METAL COMPONENT PRODUCTION METHOD AND METAL-RESIN BOND PRODUCTION METHOD

Abstract

To provide a method for manufacturing a metal member having a joined surface for joining a resin molding so as to obtain a metal resin joined body having sufficient joint strength and excellent airtightness.SOLUTION: A method for manufacturing a metal member having a joined surface to an object to be joined thereon includes a laser irradiation step of irradiating a metal substrate with a laser beam, wherein in the laser irradiation step, energy E determined from Expression (2) based on Expression (1) satisfies 0.18≤E≤0.75. Expression (1): irradiation energy per unit area=(peak power)×(pulse width)×(set output%)×(irradiation time)×(frequency) / (irradiation area). Expression (2): energy E received by metal substrate=(irradiation energy per unit area)×(absorption rate of base material)2×√(heat diffusion constant) / (difference in temperature rise between temperature of metal substrate before laser irradiation and boiling point of metal substrate after laser irradiation).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a metal member having a joining surface for joining objects, and a method for manufacturing a metal-resin joined body in which a resin molded body, which is the joining object, is joined to the metal member. [Background technology]

[0002] In recent years, in the fields of various automotive sensor parts, home appliance parts, industrial equipment parts, and the like, metal-resin joined bodies have been widely used, and their applications are expanding, in which a metal substrate such as a copper substrate made of copper or a copper alloy, which has extremely high heat dissipation properties and electrical conductivity, or an aluminum substrate made of aluminum or an aluminum alloy, which has high heat dissipation properties and is lighter than other metals, is integrally joined to a resin molded body, which has high insulating properties, is lightweight, and is inexpensive.

[0003] A typical industrially suitable method for producing a metal-resin joined body in which a metal substrate and a resin molded body, which are dissimilar materials, are integrally joined to each other, is to insert a metal material into an injection molding die and inject a molten thermoplastic resin toward the surface of the inserted metal material to form a resin molded body.

[0004] In this case, for the purpose of further improving the bonding strength between the metal substrate and the resin molded body, it is known to roughen the metal substrate to form surface irregularities by irradiating it with laser light to heat it, or etching it with an acid aqueous solution. Among these, several studies have been conducted on the method of irradiating the metal substrate with laser light, because it is advantageous in terms of selectivity, allowing only the areas to be bonded with the resin to be treated, and waste liquid disposal after treatment is not an issue.

[0005] For example, in Patent Document 1, a laser is irradiated onto the joining surface of an aluminum die-cast member with a polymer member to melt the surface layer of the joining surface, and the laser irradiation density is set to 2 J / mm 2 More than 40J / mm 2 The following is a list of what you should do:

[0006] In addition, in Patent Document 2, in order to obtain a composite molded body consisting of a metal molded body and a resin molded body, an energy density of 1 MW / cm 2 In addition to the above, it is described that by irradiating a metal molded body with laser light at an irradiation speed of 2000 mm / sec or more, holes with a complex structure are formed on the surface of the metal molded body. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Republished Publication No. 2019 / 064344 [Patent Document 2] Japanese Patent Application Publication No. 2019-63875 Summary of the Invention [Problem to be solved by the invention]

[0008] In order to obtain a metal-resin joined body in which a metal substrate and a resin molded body are integrally joined to each other, various conditions of the laser light irradiated onto the metal substrate have been optimized in order to improve the joining strength, as in Patent Documents 1 and 2 described above.

[0009] However, in the conventional method, attention is focused only on the oscillation output of the laser device, and the characteristics of the metal substrate side to which the laser light is irradiated are not taken into consideration. Therefore, even if the metal substrate is irradiated with laser light at a predetermined oscillation output, if the energy received by the metal substrate is inappropriate, the resulting metal-resin bonded body may have insufficient bonding strength or may have poor airtightness between the metal substrate and the resin molded body.

[0010] Therefore, the present inventors conducted extensive research to solve the above problems, and as a result, they found that by controlling the energy received by the metal base material while taking into consideration the irradiation energy of the laser beam, it is possible to reproducibly obtain a metal-resin joined body having excellent joining strength and airtightness, and completed the present invention.

[0011] Therefore, an object of the present invention is to provide a method for producing a metal-resin bonded body that can reproducibly produce a metal-resin bonded body that has sufficient bonding strength and excellent airtightness. Another object of the present invention is to provide a method for manufacturing a metal member having a joining surface for joining a resin molded article to be joined, in order to obtain such a metal-resin joined body. [Means for solving the problem]

[0012] That is, the gist of the present invention is as follows. [1] A method for manufacturing a metal member having a joining surface for joining an object to be joined on its surface, a laser irradiation step of irradiating a surface of a metal substrate made of metal with laser light to form the joining surface having an uneven portion on the metal substrate; In the laser irradiation step, the energy E received by the metal substrate by irradiation with the laser light is calculated by the following formula (2) or (3) based on the irradiation energy per unit area calculated by the following formula (1): Calculate the energy E is 0.18≦E≦0.75 and setting the laser conditions so as to achieve the above, and performing the laser processing under the set laser conditions. A method for manufacturing a metal member comprising the steps of: Irradiation energy per unit area = (peak power) × (pulse width) × (set output) × (irradiation time) × (frequency) / (irradiation area) Formula (1) Energy received by the metal substrate E = (irradiation energy per unit area) x (absorption rate of the substrate) 2 ×√(thermal diffusion constant) / (difference in temperature rise from the temperature of the metal substrate before laser irradiation to the boiling point of the metal substrate after laser irradiation) Equation (2) Energy received by the metal substrate E = (irradiation energy per unit area) × (substrate absorption rate) × (vapor absorption rate) × √ (thermal diffusion constant) / (difference in temperature rise from the temperature of the metal substrate before laser irradiation to the boiling point of the metal substrate after laser irradiation) Equation (3) [2] The method for producing a metal component according to [1], wherein the metal substrate is aluminum, copper, iron, or an alloy containing any of these metals. [3] The method for manufacturing a metal member according to [1] or [2], characterized in that the surface roughness (Rz) of the joining surface is 30 μm or more and 180 μm or less. [4] A resin molding process is provided in which a resin molded body is formed on the surface of the metal member obtained by the manufacturing method according to [1]. A metal-resin joined body is manufactured by joining the joining surface of the metal member and the resin molded body. 1. A method for producing a metal-resin bonded body, comprising: [5] A method for producing a metal resin bonded body, wherein in the resin molding step, a resin molded body containing a thermoplastic resin or a thermosetting resin is molded on the metal member. [Effects of the Invention]

[0013] According to the present invention, it is possible to control the energy received by the metal substrate while taking into consideration the irradiation energy of the laser beam, and therefore it is possible to reproducibly produce a metal-resin joined body having excellent joining strength and airtightness. Moreover, since this method can be applied regardless of the various conditions of the laser beam or the type of metal substrate, it can be said to be a highly practical method. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing the relationship between the beam diameter of a laser beam and the irradiation interval. [Figure 2] FIG. 2 is a diagram for explaining an outline of the bonding strength evaluation (1) (shear test). [Figure 3] FIG. 3 is a diagram for explaining an outline of the bonding strength evaluation (2) (shear test). [Figure 4]FIG. 4 is a diagram for explaining an outline of the evaluation of the airtightness of a metal-resin bonded body. [Figure 5] FIG. 5 is a diagram for explaining an outline of the evaluation of the airtightness of a metal-resin-metal bonded body. [Figure 6] FIG. 6 is a schematic diagram illustrating the metal members in the metal-resin bonded body used in the evaluation of bonding strength, where (a) shows the bonding surface of the metal members and (b) shows the trajectory of the laser light on the bonding surface. [Figure 7] FIG. 7 is a schematic diagram illustrating the metal members in the metal-resin bonded body used in the airtightness evaluation, where (a) shows the bonded surface of the metal members and (b) shows the trajectory of the laser light on the bonded surface. [Figure 8] FIG. 8 is a diagram showing an outline of a metal-resin bonded body for evaluation of bonding strength. [Figure 9] FIG. 9 is a diagram showing an outline of the metal-resin bonded body for the evaluation of airtightness. [Figure 10] FIG. 10 is a diagram showing an outline of a metal-resin-metal bonded body for evaluation of bonding strength according to Example 25. As shown in FIG. [Figure 11] FIG. 11 is a diagram showing an outline of a metal-resin-metal bonded body for evaluation of airtightness according to Example 25. As shown in FIG. [Figure 12] FIG. 12 is a scanning electron microscope photograph of the metal-resin bonded body of Comparative Example 1 cut in the thickness direction to observe the cross section. [Figure 13] FIG. 13 is a scanning electron microscope photograph of the metal-resin bonded body of Example 1 cut in the thickness direction to observe the cross section. [Figure 14] FIG. 14 is a scanning electron microscope photograph of the metal-resin bonded body of Comparative Example 2 cut in the thickness direction to observe the cross section. [Figure 15] FIG. 15 is a graph showing the relationship between the "energy E received by the metal base material" when forming the joining surface of the metal member and the surface roughness Rz of the joining surface for the metal-resin joined bodies of Examples 1 to 25 and Comparative Examples 1 to 8. DETAILED DESCRIPTION OF THE INVENTION

[0015] The method for producing a metal member and the method for producing a metal-resin bonded body according to the present invention will be described in detail below. The components of the present invention described below can be combined in part or in whole as appropriate.

[0016] [1. Metallic components and metal-resin joints] The metal member of the present invention has a surface to be joined with an object to be joined, and is obtained by a laser irradiation process in which a surface of a metal substrate made of metal is irradiated with laser light to form a joining surface having projections and recesses. The metal-resin joined body of the present invention is obtained by joining the joining surface of the metal member obtained as described above with a resin molded body.

[0017] [1-1. Metallic Components] <Metal base material> First, the metal substrate used in the metal member of the present invention may be a copper substrate made of copper or a copper alloy, an iron substrate made of iron or an iron alloy, or an aluminum substrate made of aluminum or an aluminum alloy. The material is not limited, and can be selected based on the application of the metal-resin bonded body formed therefrom and various physical properties required for that application, such as strength, corrosion resistance, and processability. Examples of suitable materials include processed materials obtained by appropriately processing them into a desired shape, and combined materials obtained by appropriately combining these processed materials. Depending on the application, a substrate with a thickness of approximately 0.3 mm to 10 mm is typically used. Typically, an oxide film is formed on the surface of the metal substrate. The oxide film may be a natural oxide film formed naturally in the atmosphere, or an anodic oxide film formed by anodizing. It may also be a rolled oxide film formed by hot rolling.

[0018] <Objects to be joined> The object to be joined with the metal substrate is not particularly limited as long as it is a material that can be joined with the metal substrate. It is preferable to use a material that can be joined at a temperature lower than the melting point of the metal substrate. Such an object to be joined is preferably a resin molded body made of a resin material. The resin molded body will be described later.

[0019] <Joint surface> The bonding surface formed on the metal substrate may be only a portion of one side of the metal substrate, the entire surface, or a portion or entire surface of both sides, as long as the bonding surface is formed in the necessary portion depending on the intended use. Furthermore, there are no particular limitations on the shape, size, arrangement, etc. of the bonding surface. The same applies to combined materials, etc. In this disclosure, the term "bonding surface" refers to the area where the metal substrate and resin are to be bonded, and refers to the area where a predetermined treatment has been applied to the surface of the metal substrate for bonding with the resin. In contrast, the area where the metal substrate and resin are bonded is referred to as a "bonding portion" to distinguish it from the above.

[0020] <Uneven part> It is preferable that a hydroxyl-containing coating containing hydroxyl groups is formed on the joining surface. It is more preferable that a hydroxyl-containing coating is formed over the entire surface of the joining surface. The joining surface has an uneven portion, and it is preferable that a hydroxyl-containing coating formed by laser treatment is formed over the entire surface of this uneven portion. Furthermore, this uneven portion has, macroscopically, a "macro uneven portion" in which concave and convex portions are formed alternately and continuously, and a "fine uneven portion" formed on the surface of the macro uneven portion.

[0021] The hydroxyl group-containing coating contains, depending on the metal constituting the metal substrate, a hydroxide (metal hydroxide) or an oxide hydroxide (metal oxide hydroxide) of the metal constituting the metal substrate, such as aluminum hydroxide (Al(OH)), aluminum oxide hydroxide (AlO(OH)), copper hydroxide (Cu(OH)), iron(II) hydroxide (Fe(OH)), or iron(III) oxide hydroxide (FeO(OH)). The hydroxyl group-containing coating may also contain, depending on the metal constituting the metal substrate, an oxide (metal oxide) of the metal constituting the metal substrate, such as aluminum oxide (AlO), copper(I) oxide (CuO), copper(II) oxide (CuO), iron(II) oxide (FeO), iron(II,III) oxide (FeO), or iron(III) oxide (FeO).

[0022] On the surface of the metal substrate, a deposit is formed in the form of a film, in which metal oxides formed due to laser irradiation accumulate around the irradiated area. The metal fusing layer made of such deposits contains oxygen as the metal oxide as described above. The metal fusing layer has a hydroxyl-containing film having hydroxyl groups in the outermost layer. In the present invention, as described above, it is preferable that the entire joining surface is covered with a hydroxyl-containing film having macro-irregularities and micro-irregularities.

[0023] It has been previously believed that, in order to increase the bonding strength of metal-resin bonded bodies, it is effective to form macroscopic irregularities with a predetermined opening diameter and depth when treating a metal material with laser light, thereby forming a structure that facilitates mechanical interaction by the resin penetrating. It has also been known that the molten portion of the metal substrate formed by the laser treatment is an oxygen-containing film containing oxygen, and that this oxygen-containing film contributes to the development of bonding strength. After detailed studies, the present inventors have newly discovered that this oxygen-containing film has a structure with fine nano-sized openings (fine irregularities). The inventors have concluded that, in order to further increase the bonding strength and airtightness of metal-resin molded bodies, it is effective to allow the resin to penetrate into these fine irregularities and to effectively utilize the effects of chemical bonding between the functional groups of the oxygen-containing film and the functional groups in the resin. Furthermore, they came to the conclusion that forming such an oxygen-containing film over the entire surface of the joining surface will ensure sufficient interaction between the resin and the oxygen-containing film, and that it will be even more effective to adjust the shape of the macro-irregularities, particularly the depth relative to the opening diameter of the recesses, to create a structure that allows the resin to penetrate relatively easily, while preventing the resin that penetrates from becoming too shallow (so that the interaction between the resin and the oxygen-containing film is not weakened).From this perspective, they discovered that by forming a joining surface on the surface of the metal base material, when joined to a resin molded body, a high joining strength can actually be obtained, and a metal resin molded body that can ensure sufficient airtightness can be obtained.

[0024] Furthermore, by providing a hydroxyl-containing coating having macro- and micro-asperities, chemical bonding through hydrogen bonding is achieved between the hydroxyl groups present on the surface of the metal component and the functional groups present on the surface of the resin molded body. Furthermore, by having macro-asperities on the order of μm that satisfy a predetermined opening diameter (D), depth (L), and aspect ratio (L / D), the hydroxyl-containing coating provides a mechanical bond (anchor effect) between the macro-asperities and the resin molded body. Here, the hydroxyl-containing coating has macro-asperities of a predetermined shape, allowing the resin to penetrate deep into the recesses of the macro-asperities. Furthermore, the hydroxyl-containing coating has macro-asperities on the order of μm, and micro-asperities on the surface of the macro-asperities on the order of nm. This increases the surface area of the hydroxyl-containing coating presented on the joining surface, thereby increasing the amount of hydroxyl groups that interact with the resin molded body. Furthermore, in the metal member and metal-resin bonded body of the present invention, a hydroxyl-containing coating is formed over the entire bonding surface, thereby suppressing a decrease in bonding strength and airtightness that would occur in areas where the hydroxyl-containing coating is not present. Thus, according to the present invention, the effects of mechanical and chemical bonding are exerted over the entire bonding surface, and the metal member and resin molded body can be bonded with the resin permeating the macro-asperity and micro-asperity portions, thereby increasing the area of the bonding surface that contributes to the mechanical and chemical bonding. Therefore, the metal member and metal-resin bonded body of the present invention strengthen the effects of the mechanical and chemical bonding between the metal member and resin molded body, making it possible to improve bonding strength and airtightness.

[0025] In this specification, "the entire surface to be bonded" does not necessarily mean 100% of the surface area of the surface to be bonded, and does not exclude the case where there are very small spots of the surface that are not covered with the hydroxyl-containing film due to unirradiated areas. Preferably, 90% or more, more preferably 95% or more of the surface to be bonded is covered with the hydroxyl-containing film.

[0026] <Macro unevenness> The macro-relief is a structure having a micrometer-order irregular shape and is formed on the surface of the hydroxyl group-containing coating. The macro-relief has a structure consisting of recesses formed by perforating the metal substrate upon irradiation with laser light and protrusions consisting of metal oxide deposits formed by irradiation with laser light. Multiple laser light irradiations are performed adjacent to each other, resulting in a repeating structure consisting of recesses and protrusions. The macro-relief can be confirmed by observing the surface or cross section of the metal member using, for example, a scanning electron microscope (SEM).

[0027] <Minute unevenness> The fine irregularities are structures having irregular shapes on the order of nm, and are formed on the macro irregularities on the surface of the hydroxyl-containing coating. The fine irregularities are formed on the surface of the hydroxyl-containing coating when a metal melt layer having the hydroxyl-containing coating is formed by laser irradiation. The fine irregularities can be confirmed by observing the surface or cross section of the metal member using, for example, a scanning electron microscope.

[0028] [1-2. Resin molded body] Next, we will explain a resin molded body that is suitable for use as a joining object for a metal member having a predetermined joining surface. The resin molded body can be formed by molding a resin composition onto the surface of the metal member. The resin molded body contains a thermoplastic resin or a thermosetting resin.

[0029] The thermoplastic resin can be selected from known resins depending on the application, and examples thereof include polyamide resins (aliphatic polyamides such as PA6 and PA66, and aromatic polyamides), polystyrene, copolymers containing styrene units such as ABS resin and AS resin, polyethylene, copolymers containing ethylene units, polypropylene, copolymers containing propylene units, other polyolefins, polyvinyl chloride, polyvinylidene chloride, polycarbonate resins, acrylic resins, methacrylic resins, polyester resins, polyacetal resins, and polyphenylene sulfide resins, and these can be used alone or in combination of two or more. Among these, polyamide resins and polyphenylene sulfide resins are preferred because they have high fluidity during resin molding and easily penetrate into recesses.

[0030] The thermosetting resin can be appropriately selected from known resins depending on the application, and examples thereof include urea resins, melamine resins, phenolic resins, resorcinol resins, epoxy resins, polyurethanes, and vinyl urethanes, and these can be used alone or in combination of two or more. Among these, it is preferable to use epoxy resins, acrylic resins, and urethane resins, because reaction-curing adhesives are compatible with hydroxyl group-containing films and can provide high bonding strength as the reaction area increases.

[0031] Furthermore, adhesives can also be used as the resin molded body. Examples of adhesives include the above-mentioned thermoplastic resins or thermosetting resins, or other elastomers or rubbers, and compounds exhibiting adhesive properties. The adhesive can be selected from known adhesives as appropriate depending on the application. For example, dry-solidifying adhesives include acrylic resin emulsions, rubber latexes, vinyl acetate resin solvents, vinyl copolymer resin solvents, and rubber solvents. Reaction-curing adhesives include epoxy resins, urethane resins, and modified silicone resins, and these can be used alone or in combination. Among these, reaction-curing adhesives are preferably epoxy resins, acrylic resins, or urethane resins because they are compatible with hydroxyl-containing coatings and can achieve high bonding strength as the reaction area increases.

[0032] Furthermore, thermoplastic elastomers can be used, such as styrene-based elastomers, vinyl chloride-based elastomers, olefin-based elastomers, urethane-based elastomers, polyester-based elastomers, nitrile-based elastomers, and polyamide-based elastomers, and these can be used alone or in combination of two or more.

[0033] Furthermore, in each of the above resins (resin compositions), in order to further improve performance such as adhesion to metal members, mechanical strength, heat resistance, dimensional stability (resistance to deformation, warpage, etc.), and electrical properties, fibrous, granular, plate-like fillers, and various elastomer components can be added.

[0034] Furthermore, known additives that may generally be added to the resin (resin composition), namely, flame retardants, colorants such as dyes and pigments, stabilizers such as antioxidants and ultraviolet absorbers, plasticizers, lubricants, slip agents, mold release agents, crystallization accelerators, crystal nucleating agents, etc., may be added appropriately to the resin (resin composition) within a range that does not impair the required performance or the object of the present invention.

[0035] [1-3. Metal-resin bonded body] A metal-resin bonded body is formed with the resin embedded in the bonding surface (macro-concave and micro-concave portions) of the surface of the metal member, and the metal member and the resin molded body are integrally bonded via the bonding surface. The metal member and the resin molded body may be bonded using one metal member and one resin molded body, or a plurality of either or both may be bonded, or a plurality of sets of these may be laminated in any order, and this can be determined appropriately depending on the application.

[0036] For example, the metal-resin bonded body may be a metal-resin bonded body in which a metal member and a resin molded body are bonded together in a stacked or continuous arrangement. Alternatively, the metal-resin bonded body may be a metal-resin-metal bonded body in which a metal member, a resin molded body, and a metal member are bonded together in a stacked or continuous arrangement in this order. Alternatively, the metal-resin bonded body may be a resin-metal-resin bonded body in which a resin molded body, a metal member, and a resin molded body are bonded together in a stacked or continuous arrangement in this order.

[0037] When the metal resin bonded body is a metal-resin-metal bonded body in which two or more metal members are bonded via a resin molded body, the bonded body may include a resin molded body formed by molding a thermoplastic resin or a thermosetting resin and sandwiched between metal members. Alternatively, the bonded body may be a resin molded body in which an adhesive containing a thermoplastic resin or a thermosetting resin is used as the resin molded body and the metal members are bonded via the adhesive.

[0038] [2. Methods for producing metal members and metal-resin bonded bodies] The method for producing a metal member of the present invention is a method for producing a metal member having a surface to be bonded to an object to be bonded, and includes a laser irradiation step of irradiating a surface of a metal substrate made of metal with laser light to form a bonding surface having macro-convex and concave portions on the metal substrate. The method for producing a metal-resin bonded body of the present invention also includes a resin molding step of bonding a resin molded body to the surface of the metal member obtained above.

[0039] [2-1.Metal component manufacturing method] <Preparation process> The method for producing a metal member of the present invention may include a preparation step of performing pretreatment such as degreasing, etching, desmutting, chemical polishing, and electrolytic polishing as a pretreatment of the surface of the metal substrate prior to the laser irradiation step.

[0040] <Laser irradiation process> In the present invention, a treatment is performed in which a surface of a metal substrate made of metal is irradiated with laser light (hereinafter simply referred to as "laser treatment" or the like). A joining surface with an object to be joined is formed by the laser treatment, thereby obtaining the metal member according to the present invention. Here, although known lasers can be used as the laser, it is preferable to use a pulsed laser, such as a YAG laser, a YVO4 laser, a semiconductor laser, or a fiber laser, because this is advantageous for spot-processing the metal substrate as in the present invention.

[0041] The principle behind the formation of a joining surface with macro-convex and concave portions on a metal substrate by this laser treatment is roughly as follows: the metal substrate is melted and evaporated by the energy of the laser irradiation, and the spaces created by the evaporation become the bases of the concave portions, and the areas on both sides (neighboring sides) of the concave portion that are not irradiated by the laser become the bases of the convex portions. At the same time, the molten metal portion is oxidized in part or in whole to become metal oxide, which is deposited around the irradiated area that will become the concave portion, forming the convex portion. The deposit made of metal oxide forms a film-like film that covers the concave and convex portions. In this way, the deposit made of metal oxide formed on the surface of the metal substrate forms a molten metal layer that forms the concave and convex shape of the macro-convex portion. Furthermore, metal oxides have at least some partial ionicity, and the ionic surface of the metal oxide contains metal ions (Al 3+ ) and oxide ions (O 2-) are present. Due to electrostatic neutrality, reaction with moisture in the air causes hydroxylation of the metal oxide present on the surface of the metal fusing layer, and the surface of the metal fusing layer becomes covered with hydroxyl groups. In this way, macroscopic irregularities are formed on the metal substrate, and a hydroxyl-containing coating containing hydroxyl groups is formed on the outermost layer of the metal fusing layer. Note that, when focusing on this hydroxyl-containing coating, it has macroscopic irregularities in which concave and convex portions are formed alternately and continuously, and fine irregularities formed on the surface of the macroscopic irregularities.

[0042] In addition, when a laser-unirradiated portion exists on a metal component, there is no metal melt layer in the laser-unirradiated portion, and no hydroxyl-containing coating as described above. Usually, an oxide coating is formed in the laser-unirradiated portion. Since the laser-unirradiated portion does not have a hydroxyl-containing coating, there is no improvement in airtightness due to chemical bonding caused by hydroxyl groups when bonding with a resin molded body. Furthermore, when the laser-unirradiated portion is flat, there is no improvement in bonding strength due to mechanical bonding caused by macro-irregularities. Therefore, when a large portion of the laser-unirradiated portion remains on the bonding surface and a hydroxyl-containing coating is not formed on the entire bonding surface, the airtightness and bonding strength of the metal-resin bonded body are reduced.

[0043] <Energy E received by the metal substrate during the laser irradiation process> In the present invention, based on the irradiation energy of the laser beam per unit area calculated by the following formula (1), the energy E received by the metal substrate calculated by the following formula (2) or (3) is set to be in the range of 0.18≦E≦0.75. Irradiation energy per unit area (J / m 2 ) = (Peak power (W)) x (Pulse width (s)) x (Set output (%)) x (Irradiation time (s)) x (Frequency (Hz)) / (Irradiation area (m 2 )) ...Equation (1) Energy received by the metal substrate E (J / (m K √s)) = (Irradiation energy per unit area (J / m 2 )) × (substrate absorption rate (%)) 2 ×√(thermal diffusion constant (m2 / s) / (difference in temperature rise from the temperature of the metal substrate before laser irradiation to the boiling point of the metal substrate after laser irradiation (K)) Equation (2) Energy received by the metal substrate E (J / (m K √s)) = (Irradiation energy per unit area (J / m 2 )) × (substrate absorption rate (%)) × (vapor absorption rate (%)) × √ (thermal diffusion constant (m 2 / s) / (difference in temperature rise from the temperature of the metal substrate before laser irradiation to the boiling point of the metal substrate after laser irradiation (K)) Equation (3)

[0044] As described above, when a metal substrate is irradiated with a laser, the temperature of the irradiated metal substrate rises due to the energy applied, melts, vaporizes, and explodes, scattering part of the metal substrate to form a hole. The part of the metal substrate that did not completely evaporate explodes and deposits around the hole. At this time, the energy applied by the laser is absorbed by the metal substrate and used to increase the temperature of the substrate. The evaporated metal substrate then absorbs the energy, and the energy applied to the metal substrate decreases. Furthermore, the temperature of the metal substrate rises at this time, but the energy is dispersed by thermal diffusion.

[0045] Based on these considerations, the formulas (1) to (3) according to the present invention were calculated. That is, in order to understand the influence of laser light irradiation on a metal substrate, it is first necessary to clarify the melting and evaporation phenomena of the metal substrate that accompany laser irradiation. However, these phenomena occur in a small area and in a short time, making them difficult to observe directly. For this reason, analysis using, for example, molecular dynamics simulations has been conducted. Reference 1 (Etsuji Omura et al., Molecular Dynamics Simulation of Laser Ablation Phenomenon, Laser Research 26, 800 (1998)) describes a simulation of laser ablation, in which a material surface is instantaneously melted and evaporated by irradiation with high-energy-density short-pulse laser light.

[0046] In this reference 1, a power density of 10 GW / cm is used for aluminum. 2The evaporation process of Al when irradiated with a Gaussian beam of approximately 28 nm width for 3 ps is illustrated in the figure. Initially, the surface rises due to thermal expansion, and many small voids are generated in the liquid phase. As these voids combine and grow larger, they explode, scattering the atoms into relatively large clumps. Furthermore, the molten metal that did not completely evaporate becomes spherical due to surface tension and accumulates around the holes, resulting in the formation of a rise around the holes (see Fig. 5, first paragraph in the left column on page 804).

[0047] On the other hand, even with the same aluminum, the power density is 1 GW / cm 2 When the Gaussian beam is irradiated for 30 ps (with the same beam width), the evaporated atoms form small clusters and scatter apart. In this case, the explosive evaporation seen in the previous case is not observed, and the molten metal overflows from the hole and accumulates around it, resulting in a shallower hole depth than in the previous case (see Fig. 6, second paragraph in the left column on page 804).

[0048] Therefore, in the present invention, the energy E received by the metal substrate by irradiation with laser light is defined as that defined by the above formula (2) or (3). In other words, it is thought that the energy from the irradiation with laser light is absorbed by the metal substrate through thermal diffusion, causing the temperature of the metal substrate to rise and evaporate, and that the metal substrate absorbs energy through metal vapor and forms a molten zone, resulting in the formation of surface irregularities. Therefore, formulas (2) and (3) take these factors into consideration.

[0049] Regarding the above formula (2) or (3), the "irradiation energy per unit area (J / m 2 ) can be calculated using the above formula (1). 2"Thermal diffusion coefficient" represents the laser beam energy received per unit area by the laser-irradiated portion of a workpiece when a pulsed laser containing pulses with a specified peak power, pulse width, and frequency is applied at a specified output power and irradiation time. "Substrate absorptivity" indicates the absorptivity of a metal substrate (solid) to a laser light source. However, since absorptivity varies depending on the wavelength of the laser light source, it is calculated by subtracting the reflectivity (%) of the metal substrate actually used to manufacture a metal-resin bonded body from 100 (%) (100 - reflectivity). The reflectivity of the metal substrate is measured using a UV-visible spectrophotometer to measure the relative reflectivity of the laser wavelength used in accordance with the measurement regulations of JIS K 0115:2020. "Thermal diffusion constant" indicates the ease with which heat spreads within a metal substrate; a high value is thought to result in a shallower macro-irradiated structure. Here, the calculation is made by dividing the metal substrate's thermal conductivity by (specific gravity x specific heat), where the thermal conductivity, specific gravity, and specific heat are physical properties of each metal substrate. Furthermore, the "temperature rise difference between the temperature of the metal substrate before laser irradiation and the boiling point of the metal substrate after laser irradiation" is the temperature difference (T2 - T1) obtained by subtracting the actual temperature of the metal substrate before laser irradiation, T1, from the boiling point T2 (physical property) of the metal substrate.

[0050] The reason why the root (1 / 2 power) of the "thermal diffusion constant" is used in the above formulas (2) and (3) is that in Reference 2 (Tatsuya Kikuchi et al., Fabrication of Metal Microstructures Using Anodic Oxidation of Al and Laser Irradiation - Aiming for a New LIGA Process -, Surface Chemistry, Vol. 50, No. 8 (1999) 697-704), the minimum energy E required to cause laser ablation of a metal substrate is ab is known to be expressed by the following formula (see Reference 2, page 698, right column, lines 31-39), and this is the basis for this. E ab =2H1ρk 1 / 2 τ -1 / 2 (In the formula, H1, ρ, and k represent the latent heat of vaporization, density, and thermal diffusion constant of the metal, respectively, and τ represents the pulse width.)

[0051] Furthermore, the "vapor absorptivity" in formula (3) can be used to calculate the absorptivity of a metal substrate (vapor) based on the same concept as the "substrate absorptivity" described above. However, since it is difficult to actually measure metal vapor, it can be considered to be the same as the "substrate absorptivity," which is the energy absorption rate of a metal substrate (solid), and can be treated as the square of the "substrate absorptivity," as shown in formula (2).

[0052] In the present invention, the oscillation output of the laser device is determined by the above formula (1). The "peak power" in formula (1) is calculated by dividing the pulse energy, which represents the energy of one pulse of the pulsed laser, by the pulse width. The higher this value, the deeper the surface irregularities of the metal substrate formed by laser irradiation. The "pulse width" is the time width per pulse emitted from the pulsed laser and affects the peak power. The "set output" represents the laser oscillation output, and the higher this value, the deeper the surface irregularities. The "frequency" represents the number of laser pulses per second. Of these, the peak power and frequency are typically unique to each laser device. In contrast, the pulse width and set output are typically configurable when irradiating laser light. Of course, laser devices that allow for configurable peak power and frequency may also be used.

[0053] The "irradiation time" and "irradiation area" are irradiation conditions when a metal substrate is irradiated with laser light. The "irradiation time" is the cumulative total of the time during which the surface of the metal substrate is irradiated with laser light and the time during which the surface is not irradiated with laser light. The time during which the laser light is irradiated refers to the time during which the metal substrate is irradiated with a pulsed laser. As an example, as shown in Figure 6, consider a case in which the laser light is irradiated onto the linear portions shown in black, and then the laser light is irradiated onto the linear portions shown in white, leaving intervals between them, to create a striped pattern. In this case, the laser light is first scanned in one direction from the starting point to the end point. Next, the laser light is turned back in the opposite direction without irradiating the laser light, moving to the next starting point at a predetermined interval. Then, the laser light is again scanned in one direction from the starting point to the end point. This process is then repeated. Thus, when irradiating the laser beam, there are sections on the target (workpiece) where the laser beam output is turned on and irradiated, sections where the laser beam is not irradiated (turned off) and the workpiece moves, and sections where the laser beam is not output at the transition point between these sections. The time when the laser beam is not irradiated refers to the time required for such sections where the laser beam is not irradiated. Furthermore, the "irradiation area" is synonymous with the area of the joining surface for joining the resin molded body.

[0054] In the present invention, the energy E (J / (m·K·√s)) received by the metal substrate, as calculated by the above formula (2) or (3), is typically 0.18 or more, preferably 0.2 or more, more preferably 0.3 or more, and even more preferably 0.4 or more, and typically 0.75 or less, preferably 0.7 or less, more preferably 0.6 or less, and even more preferably 0.5 or less. The surface of the metal substrate is irradiated with a laser beam so as to form surface irregularities within this range, thereby obtaining a metal member having a joining surface for joining a resin molded article, which is the object to be joined. When this energy E (J / (m·K·√s)) is equal to or greater than the above lower limit, the metal substrate receives energy from the laser, forming macro-irregularities with holes of sufficient depth, which effectively exerts the anchoring effect and facilitates good joining of the resin molded article. Conversely, when the energy E (J / (m·K·√s)) is below the upper limit, the energy is kept appropriately low, preventing the hole depth from becoming too deep relative to the hole opening diameter, allowing the resin to reach deep into the hole without leaving any voids, making it easier to ensure sufficient airtightness.

[0055] <Laser treatment conditions> In the present invention, as described above, laser treatment of a metal substrate is performed so that the energy E received by the metal substrate, which is calculated by formula (2) or (3), falls within a predetermined range based on the irradiation energy of the laser light per unit area calculated by formula (1). Taking this into consideration, it is preferable to set the individual treatment conditions for the laser treatment as follows.

[0056] Laser processing is also affected by energy density. Energy density represents the laser power received per unit area and per unit time by the laser irradiated part of the object (workpiece) that is the target of laser processing. Energy density (J / mm 2) can also be expressed by the following formula (A1) using the laser light output W (W), the number of laser light scans N (times), the laser light irradiation interval C (mm), the laser light scanning speed V (mm / s), the length of the laser irradiated area perpendicular to the irradiation direction of the laser light Length, and the width of the laser irradiated area parallel to the irradiation direction of the laser light Width. Energy density = (((Length / C) × Width × N) / V) × W) / (Length × Width) Equation (A1) Moreover, by modifying this formula (A1), the following formula (A2) is obtained, and the energy density can be calculated using formula (A2). Energy density = (W × N) / (C × V) Equation (A2)

[0057] The energy density is preferably 0.5 J / mm 2 That's all. As the energy density increases, fine irregularities containing hydroxyl groups are more likely to form on the joining surface of the metal member subjected to laser treatment. Also, a hydroxyl-containing coating with a predetermined hydroxyl group abundance ratio is more likely to be formed. Furthermore, as the energy density increases, the depressions in the macro irregularities formed on the surface of the metal substrate tend to become deeper, and the surface roughness of the metal member after laser treatment tends to increase. Note that the higher the melting point and the greater the thermal diffusion of the metal constituting the metal substrate, the less susceptible the metal substrate tends to be to the effects of laser light. Taking the above-mentioned circumstances into consideration, it is desirable to change the energy density according to the metal to be treated with the laser.

[0058] When performing laser processing on a metal substrate containing aluminum as the main metal, the energy density is preferably 0.5 J / mm 2 More than 1 J / mm 2 More preferably, 1.5 J / mm 2 In addition, when performing laser processing on a metal substrate containing aluminum as the main metal, the energy density is preferably 5 J / mm 2 Less than 4J / mm 2 Less than 3 J / mm 2The following is the result.

[0059] When performing laser processing on a metal substrate mainly made of iron, the energy density is preferably 1 J / mm 2 More than 2J / mm 2 More preferably, 3 J / mm 2 In addition, when performing laser processing on a metal substrate containing iron as the main metal, the energy density is preferably 10 J / mm 2 Less than or equal to 8 J / mm 2 Less than 6 J / mm 2 The following is the result.

[0060] When laser processing is performed on a metal substrate containing copper as the main metal, the energy density is preferably 2 J / mm 2 More than 4J / mm 2 More preferably, 6 J / mm 2 In addition, when performing laser processing on a metal substrate containing copper as the main metal, the energy density is preferably 20 J / mm 2 Less than or equal to 15 J / mm 2 Less than 10 J / mm 2 The following is the result.

[0061] When the energy density is equal to or greater than the lower limit, fine irregularities having hydroxyl groups are easily formed on the surface of the laser-treated metal member. Furthermore, a hydroxyl-containing coating having a predetermined hydroxyl group abundance ratio is easily formed. Therefore, the fine irregularities having hydroxyl groups and the hydroxyl-containing coating are likely to improve the airtightness and bonding strength of the metal-resin bonded body. Furthermore, when the energy density is equal to or greater than the lower limit, the depth (L) of the recesses of the macro-irregularities formed on the surface of the metal substrate tends to increase, and the aspect ratio (L / D) tends to increase. Therefore, when the resin molded body penetrates into the macro-irregularities, a mechanical bond (anchor effect) between the macro-irregularities and the resin molded body is exerted, which tends to improve the bonding strength. When the energy density is equal to or less than the upper limit, the depth (L) of the recesses of the macro-irregularities formed on the surface of the metal substrate tends to increase, and the aspect ratio (L / D) tends to increase. Therefore, the resin molded body can penetrate deep into the recesses of the macroscopic unevenness, and chemical bonding between the hydroxyl groups of the metal member and the functional groups of the resin molded body is achieved throughout the entire macroscopic unevenness, which facilitates improved airtightness. Furthermore, the protrusions of the macroscopic unevenness can be prevented from becoming elongated and pointed, thereby suppressing a decrease in mechanical strength due to breakage of the protrusions. Furthermore, fracture of the metal member can be prevented when the metal-resin bonded body breaks.

[0062] The laser conditions (laser processing conditions) for laser processing may be appropriately set to achieve the above-mentioned energy density. Parameters of the laser processing conditions include the laser beam output (W), laser beam frequency (kHz), laser beam diameter (μm), laser beam irradiation interval (μm), laser beam scanning speed (mm / s), and the number of laser beam scans. The number of scans refers to the number of times the laser beam is repeatedly applied along the same irradiation path. The relationship between the laser beam diameter and the irradiation interval will be explained with reference to FIG. 1. The laser beam irradiation interval refers to the distance between the path 6 of one laser beam irradiated onto the target object and the path 6' of another laser beam irradiated adjacent to the laser. More specifically, the laser beam irradiation interval refers to the distance between the end of the path 6 of one laser beam on either side in the direction perpendicular to the scanning direction 3 and the end of the path 6' of the other laser beam on the same side as the one laser beam. When a pulsed laser is used, the laser beam path is represented by a continuous path of pores formed by individual laser pulses. In this case, the laser beam irradiation interval 5 corresponds to the sum of the width of the region sandwiched between the trajectories of the laser beam formed by the continuous pores and the size of the beam diameter 4. Table 1 shows examples of laser treatment conditions when the main metal of the metal substrate to be treated with laser is aluminum, iron, or copper.

[0063] [Table 1]

[0064] The joining surface of the metal member obtained by the present invention preferably has a surface roughness Rz of 30 μm or more, more preferably 40 μm or more, even more preferably 60 μm or more, particularly preferably 80 μm or more, and preferably 180 μm or less, more preferably 160 μm or less, and even more preferably 140 μm or less. If the surface roughness Rz is equal to or greater than the above-mentioned lower limit, the joining strength of the resulting metal-resin joined body is improved, interfacial failure is prevented, and resin failure is more likely to occur. If the surface roughness Rz is equal to or less than the above-mentioned upper limit, the airtightness of the resulting metal-resin joined body is more likely to be improved. Note that this surface roughness Rz represents the maximum height according to JIS B 0601-2001. The surface roughness Rz can be measured by the method described in the examples.

[0065] [2-2. Method for manufacturing metal-resin bonded body] The metal-resin bonded body is produced by molding a resin molded body onto the surface of a metal member using a resin composition as a raw material.

[0066] Here, as a method for molding the resin composition (forming a resin molded body), a suitable molding method can be adopted according to the resin used. For example, when a thermoplastic resin is used, a composition containing a thermoplastic resin is injection-molded onto a metal member to integrally bond the resin molded body to obtain a metal-resin bonded body, or a resin molded body is first obtained by injection molding, and then the obtained resin molded body is integrally bonded to the surface of a metal member by thermocompression bonding using means such as laser welding, vibration welding, ultrasonic welding, hot press welding, hot plate welding, non-contact hot plate welding, or high-frequency welding, but is not limited thereto.

[0067] Furthermore, for example, when a thermosetting resin is used, examples of methods include, but are not limited to, a metal-resin bonded body obtained by injection-molding a composition containing the thermosetting resin onto a metal member to integrally bond the resin molded body, or a method in which a composition adjusted to a predetermined viscosity is applied onto a metal member and then the metal member is subjected to compression molding by heating and pressurizing the entire body.

[0068] Furthermore, when an adhesive is used, it can be applied to the metal member and dried to harden, but if necessary, operations such as heating can be performed, and molding conditions suitable for the adhesive used can be adopted.

[0069] [3. Action and Effects]

[0070] In the method for manufacturing a metal member according to the present invention, a bonding surface having an uneven surface is formed by laser processing, in which a laser beam is irradiated onto the surface of a metal substrate. This makes it possible to improve the bonding strength and airtightness of the resulting metal member and resin molded article. Furthermore, according to the present invention, it is possible to control the energy received by the metal substrate while taking into account the irradiation energy of the laser beam, thereby enabling the reproducible production of a metal-resin bonded body having excellent bonding strength and airtightness. Furthermore, the present invention is a highly practical method that can be applied regardless of the laser beam conditions or the type of metal substrate. In other words, the present invention allows the laser beam to be irradiated by appropriately setting the energy E received by the metal substrate by setting the laser processing conditions according to the performance of the laser beam irradiation device and the type of metal substrate. [Example]

[0071] Preferred embodiments of the present invention will be specifically described below based on examples, comparative examples, and test examples, but the present invention should not be construed as being limited thereto.

[0072] <Evaluation of Bond Strength (1) (Shear Test)> The bond strength of the metal-resin bonded body was evaluated by measuring the shear strength in accordance with ISO 19095. Specifically, as shown in Figure 2, a metal-resin bonded body 9, which was made by bonding a metal member 8 and a resin molded body 7, was fixed in a dedicated jig 10, and a load was applied at a rate of 10 mm / min so that a shear force was applied in a direction parallel to the bonding surface, and a test was conducted to destroy the bond between the metal member and the resin molded body. The fracture force at which the metal-resin bonded body broke was calculated as the tensile shear strength (MPa).

[0073] Furthermore, the fracture surface on the metal member side after the shear test was visually observed to confirm the fracture mode. If base material fracture occurred in the resin molded body, it was judged as resin fracture (good). If interface fracture occurred between the metal member and the resin molded body, it was judged as interface fracture (poor). If base material fracture occurred in the metal member, it was judged as metal fracture (poor). If fracture was observed between the metal member and the resin bonded body when the resin molded body was released from the mold after injection molding, the shear strength was rated as 0 MPa.

[0074] <Evaluation of Bond Strength (2) (Shear Test)> The bond strength of the metal-resin-metal bonded bodies was evaluated by measuring shear strength in accordance with JIS K 6850. Specifically, as shown in FIG. 3, a metal-resin-metal bonded body 11, which was formed by bonding two metal members 8 and 8' using a thermosetting adhesive (described below), was fixed to a dedicated jig 10, and a load was applied at a rate of 5 mm / min so that a shear force was applied in a direction parallel to the bonding surfaces, in order to perform a test to break the bond between the metal members via the adhesive. The breaking force at which the metal-resin-metal bonded body broke was calculated as the tensile shear strength (MPa).

[0075] Furthermore, the fracture surface after the shear strength evaluation was visually inspected to confirm the fracture morphology. If cohesive failure occurred in the adhesive and adhesive remained throughout the entire joint, it was judged as "resin failure" (good). If failure occurred at the interface between the metal component and the adhesive, it was judged as "interface failure" (poor).

[0076] <Airtightness evaluation> The airtightness of the metal-resin bonded body or the metal-resin-metal bonded body was evaluated by an air leak test. Specifically, as shown in FIG. 4, a metal-resin bonded body 9, which was obtained by bonding a metal member 8 and a resin molded body 7, was clamped and fixed in a dedicated airtight jig 15. Air was applied at a maximum positive pressure of 0.5 MPa and held for one minute. Thereafter, the presence or absence of air leakage was visually confirmed. Alternatively, as shown in FIG. 5, a metal-resin-metal bonded body 11, which was obtained by bonding two metal members 8 and 8′ using a thermosetting adhesive described below, was clamped and fixed in a dedicated airtight jig 15. Air was applied at a maximum positive pressure of 0.5 MPa and held for one minute. Thereafter, the presence or absence of air leakage was visually confirmed. In the dedicated airtight jig 15 described above, the metal-resin bonded body 9 or the metal-resin-metal bonded body 11 was clamped and fixed from above and below with the O-ring 13 interposed between the fixing jigs. With the metal-resin bonded body 9 or the metal-resin-metal bonded body 11 sandwiched between them, water 12 is present in the open portion above the dedicated airtight jig 15, and air is present in the sealed portion below the dedicated airtight jig 15. By applying air to the sealed portion through the ventilation pipe 14, it is possible to check whether air leaks through the metal-resin bonded body 9 or the metal-resin-metal bonded body 11 to the open portion side, based on whether air bubbles are generated from the bonded interface. If no air leaks were observed within the evaluation time, the result was evaluated as "pass (good)," and if an air leak was observed, the result was evaluated as "fail (bad)."

[0077] <Evaluation of surface roughness of bonding surfaces> The surface roughness of the bonding surface was measured by measuring the maximum height Rz using a Keyence VR-3200 one-shot 3D shape measuring instrument. The measurement was performed in a measurement range of 3600 x 2800 μm, with a magnification of 80x, no cutoff λs, no cutoff λc, and a reference length of 1, and the average value of 41 locations was taken as the measured value. The measurement was performed so that the striped trajectory of the laser light and the striped light irradiated from the measuring instrument's projection lens intersected at right angles.

[0078] Example 1 An aluminum plate material measuring 1.5 mm thick, 18 mm wide, and 45 mm long, and a doughnut-shaped aluminum circular material measuring 2 mm thick, 55 mm outer diameter, and 20 mm inner diameter were cut out from A5052 aluminum alloy (A5052-H34) treated with the tempering code H34 specified in JIS H0001. The former aluminum plate material was used as the metal substrate for the evaluation of bonding strength (1), and the latter doughnut-shaped aluminum circular material was used as the metal substrate for the evaluation of airtightness.

[0079] Table 2 shows the physical properties of this A5052 aluminum alloy material. Among these, "specific gravity," "thermal conductivity," "specific heat," and "boiling point" are literature values, and "thermal diffusion constant" is calculated by "thermal conductivity / (specific gravity × specific heat)." The absorptivity was calculated by subtracting the reflectance (%) of the metal substrate from 100 (%). The reflectance of the metal substrate conformed to JIS K 0115:2020, and the relative reflectance of the wavelength of the laser light used was measured using a UV-visible spectrophotometer. The absorptivity A was the value obtained using the laser light irradiation device A used in Examples 1 to 23 and 25, including this Example 1, and Comparative Examples 1 to 8. The absorptivity B was the value obtained using the laser light irradiation device B used in Example 24, which will be described later.

[0080] [Table 2]

[0081] The two metal substrates prepared above were each irradiated with laser light using a laser light irradiation device A. The laser light irradiation device A was a laser marker MDF-5200 manufactured by Keyence Corporation. The specifications of this device were a pulsed fiber laser, wavelength 1090 nm, maximum output 50 W, and beam diameter 60 μm. The laser conditions for forming the bonding surface in this Example 1 were, as shown in Table 3, 85% output, 90 μm irradiation interval, 340 mm / s scanning speed, 60 kHz frequency, and 1 scan. The peak power was 6.7 kW, the pulse width was 220 ns, and the irradiation time was 6.35 s for the metal substrates used in the bond strength evaluation (shear test) described below, and 5.20 s for the metal substrates used in the airtightness evaluation. In Table 3, when the conditions for laser processing of metal substrates used for evaluation of bonding strength (shear test) and for evaluation of airtightness are distinct, the former is referred to as "shear" and the latter as "airtight." Also, when the conditions are common, they are collectively referred to as "common" (the same applies to Tables 4 and 5 below).

[0082] When actually forming a bonding surface by irradiating a metal substrate with laser light, first, on the metal substrate 1 made of an aluminum plate material for evaluating bonding strength, a bonding surface 1a measuring 10 mm in length (t1) and 18 mm in width (t2) in the short direction was formed at the end in the longitudinal direction on one main surface side, as shown in Figure 6(a). The irradiated area of the bonding surface 1a was 180 mm 2 Specifically, as shown in Figure 6(b), the laser beam with a beam diameter (D) of 60 μm was irradiated at an irradiation interval (L) of 90 μm so as to draw a striped pattern on the joining surface 1a. Then, by scanning the trajectory of the striped pattern on the joining surface 1a once, a metal member for evaluation of joining strength was obtained. The surface roughness of the bonding surface of the metal members used for the bonding strength evaluation was evaluated, and the results are shown in Table 5 below.

[0083] In addition, for the metal substrate 2 made of a doughnut-shaped aluminum circular material for airtightness evaluation, as shown in Figure 7(a), a doughnut-shaped bonding surface 2a with an outer diameter (R2) of 24 mm and an inner diameter (R1) of 20 mm was formed so that the opening 2b at the center had a diameter (R1) of 20 mm and a border of 2 mm in width. The irradiation area of the bonding surface 2a was 138 mm 2 Specifically, as shown in Figure 7(b), a laser beam with a beam diameter (D) of 60 μm was irradiated at an irradiation interval (L) of 90 μm, drawing concentric circles on the joining surface 2a. Then, a metal member for airtightness evaluation was obtained by scanning the joining surface 2a once along a path that drew concentric circles.

[0084] Here, the item "Processing area (mm )" in the setting conditions for laser processing shown in Table 3 2 )" represents the area of the joining surfaces 1a and 2a of the two types of metal substrates 1 and 2 described above. Also, "irradiation energy (J)" in the item of laser output represents the value of "(peak power) x (pulse width) x (set output) x (irradiation time) x (frequency)" included in formula (1). "Unit area irradiation energy (J / m 2 )" represents the laser beam irradiation energy per unit area calculated from formula (1). In addition, in Table 5, the energy E received by the metal substrate calculated from formula (2) represents the calculated values for the metal substrate made of aluminum plate material for evaluating bonding strength (shear test) and the metal substrate made of doughnut-shaped aluminum circular material for evaluating airtightness. In this Example 1, the temperature of the metal substrate before laser irradiation is assumed to be room temperature (25°C) for calculations.

[0085] [Table 3]

[0086] [Table 4]

[0087] [Table 5]

[0088] Each metal member (the laser-treated aluminum plate and aluminum disk) with the bonding surface formed as described above was inserted into a mold fabricated in accordance with ISO 19095 using an injection molding machine (Nissei Plastic Industrial Co., Ltd., FNX1103-18A). Then, the molded body was injection-molded with an aromatic nylon (Mitsubishi Engineering-Plastics Corporation, trade name: Reny®, grade: XL1002U) based on polyamide MXD10 as the thermoplastic resin at a resin temperature of 250°C, a mold temperature of 140°C, an injection speed of 30 mm / s, and a holding pressure of 80 MPa. This produced a bonded body (metal-resin bonded body 9, Figure 8) between aluminum plate (metal member) 8 and resin molded body 7. The resin molded body had a rectangular shape measuring 3 mm thick, 10 mm wide, and 45 mm long, and the area of the rectangular bond between the aluminum plate and resin molded body (bonding area) was 5 mm x 10 mm. The resin molded body is a disk-shaped body with a thickness of 2 mm and a diameter of 24 mm, and the joining width of the annular joint with the inner diameter side of the aluminum disk is 2.0 mm and the joining area is 138.2 mm. 2 A bonded body (metal-resin bonded body 9, FIG. 9) of an aluminum disk (metal member) 8 and a resin molded body 7 was produced.

[0089] The metal-resin bonded bodies obtained above for evaluation of bonding strength were subjected to a test to destroy the bond between the aluminum plate material (metal member) 8 and the resin molded body 7 according to the aforementioned evaluation of bonding strength (1). The fracture force at which the metal-resin bonded body fractured was determined as the tensile shear strength (MPa). The fracture morphology after the tensile shear test was visually observed. The metal-resin bonded bodies for evaluation of airtightness were also checked for air leaks using the aforementioned airtightness evaluation. The results are also shown in Table 3. In Table 3, if at least one of the bonding condition (fracture morphology) and airtightness (air leakage) was poor (×) or failed (×), an overall evaluation was marked "NG." If both were good (◯) or passed (◯), an "OK" was marked.

[0090] [Comparative Examples 1 to 3, Examples 2 to 9] Metal-resin joined bodies for evaluation of bonding strength and airtightness were obtained and subjected to various evaluations in the same manner as in Example 1, except that the laser treatment conditions were changed as shown in Table 3. The results are summarized in Table 5.

[0091] [Examples 10 to 14, Comparative Example 4] Aluminum plates measuring 1.5 mm thick, 18 mm wide, and 45 mm long were cut from hollow extrusions of A6063 aluminum alloy (A6063-T5) processed to the tempering code T5 specified in JIS H0001 in accordance with ISO 19095. Donut-shaped aluminum discs measuring 2 mm thick, 55 mm outer diameter, and 20 mm inner diameter were cut from the extrusions. The former were used as metal substrates for shear strength evaluation (bonding strength evaluation), and the latter were used as metal substrates for airtightness evaluation. Metal-resin joints for bonding strength evaluation and airtightness evaluation were obtained and subjected to various evaluations in the same manner as in Example 1, except that the laser processing conditions were changed as shown in Table 3. The results are summarized in Table 2.

[0092] [Examples 15 to 20, Comparative Examples 5 and 6] An aluminum plate measuring 1.5 mm thick, 18 mm wide, and 45 mm long was cut from a rolled oxygen-free copper (C1020) material specified in JIS H3100. A doughnut-shaped aluminum disc measuring 2 mm thick, 55 mm outer diameter, and 20 mm inner diameter was cut from the rolled oxygen-free copper (C1020). The former was used as a metal substrate for shear strength evaluation (bonding strength evaluation), and the latter was used as a metal substrate for airtightness evaluation. The bonding surfaces were formed by laser processing under the conditions shown in Table 2. The metal-resin bonded bodies were obtained using polyphenylene sulfide (PPS) (manufactured by Polyplastics Co., Ltd., trade name: DURAFIDE, grade: 1150MF1) as the thermoplastic resin. The injection molding conditions were a resin temperature of 320°C, a mold temperature of 150°C, an injection speed of 30 mm / s, and a holding pressure of 80 MPa. Metal-resin bonded bodies for bonding strength evaluation and airtightness evaluation were obtained and subjected to various evaluations in the same manner as in Example 1. The results are summarized in Table 4.

[0093] [Examples 21 to 23, Comparative Examples 7 to 8] An aluminum plate measuring 1.5 mm thick, 18 mm wide, and 45 mm long was cut from stainless steel (SUS304) plate material, and a doughnut-shaped aluminum disc measuring 2 mm thick, 55 mm outer diameter, and 20 mm inner diameter was cut from the stainless steel (SUS304). The former was used as the metal substrate for shear strength evaluation (bonding strength evaluation), and the latter was used as the metal substrate for airtightness evaluation. The bonding surfaces were formed by laser processing under the conditions shown in Table 4. The metal-resin bonded bodies were obtained using polyphenylene sulfide (PPS) (manufactured by Polyplastics Co., Ltd., trade name: DURAFIDE, grade: 1150MF1) as the thermoplastic resin. The injection molding conditions were a resin temperature of 320°C, a mold temperature of 150°C, an injection speed of 30 mm / s, and a holding pressure of 80 MPa. Metal-resin bonded bodies for bonding strength evaluation and airtightness evaluation were obtained and subjected to various evaluations in the same manner as in Example 1. The results are summarized in Table 4.

[0094] Example 24 Metal-resin bonded bodies for evaluation of bonding strength and airtightness were obtained in the same manner as in Example 1, except that the laser beam irradiation device was replaced with laser beam irradiation device B and the laser treatment conditions were changed as shown in Table 3. Various evaluations were then performed. The results are shown in Table 2. Laser beam irradiation device B was a Keyence MDV-9600A. The specifications of this device were a Q-switched YVO4 laser with a wavelength of 1064 nm, a maximum output of 8 W, and a beam diameter of 40 μm. The laser conditions for forming the bonding surface in Example 24 were as shown in Table 4: 95% output, 100 μm irradiation interval, 30 mm / s scanning speed, 20 kHz frequency, and 1 scan. The peak power was 32 kW, the pulse width was 10.1 ns, and the irradiation time was 35.00 s for the metal substrates used in the evaluation of bonding strength (shear test) and 51.04 s for the metal substrates used in the evaluation of airtightness.

[0095] Example 25 Two rectangular aluminum plates measuring 5 mm thick x 25 mm wide x 50 mm long were cut out from hollow extrusions of A6063 aluminum alloy (A6063-T5) treated to the tempering code T5 specified in JIS H0001, a circular aluminum disk measuring 2 mm thick x 55 mm outer diameter x 20 mm inner diameter, and a circular aluminum disk measuring 2 mm thick x 24 mm outer diameter were cut out and used as metal substrates.

[0096] Next, laser irradiation was performed in the same manner as in Example 1, except that the laser treatment conditions were changed as shown in Table 4, to form a joining surface. For each of the two aluminum plates, the laser was irradiated to a rectangular area measuring 6 mm in the longitudinal direction and 25 mm in the lateral direction at the end of the longitudinal direction on one of the main surfaces. The irradiated area of the joining surface was 180 mm 2 In the case of the annular aluminum disk, the laser was irradiated from the inside to a ring-shaped area with a width of 2.0 mm. In the case of the circular aluminum disk, the laser was irradiated from the inside to a ring-shaped area with a width of 2.0 mm. The irradiated area of the joining surface was 138 mm. 2 It was.

[0097] A thermosetting adhesive (one-component heat-curing epoxy adhesive) (product name: Scotch-Weld® SW2214, manufactured by 3M Japan Ltd.) was applied to the joining surfaces of each metal component (the laser-treated aluminum plate and aluminum disk). The adhesive was applied to the joining surfaces to a thickness of 0.2 mm, adjusted with a stainless steel wire. After applying the adhesive, the two aluminum plates were bonded together, and a pressure of 0.01 MPa was applied. After the specimen temperature reached 150°C, the test pieces were heated for 30 minutes. This resulted in a joined aluminum plate (metal component) 8 and 8' (a joint of an aluminum plate, a resin molded body, and an aluminum plate) (metal-resin-metal joined product 11, Figure 10) with a rectangular joint area of 6 mm × 25 mm. In addition, after applying the adhesive, a circular aluminum disk and a circular aluminum disk were bonded together, and under the same bonding conditions, the bonding width of the circular joint between the circular aluminum disk and the circular aluminum disk was 2.0 mm and the bonding area was 138.2 mm. 2A bonded body (metal-resin-metal bonded body 11, FIG. 11) was fabricated by bonding an annular aluminum disk (metal member) 8 and a circular aluminum disk (metal member) 8' via an adhesive (a bonded body of an annular aluminum disk, a resin molded body, and a circular aluminum disk). The obtained metal-resin bonded body was subjected to the aforementioned evaluation of bonding strength (2) and airtightness. The evaluation results are summarized in Table 3.

[0098] [Consider] Of the above experiments, the metal-resin bonded bodies obtained in Comparative Example 1, Example 1, and Comparative Example 2 were cut in the thickness direction, and the cross sections were observed at a magnification of 500 times using a scanning electron microscope (JEOL Ltd., JSM-7200F), as shown in Figures 12, 13, and 14. These images show that a bonding surface having irregularities was formed on the surface of the metal base material in all cases. Of these, Figure 12 shows a cross section of a metal-resin bonded body for airtightness evaluation in Comparative Example 1. Comparative Example 1 failed the airtightness evaluation (×), and SEM observations revealed that the recesses in the surface irregularities formed on the joining surfaces of the metal members (metal substrates) were long and deep. This suggests that the resin was unable to reach the depths of the recesses, reducing the airtightness. It also shows that the tops of some of the protrusions in the surface irregularities formed on the joining surfaces of the metal members were in contact with each other. This suggests that the tops of the protrusions came into contact, forming closed holes (spaces) below them that the resin molded body could not penetrate, resulting in reduced airtightness.

[0099] FIG. 14 shows a cross section of a metal-resin bonded body for evaluation of bonding strength in Comparative Example 2. The bonding condition in Comparative Example 2 was unacceptable (×), and SEM observation revealed that the depressions (valleys or holes) in the surface irregularities formed on the bonding surfaces of the metal members were relatively small. This suggests that the resin molded body did not sufficiently penetrate into the bonding surfaces of the metal members, resulting in insufficient anchoring effect (mechanical bonding / anchoring effect). Furthermore, SEM observation of the cross section in Comparative Example 2 confirmed the presence of areas that had not been irradiated with the laser. It is believed that the airtightness and bonding strength in Comparative Example 2 were reduced due to the influence of the areas that had not been irradiated with the laser.

[0100] In contrast, Fig. 13 shows a cross section of a metal-resin joined body for evaluating the joining strength in Example 1. Example 1 shows good results in both airtightness and joining condition. In fact, SEM observation shows that the surface irregularities formed on the joining surfaces of the metal members have sufficient openings on the top side, recesses of appropriate depth, and uniformly shaped protrusions.

[0101] FIG. 15 is a graph showing the relationship between the "energy E received by the metal substrate" (energy E calculated by Equation (2) or "calculated value" in Table 3) and the surface roughness Rz of the joining surface of the metal-resin joined bodies for evaluation of joining strength obtained in Examples 1 to 25 and Comparative Examples 1 to 8. The graph in FIG. 15 also shows the fracture morphology and airtightness evaluation results. A good joint is indicated when both the fracture morphology and airtightness are good (○), and a poor joint is indicated when either the fracture morphology or airtightness is poor (×). In FIG. 15, good joints are plotted with black circles, and unsuccessful joints are plotted with black triangles. This shows that if the "energy E received by the metal substrate" is in the range of 0.18≦E≦0.75, the fracture morphology after the tensile shear test is good, and the airtightness (air leakage) is also acceptable within this range.

[0102] As described above, according to the present invention, a metal-resin bonded body having excellent bonding strength and airtightness can be obtained. In particular, the present invention makes it possible to control the energy received by the metal substrate while taking into consideration the irradiation energy of the laser beam, so that a metal-resin bonded body having excellent bonding strength and airtightness can be produced with good reproducibility. Moreover, since the present invention can be applied even when the conditions of the laser beam or the type of metal substrate are changed, it can be said that the method has excellent practicality. [Explanation of symbols]

[0103] 1, 2...metal substrate, 1a, 2a...joint surface, 2b...opening, 3...scanning direction, 4...beam diameter, 5...irradiation interval, 6(6')...laser light trajectory, 7...resin molded body, 8...metal member, 9...metal-resin bonded body, 10...dedicated jig for shear test, 11...metal-resin-metal bonded body, 12...water, 13...O-ring, 14...air blowing tube, 15...dedicated airtight jig

Claims

1. A method for manufacturing a metal member having a surface to be joined with an object to be joined, a laser irradiation step of irradiating a surface of a metal substrate made of metal with laser light to form the joining surface having an uneven portion on the metal substrate; In the laser irradiation step, based on the irradiation energy per unit area calculated by the following formula (1), the energy E received by the metal substrate by irradiation with laser light calculated by the following formula (2) or (3) is calculated, and laser conditions are set so that the energy E received by the metal substrate satisfies 0.18≦E≦0.75, and the laser treatment is performed under the set laser conditions. A method for manufacturing a metal member comprising the steps of: Irradiation energy per unit area = (peak power) × (pulse width) × (set output) × (irradiation time) × (frequency) / (irradiation area) ... formula (1) Energy received by the metal substrate E = (irradiation energy per unit area) x (substrate absorption rate) ２ ×√(thermal diffusion constant) / (difference in temperature rise from the temperature of the metal substrate before laser irradiation to the boiling point of the metal substrate after laser irradiation) ...Equation (2) Energy E received by the metal substrate = (irradiation energy per unit area) × (substrate absorptivity) × (vapor absorptivity) × √ (thermal diffusion constant) / (difference in temperature rise from the temperature of the metal substrate before laser irradiation to the boiling point of the metal substrate after laser irradiation) ... Equation (3)

2. 2. The method for manufacturing a metal member according to claim 1, wherein the metal substrate is aluminum, copper, iron, or an alloy containing any of these metals.

3. 3. The method for manufacturing a metal member according to claim 1, wherein the surface roughness (Rz) of the joining surface is 30 μm or more and 180 μm or less.

4. a resin molding step of forming a resin molded body on the surface of the metal member obtained by the manufacturing method according to claim 1, A metal-resin joined body is manufactured by joining the joining surface of the metal member and the resin molded body.

1. A method for producing a metal-resin bonded body, comprising:

5. 5. The method for producing a metal resin bonded body according to claim 4, wherein in the resin molding step, a resin molded body containing a thermoplastic resin or a thermosetting resin is molded on the metal member.

Images