Method for joining resin members and near-infrared absorber composition

Abstract

The present invention provides: a joining method for joining two resin members, at least one of which transmits laser light, the method for joining resin members comprising a step A for applying a near-infrared absorber composition containing a near-infrared absorber and at least one selected from the group consisting of a metal and a metal compound onto a surface of at least one resin member out of a first resin member and a second resin member, a step B for bringing the first resin member and the second resin member into contact with each other with the application portion to which has been applied the near-infrared absorber composition interposed therebetween, and a step C for irradiating the application portion with laser light to melt and join the first resin member and the second resin member at the application portion; and a near-infrared absorber composition.

Description

Method for joining resin members and near-infrared absorber composition

[0001] The present disclosure relates to a method for joining resin members and a near-infrared absorber composition.

[0002] Conventionally, a method of joining resin members by laser welding has been known. Many resin members joined by laser welding are a combination of a resin member that transmits laser light and a resin member that absorbs laser light (see, for example, Japanese Patent No. 4059907). This is because the laser light absorbed by the resin member that absorbs laser light is converted into thermal energy, melting the resin members to join them.

[0003] On the other hand, in recent years, the demand for joining resin members that transmit laser light to each other has been rapidly expanding. As a method for joining resin members that transmit laser light to each other, a method using a near-infrared absorber has been proposed (see, for example, Japanese Patent No. 4805049 and International Publication No. 2024 / 128016).

[0004] In the method of joining resin members that transmit laser light to each other, a near-infrared absorber is applied to the joining surface and irradiated with laser light. When the near-infrared absorber is irradiated with laser light, the near-infrared absorber absorbs the light and the light energy is converted into thermal energy. The resin members are melted and joined by this converted thermal energy. However, with only the converted thermal energy, the thermal welding of the resin members is insufficient, and the resin members cannot be firmly joined to each other.

[0005] The problem to be solved by one embodiment of the present disclosure is to provide a method for joining resin members that can join resin members to each other with a stronger joining strength than in the prior art. Another problem to be solved by another embodiment of the present disclosure is to provide a near-infrared absorber composition used in the method for joining resin members.

[0006] The following embodiments are specific means for solving the above problems: <1> A joining method for joining two resin members, at least one of which transmits laser light, comprising: step A, applying a near-infrared absorbing agent composition, which includes a near-infrared absorbing agent and at least one selected from the group consisting of a near-infrared absorbing agent and a metal and a metal compound, to the surface of at least one of the resin members, a first resin member and a second resin member; step B, bringing the first resin member and the second resin member into contact via the application portion of the near-infrared absorbing agent composition; and step C, irradiating the application portion with laser light to melt and join the first resin member and the second resin member at the application portion. <2> The joining method for resin members according to <1>, wherein the near-infrared absorbing agent composition further comprises a perchlorate. <3> A method for joining resin members according to <1> or <2>, wherein the near-infrared absorbent comprises at least one selected from the group consisting of diimonium compounds, cyanine compounds, squarylium compounds, azochelate compounds, phthalocyanine compounds, and naphthalocyanine compounds. <4> A method for joining resin members according to any one of <1> to <3>, wherein the near-infrared absorbent comprises a perchlorate ion as a counterion. <5> A method for joining resin members according to any one of <1> to <4>, wherein the metal compound is a metal perchlorate salt. <6> A method for joining resin members according to any one of <1> to <5>, wherein the metal compound comprises at least one selected from the group consisting of iron compounds, zinc compounds, copper compounds, and silver compounds. <7> A method for joining resin members according to any one of <1> to <6>, wherein the total content of the metal and the metal compound in the near-infrared absorbent composition is 0.000001 times by mass to 1 time by mass relative to the content of the near-infrared absorbent. <8> A method for joining resin members according to any one of <1> to <7>, wherein in step A above, an amount of the near-infrared absorbing agent composition is applied to the surface of at least one of the resin members, the first resin member and the second resin member, in such an amount that the absorbance at the maximum absorption wavelength of the near-infrared absorbing agent is 0.05 to 2.<9> The method for joining resin members according to any one of <1> to <8>, wherein the laser light has an oscillation wavelength of 700 nm to 1200 nm, and the light source is at least one selected from the group consisting of an Nd:YAG laser, a semiconductor laser, and a dye laser. <10> The method for joining resin members according to any one of <1> to <9>, wherein the material of the first resin member and the second resin member is a thermoplastic resin. <11> A near-infrared absorbing agent composition used in the method for joining resin members according to any one of <1> to <10>, comprising a near-infrared absorbing agent and at least one selected from the group consisting of metals and metal compounds. <12> A resin joint joined by the method for joining resin members according to any one of <1> to <10>.

[0007] According to one embodiment of the present disclosure, a method for joining resin members is provided that can join resin members together with a stronger bonding strength than conventional methods. According to another embodiment of the present disclosure, a near-infrared absorbing agent composition used in the above-mentioned method for joining resin members is provided.

[0008] Figure 1A is a diagram illustrating the operation of step A in the embodiment. Figure 1B is a diagram illustrating the operation of step B in the embodiment.

[0009] The following describes in detail an example of an embodiment of the resin component joining method relating to this disclosure. The requirements described below may be based on a typical embodiment of this disclosure, but this disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the purpose of this disclosure.

[0010] In this disclosure, a numerical range indicated using "~" means a range that includes the numerical values ​​before and after "~" as the lower and upper limits, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0011] In this disclosure, the amount of each component in the near-infrared absorbing agent composition means the total amount of multiple substances present in the near-infrared absorbing agent composition if there are multiple substances corresponding to each component in the near-infrared absorbing agent composition, unless otherwise specified.

[0012] In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0013] In this disclosure, "solids" means the components excluding the solvent, and "solvent" means water and organic solvents.

[0014] In this disclosure, "mass%" and "weight%" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0015] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved.

[0016] In this disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic".

[0017] [Method for joining resin members] The method for joining resin members according to the present disclosure (hereinafter also simply referred to as the "joining method") is a joining method for joining two resin members, at least one of which transmits laser light, and includes: Step A, applying a near-infrared absorbing agent composition containing a near-infrared absorbing agent and at least one selected from the group consisting of a near-infrared absorbing agent and a metal and a metal compound to the surface of at least one of the resin members, a first resin member and a second resin member; Step B, bringing the first resin member and the second resin member into contact via the application portion of the near-infrared absorbing agent composition; and Step C, irradiating the application portion with laser light to melt and join the first resin member and the second resin member at the application portion.

[0018] The resin member joining method according to this disclosure makes it possible to join resin members together with stronger bonding strength than conventional methods. The reason why the resin member joining method according to this disclosure can achieve such an effect is not clear, but the inventors speculate as follows. However, the following speculation is not intended to be a restrictive interpretation of the resin member joining method according to this disclosure, but is explained as an example.

[0019] In the joining method according to this disclosure, a near-infrared absorbing agent composition containing a near-infrared absorbing agent and a metal and / or metal compound is used to join two resin members (i.e., a first resin member and a second resin member). When laser light is irradiated onto the portion of the near-infrared absorbing agent composition placed between the first resin member and the second resin member, the near-infrared absorbing agent in the near-infrared absorbing agent composition absorbs the light, and the light absorption energy is converted into thermal energy. The heat generated by this conversion decomposes the near-infrared absorbing agent. The metal and / or metal compound in the near-infrared absorbing agent composition acts catalytically in this decomposition of the near-infrared absorbing agent. The heat generated by the decomposition of the near-infrared absorbing agent melts the first resin member and the second resin member, thereby joining the first resin member and the second resin member. In the joining method according to this disclosure, it is believed that the first resin member and the second resin member can be firmly joined by using the heat generated by the conversion of the light absorption energy of the near-infrared absorber into thermal energy, as well as the heat generated by the decomposition of the near-infrared absorber catalyzed by a metal and / or a metal compound, to melt the first resin member and the second resin member.

[0020] [Step A] Step A is a step of applying a near-infrared absorbing agent composition, which includes a near-infrared absorbing agent and at least one selected from the group consisting of metals and metal compounds, to the surface of at least one of the first resin member and the second resin member. According to Step A, a portion of the near-infrared absorbing agent composition is formed on the surface of at least one of the first resin member and the second resin member.

[0021] In step A, the near-infrared absorbing agent composition may be applied to the surface of only one of the first resin member or the second resin member, or it may be applied to the surfaces of both the first and second resin members. Here, "surface" of the resin member means the surface that brings the first resin member and the second resin member into contact in step B via the application portion of the near-infrared absorbing agent composition (e.g., the overlapping surface and the abutting surface).

[0022] The method for applying the near-infrared absorbing agent composition to the surface of a resin member is not particularly limited. Examples of known methods for applying the near-infrared absorbing agent composition include coating, immersion, sheet bonding, and sheet sandwiching. The coating method is preferred for applying the near-infrared absorbing agent composition. The coating method allows for the near-infrared absorbing agent composition to be applied to the surface of the resin member with high uniformity. Furthermore, the coating method is also preferred because it allows for easy adjustment of the application position.

[0023] Coating methods include, for example, spin coating, die coating, spray coating, bar coating, dispenser coating, inkjet coating, roll coating, and curtain coating. Coating methods using cotton swabs are also available.

[0024] In step A, it is preferable to apply an amount of near-infrared absorbing agent composition to the surface of at least one of the first resin member and the second resin member such that the absorbance at the maximum absorption wavelength of the near-infrared absorbing agent is 0.05 or more, more preferably 0.15 or more, and even more preferably 0.2 or more. When the amount of near-infrared absorbing agent composition applied is such that the absorbance at the maximum absorption wavelength of the near-infrared absorbing agent is 0.05 or more, the resin members tend to be bonded together more strongly. From the viewpoint of bonding strength between resin members, the amount of near-infrared absorbing agent composition applied is not particularly limited, but for example, from the viewpoint of coloring of the joint due to the near-infrared absorbing agent, it is preferable that the amount is such that the absorbance at the maximum absorption wavelength of the near-infrared absorbing agent is 1.75 or less, more preferably 1.5 or less, and even more preferably 0.75 or less. If the amount of near-infrared absorbing agent composition applied is such that the absorbance at the maximum absorption wavelength of the near-infrared absorbing agent is 1.75 or less, discoloration caused by the near-infrared absorbing agent is less likely to occur at the joint of the resin member. Therefore, if the resin member is colorless, the resulting resin joint will also maintain its colorless state well, and the aesthetic value of the resin joint will not be easily impaired. In one embodiment, the amount of near-infrared absorbing agent composition applied may be such that the absorbance at the maximum absorption wavelength of the near-infrared absorbing agent is 0.05 to 2, 0.15 to 2, 0.2 to 2, 0.05 to 1.75, 0.05 to 1.5, 0.15 to 0.75, or 0.2 to 0.75.

[0025] In this disclosure, absorbance refers to the sum of the absorbance values ​​obtained when the near-infrared absorbing agent composition contains two or more near-infrared absorbing agents, by measuring the absorbance of the near-infrared absorbing agent composition at the maximum absorption wavelength of each near-infrared absorbing agent. Furthermore, when the near-infrared absorbing agent composition is applied to the surfaces of both the first and second resin members, the amount refers to the total amount of the near-infrared absorbing agent composition applied to the surface of the first resin member and the near-infrared absorbing agent composition applied to the surface of the second resin member. In this disclosure, "maximum absorption wavelength of the near-infrared absorbing agent" refers to the maximum absorption wavelength of the near-infrared absorbing agent in the near-infrared region (i.e., between 780 nm and 2500 nm).

[0026] The absorbance is measured using a UV-Vis-Near-Infrared spectrophotometer, with a resin component that has not been treated with the near-infrared absorbing agent composition as a reference. For example, a UV-Vis-Near-Infrared spectrophotometer (model number: UV-3600) manufactured by Shimadzu Corporation can be suitably used. However, the UV-Vis-Near-Infrared spectrophotometer is not limited to this.

[0027] <Resin Members> At least one of the two resin members (i.e., the first resin member and the second resin member) transmits laser light. Both of the two resin members may transmit laser light. At least one (preferably both) of the two resin members is preferably transparent. For example, the haze value of at least one (preferably both) of the two resin members is preferably 30% or less, and more preferably 10% or less. The higher the haze value of the resin member, the more likely the irradiated laser light is to scatter inside the resin member, and the more likely the irradiation efficiency of the laser light to the application area of ​​the near-infrared absorbing agent composition will decrease. When the haze value of the resin member is 30% or less, scattering of the irradiated laser light inside the resin member is less likely to occur, and the irradiated laser light can be efficiently delivered to the application area of ​​the near-infrared absorbing agent composition through the resin member. The haze values ​​of the two resin members may be the same or different.

[0028] The haze value of the resin component is measured using a haze meter in accordance with JIS K 7136:2000 (ISO 14782-1:1999). For example, a haze meter manufactured by Nippon Denshoku Industries Co., Ltd. (product name: NDH-2000) can be suitably used. However, the haze meter is not limited to this.

[0029] The first resin member and the second resin member may be colored or colorless, but it is preferable that both be colorless.

[0030] The materials of the first resin member and the second resin member may be the same or different, but from the viewpoint of bonding strength, for example, it is preferable that they be the same. When the materials of the first resin member and the second resin member are the same, when they are joined by melting, the resin members tend to integrate more easily because they are made of the same material, resulting in a stronger bond.

[0031] In the joining method according to this disclosure, since the first resin member and the second resin member are joined by melting them, it is preferable that both the first resin member and the second resin member are thermoplastic resins. In this disclosure, a thermoplastic resin means a resin that softens and becomes plastic when heated and hardens when cooled.

[0032] Examples of thermoplastic resins include polycarbonate resin, acrylic resin (e.g., polymethyl methacrylate, polyacrylonitrile, and polyacrylamide), polyamide resin (e.g., nylon 6, nylon 66, nylon 9, and nylon 12), acrylonitrile-butadiene-styrene resin, polyester resin (e.g., polyethylene terephthalate), polyolefin resin (e.g., polyethylene, polypropylene, and cyclic olefin copolymer), polyvinyl chloride resin, and polystyrene resin.

[0033] The material of the first resin member and the second resin member is preferably at least one selected from the group consisting of polycarbonate resin, acrylic resin, polyamide resin, polyester resin, polyolefin resin, and polyvinyl chloride resin, for example, from the viewpoint of transparency, and more preferably at least one selected from the group consisting of polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polypropylene, polyvinyl chloride, nylon, and cyclic olefin copolymer.

[0034] The first resin member and the second resin member may contain one type of resin or two or more types of resin.

[0035] The melting points of the first resin member and the second resin member are not particularly limited, but are preferably, for example, 100°C or higher. Alternatively, the melting points of the first resin member and the second resin member are preferably, for example, 300°C or lower. In one embodiment, the melting points of the first resin member and the second resin member may each be between 100°C and 300°C. The melting points of the first resin member and the second resin member may be the same or different, but are preferably the same.

[0036] The melting point of the resin component is measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121:2012 (ISO 3146:2022). A suitable differential scanning calorimeter for this purpose is, for example, a differential scanning calorimeter (model number: DSC7000X) manufactured by Hitachi High-Tech Science Corporation. However, the differential scanning calorimeter is not limited to this model.

[0037] The sizes of the first resin member and the second resin member are not particularly limited and can be set as appropriate depending on the purpose. The sizes of the first resin member and the second resin member may be the same or different.

[0038] The shapes of the first resin member and the second resin member are not particularly limited as long as they can be brought into contact with each other via the portion to which the near-infrared absorbing agent composition is applied, and can be appropriately set according to the purpose. The shapes of the first resin member and the second resin member may be planar or three-dimensional. Examples of the shapes of the first resin member and the second resin member include plate-like, columnar, rod-like, and conical shapes. The shapes of the first resin member and the second resin member may be the same or different.

[0039] <Near-infrared absorbing agent composition> The near-infrared absorbing agent composition used in the bonding method according to this disclosure comprises a near-infrared absorbing agent and at least one selected from the group consisting of metals and metal compounds. The components of the near-infrared absorbing agent composition will be described in detail below.

[0040] (Near-infrared absorber) The near-infrared absorber composition contains a near-infrared absorber. The type of near-infrared absorber is not particularly limited. The near-infrared absorber should, for example, have absorption in the near-infrared region (e.g., 700 nm to 1200 nm), which is a preferred oscillation wavelength for a laser light source.

[0041] Examples of the near-infrared absorber include, for example, diimonium compounds, cyanine compounds, squarylium compounds, azo chelate compounds, phthalocyanine compounds, and naphthalocyanine compounds. The near-infrared absorber preferably contains at least one selected from the group consisting of diimonium compounds, cyanine compounds, squarylium compounds, azo chelate compounds, phthalocyanine compounds, and naphthalocyanine compounds, for example, in that it is liable to decompose by light and heat. More preferably, it is at least one selected from the group consisting of diimonium compounds, cyanine compounds, squarylium compounds, azo chelate compounds, phthalocyanine compounds, and naphthalocyanine compounds. Further preferably, from the viewpoint of suppressing coloring caused by the near-infrared absorber at the joint of the resin bonded body, for example, the near-infrared absorber is at least one selected from the group consisting of diimonium compounds, cyanine compounds, and squarylium compounds, and particularly preferably a diimonium compound.

[0042] The near-infrared absorber preferably has perchlorate ion as a counter ion. When the near-infrared absorber has perchlorate ion as a counter ion, there is a tendency that resin members can be bonded more firmly and efficiently. The reason is considered as follows. When the near-infrared absorber composition is irradiated with laser light, the near-infrared absorber in the near-infrared absorber composition absorbs the light, and the light absorption energy is converted into heat energy. During this conversion, the metal and / or metal compound acts as a catalyst to promote the thermal decomposition of the near-infrared absorber. When the near-infrared absorber has perchlorate ion as a counter ion, the near-infrared absorber thermally decomposes at a relatively low temperature. It is considered that the heat of decomposition generated by this decomposition further promotes the thermal decomposition of the near-infrared absorber, and more heat can be efficiently generated.

[0043] Examples of compounds suitable as the near-infrared absorber are given below. However, the near-infrared absorber in the present disclosure is not limited to the following Compounds B-1 to B-9.

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] The near-infrared absorber composition may contain one kind of near-infrared absorber alone or two or more kinds thereof.

[0055] The content of the near-infrared absorber in the near-infrared absorber composition is not particularly limited. For example, it is preferably 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 20% by mass, and still more preferably 0.05% by mass to 10% by mass, based on the total mass of the near-infrared absorber composition.

[0056] The near-infrared absorber may be a commercially available product or a synthetic product. When the near-infrared absorber is a synthetic product, the synthesis method of the near-infrared absorber is not particularly limited. Conventionally known methods can be applied to the synthesis of the near-infrared absorber. For example, a near-infrared absorber that is a diimonium-based compound can be synthesized by referring to the method described in JP-A-5-98243, a near-infrared absorber that is a cyanine-based compound can be synthesized by referring to the method described in Ukrainskii Khimicheskii Zhurnal (Russian Edition) (2008), Vol. 74 (Volumes 3-4), pages 105-113, and a near-infrared absorber that is a squarylium-based compound can be synthesized by referring to the method described in International Publication No. 2023 / 021802.

[0057] (Metals and / or Metal Compounds) The near-infrared absorbing agent composition contains at least one selected from the group consisting of metals and metal compounds. The near-infrared absorbing agent composition may contain only metals, only metal compounds, or both metals and metal compounds. However, from the viewpoint of uniform solubility in the near-infrared absorbing agent composition, for example, it is preferable to contain at least a metal compound, and more preferable to contain only a metal compound.

[0058] The metal and metal compound are not particularly limited as long as they function as catalysts. The molecular weight of the metal compound is preferably 80 to 500, and more preferably 100 to 350.

[0059] Examples of metals include iron, zinc, copper, and silver. Examples of metal compounds include iron compounds, zinc compounds, copper compounds, and silver compounds. Preferably, the metal compound contains at least one selected from the group consisting of iron compounds, zinc compounds, copper compounds, and silver compounds, and more preferably, at least one selected from the group consisting of iron compounds, zinc compounds, copper compounds, and silver compounds.

[0060] The metal compound may be, for example, a metal halide, an inorganic metal salt, or an organometallic salt.

[0061] Examples of metal halides include iron(III) chloride, iron(III) bromide, zinc(II) chloride, copper(II) chloride, and silver(II) chloride. At least one of iron(III) chloride and silver(II) chloride is preferred as the metal halide.

[0062] As an inorganic metal salt, for example, a metal perchlorate salt is preferred. When the metal compound is a metal perchlorate salt, the resin components tend to be bonded together more strongly and efficiently. The reason for this is thought to be as follows: When a near-infrared absorbing agent composition is irradiated with laser light, the near-infrared absorbing agent in the composition absorbs the light, and the light absorption energy is converted into thermal energy. During this conversion, the metal and / or metal compound acts as a catalyst, promoting the thermal decomposition of the near-infrared absorbing agent. Since metal perchlorate salts tend to have a relatively low decomposition initiation temperature, when the metal compound is a metal perchlorate salt, the heat generated by the conversion from light absorption energy to thermal energy causes the metal compound, which is the metal perchlorate salt, to decompose first. It is thought that the heat generated by this decomposition causes a chain reaction of decomposition of the near-infrared absorbing agent, allowing a larger amount of heat to be efficiently generated.

[0063] Examples of metal perchlorate salts include iron(III) perchlorate, zinc(II) perchlorate, copper(II) perchlorate, and silver(II) perchlorate. At least one of iron(III) perchlorate and silver(II) perchlorate is preferred as the metal perchlorate salt.

[0064] As for organometallic salts, for example, organic acid metal salts are preferred. Examples of metal compounds that are organic acid metal salts (so-called organic acid metal salts) include iron(II) acetate, copper(II) acetate, copper(II) gluconate, and zinc(II) lactate.

[0065] The metal compound is preferably at least one selected from the group consisting of metal halides, metal perchlorates, and metal organic acids; more preferably at least one selected from the group consisting of metal halides and metal perchlorates; even more preferably a metal perchlorate; and particularly preferably at least one of iron(III) perchlorate and silver(II) perchlorate.

[0066] The metal and / or metal compound contained in the near-infrared absorbing agent composition may be a single type or two or more types.

[0067] The total content of metals and metal compounds in the near-infrared absorbent composition is not particularly limited, but is preferably 0.0000001 to 1 times the mass of the near-infrared absorbent, more preferably 0.000001 to 1 time, and even more preferably 0.00001 to 1 time. When the total content of metals and metal compounds in the near-infrared absorbent composition is 0.0000001 times or more the mass of the near-infrared absorbent, a significant difference in catalytic function can be observed. When the total content of metals and metal compounds in the near-infrared absorbent composition is 1 time or less the mass of the near-infrared absorbent, the effects of metal residue on the resin joint obtained by joining resin members (e.g., discoloration and brittleness) tend to be suppressed.

[0068] (Perchlorates) The near-infrared absorbing agent composition preferably further contains perchlorates. When the near-infrared absorbing agent composition further contains perchlorates, it tends to bond resin components together more strongly and efficiently. Note that the term "perchlorates" as used herein does not include those corresponding to the near-infrared absorbing agents and metal compounds mentioned above.

[0069] When a near-infrared absorbing agent composition is irradiated with laser light, the near-infrared absorbing agent in the composition absorbs the light, and the absorbed light energy is converted into thermal energy. During this conversion, the metal and / or metal compound acts as a catalyst, promoting the thermal decomposition of the near-infrared absorbing agent. If the near-infrared absorbing agent composition further contains perchlorates, the heat generated by the conversion from absorbed light energy to thermal energy causes the perchlorates, which have a lower decomposition onset temperature, to decompose first. It is thought that the heat generated by this decomposition of the perchlorates causes a chain reaction of decomposition of the near-infrared absorbing agent, thereby efficiently generating a larger amount of heat.

[0070] The perchlorate is not particularly limited, and examples include sodium perchlorate, potassium perchlorate, and ammonium perchlorate. The perchlorate preferably contains at least one selected from the group consisting of sodium perchlorate, potassium perchlorate, and ammonium perchlorate, for example, from the viewpoint of solubility and availability, and more preferably contains at least one selected from the group consisting of sodium perchlorate and ammonium perchlorate.

[0071] If the near-infrared absorbing agent composition further contains perchlorates, it may contain one type of perchlorate alone or two or more types.

[0072] If the near-infrared absorbing agent composition further contains a perchlorate, the perchlorate content in the near-infrared absorbing agent composition is not particularly limited and can be appropriately set considering cases where the near-infrared absorbing agent composition contains a near-infrared absorbing agent having a perchlorate ion as a counterion, and / or cases where the near-infrared absorbing agent composition contains a metal compound that is a metal perchlorate salt. The total content of the near-infrared absorbing agent having a perchlorate ion as a counterion, the metal compound that is a metal perchlorate salt, and the perchlorate that does not fall under either the near-infrared absorbing agent or the metal compound in the near-infrared absorbing agent composition is preferably 0.1 to 1.0 times the mass, more preferably 0.15 to 1.0 times the mass, and even more preferably 0.15 to 0.5 times the mass, relative to the content of the near-infrared absorbing agent.

[0073] (Solvent) The near-infrared absorbing agent composition preferably further contains a solvent. When the near-infrared absorbing agent composition further contains a solvent, the solubility and dispersibility of each component contained in the near-infrared absorbing agent composition are improved, so that the near-infrared absorbing agent composition can be applied to the resin member in a more uniform state. As a result, the bonding strength between resin members in the resin joint tends to be stronger.

[0074] The type of solvent is not particularly limited. The solvent can be appropriately selected considering the solubility and dispersibility of each component contained in the near-infrared absorber composition, as well as the applicability and drying properties when the near-infrared absorber composition is formed. Examples of solvents include ester-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, halogen-based solvents, and aromatic hydrocarbon-based solvents.

[0075] Specific examples of ester solvents include methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, methyl lactate, and ethyl lactate.

[0076] Specific examples of ether-based solvents include diethylene glycol dimethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and propylene glycol monopropyl ether acetate.

[0077] Specific examples of ketone solvents include acetone, 2-butanone, cyclohexanone, 2-heptanone, and 3-heptanone.

[0078] Specific examples of amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone.

[0079] Specific examples of halogenated solvents include methylene chloride, chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-bromopropane, chlorobenzene, and 1,2-dichlorobenzene.

[0080] Specific examples of aromatic hydrocarbon solvents include toluene and xylene.

[0081] The solvent is preferably at least one selected from the group consisting of ester solvents, ketone solvents, halogen solvents, and aromatic hydrocarbon solvents, from the viewpoint of solubility or dispersibility of the components contained in the near-infrared absorber composition, availability of the solvent, viscosity and surface tension of the near-infrared absorber composition when applied to the resin member, and drying speed of the solvent. It is more preferably at least one selected from the group consisting of acetone, 2-butanone, cyclohexanone, n-butyl acetate, toluene, xylene, chloroform, and 1-bromopropane, and even more preferably at least one selected from the group consisting of 2-butanone, cyclohexanone, chloroform, and 1-bromopropane.

[0082] If the near-infrared absorbing agent composition further contains a solvent, it may contain one solvent alone or two or more solvents.

[0083] If the near-infrared absorbing agent composition further contains a solvent, the solvent content in the near-infrared absorbing agent composition is not particularly limited and can be appropriately set depending on the method of applying the near-infrared absorbing agent composition to the resin member. For example, if the method of applying the near-infrared absorbing agent composition to the resin member is a spray coating method, the solvent content in the near-infrared absorbing agent composition can be set to 98% to 99.9999% by mass of the total mass of the near-infrared absorbing agent composition. Also, if the method of applying the near-infrared absorbing agent composition to the resin member is, for example, a spin coating method, a bar coating method, a dispenser coating method, or an inkjet coating method, the solvent content in the near-infrared absorbing agent composition can be set to 90% to 99.9% by mass of the total mass of the near-infrared absorbing agent composition.

[0084] (Other Components) The near-infrared absorbing agent composition may contain components other than those described above (so-called other components) as necessary, to the extent that it does not impair the effect of the bonding method relating to this disclosure. Examples of other components include binders, viscosity modifiers, preservatives, pH adjusters, chelating agents, antistatic agents, and other additives.

[0085] <<Method for preparing near-infrared absorbing agent composition>> The method for preparing a near-infrared absorbing agent composition is not particularly limited. A near-infrared absorbing agent composition can be prepared by mixing a near-infrared absorbing agent with at least one selected from the group consisting of metals and metal compounds, and an optional component such as a perchlorate, solvent, or other component. The method of mixing each component is not particularly limited, and one example is mixing by stirring.

[0086] [Step B] Step B is a step in which the first resin member and the second resin member are brought into contact via a portion for applying the near-infrared absorbing agent composition. By going through Step B, a state is formed in which the portion for applying the near-infrared absorbing agent composition is positioned between the first resin member and the second resin member.

[0087] The manner in which the first resin member and the second resin member are brought into contact via the portion to which the near-infrared absorbing agent composition is applied is not particularly limited, but it is preferable, for example, that the first resin member and the second resin member are indirectly overlapped or butted together via the portion to which the near-infrared absorbing agent composition is applied. In this disclosure, "butted together" means bringing the two resin members close together and in contact with each other. For example, if both resin members are plate-shaped bodies, it means bringing the sides connected to the main surface of each plate-shaped body into contact with each other in a butting-like manner.

[0088] [Process C] Process C is a process in which laser light is irradiated onto the application area, melting and joining the first resin member and the second resin member at the application area. When laser light is irradiated onto the application area of ​​the near-infrared absorbing agent composition placed between the first resin member and the second resin member, the near-infrared absorbing agent in the near-infrared absorbing agent composition absorbs light, and the light absorption energy is converted into thermal energy. The heat generated by this conversion decomposes the near-infrared absorbing agent. The metal and / or metal compound in the near-infrared absorbing agent composition acts catalytically in this decomposition of the near-infrared absorbing agent. The heat generated by the decomposition of the near-infrared absorbing agent melts the first resin member and the second resin member, thereby joining the first resin member and the second resin member.

[0089] The section containing the near-infrared absorbing agent composition is irradiated with laser light via a first resin member and / or a second resin member. The laser light irradiation pattern is not particularly limited and may be a single irradiation or a scanning irradiation, but a single irradiation is preferred from the viewpoint of productivity per unit time.

[0090] The emission wavelength of the laser light is not particularly limited as long as it is in the near-infrared wavelength range, but is preferably, for example, 700 nm to 1200 nm. The laser light source can be appropriately selected and used as long as it is capable of emitting near-infrared light. Examples of light sources with wavelengths of 700 nm to 1200 nm include solid-state lasers and liquid lasers that emit near-infrared light. Examples of solid-state lasers include Nd:YAG lasers and semiconductor lasers. Examples of liquid lasers include dye lasers. The laser light source is preferably at least one selected from the group consisting of Nd:YAG lasers, semiconductor lasers, and dye lasers. The output power of the laser light is not particularly limited, but is preferably, for example, 5 W or more. The irradiation energy is not particularly limited, but is preferably, for example, 10 mJ / cm ２ ~100 mJ / cm ２ It is preferable that this is the case. The irradiation time is not particularly limited, but is preferably, for example, 0.01 seconds to 1 second.

[0091] [Other Processes] The joining method relating to this disclosure may include processes other than processes A, B, and C. In this disclosure, processes other than processes A, B, and C are also referred to as "other processes."

[0092] Other steps include, for example, step X, which involves drying the near-infrared absorbing agent composition applied to the surface of the resin member in step A. If the near-infrared absorbing agent composition further contains a solvent, the bonding method according to this disclosure preferably includes step X between steps A and B. In step X, at least a portion of the solvent in the near-infrared absorbing agent composition is removed.

[0093] Methods for drying the near-infrared absorbing agent composition include, for example, natural drying, heat drying, and reduced-pressure drying. These drying methods can be applied individually or in combination to dry the near-infrared absorbing agent composition. The drying temperature and drying time can be appropriately set, for example, depending on the type and amount of solvent in the near-infrared absorbing agent composition. An example of drying conditions is a drying temperature of 20°C to 120°C and a drying time of 30 seconds to 1200 seconds.

[0094] [Near-infrared absorbing agent composition] The near-infrared absorbing agent composition according to this disclosure is a near-infrared absorbing agent composition used in the resin member joining method according to this disclosure, and comprises a near-infrared absorbing agent and at least one selected from the group consisting of metals and metal compounds. The near-infrared absorbing agent composition according to this disclosure is synonymous with the near-infrared absorbing agent composition in the resin member joining method according to this disclosure, and the preferred embodiments are also the same, so a description is omitted here.

[0095] [Resin Joint] The resin joint according to this disclosure is a resin joint joined by the resin member joining method according to this disclosure. Because the resin joint according to this disclosure is joined by the resin member joining method according to this disclosure, the bonding strength between the resin members is stronger compared to a resin joint joined by a conventional resin member joining method.

[0096] The resin joints according to this disclosure can be applied to, for example, automotive parts (e.g., headlamps, taillamps, instrument panels, and resonators), medical devices (e.g., medical tubing), electronic components, and home appliances (e.g., housings). Because the resin joints according to this disclosure have stronger bonding strength between resin members than resin joints joined by conventional resin member joining methods, they are particularly suitable for applications requiring strong bonding strength.

[0097] The resin component joining method and near-infrared absorbing agent composition according to this disclosure will be described in more detail below with reference to examples. However, the resin component joining method and near-infrared absorbing agent composition according to this disclosure are not limited to the following examples, unless they exceed the spirit of the disclosure.

[0098] [Synthesis of near-infrared absorber] (1) Compound B-1 Compound B-1 was synthesized by a method similar to the method described in Japanese Patent Publication No. 5-98243.

[0099] (2) Compounds B-2 to B-7 Compounds B-2 to B-7 mentioned above are synthesized by a method similar to the method described in Japanese Patent Publication No. 5-98243.

[0100] (3) Compound B-8 Compound B-8, as described above, is synthesized by the method described in Ukrainskii Khimicheskii Zhurnal (Russian Edition) (2008), No. 74 (vols. 3-4), pages 105-113.

[0101] (4) Compound B-9 Compound B-9 is synthesized by the method described in International Publication No. 2023 / 021802.

[0102] [Preparation of Resin Bonded Body] <Example 1> 1. Preparation of Near-Infrared Absorbing Agent Composition A near-infrared absorbing agent composition was prepared by mixing 0.1 parts by mass of compound B-1 as a near-infrared absorbing agent, 0.00001 parts by mass of iron(III) chloride as a metal compound, and 99.89999 parts by mass of cyclohexanone as a solvent.

[0103] 2. Application of Near-Infrared Absorbing Agent Composition to Resin Members Two polycarbonate resin plates [Material: Polycarbonate (PC), Melting point of PC: 250°C, Color: Clear, Size: 50 mm square, Thickness: 2 mm, Manufactured by Standard Test Piece Co., Ltd.] were prepared as resin members to be bonded. The two prepared resin members were designated as the first resin member and the second resin member, respectively. First, as shown in Figure 1A, masking was performed on parts Q on the surface of the first resin member 10 other than the area P (coating area: 25 mm x 50 mm) to which the near-infrared absorbing agent composition was to be applied. Next, the near-infrared absorbing agent composition was applied to the area P on the surface of the first resin member 10 by spin coating using a spin coater coating machine manufactured by Misaka Corporation [Product name: Opticoat MS-B150] at a rotation speed of 500 rpm (revolutions per minute) [Step A]. The amount of near-infrared absorbing agent composition applied was set to the amount at which the absorbance of compound B-1, the near-infrared absorbing agent, at its maximum absorption wavelength of 1094 nm was 0.3. The absorbance was measured using a UV-Vis near-infrared spectrophotometer (model: UV-3600, manufactured by Shimadzu Corporation) with a polycarbonate resin plate without the near-infrared absorbing agent composition applied as a reference. Next, the first resin member coated with the near-infrared absorbing agent composition was heated at 80°C for 1 minute using a hot plate to volatilize the solvent in the near-infrared absorbing agent composition. As a result, a first resin member having a portion coated with a near-infrared absorbing agent composition containing at least a near-infrared absorbing agent and a metal compound was manufactured.

[0104] 3. Overlapping and joining of resin members Next, as shown in Figure 1B, the first resin member 10 having the near-infrared absorbing agent composition application portion prepared above and the second resin member 20 prepared above were overlapped via the near-infrared absorbing agent composition application portion [Step B]. Then, using a simultaneous direct transmission infrared welding (STTIr) type laser welding device [Product name: Radiance 3i, manufactured by Emerson Japan Co., Ltd.], laser light was simultaneously irradiated from the second resin member 20 side to the near-infrared absorbing agent composition application portion at an oscillation wavelength of 980 nm with a laser unit output of 25 W, melting and joining the first resin member and the second resin member [Step C]. A resin joint was thus manufactured.

[0105] <Example 2> A resin bond was prepared in the same manner as in Example 1, except that in "1. Preparation of near-infrared absorbing agent composition" of Example 1, the type of solvent was changed from "cyclohexanone" to "1-bromopropane," and in "2. Application of near-infrared absorbing agent composition to resin member," the method of applying the near-infrared absorbing agent composition was changed from "spin coating method" to "spray coating method." The application of the near-infrared absorbing agent composition to the resin member by spray coating was performed using an airbrush manufactured by BKJANYO, with a nozzle of 0.3 mm, an air pressure of 0.15 MPa, and a spraying distance of 5 cm to 10 cm.

[0106] <Example 3> A resin bond was prepared in the same manner as in Example 1, except that in "1. Preparation of near-infrared absorbing agent composition" of Example 1, the type of solvent was changed from "cyclohexanone" to "2-butanone," and in "2. Application of near-infrared absorbing agent composition to resin member" the method of applying the near-infrared absorbing agent composition was changed from "spin coating method" to "bar coating method." The application of the near-infrared absorbing agent composition to the resin member by bar coating method was performed using an automatic coating machine (model: G-7) manufactured by Orihara Manufacturing Co., Ltd.

[0107] <Example 4> In Example 1, the resin bond was prepared in the same manner as in Example 1, except that in "1. Preparation of near-infrared absorbent composition," the type and amount of solvent were changed from "99.89999 parts by mass of cyclohexanone" to "94.89999 parts by mass of chloroform," and 5 parts by mass of a binder [product name: Panlite® L-1225-L, manufactured by Teijin Limited] were added, and in "2. Application of near-infrared absorbent composition to resin member," the method of applying the near-infrared absorbent composition was changed from "spin coating method" to "dispenser coating method." The application of the near-infrared absorbent composition to the resin member by dispenser coating method was performed using an electric dispenser (product name: Tofutty) manufactured by Icams Lab Co., Ltd.

[0108] <Example 5> In Example 3, a resin bond was fabricated in the same manner as in Example 3, except that the method of applying the near-infrared absorbing agent composition was changed from the "bar coating method" to the "inkjet coating method" in "2. Application of the near-infrared absorbing agent composition to the resin member". The application of the near-infrared absorbing agent composition to the resin member by inkjet coating was performed using a material printer (product name: DMP-2850) manufactured by Fujifilm Corporation.

[0109] <Example 6> A resin bond was prepared in the same manner as in Example 1, except that the method of applying the near-infrared absorbing agent composition was changed from the "spin coating method" to the "cotton swab application method" in "2. Application of the near-infrared absorbing agent composition to the resin member" in Example 1. The application of the near-infrared absorbing agent composition to the resin member by the cotton swab application method was performed using industrial cotton swabs (model number: P751S) manufactured by Nippon Cotton Swab Co., Ltd.

[0110] <Example 7> In Example 1, a resin bond was fabricated in the same manner as in Example 1, except that the laser irradiation pattern was changed from "single irradiation" to "scanning irradiation" in "3. Overlapping and joining of resin members". For the scanning irradiation of the laser light, a galvanoscan type laser welding device [product name: BRANSON® GL-300, manufactured by Emerson Japan Co., Ltd.] was used, and the laser light was scanned and irradiated from the second resin member 20 side to the application area of ​​the near-infrared absorber composition under the conditions of laser unit output of 300 W, oscillation wavelength of 1080 nm, and laser irradiation diameter of 1.57 mm, melting and joining the first resin member and the second resin member.

[0111] <Examples 8-12> In Examples 8-12, the resin bond is prepared in the same manner as in Example 1, except that the composition of the near-infrared absorbent composition is changed to the composition shown in Table 2 in "1. Preparation of near-infrared absorbent composition" of Example 1.

[0112] <Examples 13-27> In Examples 13-27, the resin bond is prepared in the same manner as in Example 1, except that the composition of the near-infrared absorbent composition is changed to the composition shown in Table 3 in "1. Preparation of near-infrared absorbent composition" of Example 1.

[0113] <Examples 28-37> In Examples 28-37, resin bonded bodies are prepared in the same manner as in Example 1, except that the composition of the near-infrared absorbent composition is changed to the composition shown in Table 4 in "1. Preparation of near-infrared absorbent composition" of Example 1.

[0114] <Examples 38-45> In Example 1, "2. Application of near-infrared absorbing agent composition to resin member," the amount of near-infrared absorbing agent composition applied was changed to an amount such that the absorbance of compound B-1, which is a near-infrared absorbing agent, at its maximum absorption wavelength of 1094 nm was as shown in Table 5. Otherwise, a resin bond was prepared in the same manner as in Example 1.

[0115] <Example 46> In Example 46, a resin joint is prepared in the same manner as in Example 1, except that in "2. Application of near-infrared absorbing agent composition to resin member" of Example 1, the material of the resin member (i.e., the first resin member and the second resin member) is changed from "polycarbonate (PC)" to "polyethylene terephthalate (PET)". Specifically, a polyethylene terephthalate resin plate [Material: polyethylene terephthalate, PET melting point: 250°C, Color: clear, Size: 50 mm square, Thickness: 2 mm, Manufactured by Standard Test Piece Co., Ltd.] is used as the resin member.

[0116] <Example 47> In Example 47, a resin joint is prepared in the same manner as in Example 1, except that in "2. Application of near-infrared absorbing agent composition to resin member" of Example 1, the material of the resin member (i.e., the first resin member and the second resin member) is changed from "polycarbonate (PC)" to "polymethyl methacrylate (PMMA)". Specifically, a polymethyl methacrylate resin plate [Material: polymethyl methacrylate, PMMA melting point: 165°C, Color: clear, Size: 50 mm square, Thickness: 2 mm, Manufactured by Standard Test Piece Co., Ltd.] is used as the resin member.

[0117] <Example 48> In Example 48, a resin joint is prepared in the same manner as in Example 1, except that in "2. Application of near-infrared absorbing agent composition to resin member" of Example 1, the material of the resin member (i.e., the first resin member and the second resin member) is changed from "polycarbonate (PC)" to "polypropylene (PP)". Specifically, a polypropylene resin plate [Material: polypropylene, PP melting point: 160°C, Color: natural, Size: 50 mm square, Thickness: 2 mm, Manufactured by Standard Test Piece Co., Ltd.] is used as the resin member.

[0118] <Example 49> In Example 49, a resin joint is prepared in the same manner as in Example 1, except that in "2. Application of near-infrared absorbing agent composition to resin member" of Example 1, the material of the resin member (i.e., the first resin member and the second resin member) is changed from "polycarbonate (PC)" to "polyvinyl chloride (PVC)". Specifically, a polyvinyl chloride resin sheet [Material: rigid polyvinyl chloride, PVC melting point: 170°C, Color: clear, Size: 50 mm square, Thickness: 2 mm, manufactured by Standard Test Piece Co., Ltd.] is used as the resin member.

[0119] <Example 50> In Example 50, a resin joint is prepared in the same manner as in Example 1, except that in "2. Application of near-infrared absorbing agent composition to resin member" of Example 1, the material of the resin member (i.e., the first resin member and the second resin member) is changed from "polycarbonate (PC)" to "nylon (Ny)". Specifically, a nylon resin sheet is used, which is injection molded using a mold to a size of 50 mm square and a thickness of 2 mm from nylon [product name: Trogamid (registered trademark) CX7323 Natural, melting point of Ny: 190°C, manufactured by Polypla Evonik Co., Ltd.].

[0120] <Example 51> In Example 51, a resin bond is prepared in the same manner as in Example 1, except that in "2. Application of near-infrared absorbing agent composition to resin member" of Example 1, the material of the resin member (i.e., the first resin member and the second resin member) is changed from "polycarbonate (PC)" to "cycloolefin copolymer (COC)". Specifically, a cycloolefin copolymer resin sheet is used, which is injection molded using a mold to a size of 50 mm square and a thickness of 2 mm from cycloolefin copolymer [product name: Topas (registered trademark) COC 5013L-10, manufactured by Polyplastics Co., Ltd.].

[0121] <Comparative Examples 1-5> In Comparative Examples 1-5, the resin bond is prepared in the same manner as in Example 1, except that the composition of the near-infrared absorbent composition is changed to the composition shown in Table 7 in "1. Preparation of near-infrared absorbent composition" of Example 1. In Comparative Example 4, the structure of cyanine compound 1 used as the near-infrared absorbent is shown below. Cyanine compound 1 is the same as cyanine compound 1 described in International Publication No. 2024 / 128016 and is synthesized by the method described in the above publication. In Comparative Example 5, the nigrosine used as the near-infrared absorbent is NUBIAN® BLACK 9801 manufactured by Orient Chemical Industries, Ltd.

[0122]

[0123] [Evaluation] 1. Bonding Strength The bonding strength of the resin joint shall be evaluated by the following method. The resin joint shall be tested according to the tensile shear bond strength test method of JIS K 6850:1999, and the first resin member and the second resin member shall be visually observed after the test. Based on the observation results, the evaluation shall be performed according to the evaluation criteria below. The test shall be performed using the Autograph AGS-5KNX (product name) manufactured by Shimadzu Corporation and the MTCH-350 (product name) constant temperature and humidity chamber for universal testing machine manufactured by ESPEC Corporation. The test shall be performed in an environment with an ambient temperature of 23°C. If the bonding strength of the resin joint is strong, substrate failure may occur, and if the bonding strength of the resin joint is weak, interfacial failure is likely to occur from the joint.

[0124] (Evaluation Criteria) A: Substrate failure is confirmed, but interface failure is not. B: Both substrate failure and interface failure are confirmed. C: Of the substrate failure and interface failure, only interface failure is confirmed, or the resin components do not bond and no resin bond is formed.

[0125] 2. Coloring of the Joint The coloring of the joint of the resin joint shall be evaluated by the following method. The joint of the resin joint shall be visually observed to confirm the presence and degree of coloring. Based on the results of the observation, an evaluation shall be performed according to the evaluation criteria below. For those in which no resin joint is formed, the overlapping portion of the first resin member and the second resin member shall be visually observed and evaluated. In Comparative Example 4, since the resin members are not joined, the coloring of the overlapping portion shall be evaluated. From the viewpoint of design, it is preferable for the resin joint to have no coloring at the joint.

[0126] (Evaluation Criteria) A: No discoloration is observed at the joint. B: Slight discoloration is observed at the joint. C: Clear discoloration is observed at the joint.

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134] In Tables 1 to 7, a "-" in the column for the composition of the near-infrared absorbent composition means that the component corresponding to that column is not included. Examples 1 described in Tables 2 and 4 to 6 are all described for comparison with the other examples described in Tables 2 and 4 to 6, and are the same examples as Example 1 described in Table 1. In Tables 1 to 7, "absorbance" means the absorbance of the near-infrared absorbent at the wavelength of maximum absorption in the near-infrared region (i.e., between 780 nm and 2500 nm), which is an indicator of the amount of near-infrared absorbent composition that is imparted.

[0135] The results shown in Tables 1 to 7 show that the bonding method of the example can bond resin members together with stronger bonding strength than the bonding method of the comparative example. Furthermore, the results shown in Table 6 show that, according to the bonding method of the example, by controlling the amount of near-infrared absorbent composition applied, it is possible to achieve both strong bonding between resin members and suppression of discoloration at the joint of the resin bonded body.

[0136] The disclosure of Japanese Patent Application No. 2024-166605, filed on 25 September 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A joining method for joining two resin members, at least one of which transmits laser light, comprising: step A, applying a near-infrared absorbing agent composition, which includes a near-infrared absorbing agent and at least one selected from the group consisting of metals and metal compounds, to the surface of at least one of the resin members, a first resin member and a second resin member; step B, bringing the first resin member and the second resin member into contact via a portion where the near-infrared absorbing agent composition is applied; and step C, irradiating the application portion with laser light to melt and join the first resin member and the second resin member at the application portion.

2. The method for joining resin members according to claim 1, wherein the near-infrared absorbing agent composition further comprises a perchlorate.

3. The method for joining resin members according to claim 1, wherein the near-infrared absorbing agent comprises at least one selected from the group consisting of diimonium compounds, cyanine compounds, squarylium compounds, azochelate compounds, phthalocyanine compounds, and naphthalocyanine compounds.

4. The method for joining resin members according to claim 1, wherein the near-infrared absorbent has perchlorate ions as counterions.

5. The method for joining resin members according to claim 1, wherein the metal compound is a metal perchlorate salt.

6. The method for joining resin members according to claim 1, wherein the metal compound comprises at least one selected from the group consisting of iron compounds, zinc compounds, copper compounds, and silver compounds.

7. The method for joining resin members according to claim 1, wherein the total content of the metal and the metal compound in the near-infrared absorbing agent composition is 0.000001 times by mass to 1 time by mass relative to the content of the near-infrared absorbing agent.

8. The method for joining resin members according to claim 1, wherein in step A, an amount of the near-infrared absorbing agent composition such that the absorbance at the maximum absorption wavelength of the near-infrared absorbing agent is 0.05 to 2 is applied to the surface of at least one of the first resin member and the second resin member.

9. The method for joining resin members according to claim 1, wherein the laser light has an oscillation wavelength of 700 nm to 1200 nm, and the light source is at least one selected from the group consisting of an Nd:YAG laser, a semiconductor laser, and a dye laser.

10. The method for joining resin members according to claim 1, wherein the material of the first resin member and the second resin member is a thermoplastic resin.

11. A near-infrared absorbing agent composition used in a method for joining resin members according to any one of claims 1 to 10, comprising a near-infrared absorbing agent and at least one selected from the group consisting of metals and metal compounds.

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