JP2008273190A - Resin-coated metal plate excellent in conductivity, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin-coated metal plate which stably exhibits excellent conductivity even under light-contact conditions of a pressure of approximately 10 to 12 gf/mm<SP>2</SP>, whose surface resistance caused by surface contact is stable at low level over the entire region of the large plate, and which is suitable for a component material of large sized electric appliances such as a large-screen display or the like. <P>SOLUTION: The resin-coated metal plate excellent in conductivity, wherein a resin film is formed on the surface of a metal plate, has 10 or more peaks per 2.54 cm (PPI, peak count level 2H=2.54 μm) in the roughness curve (Z(X)) of the resin-coated metal plate and has its Kurtosis (Rku) of 5.0 or less in the roughness curve. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resin-coated metal plate having excellent conductivity and a method for producing the same.

  Conventionally, galvanized steel sheets have been widely used in fields such as home appliances, automobiles, and building materials. In order to improve corrosion resistance, fingerprint resistance, coating film adhesion, etc., the zinc-based plated steel sheet used for these applications is provided with a resin-based film having a thickness of about 1 μm on the surface of the zinc-based plated layer.

  By the way, when this galvanized steel sheet is used for household appliances, it is required that the steel sheet surface has conductivity (grounding) in addition to the above characteristics in order to stabilize the operation of the electronic device and to block noise. The However, since a resin-based film generally has an insulating property, the conductivity of the steel sheet surface decreases due to the formation of the resin film. On the other hand, if the thickness of the resin film is made extremely thin or the resin film is omitted in order to ensure conductivity, the corrosion resistance and fingerprint resistance will be insufficient. In terms of electrical conductivity, due to the increase in the number of complicated parts accompanying the recent downsizing and multi-functionalization of electronic parts and the limitation of space in various devices, only contact with the parts surface or weak spring joints ( Even if it is a light contact), it is required to have conductivity that can secure a sufficient grounding property.

  Various developments are in progress to provide a steel plate having the above characteristics. For example, Patent Document 1 discloses a back surface in which a Ni filler-containing coating film is provided on the back surface of a steel plate whose roughness is controlled to a specific Ra and PPI. A precoated steel sheet having excellent grounding properties is disclosed. Patent Document 2 discloses a metal material with good conductivity in which a predetermined number of protrusions having a height of 0.5 to 30 μm exist within a certain area on the surface of the metal material, and the protrusions have a steep rise. Is disclosed.

However, in the technique of Patent Document 1, since the conductivity of the metal plate is mainly ensured by the Ni filler contained in the coating film, the use of the Ni filler causes deterioration of the corrosion resistance of the metal plate. There is a risk, and further, the cost tends to be high. Further, in Patent Document 2, conductivity is evaluated, but the conductivity is based on the interlayer resistance value defined in JIS C2550 and current weldability. In particular, the measurement of the interlayer resistance value is 2 MPa ± 5. % (About 204 gf / mm ² ) is measured by bringing the terminal into contact with the test piece, and therefore does not satisfy the electrical conductivity under light contact conditions (pressure 10 to 12 gf / mm ² ).

  In addition, Patent Documents 3 and 4 are intended to ensure conductivity under light contact conditions. In Patent Document 3, based on the knowledge that the conductivity is affected by the surface texture of the original plating plate, It has been proposed to perform temper rolling with a roll having a surface roughness Ra and PPI. Patent Document 4 describes that the surface roughness (arithmetic average roughness Ra, filtered centerline waviness Wca) of the surface-treated galvanized steel sheet is appropriately controlled in order to ensure good grounding properties. .

Zinc-based galvanized steel sheets are also used as back panels for plasma displays and liquid crystal televisions. In these applications where screens are becoming increasingly larger in recent years, the back panels are more reliably prevented from leaking electromagnetic waves. (For example, if a 42-inch display is provided, the size of the back panel is approximately 1000 mm × 700 mm). In Patent Document 5, the composition of the alloyed hot-dip galvanized layer is optimized and the surface roughness Ra of the alloyed hot-dip galvanized steel sheet and the surface of the plated layer are provided in order to satisfy the requirements for such advanced electromagnetic wave shielding characteristics. It has been proposed to adjust the coating thickness to an appropriate range.
JP-A-7-265791 JP-A-2005-139551 JP 2005-238535 A JP 2004-277876 A JP 2007-138191 A

  Although Patent Document 3 describes that the conductivity can be improved by using a high PPI plating base plate, what is actually specified is the surface roughness (Ra, Wca) of the rolling roll. There is only. The roughness of the roll is naturally transferred to the surface of the steel sheet to be rolled, but the transfer rate is limited, and the steel sheet surface does not always have the same roughness as the roll. In addition, the PPI on the roll surface is counted at a cut level of ± 0.638 μm, whereas the film thickness of the organic film formed on the steel plate surface is 0.1 to 5 μm. It is also conceivable that there is no projection that can exhibit electrical continuity. In Patent Document 4, Ra and Wca are defined. However, as will be described later, it is possible to grasp whether or not the surface property is such that it can function as a conduction point under light contact as described later. It can be difficult. In addition, the electrical conductivity evaluation method employed in Patent Documents 3 and 4 is not likely to be intended for electrical conductivity under light contact.

As described above, various studies have been made on resin-coated metal sheets for the purpose of ensuring conductivity as well as various properties such as corrosion resistance. However, in recent years, electronic devices are becoming more compact and multifunctional. In fact, a resin-coated metal sheet that can satisfy the electrical conductivity under light contact required for applications such as parts has not been obtained.
In addition, for resin-coated metal plates that satisfy the high-level electromagnetic shielding properties required in applications such as household appliances, which are becoming larger, and the surface resistance due to surface contact is maintained low throughout the entire surface. There was room for consideration.

The present invention has been made paying attention to the circumstances as described above, and the purpose thereof is a resin-coated metal plate that can stably exhibit good conductivity even under light contact at a pressure of about 10 to 12 gf / mm ² . And it is providing the resin coating metal plate suitable also for uses, such as a large screen display, in which the surface resistance by surface contact is maintained at low level over the whole surface.

  The resin-coated metal plate of the present invention that has solved the above problems is a resin-coated metal plate in which a resin film is formed on the surface of the metal plate, and the roughness curve Z (x) of the surface of the resin-coated metal plate , The number of peaks per 2.54 cm (1 inch) (hereinafter simply referred to as “PPI”, the peak count level 2H = 2.54 μm) is 10 or more, and the kurtosis (Rku) in the roughness curve is It has a gist where it is 5.0 or less (the resin-coated metal plate of the first aspect).

  The inventors of the present invention have studied the resin-coated metal plate provided with a resin film of about 1 μm in order to improve the conductivity under light contact. In order to ensure stable conductivity under light contact. Obtained not only the number of irregularities present on the surface of the resin-coated metal plate, but also the difference in height and shape of the irregularities. As a result of further studies based on this knowledge, it has been found that a resin-coated metal plate that satisfies the requirements of the PPI and Rku can provide stable conductivity even under light contact. completed.

  Here, the PPI is a value measured according to the method defined in SAE J911 JUN86 (American Automotive Technical Standard), and exists per unit length in the roughness curve Z (x) of the surface of the resin-coated metal sheet. This indicates the number of peaks and valleys (concave / convex portions) having a predetermined height difference, and is an index representing the surface properties of the resin-coated metal plate. In the present invention, the peak count level 2H at the time of PPI calculation is 2.54 μm.

  On the other hand, the kurtosis (Rku) is a value measured in accordance with the provisions of JIS B0601 (ISO 4287: 1997), and is a peak (convex) existing per unit length in the roughness curve of the surface of the resin-coated metal plate. Part) or valley (concave part).

In the resin-coated metal plate according to the present invention, the average film thickness Y of the resin film on the surface of the resin-coated metal plate is 1.2 μm or less, and the average film thickness Y and the PPI are represented by the following formula (I): It is preferable that the above relationship is satisfied.
Y ≦ 0.003 × PPI + 0.65 (I)

  The resin-coated metal plate has an average film thickness of the resin film of 0.3 μm or more and 1.0 μm or less, and the width direction center point of the surface of the metal plate coated with the resin film and the left and right ends from the width direction center point In the roughness curve of the resin-coated metal sheet measured at a total of three points, two points on the same straight line as the central point separated by 300 mm in the direction of the part, the number of peaks per 2.54 cm (PPI, peak count level) 2H = 2.54 μm) is 40 or more, and the kurtosis (Rku) in the roughness curve is preferably 2.5 ± 0.5 (the resin-coated metal plate of the second embodiment).

If the film thickness of the resin film provided on the resin-coated metal plate and the PPI value and Rku value at any three locations satisfy the above values, the surface by surface contact over the entire area of the resin-coated metal plate surface Resistance is kept low.
Further, the resin film containing an organic resin and inorganic fine particles is a preferred embodiment of the present invention.

  The method for producing a resin-coated metal plate of the present invention is a method for producing the above-mentioned resin-coated metal plate, and in the roughness curve of the roll surface, the number of peaks per 2.54 cm (PPI, peak count level 2H = 2). .54 μm) uses 100 to 300 rolling rolls, and the ratio of unit tension to line load [unit tension / line load] is less than 0.030 to roll a metal plate on which a resin film is formed. Have.

  Furthermore, when the resin coated metal plate is required to have better conductivity (surface resistance is low and stable) over the entire surface, such as for large screen displays, the unit tension ratio [unit tension It is recommended to roll the metal plate with a / line load] of less than 0.028.

Since the resin-coated metal plate of the present invention can exhibit excellent conductivity even when the contact pressure at the joint between the metal plates is small, the resin-coated metal plate is useful as a casing constituent member for electronic devices and the like.
In addition, since the surface resistance due to surface contact is maintained at a low level over the entire surface of the resin-coated metal plate, it is also suitably used for applications such as large screen displays.

  The resin-coated metal plate of the present invention is a resin-coated metal plate in which a resin film is formed on the surface of the metal plate, and 2.54 cm (1) in the roughness curve Z (x) of the surface of the resin-coated metal plate. The number of peaks per inch (PPI, peak count level 2H = 2.54 μm) is 10 or more, and the kurtosis (Rku) in the roughness curve is 5.0 or less. (Resin-coated metal plate of the first aspect). The roughness curve Z (x) is a curve obtained by measurement with a cut-off value of 0.8 mm in accordance with the provisions of JIS B 0601.

  As described above, the PPI indicates the surface property of the resin-coated metal plate. The PPI is a value measured in accordance with the provisions of the SAE standard J911-1986. As shown in FIG. 1, from the average line of the roughness curve Z (x), positive (+), negative (−) A constant level H is provided in each direction (reference level width between positive and negative = 2H), and a positive reference level (+ H, peak portion, diagram) exceeds a negative reference level (−H, valley portion, a in FIG. 1). When a value exceeding b) in 1 is assumed to be “1 count”, it means the number of counts (the number of peak-valley counts) per 2.54 cm (1 inch).

  The reference level width (2H) between positive and negative is called peak count level. In the SAE standard, 2H = 50 μin. In the present invention, 2H = 2.54 μm (100 μin.) Is adopted.

  Conventionally, the arithmetic average roughness Ra of the surface of the metal plate has been used as an index for the conductivity of the metal plate having the resin film. However, with respect to a resin-coated metal plate having a resin film with a film thickness of about 1 μm, when the purpose is to improve conductivity under light contact, the peak-to-valley count (PPI) is more than the arithmetic average roughness Ra. It has been clarified by examination of the present inventors that is more highly correlated with conductivity. The reason why this PPI shows a high correlation with the conductivity of the resin-coated metal plate is considered as follows.

  Usually, the metal plate surface has irregularities derived from its production conditions. On the other hand, although a general resin is an insulator, a film formed on a convex portion on the surface of a metal plate is usually thinner than a concave portion, so that contact between the convex portion and a terminal (such as a ground terminal) It is presumed that this convex portion becomes an energization point and electrical continuity occurs to ensure conductivity. Here, Ra (arithmetic mean roughness) is an index indicating the average of the absolute value of the roughness curve, as shown in the following formula (II), and directly reflects the number of uneven portions present on the surface of the metal plate. It is not a value. For example, assuming that the roughness curve is a triangular wave, the same value is obtained regardless of whether the number of waves per unit length is 1 or 100 as long as the amplitude is the same. At this time, in the former case, since there is only one energization point, it can be easily imagined that it is difficult to achieve electrical conduction compared to the latter case (100 energization points). Therefore, in the case of the above Ra, there is a case where different tendencies are observed in conductivity even with the same value. On the other hand, the PPI represents the number of peaks and valleys that are not less than a predetermined height difference present on the surface of the metal plate as described above, and the measured value indirectly indicates the energization point. Therefore, it is considered that a higher correlation with conductivity is recognized.

  In the present invention, 2H = 2.54 μm (100 μin.) Different from the above-mentioned SAE standard is adopted as the peak count level of the PPI. Until now, even when PPI is used, the peak count level (2H = 1.27 μm) prescribed in the SAE standard is often adopted, and the idea of adopting a different peak count level is that of conductivity. It did not exist when improvement was an issue. However, in the process of studying by the present inventors, in the case of a coated metal plate having a film thickness of about 1 μm, when the peak count level 2H is set to 2.54 μm, the tendency of conductivity can be grasped more stably. Has become clear. Although the clear reason is not certain, the present inventors presume as follows.

  When a resin film is formed on the surface of a metal plate, generally, after the resin composition solution is applied on the metal plate to form a coating film, the film is formed through a drying process in which the water and solvent of the coating solution are evaporated. Is done. In this drying step, the film is leveled (leveled) to some extent, but is not completely leveled, and the surface properties of the coating reflect the properties of the underlying metal plate (such as irregularities). In addition, the present inventors have confirmed through experiments that the arithmetic average roughness Ra is reduced by 10 to 20% before and after the formation of the resin film. Therefore, for example, assuming a resin-coated metal plate having a height difference of 2H = 1.27 μm after film formation, the surface of the metal plate before film formation has 2H = 1.4 to 1.6 μm unevenness. Seems to have existed. Here, assuming that the unevenness on the surface of the metal plate is a triangular wave and the coating film is completely leveled in the drying process, if the average film thickness is 0.7 to 0.8 μm, 2H = 1 before the film formation is calculated. The irregularities observed at .4 to 1.6 μm are buried in the film, and theoretically no irregularities are observed at all after the film is formed. In addition, as described above, in actuality, since the surface property of the film reflects the roughness of the base, there is an uneven portion having a height difference of 2H = 1.27 μm after coating. Although the film is thinner than the average film thickness, it is presumed that there are many cases where there is no convex portion having a function as a conduction point.

  Based on these findings, when a film having an average film thickness of about 1 μm is formed, in order to form a convex portion that can function as a conduction point on the surface of the resin-coated metal plate, It is presumed that the metal plate must have at least 2H = 2 [mu] m or more, and an uneven portion exceeding 2H = 1.6-1.8 [mu] m after film formation. As a result of various experiments conducted in consideration of variations in film thickness during production under such examination, in the present invention, 2H = 2.54 μm (100 μin.) Is adopted as the peak count level.

  The PPI value is 10 or more, preferably 30 or more, and more preferably 40 or more. This is because if the PPI value is too small, the number of energization points for securing conductivity under light contact and maintaining the surface resistance due to surface contact at a low level tends to be insufficient. The upper limit of the PPI value is not particularly limited. However, since the surface property of the metal plate is mainly derived from the surface roughness of the rolling roll at the time of producing the metal plate, the roll roughness is prevented from being lowered, and the roll has a long life. From the viewpoint of achieving the reduction, it is preferably 250 or less. More preferably, it is 200 or less.

  In addition to the PPI value, the resin-coated metal plate of the present invention has a kurtosis (Rku) of 5.0 or less in the roughness curve. In the process of completing the present invention, even when the PPI value satisfies the above numerical range, the inventors may not be able to stabilize the conductivity. The knowledge that the shape of the convex part which exists in the resin coating metal plate surface also affects electroconductivity was acquired.

  Here, the kurtosis (Rku) is a value measured according to the provisions of JIS B0601 (ISO 4287: 1997), and the roughness curve (the height of the mountain) Z (x) at the reference length lr. It is a value calculated by dividing the mean square (the following formula (III)) by the square of the root mean square roughness Rq of the roughness curve (the following formula (IV)).

  This kurtosis (Rku) value represents the kurtosis of the distribution of the probability density function in the roughness curve, and when Rku is 3, it indicates a normal distribution. Moreover, it shows that the peak (mountain or valley) forming the roughness curve has a sharper shape as the Rku value is larger, and that the smaller the Rku is, the smoother the peak is. Shown (see FIG. 2).

  That is, the kurtosis (Rku) value reflects the presence of protruding peaks or valleys (uneven portions) on the surface of the resin-coated metal plate, and Rku is 5.0 or less. This means that the shape of the ridges (valleys) of the concavo-convex part present in the figure is not extremely sharp.

  The reason why Rku is effective as an index of conductivity is not clear, but the present inventors presume as follows. In the conventional conductivity measurement, since the contact pressure is relatively large, when there is a projecting portion protruding on the surface of the resin-coated metal plate, the projecting portion first contacts a terminal (such as a ground terminal). At this time, since the pressing force of the terminal concentrates on the protruding convex portion, the convex portion is thereby crushed. As a result, the terminal or the like is another convex portion (the tip is present below the protruding convex portion). ), And electrical conduction has occurred. That is, in the conventional conductivity measurement, it is considered that the influence of the peak shape appearing on the surface roughness curve was not large because the pressing force of the terminal was sufficiently large.

On the other hand, under light contact, if there is an extremely protruding protrusion, the terminal and the other protrusion (the difference in height between the recess and the protrusion is small, and the protrusion has a tip below the protruding protrusion). As a result, it is estimated that it is difficult to secure a sufficient energization point and a poor conductivity occurs.
Also, when conducting electrical continuity by surface contact, it is considered that the energization point is secured by contact between the terminal (having a certain surface area) and the convex portion on the surface of the resin-coated metal plate. However, when the convex portion is extremely protruding, the film covering the convex portion is deformed and thinned by contact with the terminal, but the deformed film is deposited around the convex portion, and other convex portions ( This hinders contact between the terminal and the terminal (protruding part having a tip below the protruding convex part) and inhibits further pushing of the terminal. Therefore, when there is an extremely protruding protrusion, it is difficult to secure a sufficient energization point, and it is difficult to stabilize the surface resistance due to surface contact at a low level.

  The Rku value is preferably 3.5 or less. On the other hand, the lower limit is not particularly limited, but the Rku value is preferably 2.0 or more. When the Rku value exceeds 5.0, the number of convex portions (concave portions) that are sharper or extremely high is increased, and as a result, the number of convex portions that can function as a conduction point is decreased. It is because there exists a tendency which is inhibited. On the other hand, when the Rku value is too small, the convex portion has a gentle shape, so that the resin film of the convex portion tends to be thick, and there is a possibility that it cannot function as a conduction point under light contact conditions.

  The resin film according to the present invention preferably has an average thickness of 1.2 μm or less. More preferably, it is 0.1-1.0 micrometer, More preferably, it is 0.2-0.8 micrometer. When the resin film is too thick, it tends to be difficult to ensure conductivity under light contact. On the other hand, if it is too thin, it may be difficult to obtain the effects (corrosion resistance, decoration, fingerprint resistance) by providing the resin film.

  The thickness of the resin film can be measured by the following method in addition to the method described in the examples. First, gold (Au) vapor deposition is performed so as to cover the surface of the 20 × 20 mm resin-coated metal plate, and the resin-coated metal plate is embedded in the resin so that the cut surface (end) is exposed, and the resin-coated metal plate is cut. The surface (end cross section) is polished to adjust the measurement sample. Next, an SEM (scanning electron microscope) photograph of the sample surface layer cross section is taken at an acceleration voltage of 20 kV and a magnification of 5000 times, and the resin film thickness is measured from the photograph. Photographing is performed at three arbitrary positions, and the film thickness is measured at three arbitrary positions with respect to one photograph, and a value calculated from the values at a total of nine positions is taken as the average film thickness of the resin.

In the resin-coated metal plate according to the present invention, it is preferable that the average film thickness Y of the resin film provided on the resin-coated metal plate and the PPI satisfy the relationship of the following formula (I).
Y ≦ 0.003 × PPI + 0.65 (I)

  As described above, a general resin exhibits insulating properties, and its thickness greatly affects the conductivity of the resin-coated metal plate. On the other hand, the PPI is the same in that it affects conductivity, and when these two correlations are studied, excellent conductivity is stably obtained when the above relational expression is satisfied. It has been clarified by experiments by the present inventors.

  If there is a high demand for electrical conductivity, especially if you want to maintain low surface resistance due to surface contact over the entire surface of a resin-coated metal sheet cut to a predetermined size (about 700 mm or more), change to the above feature. Therefore, it is recommended to use a resin-coated metal plate having the following characteristics. That is, the resin-coated metal plate of the present invention that can satisfy the requirement for higher conductivity is the center point in the width direction of the surface of the metal plate coated with the resin film and 300 mm in the left and right end directions from the center point in the width direction. In the roughness curve of the resin-coated metal sheet measured at a total of three points, two points existing on the same straight line as the separated center point, the number of peaks per 2.54 cm (PPI, peak count level 2H = 2.54 μm) ) Is 40 or more, and the kurtosis (Rku) in the roughness curve is 2.5 ± 0.5 (resin-coated metal plate of the second embodiment).

  Those satisfying the above PPI value and Rku value can be suitably used for applications such as a rear panel of a large-screen television because the surface resistance due to surface contact can be stably maintained at a low level in any part of the resin-coated metal plate. .

  The PPI value and the Rku value have the same significance as the resin-coated steel sheet of the first aspect. However, in the resin-coated steel sheet of the second aspect, the measurement of the PPI value and the Rku value is as described above. The center point of the resin-coated metal plate, and two points on the same straight line as the center point and separated from the center point by a predetermined distance in the left and right end direction. This is to show that the surface resistance variation on the surface of the resin-coated metal plate is small and that the surface resistance due to surface contact is maintained below a certain level over the entire surface. In addition, it is assumed that the center point and the two points on the left and right end portions are present on the same straight line. Usually, in a metal sheet that has been subjected to a rolling process, the width direction is greater than the length (flow) direction. This is due to the fact that the variation in characteristics tends to increase.

  The PPI value and the Rku value at each point may be measured by taking a sample from an area including the center point or the two points in the left and right end directions, and at an arbitrary position of the sample. A detailed measurement method will be described in detail in Examples.

  In the second resin-coated steel sheet according to the present invention, a total of three points including the center point of the surface of the resin-coated metal sheet on which the resin film is formed and the two points on the left and right ends, regardless of the relationship of the above formula (I). The average film thickness of the resin film is preferably 0.3 μm or more and 1.0 μm or less. More preferably, they are 0.4 micrometer or more and 0.9 micrometer or less, More preferably, they are 0.5 micrometer or more and 0.8 micrometer or less. This is because when the average film thickness of the resin film is less than the above lower limit, the corrosion resistance tends to decrease, whereas when it exceeds the upper limit, it may be difficult to obtain conductivity. Of course, also in the case of the resin-coated metal plate of the second aspect, the relational expression between the average film thickness Y of the resin film of the above formula (I) and the PPI may be adopted as a measure of conductivity.

  As the resin film provided on the resin-coated metal plate according to the present invention, any resin film conventionally used as a resin film of a resin-coated metal plate can be used. Specifically, the base resin which is the main component constituting the resin film according to the present invention includes acrylic resin, melamine resin, phenol resin, epoxy resin, urethane resin, polyester resin, polyamide resin. Alkyd resins, polyolefin resins, silicone resins, fluorine resins, aminoplast resins, vinyl chloride resins, polycarbonate resins and the like. These may be used alone or in combination of two or more.

  As the resin film according to the present invention, among the above base resins, those formed from an emulsion composition of a polyester base resin or a polyolefin resin are preferable.

  As a preferable polyester-based resin, “Byron (registered trademark)” series manufactured by Toyobo Co., Ltd. is preferable in that a wide variety of types can be obtained. The polyester resin may be crosslinked with a melamine resin or the like. As the melamine resin, there are “Sumimar (registered trademark)” series manufactured by Sumitomo Chemical Co., Ltd. and “Cymel (registered trademark)” series manufactured by Mitsui Cytec.

  As a preferable emulsion composition, an ethylene-unsaturated carboxylic acid copolymer (including a neutralized state) is a main component, and 0.2 to An amine having a boiling point of 100 ° C. or less corresponding to 0.8 mol (20 to 80 mol%) and 0.02 to 0.4 mol (2 mol) per mol of carboxyl group of the ethylene-unsaturated carboxylic acid copolymer. To 40 mol%) of a monovalent metal compound corresponding to 2 to 40 mol%, and a cross-linking agent having two or more functional groups capable of reacting with a carboxyl group is added to 0.5 to 100 mass% of the solid content of the emulsion composition. It is preferable that 20% by mass of amine and ammonia having a boiling point of more than 100 ° C. are not substantially contained.

  The resin film obtained from the emulsion composition is excellent in various properties such as corrosion resistance, paintability, lubricity, workability, and grounding properties, and these findings are described in JP-A-2005-264212. Yes.

  The ethylene-unsaturated carboxylic acid copolymer is a copolymer of ethylene and an unsaturated carboxylic acid such as (meth) acrylic acid. A copolymer can be obtained by polymerization by a known high-temperature high-pressure polymerization method or the like. The copolymer is most preferably random, but may be a block copolymer or a copolymer grafted with an unsaturated carboxylic acid moiety. An olefin monomer such as propylene or 1-butene may be used in place of a part of ethylene, and another known vinyl monomer is partially copolymerized (10) as long as the object of the present invention is not impaired. (About mass% or less). The copolymerization ratio of unsaturated carboxylic acid to ethylene is preferably 10 to 40% by mass of unsaturated carboxylic acid when the total amount of monomers is 100% by mass.

  Since the ethylene-unsaturated carboxylic acid copolymer has a carboxyl group, it can be emulsified (aqueous dispersion) by neutralization with an organic base or metal ion. At this time, an amine having a boiling point of 100 ° C. or lower is used as the organic base. Amines having a boiling point exceeding 100 ° C. tend to remain on the steel sheet when the resin coating is dried, and the water absorption of the top coating increases, which may lead to a decrease in corrosion resistance. In addition, the boiling point under atmospheric pressure is employ | adopted for the said boiling point.

  Specific examples of amines having a boiling point of 100 ° C. or lower (hereinafter referred to as the above amines) include 3 such as triethylamine, N, N-dimethylbutylamine, N, N-dimethylallylamine, N-methylpyrrolidine, tetramethyldiaminomethane, and trimethylamine. Secondary amines; secondary amines such as N-methylethylamine, diisopropylamine, diethylamine; primary amines such as propylamine, t-butylamine, sec-butylamine, isobutylamine, 1,2-dibutylpropylamine, 3-pentylamine, etc. 1 type, or 2 or more types can be mixed and used. Of these, tertiary amines are preferred, and triethylamine is the most preferred.

  The amount of the amines is in the range of 0.2 to 0.8 mol (20 to 80 mol%) with respect to 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. This is because the corrosion resistance is good within this range. When the amount of the amines is less than 0.2 mol, the particle size of the resin particles in the emulsion is increased and the above effect is not exhibited. However, when the amount exceeds 0.8 mol, the emulsion composition thickens and gels. This is not preferable because it sometimes occurs. The upper limit of the amount of the amines is more preferably 0.6 mol, still more preferably 0.5 mol, and the lower limit of the amount of the amines is more preferably 0.3 mol.

  Monovalent metal ions are also used for preparing the emulsion composition. Effective for improving solvent resistance and film hardness. The monovalent metal compound preferably contains one or more metals selected from sodium, potassium, and lithium, and a hydroxide, carbonate, or oxide of these metals is preferable. Among these, NaOH, KOH, LiOH and the like are preferable, and NaOH has the best performance and is preferable. Moreover, since the effect by adding a metal compound more than bivalence is not recognized, it is not used.

  The amount of the monovalent metal compound is in the range of 0.02 to 0.4 mol (2 to 40 mol%) with respect to 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. When the amount of the metal compound is less than 0.02 mol, the emulsion stability becomes insufficient. However, when the amount exceeds 0.4 mol, the hygroscopicity (particularly with respect to the alkaline solution) of the resulting resin film increases, and degreasing Since the corrosion resistance after a process may deteriorate, it is not preferable. The lower limit of the more preferable amount of the metal compound is 0.03 mol, and the more preferable lower limit is 0.1 mol. The upper limit of the more preferable amount of the metal compound is 0.3 mol, and the more preferable upper limit is 0.2 mol.

  The preferred ranges of the amounts used of the amines and the monovalent metal compound are as described above, and these are all emulsified by neutralizing carboxyl groups in the ethylene-unsaturated carboxylic acid copolymer. Used to do. Therefore, if the total amount (neutralization amount) is too large, the viscosity of the emulsion composition may rapidly increase and solidify, and excessive alkali will cause corrosion resistance deterioration, and thus volatilize. For this reason, a large amount of energy is required, which is not preferable. However, if the neutralization amount is too small, the emulsifiability is inferior, which is not preferable. Therefore, the total amount of the amines and the monovalent metal compound used should be in the range of 0.3 to 1.0 mol with respect to 1 mol of carboxyl groups in the ethylene-unsaturated carboxylic acid copolymer. preferable.

  In the neutralization step (emulsification step) of the ethylene-unsaturated carboxylic acid copolymer with the above-described amines and monovalent metal ions, an amine having a boiling point of 100 ° C. or less and a monovalent metal compound are almost simultaneously copolymerized. It is desirable that the amine having a boiling point of 100 ° C. or lower is added first. The reason is not clear, but if an amine having a boiling point of 100 ° C. or lower is added later, the effect of improving the corrosion resistance may be insufficient.

  The emulsion composition is blended with a crosslinking agent having two or more functional groups capable of reacting with a carboxyl group. This is because the ethylene-unsaturated carboxylic acid copolymer is chemically crosslinked to improve the film strength. The amount of the crosslinking agent is preferably 1 to 20% by mass (more preferably 5 to 10% by mass) out of 100% by mass of the solid content in the emulsion composition. If it is less than 1% by mass, the effect of crosslinking by chemical bonding becomes insufficient, and the effect of improving corrosion resistance is difficult to be exhibited. On the other hand, when it exceeds 20% by mass, the crosslinking density of the resin film becomes excessively high and the hardness is increased, and cracks occur because it becomes impossible to follow the deformation of the metal plate when performing press working, As a result, corrosion resistance and paintability may be lowered, which is not preferable. In addition, as a ratio of the amount of the crosslinking agent to the ethylene-unsaturated carboxylic acid copolymer, it is desired to appropriately change the amount of the crosslinking agent according to the amount of the carboxyl group in the copolymer. It is preferable to make a crosslinking agent into 0.5-50 mass parts (more preferably 5-20 mass parts) with respect to mass parts.

  Although it does not specifically limit as a crosslinking agent which has two or more functional groups which can react with a carboxyl group in 1 molecule, A sorbitol polyglycidyl ether, (poly) glycerol polyglycidyl ether, a pentaerythritol polyglycidyl ether, a trimethylol propane polyglycidyl Glycidyl group-containing crosslinking agents such as ether, neopentyl glycol diglycidyl ether, (poly) ethylene glycol diglycidyl ether, and polyglycidyl amines; 4,4′-bis (ethyleneiminecarbonylamino) diphenylmethane N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide), toluenebisua Bifunctional aziridine compounds such as lysine carboxamide; tri-1-aziridinylphosphine oxide, tris [1- (2-methyl) aziridinyl] phosphine oxide, trimethylolpropane tris (β-aziridinylpropionate), tris An aziridinyl group-containing crosslinking agent such as a tri- or higher functional aziridine compound such as 2,4,6- (1-aziridinyl) -1,3,5-triazine, tetramethylpropanetetraaziridinylpropionate, or a derivative thereof. Are mentioned as preferred examples, and one or more of them can be used. Of these, aziridinyl group-containing crosslinking agents are preferred. In addition, you may use together polyfunctional aziridine and monofunctional aziridine (ethyleneimine etc.).

  The emulsion composition may contain a wax. When the wax is contained in the range of 0.5 to 20% by mass (more preferably 0.5 to 10% by mass, more preferably 0.5 to 5% by mass) in terms of solid content, Good lubricity, scratch resistance, deep drawability, punchability, mold wear resistance, and blackening resistance of the sliding surface during processing required for pressing and punching. However, if the amount of wax is too large, the wax softens, liquefies or blooms, and concentrates at the interface between the resin film and the post-coating film or between the surface modification layer and the resin film, so corrosion resistance after degreasing, etc. Is not preferable because it deteriorates.

  The wax is not particularly limited, and natural waxes such as microcrystalline wax and paraffin wax; synthetic waxes such as polyethylene; and known waxes such as a mixture thereof can be used. The softening point is preferably selected from 80 to 140 ° C. The most suitable wax is a spherical polyethylene wax, preferably having an average particle size of 0.1 to 3 μm (more preferably 0.3 to 1.0 μm). This is because the lubricity, punchability, mold wear resistance and deep drawability can be significantly improved. As the spherical polyethylene wax, for example, “Daijet E-17” (manufactured by Reciprocal Chemical Co., Ltd.), “KUE-1”, “KUE-5”, “KUE-8” (manufactured by Sanyo Chemical Industries), “Chemipearl ( Registered trademark) "series (Mitsui Chemicals)" W-100 "," W-200 "," W-300 "," W-400 "," W-500 "," W-640 "," W Commercially available products such as “-700” and “Elepon E-20” (manufactured by Nikka Chemical Co., Ltd.) can be suitably used.

  The emulsion composition used in the present invention comprises an essential component, an ethylene-unsaturated carboxylic acid copolymer, the above amines, a monovalent metal compound, a cross-linking agent such as an aziridine compound, and a wax used as necessary. Etc. are preferably included. In the ethylene-unsaturated carboxylic acid copolymer, it is desirable to adjust the amount of other additive components such as an aziridine compound and wax so that these resin components are 50% by mass or more of the solid content of the emulsion composition.

  The emulsion composition is prepared by first charging the essential component ethylene-unsaturated carboxylic acid copolymer together with an aqueous medium into, for example, a homogenizer device, and heating at 70 to 250 ° C. as necessary. Add amines and monovalent metal compounds as appropriate in the form of an aqueous solution (add the amines first, or add the amines and monovalent metal compounds almost simultaneously), high shear Stir with force. Wax, cross-linking agent, etc. may be added at any stage, but it is desirable not to apply heat after the addition of the cross-linking agent so that the cross-linking reaction proceeds and does not gel.

  Moreover, it is a preferred embodiment of the present invention that the resin film contains inorganic fine particles. When inorganic fine particles are contained, the resin film tends to be hard, and when the grounding terminal comes into contact with the resin film, micro-cracks are generated in the vicinity of the inorganic substance, resulting in electrical continuity. Is thought to be easier.

  Preferred inorganic fine particles include silica (silicon dioxide), Ca ion exchange silica, oxides / hydroxides such as Al, Ti, Ce, Sb, Zr, Fe, Sn, Mg, Ca, Zn, phosphoric acid, sulfuric acid, Examples thereof include metal salts such as Al, Mn, Mg, Ca, Ni such as nitric acid and carbonic acid, molybdate, tungstate, vanadate, and phosphomolybdate. These inorganic fine particles preferably have a 50% volume average particle diameter of 1 to 100 nm as measured by a laser diffraction method (scattering method). More preferably, it is 2-20 nm. The amount of the inorganic fine particles is preferably 5 to 80% by mass in the resin film. If the amount of inorganic fine particles is small, the effect of adding inorganic fine particles may be difficult to obtain. On the other hand, if the amount of inorganic fine particles is too large, the amount of resin in the film will be relatively reduced, and the film will easily crack. Tend to be. More preferably, it is 10-75 mass%, More preferably, it is 20-70 mass%.

  Examples of the original plate of the resin-coated metal plate of the present invention include an aluminum plate, a copper plate, a cold-rolled steel plate, a hot-dip galvanized steel plate, and an electrogalvanized steel plate. Among these, zinc-based plated steel sheets are preferable. In particular, in applications where corrosion resistance, appearance beauty, dimensional accuracy, etc. are important in addition to conductivity, electrogalvanized steel sheets are suitable. is there.

  On the other hand, examples of the electrogalvanized steel sheet include an electrogalvanized steel sheet in which zinc and an iron group element (Fe, Co, Ni) are alloyed. From the viewpoint of ensuring moldability, the content of the iron group element is preferably controlled to about 5 to 20% by mass in any case.

The adhesion amount of plating is preferably, for example, 50 g / m ² or less, more preferably 40 g / m ² or less, and still more preferably 35 g / m ² or less. In particular, in the case of an electrogalvanized steel sheet, it is generally 20 g / m ² . But not limited coating weight of the lower limit is particularly from the viewpoint of corrosion resistance, is preferably from 5 g / m ^2, and more preferably 10 g / m ^2.

  Next, the manufacturing method of the resin coating metal plate of this invention is demonstrated. The resin-coated metal plate of the present invention preferably employs a method in which a raw material composition for a resin film is prepared and applied to the metal plate and dried. As the raw material composition, a matrix resin, a crosslinking agent added if necessary, etc. are dispersed in water or diluted with an organic solvent to obtain a concentration or viscosity suitable for coating. The organic solvent is not particularly limited, but aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate and butyl acetate; alicyclic hydrocarbons such as cyclohexane; aliphatic carbonization such as hexane and pentane. Hydrogen etc .; Ketones such as methyl ethyl ketone and cyclohexanone are listed. The solid content concentration of the raw material composition is preferably about 5 to 35% by mass.

  Various known additives used in the field of resin-coated metal plates, such as matting agents, extender pigments, rust preventives, anti-settling agents, and waxes, are added to the raw material composition as long as the object of the present invention is not impaired. May be.

  The method for applying the raw material composition to the metal plate is not particularly limited, and a bar coater method, a roll coater method, a spray method, a curtain flow coater method, or the like can be employed. Although drying is performed after coating, when a crosslinking agent is added, it is preferable to perform drying by heating at a temperature at which the crosslinking agent can react. Specifically, heat drying is preferably performed at 40 to 250 ° C. for about 1 to 60 seconds. The metal plate may be subjected to a known surface treatment (primary treatment) such as chromate treatment or phosphate treatment in advance for the purpose of improving corrosion resistance, improving adhesion to the resin film, and the like. In particular, it is preferable to use a nonchromated metal plate in consideration of environmental pollution and the like.

  In order to obtain a resin-coated metal plate satisfying the above PPI value and Rku value (hereinafter sometimes referred to simply as “surface roughness characteristics”), a metal plate (steel plate or zinc-based material) used as an original plate is used. It is recommended to adopt a method of adjusting the surface roughness in advance during the production of the plated steel sheet. In particular, when an electrogalvanized steel sheet is adopted as the original sheet, the galvanized layer is formed so as to substantially conform to the irregularities on the surface of the steel sheet, so the surface roughness characteristics of the steel sheet forming the galvanized layer should be adjusted in advance. It is preferable to keep it.

  As a specific method for adjusting the roughness characteristics (PPI, Rku) of the surface of the metal plate, the original plate is tandem, reverse-rolled by a rolling roll whose surface is dulled by blasting, electric discharge machining, laser machining, etching, or the like, or Examples thereof include a method of temper rolling, a method of blasting and etching the original plate itself, and the like. In particular, it is preferable to employ a method of subjecting the annealed metal sheet to temper rolling under conditions corresponding to the sheet thickness after cold rolling and employing a rolling roll having a specific PPI value.

  As the rolling roll, it is preferable to use one having a roll surface PPI value (peak count level 2H = 2.54 μm) of 100 to 300. More preferably, the PPI value is 190 or more. The PPI value on the roll surface is preferably adjusted by applying electric discharge machining to the roll surface.

Moreover, as conditions at the time of temper rolling, for example, when the thickness of a metal plate (steel plate) is 0.4 to 2.0 mm, the rolling reduction is 0.5 to 3% (more preferably 0.8 to 2.5%), unit tension of 1 to 15 kgf / mm ² (more preferably 3 to 13 kgf / mm ² ), and linear load of 100 to 650 kgf / mm (more preferably 150 to 600 kgf / mm) are recommended. . In particular, it is recommended that the ratio of unit tension to line load [unit tension / line load] be less than 0.030.

  The unit tension means a force by which the metal plate is pulled in the traveling direction during rolling, and the line load means a force applied to the metal plate by the roll. That is, [unit tension / line load] <0.030 means that the line load is larger than the unit tension (or the unit tension is smaller than the line load). While the pressure applied to the plate is large, the tension acting in the traveling direction of the metal plate is small and the variation in the plate thickness is small, so it can be said that the surface property of the rolling roll is easily transferred to the metal plate. In particular, when high conductivity is required, for example, when it is desired to obtain sufficient conductivity by surface contact, the ratio of the unit tension to the line load is preferably 0.028 or less, more preferably 0.8. 025 or less.

  The temper rolling is performed by passing an original plate used for a resin-coated metal plate through a temper rolling mill. A general temper rolling mill includes several upper and lower rolling rolls as shown in FIG. These rolling rolls are supported by a stand at both ends of the roll, and when the original plate passes between the upper rolling roll and the lower rolling roll, in the stand, by applying hydraulic pressure to the lower rolling roll, The load during rolling can be adjusted. In addition, the tension (flow direction) applied to the original plate applies a pulling force to the original plate between the bridle rolls by applying a rotational speed difference to the bridle roll installed on the entrance side and the outgoing side of the original plate in the temper rolling mill. Can be adjusted. Therefore, the rolling reduction, unit tension, and line load can be adjusted by controlling the hydraulic pressure in the stand and the pulling force by the motor.

  In addition, the line load is obtained by measuring the load applied to the lower rolling roll on each of the both sides of the temper rolling mill with a load meter (load cell), adding them, and dividing by the width of the original plate. Calculated. The rolling reduction is measured by measuring the length between the creases on the exit side of the temper rolling mill by placing two crease lines at 1000 mm intervals in the length direction on the surface of the original sheet on the entrance side of the temper rolling mill. Then, it is calculated by substituting the obtained value into the following equation.

  The unit tension is calculated by measuring the tensile force applied between the bridle rolls with a tension meter and dividing the obtained value by the cross-sectional area of the steel plate.

  The steel sheet tempered and rolled as described above may be directly used for forming a resin film, but it is preferable to provide a plating layer on the surface for the purpose of improving corrosion resistance and the like. For example, in the case of performing electroplating, an energized portion composed of a combination of a metal conductor roll and a rubber backup roll provided above and below so that a steel sheet that is transported horizontally is sandwiched between tempered steel sheets. Pass through the horizontal electroplating equipment provided. In the horizontal electroplating apparatus, the surface of the metal plate is subjected to alkaline scrubber degreasing, electrolytic degreasing, water washing, and sulfuric acid washing, and then subjected to cathodic electrolysis in a metal plating bath to form a plating layer. Next, after the surface is washed with water, the resin coating material is provided with a resin film on the surface of the plating layer by applying the raw material composition of the resin film with a roll coater or the like, evaporating and drying the solvent (water) with a dryer. A board is obtained.

  The resin-coated metal plate of the present invention has the above-mentioned surface roughness characteristics. For example, when used as a casing of an electronic device, the surface having the specific surface roughness characteristics is used inside the casing. .

  Hereinafter, the present invention will be described in more detail with reference to examples.However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

Experimental Examples 1-30
The low carbon Al killed steel was cold rolled to a thickness of 0.5 mm, 0.8 mm, and 1.0 mm, then degreased, washed, and annealed, and temper rolled under the conditions shown in Table 1. The PPI of the rolling roll used at this time is also shown in Table 1.

  Next, the steel sheet after temper rolling was passed through a horizontal electroplating apparatus, and electrogalvanized in the following steps. The amount of galvanized adhesion is as shown in Table 2.

(I) Alkaline scrubber degreasing step: The surface of the steel sheet was degreased at 60 ° C. using a 3% sodium orthosilicate aqueous solution.
(Ii) Electrolytic degreasing and rinsing step: Using a 3% sodium orthosilicate aqueous solution, electrolytic degreasing of the steel sheet surface was performed at 60 ° C. and 20 A / dm ² , followed by washing with water.
(Iii) Pickling and rinsing steps: The steel sheet was pickled at room temperature using a 5% sulfuric acid aqueous solution and then washed with water.
(Iv) Electrogalvanization and water washing process: Electrogalvanization was performed according to the following plating solution composition and conditions, and then washed with water.
・ Plating solution composition:
ZnSO ₄ .7H ₂ O: 300 to 400 g / l
Na ₂ SO ₄ : 50 to 100 g / l
H ₂ SO _4: 25~35g / l
Current density: 50 to 200 A / dm ²
・ Plating solution temperature: 60 ℃
・ Plating solution flow rate: 0.8 to 2.4 m / sec
Two types of films (film A and film B) having different compositions were formed on the surface of the obtained galvanized steel sheet.

[Film A (organic film)]
After the electrogalvanizing and rinsing steps, a treatment liquid A having the following composition was applied to the dried electrogalvanized steel sheet by a bar coating method and baked. Table 2 shows the average film thickness of the film A after baking. The composition and baking conditions of the treatment liquid A used at this time are shown below (resin type: A).

  Preparation of treatment liquid A: 20% by mass of melamine-based cross-linking agent (“Summar ( (Registered trademark) M-40ST "; manufactured by Sumitomo Chemical Co., Ltd.) was added, and this was diluted with a mixed solvent of xylene and cyclohexanone (1: 1 (mass ratio)) to prepare treatment solution A. The solid content of the obtained treatment liquid A was 10% by mass.

  -Baking conditions: After the obtained treatment liquid A was applied to the surface of the steel sheet dried by electrogalvanizing and rinsing with a bar coating method, the in-furnace time in the hot air drying furnace was 50 seconds, and the ultimate plate temperature was 230 ° C. It dried on conditions, and the membrane | film | coat A was formed on the steel plate (No. 1-2).

[Coating B (Organic inorganic composite coating)]
The treatment liquid B (emulsion composition) was applied to the steel sheet after the electrogalvanization and water washing steps by a roll coating method, and then the water was evaporated and the coating film was dried. Table 2 shows the average film thickness after drying. The treatment liquid B was prepared as follows, and the film was dried according to the following conditions.

  Preparation of treatment liquid B: In an autoclave, 626 parts by mass of water (hereinafter simply referred to as “parts”), 160 parts of an ethylene-acrylic acid copolymer (acrylic acid 20% by mass, melt index (MI) 300) And 40 mol% triethylamine and 15 mol% NaOH are added to 1 mol of the carboxyl group in the ethylene-acrylic acid copolymer, and the mixture is stirred at a high speed in an atmosphere of 150 ° C and 0.5 MPa. An ethylene-acrylic acid copolymer emulsion was obtained. Next, 5% by mass (emulsion composition) of 4,4′-bis (ethyleneiminocarbonylamino) diphenylmethane (“Chemite (registered trademark) DZ-22E”; manufactured by Nippon Shokubai Co., Ltd.) as a cross-linking agent was added to this emulsion. The solid content of the product is 100% by mass, the same shall apply hereinafter) and a glycidyl group-containing compound ("Epiclon (registered trademark) CR5L" (hereinafter abbreviated as "CR5L"); manufactured by Dainippon Ink & Chemicals, Inc.). Spherical polyethylene having a solid content of 5% by mass and silica particles having a particle size of 10 to 20 nm (“Snowtex 40”; manufactured by Nissan Chemical Industries Ltd.) with a solid content of 30% by mass, a softening point of 120 ° C. and an average particle size of 1 μm. A wax (“CHEMIPARL (registered trademark) W-700”; manufactured by Mitsui Chemicals, Inc.) was blended so that the solid content was 5% by mass and stirred. Composition (treatment solution B) was prepared. The solid content of the obtained emulsion composition was 15% by mass.

  -Drying conditions: After applying the obtained emulsion composition to the steel sheet after the electrogalvanizing and rinsing steps by a roll coating method, the air temperature is 200 ° C., the wind speed is 53 m / sec, and the drying time is 1 to 2 seconds. It dried and formed the organic inorganic composite membrane | film | coat on the steel plate (No. 3-30).

  The obtained resin-coated metal sheet test materials were evaluated according to the following evaluation methods, and the results are shown in Table 2. Moreover, the relationship between a film thickness, PPI value, and the electroconductivity of a resin coating metal plate is shown in FIG. In FIG. 1-2 and ● are No. 3-18 and ▲ are No. 19-25, x is No .. The result of 26-30 is shown.

[Evaluation methods]
(1) PPI
PPI was measured in accordance with SAE (Society of Automotive engineers) J911-1986. The peak count level 2H = 2.54 μm. For the measurement, a surface roughness shape measuring instrument (“Surfcom 1400A-3DF”; manufactured by Tokyo Seimitsu Co., Ltd.) was used. In addition, the small surface roughness measuring device ("Surf Test SJ-301"; Mitutoyo Corporation) was used for PPI measurement of the roll surface used at the time of temper rolling. Measurement was obtained with a cut-off value of 0.8 mm, stylus tip radius R: 2 μm (the stylus part is regarded as a sphere), measurement length: 25.4 mm (in the case of a roll, the measurement length was 4 mm) The value was converted into a value when the measurement length was 25.4 mm.). The measurement place is two places in the same direction on the surface of the resin-coated metal plate, and two places in the direction perpendicular to the direction (in the case of a roll, only in the width direction), the average value is calculated, and the surface of the film, or The PPI on the roll surface was used.

(2) Kurtosis (Rku)
Cultosis (Rku) was measured in accordance with JIS B0601 (ISO 4287: 1997). As a measuring device, a surface roughness shape measuring machine ("Surfcom 1400A-3DF", manufactured by Tokyo Seimitsu Co., Ltd.) was used as in the PPI measurement. The measurement conditions were a cut-off value of 0.8 mm, a stylus tip radius R: 2 μm (the stylus part is regarded as a sphere), and a measurement length: 25.4 mm. Moreover, the measurement place was two places in the same direction and two places in the direction perpendicular | vertical to the said direction, the average value was computed and it was set as Rku of the film | membrane surface. In addition, Kurtosis measured only about the organic resin film steel plate.

(3) Zinc adhesion amount Using a fluorescent X-ray analyzer ("MXF-2100"; manufactured by Shimadzu Corporation), the zinc adhesion amount on the metal plate was measured. In measuring the zinc adhesion amount, a calibration curve representing the relationship between the zinc content and the fluorescent X-ray intensity was prepared in advance, and the zinc adhesion amount was determined based on this calibration curve.

(4) Average thickness of resin film (4-1) For film A, the film A was swollen with a solvent (N-methyl-2-pyrrolidone) and removed from the surface of the steel sheet, and the mass of the steel sheet before and after film A was removed. The amount of resin adhesion was calculated from the difference and the peeled area of the film, and the value obtained by dividing this by the specific gravity of the resin A was taken as the average thickness t (μm).

  (4-2) For coating B, the amount of Si derived from silica particles (silicon dioxide) contained in coating B was measured by fluorescent X-ray analysis. As the fluorescent X-ray analyzer, “MXF-2100” manufactured by Shimadzu Corporation was used. In measuring the Si content, a calibration curve representing the relationship between the Si content and the fluorescent X-ray intensity was prepared in advance, and the Si content in the film was determined based on this calibration curve. Based on the value of the obtained Si content (fluorescence X-ray value), the specific gravity was converted to calculate the mass of the coating B, and the average thickness t (μm) was obtained. The specific conversion method is as follows.

[Si / SiO ₂ ] = 28/60
SiO ₂ mass ratio = 0.3

(5) Conductivity tester (made by Custom Co., Ltd., “Multi Tester CX-250”) was used to measure the resistance of the resin-coated metal plate surface according to the following procedure. As shown in FIG. 4, the measurement was performed by sliding the two terminals in the length direction of the test piece at an average speed of 10 mm / second while keeping the angle with the resin film at 45 °. The pressure at the time of measurement was performed under light contact of only the terminal's own weight (7 g, pressure: about 11 gf / mm ² ). When the measured value (resistance value) was stabilized after 1 second or more from the start of measurement, the resistance value was read. This operation was performed 5 times in total at different measurement locations, and the average value was taken as the resistance value. The case where the resistance value was 50Ω or less was evaluated as good, 100Ω or less was good, 200Ω or less was acceptable, and the case where the resistance value was more than 200Ω was evaluated as defective.

  From Table 2, no. It can be seen that 1 to 25 resin-coated metal plates all have a PPI value of 10 or more and a kurtosis (Rku) of 5 or less, indicating good conductivity. In particular, the average film thickness Y and the PPI value of the resin film satisfy the relationship of the formula (I) (Y ≦ 0.003 × PPI + 0.65), and the resin film contains an organic resin and inorganic fine particles. It can be seen that particularly good conductivity is easily obtained.

  In contrast, no. The resin-coated metal plates of 26 to 28 have Rku of more than 5, and although there are convex portions on the surface of the resin-coated metal plate, they are not shaped to contribute to conductivity, so conductivity is obtained. It is thought that there is nothing. No. In the examples of 29 and 30, it can be considered from the Rku value that the shape of the convex portion can contribute to the conductivity, but since the number of convex portions is small (PPI value is less than 10), the energization point is small and good. It is considered that conductivity was not obtained.

  Moreover, it can be seen from Table 1 that a resin-coated metal sheet having a preferable PPI value and Rku value can be obtained by setting the unit tension / line load to less than 0.030.

Experimental Examples 31-49
Low-carbon Al killed steel is cold-rolled to a width of 1200 mm and a thickness of 0.5 mm, 0.8 mm, and 1.0 mm, and then degreased, washed, and annealed, and conditioned under the conditions shown in Table 3. Rolled. The PPI of the rolling roll used at this time is also shown in Table 3.

The temper rolling was performed by passing the steel sheet having the above-mentioned width and thickness through a temper rolling mill provided with a roll of 4 stages in total, 2 upper stages and 2 lower stages (see FIG. 5). At the time of rolling, in the stand that supports the roll provided in the temper rolling mill from both sides, the line load applied to the steel sheet by the roll was adjusted by applying hydraulic pressure to the lower roll.
The rolling reduction is calculated from the following equation by putting two crease lines at 1000 mm intervals in the length direction on the steel sheet surface at the entrance side of the temper rolling mill, and measuring the length between the crease marks at the exit side. did.

  The tension was adjusted by applying a tensile force with a motor between bridle rolls installed on the entry side and exit side of the temper rolling mill. The unit tension was calculated by measuring the tensile force applied to the bridle roll with a tension meter and dividing by the cross-sectional area of the steel plate.

Next, electrogalvanization was applied to the steel sheet after temper rolling under the same conditions as in Experimental Examples 1 to 30 (adhesion amount of galvanization: 20 g / m ² ).

  After apply | coating the said process liquid B to the surface of the obtained galvanized steel plate by the roll coat method, the water | moisture content was evaporated and the coating film was dried and the resin coated steel plate which has an organic inorganic composite film was obtained (No .31-49). Tables 4 and 5 show the average film thickness after drying. In addition, the conditions similar to Experimental Examples 3-30 were employ | adopted for preparation of the process liquid B and the drying conditions of a film | membrane.

  A large plate sample of 1200 mm (width direction) × 500 mm (length direction) is taken from the coil of the resin-coated steel sheet having the obtained organic-inorganic composite film, and further, the width direction center part and the left and right ends from the center part Samples of 50 mm (width) x 120 mm (length) were collected from a total of two points that are on the same line as the central part separated by 300 mm in the direction of the part, and according to the above evaluation method, PPI, kurtosis, zinc adhesion amount And the average thickness (4-2) of the resin film was evaluated. The surface resistance and corrosion resistance were evaluated according to the following evaluation methods.

(6) Surface resistance Low resistivity meter (Loresta EP [MCP-T360], ESP probe (4-terminal 4-probe system, electrode (probe) diameter: 2 mm (electrode tip is flat), electrode interval: 5 mm)); Mitsubishi Chemical The surface resistance was measured 5 times (5 places) by changing the location in each sample, and the largest measured value was used as a representative value and evaluated according to the following criteria.
◎ (excellent): 1 mΩ or less ○ (good): 1 mΩ or more, 50 mΩ or less × (defect): 50 mΩ or more

(7) Evaluation of corrosion resistance A sample of 50 mm x 120 mm was taken, the back and ends were sealed with tape, a salt spray test was conducted in accordance with JISZ 2371, and the white rust occurrence rate was observed at a test time of 168 hours , Calculated and evaluated according to the following criteria.

◎ (good): 1% or less ○ (possible): more than 1%, 5% or less × (defect): more than 5%

In Tables 4 and 5, L, C, and R indicate samples collected from the left end (L), center (C), and right end (R) of the resin-coated steel sheet.
From Table 4, No. The resin-coated metal plates 31 to 41 have a PPI value of 40 or more and a kurtosis (Rku) in the range of 2.5 ± 0.5 at any location of the measurement sample. It can be seen that the surface resistance due to surface contact is maintained at a low level.

  In contrast, no. The resin-coated metal plate No. 42 has a convex portion on the surface, but there were places where the upper limit of the film thickness was partially exceeded in the plane (No. 42-L and R), so that the surface was low and stable in the plane. The surface resistance due to contact could not be obtained. No. The resin-coated metal plate No. 43 had a low surface resistance in the surface of the resin-coated metal plate and was stable, but had a thin resin film and poor corrosion resistance. No. The resin-coated metal plates 44 to 49 have a PPI value of less than 40, and the number of convex portions on the surface of the resin-coated metal plate is small and there are few energization points, or there are locations where the Rku value exceeds 3. Although there is a convex part on the surface of the resin-coated metal plate, it is not a shape that can contribute to conductivity when brought into surface contact, so it is due to low and stable surface contact over the entire surface of the resin-coated metal plate. It is considered that the surface resistance was not obtained.

  Moreover, it can be seen from Table 3 that a resin-coated metal plate having a preferable PPI value and Rku value can be obtained by setting the unit tension / line load to less than 0.028.

The resin-coated metal plate of the present invention exhibits excellent conductivity even under light contact conditions of a pressure of about 10 to 12 gf / mm ² , and further, the surface resistance due to surface contact is low and stable over the entire large plate. Therefore, it is suitably used as a housing material for electronic equipment, electrical equipment, optical equipment, and a constituent material of home appliances (particularly a rear panel of a large screen display).

It is a figure for demonstrating the concept of PPI. It is a figure for demonstrating the concept of Rku. It is a figure which shows the relationship between a film thickness, PPI value, and the electroconductivity of a resin coating metal plate based on the result of an Example. It is a figure which shows the method of the electroconductivity test employ | adopted in the Example. It is a figure which shows the manufacturing method of the metal plate which concerns on this invention.

Claims (6)

A resin-coated metal plate in which a resin film is formed on the surface of the metal plate,
In the roughness curve of the resin-coated metal plate, the number of peaks per 2.54 cm (PPI, peak count level 2H = 2.54 μm) is 10 or more, and
A resin-coated metal plate having excellent conductivity, wherein kurtosis (Rku) in the roughness curve is 5.0 or less. The average film thickness Y of the resin film on the surface of the resin-coated metal plate is 1.2 μm or less, and the average film thickness Y and the PPI satisfy the relationship of the following formula (I). Resin coated metal plate.
Y ≦ 0.003 × PPI + 0.65 (I) A resin-coated metal plate in which a resin film is formed on the surface of the metal plate,
The average film thickness of the resin film is 0.3 μm or more and 1.0 μm or less,
Measured at a total of three points: a center point in the width direction of the surface of the metal plate coated with the resin film and two points on the same straight line as the center point separated from the center point in the width direction by 300 mm in the left and right end directions. In the roughness curve of the resin-coated metal plate, the number of peaks per 2.54 cm (PPI, peak count level 2H = 2.54 μm) is 40 or more, and
The resin-coated metal sheet according to claim 1, wherein kurtosis (Rku) in the roughness curve is 2.5 ± 0.5.   The resin-coated metal plate according to claim 1, wherein the resin film contains an organic resin and inorganic fine particles. A method for producing a resin-coated metal sheet according to any one of claims 1, 2, or 4,
In the roll surface roughness curve, use a roll having 100 to 300 peaks per 2.54 cm (PPI, peak count level 2H = 2.54 μm),
A method for producing a resin-coated metal sheet, comprising rolling a metal sheet on which a resin film is formed with a ratio of unit tension to line load [unit tension / line load] being less than 0.030. A method for producing a resin-coated metal plate according to claim 3 or 4,
In the roll surface roughness curve, use a roll having 100 to 300 peaks per 2.54 cm (PPI, peak count level 2H = 2.54 μm),
A method for producing a resin-coated metal sheet, comprising rolling a metal sheet on which a resin film is formed with a ratio of unit tension to line load [unit tension / line load] being less than 0.028.