JPH1016128A - Surface treated metal plate of superior resistance to fingerprint and grounding properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treated metal plate of superior resistance to fingerprint and grounding properties in which the coverage rate of a film is controlled by controlling the surface roughness of the metal plate or a plated metal plate and the film thickness of an organic composite film coating a topmost layer. SOLUTION: A chromate film is provided on a metal plate or a plated metal plate, over which an organic composite film of film coverage rate of 70-99% is formed. When the surface roughness of the metal plate or the plated metal plate is set as the centerline average roughness Ra(μm) regulated by JIS-B0601 and the film thickness of the organic composite film coating the topmost layer is set as t(μm), the value α (film coating index) represented by the formula of α=57.4-24.6×Ra+101.6×t is 70-99.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated metal plate which is excellent in fingerprint resistance, corrosion resistance, processing galling and grounding properties, and is used for home electric appliances, especially for electronic parts and the like which require grounding properties. About.

[0002]

2. Description of the Related Art Heretofore, surface-treated metal sheets for home appliances include:
Various product performances such as fingerprint resistance, corrosion resistance, and processing galling have been required. Various studies have been made to satisfy these performances, and many products have been developed. Among them, a surface-treated metal plate in which a chromate treatment is performed on a plated metal plate and an organic composite film based on a special resin is formed thereon is being developed, and at present, the most effective metal satisfying the above-described performances has been developed. As a board, it has become mainstream as a component for home appliances. For example, Japanese Patent Publication No. 4-14191 discloses an organic coating film in which a colloidal sol having a specific fine particle size is additionally adjusted in an aqueous organic resin on a chromate-coated plated steel plate to improve corrosion resistance and fingerprint resistance. There is disclosed a method for producing a surface-treated steel sheet having the following.
Japanese Patent Application Laid-Open No. 5-65666 discloses a method for producing a plated steel sheet to which a paint containing a wax and a lubricant is applied for the purpose of improving workability.

[0003]

In recent years, with the increase in demand for computer-related equipment worldwide, new characteristics are required for the surface-treated metal plate itself. The requirement is an electromagnetic wave shielding property which is indispensable for electronic parts and the like, and a high grounding property is required for the metal plate itself in order to satisfy this performance. It is an effective means to add a high grounding property to a high performance coated metal plate that has been conventionally developed, by making the organic film into a thin film. However, simply reducing the film thickness will cause unevenness in the coating film, which will ensure grounding properties, but will degrade the inherent performance of painted metal plates such as fingerprint resistance, processing galling, and corrosion resistance. There was a problem of doing.

[0004]

Means for Solving the Problems In order to solve such problems, the inventor of the present invention has conducted intensive studies and found that by controlling the center line average roughness of the metal plate and the plated metal plate and the thickness of the coating film. We found that adding a good grounding property while controlling the coating film area ratio and securing various performances of the coated metal plate. That is, the former is characterized in that a chromate film is formed on a metal plate or a plated metal plate, and an organic composite film is formed on the chromate film so as to have a coating film coverage of 70 to 99%. It is a surface-treated metal plate that has excellent fingerprint and grounding properties. Further, in the latter, the surface roughness of the metal plate or the plated metal plate is defined as the center line average roughness Ra (μm) specified in JIS-B0601, and the thickness of the organic composite film covering the outermost layer is defined as t. (Μm), a value (coating film coating index) α expressed by the following formula is 70 to 99.
Wherein the surface-treated metal plate is excellent in fingerprint resistance and arc resistance. α = 57.4-24.6 × Ra + 101.6 × t

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows a cross section of a surface-treated metal plate having a plating according to the present invention. From the lower layer, metal plate 1, plating 2, chromate 3, and organic composite film 4
It consists of. Hereinafter, each film will be described. The metal plate targeted by the present invention includes iron, iron-based alloy, aluminum, aluminum-based alloy, copper, and copper-based alloy. In addition, the plated metal plate is a galvanized metal plate, a zinc alloy plated metal plate manufactured by electroplating, hot dipping, vapor deposition plating,
It includes a dispersion-plated metal plate, a lap-plated metal plate, and an aluminum alloy-plated metal plate. The amount of plating does not need to be particularly limited, but when corrosion resistance is considered, 5 mg
/ M ² or more is desirable.

[0006] After plating on the metal plate and on the metal plate by the above-mentioned existing method, a chromate treatment is performed. There is no particular limitation on the amount of chromate adhering, but 5 mg / m ²
Below, the corrosion resistance is inferior, and when it is 100 mg / m ² or more, the coating film adhesion is inferior.
100 mg / m ² is desirable. Regarding the type of chromate treatment, any of electrolytic chromate, etching chromate, and coating chromate can be applied to the present invention.

[0007] As the resin component in the organic composite film,
It is not necessary to limit, but acrylic resin, acrylic ethyl
Resin, urethane resin, epoxy resin, polyester tree
Fat, phenolic resin, polycarbonate resin, polyole
One of fin-eye monomers and melamine resin
Or a mixture of two or more. Ko
Acrylic resin when the strike surface is important, top coatability is important
If you want to focus on epoxy, polyester resin, workability
If so, a urethane resin is optimal. As a pigment,
Although it is not necessary to particularly limit, SiO 2_Two, Cr_TwoO_Three, F
e_TwoO_Three, Fe _ThreeO_Four, MgO, ZrO_Two, SnO_Two,
Al_Two O_Three, Sb_TwoO_FiveOne or two or more
Can be used. Especially SiO_TwoIs economical
It is advantageous and optimal. The coating film formation method is
, Spray coat, curtain flow coat, etc.
These methods may be used.

[0008] The coated area ratio of a metal plate coated with an organic composite film is CMA (Computer Aided).
X-ray Micro Analyzer (manufactured by JEOL Ltd.). CMA analysis conditions were as follows: analysis diameter 2 μm, irradiation current 0.05 μA, irradiation time 30 ms.
c, Analysis of 250,000 points (1 mm square) of 500 points by 500 points at an acceleration voltage of 15 kA, and measurement of the detection intensity of elements contained in the coating film at each analysis point is performed.
However, the measurement element for obtaining the coating film coverage ratio is, for accuracy,
A sensitive heavy element is desirable. When the average strength of 250,000 points of a coated metal plate having an average coating film thickness of 1 μm is determined, a value of 1/10 is set as a threshold value, and the number of points indicating a detection intensity of more than that is N, The coating film coverage area ratio (%) can be determined by the following formula. Coating area ratio (%) = (N / 250,000) × 100

[0009] The coating film coverage ratio tends to increase as the center line average roughness Ra of the metal plate or plated metal plate becomes smaller and as the film thickness t of the organic composite film covering the outermost layer becomes thicker. Therefore, a coating film coating index α, which is an index of the coating film coating degree, was expressed as a mathematical expression using Ra and t as follows. Coating index α = 57.4-24.6 × Ra + 101.
6 × t Next, FIG. 2 shows the relationship between the coating film coverage area ratio and the coating coverage index. In a region where the coating film coverage ratio is 100% or less, a straight line in direct proportion is obtained, and the coating film coverage index has a very linear relationship with the coating film coverage ratio. Therefore, the coating film covering area ratio can be replaced with the coating film covering index, and the coating film covering area ratio can be represented by Ra and t.

In order to secure fingerprint resistance, it is desirable that the coating film coverage area ratio be 70% or more. If it is smaller than 70%, fingerprint marks are conspicuous when the painted metal plate is directly touched with a hand, and the appearance is impaired. Conversely, in order to ensure grounding properties, it is desirable that the coating film coverage area ratio be 99% or less. If it exceeds 99%, the grounding property is reduced, and a sufficient electromagnetic wave shielding property cannot be obtained. In other words, a high grounding property and fingerprint resistance can be ensured when the coating film coverage index represented by Ra of the metal plate or plated metal plate and the film thickness t of the organic composite film coating the outermost layer is 70 to 99. It is when it is in the range.

[0011]

Next, examples of the present invention will be described. Table 1 summarizes the configuration of the coated metal plate used in this example. The three types of metal plates, iron, aluminum, and stainless steel, are used to control the roughness of the rolling roll during the cold rolling process, so that Ra is 0.4, 0.6, 0.8, 1..
It was made of an iron plate having a thickness of 0, 1.2, 1.5, or 1.8 μm, an aluminum plate having a Ra of 0.8 μm, or stainless steel.
As shown in Table 1, the plating is electrogalvanized (EG),
Electro-Zn-Ni alloy plating (ZL), hot-dip galvanizing (GI) with Ni content of 12% by weight, alloyed hot-dip galvanizing (AS) with Fe content of 10.5% by weight Table 1 It was applied to a specified amount and a specified iron plate.

In the chromate treatment, electrolytic chromate which has been subjected to electrolytic treatment using a commercially available sulfuric acid-based treatment solution containing mainly chromic acid, and reaction chromate which has been subjected to etching treatment by mixing nitric acid as a reducing agent into commercially available chromic acid. A commercially available treatment mixture containing chromic acid and silica was applied and baked for use. The coating film was made of a commercially available acrylic resin, polyester resin, or epoxy resin and mixed with silica sol, and baked at 120 ° C. after the bar coating. At each level, the coating film covering area ratio was calculated from the CMA analysis results of Si in the coating film, and the fingerprint resistance, grounding property, corrosion resistance, and galling property were evaluated. The results were shown in Tables 2 to 4. Summarized in

[0013]

[Table 1]

[0014] Fingerprint resistance was evaluated by pressing a real finger against each painted metal plate for 3 seconds and rating the degree of conspicuousness of the fingerprint marks. The following indicators were used for scoring. Fingerprint traces are completely unknown: Score 5 Fingerprint traces are hardly understood: Score 4 Fingerprint traces are clearly observed by observing: Score 3 Fingerprint traces are somewhat noticeable: Score 2 Fingerprint traces are very noticeable: Score 1 For practical application of fingerprint resistance, a rating of 3 or more is required. The earthing property is measured by a measuring method defined in JIS-C2550 of each coated metal plate, and an interlayer resistance value (Ω · cm ² )
Was measured. For practical application, the interlayer resistance value is 2.5
It is necessary to keep Ω · cm ² or less.

The corrosion resistance was evaluated by measuring the area ratio of white rust and red rust after 168 hours of flat salt spray corrosion test, and evaluated according to the following criteria. No rust generation: ◎ Rust generation area ratio less than 5%: 〇 Rust generation area ratio less than 20%: △ Rust generation area ratio 20% or more: × ◎ or 必要 is required for practical use.

[0016] The galling property is L bending clamp press 90
% Bending, a bending radius of 5 mm, and press with no oil coating, and the appearance was evaluated by observation after press. The evaluation was performed according to the following criteria. No flaws in the pressed part: ◎ Minor flaws in the pressed part: 多 い Many flaws in the pressed part: △ Significant flaws in the pressed part: × ◎ for practical application is required.

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

No. Nos. 1 to 5 are comparative examples in which Ra is varied from 0.4 to 1.2 μm at a film thickness of 0.1 μm. However, it is inferior in fingerprint resistance, corrosion resistance, and processing galling. N
o. 6 to 7 have a film thickness of 0.3 μm and Ra of 0.4 to 0.6.
In the example of the present invention shaken to μm, the coating film coverage area ratio is 70 to 99.
%, Excellent performance in both grounding property and fingerprint resistance. No. Nos. 8 to 12 are comparative examples in which the film thickness was 0.3 μm and Ra was varied from 0.8 to 1.8 μm, and the coating film coverage area ratio was 70% or less, and the grounding property was excellent, but the fingerprint resistance was high. Inferior. In particular, when Ra is 1.2 μm or more, the corrosion resistance is poor.

No. 13 to 17 have a film thickness of 0.4 μm and Ra
Was varied to 0.4 to 1.2 μm, the coating film coverage was included in 70 to 99%, and both the grounding property and the fingerprint resistance exhibited excellent performance. No. Nos. 18 to 19 are comparative examples in which the film thickness is 0.4 [mu] m and Ra is varied from 1.5 to 1.8 [mu] m. , Poor corrosion resistance. No. 20-2
No. 5 is an example of the present invention in which Ra is varied to 0.4 to 1.5 μm at a film thickness of 0.5 μm, and the coating film coverage area ratio is included in 70 to 99%, and both grounding property and fingerprint resistance are excellent. Performance. No. Reference numeral 26 denotes a comparative example in which the film thickness was 0.5 μm and Ra was 1.8 μm. The coating film coverage area ratio was 70% or less, which was excellent in grounding property but poor in fingerprint resistance.

No. 27 to 31 have a film thickness of 0.6 μm and R
In the examples of the present invention in which a was varied from 0.8 to 1.8 μm, the coating film covering area ratio was included in 70 to 99%, and both the grounding property and the fingerprint resistance exhibited excellent performance. No. 32 to 33 are comparative examples in which the film thickness is 0.7 μm and Ra is varied from 0.8 to 1.0 μm, all of which have a coating film coverage of 100%, and are excellent in fingerprint resistance and corrosion resistance. Poor grounding. No. 3
Nos. 4 to 36 have a film thickness of 0.7 μm and Ra of 1.2 to 1.8 μm.
m, the coating film covering area ratio is 70 to 99%.
And exhibited excellent performance in both grounding property and fingerprint resistance. No. 37 to 41 are comparative examples in which Ra is varied from 0.8 to 1.8 μm at a film thickness of 1.0 μm, and all have a coating film coverage of 100%, and are excellent in fingerprint resistance and corrosion resistance. Poor grounding.

No. 42 to 46 have a film thickness of 3.0 μm and R
Comparative Examples in which a was varied from 0.8 to 1.8 μm, all of which had a coating film coverage of 100% and were excellent in fingerprint resistance, corrosion resistance, and galling, but were poor in grounding properties. No. 47
-56 and 59 have a film thickness of 0.4 μm and Ra of 0.8 μm,
In the examples of the present invention in which the type of the coating original plate or the coating film was changed, regardless of the type of the original plate and the type of coating film, all exhibited excellent grounding properties and fingerprint resistance. In particular, no. Nos. 53 to 55 were very excellent in corrosion resistance. In addition, No. In the level using AS for the 56 plated steel sheets, the coating film covering area ratio was slightly lower than that of the other original coated sheets. No. 57 is a comparative example in which an unplated iron plate was used as a coating base plate having a thickness of 0.4 μm and Ra of 0.8 μm, and showed excellent performance in both grounding property and fingerprint resistance, but was inferior in corrosion resistance.

No. Reference numeral 58 denotes a film thickness of 0.4 μm, Ra0.
In a comparative example in which an aluminum plate was used as the 8 µm coating original plate, both the grounding property and the fingerprint resistance were excellent, but the processing galling was inferior. No. 60 to 72 have a film thickness of 0.1 μm,
Ra 0.8 μm, a comparative example in which the coating original plate or the coating type was changed. The film thickness was small and the coating film covering area ratio was low, so the grounding properties were very good, but the fingerprint resistance, corrosion resistance, and processing were excellent. Poor galling. In addition, No. As for the level using AS for the 69 plated steel sheets, the coating film covering area ratio was slightly lower than that of other coated original sheets. No. Reference numerals 73 to 85 are comparative examples in which the coating original plate or the coating film type was changed with a film thickness of 0.7 μm and Ra of 0.8 μm.
0%, which is excellent in fingerprint resistance, but poor in grounding properties. In particular, no. Reference numeral 83 is a comparative example in which an unplated iron plate was used as a coating base plate, and was inferior in corrosion resistance.

In order to satisfy the fingerprint resistance of home electric appliances, a score of 3 or more is required.
% Is satisfied by the coated metal plate. For use as a metal plate for electronic components, an interlayer resistance of 2.5 Ω · cm ²
It is necessary to keep it below.
% Is satisfied by the coated metal plate. Corrosion resistance is iron plate <aluminum plate <stainless steel, no plating <AS <EG <G
Although a tendency such as I <ZL, electrolytic chromate = reaction chromate <coating chromate was observed, good performance was obtained at a level other than the absence of iron plate plating within the range of the coating film coverage of claim 1. Was. Machinability is ZL for original plate type
Showed a good tendency, and on the contrary, there was a tendency that aluminum was easy to bite. Other coating original plates showed good performance when the coating film coverage ratio was within the range of the coating film coverage ratio of claim 1, while slightly poorer tendency was observed in a region where the coating film coverage ratio was low.

[0026]

From the above results, it can be seen that an organic composite film is formed on a metal plate or a plated metal plate so that a chromate film is formed thereon and the coating film coverage is 70 to 99%. The characteristic surface-treated metal plate having excellent fingerprint resistance and grounding properties has both fingerprint resistance and grounding properties.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a film of a surface-treated metal plate when there is plating of the present invention.

FIG. 2 is a diagram showing a relationship between a coating film coverage area ratio (%) and a coating film coating index.

[Explanation of symbols]

 1 Metal plate 2 Plating 3 Chromate 4 Organic coating

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hidehito Goto 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Works (72) Inventor Katsutoshi Enyama 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Kimitsu Works, Ltd.

Claims (2)

[Claims] A chromate film is formed on a metal plate or a plated metal plate, and the upper layer has a coating film coverage of 70 to 99%.
%. A surface-treated metal plate having an excellent fingerprint resistance and grounding property, wherein an organic composite film is formed so as to be 0.1% by weight. 2. The surface roughness of a metal plate or a plated metal plate is determined by a center line average roughness R defined in JIS-B0601.
a (μm), and when the thickness of the organic composite film covering the outermost layer is t (μm), a value (coating coating index) α expressed by the following formula is 70 to 99, The surface-treated metal plate according to claim 1, which is excellent in fingerprint resistance and grounding properties. α = 57.4-24.6 × Ra + 101.6 × t