JP4692142B2 - Electromagnetic shielding member and electromagnetic shielding case - Google Patents

Description

The present invention, black color appearance and corrosion resistance as well, relates to an electromagnetic wave shielding member and an electromagnetic wave shielding enclosure using the excellent black steel sheet electromagnetic shielding.

  Conventionally, black steel sheets with a blackened surface have been widely used in office equipment such as personal computers and copiers, home appliances such as air conditioners, automobile parts and interior building materials. Such black steel plates are usually coated with a black paint on the surface of a zinc-based plated steel plate or subjected to blackening treatment (for example, anodic electrolysis, cathodic electrolysis, alternating electrolysis, anodization) on the plated surface of a Zn-Ni plated steel plate. After that, it is manufactured by forming one or more coating layers. The reason for forming the coating layer in the latter method is that sufficient corrosion resistance cannot be obtained with the blackening treatment.

However, in the case of the former black steel plate, there is a problem in terms of electromagnetic wave shielding because it is necessary to increase the coating thickness in order to completely hide the base with the black paint.
On the other hand, in the case of the latter black steel plate, after forming the blackening treatment layer by blackening treatment, the organic and / or inorganic coating layer is formed, so that there is still a problem in that it is difficult to obtain sufficient electromagnetic shielding properties. It was.

  However, in the latter black steel plate, when forming a coating layer covering the blackening treatment layer, a coating composition to which metal ions, water-soluble organic resin, water-dispersible organic resin, glycoluril resin and acid are added is used. Thus, there has been proposed a method capable of reducing the thickness of the film to enhance the electromagnetic wave shielding property and obtaining an excellent black appearance and corrosion resistance while being a thin film (for example, Patent Document 1).

  In addition, in surface-treated steel sheets with organic and / or inorganic coatings, surface treatments with excellent electromagnetic shielding and corrosion resistance can be achieved by combining the centerline average roughness Ra and coating thickness of the surface after coating formation within an appropriate range. A method for obtaining a steel sheet has been proposed (for example, Patent Document 2).

JP 2004-188976 A JP 2004-156081 A

In recent years, in the field of electronic and electrical equipment, the problem of electromagnetic interference (EMI: Electric Magnetic Interference) has emerged, in which unnecessary electromagnetic waves leaking from equipment enter other equipment and cause some kind of malfunction or malfunction. In addition to equipment, there are concerns about the effects of electromagnetic waves on the human body.
One countermeasure is to surround the noise source with a metal plate (conductor). However, the casing surrounding the noise source has a joint or a joint, and electromagnetic waves leak from the gap. Therefore, when the surface-treated steel plate is used for the casing, sufficient electromagnetic wave shielding properties at the joints or joints are required. For this purpose, it is necessary to form a large number of contact conduction regions over the entire contact surface between the surface-treated steel plates that are in contact at the joints or joints.

Patent Document 1 proposes a black steel plate excellent in black appearance, corrosion resistance, and electromagnetic shielding properties. This is an electromagnetic wave shielding property improved by thinning the coating layer on the blackened Zn-Ni plated steel sheet.
However, since no consideration has been given to the surface roughness of the blackened Zn-Ni plated steel sheet, when the surface roughness changes, it is a case where a coating layer having the same adhesion amount is formed. However, there is a problem that the conductive region is difficult to be formed at the joint or the joint, or the number of the conductive regions is reduced, resulting in deterioration of the electromagnetic shielding property. Furthermore, since the thickness of the blackening treatment layer is not specified, there is a problem that the electromagnetic wave shielding property is deteriorated as the thickness is increased.

  Patent Document 2 proposes a method for providing a surface-treated steel sheet having excellent electromagnetic shielding properties and corrosion resistance by combining the center line average roughness Ra of the surface after coating layer formation and the film thickness within an appropriate range. ing. However, in this method, the unevenness of the steel sheet surface, in other words, the number of peaks per unit length PPI is not taken into consideration, so if the PPI is low, the number of conduction regions at the joint or joint is also reduced. There was a problem that sufficient electromagnetic shielding properties could not be obtained.

The present invention advantageously solves the above problem, effectively suppressing electromagnetic wave leakage at the joint or joint of the casing composed of the surface-treated steel sheet, to exhibit excellent electromagnetic shielding properties, the excellent black appearance, more electromagnetic wave shielding member with a black steel plate having excellent corrosion resistance, and further an object to provide an electromagnetic wave shielding enclosure formed by the black steel sheet as described above.

Now, as a result of intensive studies to solve the above problems, the inventors have conventionally defined the surface roughness of a Zn-Ni plated steel sheet having a blackening treatment layer for the purpose of improving electromagnetic shielding properties. In this case, a general roughness standard such as arithmetic average roughness Ra was applied, but in order to effectively improve the electromagnetic wave shielding property, a general roughness such as arithmetic average roughness was simply used. It was not enough to specify the surface roughness of the steel sheet as a standard, and we found that the number of peaks per unit length PPI is important. Moreover, the knowledge that the thickness of a blackening process layer also has influence on electromagnetic wave shielding property was acquired.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
( 1 ) An electromagnetic wave shielding member using a black steel plate having a coating layer on the surface of a Zn-Ni plated steel plate having a blackening treatment layer as a whole or a part of the member,
The thickness of the blackening treatment layer is 0.01 to 1.0 μm, and the surface roughness of the Zn-Ni plated steel sheet having the blackening treatment layer is 0.7 to 2.0 μm in terms of arithmetic average roughness Ra, and a peak per inch. The number PPI is 180 or more,
Further, when the arithmetic average roughness Ra is x (μm), the number of peaks PPI per inch is y, and the adhesion amount per one side of the coating layer is z (g / m ² ), these x, y, z is the following formula (1)
z ≦ (0.010x−0.0077) y−1.05x + 2.16 --- (1)
An electromagnetic shielding member characterized by satisfying the relationship:

( 2 ) An electromagnetic wave shielding housing in which a housing is formed using a black steel plate having a coating layer on the surface of a Zn-Ni plated steel plate having a blackening treatment layer ,
The thickness of the blackening treatment layer is 0.01 to 1.0 μm, and the surface roughness of the Zn-Ni plated steel sheet having the blackening treatment layer is 0.7 to 2.0 μm in terms of arithmetic average roughness Ra, and a peak per inch. The number PPI is 180 or more,
Further, when the arithmetic average roughness Ra is x (μm), the number of peaks PPI per inch is y, and the adhesion amount per one side of the coating layer is z (g / m ² ), these x, y, z is the following formula (1)
z ≦ (0.010x−0.0077) y−1.05x + 2.16 --- (1)
An electromagnetic shielding housing characterized by satisfying the above relationship .

According to the present invention, it is possible to effectively suppress electromagnetic wave leakage at the joints or joints of the casing made of the surface-treated steel sheet, to exhibit excellent electromagnetic shielding properties, and to have excellent black appearance and further corrosion resistance. A black steel plate can be provided.
Moreover, according to this invention, the electromagnetic wave shielding member excellent in electromagnetic wave shielding property can be provided by using said black steel plate for the whole or one part.
Furthermore, according to this invention, the electromagnetic wave shielding housing | casing excellent in electromagnetic wave shielding property can be provided by forming a housing | casing with said black steel plate.

Hereinafter, the present invention will be specifically described.
First, the reason why the thickness of the blackening treatment layer formed on the Zn—Ni plated steel sheet is limited to the range of 0.01 to 1.0 μm in the present invention will be described.
The blackening treatment layer formed on the Zn-Ni plated steel sheet is a layer formed by anodic oxidation, etc. and is not a good conductor, so if the layer thickness exceeds 1.0 μm, the coating layer is not formed. In addition, since the electromagnetic shielding properties at the joints or joints in the casing deteriorate, the thickness is set to 1.0 μm or less. On the other hand, if the thickness of the blackening treatment layer is less than 0.01 μm, a sufficient black appearance cannot be obtained.

Next, regarding the surface roughness of the blackened Zn—Ni plated steel sheet, the reason why the arithmetic average roughness Ra is 0.7 to 2.0 μm and the number of peaks PPI per inch is limited to 180 or more will be described.
The conventional blackened Zn—Ni plated steel sheet has Ra of about 0.5 to 1.5 μm, and the number of peaks PPI per inch is about 120 to 160.
In this invention, it was set as high Ra from a viewpoint that the coating layer on the Zn-Ni plating steel plate by which the blackening process was carried out thinly locally, and forms a conduction | electrical_connection area | region. When this Ra is less than 0.7 μm, the unevenness becomes small, and it becomes difficult to form a local thin film region when the coating layer is formed. For this reason, the surface roughness characteristics of the blackened Zn—Ni plated steel sheet were set to 0.7 μm or more in Ra.
On the other hand, when Ra exceeds 2.0 μm, although there is an effect on electromagnetic wave shielding properties, in order to cover the surface of the blackened Zn-Ni plated steel sheet with 100% coating layer and develop corrosion resistance, the coating layer It is necessary to increase the amount of adhesion, which increases the cost. For this reason, the surface roughness characteristics of the blackened Zn—Ni plated steel sheet were set to 2.0 μm or less in Ra.

Moreover, in this invention, it was set as high PPI from a viewpoint that many local thin film area | regions of the coating layer on the Zn-Ni plating steel plate blackened were formed over the whole surface. That is, when the number of peaks PPI per inch is less than 180, the number of local thin film regions is small, and it is difficult to obtain sufficient electromagnetic shielding properties. For this reason, PPI was 180 or more about the surface roughness characteristic of the Zn-Ni plating steel plate blackened. More preferably, PPI: 200 or more.
On the other hand, the upper limit of the PPI value is not particularly limited, but if the PPI exceeds 400, a large number of local thin film regions are formed, and there is a concern that the corrosion resistance may be lowered. For this reason, the PPI is preferably 400 or less.

Furthermore, the thickness of the Zn—Ni plating layer is preferably about 1 to 5 μm in order to ensure excellent corrosion resistance and plating adhesion.
And it is not necessary to make it the blackening process layer about the whole thickness of this Zn-Ni plating layer, and it should just be the blackening process layer over the thickness of 0.01-1.0 micrometer of a surface layer part as mentioned above.

The blackening treatment means is not particularly limited, and any of anodic electrolysis, cathodic electrolysis, alternating electrolysis, anodic oxidation, etc. in conventionally used treatment solutions is suitable.
In addition, as a method for controlling the thickness of the blackening treatment layer, a method of adjusting the treatment conditions such as the type, concentration and pH of the oxidizing agent in the treatment liquid, and the current density, electrolysis time, and electric density is effective.

Next, one or more coating layers are formed on the surface of the blackening treatment layer formed as described above. This is because sufficient corrosion resistance cannot be obtained with the surface after the blackening treatment.
As the coating layer, any coating layer that improves the corrosion resistance after the blackening treatment and does not impair the black appearance is suitable, but a coating layer composed of a chromate and an organic film, or organic and / or A coating layer composed of an inorganic coating is particularly advantageously adapted.

The coating amount of the coating layer is preferably 0.6 g / m ² or more in order to obtain sufficient corrosion resistance.

In addition, the upper limit value of the coating amount of the coating layer depends on the Ra and PPI sizes of the surface of the Zn-Ni plated steel sheet having the blackening treatment layer, but for example, when Ra = 2.0 μm and PPI = 180 In order to obtain excellent electromagnetic shielding properties, it is preferably about 2.3 g / m ² or less per side.
In addition, when Ra = 2.0 μm and PPI = 200, it is preferable to be about 2.5 g / m ² or less per side.
Further, when Ra = 2.0 μm and PPI = 400, it is preferable that the coating amount of the coating layer is about 5.0 g / m ² or less per side.

The preferred upper limit value of the coating amount of the coating layer described above is represented by the following general formula.
That is, when the arithmetic average roughness Ra is x (μm), the number of peaks PPI per inch is y, and the adhesion amount per one side of the coating layer is z (g / m ² ), x, y, z What is necessary is just to satisfy the relationship of following Formula (1).
z ≦ (0.010x−0.0077) y−1.05x + 2.16 --- (1)
Here, when the adhesion amount z satisfies the relationship of the above formula (1), it is the adhesion amount of the coating layer suitable for Ra and PPI of the plated steel sheet from the viewpoint of securing the conduction point, and is particularly excellent. Electromagnetic shielding properties can be obtained.

By the way, according to the above equation (1), the relationship between PPI (y) and the coating amount z (g / m ² ) of the coating layer when Ra (x) is 2.0 μm and PPI (y) is 200-400. This is shown in FIG.

Next, an electromagnetic wave shielding member using the above-described black steel plate and an electromagnetic wave shielding case formed of the above black steel plate will be described.
In the case of using a surface-treated steel sheet, the electromagnetic shielding property is particularly problematic in the overlapping portion of the surface-treated steel sheet. Therefore, if the black steel plate of the present invention is applied at least in the overlapping portion, excellent electromagnetic shielding properties can be obtained. This is an electromagnetic wave shielding member using the black steel plate of the present invention as a whole or a part of the member.
In addition, if the entire casing is made of the black steel plate of the present invention, not only the overlapping portion, particularly excellent electromagnetic shielding properties can be obtained. This is an electromagnetic wave shielding casing in which the entire casing is formed of the black steel plate of the present invention.

  As a method for controlling the surface roughness characteristics of the Zn-Ni plated steel sheet after the blackening treatment of the present invention, a method for adjusting the surface roughness of a cold-rolled steel sheet used as an original sheet, a steel sheet after Zn-Ni plating A method for adjusting the surface roughness of the steel sheet, a method for adjusting the surface roughness of the steel sheet after the blackening treatment, and the like can be used. As a method of adjusting the surface roughness of the cold-rolled steel sheet used as the original sheet, the roll of tandem rolling or temper rolling of the original sheet is subjected to dull processing by blasting method, electric discharge processing method, laser processing method, etching method or other surface processing methods. A tandem rolling or temper rolling method or the like can be used as the roll subjected to. Moreover, the method of processing an original plate with a direct blast processing method can also be used.

  That is, when the Zn—Ni plating layer of the present invention is manufactured by the electroplating method, the plating layer is formed on the steel plate surface so as to substantially follow the unevenness of the steel plate surface. Further, when the blackening treatment is performed by electrolytic treatment such as anodization, the blackening treatment layer is formed on the steel plate surface so as to substantially follow the unevenness of the steel plate surface. Therefore, it is preferable to adjust the surface roughness of the Zn-Ni plated steel sheet after the blackening treatment by a method of controlling the roughness of the steel sheet before forming these layers.

Moreover, as a method of adjusting the surface roughness of the steel plate after Zn-Ni plating and blackening treatment, a method of temper rolling using a temper rolling roll with adjusted roughness can be used.
In this case, the roughness pattern of the temper rolling roll is not transferred to the steel plate as it is 100% even after temper rolling, and the Ra value is transferred to the steel plate side as a value of about 40 to 50% of the value of the roll surface. The PPI value is transferred to the steel sheet as a value around 80% of the roll surface value. Therefore, in order to obtain a blackened Zn-Ni plated steel sheet having a surface roughness characteristic in which the arithmetic average roughness Ra is 0.7 to 2.0 μm and the number of ridges PPI per inch is 180 or more, a temper rolling roll It is preferable that Ra has a surface roughness of 1.4 to 5.0 μm and a PPI of 220 or more.

The electromagnetic wave shielding property of the present invention is evaluated by measuring leakage noise using an apparatus as shown in FIG.
Thickness: A 20 MHz clock 4 is placed as a transmission source in an aluminum casing 3 having an outer diameter of 100 mm × 100 mm × 100 mm made of a 2 mm aluminum plate. The upper surface of the aluminum housing 3 has an opening of 80 mm × 80 mm, a 10 mm edge 5 is projected inside, and a 10 mm × 1 mm gasket (urethane sponge is coated with conductive cloth (copper and nickel plated). 1) 6 is installed. The specimen 1 is cut out to 100 mm × 100 mm and brought into contact with the gasket 6 installed on the upper surface of the aluminum housing 3 with the evaluation surface 2 as the lower surface. A load of 19.6 N (2 kgf) is applied to the specimen 1 in the vertical direction. In this way, electromagnetic waves leaking from the frame-shaped mating surface where the gasket 6 and the specimen 1 are in contact are received by the loop antenna 7 with a diameter of 30 mm at a position 50 mm away from the edge 5 and 25 dB. After amplification with the preamplifier 8, analysis is performed using a spectrum analyzer (R3162 manufactured by Advantest Corporation) 9.

Further, the electromagnetic shielding properties when the present invention was used as a housing material were evaluated by producing a housing as shown in FIG.
A commercially available ATX tower type PC case (Owltech OWL-PCR7) was diverted, and the outer shell portion 10 and the lid 11 of the casing were made of test materials. In the above case, a desktop personal computer was prepared by incorporating parts having the following specifications, and Windows (registered trademark) XP was installed and started as an OS.
Power supply: Use case accessories as it is Motherboard: AX4SG MaxII made by A-Open
CPU: Intel Pentium (registered trademark) 4 processor 3GHz
DDR memory: Unbranded 250MB x 2
HDD: Hitachi IBM Corporation: HDS722516VLAT80 (capacity 160GB)
Optical drive: Pioneer DVR-A08-J

Example 1
The specimens shown in Table 1 as Nos. 1 to 13 were annealed cold-rolled steel sheet → temper rolled (surface roughness adjustment) → electric Zn-Ni plating → anodic electrolysis (blackening treatment) → coating layer formation, or Annealed cold-rolled steel sheet → Blasting (surface roughness adjustment) → Electrical Zn-Ni plating → Anodization (blackening treatment) → Covering layer formation thickness, blackening treatment layer thickness, Ra after blackening treatment, Manufactured with various changes in the amount of PPI and coating layer. The thickness of the Zn—Ni plating layer formed by the electric Zn—Ni plating treatment was 2 μm. The thickness of the blackening treatment layer was adjusted by changing the electrolysis time and pH of the anodizing treatment.
The coating layer has a final plate temperature of 190 ° C. after 21 seconds after a coating composition to which metal ions, water-soluble organic resin, water-dispersible organic resin, glycoluril resin and acid are added is applied with a bar coater. As described above, it was heated in an oven, dried and cured to obtain a predetermined adhesion amount.
Table 1 shows the results of examining the surface roughness characteristics, the thickness of the blackening treatment layer, the coating layer adhesion amount, the flat surface corrosion resistance, the black appearance, and the electromagnetic wave shielding property of each specimen thus obtained.

The evaluation method of each characteristic is as follows.
<Surface roughness characteristics>
For the test material after the blackening treatment, a stylus type roughness meter (manufactured by Tokyo Seimitsu Co., Ltd.) having a radius of curvature of the tip of the stylus of 1 μm was used, and the scanning speed was 0.3 mm / s. The arithmetic average roughness Ra specified in 1994 was measured as a cut-off value: 0.8 mm, and the number of peaks PPI per inch was measured as the number of peaks exceeding 0.635 μm.

<Thickness of blackening treatment layer>
The cross section of the test material after the blackening treatment was observed with a transmission electron microscope, the thickness of the blackening treatment layer at the center of the visual field was measured at a magnification of 90,000 times, and the average value of the four visual fields was obtained.

<Coating layer adhesion amount>
The change in the mass of the test material before and after the formation of the coating layer was calculated in terms of a unit area.
<Flat plate corrosion resistance>
After shearing the specimen after forming the coating layer to a size of 50 mm x 100 mm, sealing the end face, and conducting a salt spray test in accordance with the neutral salt spray test (JIS Z 2371-2000) for 48 hours The white rust generation area ratio was measured and evaluated according to the following criteria.
◎: 5% or less ○: Over 5% 10% or less △: Over 10% 20% or less ×: Over 20%

<Black appearance>
The color tone (L * value) of the test material after the coating layer was formed was measured using a spectroscopic color difference meter (SQ2000, manufactured by Nippon Denshoku Co., Ltd.) and evaluated according to the following criteria.
○: L * value is 25 or less ×: L * value is more than 25

<Electromagnetic wave shielding>
The electromagnetic wave shielding property was measured by using a spectrum analyzer to measure leakage noise from the joint portion between the evaluation surface of the test material and the housing using the apparatus shown in FIG. 2, and charts as shown in FIGS.
In the evaluation of the inventive example and the comparative example, the peak value was read every 20 MHz from the frequency 20 MHz to 1000 MHz, and the value converted by the following formula (2) was defined as the noise evaluation value (I).
I = 10 × log (10 ^0.1d1 +10 ^0.1d2 + ... + 10 ^0.1dn ) --- (2)
n: number of peaks
d1, d2, ... dn: Peak value As an evaluation standard, a Zn-Ni plated steel sheet (reference example) that does not have a coating layer and is considered to have excellent electromagnetic shielding properties at the joint or joint of the casing was used as a test material. FIG. 4 shows a measurement example in this case, and FIG. 5 shows a measurement example of Invention Example 7. Moreover, the example measured in the state without a test material is shown in FIG. 6, and the example measured in the state without a test material without transmitting and outputting a high frequency is shown in FIG. FIG. 7 shows external noise. Here, the peak value read from FIGS. 4 to 7 was substituted into the above equation (2), and the calculation result was I. In addition, since the peak of the place which attached | subjected x in FIGS. 4-7 originates in the external noise shown in FIG. 7, it was excluded from the object of above-mentioned Formula (2).
For the sample materials of the inventive examples, the noise evaluation value obtained by measuring the leakage noise is I, the noise evaluation value obtained from FIG. 6 (no sample material, with high frequency output) is Ia, and FIG. When the noise evaluation value obtained from no material and no high frequency output is Ib,
(I−Ib) / (Ia−Ib)> 0.35 ×
0.35 ≧ (I−Ib) / (Ia−Ib)> 0.26 is Δ,
0.26 ≧ (I−Ib) / (Ia−Ib)> 0.20
The 0.20 ≧ (I-Ib) / (Ia-Ib)> 0.13 ○ +,
0.13 ≧ (I−Ib) / (Ia−Ib) ≧ 0
It was evaluated with.

As is apparent from Table 1, according to the present invention, the thickness of the blackening treatment layer is 0.01 to 1.0 μm, the arithmetic average roughness Ra after blackening treatment is 0.7 to 2.0 μm, and the number of peaks PPI per inch is 180. All of the above-mentioned adjustments not only have a good black appearance and corrosion resistance, but also have good electromagnetic shielding properties.
Especially when the arithmetic average roughness Ra (x), the number of peaks per inch PPI (y), and the coating layer adhesion amount (z) satisfy the relationship of the above formula (1), the electromagnetic wave is particularly excellent. Shielding properties are obtained.

Example 2
Various test materials (No.5, No.6, No.8, No.11, No.13) shown in Table 1 are applied to the outer shell 10 and the lid 11 of the tower type PC case shown in FIG. Table 2 shows the results of the investigation on the electromagnetic wave shielding properties in the case of the above.
In addition, the evaluation method of the electromagnetic wave shielding property of a tower type PC case is as follows.
<Electromagnetic shielding properties of electronic and electrical equipment products>
The electromagnetic shielding properties of electronic and electrical equipment products that have been made from the test material are based on the technical standards V-3 / 2005.04, 4.3 of interference signal electric field strength of VCCI The measurement distance shown in Note 2 in Table 4.6 of the allowable value was set to 3 m, measured at an open site, and whether or not the class B was satisfied was determined.
○: Satisfied with class B ×: Not satisfied with class B

  As shown in Table 2, when the black steel plate according to the present invention is used for both the outer shell and the lid of the housing (housing Nos. 1 to 3), sufficiently satisfactory electromagnetic shielding properties are obtained as the housing. I was able to.

It is a figure which shows the suitable range of PPI (y) and the adhesion amount z (g / m < ² >) of a coating layer in case Ra (x) is 2.0 micrometers and PPI (y) is 200-400. It is a schematic diagram of the leakage noise measuring device for evaluating electromagnetic shielding properties. It is a schematic diagram of the housing | casing for evaluating electromagnetic wave shielding property. It is a chart which shows the relationship between the electric field strength and frequency of leakage noise at the time of using the Zn-Ni plated steel plate (reference example) which does not have a coating layer as a test material. It is a chart which shows the relationship between the electric field strength of the leakage noise at the time of using Example 7 as a test material, and a frequency. It is a chart which shows the relationship between the electric field strength and frequency of the leakage noise at the time of measuring in an opening state, without mounting a test material on the aluminum housing | casing of the apparatus shown in FIG. FIG. 2 is a chart showing the relationship between the electric field strength of leakage noise and the frequency when external noise is measured without placing a test material on the aluminum housing of the apparatus shown in FIG. It is.

Explanation of symbols

1 Test Material 2 Evaluation Surface 3 Aluminum Case 4 20 MHz Clock 5 Edge 6 Gasket 7 Loop Antenna 8 Preamplifier 9 Spectrum Analyzer
10 Enclosure of the housing
11 Housing lid

Claims (2)

On the surface of the Zn-Ni plated steel sheet having a blackening treatment layer, an electromagnetic shielding member using a black steel sheet having a coating layer as a whole or a part of the member,
The thickness of the blackening treatment layer is 0.01 to 1.0 μm, and the surface roughness of the Zn-Ni plated steel sheet having the blackening treatment layer is 0.7 to 2.0 μm in terms of arithmetic average roughness Ra, and a peak per inch. The number PPI is 180 or more,
Further, when the arithmetic average roughness Ra is x (μm), the number of peaks PPI per inch is y, and the adhesion amount per one side of the coating layer is z (g / m ² ), these x, y, z is the following formula (1)
z ≦ (0.010x−0.0077) y−1.05x + 2.16 --- (1)
An electromagnetic shielding member characterized by satisfying the relationship: On the surface of a Zn-Ni plated steel sheet having a blackening treatment layer, an electromagnetic wave shielding casing in which a casing is formed using a black steel sheet having a coating layer ,
The thickness of the blackening treatment layer is 0.01 to 1.0 μm, and the surface roughness of the Zn-Ni plated steel sheet having the blackening treatment layer is 0.7 to 2.0 μm in terms of arithmetic average roughness Ra, and a peak per inch. The number PPI is 180 or more,
Further, when the arithmetic average roughness Ra is x (μm), the number of peaks PPI per inch is y, and the adhesion amount per one side of the coating layer is z (g / m ² ), these x, y, z is the following formula (1)
z ≦ (0.010x−0.0077) y−1.05x + 2.16 --- (1)
An electromagnetic shielding housing characterized by satisfying the above relationship .

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