JP2006097127A - Scratch-resistant precoated metallic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precoated metallic sheet which scarcely causes a scratch on an optical disk even when the disk comes into contact with a protrusion of the inner surface of a drive of an electric or electronic device. <P>SOLUTION: This scratch-resistant precoated metallic sheet is a metallic sheet such as an aluminum alloy sheet with a chemical conversion film on the one surface thereof, wherein the film comprises a base resin, a bead resin, and a lubricant and has an arithmetic mean roughness Ra of 1.3 to 6.2 μm, an average length RSm of a profile curve element of 300 to 550 μm, and a coefficient of dynamic friction of 0.20 or lower. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pre-coated metal plate used for a casing of an electric device or an electronic device such as a liquid crystal television or a personal computer, and is a scratch-resistant pre-coat that hardly damages the optical disk even if the optical disk such as a CD or DVD contacts the inner surface. It relates to a metal plate.

  In recent years, the development of optical disks and drives such as CDs and DVDs has progressed, and the slot-in type in which the optical disk itself is inserted into the drive housing has begun to spread. As such a casing, a metal plate such as a pre-coated aluminum alloy plate is often used. In the slot-in type drive, when the distance between the optical disc and the convex portion on the inner surface of the housing is narrow, the optical disc and the convex portion may collide due to the thickness accuracy of the optical disc itself or the bending during operation of the optical disc. Further, if an unexpected shock is applied to the drive during reproduction or recording of the optical disk, the optical disk may come into contact with the inner surface of the housing. Furthermore, when the optical disk is tilted by a human hand and inserted into the drive, the optical disk may come into contact with the convex portion on the inner surface of the housing.

  Various types of optical discs have been developed. Even if the surface of the optical disc is slightly scratched, there are some that adversely affect the reproduction and writing of the recording. Therefore, when the optical disk is damaged as described above due to the contact between the optical disk and the convex portion on the inner surface of the housing, there is a problem that the optical disk cannot be used.

In order to prevent the occurrence of such scratches, in Patent Document 1, the surface of a member that may contact or come into contact with the optical disk in the optical disk apparatus is based on urethane resin and includes at least polyurethane particles and fluororesin powder. It has been proposed to prevent the optical disk from being damaged by forming a protective film.
JP 2003-242703 A

  However, since this scratch-resistant coating uses a flexible urethane resin as the base resin, the coating is deformed when the optical disc and the scratch-proof coating are in contact with each other, and the contact area between the coating and the optical disc is different from that of the other. As compared with the case of using the above resin. Since the increase in the contact area impairs the scratch resistance, a large amount of polyurethane particles as much as 20 to 150 parts by weight with respect to 100 parts by weight of the base resin is added to the film to reduce the contact area. . As described above, in a film containing a large amount of polyurethane particles, the polyurethane particles easily fall off from the film at the time of molding, and as a result, there is a problem that the effect of preventing scratches due to the addition of polyurethane particles is not fully exhibited.

  Moreover, in patent document 1, in order to provide slipperiness to the coating surface as a scratch-preventing property, low-friction fluororesin powder is added to the coating as a large amount component of 10 to 150 parts by weight with respect to 100 parts by weight of the base resin. It is necessary to add. Since such a film contains a large amount of fluororesin powder, an increase in material cost cannot be avoided, and there is also a problem that winding becomes difficult because the film slips during coil-up. In order to deal with such a problem, there is also a method of forming an anti-scratch coating by post coating. However, in the film formation by post-coating, since a film having a certain film thickness must be applied to the convex portion for each molded product, there remains a problem that the process becomes complicated and an increase in manufacturing cost cannot be avoided.

  Furthermore, in the coating film of Patent Document 1, since the fluororesin powder remains softened without being liquefied at the baking temperature of the coating film (temperatures of 80 ° C. and 140 ° C.), it has sufficient permeability to the base resin. It is not obtained and dispersion unevenness is likely to occur locally. As a result, there is a problem that unevenness occurs in slipperiness.

Moreover, it is a pre-coated aluminum alloy plate used for a casing of an electronic device such as a personal computer, and is intended to prevent the casing itself from being damaged during molding processing or contact with other parts. Has also been proposed (Patent Document 2). The resin coating film to be precoated contains a base resin such as a polyester resin, beads such as an acrylic resin, and an inner wax such as polyethylene wax. However, this coating film is thought to prevent itself from being damaged by the combination of the non-flexible base resin and the non-flexible beads, and does not prevent the counterpart optical disc from being damaged. That is, this coating film is made hard by adding beads to the resin, and further added inner wax to impart lubricity, so that it is difficult to scratch the coating film during press molding. It is a thought. Therefore, it is mainly taken into consideration that the required performance on the outside of the housing is satisfied, and the required performance on the inside surface of the housing as in the present invention is prevented from being damaged. Does not take into account. As a result of evaluating the scratch resistance of the coating film obtained by adding acrylic beads and carnauba wax to the polyester resin, the present inventors have confirmed that the optical disk is severely damaged.
JP 2004-98624 A

  The present invention is a pre-coated metal plate that is currently widely used as a housing for electrical and electronic equipment, and has excellent scratch-proofing properties for optical discs, good winding properties when coiling up, and low manufacturing costs. Furthermore, it aims at providing the precoat metal plate which does not have non-uniformity in slipperiness.

The present invention according to claim 1, wherein the chemical conversion film formed on both surfaces of the metal plate,
At least one base resin selected from the group consisting of a polyester resin, an epoxy resin and an acrylic resin; a nylon resin bead and a fluorine resin; A coating comprising: at least one resin bead selected from the group consisting of beads and urethane-based resin beads; and at least one lubricant selected from the group consisting of carnauba wax, polyethylene wax and microcrystalline wax. With a membrane,
The arithmetic average roughness Ra of the coating film is 1.3 to 6.2 μm, the average length RSm of the contour curve element is 300 to 550 μm, and the dynamic friction coefficient Kf on the coating film surface is 0.20 or less. A scratch-resistant precoated metal plate characterized by the above was obtained.

  According to a second aspect of the present invention, the resin beads have an average particle size Pd of 10 to 100 μm, and the resin beads are contained in an amount of 2 to 12% by weight based on the base resin of the coating film.

  The present invention according to claim 3, wherein at least one lubricant selected from the group consisting of the carnauba wax, polyethylene wax and microcrystalline wax is 0.2 to 10% by weight based on the base resin of the coating film. It was made to contain.

  In the present invention, the scratch-resistant pre-coated metal plate is a conductive resin film formed on the other of the chemical conversion film, and the silver probe is brought into contact with a contact load of 100 g by a four-terminal method. A conductive resin film having an electric resistance value Er of 10Ω or less is further provided.

  In the present invention, the scratch-resistant pre-coated metal plate is a resin film formed on the other of the chemical conversion film, and is a fluorine resin, an epoxy resin, a polyester resin, an acrylic resin, a urethane resin. A heat-dissipating and conductive resin film further comprising: at least one base resin selected from the group consisting of resins; a heat-dissipating material containing at least graphite; and a conductive material containing at least nickel powder. .

  In the present invention, since a non-flexible resin such as polyester is used as the base resin, there is almost no deformation of the coating film in contact with the contacted object such as an optical disk, and an increase in the contact area can be prevented. The contact object is hard to be damaged. Further, the arithmetic average roughness of the coating film, the average length of the contour curve element, and the dynamic friction coefficient are set to predetermined ranges (Ra: 1.3 to 6.2 μm, RSm: 300 to 550 μm, Kf: 0.20 or less). Accordingly, it is possible to reduce the dropout of the beads while maintaining a small contact area with the contacted object, so that the contacted object is hardly damaged.

  In addition, the resin beads have a small particle size (Pd: 10 to 100 μm) and the resin beads content to the base resin is 2 to 12% by weight, thereby reducing the contact area between the coating film and the optical disk. Further, the scratch resistance can be further improved. Further, by reducing the bead content, it is possible to reduce the falling off of the beads from the coating film, so that the contacted object is hardly damaged and the coating operation can be easily performed.

  Moreover, since the content of the lubricant with respect to the base resin is set to 0.2 to 10% by weight with respect to the base resin, sufficient lubricity on the coating film surface is ensured, so that the frictional force with the contacted object is reduced. Therefore, it is difficult for the contacted object to be scratched, the bending workability at the time of molding is improved, and the good winding property at the time of coiling up can be achieved.

  In addition, since a conductive resin film having a predetermined electric resistance (Er: 10Ω or less) is provided on the surface of the metal plate opposite to the coating film, the housing is secured while ensuring scratch resistance and sufficient bending workability. The external surface can be shielded electromagnetically or grounded.

  In still another embodiment, a resin having a predetermined electrical resistance (Er: 10Ω or less) and a predetermined housing surface temperature (32 ° C. or less) on the surface of the metal plate opposite to the coating film. Since the coating is provided, the outer surface of the casing can be electromagnetically shielded or grounded while ensuring scratch resistance and sufficient bending workability, and the amount of heat trapped inside the casing can be reduced.

A. Metal plate The metal used in the present invention is particularly limited as long as it has sufficient strength to form a casing for parts of electric equipment and electronic equipment and has sufficient formability. However, pure aluminum, aluminum alloys such as a 5000 series aluminum alloy, galvanized steel, and stainless steel are preferable.

B. In order to form the pre-coating layer on the convex portion of the surface that becomes the inner surface of the housing after the molding process such as chemical film press molding, a chemical film is first provided on the metal plate before the molding process. Such a chemical conversion film is not particularly limited as long as it is interposed between the surface of the metal plate and the coating film to enhance the adhesion between them. For example, for aluminum alloys, a chemical conversion film formed with a phosphoric acid chromate treatment solution that is inexpensive and easy to manage the bath solution, or a chemical conversion coating formed by a coating-type zirconium treatment that does not require changes in the treatment solution components and does not require washing with water. Can be used. Such a chemical conversion treatment is performed by spraying a predetermined chemical conversion treatment solution on the aluminum alloy plate or immersing the alloy plate in the treatment solution at a predetermined temperature for a predetermined time. For galvanized steel and stainless steel, a chemical conversion film formed with a phosphating solution can be used in addition to the chromate treatment.

  Before the chemical conversion treatment, in order to remove dirt on the surface of the metal plate or to adjust the surface properties, the metal plate is subjected to acid treatment (washing) with sulfuric acid, nitric acid, phosphoric acid or the like, or caustic soda, phosphoric acid. It is desirable to perform alkali treatment (washing) with soda, sodium silicate, or the like. Surface treatment by such cleaning is also performed by spraying a predetermined surface treatment liquid on the metal plate or immersing the metal plate in the treatment liquid at a predetermined temperature for a predetermined time.

C. Coating then coating is formed on the chemical conversion film. The coating film contains a base resin such as a polyester-based resin, resin beads having a specific type and a specific average particle diameter, and further contains a specific lubricant as an essential component, limiting the amount of resin beads added, and an appropriate solvent. In addition, a paint in which these are dissolved or dispersed is baked and coated to a specific coating thickness. On the other hand, a coating film may be formed by powder coating a mixture of a specific resin, resin beads, and lubricant without using a solvent.
The coating film thus obtained employs a combination of a base resin made of a non-flexible resin and beads made of a flexible resin, and has an arithmetic average roughness Ra, contour as surface physical characteristics of the coating film. A characteristic is that the average length RSm and the dynamic friction coefficient Kf of the curved elements are set within a predetermined range. Here, the average length RSm of the contour curve element is an arithmetic average value.
In addition, the said chemical film is provided on both surfaces of a metal plate, and such a coating film is formed on one chemical conversion film.

C-1. Surface physical properties of the coating film Regarding the surface physical characteristics of the coating film, Ra was 1.3 to 6.2 μm, RSm was 300 to 550 μm, and Kf was 0.20 or less. As schematically shown in FIG. 1, the surface roughness R of the coating film is expressed as the height from the coating film surface where no resin beads are present to the portion protruding by the beads. Further, as schematically shown in FIG. 1, the separation distance RS of the contour curve element represents the interval between the protruding portions by the beads. The measured values of Ra and RSm are in accordance with JIS B0601, and include variations in film thickness, but are mainly determined by the film thickness, the amount of beads added, and the particle size of the beads. Therefore, Ra can be considered as an average value of R, and RSm can be considered as an average value of RS. The measured value of Kf is a coefficient of dynamic friction measured with a Bowden testing machine, and is determined by the type of base resin, Ra, RSm, type and content of lubricant, bead content, coating thickness, etc. It is. By setting Ra, RSm and Kf within the above numerical range, good scratch resistance can be obtained.

  If Ra is less than 1.3 μm, the height of the bead protruding portion is not sufficient, so the contact area between the coating film surface of the convex portion on the inner surface of the housing and the optical disk that is the contact object cannot be partially reduced. The optical disk is easily scratched. On the other hand, if Ra exceeds 6.2 μm, the resin beads are easily dropped during the forming process of the precoated metal plate, and the optical disk is easily damaged. In order to further reduce the contact area with the object to be contacted and the impact buffering action of the beads, Ra is preferably 3.6 to 6.2 μm.

  When RSm is less than 300 μm, the distance between the protruding portions of the beads is narrow, so that the contact area between the coating film surface of the convex portion on the inner surface of the housing and the optical disk is partially increased, and the optical disk is easily damaged. On the other hand, when RSm exceeds 550 μm, the surface of the coating film on which no beads are present may come into contact with the optical disk, and the optical disk is easily damaged. In order to further reduce the scratchability of such an optical disc, it is preferable to set RSm to 350 μm to 550 μm.

  If the Kf on the coating film surface exceeds 0.20, the slipperiness of the coating film surface is lowered, so that the optical disk is easily damaged. The range of Kf is preferably 0.15 or less, and more preferably 0.01 to 0.15. This is because if Kf is less than 0.01, the slipperiness is too great, which may cause a problem in winding during coil up.

  In order to impart surface physical properties of Ra, RSm, and Kf to the coating film, the type of base resin, the average particle size and content of beads, the type and content of lubricant, the coating thickness, etc. are adjusted as appropriate. Is done.

C-2. Coating thickness The coating thickness is preferably 5 to 30 μm in a portion where no resin beads are present. This is because if it is less than 5 μm, the resin beads are likely to fall off during the molding process. On the other hand, if the thickness exceeds 30 μm, the surface of the coating film on which no resin beads are present and the optical disk are likely to come into contact with each other.
In addition, it is preferable that the relationship between coating film thickness and the below-mentioned bead average particle diameter Pd is coating film thickness: Pd = 1: 2.0-1: 3.5.

C-3. As the base resin, one or more selected from the group consisting of polyester resins, epoxy resins, and acrylic resins are used. That is, these resins are used alone or in admixture of two or more. Since these resins are inflexible compared to flexible resins such as urethane resins, the deformation of the coating film when the contacted object such as the optical disk comes into contact with the coating film is reduced, and the coating film and the optical disk The contact area with the contacted object can be reduced, and as a result, the scratch resistance can be improved.

  As the polyester resin, alkyd resin, unsaturated polyester resin, modified alkyd resin and the like are used. The alkyd resin has a skeleton of a condensate of a polybasic acid such as phthalic anhydride and a polyhydric alcohol such as glycerin, which is modified with fatty acid fats and oils. Depending on the type and content of the fats and oils used, the oils are classified into short oil alkyd resins, medium oil alkyd resins, long oil alkyd resins and super long oil alkyd resins. An unsaturated polyester resin is synthesized by esterifying an unsaturated polybasic acid or a saturated polybasic acid and a glycol. As the polybasic acid, phthalic anhydride, isophthalic acid, terephthalic acid and adipic acid are used, and as the glycols, propylene glycol is often used. As the modified alkyd resin, those modified with a polymerizable monomer such as natural resin, phenol resin or styrene are used.

Epoxy resins include baking-curing type epoxy resins that are baked using the reaction of hydroxyl groups in the molecule, and curing by addition reaction between primary amines or secondary amines added as curing agents and epoxy groups. The two-component curable epoxy resin is often used. Bake curable epoxy resins include amine resin curable epoxy resins, phenol resin curable epoxy resins, isocyanate curable epoxy resins, and the like. The two-component curable epoxy resin includes an amine curable resin, an amine adduct curable resin, a polyamide resin curable resin, and the like.
In addition to baking curable epoxy resins and two-component curable epoxy resins, epoxy ester resins using ester compounds obtained by reacting an epoxy resin with a dry oil fatty acid, and methyl methacrylate bonded to the end of the epoxy resin. Vinyl esters copolymerized with styrene or the like can also be used.

  As the acrylic resin, an acrylic lacquer using a non-functional monomer, an amino acrylic resin using a functional monomer, or the like is used. A functional monomer having a hydroxyl group is used for the aminoacrylic resin, and curing occurs by a reaction between the hydroxyl group and an alkoxy group or a methylol group in the amino acid resin as a crosslinking agent. On the other hand, the emulsion polymerization type acrylic resin includes a non-dispersion type acrylic resin that is polymerized in a non-aqueous type and a water-based emulsion type acrylic resin. The non-dispersion acrylic resin is a dispersed polymer vehicle obtained by polymerizing a monomer in a solvent that does not dissolve the produced polymer.

  It is preferable to use a polyester-based resin that is less likely to cause coating film cracking during processing such as press processing, has good workability during coating, and is advantageous in terms of cost.

C-4. The convex coating film obtained after resin bead press molding generally stretches and becomes thinner than before molding, and the coating film is difficult to deform. Therefore, deformation hardly occurs even when it comes into contact with the optical disk, and from the viewpoint of preventing an increase in the contact area, it is advantageous to reduce the thickness of the coating film. However, sufficient scratch resistance to the optical disk cannot be obtained only by making the film thin by stretching the coating film on the convex portion. Therefore, by incorporating resin beads into the coating film, the resin beads having high flexibility are elastically deformed when the optical disk comes into contact with each other, so that a buffering effect that reduces the impact caused by the contact is exhibited. Thereby, the damage resistance with respect to an optical disk improves.
Since such resin beads protrude upward from the surface of the coating film, the contact area between an object to be contacted such as an optical disk and the surface of the coating film can be reduced as compared with the case of no addition. As a result, the slipperiness when the optical disk comes into contact with the coating film surface is improved, and the scratch resistance to the optical disk can be improved. However, even if acrylic beads having high hardness are added, the optical disk is scratched and becomes a problem. On the other hand, by including at least one kind of resin beads selected from the group consisting of nylon resin beads and fluorine resin beads rich in lubricity and urethane resin beads rich in flexibility, sufficient resistance can be obtained. Scratchability can be obtained.

  Urethane resin beads include those obtained by polyaddition reaction of diisocyanate and glycol, those obtained by allowing bischloroformate of glycol to act on diamine in the presence of a dehydrochlorinating agent, and diamine and ethylene carbonate. Those obtained by the reaction, those obtained by condensing the ω-aminoalcohol with a chloroformate or carbamic acid ester, and those obtained by the reaction of bisurethane and diamine are used. Many of those obtained by polyaddition reaction of diisocyanate and glycol are used. As diisocyanate, tolylene diisocyanate (a mixture of 2,4- and 2,6-) is often used and has a hydroxyl group. As the compound, ether-based compounds such as polyoxypropylene glycol and polyoxypropylene-polyoxyethylene glycol, and polyester-based compounds obtained by condensing adipic acid and ethylene glycol are often used.

  Examples of nylon resin beads include 6-nylon, 6,6-nylon, 3-nylon, 4-nylon, 7-nylon, 11-nylon, 12-nylon, 6,10-nylon, 6,12-nylon, etc. Beads are used. Of these, 6-nylon, 6,6-nylon, and 6,10-nylon are preferably used.

Fluorine resin beads include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (PEP), and polychlorotrifluoroethylene. (PCTFE), ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polytrifluorochloroethylene Beads such as (PTFCE) and polydichlorodifluoroethylene (DCDFE) are used. Of these resins, polytetrafluoroethylene (PTFE) is most preferably used.
The fluororesin used in the second invention is in the form of beads and has better dispersibility with respect to the base resin than the fluororesin powder added in Patent Document 1. Therefore, the bead-like fluorine-based resin has an advantage that unevenness is less likely to occur in comparison with the powdery fluorine-based resin.

  The average particle diameter Pd of the resin beads used is 10 to 100 μm, preferably 30 to 60 μm. If the average particle size Pd is less than 10 μm, the contact area with the optical disk cannot be reduced, and the optical disk is easily damaged. On the other hand, if the thickness exceeds 100 μm, the resin beads are easily removed from the coating film during the molding process, and the optical disk is easily damaged.

  The content of the resin beads is 2 to 12% by weight with respect to the base resin of the coating film. If it is less than 2% by weight, the contact area with the optical disk cannot be reduced, and the optical disk is easily damaged. On the other hand, if the content exceeds 12% by weight, the beads are easily removed from the coating film during the molding process, and the optical disk is easily damaged. In order to further improve the scratch resistance of the optical disk, the content of urethane resin beads is preferably 2 to 10% by weight, and more preferably 2 to 5% by weight. Similarly, the content of nylon resin beads and fluorine resin beads is preferably 4 to 12% by weight, and more preferably 5 to 8% by weight.

C-5. As the lubricant, at least one selected from the group consisting of carnauba wax, polyethylene wax, and microcrystalline wax is used. Carnauba wax is a plant wax mainly composed of a higher fatty acid ester and has a melting point of 78 to 86 ° C. The polyethylene wax has a molecular weight of 600 to 12000 and a melting point of 105 to 140 ° C., or a wax having an intermediate melting point between paraffin (melting point of about 50 to 75 ° C.) and polyethylene (about 110 to 130 ° C.). Used. The microcrystalline wax is a wax with fine crystallinity obtained from petroleum components, and has a melting point higher than that of paraffin, for example, a molecular weight of 600 to 900 and a melting point of 60 to 93 ° C.

  These lubricants impart lubricity to the coating surface during molding such as press molding, improve the scratch resistance of the coating, and also impart lubricity to the coating surface after molding. , Has the effect of reducing the frictional force generated between the optical disk and the coating surface. Moreover, since these lubricants are cheaper than slipperiness imparting agents such as fluororesin powder, the material cost can be reduced.

  Furthermore, while the fluororesin powder is not liquefied at the baking temperature (generally 200 to 300 ° C. or lower), these lubricants are liquid in that temperature range. Therefore, since the fluororesin powder does not have sufficient permeability to the base resin, a microscopic uniform distribution cannot be obtained over the entire coating film, and as a result, unevenness occurs in slipperiness. On the other hand, since these lubricants have good penetrability, they can be distributed microscopically over the entire coating film, so that slipperiness without unevenness over the entire coating film can be obtained.

  The content of the lubricant is 0.2 to 10% by weight, preferably 0.2 to 3% by weight, based on the base resin. If it is less than 0.2% by weight, Kf exceeds 0.20, the coating film surface cannot be provided with sufficient lubricity, the coating film is easily damaged during press molding, and the optical disk is scratched. It is because it becomes easy to attach. This is because if the content of the lubricant exceeds 10% by weight, it will slip during coil-up when the precoated metal plate is produced, making winding difficult.

C-6. Additives In addition, the paints used in the present invention include pigments, pigment dispersants, fluidity modifiers, leveling agents, anti-waxing agents used in ordinary paints to ensure the paintability and general performance as a precoat material. Agents, preservatives, stabilizers and the like may be added as appropriate.

C-7. Paint coating base resin, resin beads and lubricant are essential components, and the above additives are added to this as appropriate, and a paint in which these are dissolved or dispersed in an appropriate solvent is converted into a chemical coating film by a roll coater (the undercoat layer described below exists). In this case, it is directly applied onto the undercoat layer), treated in an oven at a predetermined temperature for a predetermined time, and baked and dried. Solvents include benzene, toluene, methyl alcohol, ethyl alcohol, ethyl acetate, butyl acetate, cellosolve, butyl cellosolve, 1,4-dioxane, tetrahydrofuran, cyclohexane, isophorone, isobutyl alcohol, xylene, ethylbenzene, methyl ethyl ketone, diacetone alcohol, ethylene Glycol monobutyl ether or the like is used. In addition, it may replace with a roll coater and may apply | coat a coating material with an air spray, a bar coater, etc.

D. Undercoat layer An undercoat layer may be provided between the chemical conversion film and the coating film in order to improve the adhesion between them. Such an undercoat layer is not particularly limited as long as it has excellent adhesion between the chemical conversion film and the coating film and is excellent in moldability. For example, a baked paint containing a resin having good compatibility with the base resin constituting the coating film can be used. As the resin for the undercoat layer, it is preferable to use the same resin as the base resin for the coating film. The undercoat layer has a thickness of 3 to 15 μm, preferably 5 to 10 μm.
Further, the undercoat layer may be composed of a plurality of layers, or another coating film composed of a single layer or a plurality of layers may be provided between the undercoat layer and the coating film.
Such an undercoat layer is directly applied onto the chemical conversion film by a roll coater, an air spray, a bar coater or the like, and is baked and dried after being treated in an oven at a predetermined temperature for a predetermined time.

E. It is good also as a precoat metal plate of the structure which further provided the electroconductive resin film in the outer surface on the opposite side to the said coating film which is a surface which becomes a housing | casing after shaping | molding an electroconductive resin film. In this case, a chemical conversion film is provided on a metal plate that is the outer surface opposite to the coating film, and a conductive resin film is formed thereon. The conductivity of the conductive resin film is such that the electrical resistance value Er is 10Ω or less when a silver probe (using a 5 mm diameter, 2.5 mmR tip) is brought into contact with a load of 100 g by the four-terminal method. It is. This is because if Er exceeds 10Ω, sufficient electrical characteristics such as grounding and magnetic shielding required for the outer surface of the housing cannot be secured. The thickness of such a conductive film is preferably 0.3 to 5 μm.

As such a conductive resin film, as disclosed in Patent Document 3, a coating film formed by applying a paint in which an Ni resin and a wax are mixed with an organic resin, or disclosed in Patent Document 4 is disclosed. A coating containing at least one selected from the group consisting of acrylic resins, epoxy resins, and urethane resins as a resin component, and containing 1 to 50% by weight of moisture and 0.1 to 20% by weight of a lubricant. A membrane can be used.
JP 2001-29885 A JP 2002-275656 A

F. A conductive and heat-dissipating resin film is provided on the outer surface opposite to the coating film, which is the outer surface of the casing after molding the conductive and heat-dissipating resin film. It is good also as a precoat metal plate of composition. In this case, a chemical conversion film is provided on a metal plate on the outer surface opposite to the coating film, and a resin film having both conductivity and heat dissipation is formed thereon.

  Such a resin film is based on at least one selected from the group consisting of a fluororesin, an epoxy resin, a polyester resin, an acrylic resin, and a urethane resin, and at least graphite for imparting heat dissipation. And at least nickel powder in order to impart conductivity. The polyester resin, acrylic resin, and epoxy resin as the base resin are the same as the base resin used for the coating film. Moreover, the same resin as the resin of beads used for the coating film is used as the fluorine resin and the urethane resin as the base resin.

  The conductivity of the conductive and heat-dissipating resin film is such that the electric resistance Er is 10Ω when a silver probe (with a diameter of 5 mm and a tip of 2.5 mmR) is brought into contact with a load of 100 g by the four-terminal method. It is as follows. This is because if Er exceeds 10Ω, sufficient electrical characteristics such as grounding and magnetic shielding required for the outer surface of the housing cannot be secured. The thickness of such a conductive and heat-dissipating resin film is preferably 0.3 to 5 μm.

  Regarding the heat dissipation of the conductive and heat-dissipating resin film, the temperature of the surface of the casing at the time when the temperature inside the casing reaches a steady state is set as a light source inside the casing to emit light and generate heat. It shall be below ℃. If the surface temperature of the housing exceeds 32 ° C., heat may be accumulated in the housing and the original performance of the electronic device may be impaired.

As such a conductive and heat-dissipating resin film, a coating film formed by applying a paint in which graphite and Ni filler are mixed with an organic resin as disclosed in Patent Document 5 can be used.
Japanese Patent Application No. 2004-186287

  The scratch-resistant pre-coated metal plate described in detail above is used as a housing for electrical equipment and electronic equipment such as televisions, video devices, personal computers, etc., but is not limited thereto, structural housing, etc. It can also be used. Further, although it has scratch resistance against optical disks such as CDs and DVDs, it is not limited to optical disks, but is used for scratch resistance to various members having a precise processed surface such as magnetic disks and magneto-optical disks. It may be used as

Hereinafter, the present invention will be described in detail with reference to examples.
Examples 1-24 and Comparative Examples 1-9
Both surfaces of an aluminum alloy plate (material: JIS A5052, plate thickness: 0.6 mm) were degreased with a commercially available aluminum degreasing agent, washed with water, and then subjected to chemical conversion treatment with a commercially available phosphoric acid chromate treatment solution. Next, a coating for a conductive resin film (a coating obtained by mixing an epoxy resin with a nickel filler and microcrystalline wax) was applied to one chemical conversion treated surface A with a bar coater and baked. On the other hand, the other chemical conversion treatment surface B was coated with an undercoat made of a polyester resin with a bar coater and baked to adjust the coating thickness to 10 μm. Next, a paint containing base resin, resin beads and lubricant shown in Table 3 was applied onto the undercoat layer with a bar coater and baked. The baking temperature was a maximum attainable plate temperature (PMT) of 200 to 240 ° C.
Table 1 shows the conditions of Examples 1 to 24 and Comparative Examples 1 to 9.

Examples 25 and 26
As the base material, a stainless steel plate was used in Example 25, and a galvanized steel plate was used in Example 26. These metal plates were subjected to chemical conversion treatment with a phosphating solution. Next, a heat-dissipating and conductive resin film paint containing polyester resin, graphite and nickel filler is applied to one chemical conversion treated surface A with a bar coater so that the film thickness after drying is 1 μm. I baked it. On the other hand, on the other chemical conversion treated surface B, an undercoat made of polyester resin was applied and baked with a bar coater to adjust the coating thickness to 10 μm, and then the base resin, resin beads and lubricant shown in Table 1 were used. The paint containing was applied onto the undercoat layer with a bar coater and baked. The baking temperature is the maximum plate temperature (PMT) 200-240 ° C. Table 1 shows the conditions of Examples 25 and 26.

  As described above, precoated metal sheets for parts of electric and electronic devices schematically shown in FIG. 1 were produced. In FIG. 1, 1 is a conductive resin film or a heat-dissipating and conductive resin film, 2 is a chemical conversion film, 3 is a metal plate such as an aluminum alloy plate, 4 is an undercoat layer, 5 is a coating film, 6 Indicates resin beads, respectively.

The amount of chromium of the chemical conversion film measured by a fluorescent X-ray analyzer was 30 mg / m ² . A silver probe (diameter 5 mm, tip 2.5 mmR) was brought into contact with the surface A with a contact load of 100 g by the four-terminal method, and the electrical resistance value was measured.

  About Example 25 and Example 26, the housing | casing was produced with the following method and the housing | casing surface temperature was measured. In other words, a case with a surface of 150 mm × 150 mm and a height of 100 mm was prepared with the A side of the obtained pre-coated metal plate on the outside and the B surface on the inside, and a 60 W light bulb was placed inside as a light source. The temperature on the surface of the housing was measured when the temperature inside the housing reached a steady state. As a result, the steady state temperature was 32 ° C.

  Next, the obtained pre-coated metal sheet was subjected to a scratch resistance test, a surface roughness measurement test, a lubricity test, and a bending workability test by the following test methods to evaluate the performance.

<Scratch resistance test>
A scratch resistance test using an optical disk was performed using a Bowden friction tester. FIG. 2 schematically shows the positional relationship between the test piece and the optical disk in the scratch resistance test. In FIG. 2, 7 is a test piece, 8 is an optical disk, and 9 is a frame. The test piece 7 was produced by projecting the B side of the precoated aluminum alloy plate by 4 mm with an Erichsen tester. The test piece was loaded with a load of 100 g and brought into contact with the optical disc and slid 20 times at a speed of 40 mm / min. Three test pieces were measured for each coating condition.

  Scratch resistance is measured by observing the optical disc after the test with an optical microscope with a magnification of 50 times, measuring the width of the scratch, and the total width of the three measurements is less than 0.2 mm. Evaluation was made based on the criteria of .smallcircle., Less than 4 mm, .largecircle., Less than 0.4 mm and less than 0.6 mm, .largecircle., From 0.6 mm to less than 1.0 mm, and .times. ◎, ○ and ○ △ were accepted.

<Surface roughness measurement test>
The surface roughness of the paint film is measured based on JIS B0601, and the surface roughness R and the distance RS of the contour curve element are measured, and Ra is calculated as an arithmetic average value of R, and RSm is evaluated as an arithmetic average value of RS. did.

<Lubricity test>
The lubricity of the coating film was evaluated by measuring the dynamic friction coefficient Kf when a 3/16 inch steel ball was moved once in a forward direction with a load of 500 g using a Bowden testing machine. It shows that lubricity is so high that Kf is small.

<Bending workability test>
Based on JIS Z2248, the bending workability was bent 180 degrees by sandwiching two base plates with the B surface of the aluminum alloy plate facing outside (total thickness 1.6 mm), and the appearance of the bent portion was visually observed. The case where a coating film crack was not observed was set as the pass.

  The test results of Examples 1 to 26 and Comparative Examples 1 to 9 are shown in Table 2.

  In Examples 1 to 26, a base resin selected from a polyester resin, an epoxy resin, and an acrylic resin, a resin bead selected from nylon resin beads, fluororesin beads, and urethane resin beads, and carnauba wax A composition selected from the group consisting of polyethylene wax and microcrystalline wax, an arithmetic average roughness Ra of 1.3 to 6.2 μm, an average length of contour curve elements RSm of 300 to 550 μm, and The result using the coating film in which the dynamic friction coefficient Kf is in the range of 0.20 or less is shown. With these precoated metal plates, good scratch resistance of the optical disk was obtained. In all Examples and Comparative Examples, there was no coating film cracking and bending workability was good.

In Comparative Example 1, since neither urethane resin beads, nylon resin beads, or fluorine resin beads were contained in the coating film, the optical disk scratch resistance was poor.
In Comparative Examples 2 and 3, since resin beads different from urethane resin beads, nylon resin beads, and fluorine resin beads were added, the optical disk scratch resistance was inferior.
In Comparative Example 4, since the lubricant was not contained in the coating film, the optical disk scratch resistance was poor.
In Comparative Example 5, since the RSm exceeded 550 μm, the optical disc scratch resistance was poor.
In Comparative Example 6, Ra was over 6.2 μm, so the optical disk scratch resistance was poor.
In Comparative Example 7, Ra was less than 1.3 μm and RSm was less than 300 μm, so that the optical disk scratch resistance was poor.
In Comparative Examples 8 and 9, since a flexible urethane-based resin was used as the base resin and polytetrafluoroethylene was used as the lubricant, the optical disk scratch resistance was poor.

  A pre-coated metal sheet for electrical and electronic equipment casings, which has excellent scratch-proofing properties for optical disks, good winding properties when coiling up, low manufacturing costs, and uniform slipperiness. Provide a metal plate.

FIG. 1 shows a cross-sectional view of a scratch-resistant pre-coated aluminum alloy plate for parts of electrical equipment and electronic equipment according to the present invention. It is explanatory drawing which shows the positional relationship of the test piece and optical disk in an optical disk damage | wound test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive resin film or conductive and heat radiating resin film 2 Chemical conversion film 3 Metal plate 4 Undercoat layer 5 Coating film 6 Resin bead 7 Test piece 8 Optical disk 9 Mount R Surface roughness RS Contour curve element separation distance

Claims (5)

A chemical conversion film formed on both sides of the metal plate;
At least one base resin selected from the group consisting of a polyester resin, an epoxy resin and an acrylic resin; a nylon resin bead and a fluorine resin; A coating comprising: at least one resin bead selected from the group consisting of beads and urethane-based resin beads; and at least one lubricant selected from the group consisting of carnauba wax, polyethylene wax and microcrystalline wax. With a membrane,
The arithmetic average roughness Ra of the coating film is 1.3 to 6.2 μm, the average length RSm of the contour curve element is 300 to 550 μm, and the dynamic friction coefficient Kf on the coating film surface is 0.20 or less. A scratch-resistant pre-coated metal sheet characterized by that.   The scratch-resistant precoated metal according to claim 1, wherein the resin beads have an average particle diameter Pd of 10 to 100 µm, and the resin beads are contained in an amount of 2 to 12 wt% with respect to the base resin of the coating film. Board.   The at least one lubricant selected from the group consisting of the carnauba wax, polyethylene wax, and microcrystalline wax is contained in an amount of 0.2 to 10% by weight based on the base resin of the coating film. 2. A scratch-resistant precoated metal alloy sheet according to 2.   A conductive resin film formed on the other of the chemical conversion film, further comprising a conductive resin film having an electric resistance value Er of 10Ω or less when a silver probe is contacted with a contact load of 100 g by a four-terminal method. The scratch-resistant precoated metal sheet according to any one of claims 1 to 3.   A resin film formed on the other of the chemical conversion films, and at least one base resin selected from the group consisting of a fluorine resin, an epoxy resin, a polyester resin, an acrylic resin, and a urethane resin; The scratch-resistant precoated metal according to any one of claims 1 to 3, further comprising a heat-dissipating and conductive resin film containing: a heat-dissipating material containing at least graphite; and a conductive material containing at least nickel powder. Board.

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