JP2005139535A - Coated metal sheet having excellent heat radiability and colorability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated metal sheet whose heat radiating property and coloring property are made compatible. <P>SOLUTION: In the coated metal sheet whose heat radiating property and coloring property are made compatible, at least one side of a metal sheet is provided with an organic coating layer containing boron nitride with a mean particle diameter of 0.01 to 30 μm by 3 to 70 mass% at a thickness of ≥1 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coated metal plate excellent in heat dissipation, and is suitable for applications in which heat generation from internal parts such as a personal computer casing is a problem.

  In recent years, heat from internal components has become a problem as home appliances progress. Heat generation is a particular problem in the field of personal computers. In a personal computer, the heat generation temperature from the CPU increases as performance increases, and an air cooling fan is usually installed as a countermeasure. However, since a space for mounting the air cooling fan is required, it is difficult to further reduce the size of the personal computer. If possible, a housing having a cooling effect without the air cooling fan is desired.

  As a metal plate excellent in heat dissipation, for example, Patent Document 1 discloses a technique disclosed as a heat dissipation sheet and a heat dissipation plate. This improves heat dissipation by adding an inorganic filler to the silicone resin. Certainly, although this technology improves heat dissipation, there is a problem that the heat dissipation sheet is colored in the color of the inorganic filler because it is necessary to add a large amount of inorganic filler.

  In recent years, steel plates with excellent heat dissipation have been used in AV equipment, which is a large amount of carbon black with excellent absorption and emission of infrared rays. Certainly, carbon black is a substance excellent in absorption and emission of infrared rays, which are heat rays, and its heat dissipation is improved by its addition.

  However, even if only a few mass% of carbon black is added, the coating film becomes black, so if you add an amount that exhibits sufficient heat dissipation characteristics, you can use any commonly used color pigment or dye There is a problem that it cannot be colored in any color. In particular, since it is indispensable to add a design by color in the field of home appliances, the inability to color other than black has been a major drawback.

  In other words, any of the metal plates that are currently excellent in heat dissipation cannot be prevented from being strongly colored by the heat dissipation additive, and has a problem that it is difficult to color in any color. Under such circumstances, there has been a demand for a coated metal plate that can be colored in any color while having heat dissipation.

JP-A-10-237228

  The present invention solves the above-described problems, and provides a coated metal plate that is excellent in heat dissipation and less colored by a heat dissipation additive and can be colored arbitrarily.

  The present inventors examined in detail the heat dissipation of the coating film of the coated metal plate constituting the housing from the viewpoint of the type and color of the heat dissipation additive. As a result, it has been found that diamond and boron nitride are optimal as white or transparent materials that do not adversely affect the color of the coating film and that absorb or emit infrared rays satisfactorily. However, since diamond is expensive, it was not suitable for general-purpose products such as painted metal plates, and boron nitride was found to be optimal.

  That is, the boron nitride powder is white, and the coating film containing the boron nitride powder can be arbitrarily colored with a normal colorant, and can be applied to a coated metal plate as an additive excellent in heat dissipation. It came.

The gist of the present invention is as follows.
(1) Paint metal with excellent heat dissipation and colorability having an organic coating layer containing 3 to 70% by mass of boron nitride having an average particle size of 0.01 to 30 μm on at least one side of a metal plate with a thickness of 1 μm or more Board.
(2) The coated metal plate excellent in heat dissipation and colorability according to (1), wherein the boron nitride is boron nitride (h-BN) having a hexagonal graphite-like structure.
(3) The coated metal plate excellent in heat dissipation and colorability according to (1), wherein the metal plate is a plated steel plate.

  The coated metal plate of the present invention has excellent heat dissipation, and since the heat dissipation additive is white boron nitride unlike carbon black, it can be colored in any color (especially other than black). Since it is possible, it is suitable for applications such as housings of household electrical appliances that require countermeasures against heat and imparting design.

  The coated metal sheet of the present invention is coated with an organic coating layer containing 3 to 70% by mass of boron nitride having an average particle size of 0.01 to 30 μm on at least one side with a thickness of 1 μm or more. Although heat dissipation can be imparted even if the average particle size is less than 0.01 μm, classification to 0.01 μm or less leads to an increase in cost, which is not preferable in terms of economy. On the other hand, if it exceeds 30 μm, boron nitride may fall off during severe processing, which is not preferable. If the boron nitride content in the coating film is less than 3% by mass, the effect of heat dissipation is insufficient, which is not preferable. On the other hand, if it exceeds 70% by mass, the coating film may be peeled off during severe processing, which is not preferable. A more preferable content is 20 to 50% by mass. The thickness of the coating of the present invention is 1 μm or more. If it is less than 1 μm, sufficient heat dissipation cannot be obtained. The upper limit is not particularly limited, but considering the cost, the preferable upper limit of the film thickness is 50 μm when applied as a paint, and 3 mm when applied as a film laminate.

  The type of boron nitride is not particularly limited, and cubic (zinc flash structure) boron nitride (c-BN), hexagonal wurtz steel structure boron nitride (w-BN), hexagonal graphite-like structure nitriding Boron (h-BN) can be applied. These can be used alone or in a mixed state of two or more.

  A particularly preferred boron nitride is boron nitride having a hexagonal graphite-like structure. Since hexagonal graphite-like structure boron nitride has a layered structure similar to graphite, good lubricity can be imparted by sliding between layers. That is, when boron nitride having a structure similar to hexagonal graphite is used as an additive, not only heat dissipation characteristics and coloring properties but also lubrication characteristics can be obtained at the same time, which is optimal as a coated metal plate.

  The amount of hexagonal graphite-like structure boron nitride added is 3% by mass or more. If it is less than 3% by mass, sufficient lubricity cannot be obtained.

  The paint resin used for the coated metal plate of the present invention is not particularly limited, and those usually used as paint resins can be applied. For example, high-molecular polyester resin, polyester resin, acrylic resin, epoxy resin, urethane resin, fluorine resin, or resin components such as these modified resins can be used as butylated melamine, methylated melamine, butylmethyl mixed melamine. , Urea resins, isocyanates and those cross-linked by a cross-linking component of these mixed systems, and those such as an electron beam curable type and an ultraviolet curable type. Further, a thermosetting type or a thermoplastic type may be used.

  It is also possible to produce a film containing boron nitride of the present invention and laminate the metal plate in the film state. Examples of resins suitable for laminating include fluorine resins, acrylic resins, polyvinyl chloride resins, polyethylene terephthalate resins, and the like, and commonly used adhesives and corona discharge treatments may be used in combination.

  In the case of the conventional heat-dissipating metal plate, since a black additive such as carbon black was used as a heat-dissipating additive, it was difficult to color, but in the present invention, white boron nitride is used. It can be easily colored with various coloring pigments and dyes.

  The color pigment and dye are not particularly limited. As the pigment, a known pigment can be used regardless of inorganic type, organic type, or a combination of both, cyanine pigments such as titanium white, zinc yellow, alumina white, and cyanine blue, pyrazolone orange, and azo pigments. , Bitumen, condensed polycyclic pigments, and the like. Other examples include glittering pigments such as metal pieces / powder, pearl pigments and mica pigments, indigoid dyes, sulfur dyes, phthalocyanine dyes, diphenylmethane dyes, nitro dyes, acridine dyes and the like. The pigment concentration is not particularly limited and may be determined according to the necessary color and hiding power.

  Further, in addition to the color pigments and dyes, any pigments that are usually added to paints can be added without any problem. For example, extender pigments such as calcium carbonate, talc, gypsum, and clay, and other organic crosslinked fine particles and / or inorganic fine particles. If necessary, a surface smoothing agent, an ultraviolet absorber, a hindered amine light stabilizer, a viscosity modifier, a curing catalyst, a pigment dispersant, a pigment settling inhibitor, a color separation inhibitor, and the like can be used.

  The coating of the present invention may contain a heat-dissipating additive such as carbon black at the same time as the design allows.

  For the purpose of improving the corrosion resistance of the coated metal plate of the present invention, a rust preventive pigment may be added to the coating film of the present invention. As the rust preventive pigment, known ones can be applied, for example, phosphate phosphate rust preventive pigments such as zinc phosphate, iron phosphate, aluminum phosphate, zinc phosphite, calcium molybdate, aluminum molybdate, molybdic acid. Molybdate anticorrosive pigments such as barium, vanadium anticorrosive pigments such as vanadium oxide, silicate pigments such as calcium silicate, strontium chromate, zinc chromate, calcium chromate, potassium chromate, and chromate anticorrosive pigments such as barium chromate Further, fine silica such as water-dispersed silica and fumed silica, ferroalloy such as ferrosilicon, and the like can be used. These may be used alone or in combination.

  Nickel filler or the like may be added to the coated metal plate of the present invention to impart conductivity.

  The coated metal plate of the present invention can be painted by any method. Examples thereof include a bar coater, spray coating, brush coating, roll coater, overflow curtain coater, slit curtain coater, roller curtain coater, T-die, and multilayer curtain coater.

  The method for drying (curing) the coated metal plate of the present invention is arbitrary, and is a method suitable for the coating material to be used, such as heat drying such as hot air heating, high-frequency induction heating, natural drying, curing by electron beam, ultraviolet irradiation, etc. Should be selected.

  Although the base metal plate of this invention is not specifically limited, A stainless steel plate, a plated steel plate, and an aluminum alloy plate are suitable. Examples of the stainless steel plate include a ferritic stainless steel plate, a martensitic stainless steel plate, and an austenitic stainless steel plate. Aluminum alloy sheets include JIS1000 series (pure Al series), JIS2000 series (Al-Cu series), JIS3000 series (Al-Mn series), JIS4000 series (Al-Si series), JIS5000 series (Al -Mg), JIS 6000 series (Al-Mg-Si series), JIS 7000 series (Al-Zn series), and the like.

  A particularly suitable metal plate is a plated steel plate having a good balance between cost and performance. As galvanized steel sheet, galvanized steel sheet, zinc-iron alloy plated steel sheet, zinc-nickel alloy plated steel sheet, zinc-chromium alloy plated steel sheet, zinc-aluminum alloy plated steel sheet, aluminum-plated steel sheet, zinc-aluminum-magnesium alloy plated steel sheet, Zinc-aluminum-magnesium-silicon alloy plated steel sheet, aluminum-silicon alloy plated steel sheet, galvanized stainless steel sheet, aluminized stainless steel sheet and the like.

  Examples of the pre-coating treatment for the metal plate include washing with water, washing with hot water, pickling, alkali degreasing, grinding, polishing, and the like, and these may be performed alone or in combination as necessary. What is necessary is just to select suitably the conditions of the coating pretreatment.

  Chemical conversion treatment may be performed on the metal plate as necessary. The chemical conversion treatment is performed for the purpose of enhancing the adhesion between the coating and the base metal plate and for improving the corrosion resistance. As the chemical conversion treatment, known techniques can be used, such as zinc phosphate treatment, chromate treatment, silane coupling treatment, composite oxide film treatment, non-chromate treatment, tannic acid treatment, titania treatment, zirconia treatment, and the like. And the like.

  The coated metal plate of the present invention is coated on at least one side. When two or more layers are coated on one surface, the lower layer, the upper layer, or the intermediate layer may be used, and a plurality of layers may be coated with the boron nitride of the present invention. However, when a lubricating performance is expected using hexagonal graphite-like structure boron nitride, a coating film containing hexagonal graphite-like structure boron nitride must be placed on the top layer.

  You may give the undercoat which contains a rust preventive pigment between the coating film of this invention, and a metal plate. As the undercoat paint, those used for normal undercoat can be used as they are. As the resin, generally known resins can be applied depending on the application. That is, high molecular polyester resin, polyester resin, acrylic resin, epoxy resin, urethane resin, fluorine resin, silicon polyester resin, vinyl chloride resin, polyolefin resin, butyral resin, polycarbonate resin, A resin component such as a phenolic resin or a modified resin thereof can be applied by crosslinking with a butylated melamine, a methylated melamine, a butylmethyl mixed melamine, a urea resin, an isocyanate or a mixed crosslinking agent component thereof.

  As the rust preventive pigment for the undercoat layer, known rust preventive pigments can be applied. For example, phosphate phosphate rust preventive pigments such as zinc phosphate, iron phosphate, aluminum phosphate, zinc phosphite, calcium molybdate, molybdenum Molybdate anticorrosive pigments such as aluminum oxide and barium molybdate, vanadium antirust pigments such as vanadium oxide, silicate pigments such as calcium silicate, strontium chromate, zinc chromate, calcium chromate, potassium chromate, chromate such as barium chromate Antirust pigments, fine silica such as water-dispersed silica and fumed silica, ferroalloys such as ferrosilicon, and the like can be used. These may be used alone or in combination. Boron nitride used in the present invention may be contained in the undercoat layer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these at all.

As the metal plate, an electrogalvanized steel sheet having a thickness of 0.6 mm (plating adhesion amount 20 g / m ² ) was used. The electrogalvanized steel sheet was subjected to an alkaline degreasing treatment and a chromate treatment, and then various coating compositions were applied, followed by heat curing in a hot air heating furnace at a baking temperature (PMT) of 230 ° C.

  As the paint composition, the basic paint composition is obtained by removing a component other than the polymer polyester resin and the melamine curing agent from the polymer polyester resin paint (NSC100HQ, manufactured by Nippon Fine Coatings Co., Ltd.). Various coating compositions for comparison with various coating compositions of the present invention were prepared by adding boron nitride to the product (see Table 1 for details of the coating composition).

  In addition, a coating containing a rust-preventive pigment (P655, Nippon Fine Coatings Co., Ltd.) as a base coating was applied to a dry film thickness of 5 μm.

  As a study on the coloring property, a coated metal plate colored blue was prepared by adding 10% by mass of phthalocyanine blue. As a comparison, a paint containing carbon black instead of boron nitride was also prepared, and an attempt was made to add phthalocyani blue to the paint to add 10% by mass (see Table 2 for details of the coating composition). ).

Below, the evaluation method of the produced coated metal plate is demonstrated.
1. Evaluation method of heat dissipation Evaluation of heat dissipation was performed by making a box-shaped simulated housing (150 x 285 x 110 mm) as shown in Fig. 1. In other words, a painted metal plate for evaluation is installed on the upper lid of the simulated enclosure, a heater is installed inside the enclosure, and the temperature one hour after the start of heating is measured with a thermocouple (from the temperature measurement point). The distance to the coated metal plate was 15mm), and the one with a temperature lower by 5 ° C or more than the comparative electrogalvanized steel plate was accepted. In addition, the output of the heater (input heat amount 10 W constant) was adjusted so that the temperature in the simulated casing reached 80 ° C. within 1 hour after the start of heating under the condition that the top cover was made of an electrogalvanized steel sheet.
2. Processability evaluation method For the processability test, after transferring the embossed pattern of the stone tone by roll forming, visually evaluate the peeling state of the coating film of the molding process part and pass 3 or more according to the following evaluation criteria. It was. A sample coated only on one side was subjected to a workability test by pressing a 1 mm thick Teflon sheet on the opposite side.

Evaluation criteria for roll forming
5: No peeling
4: Very slight peeling
3: Slight peeling
2: With peeling
1: Extensive peeling

  From Table 1, it can be seen that the coated metal plate containing boron nitride within the scope of the present invention has good heat dissipation. It can also be seen that when hexagonal graphite-like structure boron nitride is used as boron nitride, the moldability is also improved. Furthermore, it can be seen that the coated metal plate having the coating of the present invention has good heat dissipation even under the condition of the undercoating.

  As shown in Table 2, a coated metal plate using carbon black as a heat dissipation additive instead of boron nitride can give sufficient heat dissipation, but the color of the coating can be improved by adding phthalocyanine blue. Was black and could not be colored blue, and was inferior in design. On the other hand, boron nitride has sufficient heat dissipation properties, and at the same time can be easily colored blue with phthalocyanine blue, and has excellent design.

The figure which shows the heat dissipation measuring method of a coating metal plate.

Claims (3)

  A coated metal plate excellent in heat dissipation and colorability having an organic coating layer containing 3 to 70% by mass of boron nitride having an average particle size of 0.01 to 30 μm on at least one side of the metal plate with a thickness of 1 μm or more.   2. The coated metal plate excellent in heat dissipation and colorability according to claim 1, wherein the boron nitride is boron nitride (h-BN) having a hexagonal graphite-like structure. 2. The coated metal plate having excellent heat dissipation and colorability according to claim 1, wherein the metal plate is a plated steel plate.

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