JP2009299186A - Surface treated metal sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treated metal sheet which can be suitably used for the enclosure of an electronic device, and is excellent in electromagnetic wave shieldability in the joint part. <P>SOLUTION: The surface treated metal sheet has on one or both surfaces thereof a film containing granular nickel. When the average film thickness of the film is defined as t (μm), the grain size of the nickel is defined as R<SB>Ni</SB>and the distribution width of a 20% frequency level when the height of the peaks of the number-size distribution of the nickel is 100% is defined as W<SB>20</SB>(μm), the surface treated metal sheet satisfies conditions wherein: the peaks of the number-size distribution are present at least in the range of 1<[R<SB>Ni</SB>/t]≤2; the W<SB>20</SB>of the peaks of the number-size distribution is ≤5; the peaks of the number-size distribution are not present in the range of 2<[R<SB>Ni</SB>/t]; and the number of the nickel present in the range of 2<[R<SB>Ni</SB>/t] is <5×10<SP>9</SP>per m<SP>2</SP>. By this constitution, the surface treated metal sheet has excellent electromagnetic wave shieldability in the joint part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface-treated metal plate that can be suitably used for a housing of an electronic device and has excellent electromagnetic shielding properties at a joint, and an electronic device housing manufactured using at least a part of the metal plate.

  Electromagnetic waves have been used for broadcasting, radar, ship communication, microwave ovens, etc. for some time, but in recent years, their use has expanded dramatically due to remarkable developments in information and communication technology. Among them, the use of the GHz band that enables transmission of large-capacity information has increased rapidly, and cellular phones (1.5 GHz), ETC (5.8 GHz), satellite broadcasting (12 GHz), wireless LAN (2.45 to 60.0 GHz) ), And in-vehicle rear-end collision prevention radar (76 GHz). On the other hand, in addition to conventional cable wiring, in general homes, the arrival of a ubiquitous society in which personal computers, televisions, and various information appliances are networked by wireless communication using microwaves and millimeter waves and are always connected to computers.

  In this way, a large number of electromagnetic wave generation sources surround us, and coupled with the reduction in size, speed, and thinning of communication devices, the radiation of unwanted electromagnetic waves and the resulting risk of malfunction are considered to have increased significantly. It is done.

  There is an electromagnetic wave shielding technique using a metal material as means for suppressing unnecessary electromagnetic wave emission (Emission) or making it difficult to malfunction even when receiving unnecessary electromagnetic wave radiation (Immunity). Non-patent document 1 describes that a metal material is suitable as an electromagnetic shielding material. The electromagnetic wave shield described in the present invention is an “electromagnetic shield” referred to in Non-Patent Document 1, and should be distinguished from an “electrostatic shield” and a “magnetic shield”. That is, an effect of preventing electromagnetic waves having a frequency of about 1 MHz or more from leaking through the material. In this sense, the metal material has an electromagnetic wave shielding effect that is significantly superior to, for example, plastic. By surrounding the generation source of the unnecessary electromagnetic wave with the metal plate, the emission is suppressed, and by surrounding the electronic circuit with the metal plate, it becomes an immunity means for protecting the circuit from unnecessary radiation from the outside. Therefore, if an electronic device casing having no gaps or joints can be created with a metal plate, a good electromagnetic wave shield can be obtained, and electromagnetic wave leakage hardly causes a problem.

  However, the electronic device casing has some joints by screwing, spot welding, helix folding, or the like. The surface of the metal plate may be coated with a coating containing an organic resin for the purpose of imparting corrosion resistance and fingerprint resistance. In such a case, electromagnetic waves may leak from the joint, and the electromagnetic shielding properties of the housing are determined by the amount of leakage from the joint.

  As the characteristics of the material, it is believed that the better the conductivity, especially the surface conductivity, the better the electromagnetic shielding properties. So far, many techniques for increasing the surface conductivity of materials have been disclosed for the purpose of electromagnetic shielding. Yes.

  For example, Patent Document 1 and Patent Document 2 disclose a method of forming an organic film on a base steel sheet having a large center line average roughness Ra, that is, having unevenness. This is to make the distribution of the film thickness non-uniform and to ensure conductivity at the non-covered part (convex part). However, in this method, in order to provide good electromagnetic wave shielding properties, it is necessary to make the film thickness very thin, so the performance to be imparted by forming an organic coating (for example, corrosion resistance, fingerprint resistance) Slidability, heat dissipation, etc.) were difficult to obtain.

  Moreover, as a method of incorporating a conductive substance into the organic film, methods described in Patent Documents 3 and 4 are disclosed.

  Patent Document 3 discloses a method in which flaky nickel and chain nickel are contained in a film. This is because the flake nickel is oriented in the film so that the surface of the flake nickel and the film surface are parallel, and the chain nickel is oriented in the direction perpendicular to the film surface so as to connect the flake nickel. Therefore, it is possible to conduct efficiently. However, when it is actually applied to the metal plate, it can happen that the surface of the flake nickel exists perpendicularly to the coating surface, or the chain nickel exists in the horizontal direction on the coating surface. For this reason, it is extremely difficult to cause flake-like nickel and chain-like nickel to exist ideally in the film, and this method has a problem that variations in electromagnetic shielding properties become large.

  In Patent Document 4, nickel having fine protrusions on the surface of the central core is contained in the coating, and the ratio of the average particle diameter r of the nickel to the coating thickness t is defined as 0.3r ≦ t ≦ 1. In the case of 2r + 0.5, it is described that excellent conductivity can be obtained. However, in the study by the present inventors, there is a concern that the slidability deteriorates due to the fine protrusions of nickel.

  On the other hand, since an electromagnetic wave generation source in a home appliance or the like is also a heat generation source, the material of the electronic device casing is required to have a characteristic of efficiently releasing heat. For example, Patent Document 5 discloses a technique of using, as a material for an electronic device casing, a metal plate on which a highly heat-dissipating film is formed as a countermeasure against a temperature rise inside an electronic device incorporating an electronic component. Patent Document 5 discloses that by adding 10 to 50% by mass of nickel having an average particle size of 0.5 to 20 μm in the film, the film is also excellent in conductivity. However, studies on the addition amount, shape, particle size, and coating thickness of nickel are insufficient, and sufficient conductivity is not obtained.

  Moreover, in the said invention, as one factor that sufficient electroconductivity is not acquired, only the concept of an average particle diameter is used as a particle size of a particle | grain, and the particle size distribution may not be considered.

Japanese Patent Publication No. 2-34672 Japanese Patent Publication No. 6-57871 Japanese Patent No. 3068999 JP-A-2005-313609 Japanese Patent Laid-Open No. 2004-160979

Yasutaka Shimizu “Latest Electromagnetic Wave Absorption and Blocking”, p. 205-223, Nikkei Technical Library Co., Ltd. (1999) Toshio Kudo, EMCJ, 89-96 (1990) p. 51-54 Toshio Kudo, Mitsubishi Electric Industrial Times, No. 79 (1990)

  This invention is made | formed in view of the said subject, and when used as a material of a housing | casing, it aims at providing the surface treatment metal plate excellent in the electromagnetic wave shielding property of a junction part.

  As a result of intensive studies to provide a surface-treated metal plate excellent in electromagnetic wave shielding properties, the inventors of the present application have found that in the surface-treated metal plate having a film containing granular nickel on one side or both sides of the metal plate, It has been found that the intended purpose can be achieved by controlling the particle size distribution of nickel.

  The gist of the present invention is as follows.

(1) In a surface-treated metal plate having a coating containing granular nickel on one side or both sides of the metal plate, the average film thickness of the coating is t (μm), the particle size of nickel is R _Ni , and the number distribution of nickel The number distribution peak exists at least in the range of 1 <[R _Ni / t] ≦ 2 when the distribution width of the 20% frequency level when the peak height is 100% is W ₂₀ (μm). and, wherein the number distribution _{W 20} peak is 5 or less, in the range of 2 _<[R Ni / t] does not exist a peak of the number distribution in the range of 2 _<[R Ni / t] A surface-treated metal sheet, wherein the number of nickel is less than 5 × 10 ⁹ per m ² .
(2) In a surface-treated metal plate having a coating containing granular nickel on one or both sides of the metal plate, the average film thickness of the coating is t (μm), the nickel particle size is R _Ni , and the number distribution of nickel The peak of the number distribution falls within the range of 0.5 <[R _Ni / t] ≦ 2 when the distribution width of the 20% frequency level when the peak height is 100% is W ₂₀ (μm). present at least, the is a _{W 20} of the peak of the number distribution of 5 or less, 2 _<in the range of _[R Ni / t] does not exist a peak of the number distribution, the range of 2 _<[R Ni / t] The number of nickel in the film is less than 5 × 10 ⁹ per m ² , and the nickel satisfying 0.5 <[R _Ni / t] ≦ 2 on the surface of the film is 1 × 10 ⁹ or more and 9 × 10 ¹⁰ per m ^2. A surface-treated metal sheet, characterized in that:
(3) The surface-treated metal sheet according to (2), wherein the peak of the number distribution exists at least in a range of 1 <[R _Ni / t] ≦ 2.
(4) When the number of nickel in the range of 1 <[R _Ni / t] ≦ 2 is N ₁ and the number of nickel in the range of R _Ni /t≦0.5 is N _s , the surface The surface-treated metal plate according to any one of (1) to (3), wherein the nickel in the film of the treated metal plate satisfies 15 ≦ [N _s / N ₁ ] ≦ 100.
(5) The nickel satisfying 1 <[R _Ni / t] in the film of the surface-treated metal plate is 1 × 10 ⁹ or more and 5 × 10 ¹⁰ or less per 1 m ² (1 The surface-treated metal plate according to any one of (4) to (4).
(6) Nickel satisfying 1 <[R _Ni / t] ≦ 2 in the film of the surface-treated metal plate is present in a circle having a radius of 1 mm, (1) to (5 The surface-treated metal plate according to any one of 1).
(7) In the surface-treated metal plate having a coating containing granular nickel on one or both sides of the metal plate, there are two peaks of the number distribution of granular Ni in the coating, and the nickel peak particles on the large particle size side When the diameter R _pl and the peak particle diameter R _ps of nickel on the small particle diameter side, the number of nickel in the peak particle diameter R _pl is n _l , and the number of nickel in the peak particle diameter R _pl is n _s , the large particle diameter side _{W 20} peak number distribution of nickel of 5 or less, _{W 20} of the peak of the number distribution of nickel particle diameter is 1.5 or _{less, 0.15 ≦ [R ps / R} pl] ≦ 0 .4,15 ≦ surface-treated metal sheet according to _{[n s / n l] ≦} 100, and satisfies the (2).
(8) The surface-treated metal plate according to any one of (1) to (7), wherein a peak particle size R _pl of nickel on the large particle size side is 6 μm or less.
(9) The infrared total emissivity in the region of wave number 600 to 3000 cm ⁻¹ measured on the surface having the film of the surface-treated metal plate at a predetermined temperature of 80 ° C. or more and 200 ° C. or less is 0.70 or more. The surface-treated metal plate according to any one of (1) to (8), which is characterized.
(10) The surface-treated metal sheet according to any one of (1) to (9), wherein the film of the surface-treated metal sheet further contains carbon black.
(11) The surface-treated metal plate according to any one of (1) to (10), wherein the film of the surface-treated metal plate further contains a wax.
(12) An electronic device housing using the surface-treated metal plate according to any one of (1) to (11) as a member.

  According to the present invention, it is possible to provide a surface-treated metal plate that is excellent in electromagnetic wave shielding properties at a joint when used as a material for a casing.

It is a graph showing the example of the relationship between _RNi / t of the surface treatment metal plate which concerns on one Embodiment of this invention, and the relative particle amount on the number basis. It is a graph showing an example of the relationship between the relative particle amount in R _Ni and number-based surface-treated metal sheet according to an embodiment of the present invention. It is a graph showing the example of the relationship between _RNi / t of the conventional surface treatment metal plate, and the relative particle amount on the number basis. It is a graph showing the example of the relationship between _{RNi of the} conventional surface treatment metal plate, and the relative particle amount on the number basis. It is a graph showing the example of the relationship between _RNi / t of the surface treatment metal plate which concerns on one Embodiment of this invention, and the relative particle amount on the number basis. It is a graph showing an example of the relationship between the relative particle amount in R _Ni and number-based surface-treated metal sheet according to an embodiment of the present invention. It is explanatory drawing for demonstrating the outline of the measuring apparatus used for the transfer impedance measurement in one Example of this invention. It is explanatory drawing for demonstrating the outline of the draw bead test machine used for the slidability test in one Example of this invention. It is an expanded schematic sectional drawing of the concave mold and convex mold of the draw bead test machine used for the slidability test in one Example of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  Since the shield efficiency SE, which is an index of electromagnetic wave shielding properties, is expressed by the transfer impedance Ztr as shown in the following formula (1) (Non-Patent Document 2), by reducing the transfer impedance at the junction of the electronic device casing: In order to improve the electromagnetic wave shielding property, the inventors of the present application diligently studied a method for reducing the transfer impedance.

SE = k · Zw / Ztr (1)
SE: electromagnetic wave shielding effect, k: proportional constant,
Zw: spatial impedance, Ztr: transfer impedance

The surface-treated metal plate provided with a coating containing granular nickel on one side or both sides of the metal plate has an average film thickness of t (μm), a nickel particle size of R _Ni , and a nickel number distribution peak. The number distribution peak is in the range of 1 <[R _Ni / t] ≦ 2 and the number distribution when the distribution width of the 20% frequency level when the height is 100% is W ₂₀ (μm). peak _{W 20} 5 or less, and 2 _<in the range of _[R Ni / t] no peak of number distribution, and 2 _<[R Ni / t] range of nickel is 1 m ² per 5 × of The number is less than 10 ⁹ .

Alternatively, the surface-treated metal plate provided with a coating containing granular nickel on one or both sides of the metal plate has an average film thickness of t (μm), a nickel particle size of R _Ni , and a nickel number distribution. The number distribution peak is in the range of 0.5 <[R _Ni / t] ≦ 2 when the distribution width of the 20% frequency level is W ₂₀ (μm) when the peak height is 100%. and is a _{W 20} of the peak of the number distribution of 5 or less, and, 2 _<in the range of _[R Ni / t] no peak of number distribution, and, 2 _{<a [R} Ni / t] The range of nickel is less than 5 × 10 ⁹ per m ² , and nickel satisfying 0.5 <[R _Ni / t] ≦ 2 on the coating surface is 1 × 10 ⁹ or more and 9 × 10 ¹⁰ or less per m ^2. It exists.

  The conductive fine particles used in the present invention is nickel. Since nickel is difficult to oxidize, there is little decrease in conductivity when the coating film is dried and cured at a high temperature. Moreover, it is excellent also in terms of cost.

Here, the index [R _Ni / t] focused on in the present invention indicates the relative particle diameter of the nickel particles with respect to the average film thickness of the film. When [R _Ni / t] is 1, it represents that the particle diameter of the nickel particles is equal to the average film thickness of the film. Further, when [R _Ni / t] is less than 1, it represents that the particle diameter of the nickel particles is smaller than the average film thickness of the coating, and when [R _Ni / t] is more than 1, the nickel particles It represents that the particle size of is larger than the average film thickness of the film.

Since _{nickel of} 1 <[R _Ni / t] ≦ 2 can directly connect the surface of the film and the metal plate, low transfer impedance is obtained, and nickel protrudes from the film appropriately. Unevenness is small and slidability is excellent. For this reason, when there is a particle size distribution peak in the range of 1 <[R _Ni / t] ≦ 2, low transfer impedance and excellent slidability can be obtained.

0.5 _{<a [R Ni / t] ≦ 2} , there 0.5 _<[R Ni / t] nickel satisfying ≦ 2 is 1 m ² per 1 × 10 ⁹ or more 9 × ^{10 10} or less on the film surface In this case, the nickel particles satisfying 1 <[R _Ni / t] ≦ 2 can directly conduct the film surface and the metal plate, and the nickel particles _satisfying 0.5 <[R _Ni / t] <1 In addition, low transfer impedance and excellent slidability can be obtained by forming a conduction path with the base material via a plurality of nickel particles in the film, with some of the nickel particles on the surface, and in any case However, since nickel protrudes moderately from the film, the surface irregularities are small and the slidability is excellent. _{Therefore, 0.5 <[R Ni / t} ] ≦ with exist peak of the particle size distribution in the second range, 0.5 to coating surface _<[R Ni / t] nickel satisfying ≦ 2 is 1 m ² per 1 × Even when there are 10 ⁹ or more and 9 × 10 ¹⁰ or less, low transfer impedance and excellent slidability can be obtained.

Nickel with [R _Ni /t]≦0.5 may have high transfer impedance because there are too many interfaces between nickel that must be interposed in order for the coating surface and the metal plate to conduct. On the other hand, nickel of 2 <[R _Ni / t] tends to have large surface irregularities and may have poor slidability.

  Furthermore, the form of nickel used in the present invention is granular. Here, granular means a form in which the maximum diameter / minimum diameter of the particles is 2 or less. In addition, if the primary particles are granular, a form such as a chain in which a plurality of granular particles are continuous is also regarded as granular.

  The reason for limiting the shape of nickel to granular is that it has been found that a low transfer impedance can be stably obtained by optimizing the relationship between the particle size of granular nickel and the thickness of the coating and the particle size distribution.

  Next, the particle size distribution of nickel will be described. In defining the particle size of the particles, conventionally, the concept of simply the average particle size has been used. This is obtained by simply calculating and calculating the particle size of each particle. However, the particle size distribution of industrially produced particles, particularly microparticles with an average particle size of several μm, is larger in size, and the tail is on the larger particle size side. Since the distribution tends to be formed, it is not a normal distribution. Therefore, a stable transfer impedance cannot be obtained simply by defining the average particle size of the conductive particles contained in the film. Therefore, the inventors of the present application have examined the relationship between the particle diameter of the optimal granular nickel and the thickness of the film and the particle size distribution in order to obtain a stable transfer impedance, and the particle size distribution is not a simple average of the particle diameters. I found it important.

That is, for the Ni particles in the film, the particle size is measured, the number of particles having the particle size is counted, the horizontal axis is the particle size / film thickness, and the vertical axis is the number of particles (for example, relative particle amount). When the distribution graph is created, the number distribution peak is in the range of 0.5 <[R _Ni / t] ≦ 2 as shown in FIG. 1, for example, and for example, as shown in FIG. The number distribution peak W ₂₀ in the particle size distribution graph with the axis as the particle size and the vertical axis as the number of particles is 5 or less, and the number distribution peak is in the range of 2 <[R _Ni / t]. The nickel in the range of 2 <[R _Ni / t] is less than 5 × 10 ⁹ per m ² , and the surface of the coating satisfies 0.5 <[R _Ni / t] ≦ 2. film satisfying 1 m ² per 1 × 10 ⁹ or more 9 × ^{10 10} or less at a condition, the transfer Inpi Dance is low, and, take the balance of the other performance. Incidentally, W _20, for example as shown in FIG. 2, the particle size of the horizontal axis, vertical axis number of particles of the particle size distribution of 20% power level at which the height of the peak of the time of the preparation was defined as 100% graph The distribution width of.

Here, it is assumed that there is basically one particle size distribution peak in the range of 0.5 <[R _Ni / t] ≦ 2 according to the present invention, but a plurality of peaks are overlapped. Can also occur. At this time, if there is an intersection of overlapping peaks, if the intersection is at a position that is 70% or more of the peak height of the reference peak (the highest peak), these are regarded as one peak. W ₂₀ is calculated, and the average particle size of each peak particle size is defined as the peak particle size. If the intersection is a position less than 70% of the peak height, W ₂₀ is calculated assuming that each peak has a shape in which a line is vertically drawn from the intersection. If W ₂₀ thus obtained is 5 or less satisfied the conditions of the present invention, low transfer impedance, and, take the balance with other performances.

However, for example, as shown in FIGS. 3 and 4, the particle size distribution of the number distribution peak in the range of 0.5 <[R _Ni / t] ≦ 2 is wide, or in the range of 2 <[R _Ni / t]. When the peak exists, a large amount of nickel having a particle size larger than the peak particle size of the number distribution in the range of 0.5 <[R _Ni / t] ≦ 2 exists. In that case, only large particles contribute to conduction, so the number of conduction points decreases, and the transfer impedance increases. In addition, the unevenness of the surface is further increased, and the slidability is also deteriorated.

Therefore, it has a number distribution peak in the range of 0.5 <[R _Ni / t] ≦ 2, the peak W ₂₀ is 5 or less, and 2 <[R _Ni / t] There is no number distribution peak and the number of nickel in the range of 2 <[R _Ni / t] is less than 5 × 10 ⁹ per m ² , and 0.5 <[R _Ni / t] ≦ When nickel satisfying 2 is 1 × 10 ⁹ or more and 9 × 10 ¹⁰ or less per 1 m ² , the performance is particularly good. Since _{nickel of} 1 <[R _Ni / t] ≦ 2 can directly conduct, it is more preferable to have a number distribution peak in the range of 1 <[R _Ni / t] ≦ 2. W ₂₀ is more preferably 3.5 or less. More preferably, the nickel in the range of 2 <R _Ni / t is less than 2 × 10 ⁹ per m ² . Moreover, since nickel in the range of 4 <R _Ni / t remarkably deteriorates performance, it is more preferable not to include it in the film.

When examining the number distribution, it is desirable to collect data by setting the particle size number measurement range to 0.05 μm. The particle size distribution can be obtained by taking a secondary electron image of the cross section of the coating film and actually measuring the particle size of the particles. When the intersection of peaks exists in the range of 0.5 <[R _Ni / t] ≦ 2, if the intersection is a position of 70% or more of the peak height, it is regarded as one peak and W ₂₀ is calculated. The average particle size of each peak particle size is defined as the peak particle size. If the intersection is a position that is less than 70% of the peak height, each peak is regarded as having a shape with a line drawn perpendicularly from the intersection, and W ₂₀ is calculated.

In addition, when there are a plurality of peaks in the range of 0.5 <[R _Ni / t] ≦ 2, nickel on the small particle diameter side is less likely to contribute to conduction, or nickel is less likely to be arranged efficiently, Since the conduction point tends to decrease, it is more preferable that the particle size distribution has a single peak in the range of 0.5 <[R _Ni / t] ≦ 2.

2 per 1 m ² _{<0.5 <number} of nickel that meets the _[R Ni / t] ≦ 2 of _[R Ni / t] range of the number of nickel and 1 m ² per film surface of the surface of the coating film It can be obtained by taking a secondary electron image, measuring the particle diameter, and counting the number.

Furthermore, the inventors have defined that the number of nickel in the range of 1 <[R _Ni / t] ≦ 2 is N ₁ and the number of nickel in the range of R _Ni /t≦0.5 is N _s , For example, as shown in FIG. 5, it has been found that a lower transfer impedance can be obtained by satisfying 15 ≦ [N _s / N _l ] ≦ 100. This is because the presence of nickel of R _Ni /t≦0.5 connects the nickel of 1 <[R _Ni / t] ≦ 2 and the metal plate, thereby increasing the conduction path and obtaining a lower transfer impedance. Because it can. Further, nickel satisfying R _Ni /t≦0.5 has little influence on the surface unevenness, and therefore hardly affects the slidability. When N _s / N _l <15, nickel in the range of R _Ni /t≦0.5 is less than nickel in the range of 1 <[R _Ni / t] ≦ 2, so 1 <[R _Ni / t ] It is difficult to tie nickel in the range of ≦ 2 and the metal plate. In addition, when N _s / N _l > 100, nickel in the range of R _Ni /t≦0.5 is too much for nickel in the range of 1 <[R _Ni / t] ≦ 2, so that low transfer impedance and good It may be difficult to achieve both good slidability.

The nickel satisfying 1 <[R _Ni / t] ≦ 2 in the coating according to the present invention is preferably 1 × 10 ⁹ or more and 5 × 10 ¹⁰ or less per 1 m ² . If the number of nickel satisfying 1 <[R _Ni / t] is less than 1 × 10 ⁹ per 1 m ² , the number of conduction points may be insufficient and the transfer impedance may be increased. On the other hand, when the number of nickel satisfying 1 <[R _Ni / t] exceeds 5 × 10 ¹⁰ per 1 m ² , the film becomes brittle, so that the impact resistance of the film is reduced, and the binder resin or lubricant is used. Since the relative ratio of the above and the like is reduced, there is a possibility that the characteristics of the film may be deteriorated, for example, the slidability at the time of deep drawing is lowered.

The nickel satisfying 1 <[R _Ni / t] in the coating according to the present invention is preferably present at least 5 or more in a radius of 1 mm. If there are less than 5 nickel parts satisfying 1 <[R _Ni / t] in the radius range of 1 mm, the transfer impedance of the part becomes remarkably high, and the transfer impedance may be increased as a whole film. is there.

Further, as a result of further studies, the present inventors have found that there are two peaks of the number distribution of granular Ni in the film in the surface-treated metal sheet having a film containing granular nickel on one or both surfaces of the metal sheet. The peak particle size R _pl of nickel on the large particle size side, the peak particle size R _ps of nickel on the small particle size side, the number of nickel in the peak particle size R _pl is n _l , and the number of nickel in the peak particle size R _ps is when the n _s, as shown in FIG. 6, for example, following the peak of W ₂₀ of the number distribution of nickel having a greater particle diameter is 5, W ₂₀ of the peak of the number distribution of nickel particle diameter is 1 .5 or less, and those satisfying 0.15 ≦ [R _ps / R _pl ] ≦ 0.4 and 15 ≦ [n _s / n _l ] ≦ 100 should have low transmission impedance and excellent slidability I found.

This is because there is nickel on the small particle size side to connect the nickel on the large particle size side and the metal plate, nickel on the large particle size side and the surface between the nickel on the large particle size side, and the particle size distribution. the large peaks of _{W 20} of the number distribution of the nickel diameter is 5 or less, _{W 20} of the peak of the number distribution of nickel particle diameter is 1.5 or less, 0.15 ≦ _R ps _{/ R pl} This is because a conduction path can be stably obtained by controlling so as to satisfy ≦ 0.4 and 15 ≦ [n _s / n ₁ ] ≦ 100.

If W ₂₀ peak number distribution of nickel having a greater particle diameter of the particle size distribution is more than 5, if the W ₂₀ of the peak of the number distribution of nickel smaller particle size side is more than 1.5, [R ps _/ R _{When [pl} ] is less than 0.15, [R _ps / R _pl ] exceeds 0.4, it is difficult to obtain a stable conduction path and the transfer impedance becomes high, which is not suitable. In addition, when n _s / n _l <15, the nickel on the small particle size side is smaller than the nickel on the large particle size side. It is not suitable because it is difficult to connect the nickel on the particle size side to the surface and the transfer impedance becomes high. [N _s / n _l ]> 100 is not suitable because there is too much nickel on the small particle size side compared to nickel on the large particle size side, making it difficult to secure a conduction path and high transfer impedance. .

R _pl is preferably 6 μm or less. When R _pl exceeds 6 μm, nickel tends to settle in the paint and it becomes difficult to stably maintain the dispersed state of Ni particles. For example, paintability when coated with a roll coater is poor. There is a fear.

  The film thickness of the film according to the present invention is preferably, for example, 0.8 to 10 μm. If the thickness is less than 0.8 μm, the film tends to break during processing, which is not preferable. Moreover, when it exceeds 10 micrometers, it is unpreferable also from the surface of manufacturing cost.

If the total infrared emissivity in the region of wave number 600 to 3000 cm ⁻¹ measured at a predetermined temperature of 80 ° C. or higher and 200 ° C. or lower on the surface having the coating film of the surface-treated metal plate is 0.70 or higher, heat dissipation is also provided. This is more preferable.

Since the radiation absorption in the wave number region of less than 600 cm ⁻¹ or more than 3000 cm ⁻¹ has a very small effect on the heat of the casing outer plate, the emissivity including radiation in these wave number regions is not preferable. Further, when a heat-absorbing film layer having an infrared total emissivity of less than 0.70 in the region of wave numbers of 600 to 3000 cm ⁻¹ is coated, the effect of imparting heat dissipation is small because the temperature lowering effect in the housing is small. The method for imparting heat dissipation is not particularly limited. For example, a method of incorporating carbon black in the conductive film is preferable. This is because carbon black imparts heat dissipation and is effective in lowering transfer impedance as described above. Under the present circumstances, it is preferable to contain about 10-30 mass parts of carbon black with respect to 100 mass parts of resin solid content in a coating material. If the content is less than 10 parts by mass, the heat absorbability of the film may be low, and the emissivity may be less than 0.70, and the transfer impedance may not be reduced. On the other hand, when the content exceeds 30 parts by mass, the storage stability may be deteriorated, for example, the viscosity of the paint becomes remarkably increased. Moreover, it is not preferable also from the surface of cost.

  Due to the high integration of electronic circuits, a large number of electronic components are incorporated in the housing, so that the capacity of the housing needs to be increased. For this reason, the metal plate of the casing is required to have deep drawability, and a film excellent in slidability is desirable. Therefore, the conductive film of the present invention may contain, for example, wax for the purpose of improving slidability. The type of wax is not particularly limited, and for example, polyethylene, polytetrafluoroethylene, or the like can be used. At this time, the wax is preferably contained in an amount of, for example, about 5 to 15 parts by mass with respect to 100 parts by mass of the resin solid content in the paint. If the content is less than 5 parts by mass, there is a possibility that excellent slidability cannot be obtained. On the other hand, if the content exceeds 15 parts by mass, the coating performance such as T-bending processability and adhesion may be deteriorated. Moreover, it is not preferable also from the surface of cost.

  The film of the present invention may be applied to only one side or may be applied to both sides, and can be appropriately selected as necessary. In addition, when the coating of the present invention is applied on one side and a colored coating, a design coating, a coating having other functions, etc. are applied on the other side, the design and functionality of the metal plate of the present invention are applied. Is more preferable.

  As the binder used for the film of the present invention, generally known ones such as polyester resin, urethane resin, acrylic resin, epoxy resin, melamine resin, vinyl chloride resin and the like can be used. Thermoplastic type, thermosetting type Any type may be sufficient.

  These resins may be used in combination of several kinds as required. These resins are not particularly specified because the film performance, for example, processability, work adhesion, film hardness, and the like differ depending on the type, molecular weight of the resin, and glass transition temperature (Tg) of the resin. Appropriate selection may be made according to the above.

  In addition, the type of resin that is cured using a cross-linking agent depends on the type and addition amount of the cross-linking agent and the type and amount of catalyst added during the cross-linking reaction. Since hardness etc. differ, it does not prescribe | regulate in particular, What is necessary is just to select suitably as needed.

  These resins can be used by melting a solid one by heat, dissolving it in an organic solvent, or pulverizing it into a powder. Further, it may be water-soluble or water-dispersed emulsion type. Furthermore, an ultraviolet (UV) curing type or an electron beam (EB) curing type may be used. Any of these commercially available types can be used.

  According to the knowledge obtained by the present inventors so far, when the surface-treated metal plate of the present invention is produced as a pre-coated metal plate and then cut, processed and assembled, as a binder, for example, a solvent-based melamine A curable polyester system, a solvent-based isocyanate curable polyester system, and the like are suitable. The Tg of the polyester resin is preferably -10 to 70 ° C. If the Tg of the polyester resin is less than −10 ° C., the film may not be formed, and if it exceeds 70 ° C., the film is too hard and the workability may be reduced.

In the film of the present invention, a color pigment, a rust preventive pigment and a rust preventive agent can be used in combination as required. Examples of the color pigment include titanium oxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), alumina (Al ₂ O ₃ ), and kaolin. Generally known color pigments such as inorganic pigments such as clay and organic pigments can be used. As for the rust preventive pigment, for example, commonly known chromium rust preventive pigments such as strontium chromate and calcium chromate, zinc phosphate, zinc phosphite, aluminum phosphate, aluminum phosphite, molybdate, phosphorus Generally known non-chromium rust preventive pigments and rust preventives such as acid molybdate, vanadic acid / phosphoric acid mixed pigment, silica, and a type of silica adsorbed with Ca called calcium silicate can be used.

  Further, generally known leveling agents, pigment dispersants and the like can be added to the coating of the present invention as required. The type and amount of these additives are not particularly defined and can be appropriately selected as necessary.

  In order to form the film of the present invention on the surface of a metal plate, a film component containing a binder can be generally applied in the form of a known paint. For example, the paint forms include a solvent-based paint in which a resin is dissolved in a solvent, a water-based paint in which an emulsified resin is dispersed in water, a powder paint obtained by pulverizing a resin, and a pulverized and powdered resin in water. There are slurry powder coatings, ultraviolet (UV) curable coatings, electron beam (EB) curable coatings, film laminates that are applied with resin on the film, and forms that are applied after the resin is melted. . The coating method is not particularly limited, and generally known coating methods such as roll coating, roller curtain coating, curtain flow coating, air spray coating, airless spray coating, brush coating, and die coater coating can be employed. However, roll coating, roller curtain coating, and curtain flow coating are suitable when the conductive film is previously coated on the metal plate as the pre-coated metal plate.

  In addition, before coating a metal plate with a film, it is preferable to subject the metal plate to a chemical conversion treatment in order to increase the film adhesion of the metal plate. When this chemical conversion treatment is performed, the adhesion of the film and the corrosion resistance of the metal plate are improved, which is more preferable. Even if the chemical conversion treatment is not performed, if the coating film adheres, the coating chemical conversion treatment step can be omitted, which is more preferable. As the chemical conversion treatment, generally known treatments such as coating chromate treatment, electrolytic chromate treatment, zinc phosphate treatment, zirconia treatment, and titania treatment can be used. In recent years, a non-chromate chemical conversion treatment based on an organic compound such as a resin has been developed. However, using a non-chromate chemical conversion treatment based on a resin is more preferable because it reduces the burden on the environment. . The adhesiveness of the coating layer and the corrosion resistance of the metal plate vary greatly depending on the type of chemical conversion treatment and the amount of adhesion, and therefore it is necessary to select them as necessary.

  Generally a well-known metal material can be used for the metal plate of this invention. The metal material may be an alloy material. For example, a steel plate, a stainless steel plate, an aluminum plate, an aluminum alloy plate, a magnesium alloy plate, a titanium plate, a copper plate, etc. are mentioned. The surface of these materials may be plated.

  Examples of the type of plating include zinc plating, aluminum plating, copper plating, and nickel plating. These alloy platings may be used. In the case of steel plates, generally known steel plates such as cold-rolled steel plates, hot-rolled steel plates, hot-dip galvanized steel plates, electrogalvanized steel plates, hot-dip galvanized steel plates, aluminum-plated steel plates, aluminum-zinc alloyed steel plates, stainless steel plates, etc. And plated steel plate can be applied.

  The metal plate of this invention is more preferable as a housing member of an electronic device. Examples of the electronic device casing to which the metal material of the present invention can be applied at least in part include digital home appliances such as desktop PCs and digital TVs, copying machines, car navigation, car AV, engine room electronic devices, Car electronics equipment such as an in-vehicle radar housing. Further, the metal material of the present invention may be used for a part of a casing for a mobile product such as a notebook PC or a mobile phone.

  Hereinafter, the details of the method for producing the sample paint used in the experiment will be described.

(Example 1)
[paint]
“Byron ^TM GK140” (number average molecular weight: 13000, Tg: 20 ° C.) manufactured by Toyobo Co., Ltd., which is a commercially available organic solvent soluble type / amorphous polyester resin (hereinafter referred to as polyester resin), is used as an organic solvent (Solvesso). 150 and cyclohexanone mixed in a mass ratio of 1: 1).

Next, 15 parts by mass of “Cymel ^TM 303” manufactured by Mitsui Cytec Co., Ltd., which is a commercially available hexa-methoxy-methylated melamine, is added to the polyester resin dissolved in the organic solvent with respect to 100 parts by mass of the solid content of the polyester resin. Further, 0.5 parts by mass of “Catalyst 6003B” manufactured by Mitsui Cytec Co., Ltd., which is a commercially available acid catalyst, was added and stirred to obtain a melamine-curable polyester-based clear paint.

  Next, the following particles were added to the prepared clear paint as shown in Tables 1 to 10 to prepare a sample paint.

[Nickel powder]
As the nickel powder according to this example, “Inco Type 123”, “Inco Type 255”, “Inco Type 287”, “Inco Type 110”, “Inco Type 210”, “Inco Type 210H” and “Inco HDNP” manufactured by INCO were used. The particle size distribution was adjusted and used by classification. The particle size distribution was determined by taking a secondary electron image of the cross section of the coating film and actually measuring the particle size of the particles.

[Carbon black]
As the carbon black according to this example, carbon black “Toka Black ^™ # 7350F” manufactured by Tokai Carbon Co., Ltd. was used.

[Polytetrafluoroethylene]
As polytetrafluoroethylene according to this example, polytetrafluoroethylene particles “Lublon L-5” manufactured by Daikin Co., Ltd. were used and used as wax.

  Hereinafter, the details of the method for producing the sample plate used in the experiment will be described.

A commercially available electrogalvanized steel sheet having a thickness of 0.5 mm (zinc adhesion amount: 20 g / m ^{2 on} one side) was diluted to 2% by mass with “FC4336” manufactured by Nippon Parkerizing Co., Ltd., which is a commercially available alkaline degreasing agent, at a temperature of 60 ° C. The solution was alkali degreased in an aqueous solution, washed with water and dried. Next, “CT-E300” manufactured by Nihon Parkerizing Co., Ltd., which is a commercially available non-chromate chemical conversion treatment liquid, is applied on the degreased electrogalvanized steel sheet using a roll coater, and hot air is applied under conditions such that the ultimate plate temperature is 60 ° C. Dried. The adhesion amount was 150 mg / m ² as the total film amount.

  Furthermore, on each of the front and back surfaces on the metal plate subjected to the chemical conversion treatment, the prepared paint was controlled with the film thickness described in Tables 1 to 4 while being coated with a roll coater, and in an induction heating furnace combined with hot air Dry cured. The drying and curing conditions were 230 ° C. at the ultimate plate temperature (PMT).

The particle size distribution of nickel was obtained by cutting a specimen for observation from the metal plate of each example, embedding it in a resin, and then polishing the cross section perpendicular to the surface of the coating film as a smooth observation surface by polishing. The film was photographed at a magnification of 1000 times, and the particle diameter of nickel in the coating film was actually measured. In addition, the observation for a particle size measurement was implemented for each test piece 3 places each about the length of the metal plate and the horizontal direction 20 mm. Further, 1 _{<0.5 <number} of nickel that meets the _[R Ni / t] ≦ 2 of _[R Ni / t] number of nickel satisfying and 1 m ² per film surface per 1 m ^2, the coating of the test piece Three locations on the surface of the film were photographed with a scanning electron microscope at a magnification of 1000 times, and each coating surface was determined by actually measuring the particle diameter of 10 mm square nickel. In addition, the particle diameter of nickel in cross-sectional observation and surface observation was an average value of the maximum diameter and the minimum diameter of each particle.

  In addition, the average film thickness is obtained by cutting a specimen for observation from the metal plate of each example, embedding it in a resin, smoothing the cross section perpendicular to the surface of the coating film by polishing, and using a scanning electron microscope. The film area of the metal plate and 20 mm in the horizontal direction was obtained by image analysis, and the area of the paint film was divided by the length in the horizontal direction with the metal plate. Each sample was measured at three locations, and the average value was defined as the average film thickness.

  Hereinafter, the details of the evaluation test of the produced surface-treated metal sheet will be described.

1) Measurement of transfer impedance The transfer impedance was measured using ZTR39D made by Mitsubishi Electric Industries as a measurement jig. Detailed description of this jig is found in Non-Patent Document 3. The test material is punched into a disk shape having an inner diameter of 11 mm and an outer diameter of 63 mm, and is mounted on a jig. A cross-sectional view of the jig after mounting is shown in FIG. ZTR39D originally has a structure in which a disk-shaped sample is sandwiched between upper and lower outer conductors and a central inner conductor. In this study, the transfer impedance of a film containing organic resin is measured more accurately. For this purpose, a ring-shaped conductor (made of gold-plated copper) having an inner diameter of 20 mm and an outer diameter of 60 mm was prepared and placed on the upper surface of the test material, thereby widening the contact area between the test material and the conductor. In addition, a Teflon plate having a thickness of 3 mm was disposed on the back surface of the test material to prevent conduction from the back surface. In order to improve the reproducibility of the measurement, the test material was squeezed only by the weight of the upper outer conductor without screwing the upper and lower outer conductors. At this time, the average surface pressure on the surface of the test material was 0.06 MPa. The jig was connected to a spectrum analyzer (manufactured by Advantest, R3361A) with a coaxial cable, the frequency of the input side voltage was swept from 30 MHz to 1000 MHz, and the power on the output side was measured. The transfer impedance Z _tr at each frequency was calculated from the power P2 when the test material was present, using the output side power P1 measured by setting the jig without mounting the test material as a reference, using the following formula. .

Z _tr = 2 × 50 × (P2 / P1)

(Measurement 1)
Each sample was performed 5 times, and the average of 3 data excluding the highest and the lowest was obtained. Evaluation was performed as follows by the difference between each average value and the transfer impedance of the standard sample (copper plate plated with gold) at 30 to 1000 MHz. The evaluation results are shown in Tables 1 to 10 with this method as measurement 1.

The evaluation criteria are as follows.
A: Transfer impedance difference with the standard sample is less than 0.2Ω in the entire range of 30 to 1000 MHz. A to O: Transfer impedance difference with the standard sample is 0.2Ω or more in the entire range of 30 to 1000 MHz. Less than 5Ω: The difference in transfer impedance with the standard sample is 0.5Ω or more and less than 1.0Ω in the entire range of 30 to 1000 MHz. Δ: The difference in transfer impedance with the standard sample is 1. in the entire range of 30 to 1000 MHz. 0Ω or more and less than 10Ω ×: The difference in transfer impedance from the standard sample may exceed 10Ω in the range of 30 to 1000 MHz.

(Measurement 2)
At some levels, the measurement was performed 5 times per sample, the average of 3 data excluding the highest and lowest values was determined, and the transfer impedances at 30 MHz and 500 MHz were evaluated as follows. The evaluation results are shown in Tables 6, 7, 9, and 10 with this method as measurement 2.

The evaluation criteria are as follows.
◎: Less than 0.5 × 10 ⁻⁴ Ω to ○: 0.5 × 10 ⁻⁴ Ω or more and less than 10 ⁻⁴ Ω ○: 10 ⁻⁴ Ω or more and less than 10 ⁻³ Ω Δ: 10 ⁻³ Ω or more 10 ⁻ Less than ² Ω x: 10 ⁻² Ω or more

2) Evaluation of electromagnetic wave shielding property An aluminum plate having a thickness of 3 mm was welded to prepare a casing having a side of 550 mm, and an opening of 137 mm × 137 mm was provided only on the upper surface. This was installed in a radio semi-anechoic chamber, and a Schaffner comb generator was fixed inside the housing as an electromagnetic wave reference transmission source, and then a pulse wave was transmitted at a frequency of 10 MHz to 1000 MHz at intervals of 10 MHz. A soft gasket having a width of 5 mm (SGK5-1 manufactured by Morimiya Electric Co., Ltd.) was placed around the opening. A test metal plate of 150 mm × 150 mm was placed thereon. By placing a receiving antenna at a point 3 m away from the housing in the horizontal direction and connecting it to a spectrum analyzer, the signal strength of the electromagnetic wave leaking from the housing is measured, and the electric field strength of 1 μV / m is set to 0 dB (reference value). ) As dB. The measurement was performed three times, and the obtained results were averaged and compared with a VCCI standard value (standard of information technology apparatus class B: 40 dB or less for 30 MHz to 230 MHz, 47 dB or less for 230 MHz to 1000 MHz).

The evaluation criteria are as follows.
○: VCCI standard value conformity at 30 to 1000 MHz ×: Measurement value not conforming to VCCI standard value was recognized at 30 to 1000 MHz

3) Heat dissipation In a region of wave number 600 to 3000 cm ⁻¹ when the plate temperature of the produced surface-treated metal plate is 80 ° C. using a Fourier transform infrared spectrophotometer “VALOR-III” manufactured by JASCO Corporation. The total emissivity of the surface-treated metal plate was measured by measuring the infrared emission spectrum and comparing it with the emission spectrum of a standard black body. In addition, the standard black body used what spray-coated "THI-1B black body spray" with a film thickness of 30 +/- 2micrometer on the iron plate by Tacos Japan company manufacture (Okitsumo company manufacture).

The evaluation criteria are as follows.
◎: 0.90 or more ◎ ~ ○: 0.80 or more and less than 0.90 〇: 0.70 or more and less than 0.80 △: 0.50 or more and less than 0.70 ×: Less than 0.50

4) Sliding property It was carried out with a draw bead testing machine shown in FIG. In FIG. 8, 11 is a test piece having an evaluation film on both sides, 12 is a concave mold, 3 is a convex mold, 4 is a load cell, and 5 is a hydraulic cylinder. FIG. 9 is an enlarged schematic cross-sectional view of a concave mold and a convex mold of the draw bead testing machine of FIG. As shown in FIG. 9, the convex surface R is 4 mm, the concave surface R is 2 mm, the depth is 6 mm, and the width is 12 mm.

  A test piece 11 having a width of 30 mm and a length of 300 mm is mounted between the concave mold 12 and the convex mold 13, and is pressed by the hydraulic cylinder 15 with a load P of 1 t, and the convex mold 13 is recessed via the test piece 11. The test piece 11 was pressed against the mold 12 and pulled upward at a pulling speed of 200 mm / min. A bead pulling test was performed, and the slidability was measured by the pulling load at that time.

The evaluation criteria are as follows.
◎: Less than 200 kg ◎ ~ ○: 200 kg or more and less than 250 kg 〇: 250 kg or more and less than 350 kg △: 350 kg or more and less than 450 kg ×: 450 kg or more

  Details of the evaluation results will be described below.

(1) Relationship between nickel particle size distribution and film thickness, nickel distribution density The reason for specifying the relationship between nickel particle size distribution and film thickness is that nickel contained in the film is properly distributed. Thus, a low transfer impedance is obtained while considering the slidability of the film. As the relationship between the particle size distribution of nickel and the film thickness, Example No. 1-No. 39 and no. 45-No. 75 and Comparative Example No. 40-No. 44 and no. 76-83.

As shown in the examples of the present invention, the nickel particle size distribution has a number distribution peak (in the table, the peak particle size is denoted as R _p ) in the range of 1 <[R _Ni / t] ≦ 2. The distribution width W ₂₀ at the 20% frequency level when the peak height is 100% is 5 or less, and there is no number distribution peak in the range of 2 <[R _Ni / t], and It is controlled so that the number of nickel in the range of 2 <[R _Ni / t] is less than 5 × 10 ⁹ per m ^2, or the peak particle size R _p is in the range of 0.5 <[R _Ni / t] ≦ 2. The distribution width W ₂₀ of the 20% frequency level is 5 or less when the peak height is 100%, and there is no number distribution peak in the range of 2 <[R _Ni / t]. , 2 _<nickel ranging _[R Ni / t] is less than 5 × 10 ⁹ per 1 m ^2, 0 to coating surface. _<[R Ni / t] by nickel satisfying ≦ 2 is controlled to be present 1 × 10 ⁹ or more 9 × ^{10 10} or less per 1 m ^2, ensure low transfer impedance and good slidability it can.

No. 31-39, when the number of nickel in the range of 1 <[R _Ni / t] ≦ 2 is N _l and the number of nickel in the range of R _Ni /t≦0.5 is N _s , By controlling so that 15 ≦ [N _s / N _l ] ≦ 100, a lower transfer impedance can be secured.

When W ₂₀ exceeds 5 (No. 40, 77) or has a peak in the range of 2 <[R _Ni / t] (No. 41, 78), 1 <[R _Ni / t] ≦ 2 It was suggested that there is a large amount of nickel having a particle size larger than the peak particle size of the number distribution in the range, and that conduction is increased only with large particles, so that the transfer impedance is increased. Further, when the number of nickel in the range of 2 <[R _Ni / t] exceeds 5 × 10 ⁹ (No. 42, 79), it was suggested that the surface unevenness was increased and the slidability was inferior.

Peak particle diameter _{R p} is _{0.5 <[R Ni / t]} ≦ be in the 2 range of the film surface 0.5 _<[R Ni / t] nickel satisfying ≦ 2 is 1 m ² per 1 × 10 ⁹ When the number is less than the number (No. 80), it is suggested that the transfer impedance is increased because the conduction point is small. If there are more than 9 × 10 ¹⁰ nickel per 1 m ² satisfying 0.5 <[R _Ni / t] ≦ 2 on the surface of the film (No. 83), the number of nickel on the surface increases and the nickel is caught. It was suggested that the slidability was inferior

When having a particle size distribution peak only in the range of 0.5 ≧ [R _Ni / t] (No. 43, 76), the interface between nickel particles that must be interposed in order for the coating surface and the metal plate to conduct. It was suggested that the transfer impedance is high because of too much. On the other hand, when there is no peak in the range of 0.5 <[R _Ni / t] ≦ 2, and there is a peak only in the range of 2 <[R _Ni / t] (No. 44), the surface unevenness is large. It was suggested that the slidability tends to be poor.

The result of investigating the influence of the distribution density of nickel satisfying 1 <[R _Ni / t] on the area of the metal plate is shown in Example No. 84-90.

In order to give a low transfer impedance to the film of the present invention, it is necessary to raise the nickel distribution density in the film. However, it goes without saying that the slidability of the coating of the present invention is taken into consideration in this case as well. No. 84-No. The number per 1 m ^{2 of} nickel satisfying 1 <[R _Ni / t] as in 87 is in the range of 1 × 10 ⁹ or more and 5 × 10 ¹⁰ or less. Since the lower transfer impedance and the excellent slidability are shown in comparison with 88 and 89, the number of nickel satisfying 1 <[R _Ni / t] per 1 m ² is 1 × 10 ⁹ or more and 5 × 10 ¹⁰ or less. It can be seen that the range of is more preferable.

Further, even if the number of nickel satisfying 1 <[R _Ni / t] per 1 m ² is satisfied, 1 <[R _Ni / t] within a radius of 1 mm due to the dispersion state of the particles and the like. Example NO. In which there are less than 5 nickel parts satisfying ≦ 2. No. 90, the number of nickel satisfying 1 <[R _Ni / t] ≦ 2 within a radius of 1 mm is 5 or more. 84, 85, 86, and 87 show low transfer impedances, and it is more preferable that the number of nickel satisfying 1 <[R _Ni / t] in a radius of 1 mm is 5 or more.

In addition, Example No. As shown in 91 to 113, there are two peaks of the number distribution of granular nickel in the film, the W ₂₀ of the number distribution peak of nickel on the large particle size side is 5 or less, and the nickel on the small particle size side The number W of the peak of the number distribution of ₂₀ is 1.5 or less, 0.15 ≦ [R _ps / R _pl ] ≦ 0.4, and 15 ≦ [n _s / n _l ] ≦ 100. However, low transmission impedance and good slidability can be ensured.

In the particle size distribution of granular nickel in the film, when the W ₂₀ of the nickel number distribution peak on the large particle size side exceeds 5 (No. 114), the W ₂₀ of the nickel number distribution peak on the small particle size side. Is greater than 1.5 (No. 115), [R _ps / R _pl ] is less than 0.15 (NO. 116), and [R _ps / R _pl ] is greater than 0.4 (No. 115). 117), it is difficult to obtain a stable conduction path, suggesting that transfer impedance is high. When [n _s / n _l ] is smaller than 15 (No. 118), the nickel on the small particle size side is less than the nickel on the large particle size side. It was difficult to connect the nickel and the metal plate, the nickel on the large particle size side and the surface, suggesting that the transfer impedance was high. When [n _s / n _l ] exceeds 100 (No. 119), since there is too much nickel on the small particle size side with respect to nickel on the large particle size side, it is difficult to secure a conduction path and the transfer impedance is high. It was suggested that.

  As described above, by controlling the relationship between the nickel particle size distribution and the film thickness, and further the nickel distribution density within the range of the present invention, it is possible to ensure a low transfer impedance while considering the slidability of the film. I understand.

(2) Regarding the inclusion of carbon black The coating of the present invention contains carbon black (abbreviated as CB in the table) in order to further reduce the transfer impedance on the high frequency side by utilizing the effect of the dielectric, This is to provide a function of lowering the temperature of the film. No. 120-No. 125, no. 127-No. 129, no. 131-No. 133, no. 135-No. From FIG. 137, it can be seen that by adding an appropriate amount of carbon black, the transfer impedance on the high frequency side is lowered and heat dissipation can be imparted.

(3) Containing wax About the inclusion of the wax of the film of the present invention, the sliding property is further improved. No. 138-No. From 167, for example, it can be seen that slidability can be further imparted by adding an appropriate amount of polytetrafluoroethylene particles (abbreviated as PTFE in the table) as a wax.

(Example 2)
Example No. 7, 32, 91, 107, 125, 128, 132, 136, 154, 160, 166, Comparative Example No. Metal materials of 40 to 44, 76 to 83, 114 to 119 were used for the desktop PC casing. Radiation noise with a frequency of 30 MHz to 1000 MHz at a point 3 m away in a radio semi-anechoic room was measured and compared with the VCCI standard value. As a result, Example No. 7, 32, 91, 107, 125, 128, 132, 136, 154, 160, 166, Comparative Example No. Nos. 40 to 44, 76 to 83, and 114 to 119 satisfy the standards. From 40 to 44, 76 to 83, and 114 to 119, radiation noise exceeding the standard value was detected.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

Claims (12)

In the surface-treated metal plate having a coating containing granular nickel on one side or both sides of the metal plate,
When the average film thickness of the film is t (μm), the nickel particle size is R _Ni , and the nickel number distribution peak height is 100%, the distribution width of the 20% frequency level is W ₂₀ (μm). When
The number distribution peak is present at least in the range of 1 <[R _Ni / t] ≦ 2,
W _{20 of the} number distribution peak is 5 or less,
The number distribution peak does not exist in the range of 2 <[R _Ni / t],
The surface-treated metal sheet, wherein the number of nickel in the range of 2 <[R _Ni / t] is less than 5 × 10 ⁹ per 1 m ² . In the surface-treated metal plate having a coating containing granular nickel on one side or both sides of the metal plate,
When the average film thickness of the film is t (μm), the nickel particle size is R _Ni , and the nickel number distribution peak height is 100%, the distribution width of the 20% frequency level is W ₂₀ (μm). When
The number distribution peak is at least in the range of 0.5 <[R _Ni / t] ≦ 2,
W _{20 of the} number distribution peak is 5 or less,
The number distribution peak does not exist in the range of 2 <[R _Ni / t],
2 _<nickel in the range of _[R Ni / t] is less than 5 × 10 ⁹ per 1 m ^2,
Wherein 0.5 to film surface _<[R Ni / t] nickel satisfying ≦ 2, characterized in that the are present 1 × 10 ⁹ or more 9 × ^{10 10} or less per 1 m ^2, the surface treated metal plate. The surface-treated metal sheet according to claim 2, wherein the number distribution peak exists at least in a range of 1 <[R _Ni / t] ≦ 2. When the number of nickel in the range of 1 <[R _Ni / t] ≦ 2 is N ₁ and the number of nickel in the range of R _Ni /t≦0.5 is N _s ,
Nickel in the coating of the surface-treated metal plate, 15 ≦ and satisfies the _{[N s / N l] ≦} 100, the surface treated metal sheet according to any one of claims 1 to 3. The nickel satisfying 1 <[R _Ni / t] in the film of the surface-treated metal plate is 1 × 10 ⁹ or more and 5 × 10 ¹⁰ or less per 1 m ^2. The surface-treated metal plate according to any one of the above. 6. The nickel according to claim 1, wherein at least five nickels satisfying 1 <[R _Ni / t] ≦ 2 in the film of the surface-treated metal plate are present in a circle having a radius of 1 mm. The surface-treated metal plate according to Item. In the surface-treated metal plate having a coating containing granular nickel on one side or both sides of the metal plate,
There are two peaks of the number distribution of granular Ni in the film,
The peak particle size R _pl of nickel on the large particle size side, the peak particle size R _ps of nickel on the small particle size side, the number of nickel of the peak particle size R _pl is n _l , and the number of nickel of the peak particle size R _ps is n _s
W ₂₀ peak number distribution of nickel having a greater particle diameter of 5 or less, W ₂₀ of the peak of the number distribution of nickel particle diameter is 1.5 or less,
0.15 ≦ [R _ps / R _pl ] ≦ 0.4,
15 ≦ [ _ns / n ₁ ] ≦ 100,
The surface-treated metal sheet according to claim 2, wherein: The surface-treated metal plate according to any one of claims 1 to 7, wherein a peak particle size R _pl of nickel on the large particle size side is 6 µm or less. The infrared total emissivity in the region of wave number 600 to 3000 cm ⁻¹ measured at a predetermined temperature of 80 ° C. or higher and 200 ° C. or lower on the surface having the film of the surface-treated metal plate is 0.70 or higher. The surface treatment metal plate as described in any one of Claims 1-8. The surface-treated metal sheet according to any one of claims 1 to 9, wherein the film of the surface-treated metal sheet further contains carbon black. The surface-treated metal sheet according to any one of claims 1 to 10, wherein the film of the surface-treated metal sheet further contains a wax. The electronic device housing | casing which uses the surface treatment metal plate as described in any one of Claims 1-11 as a member.