymerization initiator), "Omnirad (registered trademark) BMS" (hereinafter referred to as the second photopolymerization initiator), and "Omnirad (registered trademark) DETX" (hereinafter referred to as the third photopolymerization initiator), the content ratio of the first photopolymerization initiator, the second photopolymerization initiator, and the third photopolymerization initiator is preferably first photopolymerization initiator:second photopolymerization initiator:third photopolymerization initiator = 3 or more and 5 or less:1 or more and 3 or less:1 by mass.

[0023] In the adhesive sheet 10 according to this embodiment, the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) are copolymerized in the adhesive layer 10b. Specifically, the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) are copolymerized by irradiating the adhesive layer 10b with light. That is, the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) are photopolymerized. In this manner, photopolymerization proceeds between the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b), thereby hardening the adhesive layer 10b. The adhesive layer 10b is used by being adhered to an adherend (for example, a solid electrolyte membrane). The adhesive layer 10b may be adhered to the adherend in a cured state, or may be adhered to the adherend before being cured. The adhesive layer 10b may be adhered by thermocompression (hot melt) bonding. When the adhesive layer 10b is adhered to the adherend before being cured, the adhesive layer 10b is cured by being irradiated with light as described above after being adhered to the adherend. After the adhesive layer 10b is cured, it is further thermocompressed to be more fully adhered to the adherend. In other words, the adhesive sheet 10 according to this embodiment is, for example, a hot melt adhesive sheet, and the adhesive forming the adhesive layer 10b is, for example, a hot melt adhesive.

[0024] The wavelength of the light irradiated onto adhesive layer 10b is preferably 200 nm or more and 700 nm or less, more preferably 500 nm or less, and even more preferably includes a wavelength in the ultraviolet (ultraviolet) light range (for example, a wavelength of 380 nm or less). When the irradiation light is ultraviolet light, the photopolymerization initiator (c) is preferably an ultraviolet photoinitiator. The cumulative amount of ultraviolet light on the adhesive layer 10b is 1500 mJ / cm 2 It may be 2000 mJ / cm or more. 2 or more, 2500 mJ / cm 2 It may be 3000 mJ / cm or more. 2 It may be more than that. The upper limit of the cumulative amount of ultraviolet light is usually 6000 mJ / cm 2 is. In order to copolymerize the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) so as to cure the adhesive layer 10b to a C-stage state (completely cured state), the integrated light amount is 2500 mJ / cm 2 2 It is preferable that the concentration is 3000 mJ / cm or more. 2 More preferably, it is equal to or greater than this.

[0025] The photopolymerization is initiated (initiation reaction) when the photopolymerization initiator (c) is decomposed by irradiated light to generate radicals, and then the radicals are added to the double bond moiety of the (meth)acryloyl group of the oxetane group-containing (meth)acrylate (a) or the polycarbonate-based urethane (meth)acrylate (b), thereby generating radicalized (meth)acrylate (hereinafter referred to as (meth)acrylate active species). Next, the (meth)acrylate active species is added to the double bond portion of the (meth)acryloyl group of another (meth)acrylate that has not been radicalized, in the same manner as described above, thereby generating a (meth)acrylate active species (propagating radical) with a longer molecular chain. Then, an addition reaction between such a growing radical and a (meth)acryloyl group of another (meth)acrylate that has not been converted into a radical is repeated, thereby producing a copolymer of the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) (growth reaction).

[0026] That is, the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) are polymerized by a reaction between the (meth)acryloyl groups. Furthermore, since the oxetane group contained in the oxetane group-containing (meth)acrylate (a) does not have a double bond, it is difficult for the above-mentioned (meth)acrylate active species or propagating radicals to be added, and therefore the oxetane group does not participate in the copolymerization of the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b).

[0027] When the adhesive layer 10b is cured, it is preferable that the adhesive layer 10b is cured to a C-stage state (completely cured state).

[0028] In adhesive sheet 10 according to this embodiment, the adhesive may contain an epoxy resin as an additive. Hereinafter, the epoxy resin will be referred to as epoxy resin (d).

[0029] [Epoxy resin (d)] The epoxy resin (d) may be used to impart tackiness to the adhesive, i.e., the adhesive may contain the epoxy resin (d) as a tackifier. The epoxy resin (d) is preferably a liquid epoxy resin, since it can be easily mixed and dispersed in the adhesive at room temperature (23±2° C.) Here, a liquid epoxy resin means an epoxy resin that remains in a liquid state at room temperature.

[0030] Examples of the epoxy resin (d) include bisphenol A type epoxy resin and bisphenol F type epoxy resin. The epoxy resin (d) is preferably a bisphenol A type epoxy resin, and among the bisphenol A type epoxy resins, a liquid bisphenol A type epoxy resin is more preferred. Commercially available liquid bisphenol A epoxy resins include, for example, "JER (registered trademark) 825," "JER (registered trademark) 827," "JER (registered trademark) 828," "JER (registered trademark) 828EL," "JER (registered trademark) 828US," and "JER828XA," all manufactured by Mitsubishi Chemical Corporation. The epoxy resin (d) may be used alone or in combination of two or more.

[0031] The epoxy equivalent of the epoxy resin (d) may be 150 g / eq or more, 160 g / eq or more, or 170 g / eq or more. Such epoxy equivalent weight may be 220 g / eq or less, 210 g / eq or less, 200 g / eq or less, 190 g / eq or less, or 180 g / eq or less. The epoxy equivalent is a value determined according to JIS K 7236.

[0032] The adhesive preferably contains 3 parts by mass or more of the epoxy resin (d) per 100 parts by mass of the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) combined, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more. Furthermore, the adhesive preferably contains 30 parts by mass or less of the epoxy resin (d) per 100 parts by mass of the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b) combined, more preferably 25 parts by mass or less, even more preferably 22 parts by mass or less, and particularly preferably 20 parts by mass or less. When the adhesive contains the epoxy resin (d) in the above range, the adhesive can exhibit good tackiness.

[0033] The inventors speculate as follows as to why the adhesive layer 10b of the adhesive sheet 10 according to this embodiment exhibits sufficient initial adhesion and good hot water resistance even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell.

[0034] As described above, the adhesive layer 10b of the adhesive sheet 10 according to this embodiment is formed from the adhesive, which contains an oxetane group-containing (meth)acrylate (a), a polycarbonate-based urethane (meth)acrylate (b), and a photopolymerization initiator (c). As described above, after the adhesive layer 10b is cured, a copolymer is formed in the adhesive layer 10b by copolymerization of the oxetane group-containing (meth)acrylate (a) and the polycarbonate-based urethane (meth)acrylate (b). The polycarbonate-based urethane (meth)acrylate (b) has a urethane bond, and therefore the copolymer has elasticity derived from the urethane bond, allowing the adhesive to conform sufficiently to the adherend. Furthermore, the polycarbonate-based urethane (meth)acrylate (b) has a carbonate bond, which provides good heat resistance. Therefore, the copolymer has high heat resistance due to the carbonate bond. Therefore, the adhesive can exhibit sufficient durability even when exposed to high-temperature steam (e.g., steam at 95°C). Furthermore, as described above, the oxetane group of the oxetane group-containing (meth)acrylate (a) is not used to form the copolymer, and therefore exists in a state where the ring structure is maintained. The oxetane group has a four-membered ring structure, and therefore has high strain energy, making it easy for interaction to occur with cationic species. Here, the solid electrolyte membrane of a polymer electrolyte fuel cell is made of a fluororesin such as a perfluorocarbon sulfonic acid resin as described below, and since such a fluororesin may have sulfonic acid groups, hydrogen ions as cations are present around the sulfonic acid groups. Therefore, it is believed that an interaction occurs between the oxetane groups and the hydrogen ions as cations, and the copolymer is firmly adhered to the solid electrolyte membrane as an adherend. From the above, it is believed that the adhesive layer 10b of the adhesive sheet 10 according to this embodiment can exhibit sufficient initial adhesion and good hot water resistance even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell.

[0035] The base layer 10a may be, for example, a resin film or a fiber sheet.

[0036] Examples of the resin film include a film made of a non-crystalline resin having a softening point equal to or higher than the softening point of the adhesive, and a film made of a crystalline resin having a melting point equal to or higher than the softening point of the adhesive. Examples of the resin film include a polyethylene terephthalate resin film and a polyethylene naphthalate film. The resin film may be subjected to a physical surface treatment such as matte finish or hairline finish, or may be subjected to a surface treatment such as plasma treatment or primer treatment. By subjecting the base material layer 10a to the above-described surface treatment, the adhesiveness to the adhesive layer 10b can be improved.

[0037] The fiber sheet may be, for example, a nonwoven fabric or a woven fabric made of organic or inorganic fibers. When a nonwoven fabric is used as the fiber sheet, the nonwoven fabric may be formed by a dry method such as a carding method or an airlaid method, a wet method, a spunbond method, a thermal bond method, a chemical bond method, a needle punch method, a spunlace method (a hydroentanglement method), or a stitchbond method. When a woven fabric is used as the fiber sheet, the woven fabric may be formed by a plain weave, a twill weave, a satin weave, or the like.

[0038] Examples of the organic fibers include synthetic resin fibers, semi-synthetic fibers, regenerated fibers, and natural organic fibers. Examples of the synthetic fibers include fibers made of polyolefin resins such as polyethylene resin, polypropylene resin, and cycloolefin polymer; polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin; polyamide resins such as aliphatic polyamide resin and aromatic polyamide resin; polyether sulfide resin; polyphenylene sulfide resin; polyether ether ketone resin; polyimide resin; and fluororesin. Examples of the regenerated fibers include rayon and acetate. Examples of the natural organic fibers include pulp, cotton, hemp, and silk. Examples of the inorganic fibers include rock wool, glass wool, carbon fiber, boron fiber, alumina fiber, and metal fiber. The above-mentioned various fibers may be used singly or in combination of two or more. The various fibers may be used in the form of monofilaments or multifilaments.

[0039] Next, with reference to FIG. 2, an example in which the adherend of the adhesive layer 10b of the adhesive sheet 10 according to this embodiment is a membrane electrode assembly (MEA) 20 of a polymer electrolyte fuel cell will be further described.

[0040] The membrane electrode assembly (MEA) 20, which is the substrate, is configured to allow hydrogen gas to pass from the negative electrode side to the positive electrode side, and to generate electricity by reacting the hydrogen with oxygen supplied to the positive electrode side.

[0041] As shown in FIG. 2, in a membrane electrode assembly (MEA) 20, a positive electrode 202 and a negative electrode 203 are laminated on both sides of a solid electrolyte membrane 201, respectively. The positive electrode 202 includes a positive electrode catalyst layer 202a and a positive electrode gas diffusion layer 202b laminated on the positive electrode catalyst layer 202a. The positive electrode catalyst layer 202a is laminated on one surface of the solid electrolyte membrane 201. The negative electrode 203 includes a negative electrode catalyst layer 203a and a negative electrode gas diffusion layer 203b laminated on the negative electrode catalyst layer 203a. The negative electrode catalyst layer 203a is laminated on the other surface of the solid electrolyte membrane 201.

[0042] As shown in FIG. 2, the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a are formed so as to have smaller planar dimensions than the solid electrolyte membrane 201, and the positive electrode gas diffusion layer 202b and the negative electrode gas diffusion layer 203b are formed so as to have smaller planar dimensions than the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a. That is, in the membrane electrode assembly (MEA), the planar dimensions of the positive electrode 202 and the negative electrode 203 are smaller than the planar dimensions of the solid electrolyte membrane 201. As described above, since the planar dimensions of the positive electrode 202 are smaller than the planar dimensions of the solid electrolyte membrane 201, the solid electrolyte membrane 201 protrudes outward beyond the edge of the positive electrode catalyst layer 202a on the positive electrode side (one surface side) of the membrane electrode assembly (MEA) 20. As a result, a positive electrode-side electrolyte membrane exposed region 201a, where the surface is exposed, is formed on the outer periphery of the solid electrolyte membrane 201. Similarly, on the negative electrode side (the other surface side) of the membrane electrode assembly (MEA) 20, the solid electrolyte membrane 201 protrudes outward beyond the edge of the negative electrode catalyst layer 203a, and an negative electrode side electrolyte membrane exposed region 201b where the surface is exposed is formed on the outer periphery of the solid electrolyte membrane 201.

[0043] Furthermore, on the positive electrode side of the membrane electrode assembly (MEA) 20, the positive electrode catalyst layer 202a protrudes outward beyond the edge of the positive electrode gas diffusion layer 202b, thereby forming a positive electrode-side catalyst layer exposed region 202a1 where the surface is exposed on the outer periphery of the positive electrode catalyst layer 202a. The positive electrode catalyst layer exposed region 202a1 is located inside the positive electrode electrolyte membrane exposed region 201a and outside the edge of the positive electrode gas diffusion layer 202b. In this embodiment, the positive electrode side electrolyte membrane exposed region 201a is formed in an annular shape so as to surround the outer periphery of the membrane electrode assembly (MEA) 20. The positive electrode-side catalyst layer exposed region 202a1 is formed in a ring shape that is smaller than the positive electrode-side electrolyte membrane exposed region 201a. That is, on the positive electrode side of the membrane electrode assembly (MEA), a second boundary line L2, which is the boundary line between the positive electrode side electrolyte membrane exposed region 201a and the positive electrode side catalyst layer exposed region 202a1, is located inside a first boundary line L1, which is the boundary line between the positive electrode side electrolyte membrane exposed region 201a and the positive electrode side catalyst layer exposed region 202a1.

[0044] On the negative electrode side of the membrane electrode assembly (MEA) 20, the negative electrode catalyst layer 203a protrudes outward beyond the edge of the negative electrode gas diffusion layer 203b, thereby forming a negative electrode-side catalyst layer exposed region 203a1 where the surface is exposed on the outer periphery of the negative electrode catalyst layer 203a. The negative electrode catalyst layer exposed region 203a1 is located inside the negative electrode electrolyte membrane exposed region 201b and outside the edge of the negative electrode gas diffusion layer 203b. In this embodiment, the negative electrode side electrolyte membrane exposed region 201b is formed in an annular shape so as to surround the outer periphery of the membrane electrode assembly (MEA) 20. The negative electrode catalyst layer exposed region 203a1 is formed in a ring shape that is smaller than the negative electrode electrolyte membrane exposed region 201b. That is, on the negative electrode side of the membrane electrode assembly (MEA) 20, a fourth boundary line L4, which is the boundary line between the negative electrode side electrolyte membrane exposed region 201b and the negative electrode side catalyst layer exposed region 203a1, is located inside a third boundary line L3, which is the boundary line between the negative electrode side electrolyte membrane exposed region 201b and the negative electrode side catalyst layer exposed region 203a1.

[0045] 2, two adhesive sheets 10 are used as subgasket materials for a polymer electrolyte fuel cell. One adhesive sheet 10, a first adhesive sheet 10, is adhered to the positive electrode side of a membrane electrode assembly (MEA) 20, and the other adhesive sheet 10, a second adhesive sheet 10, is adhered to the negative electrode side of the membrane electrode assembly (MEA) 20.

[0046] When the annular first adhesive sheet 10 is overlaid on the membrane electrode assembly (MEA) 20, the outer peripheral edge of the first adhesive sheet 10 is positioned outside the outer peripheral edge of the membrane electrode assembly (MEA) 20. In addition, the inner peripheral edge of the first adhesive sheet 10 is positioned so as to fit within the positive electrode-side catalyst layer exposed region 202a1 and the negative electrode-side catalyst layer exposed region 203a1. That is, the size of the hollow portion of first adhesive sheet 10 is slightly larger than positive electrode gas diffusion layer 202b.

[0047] The second adhesive sheet 10 has the same shape as the first adhesive sheet 10.

[0048] In this embodiment, the first adhesive sheet 10 and the second adhesive sheet 10 are used as the subgasket material by directly adhering the adhesive layer 10b to the outer periphery of the membrane electrode assembly (MEA) 20.

[0049] 2, the outer periphery of the adhesive layer 10b of the first adhesive sheet 10 and the outer periphery of the adhesive layer 10b of the second adhesive sheet 10 are in direct contact with each other and bonded to each other. Furthermore, on one side of the membrane electrode assembly (MEA) 20, the inner periphery of the adhesive layer 10b of the first adhesive sheet 10 is bonded to the outer periphery of the membrane electrode assembly (MEA) 20. The inner periphery of the adhesive layer 10b is bonded to the outer periphery of the membrane electrode assembly (MEA) 20 so as to cover the entire positive electrode-side electrolyte membrane exposed region 201a, the first boundary line L1, and part of the positive electrode-side catalyst layer exposed region 202a1. Similarly, on the other surface side of the membrane electrode assembly (MEA) 20 , the inner periphery of the second adhesive sheet 10 is adhered to the outer periphery of the membrane electrode assembly (MEA) 20 .

[0050] As described above, the adhesive sheet 10 is adhered (covered) to the membrane electrode assembly (MEA) 20, so that a portion of the positive electrode gas can permeate through the positive electrode-side electrolyte membrane exposed region 201a and a portion of the negative electrode gas can permeate through the negative electrode-side electrolyte membrane exposed region 201b, thereby preventing a decrease in the performance of the solid polymer fuel cell.

[0051] As described above, in a polymer electrolyte fuel cell, hydrogen and oxygen react in the membrane electrode assembly (MEA) 20 to generate electricity. When hydrogen and oxygen react, the membrane electrode assembly (MEA) 20 reaches a relatively high temperature (e.g., 95°C). When the polymer electrolyte fuel cell is installed as a power source in an automobile, the central portion of the membrane electrode assembly (MEA) 20 is cooled by circulating antifreeze contained in a radiator through a pipe. However, the pipe is usually not extended to the periphery of the membrane electrode assembly (MEA) 20. Therefore, the temperature of the periphery of the membrane electrode assembly (MEA) 20 does not decrease and can continue to maintain a high temperature.

[0052] Here, since the adhesive layer 10b of the adhesive sheet 10 according to this embodiment is configured as described above, it can exhibit good hot water resistance. More specifically, it can exhibit good hot water resistance for a long period of time, such as 250 hours or more. Therefore, when the adhesive sheet according to this embodiment is used as a subgasket material in a polymer electrolyte fuel cell mounted on an automobile, as described above, even if the adhesive layer 10b comes into contact with water at a high temperature of 95° C., it can maintain adhesion to the solid electrolyte membrane 201 for a long period of time (250 hours or more). In addition, the adhesive sheet according to this embodiment has good initial adhesion to the solid electrolyte membrane 201. As will be described later, the solid electrolyte membrane 201 is usually made of a fluororesin such as perfluorocarbon sulfonic acid.

[0053] In the membrane electrode assembly (MEA) 20, the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a are generally formed using a catalyst ink composition containing a catalyst support material such as a carbon material supporting a catalyst, a proton-conductive polymer, and a solvent.

[0054] The solid electrolyte membrane 201 of the membrane electrode assembly (MEA) 20 is made of, for example, a fluororesin such as perfluorocarbon sulfonic acid resin. Examples of the perfluorocarbon sulfonic acid resin include "Nafion" (trade name) manufactured by DuPont, "Flemion" (trade name) manufactured by Asahi Kasei Corporation, and "Aciplex" (trade name) manufactured by Asahi Glass Co., Ltd. The perfluorocarbon sulfonic acid resin is, for example, a resin having a molecular structure represented by the following formula (1). Regarding m, n, and x in the following formula (1), for example, in the "Nafion", m≧1, n=2, x=5 to 13.5; in the "Aciplex", m=0, 1, n=2 to 5, x=1.5 to 14; and in the "Flemion", m=0, 1, n=1 to 5.

[0055] [ka]

[0056] The positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a contain, for example, catalyst particles, such as platinum, contained in the positive electrode catalyst layer 202a. The catalyst particles contained in the anode catalyst layer 203a include, for example, platinum compounds, such as alloys of platinum with at least one metal selected from the group consisting of ruthenium, palladium, nickel, molybdenum, iridium, and iron.

[0057] The positive electrode gas diffusion layer 202b and the negative electrode gas diffusion layer 203b are porous conductive substrate layers, etc. Examples of porous conductive substrate layers include carbon paper and carbon cloth.

[0058] The adhesive sheet 10 according to this embodiment can also be used in redox flow batteries. The adhesive sheet used in redox flow batteries is used to prevent permeation of the electrolyte.

[0059] The matters disclosed by this specification include the following.

[0060] (1) a base layer; and an adhesive layer formed of an adhesive and overlapping at least one surface of the base layer; The adhesive contains a (meth)acrylate having an oxetane group, a polycarbonate-based urethane (meth)acrylate, and a photopolymerization initiator. Adhesive sheet.

[0061] With this configuration, the adhesive layer of the adhesive sheet has sufficient initial adhesion even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell, and also has good hot water resistance.

[0062] (2) the ratio of the oxetane group to the total amount of (meth)acryloyl groups contained in the adhesive is 20% or more in terms of molar ratio; The adhesive sheet according to (1) above.

[0063] With this configuration, the adhesive layer of the adhesive sheet has sufficient initial adhesion even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell, and also has better hot water resistance.

[0064] (3) The adhesive further comprises an epoxy resin. The adhesive sheet according to (1) or (2) above.

[0065] With this configuration, the adhesive layer of the adhesive sheet has sufficient initial adhesion even when the adherend is a solid electrolyte membrane of a polymer electrolyte fuel cell, and also has better hot water resistance.

[0066] (4) It is used by adhering it to the solid electrolyte membrane of a polymer electrolyte fuel cell. The adhesive sheet according to any one of (1) to (3) above.

[0067] The adhesive sheet according to the present invention is not limited to the above-described embodiment. Furthermore, the adhesive sheet according to the present invention is not limited by the above-described effects. The adhesive sheet according to the present invention can be modified in various ways without departing from the spirit and scope of the present invention. [Example]

[0068] <Raw materials for adhesive layer composition> (Meth)acrylate ·Oxetane group-containing acrylate (Product name "OXE-10" manufactured by Osaka Organic Chemical Industry Co., Ltd.) Compound name: (3-ethyloxetan-3-yl)methyl acrylate Cyclic trimethylolpropane formal acrylate (Product name: Viscoat #200, manufactured by Osaka Organic Chemical Industry Co., Ltd.) Benzyl acrylate (Product name: Viscoat #160, manufactured by Osaka Organic Chemical Industry Co., Ltd.) Isobornyl acrylate monomer (Product name "IBXA" manufactured by Osaka Organic Chemical Industry Co., Ltd.) ·First polycarbonate-based urethane acrylate, bifunctional type (Product name "UF-8001G" manufactured by Kyoeisha Chemical Co., Ltd.) Mass average molecular weight: approx. 4500, glass transition temperature Tg: 56°C Secondary polycarbonate-based urethane (meth)acrylate, bifunctional type (Product name: UF-A7-52, manufactured by Kyoeisha Chemical Co., Ltd.) Transparent liquid, viscosity 13,000mPa·s (60℃) 1st Polyester Urethane (Meth)acrylate (Product name "UF3123M" manufactured by Kyoeisha Chemical Co., Ltd.) Secondary polyester urethane (meth)acrylate (Product name "UA288L" manufactured by Kyoeisha Chemical Co., Ltd.) Photopolymerization initiator First photoinitiator (trade name "Omnirad EDB" manufactured by IGM Resins) Second photoinitiator (IGM Resins product name "Omnirad BMS") Third photoinitiator (IGM Resins' product name "Omnirad DETX") additives Tackifier (bisphenol A epoxy resin) Mitsubishi Chemical Corporation product name: JER (registered trademark) 828

[0069] (Examples 1 to 5, Comparative Example 1) Each adhesive layer composition was prepared by mixing a (meth)acrylate, a photopolymerization initiator, and the like according to the formulation shown in Table 1. No organic solvent was used when mixing the components. In Table 1, the molar ratio R of the oxetane group in the oxetane group-containing acrylate (a) to the total amount of (meth)acryloyl groups is shown for each example and comparative example. M Also shown.

[0070] [Table 1]

[0071] [Preparation of adhesive sheet] The adhesive layer composition of each example was coated onto the entire surface of one side of a PEN film (length: 210 mm, width: 150 mm, thickness: 100 μm, Teonex: manufactured by Toyobo Film Solutions Co., Ltd.) serving as a base layer, to form an adhesive layer (hot-melt adhesive layer) on the PEN film. Next, the adhesive layer was irradiated with ultraviolet light using an ultraviolet irradiator to obtain an adhesive sheet according to each example. The coating was carried out so that the adhesive layer had a thickness of 20 μm to 30 μm after ultraviolet irradiation.

[0072] [Preparation of test samples for performance evaluation] The adhesive sheet of each example was superimposed on the perfluorocarbon sulfonic acid resin sheet so that the exposed surface of the adhesive layer of the adhesive sheet of each example was in contact with one surface of the perfluorocarbon sulfonic acid resin sheet. Using a laminator adjusted to a temperature of 140°C, the PEN film with the adhesive layer of each example and a perfluorocarbon sulfonic acid resin sheet were bonded together by thermocompression bonding to prepare test samples for performance evaluation. Details of Perfluorocarbon Sulfonic Acid Resin Sheet (Tetrafluoroethylene / perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether] copolymer film) Same shape as the PEN film used as the base layer (DuPont, product name "NAFIONN-115")

[0073] <Initial adhesion> A test piece measuring 10 mm wide x 80 mm long was cut out from the performance evaluation test sample of each example, and the peel strength of the test piece was then measured. The peel strength was measured by leaving the test specimen in an environment of 23°C and 50% RH for 24 hours, and then performing a 180° peel test at a pulling speed of 50 mm / min using a tensile tester. In the 180-degree peel test, the average value of the tensile stress in the peel section from 5 mm to 40 mm after the start of the test was calculated, and this was taken as the peel strength of the sample. The peel strength was determined by performing the 180-degree peel test three times and arithmetically averaging the results. The results are shown in Table 2 as the initial peel strength.

[0074] <Adhesion after immersion in hot water for 250 hours> A test specimen measuring 10 mm wide x 80 mm long was cut out from each performance evaluation test sample, and the test specimen was immersed in hot water at 95°C for 250 hours, after which the peel strength was measured in the same manner as above. The results are shown in Table 2. Table 2 also shows the peel strength retention rate after 250 hours of immersion (95° C. hot water) relative to the initial peel strength.

[0075] [Table 2]

[0076] Table 2 shows that the adhesive layer of the adhesive sheet according to each example exhibits high initial peel strength and also high peel strength retention. [Explanation of symbols]

[0077] 10 adhesive sheet, 20 membrane / electrode assembly (MEA), 201 solid electrolyte membrane, 202 positive electrode, 203 negative electrode, 10a substrate layer, 10b adhesive layer, 201a positive electrode side electrolyte membrane exposed region, 201b negative electrode side electrolyte membrane exposed region, 202a positive electrode catalyst layer, 202b positive electrode gas diffusion layer, 203a negative electrode catalyst layer, 203b negative electrode gas diffusion layer, 202a1 positive electrode side catalyst layer exposed region, 203a1 negative electrode side catalyst layer exposed region, L1 1st boundary line, L2 2nd boundary line, L3 3rd boundary line, L4 4th boundary line.

Claims

1. a base layer; and an adhesive layer formed of an adhesive and overlapping at least one surface of the base layer; The adhesive contains a (meth)acrylate having an oxetane group, a polycarbonate-based urethane (meth)acrylate, and a photopolymerization initiator. Adhesive sheet.

2. the ratio of the oxetane group to the total amount of (meth)acryloyl groups contained in the adhesive is 20% or more in terms of molar ratio; The adhesive sheet according to claim 1 .

3. The adhesive further comprises an epoxy resin. The adhesive sheet according to claim 1 or 2.

4. It is used by adhering it to the solid electrolyte membrane of a polymer electrolyte fuel cell. The adhesive sheet according to claim 1 or 2.

Images