JP4527587B2 - Painted metal material with excellent heat dissipation and electronic equipment parts using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a coated metal material having excellent heat dissipation, and in particular, heat dissipation useful as a material of a casing (casing) that houses an electronic device (including an electric device and an optical device that includes a heat source). The present invention relates to a coated metal material having excellent properties and an electronic device component using the painted metal material as a protective casing.

  In recent years, as the performance and miniaturization of electronic equipment has progressed, the rise in the internal temperature of the equipment due to heat generated from the inside of the electronic equipment has become a problem, such as IC, CPU (semiconductor element), disk, motor, etc. There is a concern that the stable operation may be hindered beyond the heat-resistant temperature. Further, when the internal temperature of the electronic device rises, the semiconductor element may be broken or broken, and the life of the electronic device component may be shortened.

  The present inventors pay attention to such a situation, and started to develop a housing material that can quickly dissipate heat generated from electronic device parts with a built-in heat source to the outside to suppress the rise in internal temperature. The technology described in Document 1 was developed.

The present invention is a coated body having improved heat dissipation by forming a heat-dissipating coating film containing a heat-dissipating additive on the surface or front and back surfaces of a base material. A conductive filler such as Ni is blended together with a conductive additive to provide conductivity. This coated body has an infrared ray (wavelength: 4.5 to 15.4 μm) integral emissivity when heated to 100 ° C. that satisfies the relationship of the following formula (1), and has heat dissipation and conductivity for electromagnetic wave shielding. It is attracting attention as a coated body for electronic devices (excluding microwave oven parts) that excel in the area.
a × b ≧ 0.42 (1)
a: Infrared integrated emissivity of a coated body having a heat-radiating coating film formed on the surface b: Infrared integrated emissivity of a coated body having a heat-radiating coating film formed on the back surface

  This coated body exhibits excellent heat radiation characteristics by forming a heat-dissipating coating film containing a heat-dissipating additive on one or both sides of the base material. A wide range of applications is expected as a housing for electronic equipment. However, in order to further develop this technology in the future, further improvement in heat dissipation characteristics is required.

  Patent Document 2 discloses a sealed battery with a convection promoting film in which a convection promoting film that promotes air convection is mounted on the outermost surface of the battery. As the convection promoting film, a thin-film polyethylene terephthalate film or polytetrafluoroethylene film is disclosed. Examples thereof include a fluoroethylene film and a polypropylene film.

  However, even if the thin film material described in Patent Document 2 is used as the coating material intended by the present invention, the heat radiation characteristics as expected in the present invention are not exhibited.

  Furthermore, Patent Document 3 includes a sealed housing housing electronic device parts, a ventilation path provided in the housing, having an intake hole in the lower portion and an exhaust hole in the upper portion, and cools the housing by natural air cooling. An air-cooled sealed electronic device housing having a structure is disclosed.

However, this technique is intended to control the flow of external air by devising the peripheral structure of the heating element to promote heat dissipation, and is essentially different from the technique of improving the heat dissipation characteristics of the coating film itself.
Japanese Patent No. 3563731 JP 2001-313209 A JP 2001-291982 A

  The present invention has been made under the circumstances as described above, and its purpose is to further improve the performance of the heat dissipating coated body as disclosed in Patent Document 1 and further improve the heat dissipating characteristics of the coating film. In addition to providing a painted metal material, it is an object of the present invention to provide useful electronic device parts using the painted metal material.

  The coated metal material of the present invention that has solved the above problems is a coated metal material in which at least one layer of a coating film is formed on one side or both sides of a metal substrate, and the outermost layer has an opening on the surface. The porous particles having pores of 1 to 1000 nm are contained in a state in which at least a part is exposed from the surface of the outermost layer.

  The outermost layer in the coated metal material of the present invention has a thickness (x) of 0.5 to 4 μm, an average particle size (y) of porous particles of 1 to 8 μm, and a relationship of “x <y” Is preferably satisfied. In addition, a coating layer containing a radioactive additive is formed on the lower surface side of the outermost layer, and infrared radiation (wavelength: 4.5 to 15.4 μm) integrated radiation when the coated metal body is heated to 100 ° C. Those having a rate of 0.6 or more are preferable because they have more excellent heat dissipation characteristics, and those having a surface resistance reduced to 100 Ω or less by blending the coating film with a conductive filler such as Ni have an electromagnetic shielding effect. Is also preferable. And the coated metal body of this invention provided with such a characteristic can be utilized very effectively especially for the housing | casing of the electronic device which has a heat source.

  Further, the electronic device component of the present invention is an electronic device component having a built-in heat source, wherein at least a part of the outer wall of the electronic device component is composed of the above-mentioned painted metal body and has excellent heat dissipation characteristics. It has the characteristic in that.

  As described above, the coated metal material of the present invention has porous particles having pores of 1 to 1000 nm opened on the surface in the outermost layer of the coating film, and at least a part of the porous particles from the surface of the outermost layer. Exposed and contained in open pores, effectively utilizing the heat transfer promoting action to the outside air by the convection provided by the porous particles to exhibit excellent heat dissipation characteristics. It can be used very effectively as a material for the housing that protects various electronic devices that cause eruption.

  In particular, the above-mentioned porous particles are blended in the outermost layer of the coating film, and the coating film in which the heat-dissipating additive is blended in the lower layer side is used to promote heat transfer by the convection of the outermost layer and Combined with radiation characteristics, it exhibits extremely excellent heat dissipation characteristics. Furthermore, a conductive filler is blended in at least one of the above coatings to reduce the electrical resistance of the coating to 100Ω or less. Is good and has excellent performance in the electromagnetic shielding effect.

  Heat generated from an internal heat generating component such as an electronic device is transmitted to a casing (casing) that protects the device by heat conduction, convection, heat radiation, or the like. Therefore, if this heat can be quickly dissipated to the atmosphere without accumulating in the housing, the internal temperature of the housing can be kept safe without excessively increasing the internal temperature of the housing.

  Therefore, in the above-mentioned Patent Document 1, by constituting the casing with a plate material in which the constituent material of the casing is covered with a heat-dissipating coating film, heat generated inside the apparatus is dissipated to the outside air, and an increase in the internal temperature of the electronic apparatus is suppressed. Yes. Such a heat-dissipating coating film is one that has improved heat dissipation by blending a heat-dissipating additive such as carbon black as described above, and by adding a conductive filler to the coating film to give conductivity, It is clarified that an electromagnetic wave shielding effect can be imparted.

  On the other hand, in the present invention, the use of such a heat-dissipating additive is not excluded, but the main component of the heat-dissipating action is contained in the outermost layer of the coating film, and has a pore having 1-1000 nm pores opened on the surface. It is characterized by the fact that it is exhibited by the particles. That is, if porous particles having pores of a predetermined size opened on the surface are contained in a state where a part thereof is exposed from the surface of the outermost layer of the coating film, the exposed pores of the porous particles are against the outside air. It was confirmed that the heat transfer effect by convection was demonstrated and the heat dissipation characteristics were further improved.

  As described above, the reason why the pores of a predetermined size opened on the surface of the porous particles exhibit a specific heat dissipation characteristic has not been clarified at present. However, as will be clarified in the examples to be described later, in the case where the average diameter of the open pores is smaller than 1 nm, the heat dissipation characteristics are hardly improved, and the pores are closed pores which are not opened on the surface. However, considering that the heat dissipation characteristics intended by the present invention are not exhibited, it is clear that the apertured pores having an average diameter of 1 nm or more have a considerable influence on the heat dissipation characteristics.

  Moreover, it is important that at least a part of the porous particles are exposed from the surface of the outermost layer of the coating film, and the open pores are present in an open state on the outer surface. The simplest method is to adjust the film thickness (x) of the coating film constituting the outermost layer and the average particle diameter (y) of the porous particles so as to satisfy the relationship of “x <y”. That is, the fact that the average particle diameter (y) and the film thickness (x) of the porous particles satisfy the above relationship means that at least a part of the porous particles is exposed from the surface of the outermost layer coating film. Yes. For this reason, the open pores present on the surface of the exposed porous particles promote heat transfer in the direction of the external atmosphere by convection, and the heat dissipation characteristics are more effectively enhanced.

  However, if the average particle diameter (y) of the porous particles is too large with respect to the film thickness (x), the porous particles greatly protrude from the surface of the outermost layer, and the protruded porous particles are exposed to the outermost layer with a small frictional force. The average particle diameter (y) of the porous particles is preferably about 3/2 to 2 times the film thickness (x), that is, “(3/2) · x ≦ y ≦ 2x”. It is desirable to adjust the film thickness and the average particle diameter of the porous particles so that about 1/3 to 1/2 of the porous particles are exposed from the upper surface of the outermost layer. However, when the particle size distribution of the porous particles is narrow, a higher proportion of particles can be exposed on the surface of the outermost layer.

  Note that the size of the pores opened on the surface of the porous particles is extremely important in increasing the heat transfer efficiency by convection in the direction of the outside air. Has been confirmed to be at least 1 nm or more. The reason for this is not clarified at present, but it has been confirmed that a fine hole of less than 1 nm does not exhibit the effect of promoting heat dissipation intended in the present invention. The average diameter of the more preferable pore confirmed by experiment is 5 nm or more, More preferably, it is 10 nm or more.

  There is no particular upper limit of the average pore diameter, but in the present invention, granular porous particles having the pores are mixed in the outermost layer coating film to exert its function, and the outermost layer thickness ( x) is preferably about 0.5 to 4 μm as described later, and the average particle diameter (y) of the porous particles is preferably in the range of 1 to 8 μm in relation to the film thickness (x). If the pores are too large, the porous particles become brittle and easily collapse, so the upper limit of the pore diameter to avoid such problems is considered to be about 1000 nm. The upper limit of the more preferable pore diameter is 500 nm, and more preferably about 200 nm.

  The pore diameter of the porous particles is measured by a nitrogen gas adsorption method using a trade name “AUTOSORBI” manufactured by UAE Sonics, and the average particle diameter of the porous particles is a trade name manufactured by Leed & Northrup. This is a value measured using “Microtrack 9220FRA”.

  The preferable thickness of the outermost layer is set in the range of 0.5 to 4 μm because if the film thickness is too thin, the outermost layer cannot hold a necessary amount of porous particles. This is because if the film thickness exceeds 4 μm, the vehicle resin layer constituting the outermost layer may hinder heat dissipation. A more preferable film thickness of the outermost layer is 1 μm or more and 3 μm or less in consideration of the retention property and heat dissipation of the porous particles.

  In the present invention, as described above, the heat radiation characteristics are enhanced by utilizing the convective heat transfer promoting action by the open pores of the porous particles exposed from the surface of the outermost layer of the coating film. The exposed pores on the surface of the porous particles must be kept in an open state. For this purpose, the vehicle resin component is a volatile solvent as a coating solution for forming the porous particle-containing layer. It is preferable to use a coating solution with a low solid content that is sufficiently diluted with the above.

  That is, when a coating solution with a high solid content is used, when the coating solution is applied to the outermost coating layer and dried to form the outermost coating layer, the resin that penetrates into the pores of the porous particles is dried and solidified as it is. However, if a coating solution with a low solid content is used, the amount of resin remaining after drying and solidification is small, so the pores are blocked to the extent that a resin film is formed on the inner wall surface of the pores. This is because there is no fear of getting out.

  Therefore, when forming the outermost layer coating film, the concentration of the resin solid content excluding the porous particles is 10% by mass or less, more preferably 7.5% by mass or less, and further preferably about 5% by mass or less. It is recommended to use the coating solution. Use of such a low-concentration coating solution is advantageous in forming the outermost layer having a thickness of 0.5 to 4 μm, which is relatively thin. There is no particular lower limit of the coating solution concentration, but considering the separation stability of the porous particles in the coating solution and the coating workability, the concentration of the resin solids excluding the porous particles is about 1% by mass or more. Preferably it is about 2 mass% or more.

  In the present invention, as described above, the outermost layer of the coating film is mixed with porous particles having pores of a predetermined size, and heat transfer characteristics are accelerated by accelerating heat transfer from the coating film surface to the outside air direction. Of course, it is possible to improve heat dissipation by utilizing only such an action, but these characteristics are combined with the heat dissipation improvement technique shown in the above-mentioned Patent Document 1. It is extremely effective to make it appear.

  That is, on the lower layer side of the outermost layer containing the porous particles, a lower coating film containing a radioactive additive as disclosed in Patent Document 1 is formed, and the thermal radiation characteristics of the lower coating film are utilized. It is also effective to further improve the heat dissipation characteristics. Specifically, infrared rays (wavelength: 4.5 to 15.4 μm) when the coated metal plate is heated to 100 ° C. by forming a lower layer coating film having improved heat dissipation characteristics by blending radioactive additives. If the integral emissivity is increased to 0.6 or more, the heat radiation characteristics are further improved in combination with the presence of the outermost coating film whose convective heat transfer performance is enhanced by blending the porous particles.

  The “integrated emissivity of infrared rays” means the ease of releasing (easy absorption) of infrared rays (thermal energy). Therefore, the higher the infrared emissivity, the greater the amount of heat energy released from the coating. For example, when 100% of thermal energy given to an object (in the case of the present invention, a painted metal material) is radiated, the infrared integrated emissivity is 1.

  In the present invention, the infrared integrated emissivity when heated to 100 ° C. is determined as described above. This is because the coated metal material of the present invention is a normal electronic device (although it differs depending on the application, In consideration of the fact that the operating atmospheric temperature is approximately 50 to 70 ° C. and about 100 ° C. at the maximum, the heating temperature was set to 100 ° C. in order to match the practical atmospheric temperature. However, according to the experiments by the present inventors, the infrared integrated emissivity when heated to 200 ° C. is only about 0.02 (ie, 2%) higher than the infrared integrated emissivity of 100 ° C. It is confirmed that they are the same.

The method for measuring the infrared integrated emissivity employed in the present invention is also clarified in the above-mentioned Patent Document 1, but it is as follows.
Apparatus: “JIR-5500 type Fourier transform infrared spectrophotometer” manufactured by JEOL Ltd. and radiation measurement unit “IRR-200”
Measurement wavelength range: 4.5 to 15.4 μm
Measurement temperature: Set the heating temperature of the test material to 100 ° C. Integration count: 200 times Resolution: 16 cm ⁻¹

  Using the above apparatus, the spectral radiant intensity (measured value) of the test material in the infrared wavelength region (4.5 to 15.4 μm) is measured. Since this actual measurement value is measured as a numerical value obtained by adding / adding the background radiation intensity and the device function, an emissivity measurement program [emissivity measurement program manufactured by JEOL Ltd.] is used to correct these values. Calculate the integral emissivity. Details of the calculation method are as follows.

In the formula, ε (λ) is the spectral emissivity (%) of the specimen at the wavelength λ, E (T) is the integral emissivity (%) of the specimen at the temperature T (° C.), M (λ, T) Is the spectral radiant intensity (measured value) of the test material at wavelength λ and temperature T (° C.), A (λ) is the instrument function, and K _FB (λ) is a fixed background at wavelength λ (the back surface does not vary with the test material) Spectral radiation intensity of ground), K _TB (λ, T _TB ) is wavelength λ, spectral radiation intensity of trapped black body at temperature T _TB (° C.), K _B (λ, T) is wavelength λ, temperature T (° C.) , And λ ₁ and λ ₂ mean the range of wavelengths to be integrated, respectively.

Here, A (λ: instrument function) and K _FB (λ: spectral radiant intensity of fixed background) are measured values of spectral radiant intensity of two blackbody furnaces (80 ° C., 160 ° C.), and Based on the spectral radiant intensity (calculated value from Planck's theoretical formula) of the black body in the temperature range, the following formula is used.

In the formula, M _{160 ° C.} (λ, 160 ° C.) is the spectral radiant intensity (measured value) of the black body furnace at 160 ° C. at the wavelength λ, and M _{80 ° C.} (λ, 80 ° C.) is the black at 80 ° C. at the wavelength λ. Spectral radiant intensity (actually measured value) of the body furnace, K _{160 ° C.} (λ, 160 ° C.) is a spectral radiant intensity of the black body furnace at 160 ° C. at a wavelength λ (calculated value from Planck's theoretical formula), K _{80 ° C.} ( (λ, 80 ° C.) means the spectral radiant intensity (calculated value from Planck's theoretical formula) of a black body furnace at a wavelength λ of 80 ° C., respectively.

In calculating the integral emissivity E (T = 100 ° C.), K _TB (λ, T _TB ) is taken into account when a trapped black body cooled with water is placed around the specimen. Because it is. By installing the trap black body, variable background radiation (meaning background radiation that varies depending on the specimen). Since the radiation from the surroundings of the specimen is reflected on the specimen surface, The actually measured value of the radiation intensity can be controlled to a low spectral radiation intensity (which appears as a numerical value obtained by adding the background radiation). As the trap black body, a pseudo black body having an emissivity of 0.96 is used, and K _TB [(λ, T _TB ): spectral radiant intensity of the trap black body at the wavelength λ and the temperature T _TB (° C.). ] Is calculated as follows.
K _TB (λ, T _TB ) = 0.96 × K _B (λ, T _TB )
In the formula, K _B (λ, T _TB ) means the spectral radiant intensity of a black body at a wavelength λ and a temperature T _TB (° C.).

  The coated metal material on which the lower coating film containing the radioactive additive was formed had an integral emissivity [E (T = 100 ° C.)] of infrared rays (wavelength: 4.5 to 15.4 μm) measured in this way. In addition, the infrared integrated emissivity (a) of the coated metal material on which the heat-radiating coating film is formed is preferably at least 0.6 or more. Moreover, in the case of the coating metal material in which the same heat dissipating coating film is formed also on the back surface, the product (a × b) of infrared integrated emissivities (a) and (b) on the front and back surfaces is 0.6 or more. Those satisfying the above are preferable.

  In other words, the infrared integrated emissivity emitted from the painted metal material is useful as an index indicating the heat dissipation effect of the painted metal material itself, and those whose values show “0.6 or more” are average values in the above infrared wavelength region. Therefore, in the present invention, the above value is set as a preferable integral emissivity. More preferably, it is 0.64 or more, More preferably, it is 0.72 or more.

  When carrying out the present invention, it is preferable that the infrared emissivity on one side which is the outer surface side of the housing is larger, the integral emissivity on the one side is 0.6 or more, more preferably 0.7 or more, and further Painted metal materials that are preferably 0.8 or more are recommended as the most preferred embodiment in the present invention.

  The infrared integrated emissivity is almost unaffected by the configuration of the outermost layer coating film containing the porous particles, and is almost uniquely determined by the configuration of the lower layer coating film containing the radioactive additive. Therefore, in a preferred embodiment of the present invention in which the lower layer coating film and the outermost layer coating film are combined, the above integrated emissivity of the lower layer coating film and the heat radiation effect by the convective heat transfer of the outermost layer coating film are exhibited. Will do.

Carbon black is most preferable as a radioactive additive to be blended in the lower layer coating film, but other oxides such as Co, Ni, Cu, Mn, Ag, Sn, sulfide, carbide, etc., and further TiO _2. Ceramics, iron oxide, aluminum oxide, barium sulfate, silicon oxide and the like can also be used. A preferable blending amount of these radioactive additives is 1% by mass or more, more preferably 2% by mass or more in terms of a solid content ratio in the lower layer coating film.

  A preferable size when carbon black is used as the radioactive additive is 5 nm or more and 100 nm or less in terms of average particle diameter. If the average particle size is less than 5 nm, it is difficult not only to obtain desired heat dissipation characteristics but also the coating stability tends to deteriorate and the appearance of the coating tends to deteriorate. On the other hand, even if the average particle size exceeds 100 nm, it is too large. This is because the heat dissipation characteristics are lowered and the appearance of the coating film tends to be non-uniform. Preferably they are 10 nm or more and 90 nm or less; More preferably, they are 15 nm or more and 80 nm or less. In addition to the heat dissipation characteristics, the optimum average particle diameter of carbon black is generally in the range of 20 to 40 nm when comprehensively considering the stability of the paint, the uniformity of the appearance after coating, and the like.

  The type of the resin used as the vehicle component of the outermost layer coating film and the lower layer coating film (the base resin forming the heat radiation coating film) is not particularly limited from the viewpoint of heat radiation characteristics, and is an acrylic resin or urethane resin. Resins, polyolefin resins, polyester resins, fluorine resins, silicon resins, blends and modified resins thereof, and the like can be used as appropriate. However, since the coated metal material of the present invention is used as a casing of an electronic device, corrosion resistance and workability are often required in addition to heat dissipation characteristics. Therefore, as the base resin, a non-hydrophilic resin [ Specifically, those satisfying a contact angle with water of 30 ° or more (more preferably 50 ° or more, more preferably 70 ° or more) are preferably used. Such a non-hydrophilic resin depends on the degree of mixing and the degree of modification, but for example, polyester resins, polyolefin resins, fluorine resins, silicone resins, and blends or modified resins thereof are preferred, among others. Preferred are polyester resins and modified resins thereof (epoxy-modified polyester resins, thermosetting polyester resins such as polyester resins having a phenol derivative introduced into the skeleton, or unsaturated polyester resins).

  If necessary, a crosslinking agent such as a melamine compound or an isocyanate compound can be added to these resins.

  Moreover, you may add another additive, for example, a rust preventive pigment, an antistatic agent, a weather resistance improving agent, etc. to the said outermost layer coating film and lower layer coating film in the range which does not impair the effect | action of this invention. Among other additives, a conductive filler is preferably used as an additive that gives excellent performance when blended on the lower coating film side.

  That is, the electronic device component to which the present invention is applied may cause an electromagnetic interference to the outside in addition to the problem of heat dissipation. Therefore, the coated metal material of the present invention used as a casing for the electronic device has an electromagnetic shielding property. For this purpose, it is possible to provide conductivity by adding a conductive filler to one or both of the outermost layer coating and the lower layer coating (preferably in the lower layer coating), and to provide electromagnetic shielding performance. It is recommended to do.

  Examples of the conductive filler used for such purposes include simple metals such as Ag, Zn, Fe, Ni, and Cu, and metal compounds such as FeP. Of these, Ni is particularly preferable. The shape is not particularly limited, but it is preferable to use a scaly shape in order to give excellent conductivity with a smaller amount. The blending amount of the conductive filler occupies in all the components constituting the coating film, including the type of base resin to be used and the crosslinking agent, heat-dissipating additive and other additives added as necessary. It is good to set it as the range of 5-50 mass% by a ratio (solid content conversion). If it is less than 5%, the desired conductivity imparting effect cannot be obtained. Therefore, it is preferably 15% or more, more preferably 20% or more. However, when the amount of the conductive filler exceeds 50% by mass, the processability of the coating film is lowered. In particular, when it is applied to a portion where a high degree of bending workability is required as a coated metal plate, it should be suppressed to 40% by mass or less, more preferably 35% by mass or less in order to maintain excellent workability.

  The conductivity index may be based on an electrical resistance of 100Ω or less, more preferably 10Ω or less. Here, the electrical resistance can be measured by the following method.

  “Loresta EP” manufactured by Mitsubishi Chemical as a conductivity measuring device and a two-probe probe manufactured by Mitsubishi Chemical (MCP-TP01) are used as the conductivity measuring device, and the thickness between the probe probe and the measurement sample is 0 when measuring. Two copper plates of 8 mm in size and 20 mm in size are placed so that the copper plates do not contact each other, and the resistance (Ω) of the test material is measured.

  In the present invention in which a metal is used as the base material, it is also effective to add a rust inhibitor as an additive other than the above. Specific examples include silica compounds, phosphate compounds, phosphite compounds, polyphosphate compounds, sulfur organic compounds, benzotriazole, tannic acid, molybdate compounds, tungstate compounds. Compounds, vanadium compounds, silane coupling agents and the like can be mentioned, and these can be used alone or in combination. Particularly preferred is a combination of a silica-based compound (for example, calcium ion-exchanged silica) and a phosphate-based compound, a phosphite-based compound, or a polyphosphate-based compound (for example, aluminum tripolyphosphate). Compound: (phosphate compound, phosphite compound, or polyphosphate compound) in a mass ratio of 0.5 to 9.5: 9.5 to 0.5 (more preferably 1: It is recommended to use in the range of 9-9: 1). By controlling in such a range, a coating film having both excellent corrosion resistance and workability can be obtained.

  As described above, the coating film characterizing the coated body of the present invention has been described in detail, but the most important point of the present invention is that the coating film, also the outermost coating film, or the configuration of this and the lower coating film, The kind of metal base material on which the coating film is formed is not particularly limited. Therefore, as the metal substrate used in the present invention, the most typical steel plates, specifically cold-rolled steel plates, hot-rolled steel plates, electrogalvanized steel plates (EG), hot-dip galvanized steel plates (GI), alloyed hot-dip zinc Plated steel sheets (GA), Al-Zn plated steel sheets, various plated steel sheets such as Al, steel sheets such as stainless steel sheets, non-ferrous metal sheets, etc. can be applied. In particular, pipes, wires, rods, deformed materials, etc. can all be used.

  In addition, the above metal material may be subjected to surface treatment such as chromate treatment or phosphate treatment for the purpose of improving corrosion resistance or adhesion of the coating film. A nonchromated metal material may be used, and any embodiment is included in the technical scope of the present invention.

  The coated body of the present invention can be produced by applying a coating containing the above-described components to the surface of a substrate by a known coating method and drying or heat baking. The coating method is not particularly limited. For example, the surface of a base material that has been cleaned and subjected to pre-coating treatment (for example, phosphate treatment, chromate treatment, etc.) as necessary is applied to a roll coater method, a spray method, or a curtain. Examples thereof include a method of applying a paint using a flow coater method and the like, passing it through a hot air drying oven, drying it, or baking and hardening it.

  When forming a multi-layered coating film having a lower layer coating under the outermost layer coating layer, after forming the lower layer coating layer by the method described above, the outermost layer coating layer is dried and solidified. A film should be formed. By the way, if the lower layer coating material and the outermost layer coating material are sequentially applied and then dried and solidified simultaneously, mutual diffusion and mixing of the lower layer coating material and the outermost layer coating material occurs. It is because it becomes difficult to obtain an outer layer coating film.

  The coated body of the present invention thus obtained has an excellent convective heat conduction effect in which a thin-walled skin coating film containing the above-mentioned porous particles is formed in the outermost layer, and preferably further has a radioactive additive on the lower layer side. It has excellent heat dissipation characteristics by forming a lower layer coating film containing, or more preferably, it can provide electromagnetic wave shielding properties by blending a conductive filler on the lower layer side to make a conductive coating film, It can be used very effectively as a housing material for protecting and storing electronic devices.

  An electronic device component that effectively exhibits the features of the present invention is an electronic device component that contains a heating element in a closed space, and all or part of the outer wall of the electronic device component is coated with the painted metal. Electronic equipment parts made of materials are also included.

  Such electronic equipment components include CD, LD, DVD, CD-ROM, CD-RAM, PDP, LCD and other information recording products; PC, car navigation, car AV and other electrical / electronic / communication related products; projectors, Specific examples include AV devices such as televisions, videos, and game machines; copiers such as copiers and printers; power supply box covers such as air conditioner outdoor units, control box covers, vending machines, and refrigerators.

  EXAMPLES 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 as a matter of course, and appropriate modifications are made within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example Electrogalvanized steel sheet subjected to chromate treatment (plate thickness: 0.8 mm, Cr adhesion amount: 20 mg / m ³ was used as a base plate, and a paint (base resin) blended with additives shown in Table 1 on one side thereof A polyester resin and a melamine resin as a crosslinking agent) were applied, followed by baking and drying to form a lower coating film.

  Next, a polyester resin paint blended with the fine particles shown in Table 1 was applied thereon, followed by baking and drying to form an outermost layer coating film. In this polyester-based resin coating material, porous silica having a large diameter of about 20 nm in diameter with a surface opening in each of the resin solid content in the coating material of 50% by mass and 7.5% by mass (Trade name “Mizukasil P-707” manufactured by Mizusawa Chemical Co., Ltd.) or a diameter having an open surface; zeolite having many pores of about 0.3 nm (trade name “Zeostar KA-100P” manufactured by Nippon Chemical Co., Ltd.) Was blended so as to be 10% by mass in the ratio of the dried coating film.

  For each of the obtained coated metal plates, heat transferability by convection was evaluated by the following method, and infrared (wavelength: 4.5 to 15.4 μm) integrated emissivity when heated to 100 ° C. was examined.

"Convection heat transfer evaluation method"
In order to evaluate the convection and heat transfer performance of each test steel plate, the representative temperature of the test steel plate heated at a uniform speed in the same direction was measured according to the following principle, and a relative evaluation was performed between the test steel plates.

principle:
As shown in FIG. 1, one side of test steel plates A and B having the same dimensions are heated with the same amount of heat (Q0), and air set at the same temperature T0 and the same flow velocity (V1) is flowed on the opposite side. If the heat passing performance of the test steel plate A is superior to that of the test steel plate B, a relationship of “TA <TB” is established between the surface temperature TA of the test steel plate A and the surface temperature TB of the test steel plate B. To do. In the figure, ha and hb are the heat transfer coefficients of the test steel plates A and B, A0 is the macroscopic surface area of the test steel plates A and B (that is, the pore area of the porous particles exposed on the surface is a negligible surface area, In the experiment, since the test plates of the same size were used, the values are the same).

The heat passing performance is determined by the amount of radiant heat transfer and the amount of convection heat transfer. If the emissivity (ε0) and air temperature (T0) of the test steel plate are determined, the radiant heat transfer amount (Q2) is as follows. Since it can be obtained by the equation, the remaining convective heat transfer amount (Q1) can be obtained as “Q1 = Q0−Q2”, and the quality of improvement in convective heat transfer can be determined.
Q2 = 5.67 × ε0 × A0 × {[(TA + 273) / 100] ⁴ − [(T0 + 273) / 100] ⁴ }

  From Table 1 above, it can be considered as follows.

  The code | symbol 1 is the blank material which used the electrogalvanized steel plate in which no coating film is formed as it is. Reference numeral 2 is a coated metal plate made of only a lower layer film containing the radioactive additive according to the invention of the prior application shown as Patent Document 1, and has a high heat emissivity and good heat dissipation, compared with a blank material. A temperature drop (heat radiation) effect of 6.3 ° C. is obtained.

  Reference numeral 3 is an embodiment of the present invention in which a heat-radiating lower layer coating film is formed and an outermost layer coating film satisfying the specified requirements of the present invention is formed thereon. A heat dissipation effect of 3 ° C. is obtained.

  Reference numeral 4 is an example using a high resin solid content concentration as a paint for forming the outermost layer coating film with respect to the reference numeral 3 because the pores of the porous particles have been blocked by the resin, The effect of forming the outermost layer coating film is not exhibited at all. Reference numerals 5 and 6 are fine particles of zeolite having fine pores that do not reach the size defined in the present invention but have fine pores as the porous particles. It is worse than the code | symbol 2 which provided only the coating film. This is considered to be because not only the zeolite does not have a heat dissipation effect due to convective heat transfer, but also the thermal radiation of the lower layer coating is inhibited by the outermost layer coating containing the zeolite.

  The thermal emissivity depends exclusively on the lower layer coating film, and the thermal emissivity of reference numerals 2 to 6 having the same configuration of the lower layer coating film shows a constant value regardless of the outermost layer coating film. .

It is principle explanatory drawing which shows the calculation method of the amount of radiant heat transfer (Q2) and convective heat transfer amount (Q1) of a coating metal plate.

Claims (4)

A coated metal material in which at least one layer of a coating film is formed on one side or both sides of a metal substrate,
The coating film has a lower coating film layer A containing a heat-dissipating additive and an outermost coating film B containing porous particles having pores of 1 to 1000 nm,
The outermost layer coating film B has a layer thickness (x) of 0.5 to 4 μm, an average particle diameter (y) of the porous particles of 1 to 8 μm, and satisfies the relationship of “x <y”. Yes,
At least a part of the porous particles are included in a state of being exposed on the surface layer side of the outermost layer coating film B , and the exposed pores on the surface of the porous particles are maintained in an open state,
A coated metal material excellent in heat dissipation, wherein an integral emissivity of infrared rays (wavelength: 4.5 to 15.4 μm) when the painted metal material is heated to 100 ° C. is 0.6 or more . The coated metal material according to claim 1, wherein the coating film contains 5 to 50% by mass of a conductive filler in a ratio (in terms of solid content) occupying the constituent components of the coating film . The painted metal material according to claim 1 or 2 , which is used for a casing of an electronic device having a heat source. An electronic device component incorporating a heat source, wherein at least a part of an outer wall of the electronic device component is made of the painted metal material according to any one of claims 1 to 3. parts.

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