JP4922746B2 - Resin-coated aluminum material, casing for electronic device or household appliance using the same, and electronic device or household appliance using the casing - Google Patents

Description

  The present invention relates to a resin-coated aluminum material used for a housing such as an electronic device that emits heat, a household electrical appliance, a heat sink, a reflector, and the like, and more specifically, heat dissipation and conductivity, workability, The present invention relates to a highly functional resin-coated aluminum material excellent in solvent resistance and corrosion resistance. Furthermore, this invention relates to the housing | casing for electronic devices or household appliances using the said resin coating aluminum material, and the electronic device or household appliances using this housing | casing.

  With the downsizing and high performance of electronic devices, heat emitted from these electronic components is often accumulated in a narrow space, and exhaust heat from the space has become a problem. That is, since the high temperature inside the device due to heat generation in the electronic device may impair the performance of the precise electronic device body, it is an important issue to efficiently discharge the heat to the outside.

In order to solve such problems, Patent Document 1 discloses a heat-radiating surface in which an outer layer coating and an inner layer coating are provided on a substrate surface made of metal or the like as a low-cost material with good workability and heat dissipation. A heat-radiating surface-treating material using an inner layer coating containing 0.03-70% by weight of a dry weight of a pigment having a heat emissivity of 70% or more is described. This pigment is infrared-radiative, and a resin-coated material containing this pigment is an organic film, so that bending workability is improved as compared with an inorganic film. However, although this material is molded into a casing or the like by press molding or the like with high processing strength, it cannot be said that the workability is sufficient because the surface lubricity of the organic coating is poor. For this reason, there are problems of quality deterioration that the corrosion resistance of the processed portion is inferior, and problems that the product value and productivity are reduced when a large film crack or scratch occurs, leading to an increase in cost.
JP 2002-228085 A

Furthermore, as a material for electronic device parts such as drive cases such as CD-ROM, personal computer related equipment and measuring instruments, electrical characteristics (grounding and shielding properties) that do not impair the performance of precision electronic equipment have been hitherto. It was required to have. As a material that satisfies such requirements, Patent Document 2 describes a resin-coated metal plate for electronic device components having a surface provided with a resin coating layer having a thickness of 0.1 to 10 μm. Here, the resin coating layer includes one or more of polyester, epoxy, phenol, and alkyd, and 2 to 60 parts by weight of nickel powder with respect to 100 parts by weight of the resin. The nickel powder is at least one selected from the group consisting of spherical, spike spherical, or scaly single particles having an average maximum major axis of 0.1 to 100 μm and chain nickel in which nickel particles are bonded to each other. Selected from.
JP 2001-205730 A

Patent Document 3 describes a metal plate for electric and electronic equipment in which a resin film is provided on the surface of the metal plate. Here, the resin film contains at least one selected from the group of acrylic resin, epoxy resin, and urethane resin as a resin component, and contains 1 to 50% by weight of moisture and 0.1 to 20% by weight of lubricant. And the thickness is 0.05 to 5 μm.
JP 2002-275656 A

Patent Document 4 describes a double-side pre-coated aluminum plate for the purpose of imparting antistatic properties (surface conductivity) and preventing the occurrence of coating cracking and coating peeling in press working. This double-sided pre-coated aluminum plate is a second organic resin system containing a conductive film on the other surface, which is formed by applying and curing a first organic resin-based paint on one surface of the aluminum plate and curing. A coating film is applied and cured to form a conductive film, which is excellent in press moldability and conductivity.
JP 2003-286585 A

  In the conductive resin-coated aluminum materials and the like described in Patent Documents 1 to 4 above, it has been possible to meet the demand for conductivity to some extent. However, with recent downsizing and higher functionality of electronic devices, a large amount of heat is released from electronic components as described above. As a result, in the electronic device component material, the heat inside the housing is transferred into the housing, and there is a problem of impairing the performance of the precise electronic device body. It is possible to improve heat dissipation by increasing the thickness of the thermal radiation resin coating. However, when the film thickness is increased, the electrically insulating resin component is sufficiently covered with the conductivity-imparting component and the conductivity tends to decrease, so that it is very difficult to achieve both conductivity and heat dissipation.

Patent Document 5 describes a precoated aluminum plate that is provided with a thermosetting resin film containing graphite powder and nickel powder as a pre-coated aluminum plate that achieves both conductivity and heat dissipation.
JP 2005-305993 A

  Such an aluminum material satisfies both heat dissipation and electrical conductivity, but when graphite powder is contained in the coating, the graphite may form a layered aggregate in the coating. As a result, the graphite is easily removed from the coating and the corrosion resistance is lowered. In recent years, the manufacture of electrical and electronic equipment casings has been widely performed not only in Japan but also in Taiwan and Southeast Asian countries. When aluminum materials exported to these countries are stored, it is often exposed to environments where the temperature and humidity are more severe than those in Japan, so it is important that the aluminum materials have sufficient corrosion resistance.

  The present invention provides a resin-coated aluminum material having both good heat dissipation and conductivity, and excellent workability, solvent resistance and corrosion resistance, and for electronic equipment or household appliances using the resin-coated aluminum material. And an electronic device or household appliance using the casing.

  As a result of daily research, the inventors of the present invention include a thermosetting resin composed of a polyester-based resin and a melamine-based resin, graphite powder, and nickel powder on at least one surface of an aluminum substrate provided with a chemical film on both sides. It has been found that by providing a resin film to be used, both the heat dissipation performance and the conductivity performance can be improved. And by further research, by adding calcium ion exchange-type silica in such a resin film, without reducing the heat dissipation and conductivity, and various performances such as workability and solvent resistance, along with corrosion resistance It has been found that the anti-aggregation action of graphite can be improved. Further, by further research, the present invention was completed by finding the appropriate amount of each component and the appropriate range of properties.

  The present invention is the resin according to claim 1, comprising a base material of aluminum or an aluminum alloy, a chemical conversion film formed on both surfaces of the base material, and a thermosetting resin film formed on at least one of the chemical conversion film. A coated aluminum material, wherein the thermosetting resin film is a thermosetting resin comprising a polyester resin component and a melamine resin component, a graphite powder having an average particle size of 0.1 to 30 μm, and 0.5 A nickel powder having a maximum long axis average value of ˜100 μm and calcium ion exchanged silica, graphite powder is contained in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of the thermosetting resin, and the nickel powder is a thermosetting resin. 10 to 100 parts by weight with respect to 100 parts by weight, and calcium ion-exchange silica is 3 to 60 parts with respect to 100 parts by weight of thermosetting resin. A resin-coated aluminum material containing a part by weight and having a thickness of the thermosetting resin film of 5 μm or less was obtained.

  According to a second aspect of the present invention, the thermosetting resin includes 10 to 50 parts by weight of the melamine resin component with respect to 100 parts by weight of the polyester resin component.

  According to a third aspect of the present invention, the thermosetting resin film contains at least one selected from an anionic compound, a cationic compound, a nonionic compound, and a polymer compound as a dispersant.

  According to a fourth aspect of the present invention, a thermosetting resin film is formed on one chemical conversion film, and a white resin film containing a white pigment is formed on the other chemical conversion film.

  This invention made it the housing | casing for electronic devices or household appliances using the resin-coated aluminum material as described in any one of Claims 1-4 in Claim 5. Furthermore, in Claim 6, it was set as the electronic device or household appliances which used such a housing | casing.

  The highly functional resin-coated aluminum material of the present invention is excellent in heat radiation and surface conductivity, and is excellent in press workability due to good surface lubricity. The resin-coated aluminum material of the present invention is further excellent in reflectivity, solvent resistance and corrosion resistance. Therefore, this resin-coated aluminum material is extremely useful as a housing material for materials that require heat dissipation, such as electronic devices such as personal computers, household appliances such as refrigerators, indoor units of air conditioners, and radiators of outdoor units. is there.

A. Resin-coated aluminum material
A-1. Aluminum base material The aluminum base material used in the present invention is not particularly limited, but has sufficient strength to form and hold a casing, and has sufficient press workability during drawing and bending. Therefore, 1000 series, 3000 series and 5000 series aluminum alloy plates are preferred. As the aluminum substrate, those having a thickness of 0.1 to 2.0 mm are usually used.

A-2. As the chemical conversion film formed on the surface of the chemical conversion aluminum substrate, a coating type film and a reactive type film can be used. Either a coating type film or a reactive type film may be used, and it is not particularly limited. However, it is preferable to use a reactive chemical film having good adhesion to both the aluminum substrate and the resin film. The reactive chemical conversion film is specifically a film formed with a treatment liquid such as phosphate chromate, chromate chromate, zirconium phosphate, titanium phosphate or the like. In particular, a phosphoric acid chromate film is preferable in terms of versatility and cost. Rather than directly forming the thermosetting resin film on the aluminum substrate surface, the adhesion of the thermosetting resin film is improved by providing a chemical conversion film between the aluminum substrate and the thermosetting resin film. Thereby, the effect of preventing the occurrence of cracks in the thermosetting resin film is improved, and the workability is improved.

A-3. Thermosetting resin coating Heat on one or both of the chemical conversion coatings formed on both sides of the aluminum substrate exhibits excellent infrared absorption (radiation) properties in the infrared region, particularly in the 5-12 μm wavelength region. A curable resin film is formed. A thermosetting resin containing a polyester resin component and a melamine resin component is used as the base resin of such a thermosetting resin film, and a polyester resin crosslinked with a melamine resin component is preferably used. The thermosetting resin film contains graphite powder, nickel powder, and calcium ion exchange type silica.

(1) Base resin According to Planck's law, the radiant heat from an electronic device is effective in improving the heat dissipation by improving the thermal radiation in the infrared region having a peak at a wavelength of 8 to 10 μm. By using a resin containing a polyester resin component and a melamine resin component, such heat dissipation can be improved. According to Kirchhoff's law, a material having high thermal emissivity and thermal absorption rate and having high infrared absorption can be said to have high infrared emission.

  As the polyester resin to be used, those having a number average molecular weight of 8000 to 25000 are preferred from the viewpoint of processability and paintability. When the number average molecular weight is less than 8000, bending workability is lowered due to a decrease in flexibility of the thermosetting resin film. On the other hand, when the number average molecular weight exceeds 25000, the viscosity of the coating material for coating increases rapidly, resulting in a decrease in paintability. The glass transition temperature is preferably −10 to 70 ° C. from the viewpoint of workability and film hardness. If the glass transition temperature is lower than −10, wrinkles are likely to occur during processing such as press molding due to softening accompanying a decrease in coating hardness. On the other hand, when the glass transition temperature exceeds 70 ° C., bending workability is reduced due to a decrease in flexibility of the coating film.

  As the melamine-based resin, a methylated melamine-based resin, a butylated melamine-based resin, or the like is used, and a methylated melamine-based resin is preferable from the viewpoint of processability. The melamine resin has good infrared radiation (absorptivity) in a wide infrared wavelength range, and is blended at a ratio of 10 to 50 parts by weight, preferably 20 to 40 parts by weight with respect to 100 parts by weight of the polyester resin. When the blending ratio of the melamine-based resin is less than 10 parts by weight, the degree of crosslinking of the film becomes insufficient, and the solvent resistance, bending workability and other general physical properties of the coating film are deteriorated. Press molding or the like is used when manufacturing a housing for an electronic device or home appliance using an aluminum base material. However, since pressing oil or the like is used at the time of molding, it is necessary to clean it with an appropriate solvent after molding. . For this reason, if the solvent resistance of the thermosetting resin film is inferior, it becomes difficult to use press oil. On the other hand, when the blending ratio of the melamine-based resin exceeds 50 parts by weight, the crosslinking reaction proceeds excessively, the coating film becomes hard, and bending workability and lubricity are deteriorated.

(2) Graphite powder Graphite powder is contained in the thermosetting resin film as a lubricity impart to the coating film and as a heat dissipation impart by infrared radiation. The average particle size of the graphite powder used is 0.1 to 30 μm, preferably 0.1 to 20 μm. If the average particle size is less than 0.1 μm, the dispersibility of the graphite powder is lowered, making it difficult to form a coating material, and the processing cost into an ultrafine powder is increased. On the other hand, if the average particle size exceeds 30 μm, the graphite powder tends to fall off from the thermosetting resin coating, resulting in a decrease in corrosion resistance, solvent resistance and bending workability.

  The graphite powder is contained in a proportion of 20 to 100 parts by weight with respect to 100 parts by weight of the thermosetting resin as the base resin. If the content ratio is less than 20 parts by weight, the absolute amount of graphite powder per unit area of the thermosetting resin film is insufficient, and the effect of improving heat dissipation cannot be sufficiently obtained. On the other hand, when the content exceeds 100 parts by weight, it becomes difficult to form a thermosetting resin film, and the graphite powder tends to fall off from the resin film, resulting in a decrease in corrosion resistance, solvent resistance, and moldability.

  There are artificial types and natural types of graphite powder, but any type can be used in the present invention. Artificial types include those manufactured using petroleum as a raw material and those obtained by chemically treating natural types. Natural types include soil, scales, and scales. Either such an artificial type or a natural type may be used, or any two or more types may be mixed and used.

  In addition to graphite, carbon black, ferromanganese metal oxide, copper chrome metal oxide, and the like are known as infrared radioactive pigments. General carbon black has a primary particle size on the order of nm and has a very large surface area, so that the viscosity of the coating material increases rapidly, making it difficult to form a coating material. On the other hand, iron manganese metal oxides and copper chromium metal oxides are inferior in infrared radiation having a wavelength of 10 μm or less. However, carbon black having a large primary particle size or carbon black having a large aggregated particle size may be used in addition to the graphite powder.

(3) Nickel powder Nickel powder is contained in the thermosetting resin coating to impart conductivity to the coating. There are various types of nickel powder, such as spherical, chain-like, and scale-like, and there are no particular limitations. However, chain-like and scale-like ones are particularly preferred because of their good workability and conductivity. A mixture of one or more of these types is used.

  The average value of the maximum major axis of the nickel powder used is 0.5 to 100 μm. If the average value of the maximum major axis is less than 0.5 μm, the variation in conductivity becomes large and unstable, resulting in a decrease in conductivity. On the other hand, if the average value of the maximum major axis exceeds 100 μm, the nickel powder tends to be detached from the thermosetting resin film, so that the corrosion resistance, solvent resistance, and bending workability are lowered.

  The nickel powder is contained at a ratio of 10 to 100 parts by weight with respect to 100 parts by weight of the thermosetting resin as the base resin. Metal powders other than nickel powder are effective for imparting electrical conductivity, but nickel powder is particularly used from the balance of material cost and conductive performance. When the content ratio of the nickel powder is less than 10 parts by weight, a sufficient conductivity imparting effect cannot be obtained. On the other hand, when the content exceeds 100 parts by weight, it is difficult to form a thermosetting resin film, and nickel powder is easily removed from the resin film, resulting in a decrease in corrosion resistance, solvent resistance, and moldability.

(4) Calcium ion exchange type silica The thermosetting resin coating also contains calcium ion exchange type silica. Calcium ion-exchanged silica is one in which calcium ions are bonded to silanol groups on the silica surface and is usually very effective as a rust preventive pigment.

  By adding such calcium ion exchange type silica to the paint film, the present inventors have made it possible for the silica particles to collide inside the paint when the paint is dispersed or during re-stirring. It has been found that an effect of preventing the aggregation of can be obtained. As a result, special effects of improving appearance, improving solvent resistance, improving corrosion resistance, and reducing pigment loss are obtained by the action of preventing the formation of aggregates. In other words, by using calcium ion exchange type silica, the effect of calcium ion exchange type silica itself on the corrosion resistance, as well as the improvement of solvent resistance and corrosion resistance by preventing the aggregation of graphite, and the reduction of pigment dropout are obtained. Synergistically effective.

The calcium ion exchange type silica is contained in a proportion of 3 to 60 parts by weight, preferably 4 to 20 parts by weight, with respect to 100 parts by weight of the thermosetting resin as the base resin. When the content of calcium ion-exchanged silica is less than 3 parts by weight, it is not possible to obtain a sufficient effect of improving the corrosion resistance, and a sufficient effect of improving the solvent resistance and corrosion resistance is obtained due to insufficient anti-aggregation action of graphite. Is difficult. On the other hand, when the content ratio exceeds 60 parts by weight, the absolute amount of calcium ion exchanged silica in the coating film becomes excessive, cracking and peeling of the coating film are likely to occur, and lubricity and solvent resistance are inferior.
In addition, as an average particle diameter of the calcium ion exchange type | mold silica to be used, a thing of 1-10 micrometers is preferable. If it is less than 1 μm, sufficient corrosion resistance and anti-flocculation action of graphite cannot be obtained, and if it exceeds 10 μm, cracking and peeling of the coating film are likely to occur.

(5) Dispersant The thermosetting resin film may contain a dispersant. Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound. One or two or more kinds contained in these same compounds, or two or more kinds contained in these different compounds can be contained. Examples of the anionic compound include sulfate-based, sulfonate-based, and phosphate-based compounds. Examples of the cationic compound include amines, amine salts, ammonium salts, and the like. Nonionic compounds include esters, ethers, phenols and the like. As the polymer compound, there are many types including various polymers singly or as a mixture.

  By including such a dispersant in the thermosetting resin film, the wettability between graphite and the thermosetting resin is improved, and the graphite powder can be sufficiently covered with the thermosetting resin film, thereby preventing the dropping. The content ratio of the dispersant is preferably 30 parts by weight or less with respect to 100 parts by weight of the thermosetting resin as the base resin. If the dispersant exceeds 30 parts by weight, the viscosity of the coating film tends to increase and storage stability decreases, and the nickel powder in the resin coating tends to aggregate instead, and the conductivity may decrease. . Furthermore, the resin coating film may be inhibited from curing, and the solvent resistance may be lowered.

(6) Formation of thermosetting resin film In order to form a thermosetting resin film, a liquid film coating for a thermosetting resin film is applied (applied) to the chemical conversion film surface formed on the surface of the aluminum substrate. Bake this.
Such a coating material uses a thermosetting resin as a base resin, graphite powder, nickel powder, calcium ion exchange silica, and, if necessary, a dispersant, a lubricity-imparting component and an additive as described below as a solvent. Prepared by dissolving and dispersing. The solvent is not particularly limited as long as each component can be dissolved or dispersed, and a general organic solvent can be used.

  As a coating method of the coating film, a roll coater method, a roll squeeze method, a chemi coater method, an air knife method, a dipping method, a spray method, an electrostatic coating method and the like are used, and the coating film has excellent uniformity and productivity. A good roll coater method is preferred. For drying the coating, a general heating method, dielectric heating method, or the like is used.

  Baking at the time of forming the film is preferably performed under the conditions that the baking temperature (reached surface temperature) is 200 to 250 ° C. and the baking time is 30 to 90 seconds. When the baking temperature in film formation is less than 200 ° C. or when the baking time is less than 30 seconds, the film is not sufficiently formed and the film adhesion is lowered. When the baking temperature exceeds 250 ° C. or the baking temperature exceeds 90 seconds, the coating component is denatured.

(7) Film thickness of thermosetting resin film The film thickness of a thermosetting resin film shall be 5 micrometers or less. When the film thickness exceeds 5 μm, the absolute amount of the graphite powder in the resin film becomes excessive, and the film tends to crack or peel off. On the other hand, if the film thickness exceeds 5 μm, the electroconductive thermosetting resin component is likely to be coated with the nickel powder, which is a conductivity-imparting component, and the conductivity may be lowered. Accordingly, in order to further prevent cracking and peeling of the coating and decrease in conductivity, it is preferable that the thickness of the thermosetting resin coating is 1.5 μm or less.

A-4. When the said thermosetting resin film is formed on one of the chemical conversion films formed on both surfaces of the white resin coated aluminum base, the white resin film can be formed on the other chemical conversion film. The white resin film is a resin coating film containing a white pigment. By using this as a reflection surface, a material satisfying reflectivity, heat dissipation, and conductivity can be produced. The resin-coated aluminum material provided with such a white resin film can be used for liquid crystal reflectors and various illumination reflectors by using a white resin-coated film as a surface for light.

  As the base resin of the white resin film, at least one thermosetting resin selected from fluorine resin, epoxy resin, polyester resin, acrylic resin, and urethane resin is used. As the white pigment, a pigment composed of at least one selected from titanium oxide, zinc white, zinc sulfide, barium sulfate, and calcium carbonate is used.

  The white pigment is contained in a proportion of 70 to 150 parts by weight with respect to 100 parts by weight of the base resin. When the content ratio is less than 70 parts by weight, a sufficient reflection effect cannot be obtained, and when it exceeds 150 parts by weight, the coating film is easily cracked or peeled off. The thickness of the white resin coating film is preferably 30 to 150 μm. If the thickness is less than 20 μm, a sufficient reflection effect cannot be obtained. If the thickness exceeds 150 μm, the reflection effect is saturated and uneconomical.

  The white resin film is formed by painting (applying) the liquid film paint on the surface of the chemical conversion film and baking it. The solvent of the coating film paint, and the method and conditions of application and baking are performed in the same manner as the thermosetting resin film described above.

A-5. Lubricating component For the purpose of further improving the workability of the resin-coated aluminum material according to the present invention, a lubricating component may be added to the thermosetting resin that is the base resin. As the lubricity-imparting component, lubricants such as olefin wax such as polyethylene wax, fluorine resin such as PTFE (polytetrafluoroethylene), paraffin wax, microcrystalline wax, beeswax, lanolin and carnauba wax are used. The addition amount of the lubricity-imparting component is preferably 30 parts by weight or less with respect to 100 parts by weight of the thermosetting resin as the base resin. When the lubricity-imparting component exceeds 30 parts by weight, solvent resistance decreases, blocking, conductivity decreases, and coating film residue occurs during processing, which is suitable as a material for housings of electronic devices and home appliances. Absent.

A-6. Additives The coating for thermosetting resin coatings contains solvents, leveling agents, anti-bacterial agents, matting agents, etc., which are used in ordinary coatings to ensure paintability and general performance as precoat materials. You may let them.

  Note that the resin-coated aluminum material according to the present invention may have a form in which a thermosetting resin film is formed on both surfaces thereof, a thermosetting resin film is formed on one surface, and a white resin film is formed on the other surface. Alternatively, a thermosetting resin film may be formed on one surface and a resin film other than that defined in the present invention may be formed on the other surface. These forms are appropriately selected depending on the application and required characteristics of the resin-coated aluminum material.

  The thermosetting resin film coating applied on one chemical conversion coating and the white resin coating applied on the other chemical conversion coating may be baked simultaneously or separately. In addition, the thermosetting resin film paint used in the present invention applied on one chemical conversion coating and the resin film paint other than that prescribed in the present invention applied on the other chemical conversion coating are simultaneously baked. May be baked separately.

B. Housing for electronic equipment or home appliances The resin-coated aluminum material produced as described above is applied to a volatile press oil on the surface and then subjected to a molding process such as a press process, and so on. A housing for an electronic device or a housing for a household electric appliance such as a refrigerator is manufactured. Many press oils used at the time of molding are usually high in viscosity and need to be cleaned after processing, requiring a large amount of cleaning agent (organic solvent). However, since the resin-coated aluminum material of the present invention is excellent in surface lubricity, it can be suitably used even with a press oil having a low viscosity. In this case, cleaning after processing can be simplified. It is also possible to reduce the amount of press oil used.

C. Electronic equipment or home appliances The case made using the resin-coated aluminum material according to the present invention is further subjected to fine bending or the like, and the surface may be painted. And various apparatuses and components are built in the inside, and it assembles into a desired electronic device and household appliances.

  Hereinafter, preferred embodiments of the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

Examples 1-18 and Comparative Examples 1-10
First, a paint for a thermosetting resin film was prepared as follows. A thermosetting resin was prepared by adding methylated melamine resin at a ratio shown in Table 1 to 100 parts by weight of a commercially available polyester resin. Next, Table 1 shows each of graphite, nickel, calcium ion-exchanged silica, and dispersant with respect to 100 parts by weight of the thermosetting resin (based on all) (the polyester resin and the methylated melamine resin are combined). A part by weight was added and dispersed in an organic solvent (so-called “thinner”) mainly composed of cyclohexanone and high-boiling aromatic naphtha to prepare a coating material for a thermosetting resin film. Here, for example, in Example 1, 400 g of polyester resin, 100 g of methylated melamine resin, 200 g of graphite, 240 g of nickel, 40 g of calcium ion-exchanged silica, and 15 g of dispersing agent with respect to about 1 kg of organic solvent. Blended.

Next, using the coating material thus prepared, a resin-coated aluminum material was prepared as follows.
An aluminum plate (JIS A5052, plate thickness 0.5 mm) was used as the aluminum substrate. This base material was degreased with a commercially available aluminum degreasing agent, dried after washing with water. Next, the aluminum substrate subjected to the degreasing treatment was subjected to chemical conversion treatment using a commercially available phosphoric acid chromate treatment solution so that the chromium amount in the film was 30 ± 5 mg / m ² . Furthermore, the coating material shown in Table 1 was applied to both surfaces of the chemical conversion treated aluminum substrate with a roll coater, and baked at PMT (maximum plate temperature) 200 ° C. to 250 ° C. for 60 seconds. A schematic cross-sectional view of the resin-coated aluminum material 4 thus produced is shown in FIG. In the figure, 1 is a thermosetting resin film, 2 is a chemical conversion film, and 3 is an aluminum substrate.

  Performance evaluation was performed by the following test method about the sample of the produced resin-coated aluminum material. Details of each test method are shown below.

(Conductivity test)
The electrical conductivity of the sample was measured by the four-terminal method when the silver probe (diameter 5 mm, tip 2.5R) was brought into contact with the coating surface with a load of 100 g. The measured values were evaluated based on the following criteria: A: 4Ω or less, ○: 4Ω to more than 7Ω, Δ: more than 7Ω to 10Ω or less, ×: more than 10Ω. When the electrical resistance value exceeded 10Ω, the desired electrical characteristics (grounding property and shielding property) could not be obtained when processed into an electronic device component, and therefore x was rejected, and the others were passed.

(Heat dissipation test)
The heat dissipation test was performed by preparing a housing as described below and measuring the surface temperature of the housing. A casing having a bottom surface of 150 mm × 150 mm and a height of 100 mm was produced from the resin-coated aluminum material. The produced housing is shown in FIG. In the figure, reference numeral 5 denotes a light source, and the others are the same as those in FIG. In addition, the display of the chemical conversion film provided between the thermosetting resin film 1 and the aluminum base material 3 is abbreviate | omitted. A 60 W light bulb was installed as the light source 5 inside the case, energized to emit light and generate heat, and the temperature of the case surface when the temperature inside the case reached a steady state was measured.

  Measurement values are: ◎: 28 ° C. or less, ○: 28 ° C. to 30 ° C., △: 30 ° C. to 32 ° C., Δ: 32 ° C. to 35 ° C., x: 35 ° C. It was evaluated with. When the housing surface exceeded 35 ° C., the temperature drop was small and the heat dissipation was insufficient, so that the housing surface temperature exceeded 35 ° C. x was rejected, and the others were accepted.

(Workability test: Lubricity)
Among the workability, the lubricity is measured by the coefficient of friction using a slip tester (Bowden type) manufactured by Shinko Machine Co., Ltd .: ○: Less than 0.10, Δ: 0.10 or more and less than 0.15 Evaluation was made based on the criteria of possible, x: not less than 0.15 and unusable. ○ and Δ were accepted and x was rejected.

(Workability test: Bending workability)
Among the workability, the bending workability is 180 ° 3T bending with the evaluation surface outside, and the crack of the thermosetting resin film is visually observed. ◎: No crack of the paint film, ○: Very light coating Evaluation was made based on the criteria that there was a crack in the film but good, Δ: there was a crack in the small coating, but it could be used, and x: there was a crack in the large coating that could not be used. ◎, ○, and Δ were accepted, and x was rejected.

(Processability test: Tape test)
After the observation of the bending workability test, a cellophane tape was adhered to the bent portion, and a tape test was performed to observe the degree of peeling of the coating film when the tape was peeled off rapidly to evaluate the peeling property of the coating film. Evaluation was based on the criteria of ○: no peeling, Δ: slight peeling but usable, ×: peeling. ◎ and △ were accepted, and x was rejected.

(Solvent resistance test)
The solvent resistance test was carried out by impregnating a wiper with a trichlene solution as a chlorinated solvent, rubbing the sample surface 30 times while applying a constant load (1 kg), and visually evaluating the surface condition after the test. Evaluation: ○: Good without peeling of coating film, ○ △: Slight peeling of coating film is good, △: Can be used even though peeling of coating film is observed, ×: Unusable coating film is severely peeled off Evaluated by criteria. ○, ○ △ and △ were accepted, and x was rejected.

(Corrosion resistance test)
Corrosion resistance was evaluated by a salt spray test (salt concentration: 5%) using a CAS tester CASSER-12L-ISO manufactured by Suga Test Instruments Co., Ltd. The corrosion of the resin-coated aluminum material surface after spraying for 100 hours and after spraying for 200 hours was observed and evaluated. Evaluation was based on the following criteria: ◎: No corrosion, ○: Very slight corrosion but good, △: Minor corrosion, △: Corrosion is observed but usable, ×: Corrosion is severe and unusable . ◎, ○, ○ △ and △ were accepted, and x was rejected.

  Table 1 shows the evaluation results of the conductivity, processability, and solvent resistance tests. As is clear from the results shown in Table 1, Examples 1 to 18 were good in heat dissipation and conductivity, and good in workability, solvent resistance and corrosion resistance.

  On the other hand, Comparative Examples 1 to 10 failed in any of heat dissipation, conductivity, workability, solvent resistance and corrosion resistance, and were unsuitable as resin-coated aluminum materials for electronic devices or home appliances. It was.

Specifically, Comparative Example 1 was inferior in corrosion resistance because the amount of calcium exchanged silica added was insufficient.
In Comparative Example 2, since the addition amount of the calcium exchange type silica is excessive, the corrosion resistance is good. However, when bending is performed, the calcium exchange type silica is used as a starting point to cause cracking, and the bending workability is inferior. . Moreover, since there was too much quantity of calcium exchange-type silica with respect to a surface area, lubricity and solvent resistance were inferior.
Comparative Example 3 was inferior in conductivity because the amount of nickel powder added was insufficient.
In Comparative Example 4, since the amount of nickel powder added is excessive, film formation of the thermosetting resin film is hindered, and the nickel powder falls off from the resin layer, so that bending workability, solvent resistance, and corrosion resistance (200 hour spray) Was inferior.
In Comparative Example 5, the average value of the maximum major axis of the nickel powder was small, so the conductivity was inferior.
In Comparative Example 6, since the average value of the maximum major axis of the nickel powder was large, when bending was performed, cracking occurred with the nickel powder serving as a base point, and bending workability was inferior. Moreover, since the nickel powder was easily removed, the solvent resistance and corrosion resistance (200 hours spraying) were inferior.
In Comparative Example 7, the heat dissipation was inferior because the amount of graphite powder added was insufficient.
In Comparative Example 8, since the amount of graphite powder added was excessive, the graphite powder dropped off from the resin layer, and the peelability, solvent resistance, and corrosion resistance (200 hours spraying) were inferior.
In Comparative Example 9, since the average particle size of the graphite powder was large, when the tape test was performed, the graphite powder became a base point and cracks occurred, and the peelability was poor. Moreover, since the graphite powder was easily removed, the solvent resistance and corrosion resistance (200 hour spray test) were inferior.
In Comparative Example 10, since the thermosetting resin film was thick, the nickel powder was too coated with an electrically insulating resin and the conductivity was inferior.

Examples 19 and 20
In Example 19, the same thermosetting resin coating material as in Example 1 was prepared, and in Example 20, the same thermosetting resin coating material as in Example 12 was prepared. Further, in the same manner as in Example 1, the aluminum substrate was degreased, washed and dried, and then subjected to chemical conversion treatment on both surfaces of the degreased aluminum substrate. Further, the same coating material as in Example 1 was applied in the same manner as in Example 1 in Example 19, and the same coating material as in Example 12 was applied in the same manner as in Example 12 on the one surface of the chemical conversion treated aluminum base material.
Subsequently, the coating for white resin film was similarly applied to the other surface of the chemical conversion treated aluminum base using the same roll coater as in Example 1. The coating material for white resin coating is a coating material containing 120 parts by weight of titanium oxide with respect to 100 parts by weight of acrylic resin.

  Thus, what applied the thermosetting resin film coating material to the one surface of the aluminum base material and applied the white resin film coating material to the other surface was baked under the same conditions as in Example 1. In both Examples 19 and 20, the thickness of the thermosetting resin film after baking was 1.0 μm, and the thickness of the white resin film was 110 μm.

  With respect to the sample thus produced, tests for conductivity, heat dissipation, workability, solvent resistance, and corrosion resistance were carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

  Furthermore, in Examples 19 and 20, a light reflectivity test was also performed as described below, and the light reflectivity was also evaluated.

(Light reflectivity test)
Total reflectance is a multi-light source spectrocolorimeter MSC-IS-2DH (using an integrating sphere, diffused light illumination 8 ° direction light reception) manufactured by Suga Test Instruments Co., Ltd., and the total reflectance at a wavelength of 550 nm (including a regular reflection component). Was expressed as a percentage with respect to the light reflectivity test when a white plate made of BaSO _{4 was} used as a standard plate. In addition, in order to use as a liquid crystal reflecting plate, it is suitable that the total reflectivity is 90% or more, and 90% or more was determined to be acceptable (O). The results of the light reflectivity test are also shown in Table 2.

  As is clear from the results shown in Table 2, in Examples 19 and 20, both heat dissipation and conductivity were good, and workability, solvent resistance, and corrosion resistance were also good. In Examples 19 and 20, the total reflectance of the light reflecting surface was 95%, indicating excellent light reflectivity.

  The resin-coated aluminum material of the present invention has good conductivity, heat dissipation, workability (lubricity, bending workability, peelability), solvent resistance and corrosion resistance. Accordingly, the resin-coated aluminum material of the present invention is a housing for a personal computer, an outdoor unit of an air conditioner, a radiator of an indoor unit, a household appliance such as a refrigerator, etc. It is suitable as a material such as a reflector. Further, when a white resin coating is further provided, it is excellent in reflectivity, so that a drive case such as a CD-ROM, a personal computer related device, a measuring instrument, etc. that require grounding, shielding, and antistatic properties are required. It is also suitable as a housing material for electronic device component materials.

It is sectional drawing which shows typically the resin-coated aluminum material of this invention. It is sectional drawing which shows typically the apparatus which evaluates the heat dissipation of the resin-coated aluminum material of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermosetting resin film 2 Chemical conversion film 3 Aluminum base material 4 Thermosetting resin coating aluminum material 5 Light source

Claims (6)

A resin-coated aluminum material comprising an aluminum or aluminum alloy base material, a chemical conversion film formed on both surfaces of the base material, and a thermosetting resin film formed on at least one of the chemical conversion film,
The thermosetting resin film is a thermosetting resin composed of a polyester resin component and a melamine resin component, a graphite powder having an average particle size of 0.1 to 30 μm, and a maximum major axis average value of 0.5 to 100 μm. The graphite powder is contained in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of the thermosetting resin, and the nickel powder is 10 parts by weight with respect to 100 parts by weight of the thermosetting resin. ˜100 parts by weight, and calcium ion exchange type silica having an average particle size of 1 to 10 μm is 3 parts per 100 parts by weight of the thermosetting resin in order to prevent the aggregation of graphite inside the thermosetting resin film. A resin-coated aluminum material, which is contained in 60 parts by weight and the thermosetting resin film has a thickness of 5 μm or less.
  The resin-coated aluminum material according to claim 1, wherein the thermosetting resin contains 10 to 50 parts by weight of a melamine resin component with respect to 100 parts by weight of a polyester resin component.   The resin-coated aluminum material according to claim 1 or 2, wherein the thermosetting resin film contains at least one selected from an anionic compound, a cationic compound, a nonionic compound, and a polymer compound as a dispersant. .   The resin-coated aluminum according to any one of claims 1 to 3, wherein a thermosetting resin film is formed on one chemical conversion film, and a white resin film containing a white pigment is formed on the other chemical conversion film. Wood.   The housing | casing for electronic devices or household appliances using the resin-coated aluminum material as described in any one of Claims 1-4.   The electronic device or household appliances using the housing | casing of Claim 5.

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