JP2019005932A - Method of manufacturing composite member of aluminum diecast member and silicone member - Google Patents

Abstract

To provide a method of manufacturing a composite member in which an aluminum diecast member and a silicone member are firmly bonded, and capable of removing easily and in a short time a carbide film on a surface of the aluminum diecast member.SOLUTION: The method of manufacturing the composite member in which the aluminum diecast member and the silicone member are combined includes a removing step of removing the carbide film existing on a surface of the aluminum diecast member to be bonded with the silicone member by applying plasma to the surface to be bonded, a modifying step of imparting a hydroxyl group to the surface to be bonded by applying plasma to the surface to be bonded from which the carbide film has been removed, and a combining step of forming integrally the silicone material and the surface to be bonded to which the hydroxyl group has been imparted.SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a composite member in which an aluminum die cast member and a silicone member are combined.

  For a case of an electronic control device such as an engine control unit mounted on an automobile, a composite member is used in which a silicone member is bonded to a casing that is an aluminum die-cast member. As an aluminum alloy for die casting (die casting), ADC12 of Al-Si-Cu alloy is known. However, an aluminum die-cast member obtained by die-casting an aluminum alloy such as ADC12 and a silicone member have a problem of poor adhesion.

  Various factors, such as organic dirt, can be considered as the factors that hinder the adhesion. Among them, the presence of a carbide film formed on the surface of the aluminum die cast member becomes a problem. The carbide film is considered to consist of a residue of a release agent (a mixture of oil, silicon, wax, etc.) applied to the mold when manufacturing an aluminum die cast member. The release agent is graphitized by heating at the time of die casting, so that it remains as a hard carbide film on the surface of the aluminum die casting member. Even if the carbide film was adhered to the surface of the aluminum die cast member, the silicone member was peeled off at the interface, and the two could not be sufficiently bonded.

JP 2014-86682 A JP 2009-155358 A JP 2006-257355 A

  It is difficult to remove the carbide film formed on the surface of the aluminum die-cast member by cleaning with an organic solvent or ultrasonic cleaning. For this reason, it is necessary to perform wet treatment such as acid or alkali cleaning, blast treatment, or the like. However, in the case of wet processing, it is difficult to manage the process because it is necessary to adjust the chemical concentration and to suppress the reattachment of dirt. In addition, even if the carbide film can be removed by wet treatment or blast treatment, the surface is not activated such as increasing functional groups, and the surface is easily recontaminated with organic substances. It does not lead to an increase in adhesion.

  On the other hand, as a method for improving adhesion without removing a carbide film, Patent Document 1 discloses that a silicon-based thin film or a carbon-based thin film is formed on the surface of an aluminum die cast member by a plasma CVD method, A method for adhering an aluminum die-cast member and a seal member made of a silicone adhesive is described. Patent Document 2 describes a method in which a cured product (silicone rubber) of a moisture curable silicone rubber composition and a substrate are bonded via a silicon oxide film formed by burning an organosilicon compound. In the method described in Patent Document 2, a process of spraying a flame of a fuel gas containing an organosilicon compound on the substrate surface is performed. For this reason, the damage to a base material is large. In Patent Document 2, an aluminum die-cast member is not described as a base material, but in paragraph [0033], a metal housing such as aluminum die-casting is used as a member to be bonded to silicone rubber on the side opposite to the base material. Is described. In the following paragraph [0034], it is described that an oxide film or the like may be formed in advance on the surface of the metal casing in order to improve the adhesion. As described above, Patent Documents 1 and 2 merely describe a method of forming a new thin film instead of removing the carbide film.

  Moreover, it is difficult to make the adhesion degree and composition of the carbide film uniform every time it is manufactured. For example, in one aluminum die-cast member, there may be a mixture of a portion where a large amount of carbide film is attached or a portion where no carbide film is attached. In such a case, when a thin film is newly formed on the carbide film, the adhesiveness in the vicinity of the boundary between the part to which the carbide film is attached and the part to which the carbide film is not attached tends to become unstable. Further, when the carbide film itself is fragile, it causes a decrease in adhesive force due to the fragile carbide film.

  Patent Document 3 describes a cured product of a curable polyorganosiloxane composition for sealing that has excellent adhesion to an aluminum die-cast member. According to Patent Document 3, if the polyorganosiloxane composition is used, good adhesiveness can be obtained without cleaning the aluminum die-cast member, that is, even when the mold release agent remains in the aluminum die-cast member. It is stated. However, it is desirable that the adhesiveness can be improved without using a special polyorganosiloxane composition as described in Patent Document 3.

  The present invention has been made in view of such a situation, and the carbide film on the surface of the aluminum die-cast member can be easily and quickly removed, and the aluminum die-cast member and the silicone member are firmly bonded. It aims at providing the manufacturing method of a composite member.

  In order to solve the above-mentioned problems, a method for producing a composite member of the present invention is a method for producing a composite member in which an aluminum die-cast member and a silicone member are combined, and a joining surface of the aluminum die-cast member with the silicone member The step of removing the carbide film existing on the bonding surface by irradiating plasma on the bonding surface, and the modification of irradiating the bonding surface from which the carbide film has been removed with plasma to impart a hydroxyl group to the bonding surface And a composite step of integrally forming a silicone material on the joint surface to which a hydroxyl group has been imparted.

  According to the method for manufacturing a composite member of the present invention, first, in the removing step, the joining surface of the aluminum die cast member is irradiated with plasma. By the action of ions, radicals, etc. in the plasma on the surface of the substrate, the carbide film formed on the bonding surface can be easily and quickly removed. Next, in the modification step, the bonding surface is further irradiated with plasma. When the carbide film on the bonding surface is removed, an oxide layer (natural oxide layer) that is naturally generated under the carbide film is exposed. When plasma is irradiated there, a chemical bond of molecules on the surface of the oxide layer is broken by ions, radicals, etc. in the plasma, and the surface is activated to generate hydroxyl groups. In this way, by activating the surface of the joint surface in the reforming process, many hydroxyl groups are generated on the joint surface, so that the hydroxyl group and the silicone material react and chemically bond, thereby providing strong adhesion. Can be realized. In addition, since a large number of hydroxyl groups are generated on the bonding surface by a dry process called plasma irradiation, the hydroxyl groups are difficult to decrease over time, and the state of high reactivity with the silicone material can be maintained for a relatively long time. . Therefore, after the reforming step, it is not necessary to continuously perform the integral molding in the next compounding step (it goes without saying that it may be performed continuously), and the aluminum die-cast member and the silicone member are firmly bonded. Can be realized. As described above, according to the manufacturing method of the present invention, it is possible to manufacture a composite member that is difficult to peel at the interface of the silicone member and has high durability.

It is a top view of the test piece manufactured in the Example.

  The method for manufacturing a composite member of the present invention is a method for manufacturing a composite member in which an aluminum die-cast member and a silicone member are combined, and includes a removing step, a modifying step, and a combining step.

  The aluminum die-cast member is a member manufactured by die-casting an aluminum alloy, and the shape, size, etc. are not particularly limited. Aluminum alloys for die casting are defined in JIS H 5302: 2006, and include Al—Si—Cu based alloys ADC12 and ADC10.

  The shape of the silicone member is not particularly limited. In the present specification, “silicone” is a concept including both silicone resin and silicone rubber. The silicone member is a cured product of a composition containing an organopolysiloxane, a crosslinking agent, and an adhesive component. If necessary, the composition contains a crosslinking accelerator, crosslinking retarder, crosslinking aid, scorch inhibitor, anti-aging agent, softener, heat stabilizer, flame retardant, flame retardant, ultraviolet absorber, A rusting agent, a conductive agent, an antistatic agent, and the like may be included.

  Organopolysiloxane has at least two functional groups capable of crosslinking in one molecule, and contains alkenyl group (vinyl group, allyl group, etc.)-Containing organopolysiloxane, hydroxyl group-containing organopolysiloxane, (meth) acryl group-containing Examples include organopolysiloxane, isocyanate-containing organopolysiloxane, amino group-containing organopolysiloxane, and epoxy group-containing organopolysiloxane.

  Examples of the crosslinking agent include a hydrosilyl crosslinking agent, a sulfur crosslinking agent, and a peroxide crosslinking agent. Examples of the hydrosilyl crosslinking agent include hydrosilyl group-containing organopolysiloxane (organohydrogenpolysiloxane).

  As the adhesive component, a compound having a functional group capable of binding to a hydroxyl group imparted to the joint surface of the aluminum die cast member after the modification step is desirable. Examples of the functional group include an alkoxysilyl group, a hydrosilyl group, and a silanol group. For example, a silane coupling agent may be used as the compound having an alkoxysilyl group. The silane coupling agent is a silane compound having two or more different functional groups in the molecule. Examples of the functional group other than the alkoxysilyl group in the silane coupling agent include a vinyl group, an epoxy group, a styryl group, and a (meth) acryl group. Specific examples of the silane coupling agent include p-styryltrimethoxysilane, phenyltri (dimethylsiloxy) silane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyl Examples include trihydroxysilane.

  Hereinafter, each process of the manufacturing method of the composite member of this invention is demonstrated.

[Removal process]
This step is a step of removing the carbide film existing on the bonding surface by irradiating plasma on the bonding surface of the aluminum die-cast member with the silicone member.

  The method for generating plasma is not particularly limited. For example, RF plasma using a high frequency (RF) power source, microwave plasma using a microwave power source, direct current (DC) pulse plasma, or the like may be employed, and the power source may be modulated. Of these, microwave plasma is preferable because of its high plasma density and high processing speed, and low plasma damage on the irradiation target. When microwave plasma is employed in this step, the carbide film can be removed in a short time and the efficiency is high. The frequency of the plasma generation power source is not particularly limited. Examples of the microwave frequency include 8.35 GHz, 2.45 GHz, 1.98 GHz, and 915 MHz. Examples of the RF frequency include 13.56 MHz. Examples of the DC frequency include 1 to 500 kHz.

In the plasma, ions, electrons, and radicals are mixed by ionizing the gas. For example, when plasma is generated in a gas atmosphere containing oxygen, oxygen radicals are generated. This reacts with the carbon of the carbide film, by becoming the like bonded to CO _2, CO (radical etching), it is possible to remove the carbide film. In the case of ion etching, the ions hit the irradiation target, thereby breaking the chemical bonds of the surface molecules. For this reason, it is desirable to control the directionality of ions so that the ions are directed toward the irradiation target. On the other hand, radical etching does not need to control directionality and has a very high reaction rate. Therefore, when plasma is generated in a gas atmosphere containing oxygen, the carbide film can be removed in a short time by the etching action of oxygen radicals.

  The gas atmosphere containing oxygen may be air, or may be composed of only oxygen gas or a mixed gas of oxygen gas and rare gas or nitrogen gas. Argon, xenon, etc. are suitable as the rare gas. For example, when the gas atmosphere containing oxygen is composed of a mixed gas of one or more gases selected from rare gas and nitrogen gas and oxygen gas, from the viewpoint of effectively using the etching action of oxygen radicals, The content ratio of the oxygen gas is desirably 30% or more when the pressure or volume of the entire mixed gas is 100%. When the gas atmosphere containing oxygen is composed only of oxygen gas, radical etching can be utilized to the maximum and is effective.

  The plasma irradiation may be performed under atmospheric pressure or under a vacuum reduced to a predetermined pressure (either atmospheric pressure plasma processing or vacuum plasma processing). In particular, when performed under vacuum, it is possible to easily prevent damage to incidental equipment due to ozone generated in the plasma and to increase the mixing ratio of oxygen gas. it can. Further, the plasma density is increased, the processing speed can be increased, and the plasma irradiation range can be easily increased, so that the productivity is high. In the case of vacuum plasma treatment, the pressure in the container for generating plasma is preferably about 1 to 100 Pa.

[Modification process]
This step is a step of irradiating the bonding surface from which the carbide film has been removed with plasma to impart a hydroxyl group to the bonding surface. When the carbide film on the bonding surface is removed by the previous removing step, an oxide layer that is naturally generated under the carbide film is exposed. In this step, the bonding surface where the oxide layer is exposed is irradiated with plasma to activate the surface, thereby generating hydroxyl groups on the bonding surface.

  The plasma generation method, suitable gas atmosphere in the container, pressure, etc. are as described in the previous removal step. When microwave plasma under vacuum is employed in this step, since the plasma density is large, the degree of activation of the bonding surface is increased, and more hydroxyl groups can be generated. Thereby, a state with high reactivity with a silicone material can be maintained for a longer time on the joint surface.

  The plasma irradiation in this step is also preferably performed in a gas atmosphere containing oxygen. When performed in a gas atmosphere containing oxygen, the bonding surface can be activated in a relatively short time by surface adsorption of oxygen radicals and oxidation reforming action. For example, when the gas atmosphere containing oxygen is composed of a mixed gas of at least one kind of gas selected from rare gas and nitrogen gas and oxygen gas, the surface adsorption of oxygen radicals and oxidation reforming action are effectively used. In view of the above, it is desirable that the content ratio of the oxygen gas is 30% or more when the pressure or volume of the entire mixed gas is 100%. When the gas atmosphere containing oxygen is composed only of oxygen gas, it is effective because the action of radicals can be utilized to the maximum extent.

  The plasma irradiation in this step may be performed in the same manner as in the previous removal step, or may be performed by changing the gas atmosphere or pressure. When performing the plasma irradiation in the removal step and this step under vacuum, if both steps are performed continuously in the same container and in the same gas atmosphere, the work required for the series of steps is reduced and the processing time is reduced. Can be shortened. In addition, when performing the plasma irradiation in the removal process and the main process under atmospheric pressure, if both processes are performed continuously in the same gas atmosphere, the work required for the series of processes is reduced and the processing time is shortened. be able to.

  The state (degree of activation) of the joint surface after finishing this process can be estimated by the magnitude of the water contact angle of the joint surface. For example, when the water contact angle of the joint surface is 50 ° or less, sufficient hydroxyl groups are formed on the joint surface, and it can be considered that the reactivity with the silicone material is high. In this specification, the value measured according to JIS R3257: 1999 is employ | adopted as a water contact angle.

  There is almost no carbide film that is considered to be a residue such as a release agent on the bonding surface after the removal step and the main step. On the other hand, although a small amount of organic matter floating in the atmosphere adheres after this step, the amount of carbon contained at a depth of about 2 to 5 nm from the bonding surface is compared with that of an untreated one in which a carbide film exists. Less. For example, when the bonding surface after this step is analyzed by X-ray photoelectron spectroscopy (XPS), the number of C atoms is 5% or more when the total number of Al, O, and C atoms is 100%. It is desirable that it is 30% or less.

[Composite process]
This step is a step of integrally molding a silicone material on the joint surface of the aluminum die cast member to which a hydroxyl group has been imparted.

  The silicone material is a composition containing the above-described organopolysiloxane, a crosslinking agent, and an adhesive component. This step may be performed by insert molding, for example. That is, the aluminum die-cast member that has undergone the removal process and the reforming process is placed in a mold, and a liquid silicone material is injected into the mold so as to be in contact with the joining surface of the aluminum die-cast member, under a predetermined temperature and pressure. The silicone material may be cured. Or you may apply | coat a liquid silicone material to the joint surface of the aluminum die-casting member which finished the removal process and the modification process, and may harden a silicone material under predetermined temperature and pressure. The silicone material is cured to form a silicone member, and a composite member in which the aluminum die cast member and the silicone member are firmly bonded can be obtained.

  This step may be performed continuously after the previous reforming step, or may be performed after a time such as several hours or several days has elapsed after the reforming step. As described above, according to the modification step of the present invention, since the bonding surface is sufficiently activated, the generated hydroxyl group is less likely to decrease over time, and the state of high reactivity with the silicone material is relatively high. Can be maintained for a long time. Therefore, even if this process is not performed continuously, the hydroxyl group on the bonding surface and the silicone material can be reacted to achieve strong adhesion. From the viewpoint of ensuring high adhesiveness, this step is preferably performed within one week after the modification step.

  The adhesiveness between the aluminum die-cast member and the silicone member in the obtained composite member may be evaluated by performing a 90 ° peel test specified in JIS K 6256-2: 2013. For example, if the peel strength in the peel test is 4 N / mm or more, it is not interfacial peel but cohesive failure of the silicone member, and it can be determined that the adhesion is good.

  Next, the present invention will be described more specifically with reference to examples.

<Manufacture of test pieces>
[Example 1]
(1) A silicone material was prepared as follows. 1 part by mass of p-styryltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) as an adhesive component was added to 100 parts by mass of a liquid silicone rubber (vinyl group-containing dimethylpolysiloxane: made by Gelest, “DMS-V35”). Mix for 30 minutes with a planetary mixer. To this mixture, 4 parts by mass of a hydrosilyl cross-linking agent (hydrosilyl group-containing dimethylpolysiloxane: “HMS-151” manufactured by Gelest Co., Ltd.) was added and mixed for another 30 minutes, followed by degassing under reduced pressure to prepare a liquid silicone material. did.

  (2) A rectangular plate-shaped member (aluminum die-cast member) manufactured by die-casting the ADC12 of an Al—Si—Cu-based alloy was prepared. The plate-like member has a long side of 60 mm, a short side of 45 mm, and a thickness of 1.5 mm. The entire surface of the plate member was subjected to microwave plasma treatment as follows. First, the plate-like member was placed in a vacuum vessel, and the inside of the vacuum vessel was brought to a reduced pressure state of 0.5 Pa or less. Next, oxygen gas was supplied into the vacuum vessel to form an oxygen gas atmosphere having a pressure of 10 Pa. In this state, microwave plasma was generated at a frequency of 2.45 GHz and an output power of 2 kW, and the entire surface of the plate member was irradiated for 10 seconds. Thus, while removing the carbide | carbonized_material film which existed on the one surface of the plate-shaped member, the said surface was activated, and the hydroxyl group was produced | generated on the surface. In Example 1, plasma irradiation in the removal step and the modification step was continuously performed in the same container and in the same gas atmosphere.

  As will be described later, the water contact angle of one surface subjected to microwave plasma treatment was measured immediately after the reforming step and every time a predetermined time passed. Immediately after the reforming step, the same XPS analysis was also performed. And the plate-shaped member which completed the measurement was used for the compounding step. In the compounding step, the plate-like member was placed in a mold, and the prepared silicone material was injection molded at a temperature of 140 ° C. and an injection pressure of 0.3 MPa. Thus, the test piece by which the silicone member was vulcanized-bonded to a part of one surface of the plate-shaped member was manufactured. A part of one surface of the plate-like member to which the silicone member is bonded is included in the concept of the bonding surface in the present invention. The manufactured test piece is included in the concept of the composite member in the present invention. In FIG. 1, the top view of the manufactured test piece is shown.

  As shown in FIG. 1, the test piece 1 includes a plate-like member 10 and a silicone member 11. The silicone member 11 has a strip shape. The silicone member 11 has a long side of 90 mm, a short side of 25 mm, and a thickness of 6 mm. The left end portion of the silicone member 11 is overlapped and adhered to a part (25 mm × 25 mm region, indicated by dotted line hatching in FIG. 1) of one surface (upper surface) 100 of the plate-like member 10.

[Example 2]
A test piece was manufactured in the same manner as in Example 1 except that the entire surface of the same plate-like member as in Example 1 was subjected to RF plasma treatment instead of microwave plasma treatment. The RF plasma treatment was performed as follows. First, the plate-like member was placed in a vacuum vessel, and the inside of the vacuum vessel was brought to a reduced pressure state of 0.5 Pa or less. Next, oxygen gas was supplied into the vacuum vessel to form an oxygen gas atmosphere having a pressure of 100 Pa. In this state, RF plasma was generated at a frequency of 13.56 MHz and an output power of 1 kW, and the entire surface of the plate member was irradiated for 60 seconds. Also in Example 2, plasma irradiation in the removal step and the modification step was continuously performed in the same container and in the same gas atmosphere.

[Example 3]
A test piece was produced in the same manner as in Example 1 except that the entire surface of the same plate-like member as in Example 1 was subjected to atmospheric pressure DC pulse plasma treatment instead of vacuum microwave plasma treatment. The atmospheric pressure plasma treatment was equipped with an atmospheric pressure plasma treatment unit “Tough Plasma FPE20 Type II” manufactured by Fuji Machine Manufacturing Co., Ltd., and a stage for holding the substrate disposed at a position facing the treatment unit. An atmospheric pressure plasma apparatus was used. The atmospheric pressure plasma treatment was performed as follows. A plate-like member is installed on a stage under atmospheric pressure (about 1.013 × 10 ⁵ Pa), and a gas in which nitrogen and air are mixed at a volume ratio of 100: 0.6 is supplied to the processing unit at a flow rate of 30 L / min. Atmospheric pressure plasma was generated by introducing a predetermined electric power. The generated atmospheric pressure plasma is irradiated from the processing head toward the plate-like member through a plasma injection port provided in the processing unit. The distance between the plasma injection port and the plate member was 5 mm, and the entire surface of the plate member was irradiated with the stage moving at a speed of 10 mm / second in the short side direction of the plate member. In Example 3, plasma irradiation in the removal step and the modification step was continuously performed in the same gas atmosphere.

[Comparative Example 1]
A test piece was manufactured in the same manner as in Example 1 except that the entire surface of the same plate-like member as in Example 1 was not subjected to plasma treatment. That is, a silicone material was injection-molded on a plate-like member that was die-cast.

[Comparative Example 2]
A test piece was produced in the same manner as in Example 1 except that the entire surface of the same plate-like member as in Example 1 was subjected to blasting instead of plasma treatment. The blasting process was performed as follows. First, glass beads (FGB-320) manufactured by Fuji Seisakusho Co., Ltd. were used as a projecting material, and projected onto a plate-like member at a pressure of about 0.3 MPa for 1 minute. Next, pure water cleaning was performed for 30 seconds, ethanol cleaning was performed for 10 seconds, and dried by air blow.

  For the test piece of Comparative Example 2, as described later, the water contact angle of one surface subjected to the blast treatment was measured immediately after the blast treatment and every time a predetermined time passed. Immediately after the blast treatment, the same surface XPS analysis was also performed. And the silicone material was injection-molded to the plate-shaped member which completed the measurement.

<Measurement of water contact angle>
About the test piece of Examples 1-3, the water contact angle of the one surface after plasma processing (after a modification process and before a composite process) was measured. For the test piece of Comparative Example 1, the water contact angle on one surface of the untreated state was measured. For the test piece of Comparative Example 2, the water contact angle on one side after blasting was measured. The water contact angle was measured four times immediately after treatment, 1 hour later, 1 day later, and 7 days later, except for the test piece of Comparative Example 1. The water contact angle was measured according to JIS R3257: 1999. That is, 2 μl of water was dropped onto one surface of the plate-like member, and the water contact angle within 1 minute after the water contacted the one surface was measured.

<Analysis by X-ray photoelectron spectroscopy (XPS)>
For the test pieces of Examples 1 and 3, XPS analysis was performed on one surface immediately after the plasma treatment (immediately after the reforming step), and the ratio of C atoms, O atoms, and Al atoms present on the surface was examined. The ratio of C atoms, O atoms, and Al atoms present on the surface was analyzed by XPS analysis for one side of the untreated state for the test piece of Comparative Example 1 and one side immediately after the blast treatment for the test piece of Comparative Example 2. I investigated.

<Evaluation of adhesiveness>
About each test piece of Examples 1-3 and Comparative Examples 1 and 2, the 90 degree peeling test prescribed | regulated to JISK6256-2: 2013 was done, and the adhesiveness of the silicone member with respect to a plate-shaped member was evaluated. As a result of the 90 ° peel test, the adhesive strength is good when the peel strength is 4 N / mm or more (indicated by a circle in Tables 1 and 2 below), and the peel strength is less than 4 N / mm Or the case of interfacial peeling was defined as poor adhesion (indicated by x in Tables 1 and 2).

<Evaluation results>
Table 1 shows the evaluation results of the water contact angle and adhesiveness of each test piece. Table 2 shows the results of XPS analysis for each test piece. Table 2 also shows the evaluation results of adhesiveness when the silicone material is integrally formed immediately after the treatment.

  As shown in Table 1, in the test pieces of Examples 1 to 3 in which the joint surface of the aluminum die cast member with the silicone member was plasma-treated, the water contact angle immediately after the treatment was as small as less than 10 °, and the adhesiveness was also good. there were. It shows that hydrophilicity is so high that a water contact angle is small, and it is guessed that there is much quantity of the hydroxyl group in the surface. Among the test pieces of Examples 1 to 3 having high hydrophilicity, those in which the silicone material was integrally formed immediately after the plasma treatment were subjected to cohesive failure without causing interfacial peeling in the 90 ° peel test. On the other hand, in the untreated test piece of Comparative Example 1, the water contact angle was as large as 80 °, and the adhesiveness was poor. When the test piece of Comparative Example 1 was subjected to a 90 ° peel test, the silicone member was peeled off at the interface. Moreover, in the test piece of Comparative Example 2 subjected to the blast treatment, the water contact angle immediately after the treatment was as small as 20 °, but the adhesiveness was poor. In the case of the test piece of Comparative Example 2, even when the silicone material was integrally formed immediately after the blast treatment, the silicone member was interfacially peeled in the 90 ° peel test. This is because the water contact angle is reduced because the surface is roughened by the projection of the glass beads, but the surface is likely to be contaminated by organic substances adhering to the glass beads themselves or trace amounts of organic substances contained in the cleaning liquid. Even if a hydroxyl group is generated immediately after the glass beads are projected, the amount thereof is small and is considered to disappear immediately. This is also clear from the fact that the water contact angle increases to 80 ° after 1 hour from the blast treatment.

  As shown in Table 2, according to XPS analysis of one surface (joint surface) immediately after the treatment, in the test pieces of Examples 1 and 3 subjected to plasma treatment, the proportion of C atoms was 30% or less. In the untreated specimen of Comparative Example 1 and the blasted specimen of Comparative Example 2, the proportion of C atoms exceeded 50%. From this result, it can be understood that the carbide film existing on the bonding surface was removed by performing the plasma treatment. In the test piece of Comparative Example 2, it is considered that the carbide film is removed by the blasting process, but the proportion of C atoms was as large as 59%. This is presumably because organic substances adhered during and after the treatment.

  From the above, when plasma is applied to the bonding surface of the aluminum die-cast member, the carbide film is removed and the surface is activated, so that a large number of hydroxyl groups can be generated on the bonding surface, thereby improving the adhesion. confirmed.

  On the other hand, returning to Table 1, there was a difference in the change with time of the water contact angle depending on the type of plasma treatment. In the test piece of Example 1 subjected to microwave plasma treatment under vacuum, the water contact angle was 50 ° or less even after 7 days from the treatment, and good adhesiveness was maintained. On the other hand, for the test pieces of Examples 2 and 3 subjected to the RF plasma treatment and the atmospheric pressure plasma treatment, the water contact angle becomes 50 ° after 1 hour from the treatment, and after one day has passed. It became 80 °. In connection with this, about what formed the silicone material integrally after 1-day progress, adhesiveness became inferior. As described above, the microwave plasma treatment under vacuum among the plasma treatments has a high plasma density and a high reforming effect, so that more hydroxyl groups can be generated and the duration for which it can be sustained is long. confirmed. Further, according to the microwave plasma treatment under vacuum, the treatment time is short compared with other plasma treatments.

  The method for producing a composite member of the present invention is useful as a method for producing various composite members used for electronic control devices such as an engine control unit mounted on a vehicle, electronic devices for small portable terminal devices, and the like.

1: Test piece, 10: Plate member (aluminum die-cast member), 11: Silicone member, 100: One surface of plate member.

Claims (10)

A method for producing a composite member in which an aluminum die cast member and a silicone member are combined,
A removal step of irradiating plasma on the joint surface of the aluminum die cast member with the silicone member to remove the carbide film present on the joint surface;
A modification step of irradiating the bonding surface from which the carbide film has been removed with plasma to impart a hydroxyl group to the bonding surface;
A compounding step in which a silicone material is integrally formed on the bonding surface to which a hydroxyl group is imparted;
The manufacturing method of the composite member which has this.   The method for producing a composite member according to claim 1, wherein a water contact angle of the joint surface after the reforming step is 50 ° or less.   When the joint surface after the modification step is analyzed by X-ray photoelectron spectroscopy, the number of C atoms is 5% or more and 30% or less when the total number of atoms of Al, O, and C is 100%. The manufacturing method of the composite member of Claim 1 or Claim 2.   The composite member according to any one of claims 1 to 3, wherein the peel strength of the composite member is 4 N / mm or more when a 90 ° peel test specified in JIS K 6256-2: 2013 is performed. Method.   The composite member according to any one of claims 1 to 4, wherein the plasma irradiation in the removing step and the modifying step is continuously performed in a same container and in a same gas atmosphere under vacuum. Production method.   The method of manufacturing a composite member according to any one of claims 1 to 4, wherein the plasma irradiation in the removing step and the modifying step is continuously performed in an identical gas atmosphere under atmospheric pressure.   The method for producing a composite member according to any one of claims 1 to 6, wherein the reforming step and the compounding step are performed continuously or after a time of one week or less.   The method of manufacturing a composite member according to claim 1, wherein the plasma irradiation in the removing step and the modifying step is performed in a gas atmosphere containing oxygen. The gas atmosphere containing oxygen consists only of oxygen gas, or consists of a mixed gas of one or more gases selected from rare gas and nitrogen gas and oxygen gas,
The method for producing a composite member according to claim 8, wherein the content ratio of the oxygen gas in the case of the mixed gas is 30% or more when the pressure or volume of the entire mixed gas is 100%.   The method for manufacturing a composite member according to claim 1, wherein the plasma is microwave plasma.

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