Method for producing laminated steel sheet, and adhesive composition

Abstract

The present invention provides: a method that enables more efficient production of a laminated steel sheet; and an adhesive composition for an adhesive that can be used in said method and has high preservation stability.　This method is for producing a laminated steel sheet formed by laminating a prescribed number of thin steel sheets formed by punching a prescribed shape out from a band-shaped thin steel sheet. The method includes the following steps 1–4.　Step 1 is for forming the thin steel sheets in the prescribed shape by punching; step 2 is for applying an adhesive composition to prescribed sites on the thin steel sheets from step 1; step 3 is for layering the thin steel sheets from step 2; and step 4 is for irradiating a layered body of a prescribed number of sheets with an energy beam. The adhesive composition contains the following constituents (A) to (C).　Constituent (A) is a compound with at least one (meth)acryloyl group in one molecule; constituent (B) is a thermal radical initiator; constituent (C) is a photoinitiator; and constituent (D) is an anaerobically curing catalyst.

Description

Manufacturing method for laminated steel sheet and adhesive composition

[0001] The present invention relates to a method for producing a laminated steel sheet and an adhesive composition.

[0002] A known method for manufacturing laminated steel sheets is an adhesive method in which an adhesive is applied between laminated steel sheets to form a laminate (see JP 2001-321850 A). Epoxy resin, acrylic resin, or the like is used in the adhesive method, and heat curing or anaerobic curing is generally used. However, heat curing and anaerobic curing require a long time for curing, which reduces the production efficiency of laminated steel sheets and poses a risk of peeling between the thin steel sheets after production.

[0003] To solve the above problems, there is a method to improve the curing property by using an adhesive and a primer, but this method has the problem that the adhesive hardens before spreading during lamination and pressure bonding, making the thickness of the adhesive layer unstable and reducing the adhesive strength. Furthermore, if the adhesive itself is cured quickly, its storage stability decreases and gelation occurs in the application equipment before it is applied to the laminated steel sheets, significantly reducing the equipment operating rate.

[0004] As a result of extensive research to achieve the above object, the present inventors have discovered a method for more efficiently producing laminated steel sheets and an adhesive composition that can be used in that method and has high storage stability.

[0005] The gist of the present invention is as follows: [1] A method for producing a laminated steel sheet by laminating a predetermined number of steel sheets formed by punching a strip-shaped thin steel sheet into a predetermined shape, the method comprising the following steps 1 to 4: step 1: punching the steel sheets into the predetermined shape; step 2: applying an adhesive composition to predetermined positions of the steel sheets of step 1; step 3: laminating the steel sheets of step 2 to produce a laminate; and step 4: irradiating the laminate of step 3 with energy rays, wherein the adhesive composition comprises components (A) to (C): component (A): a compound having one or more (meth)acryloyl groups in one molecule; component (B): a thermal radical initiator; component (C): a photoinitiator; and component (D): an anaerobic curing catalyst. [2] The method for producing a laminated steel sheet according to [1], wherein the component (C) comprises (C-1) a photoinitiator having a maximum absorption wavelength of less than 350 nm and (C-2) a photoinitiator having a maximum absorption wavelength of 350 nm or more. [3] The method for producing a laminated steel sheet according to [1] or [2], wherein the adhesive composition further comprises a stabilizer as component (E). [4] The method for producing a laminated steel sheet according to [3], wherein the component (E) is at least one compound selected from the group consisting of 2,6-di-t-butyl-p-cresol, hydroquinone, and 4-methoxyphenol. [5] The method for producing a laminated steel sheet according to any one of [1] to [4], wherein the amount of the component (C) blended is 0.1 to 10 parts by mass per 100 parts by mass of the component (A). [6] The method for producing a laminated steel sheet according to any one of [1] to [5], wherein the mass ratio of the component (B) to the component (C) is 10:90 to 90:10. [7] The method for producing a laminated steel sheet according to any one of [1] to [6], wherein the component (D) contains an azole compound and / or a mercaptan compound. [8] The method for producing a laminated steel sheet according to any one of [1] to [7], comprising a step of applying a hardening accelerator between the step 1 and the step 2 and / or between the step 2 and the step 3. [9] A laminated steel sheet produced by the method for producing a laminated steel sheet according to any one of [1] to [8].

[10] A production apparatus for carrying out the method for producing a laminated steel sheet according to any one of [1] to [8].

[11] An adhesive composition comprising the following components (A) to (D), used in a method for producing a laminated steel sheet by laminating a predetermined number of thin steel sheets that have been punched into a predetermined shape from a strip-shaped thin steel sheet, the method comprising the following steps 1 to 4: step 1: punching the thin steel sheets into a predetermined shape; step 2: applying the adhesive composition to predetermined positions of the thin steel sheets of step 1; step 3: laminating the thin steel sheets of step 2 to produce a laminate; and step 4: irradiating the laminate of step 3 with energy rays, component (A): a compound having one or more (meth)acryloyl groups in one molecule; component (B): a thermal radical initiator; component (C): a photoinitiator; and component (D): an anaerobic curing catalyst.

[0006] The present invention provides a method for more efficiently producing laminated steel sheets and an adhesive composition with high storage stability that can be used in the method.

[0007] 1 is a schematic diagram of a manufacturing apparatus for laminated steel sheets according to an embodiment of the present invention.

[0008] The present invention will be described in detail below. One aspect of the present invention is a method for manufacturing a laminated steel sheet by stacking a predetermined number of steel sheets that have been punched into a predetermined shape from a strip-shaped thin steel sheet, and the manufacturing method includes the following steps 1 to 4. The manufacturing apparatus for laminated steel sheet and the manufacturing method for laminated steel sheet using the same will be described below along the manufacturing process: Step 1: punching the steel sheets into a predetermined shape; Step 2: applying an adhesive composition to predetermined locations of the steel sheets of Step 1; Step 3: stacking the steel sheets of Step 2 to obtain a laminate; and Step 4: irradiating the laminate of Step 3 with energy rays.

[0009] In the present invention, the thin steel sheets are irradiated with energy rays after lamination to harden them, and the inner part not exposed to the energy rays is cured anaerobically, thereby achieving a stable hardened state in a short time, thereby enabling stable production of laminated steel sheets. The energy rays referred to in the present invention include all light in a broad sense, such as radiation such as α rays and β rays, electromagnetic waves such as γ rays and X-rays, electron beams, ultraviolet rays with a wavelength of about 100 to 400 nm, and visible light with a wavelength of about 400 to 800 nm, and preferably ultraviolet rays.

[0010] The present invention can be used in a laminated steel sheet manufacturing apparatus as shown in Fig. 1, but is not limited to this. In the laminated steel sheet manufacturing apparatus 100 of Fig. 1, in step 1, a strip-shaped thin steel sheet 2 is fed from a roll device 1 toward a die device 4. Next, a process oil application device 3 applies processing oil to the strip-shaped thin steel sheet 2, and then, in the die device 4, the strip-shaped thin steel sheet 2 to which the processing oil has been applied is punched into a predetermined shape by a punch unit 5. Thereafter, in step 2, an adhesive composition is applied to the punched thin steel sheets, and in step 3, thin steel sheets are laminated to obtain a laminated steel sheet 9. Next, in step 4, the laminated steel sheet 9 is irradiated with energy rays under arbitrary conditions to cure the adhesive composition.

[0011] In the laminated steel sheet manufacturing apparatus 100 shown in FIG. 1 , the punch unit 5 is attached to the upper side of the die device 4, directly above the conveying path of the steel strip 2, and is positioned so that the steel strip 2 can be punched out by punching. The punch unit 5 that can be used in the present invention is a die for sequentially punching the steel strip 2 into a predetermined shape. Depending on the purpose, one type of punch unit 5 may be used, or two or more types may be combined. It is preferable to have multiple punch units 5 to improve punching accuracy. While the steel strip 2 is intermittently conveyed through the die device 4, the steel sheet is sequentially subjected to, for example, punching pilot holes, punching inner diameter pilot holes and small holes for outer grooves, punching slots, punching the inner diameter, and punching inner diameter teeth. From the viewpoint of punching workability, the thickness of the steel strip 2 is preferably in the range of 0.05 to 5.0 mm, more preferably 0.1 to 3.0 mm. Finally, as the outer shape punching punch portion 8 punches out the steel sheets, a stack of thin steel sheets is gradually formed within the punching hole 10, and the stack itself descends within the punching hole 10, eventually dropping to produce a laminated steel sheet 9.

[0012] In the laminated steel sheet manufacturing apparatus 100 shown in Figure 1, the processing oil application device 3 is provided in the middle of the feed path (transport path) of the steel strip 2 upstream of the die device 4, and is arranged so that processing oil can be applied to the upper surface side of the steel strip 2 (the surface side that comes into contact with the punch section 5 during punching). However, the processing oil application device 3 only needs to be provided upstream of the punch section 5, and may also be provided within the die device 4. The processing oil application device 3 that can be used in the present invention is only required to be able to apply processing oil to the upper surface side of the steel strip 2. The application method is not particularly limited, and examples thereof include roller, dispensing, spray, inkjet, and dipping.

[0013] The processing oil that can be used in the present invention is used as a punching oil for the purpose of preventing galling, seizure, etc. The oil components are not particularly limited, but examples include those primarily composed of mineral oil and / or synthetic oil. Specifically, the oil comprises a base oil made of mineral oil (e.g., diesel oil) and / or synthetic oil, and additives such as extreme-pressure additives, rust inhibitors, and preservatives. For example, extreme-pressure additives are compounds containing sulfur, phosphorus, etc., which react with metals due to heat generation under extreme pressure conditions to form a film of soft metal compounds at the friction interface. This film is interposed between the punch portion 5 and the thin steel sheet (the strip-shaped thin steel sheet 2), thereby preventing galling, seizure, etc.

[0014] In the laminated steel sheet manufacturing apparatus 100 shown in FIG. 1 , the adhesive applicator 6 is attached to the lower side of the die device 4, downstream of the punch unit 5. The applicator (tip) of the curable composition applicator 6 is located directly below the conveyance path of the steel strip 2 so as to be able to apply the adhesive composition to a predetermined location on the underside of the steel strip 2 (the backside that is not contacted by the punch unit 5 during punching). The adhesive applicator 6 that can be used in the present invention is only required to be able to supply the adhesive composition from the adhesive supply device 7 and apply the adhesive composition to a predetermined location on the steel strip 2. Here, the predetermined location may be a specific region of the steel sheet or the entire area through which the steel strip 2 passes. The thickness of the adhesive composition applied in an uncured state is, for example, 0.01 to 100 μm. The application method is not particularly limited, and examples include roller application, dispensing, spraying, inkjet application, and dipping. In relation to the processing oil, it is preferable to apply the adhesive composition to the steel strip 2 from the side opposite to the die (punch portion 5) side (the back side that does not come into contact with the punch portion 5 during punching). The protruding portion of the adhesive composition after lamination can be removed by wiping off the uncured portion before curing with a rag or the like, or by grinding off the cured portion after curing with a file or the like.

[0015] The present invention may include a step of applying a curing accelerator between steps 1 and 2 and / or between steps 2 and 3. Including the step of applying a curing accelerator in the manufacturing method of the present invention can further improve the curability of the adhesive composition. The curing accelerator is used for the purpose of improving anaerobic curability. The curing accelerator component includes a metal complex. Examples of metal species of the metal complex include Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, and Ag. From the viewpoint of further accelerating the curing rate of the adhesive composition according to the present invention, the metal species of the metal complex preferably includes Cu. Specific examples of metal complexes include cobalt naphthenate, cobalt octoate, copper naphthenate, copper neodecanoate, copper 2-ethylhexanoate, and vanadyl acetylacetonate. From the viewpoint of further accelerating the curing rate of the adhesive composition according to the present invention, the metal complex is preferably selected from the group consisting of copper naphthenate, copper neodecanoate, and copper 2-ethylhexanoate.

[0016] In the laminate of step 3, before the adhesive composition is irradiated with energy rays, it is preferable to fix the laminated steel sheets with a fixing jig 11. Use of the fixing jig can improve productivity.

[0017] Regarding the step (step 4) of irradiating the laminate with energy rays in step 3, in the laminated steel sheet manufacturing apparatus 100 shown in FIG. 1 , the irradiator 12 is installed outside the mold device 4. The irradiator 12 that can be used in the present invention is only required to be able to irradiate energy rays such as ultraviolet rays or visible light. The energy rays have the effect of activating and curing the adhesive composition described below. A high-pressure mercury lamp, LED, etc. can be used as the light source for the irradiator 12 that irradiates the energy rays. The adhesive composition according to the present invention has excellent energy ray curing properties, so it can be cured using an LED. The preferred cumulative light dose during energy ray irradiation is 1 to 100 kJ / m ２ The illuminance of an LED irradiation device that uses an LED as a light source is generally 30 to 900 mW / cm ２ and in some cases 20 to 300 mW / cm ２The irradiation time is 0.1 to 60 seconds. The cumulative amount of light is adjusted by adjusting the illuminance and irradiation time, and the time until curing can be adjusted by changing the cumulative amount of light.

[0018] In the present invention, it is necessary to use an adhesive composition that is suitable for the energy ray irradiation step in step 4. The adhesive composition in the present invention contains the following components (A) to (D): component (A): a compound having one or more (meth)acryloyl groups in one molecule; component (B): a thermal radical initiator; component (C): a photoinitiator; and component (D): an anaerobic curing catalyst.

[0019] In this specification, "X to Y" is used to mean that the numerical values ​​(X and Y) written before and after it are included as the lower and upper limits, respectively, and means "at least X and at most Y." In the present invention, a compound having a (meth)acryloyl group refers to a (meth)acrylate. The (meth)acryloyl group may contain a (meth)acryloyl group in the form of a (meth)acryloyloxy group. The term "(meth)acryloyl" includes both acryloyl and methacryloyl. For example, the term "(meth)acryloyl group" refers to an acryloyl group (H ２ C=CH-C(=O)-) and methacryloyl groups (H ２ C=C(CH ３ )-C(=O)-). The term "(meth)acrylate" includes both acrylate and methacrylate, the term "(meth)acryl" includes both acryl and methacryl, and the term "(meth)acrylamide" includes both acrylamide and methacrylamide.

[0020] The component (A) according to the present invention is a compound having one or more (meth)acryloyl groups in one molecule. The component (A) is a major component constituting the adhesive composition according to the present invention. Examples of the component (A) include oligomers and monomers having one or more (meth)acryloyl groups in one molecule (excluding (meth)acryloyl monomers having a phosphate ester skeleton and (meth)acrylic-containing silane coupling agents, which are described below). Here, the term "oligomer" refers to a polymer in which two to several dozens of monomer units (including monomer units other than (meth)acrylate monomers) are repeated. Examples of oligomers having one or more (meth)acryloyl groups in one molecule according to the present invention include urethane-modified (meth)acrylates and epoxy-modified (meth)acrylates. From the viewpoints of curability and adhesive strength to laminated steel sheets, component (A) preferably contains a compound having two or more (meth)acryloyl groups, and more preferably contains one or more compounds having two or more (meth)acryloyl groups selected from the group consisting of urethane-modified (meth)acrylates, epoxy-modified (meth)acrylates, and (meth)acrylates having an aromatic ring.

[0021] A urethane-modified (meth)acrylate is a compound having a urethane bond in the main chain and a (meth)acryloyl group, which is formed by reacting an isocyanate group with a hydroxyl group. From the viewpoint of curability, the (meth)acryloyl group is preferably located at the end of the molecular chain. Examples of methods for producing a urethane-modified (meth)acrylate include a method of reacting a polyol compound having a hydroxyl group with a (meth)acrylate having an isocyanate group, and a method of reacting a polyol compound having a hydroxyl group, a polyisocyanate compound, and a (meth)acrylate having a hydroxyl group.

[0022] The polyol compound having a hydroxyl group is not particularly limited, but examples thereof include polyester polyols, polycarbonate polyols, and polyether polyols.

[0023] Examples of the (meth)acrylate having an isocyanate group include, but are not limited to, 2-methacryloyloxyethyl isocyanate, 2-isocyanatoethyl methacrylate, and 2-isocyanatoethyl acrylate.

[0024] Examples of the polyisocyanate compound include aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, tetramethylxylylene diisocyanate, diphenylmethane diisocyanate, naphthalene-1,5-disocyanate, and triphenylmethane triisocyanate; isophorone diisocyanate, bis(4-isopropyl methylisocyanate), and the like. alicyclic polyisocyanates such as 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, norbornane diisocyanate, and bicycloheptane triisocyanate; and linear or branched aliphatic polyisocyanates such as hexamethylene diisocyanate, 1,3,6-hexamethylene triisocyanate, and 1,6,11-undeca triisocyanate.

[0025] The (meth)acrylate having a hydroxyl group is not particularly limited, and examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 1,6-hexanediol mono(meth)acrylate, neopentyl glycol mono(meth)acrylate, (poly)ethylene glycol mono(meth)acrylate, (poly)propylene glycol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, etc. The (meth)acrylate having a hydroxyl group may be used alone or in combination of two or more.

[0026] Epoxy-modified (meth)acrylates are compounds that can be synthesized by ring-opening polymerization of acrylic acid or the like with the glycidyl group of a glycidyl ether compound. Synthesis of epoxy-modified (meth)acrylates is not limited to this method. The main chain of the glycidyl ether can be one of various skeletons, such as bisphenol A, bisphenol F, phenol novolac, hydrogenated bisphenol A, and hydrogenated bisphenol F. These may be used alone or in combination of two or more. Specific examples of epoxy-modified (meth)acrylates include bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, fatty acid-modified epoxy acrylate, amine-modified bisphenol epoxy acrylate, novolac epoxy acrylate, and epoxidized soybean oil acrylate.

[0027] Examples of the monomer having a (meth)acryloyl group include a monofunctional (meth)acrylate monomer having one (meth)acryloyl group in one molecule, and a polyfunctional (meth)acrylate monomer having two or more (meth)acryloyl groups in one molecule.

[0028] Examples of monofunctional (meth)acrylate monomers include methoxydiethylene glycol mono(meth)acrylate, methoxytriethylene glycol mono(meth)acrylate, methoxytetraethylene glycol mono(meth)acrylate, methoxypentaethylene glycol mono(meth)acrylate, methoxyhexaethylene glycol mono(meth)acrylate, methoxyheptaethylene glycol mono(meth)acrylate, methoxyhexaethylene glycol mono(meth)acrylate, methoxyoctaethylene glycol mono(meth)acrylate, methoxynonaethylene glycol mono(meth)acrylate, methoxydecaethylene glycol mono(meth)acrylate, methoxytripropylene glycol mono(meth)acrylate, methoxytetrapropylene glycol mono(meth)acrylate, methoxypentapropylene glycol mono(meth)acrylate, methoxyhexapropylene glycol mono(meth)acrylate, methoxyheptapropylene glycol mono(meth)acrylate, methoxyhectapropylene glycol mono(meth)acrylate, methacrylate, Octapropylene glycol mono(meth)acrylate, methoxynonapropylene glycol mono(meth)acrylate, methoxydecapropylene glycol mono(meth)acrylate, methoxytributylene glycol mono(meth)acrylate, methoxytetrabutylene glycol mono(meth)acrylate, methoxypentabtylene glycol mono(meth)acrylate, methoxyhexabtylene glycol mono(meth)acrylate, methoxyheptabtylene glycol mono(meth)acrylate, methoxyheptabtylene glycol Lithium mono(meth)acrylate, methoxyoctabutylene glycol mono(meth)acrylate, methoxynonabutylene glycol mono(meth)acrylate, methoxydecabutylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxytetraethylene glycol mono(meth)acrylate, ethoxypentaethylene glycol mono(meth)acrylate, ethoxyhexaethylene glycol mono(meth)acrylate,Ethoxyheptaethylene glycol mono(meth)acrylate, ethoxyhexaethylene glycol mono(meth)acrylate, ethoxyoctaethylene glycol mono(meth)acrylate, ethoxynonaethylene glycol mono(meth)acrylate, ethoxydecaethylene glycol mono(meth)acrylate, ethoxytripropylene glycol mono(meth)acrylate, ethoxytetrapropylene glycol mono(meth)acrylate, ethoxypentapropylene glycol mono(meth)acrylate, ethoxyhexapropylene glycol mono(meth)acrylate, ethoxyheptapropylene glycol mono(meth)acrylate, ethoxyhexapropylene glycol mono(meth)acrylate, ethoxyoctapropylene glycol mono(meth)acrylate, ethoxynonapropylene Examples of the monofunctional (meth)acrylate monomer include glycol mono(meth)acrylate, ethoxydecapropylene glycol mono(meth)acrylate, ethoxytributylene glycol mono(meth)acrylate, ethoxytetrabutylene glycol mono(meth)acrylate, ethoxypentabtylene glycol mono(meth)acrylate, ethoxyhexabtylene glycol mono(meth)acrylate, ethoxyheptabtylene glycol mono(meth)acrylate, ethoxyhexabtylene glycol mono(meth)acrylate, ethoxyoctabtylene glycol mono(meth)acrylate, ethoxynonabtylene glycol mono(meth)acrylate, ethoxydecabutylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. The monofunctional (meth)acrylate monomer may be used alone or in a mixture of two or more.

[0029] Examples of polyfunctional (meth)acrylate monomers include bifunctional (meth)acrylates such as ethoxylated bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, tricyclodecanol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and 2-hydroxy-3-methacrylpropyl acrylate. trifunctional (meth)acrylates such as acrylate and trimethylolpropane trimethacrylate; tetrafunctional (meth)acrylate monomers such as ditrimethylolpropane tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional (meth)acrylate monomers such as dipentaerythritol monohydroxypenta(meth)acrylate and alkyl-modified dipentaerythritol penta(meth)acrylate; and hexafunctional (meth)acrylate monomers such as dipentaerythritol hexa(meth)acrylate.

[0030] In one embodiment, the component (A) includes a urethane-modified (meth)acrylate, an epoxy-modified (meth)acrylate, and a monofunctional (meth)acrylate monomer, preferably a urethane-modified (meth)acrylate having two or more (meth)acryloyl groups, an epoxy-modified (meth)acrylate having two or more (meth)acryloyl groups, and two or more types of monofunctional (meth)acrylate monomers, and more preferably a urethane-modified (meth)acrylate oligomer having acryloyl groups at both ends, an epoxy-modified (meth)acrylate oligomer having acryloyl groups at both ends, and two types of monofunctional (meth)acrylate monomers (preferably having hydroxy groups).

[0031] The component (B) according to the present invention is a thermal radical initiator. The component (B) is a major component for anaerobic curing of the adhesive composition when used in combination with the component (D), which will be described later. The component (B) can be an organic peroxide. Examples of organic peroxides include hydroperoxides such as cumene hydroperoxide, t-butyl hydroperoxide, p-methane hydroperoxide, methyl ethyl ketone peroxide, cyclohexane peroxide, dicumyl peroxide, and diisopropylbenzene hydroperoxide, as well as ketone peroxides, diallyl peroxides, and peroxyesters. Among these, from the viewpoints of excellent anaerobic curing properties and storage stability of the adhesive, the component (B) is preferably a hydroperoxide, and more preferably cumene hydroperoxide.

[0032] From the viewpoint of anaerobic curability, the content of component (B) is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and most preferably 0.5 to 5 parts by mass, per 100 parts by mass of component (A). When the content of component (B) is 0.1 part by mass or more, sufficient curing can be achieved even in the interior where no energy rays are exposed, and when the content of component (B) is 20 parts by mass or less, there is no risk of the storage stability of the adhesive composition being reduced.

[0033] The component (C) according to the present invention is a photoinitiator. The component (C) is a main component for curing the adhesive composition with energy rays. When the adhesive composition contains the component (C), curing can be accelerated, thereby shortening the line tact time in the production of laminated steel sheets. Examples of the component (C) include photoradical initiators. Photoradical initiators are compounds that decompose upon irradiation with energy rays to generate radical species. Examples of the component (C) include acetophenone-based photoinitiators, benzoin-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, and acylphosphine oxide-based photoinitiators. The component (C) may be used alone or in combination of two or more types.

[0034] The acetophenone-based photoinitiator is not particularly limited, but examples thereof include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer.

[0035] The benzoin-based photoinitiator is not particularly limited, but examples thereof include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

[0036] The benzophenone-based photoinitiator is not particularly limited, but examples thereof include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, and (4-benzoylbenzyl)trimethylammonium chloride.

[0037] The thioxanthone photoinitiator is not particularly limited, but examples thereof include 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one mesochloride.

[0038] The acylphosphine oxide photoinitiator is not particularly limited, but examples thereof include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide.

[0039] In the production method according to the present invention, from the viewpoint of achieving better energy ray curability, the adhesive composition preferably contains, as component (C), (C-1) a photoinitiator having a maximum absorption wavelength of less than 350 nm and (C-2) a photoinitiator having a maximum absorption wavelength of 350 nm or more.

[0040] Examples of the component (C-1) include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal, etc. From the viewpoint of further improving curability when used in combination with the component (D), the component (C-1) is preferably 2-hydroxy-2-methyl-1-phenylpropan-1-one and / or 1-hydroxycyclohexyl phenyl ketone, and most preferably 1-hydroxycyclohexyl phenyl ketone.

[0041] Examples of the component (C-2) include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide.

[0042] The blending amount (content) of component (C) is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and most preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of component (A). When the blending amount (content) of component (C) is 0.1 part by mass or more, excellent energy ray curability can be imparted, and when the blending amount (content) of component (C) is 10 parts by mass or less, the storage stability of the adhesive composition can be maintained. The mass ratio of component (C-1) to component (C-2) (component (C-1):component (C-2)) is preferably 80:20 to 20:80, more preferably 30:70 to 70:30, and most preferably 40:60 to 60:40.

[0043] From the viewpoint of combining energy ray curability and anaerobic curability, the mass ratio of the component (B) to the component (C) (component (B):component (C)) is preferably 10:90 to 90:10, more preferably 15:85 to 85:15, and most preferably 20:80 to 50:50.

[0044] The component (D) according to the present invention is an anaerobic curing catalyst. By including the component (D) in the adhesive composition according to the present invention, the anaerobic curing properties allow for curing to the interior, which is not exposed to energy rays, and also accelerates curing by energy rays. The component (D) decomposes under anaerobic conditions where it is not exposed to oxygen, generating free radicals that accelerate curing. Examples of the component (D) include amine compounds, azole compounds, mercaptan compounds, hydrazine compounds, and derivatives thereof. The component (D) may be used alone or in combination of two or more types.

[0045] Examples of the amine compound include, but are not limited to, heterocyclic secondary amines such as 1,2,3,4-tetrahydroquinoline and 1,2,3,4-tetrahydroquinaldine; heterocyclic tertiary amines such as quinoline, methylquinoline, quinaldine and quinoxalinephenazine; and aromatic tertiary amines such as N,N-dimethyl-anisidine and N,N-dimethylaniline.

[0046] Examples of azole compounds include thiazole, isothiazole, thiadiazole, oxazole, isoxazole, oxadiazole, diazole, triazole, etc. More specific examples include, but are not limited to, saccharin, benzothiazole, sodium o-sulfobenzimidazole, 1,2,4-triazole, benzotriazole, hydroxybenzotriazole, benzoxazole, 1,2,3-benzothiadiazole, 3-mercaptobenzotriazole, etc.

[0047] Examples of the mercaptan compound include, but are not limited to, linear mercaptans such as n-dodecyl mercaptan, ethyl mercaptan, butyl mercaptan, and 1-dodecanethiol.

[0048] Examples of hydrazine compounds include, but are not limited to, 1-acetyl-2-phenylhydrazine, 1-acetyl-2(p-tolyl)hydrazine, 1-benzoyl-2-phenylhydrazine, 1-(1',1',1'-trifluoro)acetyl-2-phenylhydrazine, 1,5-diphenyl-carbohydrazine, 1-formyl-2-phenylhydrazine, 1-acetyl-2-(p-bromophenyl)hydrazine, 1-acetyl-2-(p-nitrophenyl)hydrazine, 1-acetyl-2-(2'-phenylethylhydrazine), ethyl carbazate, p-nitrophenylhydrazine, and p-trisulfonylhydrazide.

[0049] From the viewpoint of improving anaerobic curability and energy ray curability when used in combination with the component (C), the component (D) preferably contains an azole compound and / or a mercaptan compound, more preferably contains one or more compounds selected from the group consisting of saccharin, benzothiazole, sodium o-sulfobenzimidone, and 1-dodecanethiol, and most preferably contains saccharin, benzothiazole, sodium o-sulfobenzimidone, and 1-dodecanethiol.

[0050] From the viewpoint of improving anaerobic curability and energy ray curability, the content of component (D) is preferably 0.01 to 40 parts by mass, more preferably 0.5 to 30 parts by mass, and most preferably 1 to 25 parts by mass, relative to 100 parts by mass of component (A). When component (D) contains an azole compound, the azole compound is preferably contained in an amount of 50% by mass or more, more preferably 60% by mass or more, and most preferably 70% by mass or more, relative to the entire component (D). When an azole compound and a mercaptan compound are contained, the mass ratio of the azole compound to the mercaptan compound (azole compound:mercaptan compound) is preferably 50:50 to 90:10.

[0051] The adhesive composition according to the present invention preferably further contains a stabilizer as component (E). Examples of stabilizers include 2,6-di-t-butyl-p-cresol, hydroquinone, hydroquinone monomethyl ether, 4-t-butylcatechol, and 4-methoxyphenol. Component (E) may be used alone or in combination. From the viewpoint of storage stability of the adhesive composition, component (E) is preferably one or more compounds selected from the group consisting of 2,6-di-t-butyl-p-cresol, hydroquinone, and 4-methoxyphenol, more preferably 2,6-di-t-butyl-p-cresol and / or hydroquinone, and most preferably hydroquinone. From the viewpoint of improving storage stability without inhibiting curability, the content of component (E) is preferably 0.001 to 0.5% by mass, more preferably 0.01 to 0.3% by mass, and most preferably 0.05 to 0.15% by mass, based on the total adhesive composition.

[0052] The adhesive composition according to the present invention may further contain an appropriate amount of additives such as an adhesion promoter, a colorant, an inorganic filler, an organic filler, a photosensitizer, a polymerization inhibitor, or a chelating agent, provided that the adhesive composition does not impair its properties.

[0053] Examples of adhesion promoters include (meth)acryloyl monomers having a phosphate ester skeleton and silane coupling agents. In the present invention, (meth)acryloyl monomers having a phosphate ester skeleton have a (meth)acryloyl group, but are strongly influenced by the phosphate ester, so they are treated as adhesion promoters rather than as component (A). Specific examples of (meth)acryloyl monomers having a phosphate ester skeleton include, but are not limited to, 2-hydroxyethyl (meth)acrylate acid phosphate.

[0054] Examples of silane coupling agents include 3-acryloxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldipropyloxysilane, 3-glycidoxypropyldimethylmonomethoxysilane, 3-glycidoxypropyldimethylmonoethoxysilane, 3-glycidoxypropyldimethylmonopropyloxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethylsilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethylsilane. Glycidyl group-containing silane coupling agents such as methoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane; vinyl group-containing silane coupling agents such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylmethyldiethoxysilane; (meth)acrylic group-containing silane coupling agents such as propyldimethyl monomethoxysilane, 3-methacryloxypropyldimethyl monoethoxysilane, 3-acryloxypropylmethyl dipropyloxysilane, 3-acryloxypropylmethyl dimethoxysilane, 3-acryloxypropylmethyl diethoxysilane, 3-acryloxypropylmethyl dipropyloxysilane, 3-acryloxypropyldimethyl monopropyloxysilane, 3-acryloxypropyldimethyl monomethoxysilane, 3-acryloxypropyldimethyl monoethoxysilane, 3-acryloxypropyldimethyl monopropyloxysilane, and γ-methacryloxypropyltrimethoxysilane; amino group-containing silane coupling agents such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane. It should be noted that (meth)acrylic-containing silane coupling agents are not included in the component (A) of the present invention.

[0055] Examples of colorants include inorganic pigments such as carbon black, barium sulfate, alumina white, clay, and titanium oxide; organic pigments such as indanthrone blue, quinacridone red, dioxazine violet, and phthalocyanine blue; and ZnS:Ag, ZnS:Cu, ZnS:Mn, and SrAl. ２ O ４ : Eu, Sr ４ Al １４ O ２５ : Eu, Y ２ O ２ S: Eu, Y ２ O ３ Fluorescent inorganic pigments such as Eu, fluorescent organic pigments, dyes (e.g., dyes for coloring resins such as aminoketone fluorescent dyes), etc. The colorants may be used alone or in combination of two or more.

[0056] Examples of inorganic fillers include glass, silica, talc, alumina, mica, ceramics, silicone particles, calcium carbonate, aluminum nitride, carbon powder, kaolin clay, dried clay minerals, dried diatomaceous earth, etc. The inorganic fillers may be used alone or in combination of two or more.

[0057] The organic filler may be an organic powder composed of rubber, elastomer, plastic, polymer (or copolymer), etc. The organic filler may be used alone or in combination of two or more types. The organic filler may also be an organic filler having a multilayer structure such as a core-shell type. The average particle size of the organic filler is preferably in the range of 0.05 to 50 μm.

[0058] Examples of the chelating agent include ethylenediamine-N,N,N',N'-tetraacetic acid disodium salt dihydrate and ethylenediamine-N,N,N',N'-tetraacetic acid tetrasodium salt tetrahydrate.

[0059] In the production method according to the present invention, from the viewpoint of the storage stability of the adhesive composition, it is more preferable that the adhesive composition does not contain, as a component, a metal complex containing a metal species such as Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, or Ag that promotes anaerobic curing.

[0060] One aspect of the present invention is an adhesive composition comprising the following components (A) to (D) for use in a method for producing a laminated steel sheet by laminating a predetermined number of thin steel sheets which have been punched into a predetermined shape from a strip-shaped thin steel sheet, the method comprising the following steps 1 to 4: step 1: punching the thin steel sheets into a predetermined shape; step 2: applying the adhesive composition to predetermined locations of the thin steel sheets of step 1; step 3: laminating the thin steel sheets of step 2 to produce a laminate; and step 4: irradiating the laminate of step 3 with energy rays, component (A): a compound having one or more (meth)acryloyl groups in one molecule; component (B): a thermal radical initiator; component (C): a photoinitiator; and component (D): an anaerobic curing catalyst.

[0061] Steps 1 to 4 and components (A) to (D) are as explained above, and therefore will not be explained here.

[0062] <Applications> The adhesive composition according to the present invention can be used for fitting or laminating adherends (e.g., electromagnetic steel sheets, welch plugs) that are metals (e.g., SPCC (Steel Plate Cold Commercial) (cold-rolled steel sheets), copper). Some types of metals may not be suitable for anaerobic curing, but the use of the adhesive in combination with energy ray curing can promote curing and improve adhesive strength. Applications for the present invention include the screwing of ignition plugs and the assembly of laminated steel sheets and laminated molds for rotors and solenoids for rotating electrical machines, but it is preferably used for the assembly of laminated steel sheets.

[0063] <Curing Method> The adhesive composition according to the present invention can be cured by energy ray curing or room temperature anaerobic curing. The combined use of energy ray curing and anaerobic curing significantly improves the curing rate, enabling curing in a very short time. Energy rays refer to light in a broad sense, including radiation such as α-rays and β-rays, electromagnetic waves such as γ-rays and X-rays, electron beams (EB), and irradiation light with a wavelength of 150 to 750 nm. In particular, as the curing conditions for energy rays, irradiation light with a wavelength range of 150 to 750 nm is preferred, and ultraviolet light with a wavelength of about 150 to 400 nm and visible light with a wavelength of about 400 to 750 nm are preferably used. The light source for irradiating energy rays is not particularly limited, but examples include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, metal halide lamps, and LED lamps. The integrated light dose for energy ray irradiation is 1 to 100 kJ / m ２ It is preferable that the composition is cured with an integrated light amount of 5 to 70 kJ / m ２ and particularly preferably 10 to 50 kJ / m ２ The curing conditions for room temperature anaerobic curing are not particularly limited, but a curing time of 1 hour or more is effective for stabilizing the shear adhesive strength.

[0064] <Application Method> The adhesive composition according to the present invention can be applied to a thin steel sheet using methods similar to those used for known sealants and adhesives. For example, methods such as dispensing using an automatic coater, spraying, inkjet printing, screen printing, gravure printing, dipping, and spin coating can be used. From the viewpoint of coatability, the viscosity (25°C) of the adhesive composition according to the present invention is preferably 10 Pa s or less, more preferably 7 Pa s or less, and most preferably 5 Pa s or less.

[0065] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0066] [Examples 1 to 3, Comparative Example 1] The following components were prepared to prepare adhesive compositions. Component (A) Component (A-1): Polyether-based urethane acrylate oligomer (functionality: 2) having acryloyl groups at both ends Component (A-2): Epoxy acrylate oligomer (functionality: 2) having acryloyl groups at both ends and containing a bisphenol skeleton Component (A-3): 2-hydroxy-3-phenoxypropyl acrylate Trade name: Epoxy Ester M-600A (Kyoeisha Chemical Co., Ltd.) Component (A-4): 2-hydroxyethyl methacrylate Trade name: Acryester HO (Mitsubishi Chemical Corporation) Component (B) Component (B) Cumene hydroperoxide Trade name: Percumyl H-80 (NOF Corporation) Component (C) Component (C-1): 1-hydroxycyclohexyl phenyl ketone Trade name: DOUBLECURE 184 (Doublebond Chemical) Maximum absorption wavelength: 243 nm Component (C-2): 2,4,6-trimethylbenzoyl-diphenylphosphine oxide Trade name: DOUBLECURETPO (Doublebond Chemical) Maximum absorption wavelength: 380 nm Component (D) Component (D-1): o-sulfobenzimidazole sodium dihydrate (reagent) Component (D-2): saccharin (reagent) Component (D-3): benzothiazole (reagent) Component (D-4): 1-dodecanethiol (reagent) Component (E) Component (E-1): 2,6-di-t-butyl-p-cresol (BHT) (reagent) Component (E-2): hydroquinone (reagent) Component (E-3): 4-methoxyphenol (reagent) Other components ・2-hydroxyethyl methacrylate acid phosphate Trade name: JPA-514 (Johoku Chemical Industry Co., Ltd.) Ethylenediamine N,N,N',N'-tetraacetic acid disodium salt dihydrate (reagent) Ethylenediamine N,N,N',N'-tetraacetic acid tetrasodium salt tetrahydrate (reagent) Aminoketone fluorescent dye (KAYASET FLAVINE FG (Nippon Kayaku Co., Ltd.)) 3-acryloxypropyltrimethoxysilane trade name: KBM-5103 (Shin-Etsu Chemical Co., Ltd.).

[0067] The components (A), (D), (E), and other components were weighed into a stirring vessel and stirred for 30 minutes. Then, the components (B) and (C) were added in a dark place and stirred for 1 hour to prepare an adhesive composition. The detailed amounts prepared are shown in Table 1, and all values ​​are expressed in parts by mass.

[0068] [Tensile Shear Adhesive Strength] (Without UV Irradiation) The adhesive composition of Examples 1 to 3 or Comparative Example 1 was applied to a steel plate (SPCC-SD) test piece measuring 25 mm wide x 100 mm long x 1 mm thick. Thereafter, another steel plate (SPCC-SD) test piece was attached and fixed to the test piece so that the overlapping surface was 25 mm x 10 mm. Any excess adhesive composition that protruded from the bonded surface was wiped off, and the test piece was aged in an environment at 25°C for 24 hours to obtain a test piece. The shear adhesive strength (unit: MPa) of the prepared test piece was measured at 25°C using a universal tensile tester (tensile speed: 50 mm / min) in accordance with JIS K 6850:1999. The shear adhesive strength was defined as the value at maximum strength.

[0069] (With ultraviolet irradiation) The adhesive composition of Examples 1 to 3 or Comparative Example 1 was applied to a steel plate (SPCC-SD) test piece measuring 25 mm wide x 100 mm long x 1 mm thick. Thereafter, another steel plate (SPCC-SD) test piece was attached and fixed so that the overlapping surface was 25 mm x 10 mm. Any excess adhesive composition that protruded from the bonded surface was wiped off, and the adhesive composition was irradiated with an LED-UV irradiator at an integrated light dose of 30 kJ / m. ２ The specimens were irradiated with ultraviolet light at 100°C and aged for 24 hours in an environment at 25°C to obtain test specimens. The shear adhesive strength (unit: MPa) of the test specimens thus prepared was measured at 25°C using a universal tensile tester (tensile speed: 50 mm / min) in accordance with JIS K 6850:1999. The shear adhesive strength was defined as the value at the maximum strength.

[0070] [Gel time] 4 g of the adhesive composition of Examples 1 to 3 or Comparative Example 1 was weighed out into a glass test tube and allowed to stand in a thermostatic chamber at 80°C. Visual inspection was performed every hour to measure the time until the adhesive composition no longer flowed. Pass criteria: 2 hours or more.

[0071]

[0072] The adhesive compositions of Examples 1 to 3 showed improved adhesive strength when irradiated with UV. Furthermore, the adhesive compositions of Examples 1 to 3 also showed favorable results in terms of storage stability measured by gel time. On the other hand, the adhesive composition of Comparative Example 1, which did not contain component (C), showed no change in adhesive strength with or without UV irradiation. From the above, it can be seen that by including components (A) to (D) in an adhesive composition, an adhesive composition suitable for UV irradiation can be obtained.

[0073] The production method according to the present invention includes an energy ray irradiation step, which allows the adhesive composition to be cured in a short time, and by combining it with anaerobic curing properties, it is possible to cure the adhesive composition even to the interior, which is not exposed to energy rays, thereby improving adhesive strength and enabling more efficient production of laminated steel sheets. Furthermore, despite the adhesive composition according to the present invention having energy ray curing properties in addition to anaerobic curing properties, it is also able to maintain storage stability as an adhesive composition, which makes it extremely useful as it can increase the yield of the production process.

[0074] This application is based on Japanese Patent Application No. 2024-016403, filed on February 6, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0075] 1: Roll device 2: Strip-shaped thin steel plate 3: Processing oil application device 4: Die device 5: Punch section 6: Adhesive application device 7: Adhesive supply device 8: Outer shape punching punch section 9: Laminated steel plate 10: Punching hole 11: Fixing jig 12: Irradiator.

Claims

1. A method for producing a laminated steel sheet by laminating a predetermined number of thin steel sheets that have been punched into a predetermined shape from a strip-shaped thin steel sheet, the method comprising the following steps 1 to 4: step 1: punching the thin steel sheets into the predetermined shape; step 2: applying an adhesive composition to predetermined locations of the thin steel sheets of step 1; step 3: laminating the thin steel sheets of step 2 to produce a laminate; and step 4: irradiating the laminate of step 3 with energy rays, wherein the adhesive composition comprises the following components (A) to (D): component (A): a compound having one or more (meth)acryloyl groups in one molecule; component (B): a thermal radical initiator; component (C): a photoinitiator; and component (D): an anaerobic curing catalyst.

2. The method for producing a laminated steel sheet according to claim 1, wherein the component (C) comprises (C-1) a photoinitiator having a maximum absorption wavelength of less than 350 nm and (C-2) a photoinitiator having a maximum absorption wavelength of 350 nm or more.

3. The method for producing a laminated steel sheet according to claim 1 or 2, wherein the adhesive composition further contains a stabilizer as component (E).

4. The method for producing a laminated steel sheet according to claim 3, wherein said component (E) is at least one compound selected from the group consisting of 2,6-di-t-butyl-p-cresol, hydroquinone and 4-methoxyphenol.

5. The method for producing a laminated steel sheet according to claim 1 or 2, wherein the amount of the component (C) blended is 0.1 to 10 parts by mass per 100 parts by mass of the component (A).

6. The method for producing a laminated steel sheet according to claim 1 or 2, wherein the mass ratio of component (B) to component (C) is 10:90 to 90:

10.

7. The method for producing a laminated steel sheet according to claim 1 or 2, wherein the component (D) includes an azole compound and / or a mercaptan compound.

8. The method for producing a laminated steel sheet according to claim 1 or 2, further comprising a step of applying a hardening accelerator between the steps 1 and 2 and / or between the steps 2 and 3.

9. A laminated steel sheet manufactured by the method for manufacturing a laminated steel sheet according to claim 1.

10. A manufacturing apparatus for carrying out the method for manufacturing laminated steel sheets according to claim 1.

11. An adhesive composition comprising the following components (A) to (D), for use in a method for manufacturing a laminated steel sheet by laminating a predetermined number of thin steel sheets that have been punched into a predetermined shape from a strip-shaped thin steel sheet, the method comprising the following steps 1 to 4: step 1: punching the thin steel sheets into the predetermined shape; step 2: applying the adhesive composition to predetermined locations of the thin steel sheets of step 1; step 3: laminating the thin steel sheets of step 2 to produce a laminate; and step 4: irradiating the laminate of step 3 with energy rays, component (A): a compound having one or more (meth)acryloyl groups in one molecule; component (B): a thermal radical initiator; component (C): a photoinitiator; and component (D): an anaerobic curing catalyst.

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