JP2010059466A - Metallic material and manufacturing method thereof, and case for electronic equipment using the metallic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic material capable of enhancing the adhesiveness to a coating film and maintaining the metallic texture of a base metal, a manufacturing method thereof, a compound metallic material using the same, and a case for electronic equipment. <P>SOLUTION: The metallic material contains includes the base metal selected among a group consisting of magnesium, a magnesium alloy, aluminum, and an aluminum alloy, and hard particles which are embedded in the surface of the base metal, harder than the base metal, and has the mean grain size of 1-40 &mu;m. The hard particles are preferably one or more selected from the group consisting of Al<SB>2</SB>O<SB>3</SB>, SiO<SB>2</SB>, ZnO, ZrO<SB>2</SB>and TiO<SB>2</SB>. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a metal material excellent in adhesion and surface smoothness of a coating film, and a method for producing the same.

  Metal materials such as magnesium alloys and aluminum alloys have been used as materials for casings of portable electronic devices such as mobile phones and notebook personal computers and members of automobile parts. These materials are generally used by providing a coating film such as a transparent resin on the surface for the purpose of preventing corrosion and improving aesthetics.

In a metal material having a coating film on the surface, in order to maintain its aesthetics and anticorrosion properties over a long period of time, it is an issue to improve the adhesion strength between the metal material and the coating film. Patent Document 1 discloses a surface-treated magnesium material whose surface is roughened by shot blasting to have a predetermined surface roughness in order to increase adhesion strength.
Japanese Patent No. 3440905

  Shot blasting is a processing method in which fine particles of sand, steel, alumina, or the like (blast particles) are blown or hit against the surface of the metal to scrape the surface of the metal and make the surface uneven. With this method, it is difficult to control the surface roughness, and in places where the surface roughness is large, the metallic texture (metallic luster) of the base material may be impaired or the surface of the coating film may be uneven, which may impair the aesthetic appearance. There is sex.

  In addition, when magnesium or a magnesium alloy is used as the metal base, the scraped magnesium powder may ignite. Furthermore, since magnesium powder is mixed in the blast particles after processing, there is a problem that it is difficult to reuse the blast particles.

  In view of such problems, the present invention can improve the adhesion to the coating film and maintain the metal texture of the base material, a manufacturing method thereof, a metal composite material using the metal material, and an electronic device casing It is an issue to provide.

  As a result of earnestly examining the above problems, the present inventor sprayed hard particles having an average particle diameter of 1 μm or more and 40 μm or less higher in hardness than the base metal on the surface of the base metal base material and embedded in the surface. The inventors have found that a metal material satisfying the above required characteristics can be obtained, and completed the present invention.

  The present invention relates to a metal substrate selected from the group consisting of magnesium, magnesium alloy, aluminum, and aluminum alloy, and an average particle diameter embedded in the surface of the metal substrate and having a hardness higher than that of the metal substrate. Is a metal material having hard particles of 1 μm or more and 40 μm or less (Claim 1).

  Due to the anchor effect of the hard particles embedded in the surface, the adhesion between the metal substrate and the coating film can be improved. Moreover, adhesive force can be improved, without impairing metallic luster by making the average particle diameter of a hard particle into the range of 1 micrometer or more and 40 micrometers or less.

It said hard _{particles, Al 2 O 3, SiO 2} , ZnO, preferably the ZrO _2, and one or more selected from the group consisting of TiO _2. Hard particles made of these materials cause a mechanochemical reaction with magnesium and aluminum, not only mechanically embedded but also chemically bonded, improving the embedding strength, so the adhesion strength between the coating film and the metal substrate Can be further improved.

  Moreover, this invention provides the metal composite material which has a coating film on the surface of these metal materials (Claim 3). Such a metal composite material is excellent in corrosion resistance and coating film adhesion. In particular, by using hard particles having a refractive index close to the refractive index of the coating film, the hard particles can be made almost invisible, so that the adhesion can be improved without impairing the metallic luster.

  The present invention further includes a step of preparing a metal substrate, and spraying hard particles having an average particle diameter of 1 μm or more and 40 μm or less higher than the metal substrate on the surface of the metal substrate. A method for producing a metal material having a step of embedding in a metal is provided. By spraying hard particles on the surface of the metal substrate, the hard particles can be efficiently embedded in the surface of the metal substrate.

  The step of spraying and embedding the hard particles on the surface of the metal substrate is preferably performed by an aerosol deposition method. The aerosol deposition method is a technique in which fine particles are mixed with a gas to form an aerosol, and sprayed onto a substrate through a nozzle to form a coating. The aerosolized raw material fine particles are accelerated to a supersonic speed (several hundred m / s) by passing through a nozzle having a minute opening. The accelerated raw material fine particles collide with the substrate surface, and are mechanically embedded in the metal substrate at the time of the collision. Further, when the hard particles cause a mechanochemical reaction with the metal substrate, they are also chemically bonded, so that the embedding strength can be improved. By using such a method, a metal base material and a hard particle can be combined more firmly.

  Furthermore, the present invention provides an electronic device casing using the above metal material. Such a casing for electronic equipment can maintain the metallic luster of the base material and is excellent in the adhesion of the coating film, thereby increasing the commercial value. Examples of the electronic device include a mobile device such as a mobile phone and a personal computer.

  The metal material of the present invention can improve the adhesion to the coating film and can maintain the metal texture of the substrate.

  The metal substrate used in the present invention is selected from aluminum, aluminum alloy, magnesium, and magnesium alloy. Among these, magnesium and a magnesium alloy are preferable because they have a low specific gravity and can reduce the weight of the material. In particular, a magnesium alloy is preferable because it has excellent strength and high reactivity, and thus has high bonding properties with hard particles. The metal substrate may be used as it is, but it is preferable to perform a surface treatment such as mirror polishing, hairline processing, diamond cut processing in order to obtain a metallic luster.

As the hard particles used in the present invention, various particles can be used as long as the hardness is higher than that of the substrate. It is preferable to use hard particles that cause a mechanochemical reaction with the metal substrate. For example, for a magnesium alloy, it is preferable to use at least one selected from the group consisting of Al ₂ O ₃ , SiO ₂ , ZnO, ZrO ₂ , and TiO ₂ . The average particle diameter of the hard particles is 1 μm or more and 40 μm or less. When the average particle size is less than 1 μm, the anchor effect is difficult to obtain, and the adhesion strength of the coating film is lowered. On the other hand, if it exceeds 40 μm, the surface roughness becomes large and irregularities are likely to occur on the coating film surface. The average particle diameter can be measured by a laser diffraction scattering method.

  Various shapes such as spherical, needle-like, whisker-like, etc. can be used as the shape of the hard particles, but if the whisker-like hard particles having a diameter to length ratio (aspect ratio) of 5 or more can be used, the anchor effect can be further exhibited. , Adhesion can be improved.

  The hard particles are embedded in a dispersed state on the surface of the metal substrate. When the amount of the hard particles is 10% to 90% with respect to the entire surface area of the metal substrate, the adhesion can be improved without impairing the metallic luster, which is preferable. When fixing by spraying hard particles by the aerosol deposition method, the amount of hard particles can be adjusted by adjusting the aerosol concentration.

  As the coating film, a known paint using a transparent acrylic resin or the like can be used, and a wet method (immersion method, spray coating, electrodeposition coating, etc.), a dry method (PVD method, CVD method, etc.) A paint film can be formed on the surface of a metal material. The coating film may be colored, translucent, or transparent, but it is preferable that the coating film is transparent because the metallic texture of the substrate can be maintained. The term “transparent” refers to the extent that the substrate can be visually confirmed. In addition, if a coating film having a refractive index within 0.1 of the refractive index of the hard particles is used, the hard particles are almost invisible when observed from the outside of the coating film. Can be more maintained.

  1 and 2 are cross-sectional views schematically showing the metal composite material of the present invention. Hard particles 2 (hard particles 4 in FIG. 2) are embedded in the surface of the metal substrate 1. Some of the hard particles are embedded in the surface of the metal substrate, and some are exposed. The coating film 3 is formed on this surface. With such a configuration, the adhesion between the metal substrate 1 and the coating film 3 is improved. Also, as shown in FIG. 2, the whisker-like hard particles 4 are easily embedded in the surface of the metal substrate 1 due to their shape, and can penetrate deeper into the coating film 3, so that the anchor effect is further improved. The adhesion between the metal substrate 1 and the coating film 3 can be improved.

  Next, the best mode for carrying out the invention will be described by way of examples. The examples are not intended to limit the scope of the invention.

(Examples 1-4)
A magnesium alloy is used as the metal substrate. A rolled sheet obtained by a twin roll continuous casting method having a composition corresponding to AZ91 alloy is prepared. Rolling is performed in multiple passes under the conditions of 200 to 400 ° C for the heating temperature of the object to be processed (rolling object), 150 to 250 ° C for the heating temperature of the rolling roll, and 10 to 50% of the rolling reduction per pass. A 5 mm rolled plate is produced. The obtained rolled material is subjected to leveler processing and polishing processing in this order, and a hot press processing (press temperature 200 to 400 ° C.) is applied to the cut piece cut into a desired size to obtain a magnesium alloy casing. In order to give a metallic luster to the obtained magnesium alloy casing, the surface is subjected to mirror polishing.

(Embedded hard particles by aerosol deposition method)
An aerosol composed of hard particles and helium gas shown in Table 1 is subsonic (flow velocity of several hundred m) from a fine opening nozzle of 1 mm or less to a magnesium alloy substrate set in a vacuum chamber depressurized to 1 kPa or less. / Sec) to embed the hard particles in the surface of the magnesium alloy substrate.

(Formation of paint film)
A colorless and transparent acrylic resin paint is spray-coated on the surface of the obtained metal material and baked at 150 ° C. for 10 minutes to form a coating film, and then the following evaluation is performed.

(Transparency evaluation)
The transparency of the obtained metal oxide film is visually evaluated. The case where there is no white turbidity or the like is transparent, ◎, the case where there is almost no white turbidity or the like is transparent, ◯, the case where there is white turbidity or the like and the transparency is poor is indicated as ×

(Surface condition: surface smoothness)
It is visually evaluated whether the coating film surface is uneven. The case where there is no unevenness is indicated by ○, and the case where there is unevenness and the surface state is poor is indicated by ×.

(Surface condition: metallic luster)
Whether or not the metallic luster of the base metal substrate can be confirmed in a state where the coating film is applied is visually evaluated. The case where the metallic luster can be confirmed is marked with ◯, and the case where the metallic luster is lost and the surface condition is poor is marked with X.

(Evaluation of paint film adhesion)
In accordance with JISK5600-5-6, the adhesion of the coating film is evaluated by a cross-cut method. That is, 11 coatings are cut into the coating film at intervals of 1 mm vertically and horizontally, and an adhesive tape is pasted on the coating film and peeled off, and the number of coating films peeled off from the magnesium alloy surface is counted. The case where all 100 pieces are not peeled is denoted by ◎, the number of peeled pieces of 10 or less is indicated by ○, and the case where 11 pieces or more are peeled is indicated by ×.

(Comparative Example 1)
A shot blasting process is performed using alumina particles on a magnesium alloy substrate whose surface is mirror-polished. Further, after the base treatment is performed in the order of degreasing → acid etching → desmutting → surface adjustment, chemical conversion treatment is performed. Thereafter, a coating film is formed in the same manner as in Examples 1 to 4, and a series of evaluations is performed.
(Comparative Examples 2 and 3)
A series of evaluations is performed by embedding the hard particles in the surface of the magnesium alloy and forming a coating film in the same manner as in Examples 1 to 5 except that the hard particles shown in Table 2 are used. The above results are shown in Tables 1 and 2.

In Examples 1 to 5 using hard particles having an average particle diameter of 1 μm to 40 μm, the adhesion of the coating film is good, and the transparency, the smoothness of the coating film, and the metallic luster are also excellent. In Example 2 using SiO ₂ as the hard particles, the transparency is particularly excellent. This seems to be because the refractive index (1.5) of SiO ₂ is close to the refractive index (1.5) of the acrylic coating film. In Example 3 using whisker-like particles, the adhesion is excellent, and it can be seen that the whisker-like particles have a particularly high anchor effect.

  Comparative Example 1 subjected to the blast treatment had good transparency, but the smoothness, metallic luster and adhesion of the coating film did not satisfy the required characteristics. In Comparative Example 2 using hard particles having a small average particle diameter, the adhesion was poor. Conversely, in Comparative Example 3 using hard particles having a large average particle diameter, the adhesion was good, but the surface of the coating film The result was uneven.

It is a cross-sectional schematic diagram which shows the metal composite material of this invention. It is a cross-sectional schematic diagram which shows the metal composite material of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal base material 2 Hard particle 3 Paint film 4 Hard particle (whisker shape)

Claims (6)

  A metal substrate selected from the group consisting of magnesium, magnesium alloy, aluminum, and aluminum alloy, and an average particle diameter of 1 μm or more and 40 μm embedded in the surface of the metal substrate and having a higher hardness than the metal substrate Metal material having the following hard particles. The metal material according to claim 1, wherein the hard particles are one or more selected from the group consisting of Al ₂ O ₃ , SiO ₂ , ZnO, ZrO ₂ , and TiO ₂ .   A metal composite material comprising a coating film on the surface of the metal material according to claim 1.   A step of preparing a metal substrate, a step of spraying hard particles having an average particle diameter of 1 μm or more and 40 μm or less higher than the metal substrate onto the surface of the metal substrate, and embedding it on the surface of the metal substrate. A method for producing a metal material.   The manufacturing method of the metal material of Claim 4 which sprays the said hard particle | grain on the surface of the said metal base material, and embeds it in the surface of a metal base material by the aerosol deposition method.   A housing for an electronic device using the metal material according to claim 1 or 2, or the metal composite material according to claim 3.

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