Laminates, methods for manufacturing the same, and automotive exterior materials

Abstract

Provided is a laminated body in which, even in the case where multiple materials having different linear expansion coefficients are laminated via an adhesive, it is possible to keep warpage in the laminated body at a reduced level after the adhesive has undergone thermosetting.　A laminated body comprising a configuration of a first material / an adhesive layer / a second material, wherein said first material and second material have mutually different linear expansion coefficients, and the adhesive layer contains an adhesive which has a warpage reduction index, as defined in formula (1), of at least 30. <Warpage Reduction Index> The used analysis model is obtained by dividing, into finite elements, a laminated body obtained by applying an adhesive so as to have a thickness of 0.7 mm, between SPCC and an aluminum plate having a width of 25 mm, a length of 100 mm, and a thickness of 1.6 mm. The amount of displacement (amount of warpage (A)), which occurs at an edge of the laminated body when the center on the SPCC side is fixed and the temperature is changed from 180°C to 25°C, is calculated using CAE software.　By the same method, the amount of warpage (B), which occurs when an adhesive layer is not provided between the aluminum plate and the SPCC, is calculated by means of the CAE software, and then a warpage reduction index is obtained on the basis of formula (1).　(1): Warpage reduction index=100-(warpage amount (A) / warpage amount (B)) × 100

Description

[Technical Field]

[0001] The present invention relates to a laminate formed by stacking multiple materials with different coefficients of thermal expansion, a method for manufacturing the same, and an exterior material for automobiles. [Background technology]

[0002] In recent years, there has been a focus on reducing the weight of automobiles to improve fuel efficiency and reduce carbon dioxide emissions. For example, to reduce the weight of automobile exterior materials while improving strength and workability, the use of composite materials, such as steel plates and aluminum plates, which are laminated together, is being considered for use as exterior materials.

[0003] However, when laminating multiple materials using an adhesive, heating and curing the adhesive could sometimes cause warping of the laminate due to differences in the coefficients of thermal expansion of each material.

[0004] As a technique for reducing warping of laminates made of multiple materials with different coefficients of thermal expansion, for example, Patent Document 1 describes an adhesive structure in which adherends having a difference in thermal expansion are bonded to each other via an adhesive layer, wherein the adhesive layer has a two-layer structure, and at least one of the layers is formed of a flexible epoxy composition mainly composed of an epoxy resin having two or more epoxy groups and being flexible in the cured state, characterized in that the adhesive structure between adherends having a difference in thermal expansion is described.

[0005] Furthermore, Patent Document 2 describes a three-layer metal-resin composite structure in which a metal plate and a fiber-reinforced resin composition are joined via a foamed resin composition, wherein the foamed resin composition comprises, per 100 parts by mass of epoxy resin, 2 to 30 parts by mass of at least one of carbon fibers and glass fibers having a fiber length of 1 to 3 mm and a fiber diameter of 5 to 20 μm, 3 to 30 parts by mass of a heat-activated curing agent for epoxy resins, 0.5 to 15 parts by mass of a heat-activated curing catalyst for epoxy resins, 0.5 to 15 parts by mass of a thermal decomposition type organic foaming agent, 50 to 200 parts by mass of an inorganic filler with an aspect ratio of 2:1 or more, and 2 to 15 parts by mass of an anti-bubble agent. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-323639 [Patent Document 2] Japanese Patent Publication No. 2007-196545 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention provides a laminate that can reduce warping of the laminate after heat curing of the adhesive when multiple materials with different coefficients of thermal expansion are laminated together via an adhesive. [Means for solving the problem]

[0008] In other words, a laminate according to one aspect of the present invention is a laminate in which a first material / adhesive layer / second material are laminated in that order, the first material and the second material having different coefficients of thermal expansion, and the adhesive layer contains an adhesive having a warpage reduction index of 30 or more as shown in the following formula (1). <Warping Reduction Index> The warpage reduction index is determined by the following method. The analysis model is created by dividing a laminate, which consists of an aluminum plate measuring 25 mm wide x 100 mm long x 1.6 mm thick and SPCC (cold-rolled steel sheet), with an adhesive layer 0.7 mm thick applied between them, into finite elements. The center of the SPCC side is fixed, and the displacement of the ends of the laminate (warpage (A)) is calculated using CAE software when the temperature is changed from 180°C to 25°C. Using a similar method, the amount of warpage (B) when no adhesive layer is provided between the aluminum sheet and SPCC (cold-rolled steel sheet) is calculated using CAE software, and the warpage reduction index is determined based on the following formula (1). Warping reduction index = 100 - {Warping amount (A) / Warping amount (B)} × 100 ... (1)

[0009] Furthermore, another aspect of the present invention is a laminate comprising a first material / adhesive layer / second material, wherein the first material and the second material have different coefficients of thermal expansion, and the average storage modulus of the adhesive layer at 25 to 180°C is 1 to 400 MPa. [Effects of the Invention]

[0010] The laminate of the present invention can reduce warping of the laminate after heat curing of the adhesive when multiple materials with different coefficients of thermal expansion are laminated. [Modes for carrying out the invention]

[0011] The present invention will be described in more detail below based on examples of embodiments, but the present invention is not limited to these embodiments.

[0012] 1. Laminate A laminate according to one embodiment of the present invention is a laminate comprising a first material / adhesive layer / second material, wherein the first material and the second material have different coefficients of thermal expansion, and the adhesive layer contains an adhesive whose warpage reduction index shown in formula (1) is 30 or higher.

[0013] (1) The first and second materials The first and second materials in this embodiment are not particularly limited as long as their coefficients of thermal expansion are different from each other. For example, metal, resin, glass, etc., can be used as the first and second materials. Only one of these materials may be used, or two or more may be used in any combination and ratio. Examples of the above-mentioned metals include aluminum, iron, copper, titanium, magnesium, and alloys containing one or more of these metals. As the resin, for example, curable resins such as epoxy resin, phenol resin, vinyl ester resin, urethane resin, melamine resin, urea resin, silicone resin, acrylic resin, unsaturated polyester resin, etc.; polyethylene resin, polypropylene resin, polyamide resin, polystyrene resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, acrylic resin, polyvinyl chloride resin, polyester resins such as polyethylene terephthalate, PBT (polybutylene terephthalate), polyoxymethylene resin, polyamide resin, fluororesin, polyimide resin, polyaminoamide resin, PES (polyethersulfone) resin, PPS (polyphenylene sulfide) resin, PEI (polyetherimide) resin, PPE (polyphenylene ether) resin, polyparaphenylene benzoxazole resin, PEEK (polyether ether ketone resin), polyacetal resin, polycarbonate resin, polyamideimide resin, etc., thermoplastic resins can be used. Furthermore, fiber-reinforced resins obtained by adding reinforcing fibers to the above resin can also be used. As the reinforcing fibers, for example, inorganic fibers such as carbon fiber, silicon carbide fiber, alumina fiber, boron fiber, glass fiber, etc.; organic fibers such as polyester fiber, polyethylene terephthalate fiber, polyparaphenylene benzobisoxazole fiber, aramid fiber, polyacetal fiber, polyethylene fiber, polyacrylonitrile fiber, etc.; natural fibers such as cellulose-based fibers, etc. can be used.

[0014] As the combination of the first and second materials, when the first and second materials are each a metal, particularly when the first or second material contains aluminum or iron, and further when the first material contains aluminum and the second material contains iron, the present invention can be preferably used.

[0015] Also, when the first and second materials are each a metal, when the difference in linear expansion coefficient between the first material and the second material is 2×10 -6 [1 / K] or more, particularly when the difference in linear expansion coefficient is 5×10 -6 [1 / K] or more, the present invention can be preferably used. The upper limit of the difference in the linear expansion coefficients of the first material and the second material is not particularly limited, but when it is 1×10 -4 [1 / K] or less, particularly when it is 9×10 -5 [1 / K] or less, and more particularly when it is 7×10 -5 [1 / K] or less, the present invention can be preferably used.

[0016] In this embodiment, the thicknesses of the first and second materials are preferably 0.1 to 10 mm, and more preferably 0.3 to 5 mm, respectively. By setting within the above range, it becomes possible to achieve both light weight and rigidity, which is preferable for use in automotive applications and the like.

[0017] (2) Adhesive layer The adhesive layer in this embodiment contains an adhesive having a warpage reduction index of 30 or more shown by the following formula (1).

[0018] In the laminate of this embodiment, by providing a specific adhesive layer between the first material and the second material having different linear expansion coefficients from each other, the adhesive layer can absorb the difference in the linear expansion coefficients of the first material and the second material, and reduce the warpage of the laminate. To obtain an adhesive having a warpage reduction index of 30 or more, as will be described later, the type and components of the adhesive, the average storage elastic modulus, the thickness, etc. may be adjusted.

[0019] <<Warpage reduction index>> In this specification, the "warpage reduction index" indicates how much the warpage amount of the laminate when heated with an adhesive layer provided between an aluminum plate and a cold-rolled steel sheet (SPCC) is reduced with respect to the warpage amount of the laminate when the adhesive layer is not provided.

[0020] The warpage reduction index can be obtained more specifically by the following method. An aluminum plate having a width of 25 mm × a length of 100 mm × a thickness of 1.6 mm (linear expansion coefficient: 23×10 -6[1 / K], Young's modulus: 70 GPa, Poisson's ratio: 0.3) and SPCC (cold-rolled steel sheet) with a width of 25 mm x length of 100 mm x thickness of 1.6 mm (coefficient of linear expansion: 16 x 10 -6 The analytical model is a laminate formed by applying an adhesive to a thickness of 0.7 mm between two layers (1 / K, Young's modulus: 200 GPa, Poisson's ratio: 0.3) and dividing the laminate into finite elements. The center of the SPCC (cold-rolled steel sheet) side is fixed, and the displacement (warpage (A)) of the edges of the laminate when the temperature is changed from 180°C to 25°C is calculated using CAE (Computer-Aided Engineering) software. Using a similar method, the amount of warpage (B) when no adhesive layer is provided between the aluminum sheet and SPCC (cold-rolled steel sheet) is calculated using CAE software, and the warpage reduction index is determined based on the following formula (1). Warping reduction index = 100 - {Warping amount (A) / Warping amount (B)} × 100 ... (1)

[0021] As is clear from formula (1) above, a higher value of the warpage reduction index indicates that the warpage of the laminate is reduced. The warpage reduction index is preferably 30 or higher, and more preferably 40 or higher, with an upper limit of 100.

[0022] <<Average Storage Modulus>> In this embodiment, the adhesive preferably has an average storage modulus of 1 to 400 MPa at 25 to 180°C in the cured state of a laminate comprising a first material / adhesive layer / second material. By having the average storage modulus within this numerical range, it is possible to reduce warping of the laminate while improving the adhesion between the first material and the second material. Within the temperature range of 25 to 180°C, in the temperature range above the glass transition temperature (Tg) of the adhesive, the storage modulus is low, and the strain due to the difference in linear expansion coefficients between the first and second materials is almost completely relieved by the adhesive, making warping of the laminate less likely. On the other hand, in the temperature range below the glass transition temperature (Tg) of the adhesive, the storage modulus is high, and the strain due to the difference in linear expansion coefficients between the first and second materials is less easily relieved by the adhesive, making warping of the laminate more likely. Therefore, by taking the average value of the storage modulus in the 25 to 180°C range, the total amount of strain and the amount of strain relief by the adhesive in the temperature range above and below the glass transition temperature (Tg) are averaged out. Consequently, this average storage modulus in the 25 to 180°C range correlates with the actual amount of warping. From the viewpoint of improving adhesion between the first material and the second material, the mean storage modulus is preferably 5 MPa or more, more preferably 10 MPa or more, even more preferably 50 MPa or more, and even more preferably 80 MPa or more. Furthermore, from the viewpoint of absorbing the difference in the coefficient of linear expansion between the first material and the second material, the average storage modulus is preferably 300 MPa or less, more preferably 200 MPa or less, even more preferably 150 MPa or less, and even more preferably 120 MPa or less. The average storage modulus of an adhesive can be determined by selecting the components of the adhesive, such as the main resin and curing agent, as well as by (a) introducing a molecular skeleton that exhibits flexibility into the main chain of the main resin, (b) adding plasticizers or reactive diluents, or (c) adding elastomers or thermoplastic resins as modifiers.

[0023] The mean storage modulus can be determined, for example, by the following method. The adhesive is applied to a Teflon® plate to a thickness of 0.5 mm and heated at 180°C for 20 minutes to cure. After natural cooling, the cured adhesive is cut into pieces 5 mm wide x 10 mm long to prepare test specimens. The storage modulus of the test specimen is measured using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd. "DVA 225") and a tensile jig at a measurement temperature of 25 to 180°C, a frequency of 10 Hz, and a heating rate of 10°C / min. The average storage modulus at 25 to 180°C is calculated by dividing the storage modulus at 25 to 180°C by the number of measurement points.

[0024] <<Mean coefficient of linear expansion>> In this embodiment, the average linear expansion coefficient (also called the "average thermal expansion coefficient") of the adhesive layer is typically greater than 0 ppm / K, preferably 10 ppm / K or more, more preferably 20 ppm / K or more, even more preferably 30 ppm / K or more, and particularly preferably 50 ppm / K or more, within a measurement range within a temperature range of 0°C or higher and below the glass transition temperature of the adhesive layer. Furthermore, the average coefficient of linear expansion of the adhesive layer is usually 5000 ppm / K or less, preferably 2000 ppm / K or less, more preferably 1000 ppm / K or less, even more preferably 800 ppm / K or less, particularly preferably 600 ppm / K or less, and most preferably 400 ppm / K or less. Within this range, there is less strain between the first and second materials in the laminate, which is preferable from the viewpoint of suppressing warping and delamination.

[0025] The average coefficient of linear expansion of the adhesive layer can be measured by thermomechanical analysis in accordance with JIS K7197 (2012). For example, using the thermal analyzer "TMA Q400" (manufactured by T.A. Instruments Japan), a sample with a width of 5 mm and a length of 16 mm is heated at a measurement temperature of 0 to 180°C and a heating rate of 10°C / min to measure the coefficient of thermal expansion in the in-plane direction. Based on this result, the coefficient of thermal expansion in the in-plane direction at 25 to 180°C is measured, and the average linear expansion coefficient is calculated from the slope of the graph.

[0026] The average coefficient of linear thermal expansion of the adhesive layer can be adjusted by selecting the type of components in the adhesive, such as the main resin and curing agent, as well as by introducing rigid components such as aromatic rings into the resin skeleton, increasing the crosslink density by controlling the molecular weight, and adding fillers and plasticizers.

[0027] <<Glass transition temperature (Tg)>> In this embodiment, the glass transition temperature (Tg) of the adhesive layer is typically -130°C or higher, preferably -110°C or higher, more preferably -80°C or higher, even more preferably -70°C or higher, and particularly preferably -60°C or higher. Furthermore, the temperature is usually 190°C or lower, preferably 170°C or lower, more preferably 150°C or lower, and even more preferably 130°C or lower. By having the glass transition temperature (Tg) of the adhesive layer within the above range, the stress generated during cooling after curing, resulting from the difference in the coefficient of linear expansion between the two adherends via the adhesive layer of the laminate in this embodiment, is reduced, thereby reducing warping. The glass transition temperature of the adhesive layer can be determined from the tanδ peak in viscoelasticity measurements.

[0028] Methods for adjusting the glass transition temperature of the adhesive layer include selecting the type of adhesive components, such as the main resin and curing agent, as well as introducing heat-resistant structures such as aromatic rings and double bonds into the resin skeleton, introducing highly interacting polar groups, and increasing the crosslink density by controlling the molecular weight.

[0029] <<Thickness>> In this embodiment, the thickness of the adhesive layer is preferably 0.1 to 2.0 mm. By having the thickness of the adhesive layer within the above numerical range, it is possible to reduce warping of the laminate while improving the adhesion between the first material and the second material. In particular, from the viewpoint of absorbing the difference in the coefficient of thermal expansion between the first material and the second material, the thickness of the adhesive layer is preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. Furthermore, since the tensile shear adhesive strength of the adhesive layer improves as the thickness of the adhesive layer decreases, the thickness of the adhesive layer is preferably 1.8 mm or less, more preferably 1.6 mm or less, and even more preferably 1.4 mm or less.

[0030] <<Tensile Shear Bond Strength>> In this embodiment, the adhesive preferably has a tensile shear adhesive strength of 10 MPa or more, more preferably 15 MPa or more, and even more preferably 20 MPa or more, in the cured state of a laminate comprising a first material / adhesive layer / second material. Having the tensile shear adhesive strength within the above numerical range ensures good adhesion between the first material and the second material. Furthermore, from the viewpoint of re-peeling due to recycling of the laminate, the tensile shear adhesive strength of the adhesive layer is preferably 50 MPa or less, more preferably 45 MPa or less, and even more preferably 40 MPa or less.

[0031] The tensile shear adhesive strength can be determined, for example, by the method described in JIS K 6850. More specifically, it is as follows: Two pieces of stainless steel (SUS) measuring 25 mm wide x 100 mm long x 1.6 mm thick are used. Adhesive is applied to one of the SUS pieces in an area measuring 25 mm wide x 12.5 mm long, to a thickness of 0.05 to 0.20 mm. The SUS pieces are pressed together using clamps, with the adhesive-coated surface between them, and heated at 180°C for 20 minutes to cure the adhesive, thereby creating a test specimen. The tensile shear adhesive strength of the test specimen is measured using a tensile testing machine (Shimadzu Corporation "Autograph AG-X") at 23°C and 50% RH at a speed of 5 mm / min.

[0032] <<Components of the adhesive layer>> The components of the adhesive layer in this embodiment are not particularly limited as long as the warpage reduction index is 30 or higher, but from the viewpoint of adhesion to the first and second materials, durability, and heat resistance, it is preferable to use one in which epoxy resin is the main component resin. Here, "main component" in this specification means the component that has the highest content (mass%) among the components constituting the adhesive layer. The content of the main component in the adhesive layer is preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more (it may also be 100% by mass).

[0033] <Epoxy resin> The following describes preferred examples of epoxy resins in this embodiment. Examples of the epoxy resins mentioned above include alcohol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, naphthalene-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, biphenyl-type epoxy resins, triphenylmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, glycidyl ester-type epoxy resins, glycidylamine-type epoxy resins, polyfunctional phenol-type epoxy resins, and aliphatic epoxy resins. In this embodiment, only one of the epoxy resins exemplified above may be used, or two or more may be used in any combination and ratio.

[0034] In particular, in this embodiment, it is preferable to use an epoxy resin having at least one of the following skeletons: phenyl skeleton (phenol skeleton), naphthalene skeleton, fluorene skeleton, biphenyl skeleton, anthracene skeleton, pyrene skeleton, xanthene skeleton, adamantane skeleton, and dicyclopentadiene skeleton. From the viewpoint of heat resistance, it is more preferable to use an epoxy resin having at least one of the phenyl skeleton, fluorene skeleton, and biphenyl skeleton. From the viewpoint of ease of manufacture and heat resistance, it is even more preferable to use an epoxy resin having at least one of the following skeletons: bisphenol A skeleton, bisphenol F skeleton, and biphenyl skeleton. The type and structure of epoxy resins can be confirmed by NMR (nuclear magnetic resonance spectroscopy), IR (infrared spectroscopy), SEM (scanning electron microscopy) analysis, IPC (inductively coupled plasma) emission spectroscopy, TGA (thermogravimetric analysis), DSC (differential scanning calorimetry), and various chromatography methods.

[0035] In this embodiment, it is even more preferable that the epoxy resin contains one obtained from the epoxy resin precursor and curing agent described below, among the epoxy resins mentioned above.

[0036] (Epoxy resin precursor) In this embodiment, the epoxy resin precursor refers to a compound containing one or more epoxy compounds that can be cured to produce an epoxy resin. The epoxy compound is a compound having an epoxy group in its molecule, and is a compound that can be subjected to an addition reaction or self-polymerization reaction by at least one of the curing agent and curing catalyst described later, thereby constituting a thermosetting resin.

[0037] Examples of the epoxy compounds that can be used include bisphenols such as bisphenol A, bisphenol F, bisphenol B, bisphenol C, bisphenol AD, and bisphenolacetophenone; bifunctional aromatic epoxy compounds such as biphenol, catechol, resorcinol, hydroquinone, and dihydroxynaphthalene-type bifunctional phenol-type epoxy compounds; bifunctional aliphatic epoxy compounds such as bifunctional glycidyl ether-type epoxy compounds, bifunctional glycidyl ester-type epoxy compounds, bifunctional glycidylamine-type epoxy compounds, and bifunctional linear aliphatic epoxy compounds; bifunctional alicyclic epoxy compounds; bifunctional heterocyclic epoxy compounds; and hydrogenated epoxy compounds such as hydrogenated bisphenol A-type epoxy compounds. In this embodiment, the epoxy resin precursor may be one of the epoxy compounds exemplified above, or two or more may be used in any combination and ratio.

[0038] In this embodiment, it is preferable that the epoxy resin precursor contains one or more compounds, including the epoxy compounds exemplified above. From the viewpoint of the flexibility of the resulting epoxy resin, it is more preferable to use at least one difunctional aliphatic epoxy compound.

[0039] In this embodiment, the epoxy resin precursor more preferably contains a difunctional aliphatic epoxy compound and an aromatic compound.

[0040] As the above-mentioned bifunctional aliphatic epoxy compound, an aliphatic epoxy compound derived from diglycidyl ether with a purity of 90% by mass or higher can be used, obtained by reacting a diol having 2 to 12 carbon atoms with an epihalohydrin and then purifying it by distillation. Examples of the above-mentioned bifunctional aliphatic epoxy compounds include glycidyl ether of ethylene glycol, glycidyl ether of propylene glycol, glycidyl ether of 1,4-butanediol, glycidyl ether of 1,6-hexanediol, glycidyl ether of 1,8-octanediol, glycidyl ether of 1,10-decanediol, glycidyl ether of 2,2-dimethyl-1,3-propanediol, glycidyl ether of diethylene glycol, glycidyl ether of triethylene glycol, glycidyl ether of tetraethylene glycol, glycidyl ether of hexaethylene glycol, and glycidyl ether of 1,4-cyclohexanedimethanol. Among these, it is preferable to use glycidyl ether of 1,4-butanediol, glycidyl ether of 1,6-hexanediol, glycidyl ether of 1,4-cyclohexanedimethanol, or glycidyl ether of 2,2-dimethyl-1,3-propanediol, as these have a significant effect in reducing the viscosity of the epoxy resin precursor and minimize the decrease in the heat resistance of the cured product.

[0041] Examples of the above aromatic compounds include bisphenols such as bisphenol A, bisphenol F, bisphenol B, bisphenol C, bisphenol AD, and bisphenolacetophenone, as well as compounds having a skeleton such as biphenol, catechol, resorcinol, hydroquinone, and dihydroxynaphthalene. Among these, it is preferable to use at least one of bisphenol A and bisphenol F from the viewpoint of the rigidity and heat resistance of the resulting epoxy resin.

[0042] In other words, the epoxy resin precursor in this embodiment is more preferably a difunctional aliphatic epoxy compound and at least one compound of bisphenol A and bisphenol F.

[0043] In this embodiment, if the epoxy resin precursor contains two or more compounds including an epoxy compound, it is preferable to use a mixture and / or reaction of the two or more compounds as the epoxy resin precursor, and it is more preferable to use a mixture of the two or more compounds and a polymerization initiator, followed by a polymerization reaction. As the polymerization initiator mentioned above, the same curing agent used for curing the epoxy resin precursor can be used. Among these, thermal polymerization initiators such as phosphonium salts, sulfonium salts, benzothiazonium salts, and ammonium salts are preferred, with phosphonium salts being more preferred.

[0044] In other words, as the epoxy resin precursor in this embodiment, it is preferable to use one obtained by mixing the difunctional aliphatic epoxy compound exemplified above with an aromatic compound and a polymerization initiator and performing a polymerization reaction, and it is more preferable to use one obtained by mixing the difunctional aliphatic epoxy compound with at least one compound of bisphenol A and bisphenol F and a polymerization initiator and performing a polymerization reaction.

[0045] Therefore, it is particularly preferable that the epoxy resin precursor in this embodiment contains a bifunctional epoxy compound having both an aliphatic skeleton and an aromatic skeleton.

[0046] (average molecular weight) There are no particular limitations on the molecular weight of the epoxy resin precursor in this embodiment. The molecular weight of the epoxy resin precursor is typically 100 or more, preferably 200 or more, and more preferably 300 or more, based on the mass-average molecular weight (Mw) in polystyrene terms, as measured by gel permeation chromatography (GPC). On the other hand, the molecular weight of the epoxy resin precursor is typically 200,000 or less, preferably 100,000 or less, and more preferably 50,000 or less. Furthermore, the number-average molecular weight (Mn) of the epoxy resin precursor is usually 100 or more, preferably 200 or more, and more preferably 300 or more. On the other hand, the number-average molecular weight of the epoxy resin precursor is usually 100,000 or less, preferably 80,000 or less, and more preferably 50,000 or less. Having the molecular weight of the epoxy resin precursor within the above range is preferable because it improves the solubility of the curing agent and each component in the epoxy resin precursor, resulting in an adhesive with properties such as viscosity that are easy to handle with conventional manufacturing equipment, and thus improving adhesion.

[0047] (Epoxy group equivalent) The epoxy group equivalent (or epoxy equivalent) of the epoxy resin precursor in this embodiment can be measured by the method shown in JIS K 7236. The epoxy group equivalent of the epoxy resin precursor is usually 50 or more, preferably 80 or more, more preferably 100 or more, even more preferably 120 or more, and particularly preferably 150 or more. On the other hand, the epoxy group equivalent of the epoxy resin precursor is usually 100,000 or less, preferably 10,000 or less, more preferably 3,000 or less, even more preferably 1,500 or less, and particularly preferably 1,000 or less. When the epoxy equivalent of the epoxy resin precursor is 100,000 or less, the amount of epoxy groups and hydroxyl groups produced after the reaction increases, which increases the interaction with the first and second materials that become the adherends, resulting in excellent adhesion after curing. On the other hand, if the epoxy equivalent of the epoxy resin precursor is 50 or higher, the crosslinking density decreases, improving flexibility and elasticity, resulting in superior warping reduction in the laminate. Methods for adjusting the epoxy group equivalent of an epoxy resin precursor include reducing the degree of polymerization in the epoxy resin skeleton or introducing a skeleton with a small molecular weight.

[0048] (viscosity) In this embodiment, the viscosity of the epoxy resin precursor at 25°C and 1 atm is preferably 0.01 Pa·s or higher, more preferably 0.05 Pa·s or higher, and particularly preferably 0.1 Pa·s or higher. On the other hand, the viscosity of the epoxy resin precursor is preferably 10,000 Pa·s or lower, more preferably 8,000 Pa·s or lower, and particularly preferably 5,000 Pa·s or lower. If the viscosity of the epoxy resin precursor is 10,000 Pa·s or less, the impregnation into the support can be improved. Furthermore, if the viscosity of the epoxy resin precursor is 0.01 Pa·s or more, the handling properties when forming the adhesive into a sheet can be improved, and resin flow can be prevented when creating laminates. The viscosity of the epoxy resin precursor can be determined by measuring the value using a B-type rotational viscometer (Brookfield viscometer) under conditions of 25°C.

[0049] The viscosity of epoxy resin precursors can be reduced by methods such as controlling the repeating unit amount to reduce molecular weight and reducing the amount of polar groups in the unit structure.

[0050] (Hardening agent) Examples of curing agents in this embodiment include thermosetting agents that start reacting with heat, and photocuring agents that start reacting with light. The curing agent can be appropriately selected from known curing agents depending on the curing method of the adhesive in the laminate of this embodiment. For example, a photocuring agent (photopolymerization initiator) can be selected when using a photocuring method, and a thermocuring agent (thermal polymerization initiator) can be selected when using a thermocuring method. The photocuring method is a curing method that uses at least one of the active energy ray curing methods, namely ultraviolet light, visible light, and infrared light. In this embodiment, if it is desired to cure the epoxy resin precursor in an environment where light irradiation is difficult, it is preferable to cure it by a thermocuring method, and in this embodiment, it is preferable to use a thermocuring agent or a combination of a thermocuring agent and a photocuring agent.

[0051] =Thermosetting agent= Examples of thermosetting agents in this embodiment include phenolic curing agents; amine curing agents such as aliphatic amines, polyetheramines, alicyclic amines, and aromatic amines; acid anhydride curing agents; amide curing agents; urea curing agents; tertiary amines; imidazoles and their derivatives; organophosphines; phosphonium salts; tetraphenylboron salts; organic acid dihydrazides; boron halogenated amine complexes; polymercaptan curing agents; isocyanate curing agents; and blocked isocyanate curing agents.

[0052] Of the above, phenolic curing agents, amine curing agents, acid anhydride curing agents, etc., are incorporated into the epoxy resin framework by reacting with the epoxy resin precursor. Therefore, the most preferable amount of curing agent to be blended into the epoxy resin in this embodiment is an amount such that the epoxy group and the active part (active hydrogen part, acid anhydride part) are in chemical equivalent (1.0). However, the amount of curing agent may be adjusted to control viscosity, reaction rate, and physical properties after curing. In this case, the amount of curing agent blended relative to the epoxy group is preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more, based on chemical equivalent. Furthermore, a chemical equivalent of 5.0 or less is preferred, more preferably 4.0 or less, and even more preferably 3.0 or less. It is preferable that the blending amount is within the above range, as this prevents the elution of unreacted components and insufficient crosslinking density during use, resulting in good heat resistance and moisture resistance of the epoxy resin.

[0053] Furthermore, curing agents other than phenolic, amine, and acid anhydride-based curing agents typically act primarily as curing catalysts or co-catalysts in the self-polymerization of epoxy resin precursors. The amount of curing agent to be added is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of epoxy resin precursor. On the other hand, the amount of curing agent to be added is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of epoxy resin precursor. If the amount added is 0.01 parts by mass or more, the curing reaction of the epoxy resin precursor is accelerated. Furthermore, if the amount added is 20 parts by mass or less, the resin composite material is less likely to experience a decrease in physical properties such as heat resistance and moisture resistance due to residual curing agent, and catalyst bleed-out during use is less likely to occur.

[0054] -Phenol-based curing agent- Examples of the phenolic curing agents mentioned above include bisphenol A, bisphenol F, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 1,4-bis(4-hydroxyphenoxy)benzene, 1,3-bis(4-hydroxyphenoxy)benzene, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, phenol novolac, bisphenol A novolac, o-cresol novolac, m-cresol novolac, p-cresol novolac, xylenol novolac, poly-p-hydroxystyrene, hydroquinone, resorcinol, catechol, and t-butylcatechol. t-butylhydroquinone, fluoroglycinol, pyrogallol, t-butylpyrogallol, allylated pyrogallol, polyallylated pyrogallol, 1,2,4-benzenetriol, 2,3,4-trihydroxybenzophenone, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene Examples include 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,4-dihydroxynaphthalene, 2,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,8-dihydroxynaphthalene, allylated and polyallylated dihydroxynaphthalenes, allylated bisphenol A, allylated bisphenol F, allylated phenol novolac, allylated pyrogallol, and the like.

[0055] - Amine-based curing agents - Aliphatic amines, polyetheramines, alicyclic amines, aromatic amines, and the like can be used as the amine-based curing agent. Examples of aliphatic amines include ethylenediamine, 1,3-diaminopropane, 1,4-diaminopropane, hexamethylenediamine, 2,5-dimethylhexamethylenediamine, trimethylhexamethylenediamine, diethylenetriamine, iminobispropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-hydroxyethylethylenediamine, and tetra(hydroxyethyl)ethylenediamine. Examples of polyetheramines include triethylene glycol diamine, tetraethylene glycol diamine, diethylene glycol bis(propylamine), polyoxypropylenediamine, and polyoxypropylene triamines. Examples of alicyclic amines include isophoronediamine, metacenediamine, N-aminoethylpiperazine, bis(4-amino-3-methyldicyclohexyl)methane, bis(aminomethyl)cyclohexane, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, and norbornenediamine. Aromatic amines include tetrachloro-p-xylenediamine, m-xylenediamine, p-xylenediamine, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, 2,4-diaminoanisole, 2,4-toluenediamine, 2,4-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diamino-1,2-diphenylethane, 2,4-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, m-aminophenol, m-aminobenzylamine, benzyldimethylamine, 2-(dimethylaminomethyl)phenol, triethanolamine, methylbenzylamine, α-(m-aminophenyl)ethylamine, α-(p-aminophenyl)ethylamine, diaminodiethyldimethyldiphenylmethane, and α,α'-bis(4-aminophenyl)-p-diisopropylbenzene.

[0056] -Acid anhydride curing agent- Examples of the above acid anhydride-based curing agents include dodecenyl succinic anhydride, polyadipic anhydride, polyazelaic anhydride, polysebacic anhydride, poly(ethyl octadecanediic acid) anhydride, poly(phenylhexadecanedioic acid) anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methylhymic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexenedicarboxylic acid anhydride, methylcyclohexenetetracarboxylic acid anhydride, and phthalic anhydride. Examples include acids, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, ethylene glycol bistrimellitate dianhydride, hetic anhydride, nadic anhydride, methylnadic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexane-1,2-dicarboxylic anhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic acid dianhydride, and 1-methyl-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic acid dianhydride.

[0057] - Amide-based curing agent - Examples of the above-mentioned amide-based curing agents include dicyandiamide and polyamide resins.

[0058] -Urea-based hardening agent- Examples of the above-mentioned urea-based curing agents include urea compounds such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-phenyl-1,1-dimethylurea, toluenebis(dimethylurea), and 4,4'-methylenebis(phenyldimethylurea).

[0059] -Tertiary amine- Examples of the above-mentioned tertiary amines include 1,8-diazabicyclo(5,4,0)undecene-7, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol.

[0060] - Imidazole and its derivatives - Examples of the above imidazoles and their derivatives include 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole, 2-ethyl-4(5)-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyano-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[ Examples include 2'-methylimidazolyl-(1')-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and compounds obtained by adding these imidazoles to epoxy compounds.

[0061] -Organophosphines- Examples of the above-mentioned organic phosphines include tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine.

[0062] -Phosphonium salt- Examples of the phosphonium salts mentioned above include tetraphenylphosphonium-tetraphenylborate, tetraphenylphosphonium-ethyltriphenylborate, and tetrabutylphosphonium-tetrabutylborate.

[0063] -Tetraphenylborone salt- Examples of the tetraphenylborone salts mentioned above include 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate.

[0064] =Photocuring agent= Examples of photocuring agents in this embodiment include acetophenones, benzophenones, benzoin ethers, hydroxyketones, acylphosphine oxides, diazonium cationonium salts, iodonium cationonium salts, sulfonium cationonium salts, and the like.

[0065] Specific examples of photocuring agents include 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 1-hydroxy-cyclohexylphenyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1,2-hydroxy C-2-methyl-1-phenylpropan-1-one, 2-[methyl-1-(4-methylthio)phenyl]-2-morpholinopropan-1-one, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-hydroxy-2-methyl-[4-(1-methylvinyl)phenyl]propanol oligomer, isopropylthioxanthone, o-benzoylbenzoic acid Methyl, [4-(methylphenylthio)phenyl]phenylmethane, 2,4-diethylthioxanthone, 2-chlorothioxanthone, benzophenone, ethylanthraquinone, benzophenone ammonium salt, thioxanthone ammonium salt, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2,4,6-trimethylbenzophenone, 4-methylbenzophenone, 4,4'-bisdiethylaminobenzophenone, 1,4-dibenzoylbenzene, 10 -Butyl-2-chloroacridone, 2,2'-bis(o-chlorophenyl)-4,5,4',5'-tetrakis(3,4,5-trimethoxyphenyl)-1,2'-biimidazole, 2,2'-bis(o-chlorophenyl)-4,5,4',5'-tetraphenyl-1,2'-biimidazole, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoyldiphenyl ether, acrylic benzophenone, dibenzoyl, bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-Difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium, o-methylbenzoyl benzoate, p-dimethylaminobenzoate ethyl ester, p-dimethylaminobenzoate isoamyl ethyl ester, activated tert-amine, carbazole-phenone photopolymerization initiator, acridine photopolymerization initiator, triazine photopolymerization initiator, benzoyl, triallylsulfonium, hexafluorophosphate salt, phosphorus hexafluoride-based aromatic sulfonium salt, antimony hexafluoride-based aromatic sulfonium salt, antimony hexafluoride-based aromatic sulfonium Salt, antimony hexafluoride-based aromatic sulfonium salt, triallylsulfonium, hexafluoroantimony, 4-methylphenyl-[4-(2-methylpropyl)phenyl]-iodonium hexafluorophosphate, 1,2-octanedione, 1-[4-(phenylthio)-2-(o-benzoyl oxime)], 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-1-(o-acetyloxime), ethyl-4-dimethylaminobenzoate, ethyl-4-dimethylaminobenzoate, 2-ethylhexyl-4 -Dimethylaminobenzoate, (9-oxo-9H-xanthene-2-yl)phenyliodonium hexafluorophosphate, bis[4-n-alkyl(C10~13)phenyl]iodonium hexafluorophosphate, bis[4-n-alkyl(C10~13)phenyl]iodonium hexafluoroantimony, triphenylsulfonium trifluorosulfonate, triphenylsulfonium bicyclo[2.2.1]heptan-1-methanesulfonate, (9-oxo-9H-xanthene-2-yl)phenylsulfonium hexafluorophosphate Olophosphate, p-azidobenzaldehyde, p-azidoacetophenone, p-azidobenzoic acid, p-azidobenzaldehyde-2-sulfonate sodium salt, p-azidobenzalacetophenone, 4,4'-diazidochalcone, 4,4'-diazidodiphenyl sulfide, 3,3'-diazidodiphenyl sulfide, 2,6-bis-(4'-azidobenzal)-4-methylcyclohexane, 1,3-bis-(4'-azidobenzal)-propanone, 4,4'-diazidochalcone-2-sulfonate sodium salt, 4,4'-diazidostilbene-2,2'-Sodium disulfonate, 1,3'-Bis-(4'-azidobenzal)-2'-Sodium disulfonate-2-propanone, 2,6-Bis-(4'-azidobenzal)-2'-Sulfonic acid (sodium salt) cyclohexanone, 2,6-Bis-(4'-azidobenzal)-2'-Sulfonic acid (sodium salt) 4-methylcyclohexanone, α-Cyano-4,4'-Dibenzostilbene, 2,5-Bis-(4'-azidobenzalsulfonic acid Sodium salt) cyclopentanone, 3-sulfonyl azidobenzoic acid, 4-sulfonyl azidobenzoic acid, cinnamic acid, α-cyanocinnamyrideneacetone acid, p-azido-α-cyanocinnamic acid, p-phenylenediacrylic acid, p-phenylenediacrylate diethyl ester, polyvinyl cinnamate, polyphenoxy-isopropyl cinnamyridene acetate, polyphenoxy-isopropyl-α-cyanocinnamyridene acetate, naphthoxy Non(1,2)diazide(2)-4-sulfonate sodium salt, naphthoquinone(1,2)diazide(2)-5-sulfonate sodium salt, naphthoquinone(1,2)diazide(2)-5-sulfonate ester (I), naphthoquinone(1,2)diazide(2)-5-sulfonate ester (II), naphthoquinone(1,2)diazide(2)-4-sulfonate salt, 2,3,4,4'-tetrahydroxybenzophenone tri(naphthoquinone diazide sulfonate Examples include esters, naphthoquinone-1,2,5-(trihydroxybenzophenone) triester, 1,4-iminoquinone-diazide(4)-2-sulfoamide(I), 1-diazo-2,5-diethoxy-4-p-trimercaptobenzene salt, 5-nitroacenaphthene, N-acetylamino-4-nitronaphthalene, organoboron compounds, and other photoacid generators that generate cations upon exposure to light, and photobase generators that generate anions upon exposure to light.

[0066] In this embodiment, the curing agent may be one of the curing agents exemplified above used alone, or two or more may be used in any combination and ratio. Furthermore, the curing agent may form a complex with a solvent or the like. It may also form a polymer. The curing agent may be completely decomposed, partially decomposed, or not decomposed at all after the manufacture of the laminate.

[0067] <Particularly Preferred Embodiments> Particularly preferred embodiments will be described below.

[0068] (a) A method of selecting an epoxy resin as the main component resin of the above-mentioned adhesive and introducing a molecular skeleton that exhibits flexibility into the main chain of the epoxy resin. Methods for introducing the molecular skeleton include using epoxy resin precursors having skeletons such as polyoxyalkylene, acrylic, silicone, polyester, and urethane. Furthermore, commercially available flexible epoxy resin precursors can be used as such epoxy resin precursors. Specifically, for example, jER871 (manufactured by Mitsubishi Chemical Corporation), jER872 (manufactured by Mitsubishi Chemical Corporation), YX7105 (manufactured by Mitsubishi Chemical Corporation), YL7175-1000 (manufactured by Mitsubishi Chemical Corporation), YL7410 (manufactured by Mitsubishi Chemical Corporation), urethane-modified epoxy resin, CTBN-modified BPA-type epoxy resin, EO-modified BPA-type epoxy resin, EPICLON EXA-4816 (manufactured by DIC Corporation), EPICLON EXA-4850 (manufactured by DIC Corporation), EPICLON TSR-960 (manufactured by DIC Corporation), EPICLON TSR-601 (manufactured by DIC Corporation), EPICLON Examples include 1650-75MPX ​​(manufactured by DIC Corporation), Rikaresin BEO-60E (manufactured by Shin-Nippon Rika Co., Ltd.), Rikaresin BEO-20E (manufactured by Shin-Nippon Rika Co., Ltd.), and Rikaresin DME-100 (manufactured by Shin-Nippon Rika Co., Ltd.).

[0069] (b) A method in which epoxy resin is selected as the main component resin of the above adhesive, and a plasticizer or reactive diluent is added. The plasticizer used in the method described in (b) above is not particularly limited, but examples include ester compounds synthesized from acids and alcohols. Examples of acids that can be used include phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, azelaic acid, maleic acid, itaconic acid, phosphoric acid, citric acid, epoxycyclohexyldicarboxylic acid, and benzoic acid. Furthermore, by introducing epoxy groups into the plasticizer, the bleed-out of the plasticizer can be suppressed, and a uniform composition can be produced. Examples of such compounds include Sansosizer E-PS, Sansosizer E-PO, Sansosizer E-4030, Sansosizer E-6000, Sansosizer E-2000H, Sansosizer E-9000H (all manufactured by Shin-Nippon Rika Co., Ltd.), epoxidized soybean oil, epoxidized linseed oil, epoxidized fatty acid octyl ester, epoxidized fatty acid alkyl ester, and ADEKA (manufactured by ADEKA Corporation).

[0070] Examples of reactive diluents used in the method described in (b) above include the YED series from Mitsubishi Chemical Corporation (YED111N, YED111AN, YED122, YED188, YED216M, YED216D, etc.), PG-207N (manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), NeoTote S (manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), Denacol series (manufactured by Nagase ChemteX Corporation), Celoxide 2021P, 2081, 2000 (manufactured by Daicel Corporation), etc.

[0071] (c) A method in which epoxy resin is selected as the main component resin of the above adhesive, and elastomers or thermoplastic resins are added as modifiers. Examples of elastomers and thermoplastic resins to be added as modifiers in the method described in (c) above include polyester, acrylic-modified epoxy resin, polyamide, epoxidized vegetable oil, polyvinyl butyral, polyvinyl acetal, modified polyvinyl butyral, modified polyvinyl acetal, silicone oil, MQ resin, etc.

[0072] Of the methods exemplified above, (a) a method of introducing a molecular skeleton that exhibits flexibility into the main chain of the epoxy resin is preferred to adjust the storage modulus of the epoxy resin to a desired range.

[0073] <Other components in adhesives> In this embodiment, the adhesive may, in addition to the epoxy resin described above, optionally contain other resins, fillers, dispersants, surfactants, plasticizers, antioxidants, pigments, coupling agents, diluents, flexibility enhancers, dispersants, wetting agents, colorants, pigments, UV absorbers, light stabilizers such as hindered amine-based light stabilizers, defoaming agents, release agents, flow regulators, solvents, and other additives. The amount of these additives is preferably 20 parts by mass or less per 100 parts by mass of the total of the epoxy resin precursor and the curing agent. On the other hand, there is no particular lower limit, but it is preferably 0.1 parts by mass or more.

[0074] (Filler) The adhesive in this embodiment may contain a filler. Examples of fillers include powdered reinforcing agents and other fillers. Specific examples of fillers include metal oxides such as aluminum oxide and magnesium oxide; metal carbonates such as calcium carbonate and magnesium carbonate; silicon compounds such as diatomaceous earth powder, basic magnesium silicate, calcined clay, fine silica powder, and fused silica; metal hydroxides such as aluminum hydroxide; and kaolin, mica, quartz powder, graphite, carbon black, carbon nanotubes, molybdenum disulfide, boron nitride, silicon nitride, and aluminum nitride. Furthermore, fibrous fillers may be used as the above-mentioned fillers. Examples of fibrous fillers include glass fibers, ceramic fibers, carbon fibers, alumina fibers, silicon carbide fibers, boron fibers, aramid fibers, cellulose nanofibers, and cellulose nanocrystals. Furthermore, organic or inorganic fiber cloths or nonwoven fabrics can be used as fillers. Furthermore, the fillers exemplified above may be used after their surface has been treated with a silane coupling agent, titanate-based coupling agent, aluminate-based coupling agent, or primer.

[0075] The laminate in this embodiment mitigates strain caused by the difference in the coefficient of linear expansion between the first and second materials by adjusting the adhesive components, the storage modulus of elasticity of the adhesive layer, and its thickness. This differs in concept from conventional techniques that involve adding fillers to the adhesive to cause thermal expansion and fill the gaps between materials. Furthermore, while the present invention can reduce the warping of the laminate without reducing the adhesive strength, it is difficult to achieve both this adhesive strength and the effect of reducing the warping of the laminate with conventional techniques. Therefore, the present invention can be particularly suitably used when it is desired to achieve both adhesive strength and the effect of reducing the warping of the laminate, and when fillers such as fillers or thermally expandable fine particles are not included.

[0076] (Dispersant) The adhesive in this embodiment may contain a dispersant. A dispersant is a compound that uniformly disperses fillers in the adhesive and in the laminate after production. Examples of the above dispersants include polysiloxane compounds and their salts such as methylhydrogenpolysiloxane, polymethoxysilane, dimethylpolysiloxane, and dimethicone PEG-7 succinate; silane compounds such as methyldimethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, dichlorophenylsilane, chlorotrimethylsilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, dodecyltrichlorosilane, octadecyltrimethoxysilane, octadecyltrichlorosilane, trifluoropropyltrimethoxysilane, vinyltrimethoxysilane, and 3-acryloxypropyltrimethoxysilane. Examples include organosilicon compounds (such as 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, hexamethyldisiloxane, 1,1,1,3,3,3-hexamethyldisilazane, 3-carboxypropyltrimethyltrimethoxysilane, etc.); carboxylic acid compounds such as formic acid, acetic acid, butyric acid, lauric acid, stearic acid, oleic acid, and 6-hydroxyhexanoic acid; organophosphorus compounds such as lauryl ether phosphate and trioctylphosphine; amine compounds such as dimethylamine, tributylamine, trimethylamine, cyclohexylamine, ethylenediamine, and polyethyleneimine; carboxylic acid amine compounds; and phosphate amine compounds. Note that a carboxylate amine compound refers to a compound having both a carboxyl group and an amino group, while a phosphate amine compound refers to a compound having both a phosphate group and an amino group. The adhesive in this embodiment may use one of the dispersants exemplified above alone, or two or more may be used in any combination and ratio. Surfactants, as described later, may also function as dispersants. Furthermore, the dispersant may be completely decomposed, partially decomposed, or not decomposed at all after the manufacture of the laminate.

[0077] (Surfactants) The adhesive in this embodiment may contain a surfactant. By including a surfactant, it is possible to prevent the occurrence of dents or uneven drying in the laminate during the manufacturing of the laminate due to the adhesion of minute bubbles or foreign matter. Furthermore, surfactants can improve the wettability of adhesives. There are no particular restrictions on the surfactant used, and any known surfactant (cationic surfactant, anionic surfactant, nonionic surfactant) can be used. Among these, silicon-based surfactants, fluorine-based surfactants, and acetylene glycol-based surfactants are preferred. Specific examples of surfactants include the nonionic surfactant Triton X100 (manufactured by Dow Chemical), the fluorine-based surfactant Zonil FS300 (manufactured by DuPont), the silicon-based surfactants BYK-310, BYK-320, and BYK-345 (manufactured by Bic Chemie), and the acetylene glycol-based surfactants Surfinol 104 and Surfinol 465 (manufactured by Air Products), Olfin EXP4036, and Olfin EXP4200 (manufactured by Nisshin Chemical Industry Co., Ltd.). The adhesive in this embodiment may use one of the surfactants exemplified above alone, or two or more may be used in any combination and ratio. Furthermore, the surfactant may be completely decomposed, partially decomposed, or not decomposed at all after the manufacturing of the laminate.

[0078] <<Sheet-type adhesive>> The adhesive layer in this embodiment may be a sheet-type adhesive. The sheet-like adhesive may be formed by providing the adhesive on a base film, but when laminating the sheet-like adhesive between layers of the first and second materials, the base film is peeled off before use. Furthermore, the sheet-like adhesive may be formed by impregnating a support with the adhesive.

[0079] When providing an adhesive on a base film, as the base film, for example, a release-treated PET film such as silicone or melamine, a polyethylene-based film, a polypropylene-based film, a fluorine-based film, a polyimide film, etc. can be used.

[0080] Also, when impregnating a support with an adhesive, as the support, for example, a non-woven fabric, a porous material, etc. can be used, and among them, a non-woven fabric is preferable. The density of the support is preferably 0.05 g / cm 3 or more from the viewpoints of suppressing resin flow during pressurization in laminate production, retaining resin with a sheet-like adhesive, and improving adhesiveness due to the rigidity of the adhesive layer, 0.08 g / cm 3 or more is more preferable, and 0.1 g / cm 3 or more is even more preferable. Also, from the viewpoints of improving resin impregnation in the sheet-like adhesive, improving lightness in the laminate, and improving interfacial adhesion, it is preferably 1.0 g / cm 3 or less, more preferably 0.9 g / cm 3 or less, and even more preferably 0.8 g / cm 3 or less.

[0081] The thickness of the sheet-like adhesive is preferably 0.1 to 2.0 mm. By the thickness of the sheet-like adhesive being within the above numerical range, the adhesiveness between the first material and the second material can be made good while reducing the warp of the laminate. Among them, the thickness of the sheet-like adhesive is preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. Also, since the tensile shear adhesion strength of the laminate improves as the thickness of the adhesive layer becomes thinner, the thickness of the sheet-like adhesive is preferably 1.8 mm or less, more preferably 1.6 mm or less, and even more preferably 1.4 mm or less.

[0082] (3) Other Layers The laminate in the present embodiment may have other layers in addition to the first material, the second material, and the adhesive layer. For example, the laminate may further include a third material having a different coefficient of thermal expansion from the first and second materials, and may be laminated in the order of first material / first adhesive layer / second material / second adhesive layer / third material. In this case, it is sufficient if either the first adhesive layer or the second adhesive layer contains an adhesive with a warpage reduction index of 30 or higher, and it is preferable that both the first adhesive layer and the second adhesive layer contain an adhesive with a warpage reduction index of 30 or higher. The first adhesive layer and the second adhesive layer may be the same or different.

[0083] 2. Method for manufacturing laminates A method for manufacturing a laminate (hereinafter also referred to as "the laminate 1") in one embodiment of the present invention includes a sheet molding step of forming an adhesive having a warpage reduction index of 30 or more into a sheet to obtain a sheet-like adhesive; a lamination step of preparing a first material and a second material having different coefficients of linear expansion, and laminating a sheet-like adhesive between layers of the first material and the second material; and a curing step of curing the adhesive by heating. Furthermore, a method for manufacturing a laminate in another embodiment of the present invention (hereinafter referred to as "Laminate 2") includes: preparing a first material and a second material having different coefficients of thermal expansion; a direct coating step of directly applying the above-mentioned adhesive having a warpage reduction index of 30 or more to at least one of the first material and the second material to form an adhesive layer; a lamination step of laminating the first material and the second material via the adhesive layer; and a curing step of curing the adhesive by heating. The following describes each step.

[0084] (1) Sheet forming process In this sheet molding process, the adhesive is molded into a sheet to obtain a sheet-like adhesive. Methods for forming a sheet include laminating or coating an adhesive onto a base film to obtain a laminate of base film / adhesive / base film. Specifically, these methods include using sheet forming equipment such as extrusion lamination with T-dies, calender rolls, and double belt presses, as well as methods such as comma coating, gravure coating, reverse coating, knife coating, dip coating, spray coating, air knife coating, spin coating, roll coating, print coating, dip coating, slide coating, curtain coating, die coating, casting, bar coating, and extrusion coating.

[0085] In the sheet molding process described above, an impregnation step may be performed in which the adhesive is impregnated into the support. The impregnation method for the adhesive in the impregnation process can be any known method. Examples of such impregnation methods include a lamination method in which the adhesive applied to the base film in the above sheet molding process is laminated with a support so that it forms base film / adhesive / support / adhesive / base film, and then impregnated using a vacuum laminator, calender roll, double belt press, etc., or a dip-nip method, kiss coat method, spray method, curtain coat method, etc., in which the adhesive is directly impregnated into the support. The thickness of the support and the amount of adhesive impregnated into the support are preferably adjusted so that the thickness of the sheet-like adhesive layer is 0.1 to 2.0 mm.

[0086] (2) Direct coating process In this direct coating step, an adhesive is applied to at least one of the first material and the second material. The adhesive may be applied to only one of the first material and the second material, or to both the first material and the second material. The method for applying the adhesive may be any known method. Examples of such application methods include the comma coating method, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, print method, dip method, slide coating method, curtain coating method, die coating method, casting method, bar coating method, extrusion coating method, and the like. The amount of adhesive applied is preferably adjusted to such an amount that the thickness of the adhesive layer is 0.1 to 2.0 mm.

[0087] (3)Lamination process In the lamination process for this laminate 1, a sheet-like adhesive is laminated and bonded between the layers of the first material and the second material. The lamination method in this laminate 1 may be a known method. For example, when using a laminate of base film / adhesive / base film as a sheet-like adhesive, one method is to peel off one base film, place the adhesive surface on the first material and adhere it, then peel off the other base film, place the second material on the adhesive surface and adhere it.

[0088] In the lamination process for the laminate 2, the first material and the second material are laminated and bonded together via the adhesive layer. The lamination method in this laminate 2 may be a known method. For example, if an adhesive is applied to the surface of the second material, one method is to place the first material on the adhesive-coated surface of the second material with the second material as the bottom layer, and then bond the first material and the second material together.

[0089] (4) Curing process In this curing process, the laminate 1 or 2 is heated to cure the adhesive. Conditions such as the type of curing agent, heating temperature, and time are appropriately selected according to the type of resin contained in the adhesive. For example, reactivity can be increased by using low molecular weight epoxy resin precursors or highly active curing agents, using two or more curing agents in combination, high-temperature heating, or long-time heating. The heating conditions are also influenced by the curing agent used, but are usually 30°C or higher, preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher. On the other hand, the heating conditions are usually 400°C or lower, preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. When the curing temperature is within the above range, it is easy to obtain a high-quality laminate in a short time and is also effective in reducing warping.

[0090] 3.Applications The laminate of the present invention is a laminate with minimal warping, formed by laminating multiple materials with different coefficients of thermal expansion. Therefore, it can be suitably used as an exterior material for automobiles, aircraft, and other vehicles where improved strength and weight reduction are required, and where relatively large material areas are necessary. [Examples]

[0091] The present invention will be specifically described below with reference to examples. However, the present invention is not limited in any way by the following examples. The measurement and evaluation methods used in this invention are as follows.

[0092] <Average storage modulus> Each adhesive prepared in the examples and comparative examples was applied to a Teflon® plate to a thickness of 0.5 mm, and the adhesive was cured by heating in a hot air drying oven at 180°C for 20 minutes. After natural cooling, the cured adhesive was cut into pieces 5 mm wide x 10 mm long to prepare test specimens. The storage modulus of the test specimens was measured using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd. "DVA 225") and a tensile jig at a measurement temperature of 25 to 180°C, a frequency of 10 Hz, and a heating rate of 10°C / min. The average value of the storage modulus at 25 to 180°C was calculated by dividing the storage modulus at 25 to 180°C by the number of measurement points.

[0093] <Amount of warping (CAE)> Aluminum plate measuring 25mm wide x 100mm long x 1.6mm thick (coefficient of linear expansion: 23 x 10 -6 [1 / K], Young's modulus: 70 GPa, Poisson's ratio: 0.3) and SPCC (cold-rolled steel sheet) with a width of 25 mm x length of 100 mm x thickness of 1.6 mm (coefficient of linear expansion: 16 x 10 -6 The analytical model was created by dividing a laminate into finite elements, in which the adhesives prepared in the examples and comparative examples were applied to a thickness of 0.1 mm between [1 / K], Young's modulus: 200 GPa, and Poisson's ratio: 0.3. The center of the SPCC (cold-rolled steel sheet) was fixed, and the displacement (warpage (A)) of the edges of the laminate was calculated using a simulation (finite element method structural analysis) with the CAE (Computer-Aided Engineering) software "ANSYS" when the temperature was changed from 180°C to 25°C. Using a similar method, the thickness of the adhesive was changed to 0.2 mm, 0.4 mm, and 0.7 mm, and the amount of warping (A) for each was calculated using CAE software.

[0094] <Calibration Reduction Index (CAE)> Using the same method as described above for <Warpage Amount (CAE)>, the warpage amount (B) when no adhesive layer is provided between the aluminum plate and SPCC (cold-rolled steel sheet) was calculated using CAE software. From this warpage amount (B) and the warpage amount (A) calculated in <Warpage Amount (CAE)> above, the warpage reduction index was determined based on the following formula (1). Warping reduction index = 100 - {Warping amount (A) / Warping amount (B)} × 100 ... (1)

[0095] <Reduction Efficiency> The warping reduction efficiency of each adhesive prepared in the examples and comparative examples was determined according to the following criteria. ○(good): The warp reduction index is 30 or higher when the adhesive thickness is 0.7mm. × (poor): The warp reduction index is less than 30 when the adhesive thickness is 0.7 mm.

[0096] <Tensile shear bond strength> The tensile shear bond strength was measured using the method described below, in accordance with the method specified in JIS K 6850. Two pieces of stainless steel (SUS) measuring 25 mm wide x 100 mm long x 1.6 mm thick were used. On one of the SUS pieces, the respective adhesives prepared in the examples and comparative examples were applied to a 25 mm wide x 12.5 mm long area to a thickness of 0.2 mm. The SUS pieces were pressed together using clamps through the adhesive-coated surfaces, and the adhesive was cured by heating at 180°C for 20 minutes to prepare test specimens. The tensile shear adhesive strength of each test specimen was measured using a tensile testing machine (Shimadzu Corporation "Autograph AG-X") at 23°C, 50% RH, and a speed of 5 mm / min.

[0097] <Amount of warping (measured value)> Aluminum plates measuring 25 mm wide x 100 mm long x 1.6 mm thick (A5052P, manufactured by Nippon Test Panel Co., Ltd.) and steel plates measuring 25 mm wide x 140 mm long x 1.6 mm thick (SPCC~SB (cold-rolled steel sheet) as described in JIS G 3141, manufactured by Nippon Test Panel Co., Ltd.) were used as standard test specimens. The adhesives prepared in the examples and comparative examples were uniformly applied to the entire surface of the aluminum plate to a thickness of 0.2 mm. A steel plate was placed on top and clamped to create a laminate. The laminate was heated in a hot air drying oven at 180°C for 20 minutes to cure the adhesive, then allowed to cool naturally. The clamps were removed, and the laminate was placed on top of the SUS (stainless steel) with the aluminum plate facing downwards. The total thickness of the laminate and the SUS was measured at four corners and one center point using an ABS Digimatic Indicator (Mitutoyo "ID-SX"), and the amount of warping was calculated based on the following formula (2). Curvature = (Thickness at the center point) - (Average thickness at the four corner points) ... (2)

[0098] <Amount of curvature (assessment)> The measured values ​​of the above warp were evaluated according to the following criteria. ○ (very good): Curvature less than 0.3mm △ (good): Curvature of 0.3mm or more but less than 0.5mm × (poor): Curvature of 0.5 mm or more

[0099] [Manufacturing of epoxy resin precursors] The epoxy resin precursors used in Examples 1 to 4 were prepared as follows.

[0100] <Production of epoxy resin precursor (α)> First, 141.8 parts by mass (hereinafter abbreviated as "parts") of 1,6-hexanediol preheated to 45°C and 0.51 parts of ethyl boron trifluoride were charged into a 1L glass flask equipped with a stirrer, dropping funnel, and thermometer, and heated to 80°C. 244.3 parts of epichlorohydrin were added dropwise over time, ensuring the temperature did not exceed 85°C. The mixture was aged for 1 hour while maintaining a temperature of 80-85°C, and then cooled to 45°C. 528.0 parts of a 22% by mass aqueous sodium hydroxide solution were added, and the mixture was heated to 45°C and vigorously stirred for 4 hours. The mixture was cooled to room temperature (25°C) to separate and remove the aqueous phase, and then heated under reduced pressure to remove unreacted epichlorohydrin and water, yielding 283.6 parts of crude 1,6-hexanediol diglycidyl ether. This crude 1,6-hexanediol diglycidyl ether was purified by distillation in an Oldasho distillation column (15 stages), and the fraction obtained at a pressure of 1300 Pa and a temperature of 170-190°C was selected as the main fraction, yielding 127.6 parts of 1,6-hexanediol diglycidyl ether. The diglycidyl purity, total chlorine content, and epoxy equivalent of this 1,6-hexanediol diglycidyl ether were as follows. Diglycidyl purity: 97% by mass Total chlorine content: 0.15% by mass Epoxy equivalent: 116g / eq

[0101] 100 parts of the obtained bifunctional epoxy compound (1,6-hexanediol diglycidyl ether) and 53.5 parts of bisphenol F (phenolic hydroxyl group equivalent: 100 g / eq), along with 0.08 parts of ethyltriphenylphosphonium iodide (30% by mass methyl cellosolve solution) as a polymerization initiator, were placed in a pressure-resistant reaction vessel, and the polymerization reaction was carried out at 165-170°C for 5 hours under a nitrogen gas atmosphere to obtain epoxy resin precursor (α). The epoxy equivalent of the obtained epoxy resin precursor (α) was 500 g / eq, and the number-average molecular weight was 1,600.

[0102] <Example 1> In a poly container, 66 g of epoxy resin precursor (α) and 19 g of the phenol novolac type epoxy compound "jER152" (manufactured by Mitsubishi Chemical Corporation) were introduced. Then, 15 g of the high molecular weight saturated copolymer polyester resin "Nichigo Polyester LP-011" (manufactured by Mitsubishi Chemical Corporation) was added as a modifying resin. The mixture was heated to 100°C and mixed, followed by vacuum stirring and degassing for 5 minutes. The epoxy resin precursor and the modified resin were preheated to 70°C before mixing. After cooling to 60°C, 8g of dicyandiamide "DICY7" (manufactured by Mitsubishi Chemical Corporation) and 2g of dichlorophenyldimethylurea "DCMU" (manufactured by Nacalai Tesque Corporation) were added as latent curing agents, and the mixture was degassed by vacuum stirring for 5 minutes to prepare an adhesive sample.

[0103] <Example 2> In a plastic container, 64 g of epoxy resin precursor (α) and 16 g of the phenol novolac type epoxy compound "jER152" (manufactured by Mitsubishi Chemical Corporation) were introduced. Then, 20 g of the acrylic modified epoxy resin "NS7008" (manufactured by Mitsubishi Chemical Corporation) was added as the modifying resin, and the mixture was heated to 100°C and mixed, followed by vacuum stirring and degassing for 5 minutes. The epoxy resin precursor and the modified resin were preheated to 70°C before mixing. After cooling to 60°C, 8g of dicyandiamide "DICY7" (manufactured by Mitsubishi Chemical Corporation) and 2g of dichlorophenyldimethylurea "DCMU" (manufactured by Nacalai Tesque Corporation) were added as latent curing agents, and the mixture was degassed by vacuum stirring for 5 minutes to prepare an adhesive sample.

[0104] <Example 3> Adhesive samples were prepared in the same manner as in Example 2, except that the amount of acrylic-modified epoxy resin "NS7008" (manufactured by Mitsubishi Chemical Corporation) added was changed as shown in Table 1.

[0105] <Example 4> Adhesive samples were prepared in the same manner as in Example 2, except that the amounts of epoxy resin precursor (α) and "jER152" (manufactured by Mitsubishi Chemical Corporation) were changed as shown in Table 1.

[0106] <Example 5> In a plastic container, 20g of bisphenol A type epoxy compound "jER828" (manufactured by Mitsubishi Chemical Corporation), 20g of bisphenol A type epoxy compound "jER1001" (manufactured by Mitsubishi Chemical Corporation), 40g of "ADEKA Resin EPR-1630" (manufactured by ADEKA Corporation), a mixture of 80-90% by mass of CTBN-modified epoxy resin and 10-20% by mass of bisphenol A type epoxy compound, and 20g of "KaneAce® MX-154" (manufactured by Kaneka Corporation), a mixture of 55-65% by mass of MBS polymer (core-shell acrylic rubber) and 35-45% by mass of bisphenol A type epoxy compound were added, and the mixture was heated to 100°C and then vacuum stirred and degassed for 5 minutes. After cooling to 60°C, 8g of dicyandiamide "DICY7" (manufactured by Mitsubishi Chemical Corporation) and 2g of dichlorophenyldimethylurea "DCMU" (manufactured by Nacalai Tesque Corporation) were added as latent curing agents, and the mixture was degassed by vacuum stirring for 5 minutes to prepare an adhesive sample.

[0107] <Comparative Example 1> 80g of bisphenol A type epoxy compound "jER828" (manufactured by Mitsubishi Chemical Corporation) as an epoxy resin precursor and 20g of epoxidized polybutadiene "Epolid PB3600" (manufactured by Daicel Corporation) as a modified resin were introduced into a plastic container. After heating and mixing at 100°C, the mixture was vacuum stirred and degassed for 5 minutes. The epoxy resin precursor and modified resin were preheated to 70°C before mixing. After cooling to 60°C, 8g of dicyandiamide "DICY7" (manufactured by Mitsubishi Chemical Corporation) and 2g of dichlorophenyldimethylurea "DCMU" (manufactured by Nacalai Tesque Corporation) were added as latent curing agents, and the mixture was degassed by vacuum stirring for 5 minutes to prepare an adhesive sample.

[0108] <Comparative Example 2> Adhesive samples were prepared in the same manner as in Comparative Example 1, except that the amounts of bisphenol A type epoxy resin "jER828" (manufactured by Mitsubishi Chemical Corporation) and epoxidized polybutadiene "Epolid PB3600" (manufactured by Daicel Corporation) added as epoxy resin precursors were changed as shown in Table 1.

[0109] <Comparative Example 3> As an adhesive sample, we used "Scotch-Weld SW-2214" (manufactured by 3M), a one-component epoxy resin-based curing adhesive.

[0110] The adhesives obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were measured and evaluated according to the measurement and evaluation methods described above, and the results are shown in Table 1 below.

[0111] [Table 1]

[0112] The adhesives in Examples 1 to 5 had a warp reduction index of 30 or higher when the thickness of the adhesive was 0.7 mm, and the measured amount of warp was 0.5 mm or less. Therefore, it was found that the laminates using the adhesives of Examples 1 to 5 can reduce warping of the laminate after the adhesive has been heat-cured. Furthermore, the adhesives in Examples 1 to 5 had a tensile shear adhesive strength of 10 MPa or more, and the adhesion between the first and second materials was also good. This is thought to be due to the fact that the epoxy resins contained in the adhesives of Examples 1 to 5 have both an aliphatic skeleton and a skeleton derived from aromatic compounds, resulting in flexibility from the aliphatic skeleton and rigidity and metal adhesion from the aromatic compound portion.

[0113] Furthermore, the adhesives in Examples 1 to 3 had a warp reduction index of 40 or higher when the adhesive thickness was 0.7 mm, and the measured amount of warp was 0.3 mm or less. Therefore, it was found that the laminates using the adhesives of Examples 1 to 3 can further reduce the warping of the laminate after the adhesive has been heat-cured. Furthermore, the adhesives in Examples 2 to 5 had an average storage modulus of 80 MPa or higher at 25 to 180°C, resulting in a tensile shear adhesive strength of 20 MPa or higher, and particularly good adhesion between the first and second materials.

[0114] Furthermore, the adhesives from Examples 1 to 3 were applied to a silicone-release-treated PET film "MRF75" as a base film, and another base film was inserted from the other side. A sheet-like adhesive (0.8 mm thick) was then produced using a laminator. Even when using the sheet-like adhesive, the same level of warping reduction efficiency was achieved, and it also exhibited superior tensile shear adhesive strength.

[0115] Furthermore, the adhesives of Examples 1-3 were applied to a glass fiber nonwoven fabric (density 0.16 g / cm³). 3 When using a sheet-type adhesive (0.8 mm thick) impregnated with Olivest Co., Ltd. product number "RAP-110", equivalent warping reduction efficiency was achieved, and it also exhibited superior tensile shear adhesive strength.

[0116] On the other hand, the adhesives in Comparative Examples 1 to 3 used a common epoxy resin (bisphenol A diglycidyl ether: BPADGE) as an epoxy resin precursor, and their average storage modulus at 25 to 180°C exceeded 400 MPa, resulting in a warp reduction index of less than 30 when the adhesive thickness was 0.7 mm. Consequently, the measured warp amount exceeded 0.5 mm, indicating an insufficient warp reduction effect.

[0117] These results show that by laminating multiple materials with different coefficients of thermal expansion using an adhesive that has a warp reduction index of 30 or higher when the adhesive thickness is 0.7 mm, the warp of the laminate after heat curing of the adhesive can be reduced. Therefore, the laminate using the adhesive of the example is suitable as an exterior material for automobiles.

[0118] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

Claims

1. A laminate comprising a first material / adhesive layer / second material, The first material and the second material have different coefficients of thermal expansion. The adhesive layer is a laminate comprising an adhesive whose warpage reduction index shown in the following formula (1) is 30 or higher, and whose tensile shear adhesive strength calculated by the following measurement method is 10 MPa or higher. <Warping Reduction Index> The warpage reduction index is determined by the following method. The analytical model is a laminate consisting of an aluminum plate measuring 25 mm wide x 100 mm long x 1.6 mm thick and SPCC (cold-rolled steel sheet), with an adhesive layer 0.7 mm thick applied between them, which is then divided into finite elements. The center of the SPCC side is fixed, and the displacement of the ends of the laminate (warpage (A)) is calculated using CAE software when the temperature is changed from 180°C to 25°C. Using a similar method, the amount of warpage (B) when no adhesive layer is provided between the aluminum sheet and the SPCC (cold-rolled steel sheet) is calculated using CAE software, and the warpage reduction index is determined based on the following formula (1). Warping reduction index = 100 - {Warping amount (A) / Warping amount (B)} × 100 ... (1) <Tensile shear adhesive strength> Two pieces of SUS (stainless steel) measuring 25 mm wide x 100 mm long x 1.6 mm thick are used. Adhesive is applied to one of the SUS pieces in an area measuring 25 mm wide x 12.5 mm long, to a thickness of 0.05 to 0.20 mm. The SUS pieces are then pressed together using clamps, with the adhesive-coated surface between them, and heated at 180°C for 20 minutes to cure the adhesive, thereby creating a test specimen. The tensile shear adhesive strength of the test specimen will be measured using a tensile testing machine (Shimadzu Corporation's "Autograph AG-X") at 23°C and 50% RH at a speed of 5 mm / min.

2. The laminate according to claim 1, wherein the average storage modulus of the adhesive layer at 25 to 180°C is 1 to 400 MPa.

3. A laminate comprising a first material / adhesive layer / second material, The first material and the second material have different coefficients of thermal expansion. A laminate in which the average storage modulus of the adhesive layer at 25 to 180°C is 1 to 400 MPa, and the tensile shear adhesive strength of the adhesive layer calculated by the following measurement method is 10 MPa or more. <Tensile shear adhesive strength> Two pieces of SUS (stainless steel) measuring 25 mm wide x 100 mm long x 1.6 mm thick are used. Adhesive is applied to one of the SUS pieces in an area measuring 25 mm wide x 12.5 mm long, to a thickness of 0.05 to 0.20 mm. The SUS pieces are then pressed together using clamps, with the adhesive-coated surface between them, and heated at 180°C for 20 minutes to cure the adhesive, thereby creating a test specimen. The tensile shear adhesive strength of the test specimen will be measured using a tensile testing machine (Shimadzu Corporation's "Autograph AG-X") at 23°C and 50% RH at a speed of 5 mm / min.

4. The laminate according to any one of claims 1 to 3, wherein the thickness of the adhesive layer is 0.1 to 2.0 mm.

5. The laminate according to any one of claims 1 to 4, wherein the adhesive layer mainly consists of epoxy resin.

6. The laminate according to any one of claims 1 to 5, wherein the adhesive layer contains a bifunctional epoxy compound having an aliphatic skeleton and an aromatic skeleton.

7. The laminate according to any one of claims 1 to 6, wherein the adhesive layer is composed of a sheet-like adhesive.

8. The laminate according to claim 7, wherein the sheet-like adhesive is obtained by impregnating a support with the adhesive, and the support is a nonwoven fabric.

9. The density of the support is 0.05 to 1.00 g / cm³ ３ The laminate according to claim 7 or 8.

10. The laminate according to any one of claims 1 to 9, wherein the first material includes aluminum.

11. The laminate according to any one of claims 1 to 10, wherein the second material contains iron.

12. Automotive exterior material using the laminate described in any one of claims 1 to 11.

13. A sheet molding process to obtain a sheet-like adhesive, comprising: forming an adhesive into a sheet shape using the following formula (1) which has a warpage reduction index of 30 or more and a tensile shear adhesive strength of 10 MPa or more calculated by the following measurement method; A lamination step is to prepare a first material and a second material having different coefficients of thermal expansion, and to laminate the sheet-like adhesive between the layers of the first material and the second material, A method for manufacturing a laminate, comprising a curing step of curing the adhesive by heating. <Warping Reduction Index> The warpage reduction index is determined by the following method. The analytical model is a laminate consisting of an aluminum plate measuring 25 mm wide x 100 mm long x 1.6 mm thick and SPCC (cold-rolled steel sheet), with an adhesive layer 0.7 mm thick applied between them, which is then divided into finite elements. The center of the SPCC side is fixed, and the displacement of the ends of the laminate (warpage (A)) is calculated using CAE software when the temperature is changed from 180°C to 25°C. Using a similar method, the amount of warpage (B) when no adhesive layer is provided between the aluminum sheet and the SPCC (cold-rolled steel sheet) is calculated using CAE software, and the warpage reduction index is determined based on the following formula (1). Warping reduction index = 100 - {Warping amount (A) / Warping amount (B)} × 100 ... (1) <Tensile shear adhesive strength> Two pieces of SUS (stainless steel) measuring 25 mm wide x 100 mm long x 1.6 mm thick are used. Adhesive is applied to one of the SUS pieces in an area measuring 25 mm wide x 12.5 mm long, to a thickness of 0.05 to 0.20 mm. The SUS pieces are then pressed together using clamps, with the adhesive-coated surface between them, and heated at 180°C for 20 minutes to cure the adhesive, thereby creating a test specimen. The tensile shear adhesive strength of the test specimen will be measured using a tensile testing machine (Shimadzu Corporation's "Autograph AG-X") at 23°C and 50% RH at a speed of 5 mm / min.

14. The method for manufacturing a laminate according to claim 13, wherein the sheet molding step includes a step of impregnating the adhesive into a support to obtain a sheet-like adhesive.

15. A direct coating step is to prepare a first material and a second material having different coefficients of thermal expansion, and to directly apply an adhesive to at least one of the first material and the second material, wherein the adhesive has a warpage reduction index of 30 or more as shown in the following formula (1) and a tensile shear adhesive strength of 10 MPa or more as calculated by the following measurement method, thereby forming an adhesive layer. A method for manufacturing a laminate, comprising: a lamination step of laminating the first material and the second material via the adhesive layer; and a curing step of curing the adhesive by heating. <Warping Reduction Index> The warpage reduction index is determined by the following method. The analytical model is a laminate consisting of an aluminum plate measuring 25 mm wide x 100 mm long x 1.6 mm thick and SPCC (cold-rolled steel sheet), with an adhesive layer 0.7 mm thick applied between them, which is then divided into finite elements. The center of the SPCC side is fixed, and the displacement of the ends of the laminate (warpage (A)) is calculated using CAE software when the temperature is changed from 180°C to 25°C. Using a similar method, the amount of warpage (B) when no adhesive layer is provided between the aluminum sheet and the SPCC (cold-rolled steel sheet) is calculated using CAE software, and the warpage reduction index is determined based on the following formula (1). Warping reduction index = 100 - {Warping amount (A) / Warping amount (B)} × 100 ... (1) <Tensile shear adhesive strength> Two pieces of SUS (stainless steel) measuring 25 mm wide x 100 mm long x 1.6 mm thick are used. Adhesive is applied to one of the SUS pieces in an area measuring 25 mm wide x 12.5 mm long, to a thickness of 0.05 to 0.20 mm. The SUS pieces are then pressed together using clamps, with the adhesive-coated surface between them, and heated at 180°C for 20 minutes to cure the adhesive, thereby creating a test specimen. The tensile shear adhesive strength of the test specimen will be measured using a tensile testing machine (Shimadzu Corporation's "Autograph AG-X") at 23°C and 50% RH at a speed of 5 mm / min.

Images