TWI424921B - Conductive resin coated metal plate - Google Patents

Description

Conductive resin coated metal plate

The present invention relates to a resin-coated metal sheet which is excellent in conductivity and which is useful as a constituent material of an electronic device casing such as an audio-visual (AV) device, a personal computer peripheral device, an Internet connection device, or an in-vehicle information terminal.

As the latest trend in the field of electronic equipment, information processing. New high-performance, such as an increase in the transmission capacity and an increase in the recording capacity, has progressed, and electromagnetic waves leaking from electronic devices tend to increase. If the leakage electromagnetic wave increases, it causes an erroneous operation of a precision machine or the like disposed around the electronic device. Therefore, countermeasures are required, and the electronic device manufacturer faces the metal plate in order to improve the shielding property (conductivity) of the electromagnetic wave to prevent leakage thereof. A condition with higher conductivity requirements. In addition, from the viewpoint of cost reduction, it is also required to reduce the number of the nails and the like when joining the metal sheets, and it is expected that the contact pressure of the joint portions of the metal sheets (a light contact pressure of about 10 to 12 gf/mm ^{2 )} is expected. Underneath, a metal plate that still exhibits good electrical conductivity.

Conventionally, in order to impart conductivity to a resin-coated metal sheet, a method of containing conductive particles in a resin film has been known. For example, Japanese Laid-Open Patent Publication No. Hei 7-314601 discloses a precoat metal sheet in which scaly nickel is added to a resin to impart conductivity. However, in addition to conductivity, only pressure marks are evaluated. However, there is no research on the requirements such as bending workability and scratch resistance required for the recent resin-coated metal sheets.

In addition, a resin-coated steel sheet in which a magnetic film made of a resin containing a magnetic powder is coated on an alloyed hot-dip galvanized steel sheet is disclosed in Japanese Laid-Open Patent Publication No. 2006-161129. It has recently been desired that even if the contact pressure of the joint portions of the metal plates is small, good electrical conductivity can be exerted, and discussion on this point is insufficient.

In addition, Japanese Laid-Open Patent Publication No. 2004-183080 discloses a coated metal sheet having a mode value of the number distribution of conductive particles set to be as small as 0.05 to 1.0 μm. This is a technical idea of a conductive pass that is required to ensure weldability even when the film thickness is increased by a large amount of particles having a small particle diameter in the coating layer. In this publication, there is no light contact. Conductivity under pressure was investigated.

Accordingly, the present invention has been made to provide a resin-coated metal sheet which exhibits good electrical conductivity even when the contact pressure is small.

Moreover, the metal plate for electronic equipment has excellent electrical conductivity under light contact pressure, and also requires the same workability as the prior art. In particular, when the conductive particles are peeled off from the film during processing and fall on the base of the electronic device, the disadvantage is that it is a cause of malfunction of the electronic device.

Therefore, in the present invention, there has been proposed a problem of providing a resin-coated metal sheet which is excellent in workability and exhibits good electrical conductivity even when the contact pressure is small.

According to the first aspect of the invention, the surface of the metal plate is coated with the conductive particles. The conductive resin film is characterized in that it contains 20 to 65 mass% of conductive particles in the conductive resin film, and the Tg of the resin in the conductive resin film is -10 ° C to + 30 ° C, and the thickness of the conductive resin film is 1.2. ～14 μm, the content of the conductive particles is set to w (% by mass), the average particle diameter of the conductive particles is set to r (μm), and when the thickness of the conductive resin film is set to t (μm), the following is satisfied. Formula (i), 36≦w × (r/t) ≦ 200 (i).

The resin film is preferably obtained from a raw material composition containing an organic solvent-soluble polyester resin, and the metal plate is preferably a composition of an alloyed hot-dip galvanized steel sheet.

In the conductive resin-coated metal sheet according to the first aspect of the invention, conductive particles having an average particle diameter which has a certain relationship with the thickness of the film are added to the resin film having a specific Tg in a specific amount. Thereby, the resin film is easily deformed, and the conductive particles can be appropriately exposed from the surface of the resin film. Therefore, even if the contact pressure when the metal plates are joined to each other is small, it is needless to say that even if the conductive particles coated with the resin film are exposed by the deformation of the resin film, the conductive particles can exhibit good conductivity. .

Further, by setting the Tg of the resin film to an appropriate range, the bending workability and the scratch resistance are also good. Further, when an alloyed hot-dip galvanized steel sheet having a high hardness is used as the metal sheet, the resin film is deformed by attempting to alleviate the pressure applied to the resin-coated metal sheet, and thus the contact probability of the conductive particles is further improved.

According to a second aspect of the invention, the surface of the metal plate is coated with a conductive resin film containing conductive particles, and is characterized in that the conductive resin film contains 20~ 70% by mass of the conductive particles, the cumulative 50% volume average particle diameter d50 (μm) of the conductive particles and the thickness t (μm) of the conductive resin film satisfy the following formula (1), and accumulate 84% by volume average particle diameter d84 (μm), cumulative 16% volume average particle diameter d16 (μm) and the aforementioned d50 satisfy the following formula (2), 0.8≦d50/t≦2.0 (1) (d84-d16)/d50≦1.0 (2).

The conductive particles are more preferably a magnetic metal powder, and more preferably a carbonyl iron powder.

In the conductive resin-coated metal sheet according to the second aspect of the invention, the conductive particles having a sharp particle size distribution are used, and the contact pressure when the metal sheets are joined to each other is used, and the conductive particles having a sharp particle size distribution are used. Small can also play a good conductivity.

As described above, the conductive resin-coated metal sheets according to the first and second aspects of the invention are suitable as constituent members of the casing of the electronic device, and particularly suitable for a case where the contact pressure between the joint portions of the metal sheets is small.

Best form for carrying out the invention <First invention>

A conductive resin-coated metal plate (hereinafter referred to as a resin-coated metal plate) according to the first invention of the present invention (hereinafter referred to as the present invention) is characterized in that the content of conductive particles in the resin film w (% by mass) When the Tg (° C.) of the resin in the resin film and the thickness t (μm) of the resin film are within a certain range, and the average particle diameter of the conductive particles is set to r (μm), w, r, and t satisfy the following formula. (i).

36≦w×(r/t)≦200 (i)

First, t, w, and formula (i) will be described.

The resin film thickness t is 1.2 to 14 μm. When it is thinner than 1.2 μm, when the bending process is performed, the conductive particles are peeled off from the film, which is not preferable. When it exceeds 14 μm, the electrical conductivity is lowered, and it is not preferable from the viewpoint of cost. t is preferably 2 to 9 μm, more preferably 3 to 8 μm. t The film quality may be measured by a method of performing specific gravity conversion, or the cross section of the resin film may be observed by microscopic observation (SEM observation).

In the resin film, the content w of the conductive particles is 20 to 65% by mass. When the amount is less than 20% by mass, sufficient conductivity is not exhibited. When the amount is more than 65% by mass, the amount of the matrix resin in the film is relatively decreased, and the film is liable to invade cracks, which is not preferable. w is preferably 30 to 60% by mass, more preferably 35 to 55% by mass.

In the above formula (i), w is as described above as the content of the conductive particles in the resin film, and since r is the average particle diameter of the conductive particles, (r/t) is a guide for the electric particles with respect to the resin film. The thickness t is large, that is, the value is an index of the length of the conductive particles that protrude outward from the surface of the resin film. In the present invention, according to the relationship with conductivity, w. (r/t) is 36 or more and 200 or less. When it is less than 36, sufficient conductivity may not be exhibited, and if it exceeds 200, the conductive particles are likely to fall off from the film, which is not preferable. w. The optimum lower limit of (r/t) is 45, the lower limit is 50, the upper limit is 150, and the upper limit is 120.

The average particle diameter r of the conductive particles, if it satisfies the range of the above formula (i) There is no particular limitation, but it is approximately 3 to 30 μm. Further, the average particle diameter r is a 50% by volume average particle diameter obtained by laser diffraction (scattering type). The particle size distribution of the conductive particles is not necessarily sharp, and it can be directly used in the market, and it can be classified by a sieve and a net depending on the use.

The conductive particles which can be used in the present invention are, for example, metal particles or a conductive layer provided with a metal or the like on the surface of the inorganic or organic polymer particles. As the metal particles, magnetic powder, nickel, iron phosphide or the like can be used from the viewpoint of conductivity and corrosion resistance. When it is necessary to impart electromagnetic wave shielding performance to the metal plate, a magnetic metal powder having excellent conductivity and electromagnetic wave absorptivity can be used as the conductive particles. As such a magnetic metal powder, a nickel-iron permalloy (Ni-Fe-based alloy, Ni content of 35 mass% or more) and a germanium-alloy (Si-Al-Fe system) are suitable. Alloy) and so on.

The base resin which is a main component of the resin film will be described. In the resin-coated metal sheet of the present invention, a resin film composed of the above-mentioned conductive particles dispersed in a matrix resin is formed on the surface of the metal plate. As the matrix resin, for example, a polyester resin, an acrylic resin, a urethane resin, a polyolefin resin, a fluororesin, an organic silicone resin, and a mixture of such resins or a resin which produces denaturation Wait. When a thermosetting resin such as an epoxy resin or an unsaturated polyester resin is used as a raw material of the matrix resin, the obtained cured coating film is too hard and the deformation energy is small, which is not preferable in the present invention. The resin coated metal plate of the present invention is mainly used for the housing of an electronic device, and therefore requires bending In view of such characteristics as workability, film adhesion, and corrosion resistance, an organic solvent-soluble (non-crystalline) polyester resin is preferable.

As an organic solvent-soluble polyester resin, the "VYLON (registered trademark)" series produced by Toyobo Co., Ltd. is suitable for a wide variety of types. The polyester resin may also be crosslinked by a melamine or the like. As the melamine resin, the "mismaro (registered trademark)" series produced by Sumitomo Chemical Co., Ltd. and the "saimeru (registered trademark)" series produced by Mitsui Cytec Corporation are available.

In the resin-coated metal sheet of the present invention, the base resin grease Tg in the resin film formed on the metal plate must be -10 ° C to + 30 ° C. By setting Tg in this range, the deformation of the resin film can be improved, and the conductive particles can be appropriately exposed. When the Tg is lower than -10 ° C, the base resin is too soft and the scratch resistance is not good. However, if the Tg exceeds 30 ° C, the deformation energy of the resin is lowered and the conductivity is lowered, which is not preferable.

The Tg of the matrix resin means the value of Tg actually measured by Tg measurement of the entire resin film. In the resin film, in addition to the matrix resin (in the case of a resin + a crosslinking agent), a known additive such as a rust preventive, a matting agent, and a pigment may be contained, but the Tg is not affected by the dispersed solid additive.

Therefore, when the matrix resin is not crosslinked, the Tg of the matrix resin becomes the Tg of the entire resin film. Further, when the crosslinking is carried out, the Tg of the matrix resin after crosslinking is from -10 ° C to + 30 ° C, so that the amount of the crosslinking agent can be appropriately adjusted. Moreover, the ratio of resin to cross-linking agent, processability, etc. and durability From the viewpoint of the balance, it is preferred to blend the crosslinking agent (after the reaction) in an amount of 5 to 30% by mass in the resin film after drying.

The Tg of the present invention is obtained by cutting a resin film from a metal plate and using a differential scanning calorimeter (DSC) under a nitrogen atmosphere at a temperature range of -100 ° C to 180 ° C to raise the temperature at 20 ° C / min. Speed is going on.

The Tg of the VYLON (registered trademark) series produced by Toyobo Co., Ltd. is as follows. Such as VYLON 103 (47 ° C), VYLON 200 (67 ° C), VYLON 220 (53 ° C), VYLON 226 (65 ° C), VYLON 240 (60 ° C), VYLON 245 (60 ° C), VYLON 270 (67 ° C), VYLON 280 (68 ° C), VYLON 290 (72 ° C), VYLON 296 (71 ° C), VYLON 300 (7 ° C), VYLON 500 (4 ° C), VYLON 530 (5 ° C), VYLON 550 (-15 ° C), VYLON 560 (7 ° C), VYLON 600 (47 ° C), VYLON 630 (7 ° C), VYLON 650 (10 ° C), VYLON GK 110 (50 ° C), VYLON GK 130 (15 ° C), VYLON GK 140 (20 ° C ), VYLON GK 150 (20 ° C), VYLON GK 180 (0 ° C), VYLON GK 190 (11 ° C), VYLON GK 250 (60 ° C), VYLON GK 330 (16 ° C), VYLON GK 590 (15 ° C), VYLON GK 640 (79 ° C), VYLON GK 680 (10 ° C), VYLON GK 780 (36 ° C), VYLON GK 810 (46 ° C), VYLON GK 880 (84 ° C), VYLON GK 890 (17 ° C), VYLON BX 1001 (-18 ° C) and so on. These Tg are the temperatures stated in the catalog. Further, the molecular weight (Mn) of these is in the range of 3 × 10 ³ to 30 × 10 ³ .

As the original plate of the resin-coated metal sheet of the present invention, an aluminum plate, a copper plate, a cold-rolled steel plate, a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, or a plated alloy steel can be used. Board and so on. Among them, a plated alloy steel plate of zinc and an iron group element (Fe, Co, Ni). Since these metal plated steel sheets have high hardness as a metal plate, the pressure applied to the resin-coated metal plate is not relieved by the deformation of the metal plate, and the resin film is moderately deformed, so that the contact probability of the conductive particles is further improved. Further, among these plated alloy steel sheets, an alloyed hot-dip galvanized steel sheet (GA steel sheet) having a plating layer in which zinc and iron are alloyed is more preferable. Since iron has excellent electromagnetic wave absorptivity and iron in plating contributes to absorption of electromagnetic waves, the use of a GA steel sheet as an original plate can exhibit higher electromagnetic shielding properties.

From the viewpoint of ensuring molding, it is preferred that the Fe, Ni, and Co contents are controlled to be about 5 to 20% by mass. The detailed plating conditions of the hot-dip plating method are not particularly limited, and a method generally employed for alloying can be employed. Plating deposition amount in consideration of the electromagnetic wave absorbent, less suitable places, for example in the following ² 50g / m preferably, more preferably to 40g / m ² or less, further more preferably to 35g / m ² or less, to the best 30 g/m ² or less. The lower limit of the amount of plating is not particularly limited from the viewpoint of electromagnetic wave absorptivity, but 5 g/m ^{2 is more} preferable, and 10 g/m ² is more preferable in view of corrosion resistance.

In order to manufacture the resin-coated metal sheet of the present invention, the method of preparing the raw material composition of the resin film is preferably applied to a metal sheet and dried. The raw material composition is diluted with a base resin, a crosslinking agent or the like which is added as needed, using an organic solvent or the like to obtain a viscosity suitable for coating. The organic solvent is not particularly limited, and examples thereof include aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate (butyl acetate) and butyl acetate; alkyl An alicyclic hydrocarbon such as cyclohexane; an aliphatic hydrocarbon such as hexane or pentane; a methyl ethyl ketone or a cyclohexanone; Ketones, etc. The solid content of the raw material composition is preferably from about 5 to 45% by mass.

In the above-mentioned raw material composition, various known additives used in the field of resin-coated metal sheets such as a matting agent, an extender, a rust preventive, an anti-precipitant, and a paraffin may be added as long as the object of the present invention is not impaired. . Further, an additive for imparting heat dissipation properties such as carbon black may be added.

The method of applying the above-mentioned raw material composition to a metal plate is not particularly limited, and a bar coater method, a roll coater method, a sputtering method, and a shower method may be employed. Curtain flow coater method, etc. Drying is carried out after coating, but in the crosslinking agent addition system, it is preferred to heat dry at a temperature at which the crosslinking agent can react. Specifically, it may be heated at 100 to 250 ° C for about 1 to 5 minutes. Moreover, for the purpose of improving the corrosion resistance, the adhesion to the resin film, and the like, the metal plate may be subjected to a known surface treatment (underlayer treatment) such as chromate treatment or phosphate treatment. Or a metal plate which has been subjected to non-Chromate treatment may be used in consideration of environmental pollution or the like.

In the resin-coated metal sheet of the present invention, as described above, when a resin film containing conductive particles is laminated on a metal plate, for example, when it is used as a casing of an electronic device, the resin film is used in a casing. If necessary, in order to improve scratch resistance, fingerprint resistance, and the like, another resin film (upper layer) may be applied to the surface of the resin film. However, it is important that the upper ejector layer should not interfere with the exposure of the conductive particles and does not cause conduction. The film having a reduced property is specifically 0.2 to 1.5 μm, more preferably about 0.4 to 1.2 μm.

<The second invention>

In the resin film of the conductive resin-coated metal sheet of the invention of the second aspect (hereinafter referred to as the present invention), the conductive particles are contained in the range of 20 to 70% by mass. When the amount is less than 20% by mass, sufficient conductivity cannot be exhibited. When the amount is more than 70% by mass, the amount of the matrix resin in the film is relatively decreased, and the film is liable to invade cracks during processing, which is not preferable. The amount of the conductive particles is preferably from 30 to 60% by mass, and more preferably from 35 to 55% by mass.

The conductive particles which can be used in the present invention are, for example, metal particles or a conductive layer provided with a metal or the like on the surface of the inorganic or organic polymer particles. As the metal particles, magnetic powder, nickel, or the like can be preferably used from the viewpoint of conductivity and corrosion resistance. When it is necessary to impart electromagnetic wave shielding performance to the metal plate, a magnetic metal powder having excellent conductivity and electromagnetic wave absorptivity can be used as the conductive particles. As such a magnetic metal powder, a carbonyl iron powder, a nickel-iron magnetic conductive alloy (Ni-Fe alloy, a Ni content of 35 mass% or more), and a ferro-aluminum magnetic alloy (Si-Al-Fe system) are suitable. Alloy) and so on.

In order to exhibit high conductivity under light contact pressure, the cumulative 50% volume average particle diameter d50 (μm) of the conductive particles and the thickness t (μm) of the conductive resin film must satisfy the following formula (1), and accumulate The 84% volume average particle diameter d84 (μm), the cumulative 16% volume average particle diameter d16 (μm), and the aforementioned d50 must satisfy the following formula (2).

0.8≦d50/t≦2.0 (1) (d84-d16)/d50≦1.0 (2)

In other words, the cumulative 50% volume average particle diameter d50 (μm) of the conductive particles is in the range of 0.8 times to 2.0 times the thickness t (μm) of the conductive resin film. When the d50/t ratio is smaller than 0.8, the conductive particles are buried in the resin film, and the ratio of the particles above the surface of the film is small, and the conductivity is poor, which is not preferable. On the other hand, when it exceeds 2.0, the ratio of the particles larger than the film thickness increases, and it is not preferable that the particles fall off during the processing of the metal plate or the like. A preferred lower limit of d50/t is 0.9, and a still more preferred lower limit is 1.0. A preferred upper limit is 1.8 and a further preferred upper limit is 1.6. Further, the thickness of the resin film will be described later.

The particle size in the present invention is, for example, a particle diameter measured by a laser diffraction method (scattering type) using a Micro-track particle size distribution measuring apparatus manufactured by Leeds & Northrup. However, assuming a group of powders, the total volume of the group in which the powder is set is 100%, and when the particle diameter is expressed by a cumulative (cumulative) curve on a volume basis, the particle size at a volume fraction of 16% refers to accumulation. The 16% volume average particle diameter d16, the particle diameter at a volume fraction of 50% refers to a cumulative 50% volume average particle diameter d50, and the particle size at a volume fraction of 84% refers to a cumulative 84% volume average particle diameter d84.

The left side of the formula (2) is a value corresponding to the volume average particle diameter d50, and the degree of particle diameter deviation becomes a certain target. The smaller the value on the left side, the narrower the particle size distribution, and the larger the value on the left side, the larger the particle size. The wider the distribution. In the present invention, the value on the left side of the formula (2) is defined as 1.0. If the upper limit is exceeded, the high level of electrical conductivity for the purpose of the present invention cannot be exhibited. Better The upper limit is 0.85 and the further better upper limit is 0.75.

The inventors of the present invention have investigated the relationship between the conductivity under light contact and the particle size distribution of conductive particles required for use in electronic equipment, and found that even if d50 is the same, particle size distribution is used as compared with conductive particles having a wide particle size distribution. One of the narrow conductive particles is more excellent in conductivity. The reason for this is considered as follows. Conductive particles having a large particle size distribution, and particles having a relatively large particle size are mixed with relatively small particles. Further, since the conductive particles having a large particle diameter protrude above the resin film to become an energization point, a certain degree of conductivity can be obtained. However, even if the small particles can sufficiently become a point of energization in relation to the thickness of the film, when the metal plates are in light contact with each other, since the particles having a large particle diameter cause physical obstacles, the so-called energization point cannot be obtained. . Therefore, even when the particle size distribution is wide as the conductive particles of the same d50, it is considered that the absolute number of the conductive particles that can be used as the conduction point is small, and excellent conductivity cannot be obtained. In other words, although the conductive particles having a large particle diameter are energized, there is a negative effect that the effect of blending the conductive particles smaller than the particle diameter is lost. Further, when the conductive particles having a particle diameter smaller than the thickness of the film are contained, the metal plates are in light contact with each other, and since the particles are not exposed beyond the film, they are completely unhelpful in conductivity and become a negative factor.

On the other hand, when the particle size distribution is sharp, since the particles have substantially the same particle diameter, the surface of the film is exposed to the same extent, and the other particles are not physically hindered from being energized, and the conductive particles are large. Part of it functions as a power-on point. Therefore, it is considered to exhibit very excellent electrical conductivity.

In order to narrow the particle size distribution of the conductive particles to be used, it is only necessary to carry out classification using a sieve and a mesh, but it is impossible to remove particles which are too small by using a sieve, and the yield of the product is deteriorated, resulting in high cost. As the classification method which can exclude too small particles, for example, there is a gas classification method, etc., but if such classification is performed, the product yield is further deteriorated, resulting in a relatively high cost. The carbonyl iron powder among the above-mentioned conductive particles can have a sharper particle size distribution than other conductive particles. Therefore, the grading step can be omitted or simplified, thereby contributing to cost reduction, and thus is preferable.

The resin film thickness t is 10 μm or less. If it exceeds 10 μm, the electrical conductivity is lowered, and it is not preferable from the viewpoint of cost. t is preferably 2 to 9 μm, further preferably 3 to 8 μm. t can be measured by a method of converting the specific gravity by the film quality, or can be measured by microscopic observation (SEM observation) of the cross section of the resin film.

Next, a base resin which is a main component of the resin film will be described. In the resin-coated metal sheet of the present invention, a resin film formed by dispersing the conductive particles in a matrix resin is formed on the surface of the metal sheet. As the matrix resin, for example, a polyester resin, an acrylic resin, a urethane resin, a polyolefin resin, a fluororesin, an organic silicone resin, a mixture of these resins or a resin which has been denatured, and the like.

Since the resin-coated metal sheet of the present invention is mainly used in a casing of an electronic device, characteristics such as bending workability, film adhesion, and corrosion resistance are also good. If these are considered, the organic solvent is soluble. A type (non-crystalline) polyester resin is preferred. Polyester tree as an organic solvent soluble The "VYLON (registered trademark) series produced by Toyobo Co., Ltd. is suitable for a wide variety of types. The polyester resin can also be crosslinked by melamine or the like. As a melamine resin, it is produced by Sumitomo Chemical Co., Ltd. The "mismaro (registered trademark)" series and the "saimeru (registered trademark)" series produced by Mitsui Cytec. The crosslinking agent is preferably added in such a manner that the crosslinking agent (after the reaction) in the resin film after drying is preferably added in an amount of 0.5 to 30% by mass (preferably 5 to 25%).

As the original plate of the resin-coated metal sheet of the present invention, an aluminum plate, a copper plate, a cold-rolled steel sheet, a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, an alloyed hot-dip galvanized steel sheet or the like can be used. Among them, a plated alloy steel plate of zinc and an iron group element (Fe, Co, Ni) is preferred. Since these alloyed steel sheets have high hardness as the metal sheets, the pressure applied to the resin-coated metal sheets is not relieved by the deformation of the metal sheets, and the resin film is moderately deformed, so that the contact probability of the conductive particles is further improved. Further, among the plated alloy steel sheets, an alloyed hot-dip galvanized steel sheet (GA steel sheet) having a plating layer in which zinc and iron are alloyed is more preferable. Iron is excellent in electromagnetic wave absorptivity, and iron in plating contributes to absorption of electromagnetic waves. Therefore, when a GA steel sheet is used as an original plate, it is possible to exhibit higher electromagnetic shielding properties.

From the viewpoint of ensuring molding, the Fe, Ni, and Co contents are preferably controlled to be about 5 to 20% by mass. The detailed plating conditions of the melt plating method are not particularly limited, and a method generally employed for alloying can be employed. The amount of plating is preferably small in view of electromagnetic wave absorptivity, and is preferably 50 g/m ² or less, preferably 40 g/m ² or less, more preferably 35 g/m ² or less, and most preferably 30 g/m ² or less. The lower limit of the amount of plating adhesion is not particularly limited from the viewpoint of electromagnetic wave absorptivity, but 5 g/m ^{2 is more} preferable, and more preferably 10 g/m ² , in view of corrosion resistance.

In order to manufacture the resin-coated metal sheet of the present invention, it is preferred to use a raw material composition for preparing a resin film and apply it to a metal plate to dry it. The raw material composition is a base resin, a crosslinking agent added as needed, and the like, and is diluted with an organic solvent or the like to have a viscosity suitable for coating. The organic solvent is not particularly limited, but may be an aromatic hydrocarbon such as toluene or xylene; or an aliphatic ester such as ethyl acetate or butyl acetate. An alicyclic hydrocarbon such as cyclohexane; an aliphatic hydrocarbon such as hexane or pentane; methyl ethyl ketone or cyclohexanone ( Ketones such as cyclohexanone). In consideration of coating suitability, it is recommended that the viscosity of the raw material composition be adjusted by using Ford cup No. 4 for about 30 to 100 seconds, or the solid portion concentration to about 5 to 45% by mass.

In the above-mentioned raw material composition, various known additives used in the field of resin-coated metal sheets such as a matting agent, an extender, a rust preventive, an anti-precipitating agent, and a paraffin may be added as long as the object of the present invention is not impaired. . Further, an additive for imparting heat dissipation properties such as carbon black may be added.

The method of applying the above-mentioned raw material composition to a metal plate is not particularly limited, and a bar coater method, a roll coater method, a sputtering method, and a shower curtain type are used. Curtain flow coater method, etc. Drying is carried out after coating, but in the crosslinking agent addition system, it is preferred to heat dry at a temperature at which the crosslinking agent can react. Specifically, it may be heated at 100 to 250 ° C for about 1 to 5 minutes.

Moreover, for the purpose of improving the corrosion resistance, the adhesion to the resin film, and the like, the metal plate may be subjected to a known surface treatment (underlayer treatment) such as chromate treatment or phosphate treatment. Alternatively, a non-chromate metal plate may be used in consideration of environmental pollution or the like, and any metal plate to which the underlayer treatment is applied is included in the scope of the present invention.

Further, the method of non-chromate treatment is not particularly limited, and known underlayer treatments such as phosphate, cerium oxide, titanium, or zirconium may be carried out singly or in combination. When the underlayer treatment is performed, it is considered that the conductivity is lowered by the underlayer treatment, and the adhesion amount is preferably controlled to 300 mg/m ² or less. In the underlayer treatment film, various known additives used in the field of rust inhibitors and resin-coated metal sheets may be added as needed.

In the resin-coated metal sheet of the present invention, as described above, the resin film containing the conductive particles is laminated to the metal plate via the underlayer treatment or without the underlayer treatment, for example, when used as a casing of an electronic device, the resin film It is used in the way inside the casing. If necessary, in order to improve scratch resistance, fingerprint resistance, and the like, another resin film (upper layer) may be applied to the surface of the resin film. However, it is important that the upper ejection layer is a film which does not hinder the exposure of the conductive particles and does not lower the conductivity, and is specifically 0.2 to 1.5 μm, preferably about 0.4 to 1.2 μm.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples, but the following The invention is not limited to the invention, and various modifications and modifications are possible within the scope of the invention. In addition, in the case of the following special statement, "%" means "% by mass" and "part" means "parts by mass".

<First Embodiment>

First, an embodiment of the first invention described above is shown.

[Metal plate]

The metal plate used and its abbreviation are shown below. Further, plating was performed on both sides of the metal plate.

GA: alloyed hot-dip galvanized steel sheet... thickness; 0.8mm, plating adhesion; single-sided 30g/m ² , amount of Fe in plating; 8.6% EG: electro-galvanized steel sheet... thickness; 0.8mm, plated Adhesive amount; single side 20g/m ² GI: hot-dip galvanized steel sheet... plate thickness; 0.6mm, plating adhesion amount; single side 60g/m ² , Al: aluminum plate... plate thickness; 0.6mm

[Base resin]

The organic solvent-soluble polyester resin VYLON (registered trademark) series manufactured by Toyobo Co., Ltd. is used. Indicates the type of use and Tg.

VYLON 550 (Tg: -15 ° C), VYLON 500 (Tg: 4 ° C), VYLON GK 130 (Tg: 15 ° C), VYLON GK 140 (Tg: 20 ° C), VYLON GK 780 (Tg: 36 ° C), VYLON 296 (Tg: 71 ° C)

[crosslinking agent]

Melamine resin ("mismaro (registered trademark) M-40ST": produced by Sumitomo Chemical Co., Ltd.).

[Electroconductive particles]

. Fe-Ni alloy magnetic powder (Mitsubishi steel made of nickel-iron magnetic alloy; 78Ni-1Mo-FP, average particle size 7.6μm; omitted in the table is Fe-Ni). Nickel powder (Nikko Rica Co., Ltd. made "CNS-10"; average particle size 6.3 μm; omitted in the table as Ni). Iron phosphide (P-Fe-350 produced by Fukuda Metal Foil Co., Ltd. is pulverized to an average particle size of 7.0 μm using a pulverizer)

Further, the average particle diameter of these was a 50% volume average particle diameter measured by a laser diffraction method (scattering type) using a Micro-track FRA9220 manufactured by Leeds & Northrup.

[Preparation of raw material composition for resin film]

Each of the various resins having different Tg and the above-mentioned crosslinking agent (80% solid content) were mixed at a mass ratio of 9:1 to obtain a matrix resin, and the amounts shown in Tables 1 to 10 (content in the resin film w) The conductive particles were added in the form of a carbon black for heat release (manufactured by Mitsubishi Chemical Corporation, particle diameter: 25 nm) at a ratio of 10% in 100% of the solid content of the composition. The xylene/cyclohexanone mixture is used in such a manner that the solid content of the raw material composition is 10 to 30%. The solvent (xylene: cyclohexanone = 1:1) was diluted, and stirred with a hand homogenizer at 10000 rpm for 10 minutes to adjust the raw material composition.

Further, a resin having a Tg of -6 ° C and a mixture of VYLON 550 and VYLON 600 at 85:15 and a Tg of 26 ° C were mixed with VYLON GK 140 and VYLON GK 780 at 63:37. Into.

[Modulation of upper vomit coating]

VYLON 550 and VYLON GK 780 and VYLON 296 having the Tg shown in Table 10 were used. The various resins and the above crosslinking agent were mixed at a mass ratio of 9:1 to a solid concentration of 7.5%, and a xylene/cyclohexanone mixed solvent (xylene:cyclohexanone = 1:1) was used. The dilution was carried out, and the upper layer coating was prepared by stirring at 10,000 rpm for 10 minutes using a manual homogenizer.

[Production of Resin-Coated Metal Sheet]

The material composition for the resin film was applied to various metal plates shown in Tables 1 to 10 by using a bar coater in the form of the film thicknesses shown in Tables 1 to 10, and reached the plate temperature in a hot air drying oven. Baking at 230 ° C for about 120 seconds to prepare a resin coated metal plate.

[Tg measurement]

Differential Scanning Thermal Analyzer based on JIS K 7121 Name: Thermo Plus DSC8230: manufactured by RIGAKU Co., Ltd.). Specifically, a resin coating film was cut from a resin-coated metal plate produced as described above using a cutter knife, and a sample was taken. The sample was placed on a differential scanning calorimeter, cooled to -100 ° C, and heated to 180 ° C at a rate of 20 ° C / min when stable, and the glass transition temperature (Tg) was determined from the obtained DSC curve.

[Measurement and evaluation criteria of conductivity]

The electrical resistance of the surface of the resin-coated metal plate was measured in the following manner using a test apparatus [(Company) Custom Production Analog Tester CX-270N]. As shown in Fig. 1, the angle between the two terminals and the resin film was maintained at 45, and the surface of the resin film was lightly drawn at an average speed of 30 mm/sec. The measurement length was 100 mm. The pressure at the time of measurement was carried out only under the light contact of the terminal weight (7 g). The impedance value is read from the start of the measurement until the measured value (impedance value) is stable for 1 second or more. The measurement position was changed and the operation was performed 10 times in total, and the average value thereof was used as the impedance value. When the impedance value is 500 Ω or less, there is no problem in practical use, and it is ○, and if it exceeds 500 Ω, the conductivity is not good as ×.

[bending workability]

The test piece of the model 2 described in the bending resistance test of JIS K5600-5-1 was subjected to 0T bending (180° bending), and the resin film after bending (the resin film after bending was outside the curved portion) was visually observed. The peeling state is × if peeled off, and ○ if not.

[Scratch resistance]

According to JIS K5600-5-4, the pencil hardness test was carried out, and the pencil using H was not scratched to ○, and the scratched was ×.

Experiment No. 1

The relationship between the Tg of the resin film and the conductivity was investigated. The metal plate was made of GA, and the conductive particles were made of Fe-Ni alloy magnetic powder (average particle diameter r: 7.6 μm). The amount of conductive particles w is constant at 50%, and the thickness t of the resin film is adjusted to about 6 μm and about 9 μm. The measurement results are shown in Table 1. When the Tg of the resin film is in the range of -10 ° C to + 30 ° C, it is understood that the conductivity, the bending workability, and the scratch resistance are all excellent.

Experiment No. 2

Using a resin having a Tg of -6 ° C in a resin film, and a magnetic powder of GA and Fe-Ni alloy, the amount of conductive particles w and the thickness (thickness) t of the resin film are changed to make w. (r/t) change, study the relationship between conductivity and conductivity. The measurement results are shown in Table 2. If w is 20~65%, w. When (r/t) is 36 or more and 200 or less, it turns out that it is excellent in electroconductivity, bending workability, and scratch resistance.

Experiment No. 3

The effect of the type of the metal plate and the type of the conductive particles on the conductivity was examined, and the results are shown in Table 3. Even if the conductive particles are different, the conductivity is not satisfactory when the formula (i) is not satisfied, and even if the metal plate and the conductive particles are different, when the formula (i) is satisfied, it is understood that the conductivity, the bending property, and the scratch resistance are all excellent.

Experiment No. 4

The same experiment as in Experiment No. 2 was carried out using a resin having a Tg of a resin film of 4 ° C, and the results are shown in Table 4. The same tendency as Experiment No. 2 was shown.

Experiment No. 5

Using a resin having a Tg of 4 ° C of a resin film, and experiment No. 3 The same experiment, the results are shown in Table 5. The same tendency as Experiment No. 3 was shown.

Experiment No. 6

The same experiment as in Experiment No. 2 was carried out using a resin having a Tg of a resin film of 15 ° C, and the results are shown in Table 6. The same tendency as Experiment No. 2 was shown.

Experiment No. 7

Using a resin having a Tg of a resin film of 15 ° C, and experiment No. 3 The same experiment, the results are shown in Table 7. The same tendency as Experiment No. 3 was shown.

Experiment No. 8

The same experiment as in Experiment No. 2 was carried out using a resin having a Tg of a resin film of 26 ° C, and the results are shown in Table 8. The same tendency as Experiment No. 2 was shown.

Experiment No. 9

The same experiment as in Experiment No. 3 was carried out using a resin having a Tg of a resin film of 26 ° C, and the results are shown in Table 9. The same tendency as Experiment No. 3 was shown.

Experiment No. 10

Using a resin having a Tg of a resin film of -15 ° C and 36 ° C, the properties satisfying the formula (i) were investigated, and the results are shown in Table 10, but the scratch resistance at -15 ° C was ensured, and the conductivity at 36 ° C was observed. Poor sex.

Further, the properties of the resin film having a Tg of 4 ° C were examined, and the characteristics when the upper film coating film was formed were examined. The results are shown in Table 10. Since the upper layer coating film is a film, it is understood that the conductivity is not adversely affected even if the Tg is high.

<Second embodiment>

Next, an embodiment of the second invention described above will be described.

(Metal plate)

The metal plate used and its abbreviation are shown below. Further, plating was performed on both sides of the metal plate. Further, on the plated steel sheet, "CTE-213" manufactured by Japan Parkerizing Co., Ltd. was used, and the underlayer treatment was carried out at an adhesion amount of 100 mg/m ² .

GA: alloyed hot-dip galvanized steel sheet... thickness; 0.8mm, plating adhesion: single-sided 30g/m ² , amount of Fe in plating; 10.3% EG: electro-galvanized steel sheet... thickness; 0.8mm, plating Adhesion: single side 20g/m ²

[Base resin]

As the base resin, an organic solvent-soluble polyester resin "VYLON (registered trademark) 650" manufactured by Toyobo Co., Ltd. was used. The catalogue value has a Tg of 10 ° C and a molecular weight (Mn) of 23 × 10 ⁴ .

[crosslinking agent]

The melamine resin "mismaro (registered trademark) M-40ST": manufactured by Sumitomo Chemical Co., Ltd., 80% solids).

[Electroconductive particles]

. Carbonyl iron powder (manufactured by BASF: Carbonyl Iron Powder EL: d50 = 5.6 μm, the table is abbreviated as Fe(CO) ₅ ). Fe-Ni alloy magnetic powder (Mitsubishi steel made of nickel-iron magnetic alloy: 78Ni-1Mo-FP; d50 = 7.6μm, omitted in the table as Fe-Ni). Nickel powder (Nikko Rica company made "CNS-10"; d50 = 6.3μm, omitted in the table as Ni). Iron phosphide (P-Fe-350 made by Fukuda Metal Foil Co., Ltd. was pulverized to a d50 of 3.1 μm and classified)

The conductive particles are classified by a sieve after being suitably pulverized, and particles having different particle size distributions (d16, d84) are produced and used. Further, d16, d50, and d84 of these conductive particles were Micro-track FRA9220 (measuring range: 0.12 to 704 μm) manufactured by Leeds & Northrup Co., Ltd. in pure water. The volume average particle diameter (μm) measured by a laser diffraction method (scattering method) in which particles are dispersed.

[Preparation of raw material composition for resin film]

The polyester resin and the above-mentioned crosslinking agent (80% solid content) were mixed at a mass ratio (dry) of 100:20 to form a matrix resin, and were added in the amounts shown in Tables 1 to 3 to have Tables 1 to Conductive particles of a particle size distribution shown in 3. The viscosity of the raw material composition was about 30 to 100 seconds (Ford Cup No. 4), and it was diluted with a xylene/cyclohexanone mixed solvent (xylene: cyclohexanone = 1:1). The hand homogenizer was stirred at 10,000 rpm for 10 minutes to adjust the raw material composition.

[Production of Resin-Coated Metal Sheet]

The film thickness t (μm) shown in Tables 11 to 13 was applied to various metal plates shown in Tables 11 to 13 using a bar coater to coat the raw material composition for the resin film, and was passed in a hot air drying oven. The plate was baked at 230 ° C for about 60 seconds to prepare a resin-coated metal plate. The film thickness t (μm) is a value calculated by measuring the specific gravity of the film.

[Measurement and evaluation criteria of conductivity]

The electrical resistance of the surface of the resin-coated metal plate was measured in the following manner using a test apparatus [(Company) Custom Production Analog Tester CX-250]. As shown in Fig. 1, the angle between the two terminals and the resin film was maintained at 45, and the surface of the resin film was lightly drawn at an average speed of 30 mm/sec. Measurement The fixed length is 100mm. The pressure at the time of measurement was carried out only under the light contact of the terminal weight (7 g). The impedance value is read from the start of the measurement until the measured value (impedance value) is stable for 1 second or more. The measurement position was changed and the operation was performed 20 times in total, and the average value thereof was used as the impedance value. When the impedance value exceeds 100 Ω or less, the conductivity step is preferably ×, more than 50 Ω to 100 Ω is ○, and 50 Ω or less is ◎.

[bending workability]

The test device of model 2 described in the bending resistance test of JIS K5600-5-1 was subjected to 0T bending (180° bending), and the resin film after bending (the resin film was bent outside the curved portion) was attached. Scotch tape (manufactured by Nichiban Co., Ltd.; "Scotch (registered trademark) CT405AP-24" was peeled off by hand, and the peeling state of the film was visually observed. If it was peeled off, it was ×, and if it was not, it was ○.

Experiment 1

As the conductive particles, carbonyl iron powder Fe(CO) _{5 having a} left side of 0.63 in the above formula (2) was used, and the relationship between the addition amount and the characteristics and the relationship between d50/t and characteristics were examined. The measurement results are shown in Table 11. When Fe(CO) _{5 of the} formula (2) is satisfied, when the amount is 20 to 70% by mass, it is understood that the conductivity and the workability can be achieved. Further, in the relationship between the d50 of the conductive particles and the film thickness t, the conductivity was lowered in Nos. 13 and 14 where d50/t was too small. In No. 15 in which d50/t exceeded 2, the workability was poor.

In addition to GA, when using EG (No. 16), it can be seen that it is practical. There is no problem with conductivity and processability.

Experiment 2

As the conductive particles, a nickel-iron magnetic conductive alloy (Fe-Ni) having a 0.87 left side of the above formula (2) was used, and the relationship between the amount of addition and the characteristics was examined. The measurement results are shown in Table 12. When Fe-Ni of the formula (2) is satisfied, when it is added in an amount of 20 to 70% by mass, it is understood that conductivity and workability can be achieved.

Experiment 3

As the conductive particles, a nickel-iron magnetic conductive alloy (Fe-Ni) having a left side of 0.59 on the left side of the above formula (2) was used, and the relationship between the amount of addition and the characteristics was examined. The measurement results are shown in Table 13. The same results as in Experiment 2 were obtained.

Experiment 4

Table 14 shows the results of using the nickel-iron magnetic conductive alloy (Fe-Ni) having the left side of the above formula (2) exceeding 1. Since the formula (2) is not satisfied, the conductivity is not good. On the other hand, Ni which satisfies the formula (2) is known to be electrically conductive and workable. However, it is said that the conductivity is low, and when it is called iron phosphide which is hard to be called conductive particles, conductivity is not obtained. Good result.

The resin-coated metal sheets according to the first and second aspects of the invention are useful as constituent parts of a casing of an electronic device. As an electronic information recording device such as CD, LD, DVD, CD-ROM, CD-RAM, PDP, LCD, etc.; personal computer, car navigation system, car audio-visual equipment, etc. electronic. Communication related products; audio-visual equipment such as projectors, televisions, video recorders, game machines, etc. In addition, it can be used as a component of a copying machine such as a photocopier or a printer, and as a power box cover and a control box cover for an outdoor unit such as an air conditioner, and as a vending machine and a refrigerator. Parts used.

Fig. 1 is an explanatory view of a method of measuring conductivity of a resin-coated metal sheet.

Claims (5)

A conductive resin-coated metal sheet comprising a conductive resin film containing conductive particles on a surface of a metal plate, wherein the conductive resin film contains conductive particles in a range of 20 to 65 mass%, and a conductive resin The Tg of the resin in the film is -10 ° C to +30 ° C, the thickness of the conductive resin film is 1.2 to 14 μm, the content of the conductive particles is set to w (% by mass), and the average particle diameter of the conductive particles is set to r (μm), when the thickness of the conductive resin film is t (μm), the following formula (i), 36 ≦ w × (r / t) ≦ 200 (i) is satisfied, and the above metal plate is alloyed by melt plating Zinc steel plate. The conductive resin-coated metal sheet according to the first aspect of the invention, wherein the resin film is obtained from a raw material composition containing an organic solvent-soluble polyester resin. A conductive resin-coated metal sheet comprising a conductive resin film containing conductive particles on a surface of a metal plate, wherein the conductive resin film contains conductive particles in a range of 20 to 70% by mass, and conductive particles The cumulative 50% volume average particle diameter d50 (μm) and the thickness t (μm) of the conductive resin film satisfy the following formula (1), accumulating 84% volume average particle diameter d84 (μm), accumulating 16% volume average particle diameter d16 (μm) and the aforementioned d50 satisfy the following formula (2), 0.8≦d50/t≦2.0 (1) (d84-d16)/d50≦1.0 (2). The conductive resin-coated metal sheet according to claim 3, wherein the conductive particles are magnetic metal powder. The conductive resin-coated metal sheet according to item 4 of the patent application, wherein the magnetic metal powder is carbonyl iron powder.