TWI633191B - Magnesium-based metal member, and method for manufacturing magnesium-based metal member - Google Patents

Abstract

The present invention provides a magnesium-based metal member in which the coating film is less deteriorated and can maintain a metallic texture, and a method for producing the same. The magnesium-based metal member includes a base material made of a magnesium-based metal and a transparent coating film formed on the surface of the base material. The coating film system includes a transparent anticorrosive film formed on the surface of the substrate, and one or more transparent coating films formed of a resin formed on the anticorrosive film. The coating film has at least one weather resistant layer to which an ultraviolet absorber is added.

Description

Magnesium-based metal member, and method for manufacturing magnesium-based metal member

The present invention relates to a magnesium-based metal member comprising a base material made of a magnesium-based metal and a transparent coating film formed on a surface of the base material, and a method for producing the same.

Magnesium alloys are used in mobile phones or laptops for portable electrical appliances, electronic devices, and other components, such as mobile phones and laptops, because of their light weight and high strength. In recent years, it has been desired that the magnesium alloy member such as the outer frame described above has a metallic texture and exhibits a high-grade feeling.

Further, since magnesium is easily corroded when it is an active metal, a coating layer having corrosion resistance is formed on the surface of the substrate in the magnesium alloy member.

For example, Patent Document 1 discloses a magnesium alloy which is formed by forming a transparent coating layer on the surface of a substrate by performing fine concavo-convex processing such as a diamond cutter on a surface of a substrate made of a magnesium alloy. member. Further, the coating layer has a multilayer structure in which an anticorrosive layer formed by an anticorrosive treatment (chemical formation treatment or anodization treatment) and a coating layer formed of a resin such as an acrylic resin thereon are provided.

[Practical Technical Literature] [Patent Document]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2009-120877

The above-described magnesium alloy member having a transparent coating layer is expected to maintain a metallic texture after a long period of time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnesium-based metal member which is less in deterioration of a coating film and which can maintain a metallic texture after a long period of time, and a method for producing the same.

The magnesium-based metal member of the present invention comprises a base material made of a magnesium-based metal and a transparent coating film formed on the surface of the base material. The coating film system includes a transparent anticorrosive film formed on the surface of the substrate, and one or more transparent coating films formed of a resin formed on the anticorrosive film. Next, the coating film has at least one weather resistant layer in which an ultraviolet absorber is added to the resin.

According to the magnesium-based metal of the present invention (hereinafter referred to as "Mg-based metal"), the coating film has at least one weather-resistant layer, and the resin forming the coating film can be prevented from being generated by ultraviolet rays. Deteriorating situation. In other words, by imparting weather resistance to the coating film, the coating film due to ultraviolet rays can be yellowed, the gloss is lowered, cracking, peeling, foaming, and the like are less likely to occur, and the coating film can be ensured after a long period of time. Transparency or density It is connected and maintains metal texture. Further, in the present invention, the Mg-based metal is a metal containing Mg as a main component, and the Mg-based metal contains pure Mg and a Mg alloy.

The resin for forming the coating film may, for example, be an epoxy resin, an acrylic resin, a urethane resin, a polyester resin or a fluororesin, and these resins may be used alone or in combination of two or more. For example, when the coating film has a multilayer structure of two or more layers, the resin for forming each layer can be changed. Further, a coating layer in which two or more kinds of resins are blended may be applied to form each layer. The coating film may also be colored and transparent, and when it is colorless and transparent, it is easy to feel the color or texture of the substrate of the Mg-based metal itself. In the present invention, since both the anticorrosive film and the coating film are transparent films, the metal texture of the substrate itself can be felt. Further, in the present invention, transparency means transparency to the extent that the substrate can be visually confirmed.

[In order to implement the invention]

As one form of the magnesium-based metal member of the present invention, for example, the coating film is made of an epoxy resin.

In the conventional magnesium alloy member, a coating layer of one layer is formed using an acrylic resin, but the adhesion between the acrylic resin and the base material (anti-corrosion film) of the Mg-based metal is low, and the coating layer may be caused by prolonged use. Stripped. When the coating layer is peeled off, the corrosion resistance is lowered, and the metal texture is impaired due to corrosion of the substrate. According to the above configuration of the present invention, the coating film formed on the anticorrosive film is formed of an epoxy resin, whereby the adhesion to the substrate (anticorrosive film) of the coating film can be improved.

Another form of the magnesium-based metal member of the present invention may, for example, be a system The innermost layer of the coating film formed on the anticorrosive film and the outer layer of at least one layer formed on the innermost layer are provided, and the innermost layer is made of an epoxy resin.

According to the above configuration of the present invention, the coating film has a multilayer structure of at least two layers of the innermost layer and the outer layer, and the innermost layer is formed of an epoxy resin, whereby the substrate for the coating film can be improved (prevention Corrosion film).

Further, in the present invention, the epoxy resin is a resin containing an epoxy resin as a main component, and other resins such as the above-mentioned acrylic resin, polyester resin or modified resin may be added to the epoxy resin, or Hardener, etc.

As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, bisphenol S type epoxy resin, brominated bisphenol A type epoxy resin, hydrogenation double can be used. Phenolic A type epoxy resin, etc. Among the epoxy resins, a phosphoric acid-modified epoxy resin which is more excellent in adhesion to a substrate (anti-corrosion film) is preferably used. The phosphoric acid-modified epoxy resin is obtained by reacting a bisphenol epoxy resin with a phosphoric acid compound. In this case, the bisphenol type epoxy resin to be used is not particularly limited, and the above bisphenol type epoxy resin can be used. Among the above bisphenol type epoxy resins, a bisphenol A type epoxy resin is preferred.

The phosphoric acid compound is a phosphoric acid having two or more hydroxyl groups bonded to a phosphorus atom, specifically, a conjugated phosphoric acid such as o-phosphoric acid or sulfonic acid, methylphosphoric acid or pyrophosphoric acid or tripolyphosphoric acid, or monomethylphosphoric acid. Or an orthophosphate such as monobutylphosphoric acid, monooctylphosphoric acid or monophenylphosphoric acid.

As the curing agent to be added to the epoxy resin, a melamine compound or an isocyanate compound having good adhesion to the anticorrosive film is preferably used. As As the melamine compound, methoxylated methylol melamine, butoxylated methylol melamine or the like is used. As the isocyanate compound, methylphenyl diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, diisophorone diisocyanate or the like is used, or the isocyanate is modified by uretization or grafting. A quality, isocyanate modified resin. The isocyanate compound is preferably a blocked isocyanate compound having an isocyanate group block by a block agent. This reason is because the isocyanate group is easily reacted, and when the coating composition is left at a normal temperature for a long period of time, the reaction proceeds slowly, and the characteristics of the composition change.

As a block agent such as methyl ethyl ketone oxime, acetone oxime, cyclohexanone oxime, acetophenone oxime, benzophenone oxime, etc.; phenols such as m-cresol, xylenol; butanol, Alcohols such as 2-ethylhexanol, cyclohexanol, ethylene glycol monoethyl ether; lactones such as ε-caprolactone, δ-valerolactone, γ-butyrolactone; diethyl malonate And ketones such as acetonitrile acetate; thiols such as thiophenol; ureas such as thiouric acid; imidazoles; urethanes. Among them, terpenoids, phenols, alcohols, lactones, and diketones are preferred.

The epoxy resin can be cured by a curing method such as hot baking or ultraviolet irradiation after coating to form a hard coating film.

When the epoxy resin is compared with an acrylic resin, it has high adhesion to a base material (anticorrosive film) of a Mg-based metal, and has low weather resistance and is easily deteriorated by ultraviolet rays, and it is difficult to maintain transparency or adhesion for a long period of time. . However, in the present invention, at least one of the coating films (when the coating film is one layer is itself) is a weather resistant layer, and the coating film itself or the epoxy resin forming the innermost layer thereof can be suppressed from ultraviolet rays. And the situation worsens, and after a long time Transparency or adhesion can be maintained. As described below, the ultraviolet absorber may be added to the epoxy-based tree forming the innermost layer, and the innermost layer itself may be used as the weather-resistant layer.

In the above aspect in which the coating film has the innermost layer and at least one outer layer, at least one of the outermost layers is made of an acrylic resin.

At least one layer of the outer layer is formed of an acrylic resin, and abrasion resistance such as thixotropic resistance and scratch resistance can be imparted to the coating film. In particular, when the innermost layer of the coating film is formed of an epoxy resin and the outermost layer is formed of an acrylic resin, the adhesion between the coating film and the abrasion resistance can be made to stand. The acrylic resin can be cured by a hardening method such as hot baking or ultraviolet irradiation after coating.

In the present invention, the acrylic resin is a resin containing an acrylic resin as a main component, and for example, the above-mentioned fluororesin, polyester resin, urethane resin, modified urethane may be added to the acrylic resin. Other resins such as resins, hardeners, and the like. When the coating film has a multilayer structure, it is preferred that the outermost layer be an acrylic resin.

The acrylic resin can be obtained by polymerizing an acrylic monomer using a polymerization initiator, and also includes a modified acrylic resin. The acrylic monomer may, for example, be methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, methyl methacrylate or methyl. Acrylic acid or alkyl methacrylate such as ethyl acrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate or lauryl methacrylate; Methoxyethyl acrylate, methoxyethyl methacrylate An alkoxyalkyl acrylate or methacrylate of an ester, methoxybutyl acrylate, methoxybutyl methacrylate, ethoxybutyl acrylate, ethoxybutyl methacrylate, etc.; Acrylic acid or methacrylic acid ester such as ester, allyl methacrylate; hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, hydroxypropyl acrylate a hydroxyalkyl ester of acrylic acid or methacrylic acid such as hydroxypropyl methacrylate; acrylonitrile of acryl or methacrylic acid such as allyloxyethyl acrylate or allyloxyethyl methacrylate; Alkyl ester; acrylamide, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, and the like. These may be used alone or in combination of two or more. As the acrylic single system, methacrylic acid having excellent transparency is preferable, and methyl methacrylate is particularly preferable. Further, these acrylic monomers and other vinyl monomers may be used in combination. Examples of other vinyl monomers include vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene; and olefins such as butadiene, isoamylene, and chloropentene. a compound; vinyl acetate, allyl alcohol, maleic acid, and the like.

As the polymerization initiator, for example, a peroxide such as benzammonium peroxide or t-butyl-peroxy-2-ethylhexanoate; azobisisobutyronitrile or azobisdimethylam can be used; An azo compound such as a nitrile.

As the curing agent to be added to the acrylic resin, a melamine compound or an isocyanate compound having good adhesion to the innermost layer (for example, an epoxy resin) is preferably used. As the melamine compound, methoxylated methylol melamine, butoxylated methylol melamine or the like is used. As the isocyanate compound, methylphenyl diisocyanate, diphenylmethane diisocyanate, and hexamethylene are used. A resin such as a bis-isocyanate or an isophorone diisocyanate, or a modification in which the isocyanate is modified, catalyzed, or modified with an isocyanate.

The polymerization method of the acrylic monomer is not particularly limited, and a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or the like can be used.

The glass transition temperature (Tg) of the acrylic resin to be used is preferably -60 ° C or more and 90 ° C or less. When the Tg is -60 ° C or more, the coating film or layer formed of the acrylic resin is excellent in moisture resistance and temperature resistance, and when the Tg is 90 ° C or lower, the coating film or layer formed of the acrylic resin is used. Good adhesion.

In the above aspect in which the coating film has the innermost layer and at least one outer layer, for example, at least one layer of the outer layer and the outermost layer each have a weather resistant layer in which an ultraviolet absorber is added to the resin.

According to this configuration, the innermost layer itself is a weather-resistant layer in which an ultraviolet absorber is added to the resin, and at least one layer of the outer layer is a weather-resistant layer, so that the innermost layer can be reliably protected (for example, an epoxy resin) In the case of deterioration due to ultraviolet rays, transparency or adhesion can be sufficiently maintained after a long period of time.

In the above aspect in which the coating film has the innermost layer and at least one outer layer, the innermost layer may have a thickness of 5 μm or more and 50 μm or less, and the outer layer may have a thickness of 5 μm or more and 100 μm or less.

When the thickness of the innermost layer (for example, an epoxy resin) is 5 μm or more and 50 μm or less, sufficient adhesion or corrosion resistance can be obtained. Further, since the thickness of the outer layer is 5 μm or more and 100 μm or less, sufficient corrosion resistance can be obtained. In addition, when the innermost layer and the outer layer are too thick, there is a fear of transparency degradation. Low and the problem of poor adhesion.

In one embodiment of the magnesium-based metal member of the present invention, for example, the anticorrosive film is a zirconia film.

The anti-corrosion film is formed on the surface of the base of the Mg-based metal to impart corrosion resistance to the substrate and improve coating adhesion. The anticorrosive film can be formed by performing an anti-corrosion treatment of a chemical conversion treatment or an anodization treatment. The chemical conversion treatment may, for example, be a zirconium chemical conversion treatment, a chromate treatment, a manganese chemical conversion treatment, or a phosphoric acid chemical conversion treatment.

Among them, the zirconia-forming film formed by the zirconia formation treatment which is one of the zirconium formation treatments is mainly composed of zirconia and has strong resistance to an acid or a base. Further, the zirconia-forming film can improve the adhesion to the coating film, and by blending the resin and the coupling agent, the coating adhesion can be further improved. Further, when the zirconia-forming film is compared with a film of a compound such as phosphate formed by a phosphate-based chemical conversion treatment, transparency is high and metal texture can be easily improved.

When the anticorrosive film is in the above-described form of the zirconia-forming film, for example, zirconium oxide formed film contains 10 mg/m ² or more and 150 mg/m ² or less of zirconium, and the thickness thereof is 10 nm or more.

When the zirconium content of the film formed by zirconia is 10 mg/m ² or more and 150 mg/m ² or less, and the thickness thereof is 10 nm or more, sufficient acid resistance, alkali resistance, or adhesion can be obtained. A preferred zirconia-forming film has a thickness of 20 nm or more. When the thickness of the zirconia film is too thick, the transparency is lowered and the adhesion is lowered. Therefore, the upper limit is preferably 1 μm or less.

One form of the magnesium-based metal member of the present invention may, for example, be ultraviolet rays. The absorbent is an organic ultraviolet absorber.

The ultraviolet absorber preferably has an absorption property in an ultraviolet region of 290 to 380 nm in which the resin (particularly an epoxy resin) is most deteriorated, and has no absorption property in the visible light region. As the ultraviolet absorber, any of an organic system and an inorganic system can be used. The organic absorber may, for example, be a benzophenone type, a benzotriazole type, an oxalic acid aniline type, a cyanoacrylate type, or a triazine type. Further, examples of the inorganic absorber include particulate titanium oxide, zinc oxide, iron oxide, and cerium oxide. As the ultraviolet absorber, the above-exemplified absorbents may be used singly or in combination of two or more kinds thereof to adjust the above characteristics. When the organic absorbent is compared with an inorganic absorbent, it is preferable in terms of high transparency.

When an organic ultraviolet absorber is used, it is preferably selected in consideration of heat resistance or durability of the absorbent. The heat resistance is such that when the coating film is formed and the resin is baked, the absorbent does not decompose by heat, and the durability is such that the ultraviolet absorbing effect does not deteriorate when exposed to ultraviolet rays for a long period of time. As a commercial item of the organic ultraviolet absorber, for example, TINUVIN (registered trademark) 479, TINUVIN 928, TINUVIN 405, etc., manufactured by Chiba Japan Co., Ltd. (now BASF Japan) can be used. Moreover, as long as it is the same effect, it can be used similarly.

When an inorganic ultraviolet absorber is used, it is desirable to suppress visible light scattering in order to improve transparency. Specifically, the particle size is made fine (for example, the average particle diameter (the intermediate diameter (D50) corresponding to 50% of the cumulative distribution on a volume basis) is 0.01 to 0.05 μm), and the composition can also be coated. The difference in refractive index of each layer of the film is reduced. Inorganic purple For the commercial product of the external absorbent, for example, NANOBYK (registered trademark)-3812, NANOBYK-3821, NANOBYK-3841, NANOBYK-3842, etc., manufactured by BYK-Chemie Co., Ltd., are used.

In addition, when the amount of the ultraviolet absorber is, for example, an organic absorbent, it is 0.01 to 20 parts by mass, preferably 0.5 to 10 parts by mass, more preferably 1 to 1 part by mass based on 100 parts by mass of the resin solid content. 5 parts by mass. Further, when a light stabilizer (HALS: Hindered Amine Light Stabilizer) is added in addition to the ultraviolet absorber, durability (weather resistance) can be further improved. The amount of the light stabilizer to be added is, for example, preferably from 0 to 3.0 parts by mass based on 100 parts by mass of the resin solid content. The respective amounts of the ultraviolet absorber and the light stabilizer can be appropriately adjusted within a range that does not impair the transparency of the coating film.

As a commercial product of the light stabilizer (HALS), for example, "SANOL (registered trademark) LS770, LS765" manufactured by SANKYO LIFETECH Co., Ltd., "TINUVIN 144" manufactured by Chiba Japan Co., Ltd., and "ADEKA" can be used. ADEKA STAB (registered trademark) LA-57, LA-62, LA-63, LA-67, LA-68, LA-82" and the like. When the resin (coating) is baked at a high temperature, it is particularly preferable to use TINUVIN 123.

In one embodiment of the magnesium-based metal member of the present invention, for example, fine concavo-convex processing is performed on at least a part of the surface of the substrate.

The metal texture can be improved by performing fine uneven processing on at least a part of the surface of the base material of the Mg-based metal. Fine uneven processing, such as cutting, grinding, blowing, and using acid rot At least one of the etching processes. Specifically, for example, at least one of fine wire processing, diamond cutting processing, rotary cutting processing, sand blast processing, and etching processing. These processes may be used singly or in combination of two or more. The fine concavo-convex processing can be carried out only on one part of the surface of the substrate, or can be fully implemented.

In one embodiment of the magnesium-based metal member of the present invention, for example, a magnesium-based metal is a magnesium alloy containing 3% by mass or more of aluminum.

The Mg alloy may, for example, be a composition containing various elements of an additive element (residue: Mg and impurities). Among them, the Mg-Al alloy containing Al as an additive element is preferable in terms of excellent mechanical strength such as corrosion resistance and strength. When the content of Al is increased, it tends to improve mechanical properties such as corrosion resistance and strength. Therefore, it is preferable to contain 3 mass% or more of Al, and it is more preferable to contain 7.3 mass% or more. When the content of Al exceeds 12% by mass, the plastic workability is lowered, and the upper limit is preferably 12% by mass. In particular, the content of Al is preferably 11% by mass or less, more preferably 8.3 to 9.5% by mass.

Addition elements other than Al, for example, selected from Zn, Mn, Si, Be, Ca, Sr, Y, Cu, Ag, Sn, Ni, Au, Li, Zr, Ce, and rare earth elements (except Y and Ce) At least one of the elements. When such an additive element is contained, the content thereof is preferably 0.01 to 10% by mass in total, more preferably 0.1 to 5% by mass. In the above-mentioned additive elements, at least one element selected from the group consisting of Si, Sn, Y, Ce, Ca, and rare earth elements (excluding Y and Ce) is 0.001% by mass or more in total, preferably When the total amount is 0.1 to 5% by mass, heat resistance or flame retardancy can be improved. And, it’s thin In the case of the earth element, it is preferably 0.1% by mass or more, and Y is preferably 0.5% by mass or more. As an impurity, for example, Fe or the like can be exemplified.

Specific examples of the Mg-Al-based alloy include an AZ-based alloy (Mg-Al-Zn-based alloy, Zn: 0.2 to 1.5% by mass), and an AM-based alloy (Mg-Al-Mn-based alloy). Mn: 0.15 to 0.5% by mass), Mg-Al-RE (rare earth element) alloy, AX alloy (Mg-Al-Ca alloy, Ca: 0.2 to 6.0% by mass), and AJ alloy (Mg-Al) -Sr-based alloy, Sr: 0.2 to 7.0% by mass). In particular, a Mg-Al alloy containing 8.3 to 9.5% by mass of Al and 0.5 to 1.5% by mass of Zn, and a typical example of AZ91 have higher specific strength and excellent corrosion resistance than other AZ alloys. Or better in terms of impact resistance.

Further, the method for producing a magnesium-based metal member according to the present invention is a method for producing a transparent coating film formed on a surface of a substrate made of a magnesium-based metal, and has the following steps.

An anti-corrosion step of applying a corrosion-resistant treatment to the substrate to form a transparent anti-corrosion film on the surface of the substrate.

A coating step of applying a resin to the anticorrosive film to form a transparent coating film of one or more layers.

Next, the coating step forms a weather-resistant layer in which at least one layer of the ultraviolet absorber is added to the resin as a coating film.

In one embodiment of the production method of the present invention, for example, at least one layer of the coating film may be formed of an epoxy resin to which an ultraviolet absorber is added.

As one form of the production method of the present invention, the coating step can be exemplified For example, an outer layer of at least one of the innermost layer and the innermost layer is formed on the anticorrosive film as a coating film. Then, in the coating step, for example, the innermost layer is formed of an epoxy resin, and at the same time, at least one layer of the outer layer is formed of an acrylic resin, and at least one of the innermost layer and the outer layer is added with ultraviolet absorption in the resin. The weather resistant layer of the agent.

According to the method for producing a Mg-based metal member of the present invention, it is possible to produce the Mg-based metal member of the present invention which is less deteriorated in the coating film and which maintains the metallic texture after a long period of time.

As a means for coating the resin (coating), for example, a conventional means such as spray coating or electrofusion coating can be employed. Further, after the resin is applied, it is hardened by baking to form a coating film firmly.

In addition, in addition to the above steps, before the anti-corrosion step of performing anti-corrosion treatment on the substrate, a surface treatment step of performing surface treatment such as degreasing, etching, decontamination, surface adjustment, etc. on the substrate may be provided as needed. .

The magnesium-based metal member of the present invention can have at least one weather-resistant layer by the coating film, so that the coating film is less deteriorated, and the metal texture can be maintained after a long period of time. Further, in the method for producing a magnesium-based metal structure of the present invention, the above-described magnesium-based metal structure of the present invention can be produced.

In particular, at least one layer constituting the coating film is made of an epoxy resin, and the water resistance of the coating film can be improved. In addition, when the innermost layer is made of an epoxy resin containing a phosphoric acid-modified epoxy resin as a main component and the outer layer is made of an acrylic resin, in addition to the above effects, the corrosion resistance of the coating film can be improved or hardness.

The Mg-based metal member of the present invention was fabricated and evaluated.

[Example 1]

A rolled plate corresponding to a Mg alloy of AZ91 (Mg-9.0% by mass of Al-1.0% by mass of Zn) was prepared and cut into appropriate sizes to obtain a plurality of substrates. Then, the substrate is subjected to a degreasing treatment as a surface treatment, and then the zirconia formation treatment is performed on the substrate as an anti-corrosion treatment, and a zirconia-forming film of an anti-corrosion film is formed on the surface of the substrate. The degreasing treatment and the chemical conversion treatment were carried out under the following conditions.

(degreasing treatment)

Stirring with 10% KOH and a nonionic surfactant 0.2% solution at 60 ° C for 10 minutes

(Chemical processing)

Under stirring with a chemical treatment agent containing zirconium, 35 ° C, 1 minute

When the surface of the substrate on which the zirconia film was formed was visually observed, the zirconia film was almost colorless and transparent. Further, when the content of zirconium contained in the zirconia-forming film is measured by a fluorescent X-ray optical analyzer, the zirconium content in the zirconia-forming film is about 45 mg/m ² .

Anti-corrosion film (zirconia formed into a film) formed on the surface of the substrate The coating material A or the coating material B described in Table 1 was spray-coated and baked at 150 ° C for 20 minutes to form a coating film formed of an epoxy resin or an acrylic resin.

In this example, the coating A and the coating B were used with or without the addition of the ultraviolet absorber. TIUVVIN 928 is used for the ultraviolet absorber, and the amount of the ultraviolet absorber added is 1.8 parts by mass based on 100 parts by mass of the resin solid component. Then, a Mg-based metal member having a coating film having an anticorrosive film and a coating film and samples No. 1-1 to No. 1-4 shown in Table 2 was formed on the surface of the base material of the Mg alloy.

When the respective thicknesses of the formed anticorrosive film and the coating film were measured, the thickness of the anticorrosive film was 20 nm, and the thickness of the coating film was 10 μm. Further, each of the thicknesses was observed by a scanning electron microscope (SEM), and when a cross section of the substrate of the anticorrosive film and the coating film was formed, 10 points were measured in the observation field of view, and the average value thereof was obtained.

In the Mg-based metal members of Sample Nos. 1-1 to 1-4, when the appearance (base surface) was visually observed, the coating film was colorless and transparent, and had an excellent metallic texture.

Next, the Mg-based metal members of the samples No. 1-1 to No. 1-4 were evaluated for the adhesion test, the corrosion resistance test (saline spray test and artificial sweat test), the water resistance test, and the water resistance test described below. Pencil hardness test and weather resistance test. The results are shown in Table 3.

<Adhesion test>

The adhesion test was carried out in accordance with the test method specified in JIS K5600-5-6:1999 (General Test Method for Coatings - Mechanical Properties of Coating Film - Adhesion (Cross Cutting Method)). This test is performed on a coating film on the surface of a Mg-based metal member, and is cut at intervals of 1 mm in the vertical and horizontal directions on the substrate to form a lattice pattern of 10 × 10 squares, and then tape is attached to the lattice pattern to be peeled off. The adhesion of the coating film (coating film) was evaluated. Next, the number of strips to be stripped is calculated by visually checking whether or not the square of the lattice is peeled off (peeling off). When all the squares (100 pieces) are not peeled off, it is preferable to evaluate the adhesion of the coating film. In Table 3, the adhesion evaluation is good (the number of grids without peeling is 100) is ○, when it is slightly unsatisfactory (the number of lattices without peeling is 70 or more) is Δ, and when it is not good (the number of lattices not peeled off is less than 70) is ×, and the number of squares in parentheses is indicated (number of grids without peeling/ The total number of grids).

Further, the evaluation of the adhesion was performed by directly adhering the test to the Mg-based metal member, and performing the first-time adhesion with the salt spray test, the artificial sweat test, and the water resistance test described below.

<Corrosion resistance test> (Saline spray test)

The salt spray test was carried out in accordance with the test method specified in JIS Z2371:2000 (Salt Spray Test Method). In the test, an aqueous sodium chloride solution (saline) was sprayed onto a Mg-based metal member under the conditions shown below, and the corrosion resistance was evaluated. After the test, it was confirmed by visual inspection whether the appearance was corroded on the substrate or discolored or expanded on the coating film. When there was no abnormality and no change, the corrosion resistance of the salt spray test was preferably evaluated.

<Salt spray test conditions>

Saline concentration: 5 mass%

Test temperature: 35 ° C

Test time: 100 hours

Further, after the salt spray test, the above adhesion test was carried out to evaluate the secondary adhesion.

(Artificial sweat test)

In the artificial sweat test, the Mg-based metal member was immersed in artificial sweat under the following conditions to evaluate the corrosion resistance. After the test, it was visually inspected whether or not the appearance was corroded on the substrate or discolored or swelled on the coating film. When there was no abnormality or change, the corrosion resistance by the artificial sweat test was evaluated as good.

<Artificial sweat test conditions>

Artificial sweat: Add acetic acid and disodium phosphate to an aqueous solution of sodium chloride to adjust the pH to an acidic solution of 4.0.

Test temperature: 40 ° C

Test time: 120 hours

Further, after the artificial sweat test, the above-described adhesion test was carried out to evaluate the second adhesion.

<Water resistance test>

In the water resistance test, the Mg-based metal member was immersed in warm water of 60 ° C for 9 hours, and the water resistance was evaluated. The Mg-based metal member is taken out from the warm water, and the moisture on the surface of the coating film is removed, and after the surface temperature is room temperature (about 25 ° C), it is visually inspected whether the appearance is corroded or coated on the substrate. In the case of discoloration or swelling, rupture, peeling, etc., as long as there is no abnormality and no change, the corrosion resistance of the artificial sweat test is preferably evaluated.

In addition, after the water resistance test, the above adhesion test was carried out, and the evaluation was carried out. Estimate the second adhesion.

<Pencil hardness test>

The pencil hardness test was carried out in accordance with the test method specified in JIS K5600-5-4:1999 (General Test Method for Coatings - Mechanical Properties of Coating Film - Draw Hardness (Pencil Method)). This test was carried out using a Uni (registered trademark) pencil manufactured by Mitsubishi Pencil Co., Ltd., and when subjected to a load of 750 g, it was evaluated by the hardest pencil hardness which did not cause a mark.

<Weatherability test>

The weather resistance test was carried out in accordance with the test method specified in JIS K5600-7-7:2008 (General Test Method for Coatings - Long-Term Durability of Coating Film - Promotion of Weather Resistance and Promotion of Light Resistance (Xenon Lamp Method)). In this test, the xenon arc was irradiated to the Mg-based metal member under the following conditions, and the weather resistance was evaluated. When the appearance was visually inspected, whether or not the yellowing or the like was caused to occur on the coating film (coating film) after the test, and the weather resistance was evaluated without deterioration or deterioration.

<Weather resistance test conditions>

Radiation: 60W/m ²

Test temperature: 63 ° C

Wet cycle: continuous operation, 18 minutes (wet time) / 102 minutes (drying time), relative humidity 50% during drying

Test time: 200 hours

In samples No. 1-1 and No. 1-2 in which the coating film was formed of an epoxy resin (phosphorus modified epoxy resin), sample No. 1-1 in which no ultraviolet absorber was added to the resin was used. After the weather resistance test, the coating film turned yellow, which impaired the creative or metallic texture. On the other hand, in the sample No. 1-2 in which the ultraviolet absorber was added to the resin, the coating film did not deteriorate in yellow after the weather resistance test, and the transparency of the coating film was sufficiently ensured. Maintain a metallic texture.

Sample Nos. 1-3 and No. 1-4 using an acrylic resin in the resin for forming a coating film, the weather resistance was not affected by the addition of the ultraviolet absorber, but the water resistance was compared with the case of using an epoxy resin. The second adhesion after the test was not good.

[Example 2]

In the same manner as in Example 1, a base material of a Mg alloy corresponding to AZ91 was prepared, and a zirconia-forming film of an anticorrosive film was formed on the surface of the substrate.

After coating the coating material A or the coating material B described in Table 4 on the anticorrosive film (zirconia formed film) formed on the surface of the substrate, each of the coating materials C described in Table 4 was applied thereon to form an epoxy resin or acrylic resin. A coating film having a two-layer structure of an innermost layer formed of a resin and an outer layer made of an acrylic resin. The coating of the innermost layer and the coating of the outer layer were each carried out under the following conditions.

(coating of the innermost layer)

Spray coating the innermost layer to form a coating, and then perform 150 ° C × 20 minutes Baking

(coating of the outer layer)

After the spray coating outer layer is formed into a coating, baking is performed at 150 ° C for 20 minutes.

In this example, the coating A or the coating C used was each added with or without an ultraviolet absorber. Paint B is used without the addition of UV absorbers. As the ultraviolet absorber, the same TINUVIN 928 as in Example 1 was used, and the amount of the ultraviolet absorber added was 1.8 parts by mass based on 100 parts by mass of the resin solid component. Then, a coating film having an anticorrosive film and a coating film was formed on the surface of the base material of the Mg alloy, and samples No. 2-1 to No. 2-4 and No. 2-6 shown in Table 5 were prepared. No. 2-7 Mg-based metal member.

When the thicknesses of the formed anticorrosive film and the coating film (the innermost layer and the outer layer) were measured in the same manner as in Example 1, the thickness of the anticorrosive film was 20 nm, the thickness of the innermost layer and the outer layer were each 10 μm, and the thickness of the entire coating film was 20 μm.

In addition, in the other sample, the Mg-based sample No. 2-5 shown in Table 5 was produced in the same manner as in the sample No. 2-2 except that the surface of the base material of the Mg alloy was subjected to a diamond cutting process as a fine uneven process. Metal components. The diamond cutting process is carried out using a commercially available diamond cutting machine, which is carried out on the entire surface of the substrate. The diamond cutting process is carried out under the following conditions.

(diamond cutting processing)

Processing radius: 50mm, depth: 0.02mm (20μm), spacing: 0.05mm

When the appearance (base surface) of the Mg-based metal member of Sample Nos. 2-1 to No. 2-7 was visually observed, the coating film was colorless and transparent, and had an excellent metallic texture.

Next, the Mg-based metal members of Sample Nos. 2-1 to No. 2-7 were evaluated in the same manner as in Example 1.

The results are shown in Table 6.

In samples No. 2-1 to No. 2-5 in which the innermost layer was formed of an epoxy resin, no ultraviolet absorber was added to the resin formed in any of the innermost layer and the outer layer, and the coating film did not have Sample No. 2-1 of the weather resistant layer showed yellowing of the innermost layer (epoxy resin) after the weather resistance test, and impaired creativity or metallic texture. In this case, Sample No. 2-2 to No. 2-5 having a weather-resistant layer containing an ultraviolet absorber in the resin forming the outermost layer and the outer layer were not even after the weather resistance test. When the coating film is yellowed, the transparency of the coating film can be sufficiently ensured, and the metallic texture can be maintained. Further, in Sample Nos. 2-2 to No. 2-5, an ultraviolet absorber was added to the resin forming the coating film (the innermost layer or the outer layer), and the adhesion was made or compared with the sample No. 2-1. Corrosion resistance and water resistance are not reduced.

Sample No. 2-6 and No. 2-7 using an acrylic resin in the innermost layer forming resin, after the corrosion resistance test (saline spray test and artificial sweat test) or after using the epoxy resin There is discoloration after the water resistance test, and the secondary adhesion after the artificial sweat test or the water resistance test is not good.

Further, the present invention is not limited to the embodiments described above, and may be appropriately modified without departing from the scope of the invention. For example, the composition of the Mg alloy, the type of the anticorrosive film, the type or thickness of the resin forming the coating film (the innermost layer and the outer layer), the number of layers of the outer layer, and the like can be appropriately changed. Further, in the present invention, when the requirements for corrosion resistance are low, the coating film is thick, and corrosion resistance is ensured, an anticorrosive film may not be provided.

[industrial use value]

The Mg-based metal member of the present invention can be suitably used in a portable electronic device for a mobile phone or a portable computer, a frame for a mobile device, or an interior of a transport device, and the like, and particularly requires a field of creativity.

The present invention has been described with reference to the particular embodiments of the present invention, and various modifications and changes may be made without departing from the spirit and scope of the invention.

The present invention is based on Japanese Patent Application No. 2013-090657, filed on Jan.

Claims (15)

A magnesium-based metal member comprising a base material made of a magnesium-based metal and a magnesium-based metal member formed of a transparent coating film formed on a surface of the base material, wherein the coating film system is formed in: a transparent anticorrosive film on the surface of the substrate, and one or more transparent coating films formed of a resin formed on the anticorrosive film, wherein the coating film has at least one layer in which a UV absorber is added to the resin. The weather resistant layer includes an innermost layer formed on the anticorrosive film and an outer layer formed on at least one of the innermost layers, and the innermost layer is made of an epoxy resin. The magnesium-based metal member according to claim 1, wherein at least one of the outer layers is made of an acrylic resin. The magnesium-based metal member according to claim 1 or 2, wherein at least one of the outer layer and the innermost layer are each provided with a weather-resistant layer of an ultraviolet absorber in the resin. The magnesium-based metal member according to claim 1, wherein the innermost layer has a thickness of 5 μm or more and 50 μm or less, and the outer layer has a thickness of 5 μm or more and 100 μm or less. The magnesium-based metal member according to claim 1, wherein the coating film is made of an epoxy resin. The magnesium-based metal member according to claim 1, wherein the epoxy resin-based modified epoxy resin constituting the epoxy resin is used. The magnesium-based metal member of claim 1, wherein the foregoing anti-corrosion film It is a film formed by zirconia. The magnesium-based metal member according to claim 7, wherein the zirconia-forming film system contains zirconium of 10 mg/m ² or more and 150 mg/m ² or less, and has a thickness of 10 nm or more. The magnesium-based metal member according to claim 1, wherein the ultraviolet absorber is an organic ultraviolet absorber. A magnesium-based metal member according to claim 1, which is subjected to fine uneven processing on at least a part of the surface of the substrate. The magnesium-based metal member according to claim 10, wherein the uneven processing is at least one of a thin wire processing, a diamond cutting process, a rotary cutting process, a sandblasting process, and an etching process. The magnesium-based metal member according to claim 1, wherein the magnesium-based metal is a magnesium alloy containing 3% by mass or more of aluminum. A method for producing a magnesium-based metal member, which is a method for producing a magnesium-based metal member having a transparent coating film formed on a surface of a substrate made of a magnesium-based metal, comprising: performing anti-corrosion treatment on the substrate An anti-corrosion step of forming a transparent anti-corrosion film on the surface of the substrate; a coating step of coating the resin on the anti-corrosion film to form a transparent coating film of one or more layers, and the coating step is formed on the resin At least one weather resistant layer of the ultraviolet absorber is added as a coating film, and the coating film includes an innermost layer formed on the anticorrosive film and at least one layer formed on the innermost layer. The outer layer and the innermost layer are made of an epoxy resin. The method for producing a magnesium-based metal member according to claim 13, wherein the coating step is such that at least one layer of the coating film is formed of an epoxy resin to which an ultraviolet absorber is added. The method for producing a magnesium-based metal member according to claim 13, wherein the innermost layer is formed on the anti-corrosion film and the outer layer is formed on the innermost layer as a coating film in the coating step, and the coating is performed. In the coating step, the innermost layer is formed of an epoxy resin, and at least one layer of the outer layer is formed of an acrylic resin, and at least one of the innermost layer and the outer layer is made of a weather resistant layer in which an ultraviolet absorber is added to the resin.