JP2009173023A - Sheet for laser joining and joining method using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet for laser joining usable for joining various materials, with which high joint strength can be obtained by a simple operation. <P>SOLUTION: This sheet 3 for laser joining is for joining a first member 2 comprising a material having transmissivity to laser light L and a second member 4 comprising a material identical to or different from the first member 2 by a laser welding method, which is sandwiched between the first member 2 and the second member 4 prior to irradiation of laser light L. The sheet 3 for laser joining comprises a multilayer sheet having a first polymer layer 5 to be in contact with the first member 2 and a second polymer layer 7 to be in contact with the second member 4, and preferably has at least one core layer 6 between the first polymer layer 5 and the second polymer layer 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, in order to join a first member made of a material that is transparent to laser light and a second member made of the same material as or different from the first member by a laser welding method, The present invention relates to a laser bonding sheet that is sandwiched between a first member and a second member in advance. The present invention also relates to a joining method and a joined product using such a laser joining sheet.

  As a method for joining members made of different materials such as resins or materials other than resin and resin, a joining method by laser light irradiation (so-called laser welding method) has been used. This is because a transparent member that is transparent to laser light and a non-transparent member that is not transparent to laser light are brought into contact with each other, and then the laser light is irradiated from the transparent member side and transmitted. This is a method in which the contact portion between the permeable member and the non-permeable member is heated and melted to integrally bond the two. In such a method, it is necessary to use a combination of laser-transmitting and non-transmitting materials, or it is not possible to bond materials having low affinity to each other well. It was restricted. Moreover, even if it was able to join, the intensity | strength and reliability were not enough.

  When performing laser bonding, it is important to irradiate the laser while maintaining a constant gap between the members to be bonded. That is, if the gap is too narrow, the local volume change of the resin melted by laser irradiation cannot be absorbed, and undesirable residual stress may occur. If the gap is too wide, the area to be melted and bonded is insufficient. There is a fear. Therefore, in order to keep the gap between the members in the range of several μm to several tens of μm, a measure is adopted in which laser irradiation is performed while applying a certain pressure. However, it has been difficult to maintain a constant gap by applying an appropriate pressure to a member having a complicated shape.

  In addition, as a method for joining laser transmissive materials by laser welding, a resin member containing toner or paint that absorbs laser light is interposed at the joining interface between laser transmissive members, and this is laminated. A method of irradiating a laser beam is proposed (for example, see Patent Documents 1 to 3). The laser absorber interposed between the laser transmissive materials absorbs the energy of the laser beam, so that the bonding interface between the two melts and joins. Yes. However, when dissimilar materials are joined together by such a method, stress is likely to be generated at the joining interface due to the difference in the linear expansion coefficient, so that sufficient joining strength may not be obtained and peeling may occur easily. . Further, as described above, it was still difficult to perform laser irradiation while maintaining an appropriate gap.

  When joining by the laser welding method, it is possible to irradiate the whole joining surface with laser light, but energy consumption is increased and production efficiency is inevitably lowered. On the other hand, it is possible to weld only a part of the joint surface by irradiating a laser beam in a spot shape or a line shape, but in this case, the adhesive force may be insufficient.

  In addition, as a method for bonding resins having low affinity to each other, a first resin member made of a first resin material having laser permeability, and a second resin material having low laser compatibility with the first resin member. A mixed powder of the first resin powder made of the first resin material and the second resin powder made of the second resin material between the second resin member made of A method of irradiating a laser beam with a mixed powder containing what it has is disclosed (for example, see Patent Document 4). In laser welding, it is said that a resin material having low compatibility with each other can be satisfactorily bonded to each other by interposing a mixed powder of laser absorbing properties at the bonding interface between the first resin member and the second resin member. Yes.

  However, since it is necessary to use a mixed powder of two types of resins to be bonded in the above bonding method, it is necessary to prepare a mixed powder corresponding to the combination of resins to be bonded. Moreover, although such a method can be used for joining resin materials, it has been difficult to use for joining a resin and an inorganic substance such as a metal. Furthermore, by interposing the mixed powder at the bonding interface between the resins, it is estimated that the stress caused by the difference in linear expansion between the resins at the bonding interface can be alleviated to some extent, but depending on the combination of the resin to be bonded In some cases it was insufficient.

  Patent Document 5 discloses a laser light-transmitting molded member, a laser light-absorbing molded member containing a laser light absorber, and a single layer or a plurality of layers sandwiched between these members while containing a laser light-transmitting absorber. The laser light transmission / absorptive molded member that consists of a layer and absorbs part of the laser light while transmitting part of the laser light contains a thermoplastic resin, and is heated by the irradiation of the laser light while being stacked. A laser weld is characterized in that it is welded and integrated. According to this document, it is described that a large number of three or more molded members can be easily integrated in a single laser welding process by adjusting the absorbance of each member.

  In Patent Document 5, the laser light transmission / absorbing molded member may be composed of a plurality of layers, but only simple examples are described in the document. In addition, the examples described in the literature are only examples in which the same base polymers are bonded to each other, and are not necessarily suitable methods for bonding different materials.

JP 2003-181931 A JP 2004-1071 A JP 2005-238462 A JP 2006-26974 A JP 2007-112126 A

  The present invention has been made to solve the above-mentioned problems, and provides a sheet for laser bonding that can be used for bonding various materials and can obtain high bonding strength with a simple operation. Objective. It is another object of the present invention to provide a bonding method and a bonded product using such a laser bonding sheet.

  In order to join the first member made of a material that is transparent to the laser beam and the second member made of the same material as or different from the first member by a laser welding method, A laser joining sheet sandwiched between a first member and a second member in advance; the laser joining sheet having a first polymer layer in contact with the first member and a second polymer layer in contact with the second member This is solved by providing a sheet for laser bonding, characterized by comprising a multilayer sheet.

  At this time, the second polymer layer is preferably made of a polymer different from the first polymer layer. It is also preferable that at least one of the first polymer layer and the second polymer layer is made of an elastomer. It is also preferable that at least one of the first polymer layer and the second polymer layer has adhesiveness. It is also preferable that at least one of the first polymer layer and the second polymer layer contains a laser beam absorber.

  Moreover, it is preferable to have at least one core layer between the first polymer layer and the second polymer layer. At this time, it is preferable that the tensile elastic modulus at 23 ° C. of the core layer is higher than both the tensile elastic modulus at 23 ° C. of the first polymer layer and the tensile elastic modulus at 23 ° C. of the second polymer layer. It is also preferable that the core layer is made of the same type of polymer as the first polymer layer and / or the second polymer layer. The first polymer layer and the second polymer layer are made of different types of polymers, and the core layer includes the same type of polymer as the first polymer layer and the same type of polymer as the second polymer layer. It is also suitable that it consists of a product or a copolymer. It is also preferable that at least one of the first polymer layer, the second polymer layer, or the core layer contains a laser absorber.

  The above-mentioned subject is a joining method which joins the 1st member which consists of material which has the permeability to laser light, and the 2nd member which consists of the same or different material as the 1st member; A laser joining sheet comprising a multi-layer sheet having a second polymer layer, wherein the first polymer layer is in contact with the first member and the second polymer layer is in contact with the second member. It is also solved by providing a joining method characterized in that the laser joining sheet is melted by irradiating a laser beam from the first member side and the first member and the second member are joined. Is done.

  At this time, the second member is preferably made of a material different from that of the first member. It is also preferable that at least one core layer is provided between the first polymer layer and the second polymer layer, and the core layer is made of the same type of polymer as at least one of the first member and the second member. Further, the first member and the second member are made of different types of polymers, and have at least one core layer between the first polymer layer and the second polymer layer, and the core layer includes the first member and the second member. It is also preferable to consist of a polymer composition or copolymer containing the same type of polymer and the same type of polymer as the second member.

  Furthermore, the above-mentioned problem is a joined product in which a first member made of a material that is transparent to laser light and a second member made of the same or different material as the first member are joined; Has a laser bonding sheet sandwiched between the first member and the second member and fused to each of the first member and the second member by laser irradiation, and the laser bonding sheet is the first This can also be solved by providing a joined product comprising a multilayer sheet having a first polymer layer adhered to the member and a second polymer layer adhered to the second member.

  By using the laser bonding sheet of the present invention, various materials can be laser-welded with high bonding strength by a simple operation.

  In order to join the first member made of a material having permeability to laser light and the second member made of the same or different material as the first member by a laser welding method, Prior to the laser light irradiation, the first member and the second member are sandwiched.

  The first member used in the present invention is made of a material that is transparent to laser light (laser transparent). Here, being transparent to laser light means that the laser light as a heating source is transmitted with almost no reflection or absorption, or is almost melted even if the laser light is partially absorbed and / or reflected. It refers to having a transmittance that allows the remaining laser light to pass therethrough and reach the laser bonding sheet.

  Although it will not specifically limit if a 1st member consists of a material which has the above permeation | transmission with respect to a laser beam, For example, what consists of resin, glass, etc. is used suitably. Examples of the resin include polyamide resins such as nylon 6 and nylon 66; polyolefin resins such as polyethylene and polypropylene; polyoxymethylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; acrylic resins such as polymethyl methacrylate; polycarbonate resins; Among various known materials such as vinyl chloride; styrenic resins such as polystyrene and ABS; epoxy resins; fluoropolymers; polyphenylene sulfide and the like, those having transparency to laser light can be mentioned. As the glass, among various known materials such as soda lime glass, lead glass, and borosilicate glass, those having transparency to laser light can be widely used. Further, tempered glass, laminated glass, multilayer glass and the like can also be used.

  The second member used in the present invention may be made of the same material as that of the first member, or may be made of a material different from that of the first member. The laser transmissive material as described above or any other material can be used. As the laser transmitting material, the same material as that used for the first member can be used. As the second member, in addition to the laser transmissive material, a material having a laser beam absorptivity (laser absorptivity) can also be used.

  In the present invention, having an absorptivity with respect to a laser beam means that the laser beam as a heat source absorbs the remainder even if it is partially transmitted and / or reflected and has the property of being heated. Examples of such laser-absorbing materials include metals, ceramics, and inorganic filler-containing compositions in which an inorganic filler is contained in a resin or rubber. In addition, a material that is made laser-absorbing by adding a dye or a pigment to the laser-transmitting material can also be used. Furthermore, wood, paper, fabric, etc. can also be used.

  The metal may be a simple substance or an alloy of two or more metals. Further, as ceramics, various known types such as oxides such as zirconia and alumina (including composite oxides), carbides such as silicon carbide, nitrides such as silicon nitride, phosphates such as apatite, etc. Things can be used. Furthermore, the composite material of the said metal and ceramics etc. can also be used. Especially, it is preferable to use a metal as a 2nd member from a practical viewpoint, and steel, stainless steel, aluminum (alloy), copper (alloy), titanium (alloy), magnesium (alloy), etc. are illustrated.

  The laser joining sheet of the present invention is irradiated with laser light in a state of being sandwiched between the first member and the second member, and is heated and melted by the energy, whereby the first member and the second member. Used to join members. The laser bonding sheet is a multilayer sheet having a first polymer layer in contact with the first member and a second polymer layer in contact with the second member. The first polymer layer and the second polymer layer may be made of different polymers, or may be made of the same polymer. When the first polymer layer and the second polymer layer are made of the same polymer, a layer made of another material is disposed therebetween. The first polymer layer and the second polymer layer are bonded to each other directly or via another layer. Therefore, the laser bonding sheet of the present invention is a multilayer sheet that can be easily handled as one molded product.

  One of the preferred embodiments of the present invention is a laser bonding sheet in which the second polymer layer is made of a polymer different from the first polymer layer. When the second member is made of a material different from that of the first member, the physical properties of these materials are different from each other, and the polymers suitable for melt bonding to these materials are often different. For example, when the first member is a resin and the second member is a metal (such as polypropylene and stainless steel), when the material properties of both are greatly different, a polymer that can be fused with high adhesive strength to both It is difficult to choose. Even in such a case, a material that can be fused well with the first member is adopted for the first polymer layer, and a material that can be fused well with the second member is adopted for the second polymer layer. As a whole, the adhesive strength between the first member and the second member can be increased.

  Here, that the second polymer layer is made of a polymer different from the first polymer layer means that the chemical composition of the polymer is different. Of course, when the monomer units constituting the polymer are different, such as polyethylene and polypropylene, some constituent monomers are common, such as polyethylene, ethylene-vinyl acetate copolymer, and maleic anhydride-modified polyethylene. Even if the other constituent monomers are different, they are different polymers. Moreover, even if it is the copolymer which consists of a multiple types of structural monomer of the same combination, if the copolymerization ratios differ, they are different polymers. However, it is not a different polymer only by the difference in molecular weight. Moreover, when a polymer layer consists of a blend, when only some polymers are common, or when a compounding ratio differs, it is set as a different polymer.

  A preferred embodiment of the present invention is a more preferred embodiment in which at least one of the first polymer layer and the second polymer layer is made of an elastomer, and both the polymer layers are made of an elastomer. is there. By using an elastomer, it is possible to reduce the stress generated at the bonding interface in the bonding of various materials, thereby maintaining a high bonding strength. In addition, the elastomer is soft and elastic, and is suitable for being brought into close contact with the shape of the joint surface. Moreover, it can also suppress that the vibration from one member is transmitted to the other member.

  As the elastomer in the present invention, any polymer material such as a crosslinked rubber or a thermoplastic elastomer can be used, and is not particularly limited. As the cross-linked rubber, various known ones such as isoprene-based rubber and butadiene-based rubber can be used. However, the degree of cross-linking is limited because highly cross-linked rubber may reduce laser weldability. . Examples of the thermoplastic elastomer include olefin elastomers, acrylic elastomers, styrene elastomers, polyester elastomers, polyurethane elastomers, polyamide elastomers, silicon elastomers, and fluorine elastomers. In the present invention, a thermoplastic elastomer is preferably used from the viewpoints of melt adhesion and processability. Among these, styrene elastomers, polyurethane elastomers, olefin elastomers, and acrylic elastomers are more preferably used.

  It is preferable that the tensile elastic modulus at 23 ° C. of at least one of the first polymer layer and the second polymer layer of the present invention is 0.01 to 200 MPa. More preferably, both polymer layers have a tensile modulus in the above range. By having such a tensile elastic modulus, when joining two different materials, stress (strain) at the interface between the two members caused by the difference in linear expansion coefficient can be relaxed. Moreover, it becomes easy to make the laser bonding sheet conform to the surface shape of the bonding surface. Therefore, the obtained bonded product can maintain high adhesive strength. If the tensile modulus of the polymer layer is too low, the adhesive strength may be reduced. The tensile elastic modulus is preferably 0.1 MPa or more. On the other hand, if the tensile modulus is too high, the stress relaxation and the follow-up to the surface shape may be insufficient. The tensile elastic modulus is preferably 100 MPa or less, more preferably 50 MPa or less.

  Further, when the resin and the metal are joined, when the hydrophobic resin and the polar resin are joined, or when the crystalline resin and the amorphous resin are joined, the first polymer layer or the second polymer layer is The polymer preferably has a polymer having a polar functional group. Since a polymer having a polar functional group has a large cohesive energy and a high affinity with a metal or a polar resin, the bonding strength between the laser bonding sheet and the metal or the polar resin can be increased. The polymer having a functional group may be a polymer modified with a monomer having a polar functional group, or the main chain of the polymer may have a polar functional group. In addition, the polymer having the polar functional group may be more absorbable with respect to the laser beam than the polymer having no polar functional group depending on the wavelength of the laser beam to be used. May be used. The polar functional group is preferably a polar group such as a carboxyl group (including a carboxylic anhydride group), a urethane group, an epoxy group, an amino group, a hydroxyl group, or an ester group, and a carboxyl group (including a carboxylic anhydride group) and a urethane group. Is particularly preferred.

  The first polymer layer or the second polymer layer may be a blend of a plurality of polymers. For example, a plurality of resins or elastomers may be blended, or a resin and an elastomer may be blended. Moreover, you may blend what has a polar functional group, and the thing which is not so. Various blends can be used depending on the purpose.

  It is preferable that at least one of the first polymer layer and the second polymer layer has adhesiveness, and it is more preferable that both polymer layers have adhesiveness. By having adhesiveness, when the laser bonding sheet is sandwiched between the first member and the second member prior to laser light irradiation, the laser bonding sheet can be temporarily fixed to the bonding surface. Workability and joining reliability are greatly improved. Moreover, the improvement of the adhesive strength derived from adhesive force can also be expected.

  The adhesive polymer layer is not particularly limited as long as it has adhesiveness. A composition comprising a base polymer and a tackifier may be used, and when the base polymer itself has tackiness, the tackifier need not be used. The molecular weight distribution of the base polymer can be widened to obtain an adhesive effect due to a low molecular weight component. Moreover, you may have a crosslinked structure in the range which does not inhibit laser welding performance.

  Regarding the adhesive strength of the laser bonding sheet of the present invention, it is preferable that the 180-degree peeling adhesive strength (adhered body: SUS304) based on 10.4 of JIS Z0237 is 0.1 N / 25 mm or more. By using the laser bonding sheet having such an adhesive force, the laser bonding sheet can be easily fixed to the bonding surface, and the adhesive force between the first member and the second member can be increased. The 180-degree peeling adhesive strength is preferably 0.5 N / 25 mm or more, more preferably 2 N / 25 mm or more, and further preferably 5 N / 25 mm or more.

  The base polymer used for the adhesive polymer layer is not particularly limited. In order to conform to the shape of the joint surface, it is preferable to use a flexible base polymer. Polyolefins represented by various modified polyethylenes such as ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid (ester) copolymer, ethylene-maleic anhydride copolymer; Various resins such as an acrylic resin such as a (meth) acrylate copolymer; a polyester resin; a polyamide resin; a polystyrene resin; a polyvinyl chloride resin; and a polyurethane resin can be used. Among these, elastomers are preferably used as the base polymer. This is because it is flexible and elastic, and is suitable for being brought into close contact with the shape of the joint surface. As the elastomer, those described above can be used.

  One suitable polymer layer having tackiness is composed of a composition comprising a base polymer and a tackifier. By blending a tackifier, a polymer layer having tackiness can be easily produced. Since many tackifiers have a high affinity for metals and the like, the adhesive strength of the portion heat-welded by laser light can often be increased as compared with the case where no tackifier is contained.

  Examples of tackifiers include coumarone resins such as coumarone / indene resin and coumarone resin / naphthenic oil / phenolic resin mixtures; terpene resins, modified terpene resins (eg, aromatic modified terpene resins), terpene-phenol resins And terpene resins such as hydrogenated terpene resins; gum rosin, tall oil rosin, wood rosin, rosin pentaerythritol ester, rosin glycerol ester, hydrogenated rosin, hydrogenated wood rosin, hydrogenated rosin methyl ester, hydrogenated rosin Pentaerythritol ester, hydrogenated rosin triethylene glycol ester, disproportionated rosin, polymerized rosin, rosin derivatives such as polymerized rosin glycerol ester and cured rosin; terpine tackifier; aromatic hydrocarbon resin, Aliphatic hydrocarbon resins, unsaturated hydrocarbon (olefin, diolefin) polymers, isoprene resins, hydrogenated hydrocarbon resins, hydrocarbon tackifying resins, polybutene, liquid polybutadiene, low molecular weight butyl rubber, etc. Examples thereof include petroleum hydrocarbon resins; styrene resins; phenol resins; xylene resins. Among these, terpene resin is preferable.

  Although content of a tackifier is not specifically limited, It is preferable to contain 1-500 weight part of tackifier with respect to 100 weight part of base polymers. When there is little content of a tackifier, the improvement of adhesive force may become inadequate. The tackifier content is more preferably 10 parts by weight or more, and even more preferably 20 parts by weight or more. On the other hand, when the content of the tackifier is too large, the flexibility of the polymer layer is lowered, and there is a possibility that the stress relaxation and following of the surface shape may be insufficient, and the strength of the polymer layer itself. May decrease. The content of the tackifier is more preferably 300 parts by weight or less, and even more preferably 200 parts by weight or less.

  As described above, when the base polymer itself has tackiness, it is not particularly necessary to use a tackifier. Examples of the base polymer itself having tackiness include acrylic polymers, urethane polymers, diene polymers, and the like.

  A block copolymer composed of a hard block and a soft block is preferably used in order to have a form-retaining ability at room temperature and to have adhesiveness and flexibility. At this time, from the viewpoint of shape retention and heat resistance, the melting point (in the case of crystallinity) or the glass transition temperature (in the case of amorphousness) of the hard block is preferably 50 ° C. or higher, and is 80 ° C. or higher. It is more preferable. From the viewpoint of melt moldability, the melting point or glass transition temperature of the hard block is usually 300 ° C. or lower. On the other hand, from the viewpoint of adhesiveness and flexibility, the glass transition point of the soft block is preferably 20 ° C. or less, more preferably 0 ° C. or less, and further preferably −20 ° C. or less. In particular, from the viewpoint of tackiness, the soft block is preferably amorphous. It is more preferable that both the soft block and the hard block are amorphous.

  As the block copolymer, an acrylic block copolymer is preferably used. The amorphous hard block and the amorphous soft block form a microphase separation structure, and can have both good mechanical performance and adhesive performance. And since it is a polar polymer, the adhesive strength after laser irradiation is also high. Furthermore, since an acrylic polymer is generally stable to light and heat, stable adhesion performance over a long period can be expected. It is preferable that the hard segment is composed of alkyl methacrylate and the soft block is composed of alkyl acrylate. A diblock copolymer or a triblock copolymer can be properly used according to the use, or may be used by mixing. Specifically, a triblock copolymer of methyl methacrylate-n butyl acrylate-methyl methacrylate and a diblock copolymer of methyl methacrylate-n butyl acrylate are exemplified. Here, the glass transition temperature of the hard block composed of methyl methacrylate is about 100 to 120 ° C., and the glass transition temperature of the soft block composed of n-butyl methacrylate is about −40 to −50 ° C. A tackifier may be added to the acrylic block copolymer.

  In addition, a urethane polymer is also preferably used as the base polymer itself having adhesiveness. Urethane polymers have a highly polar urethane bond, and particularly have good adhesion to metals and polar resins. Among these, a two-component curable urethane polymer is preferably used, and a polymer having excellent adhesiveness can be obtained. A urethane polymer can be obtained by mixing and reacting an isocyanate compound used as a raw material with an alcohol. A diisocyanate compound such as tolylene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI) and a diol compound are preferably mixed and reacted. The chemical structure and molecular weight of the diol compound are adjusted according to the purpose. Moreover, you may introduce | transduce a crosslinked structure in the range which does not inhibit the effect of this invention using a trifunctional or more than trifunctional isocyanate compound and alcohol.

  One of the preferred embodiments of the laser bonding sheet of the present invention is one having at least one core layer between the first polymer layer and the second polymer layer. By having the core layer, the mechanical properties and thickness of the entire laser bonding sheet can be adjusted, and the adhesiveness with the first member or the second member can also be adjusted. The core layer is not particularly limited as long as it is a layer made of a polymer different from the first polymer layer and the second polymer layer. The core layer may be composed of only one layer, or may be composed of a plurality of layers. In addition, the layer from which a form differs can also be used as a core layer, and the layer which consists of fabrics and polymer foams, such as a woven fabric, a knitted fabric, and a nonwoven fabric, may be sufficient.

  It is preferable that the tensile elastic modulus at 23 ° C. of the core layer is higher than both the tensile elastic modulus at 23 ° C. of the first polymer layer and the tensile elastic modulus at 23 ° C. of the second polymer layer. In this case, even if the first polymer layer and the second polymer layer are flexible, the rigidity of the entire laser bonding sheet is improved, and the handling of the sheet becomes easy. The tensile elastic modulus at 23 ° C. of the core layer is preferably more than 200 MPa, more preferably 300 MPa or more, and further preferably 1000 MPa or more. The tensile elastic modulus at 23 ° C. of the core layer is usually preferably 5000 MPa or less. The polymer used for the core layer is polyester, polyamide, polyimide, polyamideimide, aramid, polyolefin, polyoxymethylene, acrylic resin, polycarbonate, polyvinyl chloride, polyurethane, polystyrene, ABS, polysulfone, polyethersulfone, polyetherether. Various known materials such as ketone, polyetherimide, polyphenylene sulfide, polyarylate, polyester ether, fluoropolymer, polyparabanic acid, polyoxadiazole, polyhydantoin, and polyvinyl butyral can be used. At this time, it is preferable that the core layer is a biaxially stretched film because the tensile elastic modulus can be increased. For example, a biaxially stretched polyethylene terephthalate film is exemplified as a suitable material.

  When joining the 1st member and 2nd member which have various shapes, it is necessary to cut | disconnect or bend | bend the sheet | seat for laser joining previously, and to arrange | position according to the shape of a joining surface. At this time, when the laser bonding sheet is thin, flexible, or sticky, the sheet is likely to get wrinkled or air is taken in, and is arranged along the shape of the bonding surface. It is very difficult. That is, if the laser bonding sheet does not have a certain degree of rigidity, it is very difficult to properly arrange the sheet between the first member and the second member. In such a case, it is significant to employ the core layer having a high tensile elastic modulus to improve the rigidity of the laser bonding sheet.

  Moreover, it is preferable that the said core layer consists of the same kind of polymer as a 1st polymer layer and / or a 2nd polymer layer. Thereby, the bonding strength can be greatly improved. At this time, the affinity between the core layer and the first polymer layer and / or the second polymer layer is increased, the interfacial adhesive force between these layers is improved, and the destruction inside the laser bonding sheet is suppressed. In the laser irradiated portion, the first polymer layer, the second polymer layer, and the core layer are melted and mixed with each other, and at that time, they are flexibly and firmly integrated. At this time, there is a case where a chemical reaction proceeds between the polymers constituting each layer and the layers are more firmly integrated. From the viewpoint of bonding strength, it is more preferable that all of the core layer, the first polymer layer, and the second polymer layer are made of the same type of polymer.

  Here, the “same kind of polymer” means that the polymers belong to the same group for classification. For example, it refers to those belonging to groups such as polyolefin, polyester, polyamide, polyoxymethylene, acrylic resin, polycarbonate, polyvinyl chloride, styrene resin, and epoxy resin. At this time, even if it is a composition containing the polymer of another group in the range which does not inhibit the effect of invention, it shall be the same group. Here, when the polymer is a copolymer, the polymers are grouped on the basis of the constituent component having the highest weight ratio. For example, since SEBS (styrene-hydrogenated butadiene-styrene block copolymer) used in Example 1 of the present application has a styrene content of 32% by weight, it contains hydrogenated butadiene units more than twice as much. . Here, since the hydrogenated butadiene unit is an ethylene-butylene unit, it is substantially an olefin unit. That is, since the content of olefin units is more than twice the content of styrene units, such copolymers are classified as polyolefins in the present invention.

  Further, the first polymer layer and the second polymer layer are made of different types of polymers, and the core layer includes a polymer containing the same type of polymer as the first polymer layer and the same type of polymer as the second polymer layer. It is also preferable to consist of a coalescence composition or a copolymer. In this case, a polymer having a high affinity with the first member can be employed in the first polymer layer, and a polymer having a high affinity with the second member can be employed in the second polymer layer. Since the core layer has an affinity for both the first polymer layer and the second polymer layer, the interfacial adhesive force between the both surfaces of the core layer and the two polymer layers is improved, and the destruction inside the laser bonding sheet Is suppressed. In the laser-irradiated portion, the first polymer layer, the second polymer layer, and the core layer are melted and mixed with each other, and are then flexibly and firmly integrated. At this time, there is a case where a chemical reaction proceeds between the polymers constituting each layer and the layers are more firmly integrated. The core layer may be a layer composed of a polymer composition obtained by mixing the same type of polymer as the first polymer layer and the same type of polymer as the second polymer layer, or the first polymer layer and It may be a copolymer including a structural unit of the same type of polymer and a structural unit of the same type of polymer as the second polymer layer. The weight ratio of the same type of polymer as the first polymer layer and the same type of polymer as the second polymer layer is not particularly limited, but is usually about 1/9 to 9/1.

  For the purpose of improving the laser absorptivity of the laser bonding sheet, it is also preferred that at least one of the first polymer layer and the second polymer layer contains a laser beam absorber (hereinafter also referred to as “laser absorber”). From the viewpoint of efficient energy absorption, it is more preferable that both the first polymer layer and the second polymer layer contain a laser absorber. When the laser bonding sheet has a core layer, it is preferable that at least one of the first polymer layer, the second polymer layer, or the core layer contains a laser absorber. Also in this case, from the viewpoint of efficient energy absorption, it is more preferable that all of the first polymer layer, the second polymer layer, and the core layer contain a laser absorber. The laser absorbent in the present invention refers to an agent that can improve the laser absorbability of the laser bonding sheet by being added. Examples of such laser absorbers include inorganic pigments such as carbon black and composite oxide pigments; organic pigments such as phthalocyanine pigments, lake pigments, and polycyclic pigments; and various types of pigments depending on the wavelength of the laser light used. Known materials such as dyes can be used as appropriate. The blending amount of the laser absorber varies greatly depending on the type thereof, but is preferably about 0.01 to 20 parts by weight with respect to 100 parts by weight of the base polymer. Moreover, other various additives can also be mix | blended. For example, in order to improve the flexibility of the first polymer layer or the second polymer layer, various softeners for elastomers can be blended.

  The thickness of the laser bonding sheet of the present invention is not particularly limited. The sheet referred to in the present invention is a concept including a thin film, a thick plate, and the like. The total thickness of the laser bonding sheet is preferably 10 to 5000 μm. When the sheet for laser bonding has an appropriate thickness, when the first member and the second member are bonded by heating and melting with the energy of the laser beam, the stress generated at the bonding interface between the two members is moderately relieved. Is possible. When the laser bonding sheet is too thin, there is a fear that it is insufficient to relieve the stress between the two members. From such a viewpoint, the thickness of the laser bonding sheet is more preferably 20 μm or more, and further preferably 50 μm or more. On the other hand, when the laser bonding sheet is thick, it becomes difficult to melt and bond the bonding surfaces of both the first member and the second member. In such a case, one interface is laser-welded, In some cases, the other interface can be bonded only by adhesive force. However, since there is a demand for cost and a problem of the strength of the laser bonding sheet itself, the laser bonding sheet should not be too thick. The thickness of the laser bonding sheet is more preferably 2000 μm or less, and still more preferably 1000 μm or less. Here, the thickness of the laser bonding sheet refers to the distance between the surface in contact with the first member and the surface in contact with the second member.

  Although the thickness of the 1st polymer layer and the 2nd polymer layer which are contained in the sheet | seat for laser joining is not specifically limited, It is preferable that all are 1-2500 micrometers normally. The thickness of the polymer layer is more preferably 5 μm or more. More preferably, it is 500 μm or less. Although the thickness of a core layer in case the sheet | seat for laser joining has a core layer is not specifically limited, Usually, it is preferable that it is 5-2000 micrometers. The thickness of the core layer is more preferably 10 μm or more, and even more preferably 15 μm or more. Further, it is more preferably 1000 μm or less, and further preferably 500 μm or less.

  A method for producing such a multilayer sheet having the first polymer layer and the second polymer layer is not particularly limited. It can be melt-molded by coextrusion from a die, can be produced by laminating a plurality of films, or can be produced by coating a solution and then drying. When at least one of the first polymer layer and the second polymer layer has tackiness, a kneading machine such as a kneader or an extruder is used to blend a tackifier with the base polymer, knead and then mold be able to. Alternatively, the base polymer and the tackifier may be dissolved in a solvent, and the obtained solution may be applied to a release paper and then dried.

  Even when the laser bonding sheet has a core layer, the same manufacturing method as described above is employed. At this time, when at least one of the first polymer layer and the second polymer layer has tackiness, it is preferable to coat the core layer with a mixture of the base polymer and the tackifier. As the coating method, either melt coating or solution coating can be employed. Preferably, it is solution coated and then dried. If both the first polymer layer and the second polymer layer are sticky, apply the solution to one side of the core layer and dry it, then place the release paper on it, and then apply the solution to the opposite side of the core layer. And then dried. Moreover, you may laminate | stack, after giving the corona discharge process and the primer process to the surface of the film which comprises a core layer. When the tackifier is not used, the above operation may be performed using only the base polymer.

  The laser bonding sheet may be formed by melt coating or solution coating on the adherend surface of either the first member or the second member. When forming a sheet for laser bonding by melt coating, single layer coating may be repeated or coextrusion multilayer coating may be performed. On the other hand, in the case of solution coating, a single-layer coating is repeated to form a laser bonding sheet. In such a case, the joining operation is performed using a member in which a laser joining sheet is bonded in advance to one of the first member and the second member.

  The laser bonding sheet described above is sandwiched between the first member and the second member so that the first polymer layer is in contact with the first member and the second polymer layer is in contact with the second member, and the first member side The laser bonding sheet is melted by irradiating the laser beam from the first member, and the first member and the second member are bonded. Hereinafter, the joining method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of a bonded product obtained by the bonding method of the present invention. 1 is formed by laminating a first member 2, a laser bonding sheet 3, and a second member 4 in this order. The laser bonding sheet 3 includes a first polymer layer 5 in contact with the first member 2, a second polymer layer 7 in contact with the second member 4, and a core layer 6 sandwiched between the two polymer layers. In the joining method of the present invention, the laser joining sheet 3 is sandwiched between the first member 2 and the second member 4 as shown in FIG. 1, and then the laser beam L is irradiated from the first member 2 side. The laser joining sheet of the present invention only needs to be sandwiched between the first member and the second member when irradiating the laser beam. Therefore, a multilayer sheet formed in advance may be sandwiched between the first member and the second member, and laser irradiation may be performed, or the multilayer sheet pre-bonded to the adherend surface of either the first member or the second member May be brought into contact with the adherend surface of the other member for laser irradiation.

  The laser joining sheet of the present invention is suitable for joining a first member and a second member made of different materials. In this case, it is preferable to use a laser bonding sheet in which the second polymer layer is made of a polymer different from the first polymer layer. Thereby, a polymer layer suitable for adhering to each member can be selected separately.

  When at least one of the first polymer layer and the second polymer layer has adhesiveness, it can be easily fixed to the joint surface of the first member or the second member. In addition, when the base polymer is flexible, it is easy to conform to the shape of the joining surfaces of both members. Therefore, it is suitable for using a plurality of laser bonding sheets locally on a member having a large area, and is also suitable for use on a non-planar bonding surface. And it is easy to maintain the space | interval between a 1st member and a 2nd member in a fixed range by simple operation. In order to obtain the adhesive strength, after being sandwiched between the first member and the second member, the laser bonding sheet is pressed from both sides of the first member and the second member to improve the adhesive strength, and then the laser beam Is preferably irradiated. At the time of laser irradiation, the pressurization can be released, so that workability is excellent.

  When the laser bonding sheet of the present invention has a core layer, the core layer is preferably made of the same type of polymer as at least one of the first member and the second member. Thereby, the bonding strength can be improved. The core layer is not in direct contact with the first member or the second member, but the first polymer layer, the second polymer layer, and the core layer are mixed with each other due to melting or decomposition during laser irradiation. It appears that an improvement in adhesion strength is observed. Here, the same type of polymer means that the polymers belong to the same group in terms of classification. For example, it refers to those belonging to groups such as polyolefin, polyester, polyamide, polyoxymethylene, acrylic resin, polycarbonate, polyvinyl chloride, styrene resin, and epoxy resin. At this time, within the range which does not inhibit the effect of invention, even if it is a composition containing resin of another group, it shall be the same group.

  The first member and the second member are made of different types of polymers, and have at least one core layer between the first polymer layer and the second polymer layer, and the core layer includes the first member and the second member. It is also preferable to consist of a polymer composition or copolymer containing the same type of polymer and the same type of polymer as the second member. Thereby, the joining strength in the case of joining the first member and the second member made of different materials can be improved. In this case, the first polymer layer and the second polymer layer are made of different types of polymers, and the core layer includes the same type of polymer as the first polymer layer and the same type of polymer as the second polymer layer. By comprising a polymer composition or a copolymer, the joint strength can be further improved. The core layer is not in direct contact with the first member or the second member, but the first member, the second member, the first polymer layer, the second polymer layer, and the core layer are mutually connected by melting during laser irradiation. It seems that such an increase in bonding strength is recognized by being mixed and flexibly and firmly integrated. The core layer may be a layer made of a polymer composition obtained by mixing the same kind of polymer as the first member and the same kind of polymer as the second member, or the same kind as the first member. The copolymer may include a polymer structural unit and a polymer structural unit of the same type as the second member. Here, the weight ratio of the same kind of polymer as the first member and the same kind of polymer as the second member is not particularly limited, but is usually about 1/9 to 9/1.

  In the present invention, any known laser beam such as a gas laser, a solid laser, or a semiconductor laser can be used and is not particularly limited. Depending on the types and thicknesses of the first member, the second member, and the laser bonding sheet, an optimal wavelength and output can be selected and used. Further, the laser light is not limited to one having a single wavelength, and may be a mixture of two or more wavelengths. Also, when the bonding range is wider than the laser beam irradiation diameter, the laser light source or the laminated product to be joined (the first member and the second member laminated with the laser joining sheet sandwiched) is moved as necessary. However, laser light irradiation may be performed.

  Since the first member is transparent to the laser beam, at least a part of the laser beam irradiated from the first member side passes through the first member and reaches the laser bonding sheet. When at least one layer of the laser bonding sheet is made of a material that absorbs laser light, the laser bonding sheet is heated and melted by the energy of the laser light absorbed by the laser bonding sheet itself. At this time, when at least one of the first member and the second member is made of resin, the heat of the laser bonding sheet is also transmitted to these resins and melts. When the irradiation of the laser beam is completed, the laser bonding sheet and the resin of the first member and / or the second member are cooled and solidified again, whereby the laser bonding sheet and the resin are welded.

  On the other hand, when at least one of the first member and the second member is made of a material other than resin (metal, glass, ceramics, etc.), the laser bonding sheet heated and melted by irradiation with laser light is melted into the material other than resin. It is deposited and cooled after the irradiation of the laser beam and solidified again, so that a material other than the laser bonding sheet and the resin is welded. As described above, the first member and the second member are welded to each other, and the laser joining sheet and the second member are welded to each other at the joining interface, whereby the first member and the second member are joined.

  When the laser bonding sheet is made of a laser-transmitting material, at least a part of the laser light that reaches the laser bonding sheet passes through the laser bonding sheet and reaches the second member. In order for the laser-transmitting laser bonding sheet to be heated and melted, the second member needs to be heated by the laser beam to generate heat, so the second member needs to be made of a laser-absorbing material. The first member and the second member are joined by heating and melting the laser joining sheet by the heat generated by heating the second member with laser light, and then cooling and solidifying. Thus, the joined product of the present invention having the first member, the second member, and the laser joining sheet sandwiched therebetween and fused to each of the first member and the second member. can get.

  In the bonding method of the present invention, the first member and the second member are bonded by melting a laser bonding sheet by irradiation with laser light. Therefore, as described above, the laser joining sheet and the joining interface on the laser joining sheet side of the first member and / or the second member are subjected to a thermal cycle in which they are heated by laser light irradiation and then cooled. . At this time, stress due to a difference in linear expansion coefficient between the first member and the second member may occur at the bonding interface, but when the first polymer layer or the second polymer layer is a flexible laser bonding sheet, Can relieve such stress, and can prevent reduction in bonding strength and peeling. Thereby, the reliability of joining can be improved. Furthermore, when the first polymer layer or the second polymer layer has tackiness, since many of the tackifiers have high affinity for metals and the like, the adhesive strength of the portion heated and welded by laser light is increased. It becomes larger than the case where it does not contain. Moreover, since the part which was not heat-welded by the laser beam is also adhered by the adhesive force, the adhesive strength can be further improved.

  In addition, thermal stress and mechanical stress are generated at the bonding interface due to the use of the obtained bonded product. Even in such a case, when the first polymer layer or the second polymer layer is a flexible laser bonding sheet, Since the stress and stress are relieved, the bonding strength can be maintained even after long-term use. In addition, when bonded with only adhesive force, the occurrence of creep due to long-term use often becomes a problem, but only a part of the laser bonding sheet is melted by locally irradiating laser light. In the case of joining, the fusion part becomes an anchor and the occurrence of creep can be prevented.

  As a combination of the first member and the second member (first member / second member), for example, resin / resin, resin / metal, resin / ceramic, resin / glass, glass / resin, glass / metal, glass / ceramic, Glass / glass is exemplified. In particular, when the second member is made of a material different from that of the first member, the actual benefit of employing the laser bonding sheet of the present invention is great. Here, the “resin / resin” combination is useful when different types of resins, particularly resins having different polarities, are joined. Moreover, it is useful also when joining what contains many inorganic fillers in resin, and the thing which is not so. In addition, “resin / metal” is a combination that effectively achieves the effects of the present invention, and has great practical needs. This can be solved by using a laser bonding sheet.

  Hereinafter, the present invention will be described more specifically with reference to examples. Test methods in the following examples are as follows.

(1) Tensile elastic modulus Based on JIS K7161 and JIS K6251, the tensile elastic modulus specified in “4.6 Tensile elastic modulus” of JIS K7161 was measured and calculated. The shape of the sample was “Dumbell No. 3 type”. The measurement was performed after adjusting the condition in an environment of 23 ° C.

(2) 180 degree peeling adhesive strength Based on 10.4 of JIS Z0237, 180 degree peeling adhesive strength (N / 25 mm) to a stainless steel (SUS304) plate was measured. Here, when the measurement chart of the adhesive strength was undulated, the average value of the convex points and the average value of the concave points were obtained, respectively, and the average values were peeled 180 degrees to determine the adhesive strength.

(3) Shear strength A shear test of the obtained bonded product was performed by Instron 3382 (Instron Corporation). As shown in FIG. 3, a spacer 8 made of the same member as the first member 2 is overlapped on the joining surface side of the second member 4 and fixed with a chuck of the testing machine, and a spacer made of the same member as the second member 4. 9 was stacked on the joining surface side of the first member 2 and fixed to the chuck of the testing machine. Subsequently, a tensile test parallel to the first member 2 and the second member 4 (arrow direction in the figure) was applied, and a shear test was performed. At that time, the shear rate was 0.5 mm / sec and the maximum strength was obtained. The obtained maximum strength was defined as shear strength.

[First member and second member]
In the following examples and comparative examples, the following members were used as the first member and the second member.
・ Polymethylmethacrylate (PMMA)
A plate made of polymethyl methacrylate having a width of 25 mm, a length of 50 mm, and a thickness of 2 mm (“Acrylite 001” manufactured by Mitsubishi Rayon Co., Ltd.) was used.
・ Polypropylene (PP)
A plate made of polypropylene having a width of 25 mm, a length of 50 mm, and a thickness of 2 mm (“PP-N-BN” manufactured by Shin-Kobe Electric Co., Ltd.) was used.
・ Polyoxymethylene (POM)
A plate made of polyoxymethylene (POM) resin having a width of 25 mm, a length of 50 mm, and a thickness of 2 mm (“Polypen core acetal copolymer” manufactured by Nippon Polypenco Co., Ltd.) was used.
・ Stainless steel (SUS)
Stainless steel (SUS304) having a width of 25 mm, a length of 50 mm, and a thickness of 1.5 mm was used.

[First polymer layer and second polymer layer]
In the following Examples and Comparative Examples, the following solutions were prepared to form the first polymer layer or the second polymer layer. Further, the tensile modulus at 23 ° C. and the peel strength at 180 ° C. of each polymer layer were measured according to the method described above. Here, for each polymer layer, a tensile modulus and adhesive force were measured using a single-layer sample of 100 μm, but it is considered that these values do not fluctuate greatly even if the thickness and the layer configuration vary somewhat.

SEBS layer SEBS modified with a monomer having a carboxyl group (styrene content 32% by weight, molecular weight 52,000) 100 parts by weight, aromatic modified terpene resin ("YS Resin TO-115" manufactured by Yashara Chemical Co., Ltd.) 30 parts by weight, near infrared absorber (“IR-T” manufactured by Showa Denko KK) 0.05 part by weight and 300 parts by weight of toluene were weighed, put in a container, sealed and left for 18 hours, A solution (hereinafter sometimes referred to as “SEBS solution”) was obtained by stirring with a screw until uniform. The obtained SEBS solution was applied onto a release paper with a coating machine and then dried to obtain a polymer layer having a thickness of 100 μm (hereinafter sometimes referred to as “SEBS layer”). The tensile modulus of elasticity of the obtained polymer layer was 4.08 MPa. Further, the 180 ° peel-off adhesive strength of the obtained polymer layer to the stainless steel plate (SUS304) is 13.7 N / 25 mm on the average of the convex points, 11.2 N / 25 mm on the average of the concave points, and 12.5 N / 25 mm on the average of the concaves and convexes. Met.

・ Soft acrylic layer Weigh 100 parts by weight of acrylic block copolymer “LA2250” manufactured by Kuraray Co., Ltd., 1.0 part by weight of carbon black “PRINTEX G” manufactured by Degussa and 150 parts by weight of toluene, and put them in a container. After sealing for 18 hours, the solution was stirred with a screw until uniform (hereinafter sometimes referred to as “soft acrylic solution”). It was applied onto a release paper with a coating machine and then dried to obtain a polymer layer having a thickness of 100 μm (hereinafter sometimes referred to as “soft acrylic layer”). Here, “LA2250” is a triblock copolymer of methyl methacrylate-n butyl acrylate-methyl methacrylate. The tensile modulus of elasticity of the obtained polymer layer was 0.5 MPa. Further, the 180 ° peel-off adhesive strength of the obtained polymer layer to the stainless steel plate (SUS304) was 8.6 N / 25 mm on the average of the convex points, 5.2 N / 25 mm on the average of the concave points, and 6.9 N / 25 mm on the average of the concaves and convexes. Met.

-Strong adhesion soft acrylic layer 100 parts by weight of acrylic block copolymer "LA2250" manufactured by Kuraray Co., Ltd., 30 parts by weight of rosin-based tackifier, 5 parts by weight of softening agent, carbon black "PRINTEX G" 1.0 manufactured by Degussa Part by weight and 200 parts by weight of toluene are weighed, put in a container, sealed for 18 hours, left to stand, and stirred with a screw until uniform (hereinafter referred to as “strongly sticky soft acrylic solution”). There is.) It was coated on a release paper with a coating machine and dried to obtain a polymer layer having a thickness of 100 μm (hereinafter sometimes referred to as “strongly sticky soft acrylic layer”). The tensile modulus of elasticity of the obtained polymer layer was 0.4 MPa. Further, the 180 ° peel-off adhesive strength of the obtained polymer layer to the stainless steel plate (SUS304) was 11.7 N / 25 mm on the average of the convex points, 9.1 N / 25 mm on the average of the concave points, and 10.0 N / 25 mm on the average of the concaves and convexes. Met.

-Urethane layer Polyoxypropylene diol is used as the polyol, TDI (tolylene diisocyanate) is used as the polyisocyanate, and carbon black "PRINTEX G" manufactured by Degussa Co. is added to 100 parts by weight of the chain extender and terminator. 0.2 part by weight was added and stirred. 100 parts by weight of a mixed solvent (methyl ethyl ketone: ethyl acetate: toluene = 1: 1: 1 (volume ratio)) was added thereto to prepare a solution having a solid content of about 50% by weight. Subsequently, 4.0 parts by weight of a curing agent “Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd. was added, and applied onto a release paper with a coating machine, followed by drying to obtain a film having a thickness of 100 μm. The resulting film had a tensile modulus of 0.4 MPa. Moreover, 180 degree peeling adhesive force with respect to the stainless steel plate (SUS304) of the obtained film is 15.3 N / 25mm by a convex point average, 13.0 N / 25mm by a concave point average, and 14.2 N / 25mm by a concave-convex average. there were.

Example 1
On the release paper, the “soft acrylic solution” was applied and then dried to form a “soft acrylic layer” having a thickness of 50 μm. The “SEBS solution” was applied to the surface of the obtained “soft acrylic layer” and dried to form a “SEBS layer” having a thickness of 50 μm. Thereby, a laser bonding sheet 3 having a total thickness of 100 μm and having a two-layer structure was obtained. The “soft acrylic layer” was the first polymer layer 5, the “SEBS layer” was the second polymer layer 7, PMMA was the first member 2, and SUS was the second member 4. As shown in FIG. 2, the first member 2 and the second member 4 are shifted by 25 mm in the length direction and overlapped so that the first member 2 is on top, and between the first member 2 and the second member 4 (FIG. 2). Between the obtained bonding sheet 3 so that the first polymer layer 5 is in contact with the first member 2 and the second polymer layer 7 is in contact with the second member 4. I got a product. A pressure of 0.4 MPa was applied from both sides to the overlapped portion of the obtained laminated product, and heating by laser irradiation was performed from above (first member 2 side) under the following conditions. A 940 nm semiconductor laser was used as the laser. The collimated diameter of the laser beam was 46 mm, the focal length was 222.5 mm, and the minimum spot diameter was 1.52 mm. The laser beam was irradiated at an output distance of 250 W at an irradiation distance of 207.5 mm. The first member 2 was scanned 25 mm at a speed of 10 mm / sec with respect to the short direction (lateral direction in FIG. 2). After the irradiation was completed, the laser bonding sheet 3 was solidified again by air cooling, whereby the first member 2 and the second member 4 were bonded via the laser bonding sheet 3, and the bonded product 1 was obtained. The results of measuring the shear strength of the obtained bonded product 1 are summarized in Table 1.

Comparative Examples 1 and 2
Example 1 except that the sheet for laser bonding in Example 1 is composed of only a 100 μm “soft acrylic layer” (Comparative Example 1), or is composed of only a 100 μm “SEBS layer” (Comparative Example 2). In the same manner as in Example 1, a joined product was obtained. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Example 2
On the release paper, the “SEBS solution” was applied and then dried to form a “SEBS layer” having a thickness of 50 μm. The “urethane solution” was applied to the surface of the obtained “SEBS layer” and then dried to form a “urethane layer” having a thickness of 50 μm. As a result, a laser bonding sheet having a two-layer structure with a total thickness of 100 μm was obtained. The “SEBS layer” was the first polymer layer, the “urethane layer” was the second polymer layer, PP was the first member, and POM was the second member. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Comparative Examples 3 and 4
In Example 2, Example 2 was used except that the sheet for laser bonding consisted of only a 100 μm “SEBS layer” (Comparative Example 3) or only composed of a 100 μm “Urethane layer” (Comparative Example 4). In the same manner, a joined product was obtained. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Example 3
As the core layer, a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 25 μm and subjected to corona discharge treatment on both sides was used. The PET film has a tensile elastic modulus at 23 ° C. of about 4 GPa (4000 MPa). The “SEBS solution” was applied to one side of the PET film and then dried to form a “SEBS layer” having a thickness of 50 μm. The release paper was put on the surface of the “SEBS layer” and turned over, and the “soft acrylic solution” was applied to the other surface of the PET film and then dried to form a “soft acrylic layer” having a thickness of 50 μm. As a result, a laser bonding sheet having a three-layer structure with a total thickness of 125 μm was obtained. The “soft acrylic layer” was the first polymer layer, the “SEBS layer” was the second polymer layer, PMMA was the first member, and SUS was the second member. Since the rigidity of the laser bonding sheet was improved as compared with the case of using the laser bonding sheet having no core layer as in Example 1 or the like, the laser bonding sheet was used as the first member and the second member. The operation of sandwiching between them was easy. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Examples 4 and 5
In Example 3, the above-mentioned “soft acrylic solution” was applied on both sides of the PET film and dried to form a “soft acrylic layer” having a thickness of 50 μm (Example 4), or on both sides of the PET film A bonded article was obtained in the same manner as in Example 3 except that the above-mentioned “SEBS solution” was applied and dried to form a “SEBS layer” having a thickness of 50 μm (Example 5). The operation of sandwiching the laser bonding sheet between the first member and the second member was easy. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Example 6
A 25 μm thick polyoxymethylene (POM) film was used as the core layer. The tensile elastic modulus at 23 ° C. of the POM film is about 3 GPa (3000 MPa). The “urethane solution” was applied to both sides of the POM film and dried to form a “urethane layer” having a thickness of 5 μm. As a result, a laser bonding sheet having a three-layer structure with a total thickness of 35 μm was obtained. A “urethane layer” was used as the first polymer layer and the second polymer layer, POM was used as the first member and the second member, and a joined product was obtained in the same manner as in Example 1. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Example 7
In Example 6, a bonded product was obtained in the same manner as in Example 6 except that the same PET film as in Example 3 was used as the core layer. The operation of sandwiching the laser bonding sheet between the first member and the second member was easy. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Comparative Example 5
In Example 6, a joined product was obtained in the same manner as in Example 6 except that the sheet for laser joining was composed of only a 100 μm “urethane layer”. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Example 8
Weigh 100 parts by weight of acrylic block copolymer “LA4285” manufactured by Kuraray Co., Ltd., 1.0 part by weight of carbon black “PRINTEX G” manufactured by Degussa and 150 parts by weight of toluene, put in a container and seal for 18 hours. Then, the solution was stirred with a screw until it became uniform to obtain a solution (hereinafter sometimes referred to as “hard acrylic solution”). It was coated on a release paper with a coating machine and then dried to obtain a polymer layer having a thickness of 30 μm (hereinafter sometimes referred to as “hard acrylic layer”), which was used as a core layer. Here, “LA4285” is a triblock copolymer of methyl methacrylate-n-butyl acrylate-methyl methacrylate, and is a hard polymer with less n-butyl acrylate content than “LA 2250”. The obtained “hard acrylic layer” had a tensile elastic modulus at 23 ° C. of about 1 GPa (1000 MPa). The “strongly sticky soft acrylic solution” was applied to one side of the “hard acrylic layer” and dried to form a “strongly sticky soft acrylic layer” having a thickness of 20 μm. Subsequently, the release paper is put on the surface of the “strongly sticky soft acrylic layer” and then turned over, and the “strongly sticky soft acrylic solution” is applied to the other side of the “hard acrylic layer” and then dried, and the thickness is 20 μm. A “strongly adhesive soft acrylic layer” was formed. As a result, a laser bonding sheet having a three-layer structure mainly composed of an acrylic polymer having a total thickness of 70 μm was obtained. In the obtained laser bonding sheet, the core layer is composed of a “hard acrylic layer”, and the first polymer layer and the second polymer layer are composed of “strongly adhesive soft acrylic layer”. POM was used as the first member and the second member, and a joined product was obtained in the same manner as in Example 1. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

Example 9
50 parts by weight of PP, 50 parts by weight of PMMA, and 1.0 part by weight of carbon black “PRINTEX G” manufactured by Degussa Company were melt kneaded and extruded to obtain a sheet having a thickness of 50 μm, which was used as a core layer. The resulting core layer had a tensile elastic modulus at 23 ° C. of about 500 MPa. The “SEBS solution” was applied to one side of the core layer and dried to form a “SEBS layer” having a thickness of 20 μm. Subsequently, the release paper was overlaid on the surface of the “SEBS layer” and turned over, and the “soft acrylic solution” was applied to the other surface of the core layer and then dried to form a “soft acrylic layer” having a thickness of 20 μm. . As a result, a laser bonding sheet having a three-layer structure with a total thickness of 90 μm was obtained. In the obtained laser bonding sheet, the core layer is made of a resin composition containing PMMA and PP, the first polymer layer is made of “SEBS layer”, and the second polymer layer is made of “soft acrylic layer”. PP was used as the first member, PMMA was used as the second member, and a joined product was obtained in the same manner as in Example 1. The results of measuring the shear strength of the obtained bonded product are summarized in Table 1.

  As shown in Comparative Example 1, the “acrylic layer” does not have sufficient adhesiveness with SUS, and as shown in Comparative Example 2, the “SEBS layer” does not have sufficient adhesiveness with PMMA. In contrast, in Example 1 in which the “acryl layer” was bonded to PMMA and the “SEBS layer” was bonded to SUS, a much higher shear strength was obtained. That is, according to the present invention, when the members to be bonded are different, the polymer layer suitable for each member can be selected. The present invention is significant when bonding members having greatly different physical properties such as metal and resin. This point is also shown in Example 2 and Comparative Examples 3 and 4, and the same applies to the case of bonding resins having greatly different polarities.

  As can be seen by comparing Examples 3, 4 and 5 with Example 1 and Comparative Examples 1 and 2, by placing a high modulus core layer between the first polymer layer and the second polymer layer. Since the rigidity of the sheet is improved as compared with the case of using the laser bonding sheet not having the core layer, the operation of sandwiching the laser bonding sheet between the first member and the second member was easy. This point is particularly important when the joint surface is not flat. Note that the shear strength is slightly increased by having a high elastic modulus core layer. This is thought to be due to the reduced thickness per layer of the flexible polymer layer, which is also an advantage.

  As shown in Example 6, when the core layer is made of the same type of material as the first member and the second member, the core layer is made of a different type of material from the first member and the second member (Example) Compared with 7), the shear strength is greatly improved. The core layer is not in direct contact with the first member or the second member, but the first polymer layer, the second polymer layer, and the core layer are mixed with each other due to melting and decomposition during laser irradiation, and the bonding strength is increased. It is thought that it rose.

  As shown in Example 8, when the core layer is made of the same polymer (acrylic polymer) as the first polymer layer and the second polymer layer, the bonding strength is extremely high, and the first member or the second member Peel due to material destruction. This is because the compatibility between the core layer, the first polymer layer, and the second polymer layer has increased, and as a result, the interfacial adhesive force between these layers has been improved and the destruction inside the laser bonding sheet has been suppressed. Conceivable. In the laser-irradiated portion, the first polymer layer, the second polymer layer, and the core layer are presumed to be melted and mixed with each other and to be integrated flexibly and firmly at that time.

  In Example 9, the core layer is made of a mixture of PP and PMMA. Here, PP is the same type of polymer as the first polymer layer (SEBS) and the first member (PP). PMMA is the same type of polymer as the second polymer layer (acrylic block copolymer) and the second member (PMMA). The obtained bonded product had extremely high bonding strength, and was peeled off due to material destruction of the first member or the second member. The core layer has an affinity with the first polymer layer, the second polymer layer, the first member, and the second member, so that even if the first member and the second member are polymers with low affinity to each other, the core layer is excellent. High bonding strength was obtained. By melting during laser irradiation, the first member, the second member, the first polymer layer, the second polymer layer, and the core layer are mixed with each other, and are flexibly and firmly integrated, thereby improving the bonding strength. It is thought that it was accepted.

It is a typical sectional view of the joined article obtained by the joining method of the present invention. It is a typical top view and sectional view for explaining the method of laminating the 1st member, the sheet for laser joining, and the 2nd member in an example. It is a schematic perspective view for demonstrating the measuring method of shear strength in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Joined product 2 1st member 3 Sheet | seat for laser joining 4 2nd member 5 1st polymer layer 6 Core layer 7 2nd polymer layer 8, 9 Spacer A Overlapping part L Laser beam

Claims (15)

In order to join the first member made of a material having transparency to the laser beam and the second member made of the same material as or different from the first member by the laser welding method, the first member is irradiated before the laser beam irradiation. A laser joining sheet sandwiched between a member and a second member;
The laser joining sheet comprises a multilayer sheet having a first polymer layer in contact with the first member and a second polymer layer in contact with the second member.   The sheet for laser bonding according to claim 1, wherein the second polymer layer is made of a polymer different from the first polymer layer.   The laser joining sheet according to claim 1 or 2, wherein at least one of the first polymer layer and the second polymer layer is made of an elastomer.   The laser bonding sheet according to claim 1, wherein at least one of the first polymer layer and the second polymer layer has adhesiveness.   The sheet for laser bonding according to any one of claims 1 to 4, wherein at least one of the first polymer layer and the second polymer layer contains a laser beam absorber.   The sheet for laser bonding according to any one of claims 1 to 5, further comprising at least one core layer between the first polymer layer and the second polymer layer.   The laser joining sheet according to claim 6, wherein the core layer has a tensile modulus at 23 ° C. higher than the tensile modulus at 23 ° C. of the first polymer layer and the tensile modulus at 23 ° C. of the second polymer layer.   The laser bonding sheet according to claim 6 or 7, wherein the core layer is made of the same type of polymer as the first polymer layer and / or the second polymer layer.   The first polymer layer and the second polymer layer are made of different types of polymers, and the core layer includes the same type of polymer as the first polymer layer and the same type of polymer as the second polymer layer. The laser bonding sheet according to claim 6 or 7, comprising a product or a copolymer.   The laser bonding sheet according to any one of claims 6 to 9, wherein at least one of the first polymer layer, the second polymer layer, or the core layer contains a laser absorber. A joining method for joining a first member made of a material having transparency to laser light and a second member made of the same or different material as the first member;
A laser joining sheet comprising a multi-layer sheet having a first polymer layer and a second polymer layer, wherein the first polymer layer is in contact with the first member and the second polymer layer is in contact with the second member; Sandwiched between the second members,
The laser joining sheet is melted by irradiating laser light from the first member side,
A joining method comprising joining the first member and the second member.   The joining method according to claim 11, wherein the second member is made of a material different from that of the first member.   The at least one core layer is provided between the first polymer layer and the second polymer layer, and the core layer is made of the same kind of polymer as at least one of the first member and the second member. Joining method.   The first member and the second member are made of different types of polymers, and have at least one core layer between the first polymer layer and the second polymer layer, and the core layer is the same type as the first member. The joining method according to claim 11 or 12, comprising a polymer composition or a copolymer comprising the same polymer as the second member and the same type of polymer as the second member. A joined product in which a first member made of a material that is transparent to laser light and a second member made of the same or different material as the first member are joined;
The bonded product has a laser bonding sheet sandwiched between a first member and a second member and fused by laser irradiation to each of the first member and the second member,
A bonded product, wherein the laser bonding sheet comprises a multilayer sheet having a first polymer layer bonded to a first member and a second polymer layer bonded to a second member.

Images