JP6313639B2 - Pre-coated aluminum plate for capacitor case - Google Patents

Description

  The present invention relates to a precoated aluminum plate used by being molded into a capacitor case such as an aluminum electrolytic capacitor.

  Aluminum has various features such as low specific gravity and good thermal conductivity, and is therefore used in various applications. Since this aluminum is excellent in corrosion resistance in a natural environment, there are many cases in which surface treatment for preventing corrosion is not performed, but in recent years, surface treatment for the purpose of imparting functions has been increasingly performed.

  For example, in applications that require lightness, such as notebook PCs, flat-screen TVs, car stereos, etc., the use of precoated aluminum plates made of aluminum plates and pre-coated with a functional film (precoat film) is increasing. Yes. The use of a pre-coated aluminum plate has the advantage that it is superior in productivity and cost compared to an after-coating method in which an aluminum plate that has not been surface-treated in advance is individually surface-treated after press molding.

  A cover of a slim type optical disk drive device mounted on a notebook personal computer is one of typical applications in which a pre-coated aluminum material is employed. The pre-coated aluminum material used in this application has (1) lubricity (to eliminate the step of washing the press oil and to reduce the manufacturing cost, thus enabling continuous molding with quick-drying press oil that does not require washing. No. 1), (2) Anti-fingering / fingerprint resistance (to improve appearance quality), (3) Conductivity (to prevent antistatic and grounding), etc. are required.

  As an example of a precoated aluminum plate that satisfies these requirements, for example, a technique described in Patent Document 1 is known. In Patent Document 1, a predetermined corrosion-resistant film and a predetermined resin film are formed on at least one surface of an aluminum plate having a predetermined arithmetic average roughness Ra, and the surface resistance value is defined to improve conductivity. On the other hand, an aluminum plate for electronic equipment that satisfies other required performances is disclosed.

  Incidentally, as housings (covers and the like) of consumer electronic devices such as an optical disk drive device assumed in Patent Document 1, an aluminum plate formed into a box shape by bending 90 degrees has been applied. The technology for producing a box-type housing by bending is high in productivity because a coiled plate is used and continuous molding with a progressive die is established as a technology. In addition, the technique for producing a box-shaped casing by bending has established a continuous molding technique using a quick-drying press oil, so that a washing step after press molding is unnecessary and it is advantageous in production cost. Therefore, it can be said that the technique of manufacturing a box-type housing by bending is an excellent method.

However, on the other hand, a case manufactured by bending always has a gap in the corner of the side wall. For this reason, in an application in which a liquid material such as an electrolytic solution is used inside, as in the case of an electrolytic capacitor or the like, it is not possible to prevent liquid leakage from a gap existing in the corner of the side wall portion.
A container shape such as a capacitor case that does not allow liquid leakage is not a box shape bent by bending, but a container shape obtained by drawing. And when applying a precoat aluminum plate to a container-shaped product, it is calculated | required that not only the aluminum plate which is a raw material but a precoat film | membrane should follow the big deformation | transformation accompanying a drawing process.

  For example, Patent Document 2 discloses a precoated aluminum plate that assumes a large deformation of the precoat film accompanying drawing. Such a pre-coated aluminum plate is obtained by comparing the gel fraction value of the pre-coated film before and after the heat treatment at 220 ° C. as the intermolecular cross-linked state of the thermosetting resin formed on the surface of the aluminum plate. The gel fraction value after the treatment is continuously reduced from the gel fraction value before the heat treatment. Further, this pre-coated aluminum plate is controlled so that the reduction width from the value of the gel fraction before the heat treatment at the time when the heat treatment at 220 ° C. is performed for 10 minutes is less than 10%. Satisfies workability.

  As a technique other than the pre-coated aluminum plate mentioned above, a film laminated aluminum plate obtained by laminating a thermoplastic resin film excellent in workability is used in the case of an electrolytic capacitor. The film-laminated aluminum plate has a characteristic that is advantageous for drawing because the resin molecules constituting the film are not cross-linked, and thus the film can be greatly deformed.

  For example, Patent Document 3 includes a thermoplastic resin film provided on the surface of an aluminum plate and a thermosetting resin coating layer provided on the surface of the thermoplastic resin film, thereby maintaining moldability. On the other hand, a resin-coated laminated aluminum plate for an electronic component case that prevents the discoloration of the resin coating layer has been disclosed. Patent Document 3 describes that a polyamide-based resin such as nylon or a saturated polyester-based resin such as PET is used as the thermoplastic resin film.

Further, for example, Patent Document 4 describes a resin-coated aluminum alloy plate for a capacitor case in which a chemical conversion film is provided on an aluminum alloy plate and a resin layer is provided thereon. In Patent Document 4, the resin in the capacitor-coated resin-coated aluminum alloy plate is mainly composed of an epoxy resin, and at least one or more selected from the group of phenol, acrylic, urethane, and urea are added. It is stated that it consists of In Patent Document 4, the number average molecular weight of the resin is 5000 to 30000, the lubricant is contained in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin, and the tensile strength of the resin layer is 40 N / mm ^2. As mentioned above, the elongation is 2% or more, the thickness is 3 to 30 μm, and the cross-cut remaining rate in the cross-cut test when the resin-coated aluminum alloy sheet is rolled to 40% is described as being 60% or more. Has been.

Japanese Patent No. 4237975 Japanese Patent No. 4783051 Japanese Patent No. 4003915 JP 2006-334917 A

  However, when the inventions described in Patent Documents 1 to 4 are applied to a capacitor case, the following problems occur.

  The invention described in Patent Document 1 is an invention that assumes an optical disk drive as its application. Therefore, as described above, it is considered that the invention is based on the premise that the casing is manufactured by bending. Therefore, when the invention described in Patent Document 1 is applied to a capacitor case, it is considered that the deformation of the film cannot follow a molding with a large amount of deformation such as drawing, and the film is cracked or peeled off. In addition, since the invention described in Patent Document 1 has a very thin film thickness, it is difficult to color all colors as well as the black appearance assumed by the present invention.

  The invention described in Patent Document 2 assumes drawing processing and is also assumed to be applied to a capacitor case. However, it does not take into account the low temperature and short time of soldering, which are technically required, and extra energy is required, increasing the burden on the environment. In addition, there is no description on the coloring and pigment addition including the black appearance assumed by the present invention.

  As described in Patent Document 3, a film laminate material made of a thermoplastic resin as a base resin and laminated on the surface of an aluminum plate uses a thermoplastic resin film. Has its own limits. For example, when a polyamide-based thermoplastic resin typified by nylon is used as a base resin, it has good adhesion to an aluminum plate and has excellent moldability. There is a problem that the base resin is easily yellowed or browned. Furthermore, when using a saturated polyester-based thermoplastic resin such as PET as the base resin, it has good adhesion to the aluminum plate, exhibits excellent moldability, and does not easily discolor the base resin even in high-temperature environments. However, since the base resin is easily hydrolyzed, it tends to be inferior in durability under a high-temperature and humid atmosphere. In addition, the low temperature soldering and shortening of the low temperature soldering assumed by the present invention are not considered.

  Patent Document 3 also describes an example of a film laminate material in which a polyolefin-based resin typified by polyethylene or polypropylene is used as a base resin. In such a configuration, the base resin is basically used. Is composed of only carbon and hydrogen and does not contain nitrogen or oxygen. Accordingly, there is no origin of a functional group or chemical bond such as a hydroxyl group, a carboxyl group, an ester bond, an isocyanate group, a urethane bond, an amino group, or an amide bond, resulting in poor adhesion to the aluminum plate.

  The invention described in Patent Document 4 is an invention related to a thermosetting resin precoated aluminum material based on an epoxy resin, and is assumed to be applied to a capacitor case. In general, an epoxy resin has characteristics such as excellent heat resistance as a resin. However, since it is essentially a hard resin, there is a limit to further improve the deep drawability. In addition, Patent Document 4 does not consider the black appearance assumed by the present invention, coloring, and pigment addition.

  In addition, the pre-coated aluminum plate may not require cleaning after molding if the molding conditions are mild, but it is necessary to use press oil in drawing or the like where the molding conditions are severe. When press oil is used, it is necessary to clean the precoated aluminum plate using a cleaning agent such as trichlene after drawing. Accordingly, the precoated aluminum plate for drawing is required to have excellent cleaning durability.

  The present invention has been made in view of the above problems, and relates to a precoated aluminum plate that is used by being molded into a capacitor case such as an aluminum electrolytic capacitor, and has excellent deep drawability and washing durability required for the same application. Of course, the following features that are not considered in the prior art for the same application, that is, the capacitor is likely to be warmed in the soldering process, so that the soldering process can be performed at a low temperature or in a short time. Another object of the present invention is to provide a precoated aluminum plate for a capacitor case having an excellent black appearance.

A pre-coated aluminum plate for a capacitor case according to the present invention is a pre-coated aluminum plate for a capacitor case comprising an aluminum plate and a film formed on one side surface of the aluminum plate, and the surface of the aluminum plate is preliminarily alkaline degreasing liquid. After the degreasing treatment, the coating film is subjected to phosphoric acid chromate treatment, and the coating film comprises a crosslinked polyester resin obtained by crosslinking a polyester resin having a glass transition temperature of 20 to 60 ° C. with a melamine curing agent, carbon black And a copper phthalocyanine compound, the content of the carbon black contained in the coating is 3% by mass or more and 18% by mass or less, and the integrated emissivity of infrared rays having a wavelength of 3 to 30 μm is 25 ° C. 0.7 or more, and the thickness of the film is 3 μm or more and 12 μm or less. Gel fraction was constituted of meeting 95% or less 70%.

According to such a configuration, the pre-coated aluminum plate for a capacitor case according to the present invention is subjected to phosphoric acid chromate treatment after the surface of the plate has been previously degreased with an alkaline degreasing solution. The formed film contains a cross-linked polyester resin obtained by cross-linking a polyester resin having a predetermined glass transition temperature with a melamine-based curing agent, and satisfies the gel fraction as specified. And cleaning durability. In addition, carbon black and copper compound are added to the film at a predetermined ratio. By controlling the ratio, the film has a beautiful black appearance even at a film thickness in the above-mentioned range, and the moldability and tightening performance are reduced. I will not let you. Furthermore, since the integral emissivity of infrared rays is secured to 70% (0.7) or more, the film absorbs heat efficiently during soldering, and the capacitor is likely to warm up. It is estimated that it will improve. Moreover, since the pre-coated aluminum plate for a capacitor case according to the present invention contains a copper phthalocyanine compound, the black appearance can be further improved.

In the precoated aluminum plate for capacitor case according to the present invention, the content of the copper phthalocyanine compound contained in the film is preferably 0.1% by mass or more and 1.6% by mass or less. With such a configuration, the carbon black content can be reduced while improving the black appearance of the pre-coated aluminum plate for a capacitor case according to the present invention, so that the economics of the film can be increased. .

  Since the pre-coated aluminum plate for a capacitor case according to the present invention has the above-described configuration, it has an excellent black appearance and infrared integrated emissivity. Therefore, by using the pre-coated aluminum plate for a capacitor case according to the present invention, the solderability is excellent, that is, the soldering process can be performed at a low temperature or a short time, and a capacitor having an excellent black appearance and That case is obtained. Moreover, since the pre-coated aluminum plate for a capacitor case according to the present invention has the above configuration, it has excellent formability and cleaning durability.

It is a fragmentary sectional view showing typically one embodiment of the precoat aluminum plate for capacitor cases concerning the present invention. It is a schematic diagram which shows the process of performing a drawing process and a ironing process with respect to a test material, and producing a bottomed cylindrical container. Specimen No. It is a figure which shows the temperature rise curve of 1, 4, 10, 12.

[Precoated aluminum plate for capacitor case]
Hereinafter, a mode (embodiment) for carrying out the precoated aluminum plate for a capacitor case according to the present invention will be specifically described with reference to the drawings as appropriate.
In the drawings to be referred to, FIG. 1 is a partial sectional view schematically showing one embodiment of a pre-coated aluminum plate for a capacitor case according to the present invention.

  As shown in FIG. 1, a capacitor case pre-coated aluminum plate 1 (hereinafter simply referred to as “pre-coated aluminum plate 1”) includes an aluminum plate 2 and a pre-coated film 3 formed on one side surface of the aluminum plate 2. ing. A phosphate chromate film 4 is formed between the aluminum plate 2 and the precoat film 3. In addition, although the phosphoric acid chromate film | membrane 4 is formed in the other side surface of the precoat aluminum plate 1 shown in FIG. 1, the aspect which has not formed the precoat film | membrane is illustrated, The precoat film | membrane is also illustrated on this other side surface. Can be formed. Each configuration will be described below.

<Aluminum plate>
The aluminum plate 2 may be made of aluminum or an aluminum alloy. The aluminum plate (aluminum plate or aluminum alloy plate) 2 used in the present invention is not particularly limited, but a case of a deep drawing shape is performed. An industrial pure aluminum plate, a 3000 series Al-Mn alloy board can be used conveniently. In particular, aluminum plates such as A1070, A1050, A1100, A3003, A3004, and A3104 specified in JIS H 4000: 2006 are recommended. Various types of tempering and plate thickness can be selected and used according to the purpose.

<Precoat film>
The precoat film 3 includes a crosslinked polyester resin 7 obtained by crosslinking a polyester resin having a glass transition temperature of 20 to 60 ° C. with a melamine curing agent, carbon black 5 dispersed in the crosslinked polyester resin 7 and a copper compound. 6 and a resin film. This precoat film 3 has an infrared integrated emissivity of 3 to 30 μm at a temperature of 25 ° C. of 0.7 or more, a film thickness of 3 μm to 12 μm, and a gel fraction of 70% to 95%. Satisfies the following:

[Crosslinked polyester resin]
The crosslinked polyester resin 7 is a main component of the precoat film 3, and as described above, a polyester resin having a glass transition temperature of 20 to 60 ° C. is subjected to an intermolecular crosslinking reaction using a melamine curing agent. Is.

  There are film laminates that use thermoplastic resins as the base resin as those that do not undergo intermolecular crosslinking by thermosetting reaction, but as described in the above-mentioned prior art, those using thermoplastic resins as the base resin have various points. This creates a practical problem. However, when a resin that undergoes intermolecular cross-linking by thermosetting reaction or the like is selected as the cross-linked polyester resin 7, the resin originally has a functional group for intermolecular cross-linking, so that adhesion to the aluminum plate 2 is improved. Excellent. Moreover, by being crosslinked, the washing durability, chemical resistance, and heat resistance are enhanced, and the hydrolysis resistance can be improved.

  In addition to polyester resin, epoxy resin, vinylidene fluoride resin, acrylic resin, silicon polyester resin, etc. are widely known as resin for aluminum plate coating. In view of this, it is not suitable for the present invention.

  As the polyester resin, it is desirable to use a saturated polyester resin obtained by condensation polymerization of a polyhydric alcohol and a polybasic acid.

  Among these, examples of the polyhydric alcohol include dihydric alcohols such as ethylene glycol, propylene glycol, neopentyl glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, glycerin, trimethylolethane, Trihydric alcohols such as methylolpropane, and tetrahydric or higher alcohols can be used.

  Examples of polybasic acids include dibasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, and sebacic acid, tribasic acids such as trimellitic anhydride, and tetravalent or higher polybasic acids. A basic acid or the like can be used.

  Only one kind of these polyhydric alcohols and polybasic acids may be used, or two or more kinds thereof may be used simultaneously for condensation polymerization. Moreover, the glass transition temperature of a polyester resin can be adjusted by combining these components.

  The glass transition temperature is one of the transition temperatures of the resin. Generally, a resin at a temperature higher than the glass transition temperature is a soft rubber, and a resin at a temperature lower than the glass transition temperature is a hard glass. Therefore, in order for the precoat film 3 to follow a process with large deformation such as deep drawing or ironing, it is theoretically necessary to set the glass transition temperature to the processing temperature or lower. In reality, however, polymer substances have a wide range of molecular weights and branch structures are formed in the molecules, and the primary structure is not uniform. In addition, the arrangement of molecules and higher-order structures are uniform when viewed microscopically. I can't say that. Therefore, the glass transition temperature is merely a representative value, and the transition gradually occurs in a temperature range having a certain width. Furthermore, the polyester resin has a relatively high elongation except for a part of the state (a state in which crystallization is promoted in a state of a thermoplastic resin that does not cause a cross-linking reaction) even in a glassy state having a glass transition temperature or lower. Therefore, within a certain range, molding is possible even if a resin having a high glass transition temperature is used as the crosslinked polyester resin 7. On the other hand, when the resin having a glass transition temperature that is too low is used as the crosslinked polyester resin 7, the precoat film 3 becomes too soft and wrinkles are likely to enter.

  Therefore, in the present invention, the glass transition temperature of the crosslinked polyester resin 7 contained in the precoat film 3 needs to be in the range of 20 to 60 ° C. When the glass transition temperature of the crosslinked polyester resin 7 is less than 20 ° C., the film 3 becomes too soft and wrinkles easily occur. On the other hand, when the glass transition temperature of the crosslinked polyester resin 7 exceeds 60 ° C., the moldability of the precoated aluminum plate 1 is lowered, and the film is easily peeled off when the case is molded. The glass transition temperature of the crosslinked polyester resin 7 is preferably 30 to 45 ° C., for example. In addition, the glass transition temperature here means what was measured by the differential scanning calorimetry (Differential Scanning Calorimetry; DSC) method.

  Moreover, a crosslinking reaction does not occur only with the polyester resin. In order to cause the crosslinking reaction required in the present invention, a curing agent that reacts with the carboxyl group of the polyester resin is added, or a component that functions in the same manner as the curing agent is generated in the polyester resin itself. It is necessary to modify the polyester resin using a chemical reaction. Functional groups that react with these hydroxyl groups and carboxyl groups include isocyanate groups, amino groups, hydroxyl groups, and the like. By adding a substance having three or more of these functional groups as a curing agent, the crosslinking reaction is easily promoted. Is possible. Examples of such curing agents include polyisocyanate compounds, melamine compounds, epoxy compounds, amino compounds, phenolic compounds, urea compounds, etc., but from the viewpoint of cleaning durability, melamine-based curing agents are essential in the present invention. .

[Carbon black]
By including the carbon black 5 in the cross-linked polyester resin 7 of the precoat film 3, it is possible to ensure that the precoat film 3 has an infrared integrated emissivity of 0.7 or more at a temperature of 25 ° C. at a wavelength of 3 to 30 μm. it can. Further, by incorporating carbon black 5 in the crosslinked polyester resin 7 of the precoat film 3, a black appearance can be imparted.

  The type, size, form, etc. of carbon black 5 are particularly limited as long as the above conditions are satisfied, that is, the integrated emissivity of infrared rays having a wavelength of 3 to 30 μm satisfies 0.7 or more at a temperature of 25 ° C. Various modifications are possible.

  As for the content of the carbon black 5, when the ratio of the pre-coat film 3 is less than 3% by mass, the film thickness for satisfying 0.7 or more at the temperature of 25 ° C. of the infrared integrated emissivity having a wavelength of 3 to 30 μm Since it becomes too thick, a moldability falls. On the other hand, when the content of the carbon black 5 is less than 3% by mass, the color tone of the precoat film 3 becomes reddish and a good black appearance cannot be obtained. On the other hand, when the content of the carbon black 5 exceeds 18% by mass, the precoat film 3 itself becomes brittle and easily peels off from the aluminum plate 2, so that the moldability is lowered. Therefore, the content of carbon black 5 in the precoat film 3 needs to be 3% by mass or more and 18% by mass or less. In addition, it is preferable that the content rate of the carbon black 5 shall be 6 to 11 mass%.

[Copper compound]
The copper compound 6 is for ensuring a good black appearance of the precoat film 3 and is contained in the crosslinked polyester resin 7 of the precoat film 3. When the copper compound is not included, when drawing is performed, when the film thickness is reduced, or when the amount of added carbon black is reduced, the color tone becomes reddish black and the appearance may be deteriorated. Such deterioration in appearance can be improved by including a copper compound.

Examples of the copper compound that produces such an effect include CuO, CaO.CuO.4SiO ₂ , CuCr ₂ O ₄ , and CuMn ₂ O _4. An excellent copper phthalocyanine compound is desirable. Further, since copper phthalocyanine has an absorption peak even in the near infrared region having a wavelength of 1000 nm or less, when the infrared emissivity of 3 to 30 μm described in the present invention is the same, the addition of copper phthalocyanine is slightly more. However, it can be said that there is also a supplementary effect that heat absorption increases.

  If the content of the copper compound exceeds 0% by mass, that is, even if it is small, if it is contained in the precoat film 3, the effect of improving the appearance can be obtained according to the amount added. . In addition, from the viewpoint of a more reliable appearance improvement effect and economy, the content of the copper compound contained in the precoat film 3 is preferably, for example, 0.1% by mass or more and 1.6% by mass or less, More preferably, it is 0.2 mass% or more and 1.4 mass% or less.

[Film thickness]
The film thickness of the precoat film 3 is 3 μm or more and 12 μm or less. If the film thickness of the precoat film 3 is less than 3 μm, the color tone of the precoat film 3 and the infrared integrated emissivity with a wavelength of 3 to 30 μm cannot be sufficiently obtained. On the other hand, when the film thickness of the precoat film 3 exceeds 12 μm, the precoat film 3 becomes brittle and easily peels at the time of molding, which may deteriorate the moldability. The film thickness of the precoat film 3 can be controlled by adjusting the amount of the precoat film paint applied.

[Gel fraction of precoat film]
In the present invention, the gel fraction of the precoat film 3 is 70% or more and 95% or less. Since the gel fraction is a parameter that is a measure of the degree of crosslinking reaction of the thermosetting resin film, the gel fraction of the crosslinked polyester resin 7 alone should be discussed, but the precoat film 3 is a crosslinked polyester. Since carbon black 5 and copper compound 6 are included as essential components in addition to resin 7, it is difficult to strictly measure the gel fraction of only crosslinked polyester resin 4 (base resin). Therefore, in the present invention, the gel fraction of the precoat film 3 is substituted and defined by this gel fraction.

  If the gel fraction of the precoat film 3 is 70% or more, the cross-linked polyester resin 7 forming the precoat film 3 has a high cross-linking density, in addition to cleaning durability, chemical resistance, heat resistance, The precoat film 3 excellent in hydrolyzability can be obtained. On the other hand, the upper limit of the gel fraction is 95% and it is necessary not to exceed this. When the gel fraction exceeds 95%, the film becomes too hard, and therefore, when formed into an elongated cylindrical case, it becomes easy to peel off, resulting in poor moldability. In order to make the gel fraction 70% or more and 95% or less, it is preferable that the baking temperature when baking the coating film is, for example, about 200 to 280 ° C.

  Moreover, the measuring method of a gel fraction can be performed by the method based on JISK6796: 1998 (however, the extraction solvent uses not xylene but 2-butanone). That is, the specimen of the precoated aluminum plate 1 is immersed for 60 minutes in boiled 2-butanone (MEK), and the mass change of the precoated aluminum plate 1 before and after immersion is measured. Thereafter, the mass change of only the precoat film 3 is calculated by measuring the mass of the aluminum plate 2 in which only the precoat film 3 is completely dissolved, and it is assumed that the component that has not eluted into the MEK has undergone a crosslinking reaction. The ratio is calculated as a gel fraction.

[Integrated emissivity of precoat film]
In the precoat film 3 of the present invention, the integrated emissivity of infrared rays having a wavelength of 3 to 30 μm is 0.7 or more at a temperature of 25 ° C. The emissivity is a proportional coefficient obtained by dividing the infrared radiation from the object surface by the infrared radiation from the black body surface, and is defined for light of a specific wavelength at a specific temperature. Possible numerical values range from 0 (white body) to 1 (black body). The larger the number, the greater the infrared radiation. The integral emissivity is obtained by integrating this in a certain wavelength range. According to Planck's radiation method, the pre-coated aluminum plate 1 according to the present invention is generated in the vicinity of room temperature, which is the working temperature range (operating temperature range), more specifically in the practical temperature range of 273 to 373 K (0 to 100 ° C.). The possible infrared wavelengths are concentrated in the wavelength range of 3 to 30 μm. In other words, infrared light in a wavelength region that is out of the range of this wavelength region may be ignored. For this reason, the present invention is limited to infrared rays in the wavelength region of 3 to 30 μm at 25 ° C.

  The pre-coated aluminum plate 1 according to the present invention is intended to realize a low temperature or short time in the soldering process due to the capacitor being easily warmed in the soldering process, by efficiently absorbing heat from the surface of the case. Realized. Therefore, it should be discussed in terms of the absorptivity instead of the emissivity. However, according to Kirchhoff's law, the absorptivity and emissivity are equivalent in the thermal equilibrium state. Can be used as is. Since the temperature rise of the capacitor due to heat in the soldering process is a phenomenon in a non-equilibrium state rather than a thermal equilibrium state, the above explanation is not strictly correct, but as will be shown later in Examples and Comparative Examples, emissivity It has been confirmed that the higher example reaches a higher actual temperature by lower temperature and shorter heating than the lower example (see FIG. 3, which will be described later). That is, in the present invention, it is confirmed that the object is achieved if the infrared emissivity under the above-described conditions is 0.7 or more.

  With respect to the precoat film 3, when the integrated emissivity of infrared rays at a wavelength of 3 to 30 μm is less than 0.7, the ability to absorb heat from the surface of the precoat film 3 decreases, so it takes time for the capacitor to warm up during soldering. Insufficient temperature. In the present invention, the infrared integrated emissivity is, for example, preferably 0.75 or more, and more preferably 0.8 or more. In order to set the integral emissivity of infrared rays at a wavelength of 3 to 30 μm to 0.7 or more, the above-mentioned predetermined amount of carbon black may be added, and the predetermined amount of copper compound may be added incidentally.

  The infrared integrated emissivity of the precoat film 3 can be measured, for example, with a commercially available simple emissometer (D & S Model AE manufactured by D and S). Since the measurement wavelength region of the simple emissometer is 3 to 30 μm, the displayed number can be adopted as the integral emissivity defined in the present invention.

[Others]
The precoat film 3 can contain additives that impart various functions within the scope of the present invention.
For example, in order to further improve moldability, a lubricant such as polyethylene wax, carnauba wax, microcrystalline wax, lanolin, Teflon (registered trademark) wax, silicone wax, graphite lubricant, molybdenum lubricant, etc. Species or two or more can be contained. Organic fine particles and inorganic fine particles can also be added for the purpose of improving the paste of the printing ink. In addition to this, as long as the effects of the present invention are exhibited, an antioxidant, an ultraviolet absorber, an antistatic agent, and the like can be contained.

<Ground treatment>
In order to improve the adhesion with the precoat film 3, the surface of the aluminum plate 2 needs to be subjected to phosphoric acid chromate treatment after degreasing treatment with an alkaline degreasing solution in advance. Many degreasing agents for weak alkaline aluminum such as sodium carbonate, sodium silicate, and sodium phosphate are commercially available as degreasing agents suitable for such purposes, and any of these can be used in the present invention. In addition to an alkali salt as an alkali builder, a chelating agent, an activator for oil removal, and the like may be included. The degreasing capacity of alkaline chemicals can be controlled by the main component, concentration, and processing temperature of the alkali used. However, if the degreasing capacity is strengthened, a lot of smut will be generated, and subsequent washing with water will not be performed sufficiently. On the contrary, the adhesion between the aluminum plate 2 and the precoat film 3 may be lowered. Further, a sodium hydroxide-based strong alkaline degreasing agent having a pH exceeding 12 can be used. However, when this is used, the aluminum surface is strongly etched, so that it is necessary to remove smut. Therefore, it is preferable to perform acid cleaning with sulfuric acid or nitric acid after degreasing.

The aluminum plate 2 that has been subjected to alkali degreasing is then subjected to phosphoric acid chromate treatment. The phosphoric acid chromate treatment is a reaction type chemical conversion formed by spraying a treatment liquid composed of phosphoric acid, hydrofluoric acid or chromic anhydride onto the surface of the aluminum plate 2 or immersing the aluminum plate 2 in the treatment liquid. This is a treatment, and a film mainly composed of chromium phosphate (trivalent) is formed. The thickness of the film thus formed can be measured relatively easily and quantitatively by using a conventionally known fluorescent X-ray method, so that the precoated aluminum plate 1 can be measured without hindering productivity. Quality control can be performed. In addition, it is preferable that it is 10-50 mg / m < ² > in metal Cr conversion value as the adhesion amount of a base-treatment film. If the adhesion amount is less than 10 mg / m ² , the entire surface of the aluminum plate 2 cannot be uniformly coated, and the corrosion resistance is lowered. Moreover, when it exceeds 50 mg / m < ² >, when the precoat aluminum plate 1 is shape | molded, it will become easy to produce a crack in the membrane | film | coat itself of a surface treatment.

[First embodiment]
Next, the precoated aluminum plate of the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.

In the examination of the pre-coated aluminum plate according to the present invention, the aluminum plate used as a material was a 0.3 mm thick material having an alloy number of A1100-H24. As a base treatment, the substrate was degreased with a sodium carbonate weak alkaline degreasing agent and then subjected to a phosphoric acid chromate treatment. However, no. No. 23 (hereinafter simply referred to as “Sample No. 23” in accordance with the No. of the test material) was used as a comparative material for the base treatment in which neither degreasing nor phosphoric acid chromate treatment was performed. . The condition of the phosphoric acid chromate treatment was 20 mg / m ² in terms of chromium adhesion. The mechanical properties of the aluminum plate used were a tensile strength of 130 MPa, a proof stress of 120 MPa, and an elongation of 8%.

  Next, with respect to the aluminum plate subjected to the ground treatment (the aluminum plate where only No. 23 is not ground-treated), the coating material having the components described in the precoat film coating column in Table 1 is applied to one surface of the bar coater. It was applied with. And the precoat aluminum plate was manufactured by heating a coating material at the temperature described in the baking temperature of Table 1, and it was set as the test material. Note that the baking temperature was the temperature at which the material finally reached, and the baking time was set so that the total time from the start to the end of overheating was 40 seconds.

  Here, in the base resin shown in Table 1, “polyester melamine” is a polyester resin blended with a melamine curing agent, “polyester isocyanate” is a polyester resin blended with an isocyanate curing agent, “ “Epoxyurea” is a compound in which a urea-based curing agent is blended with an epoxy-based resin, and “epoxyphenol” is a compound in which a phenol-based curing agent is blended in an epoxy-based resin. Moreover, the glass transition temperature shown to a table | surface is a glass transition temperature in each said resin.

  The necessary physical properties of the test material manufactured as described above were measured. That is, the integrated emissivity of infrared rays having a wavelength of 3 to 30 μm at 25 ° C. and the gel fraction of the coating were measured. In addition, since the measuring method and measuring apparatus of the integral emissivity have already been described, they are omitted, and the gel fraction will be described next.

(Measurement of gel fraction)
The gel fraction was measured using a test material cut into 10 cm × 10 cm from the test material. After the test material was previously dried at 80 ° C. for 60 minutes, the initial mass (a) was measured, and the test material was immersed in boiled MEK for 60 minutes to elute uncrosslinked components. And the test material was dried at 150 degreeC for 60 minute (s), the residual MEK in a membrane | film | coat was dried, and mass (b) after extraction was measured. Finally, the film was completely dissolved in fuming nitric acid, and the mass (c) of the aluminum plate alone was measured. Here, (a)-(c) is the mass of the original precoat film only, and (b)-(c) can be regarded as the crosslinked film mass, so the gel fraction expressed by the following formula is It represents the degree of crosslinking.
(Gel fraction) = ((b)-(c) / (a)-(c)) × 100 (unit%)

  Next, the test material was examined for moldability and durability (cleaning durability) against a cleaning process after molding.

(Drawing formability)
FIG. 2 is a schematic diagram showing a process of producing a bottomed cylindrical container by performing drawing processing and ironing processing on the test material. The drawability of the test material was examined by the process shown in FIG.
First, after punching a cylindrical blank, drawing was performed. Next, a 12 mmφ × 15 mmL cylindrical drawn product (intermediate molded product) was obtained by redrawing. Furthermore, iron was added to the intermediate molded product so that the reduction rate of the thickness of the cylindrical side wall portion was 20%, trimmed, and processed into a final 10 mmφ × 20 mmL cylindrical container shape to obtain a final molded product. The results of evaluating the film state of the final molded product obtained at this time were defined as moldability in Table 1. The press oil used was an aqueous emulsion wax mainly composed of a fatty acid ester and a surfactant. The processing was performed at room temperature (35 ° C.).

  As for the evaluation of the film state, the moldability was excellent (◎) when no abnormal appearance was observed, good when the appearance was changed but there was no abnormality such as film peeling (○), peeling occurred The case was judged as bad (x).

(Washing durability)
A rubbing test was performed using trichlene as a cleaning agent. That is, gauze was wound around the tip of a 2-pound hammer and fixed with a rubber band, and trichrene was impregnated therein, and then was reciprocated 10 times on the film. Thereafter, the appearance of the film was visually confirmed. Excellent cleaning durability when the surface of the film is not abnormal (◎), discoloration and scratches, but the coating film is not dissolved and the aluminum base is not exposed, and the cleaning durability is good (○). Was clearly dissolved and the aluminum substrate exposed was judged to have poor cleaning durability (x).

(Color tone)
The coating film surface was judged to be good (◯) when the surface of the coating film had a uniform black color, and the aluminum plate serving as the base material was completely concealed. The evaluation of the color tone is made in the state of the plate before the drawing (described as “plate” in Table 1) and the final molded product after the drawing (in Table 1, “ This was performed for “after molding”.

(Dry film thickness)
The dry film thickness was measured with an isoscope.

  Table 1 shows the components of the paint for precoat film and the performance of the precoat film evaluated as described above.

  As shown in Table 1, the test material No. No. 1 is a comparative example that does not contain carbon black and copper compound, which are essential components in the precoat film. Specimen No. No. 1 resulted in the infrared emissivity of the film not meeting the criteria of the present invention. In addition, specimen No. The color tone of 1 was colorless, and a good black appearance as the object of the present invention was not obtained.

  Specimen No. 2 is a comparative example in which the amount of carbon black added is less than the range of the present invention. Specimen No. 2 resulted in the infrared emissivity of the film not meeting the criteria of the present invention. In addition, specimen No. The color tone of No. 2 was a reddish black color tone, and a good black appearance intended by the present invention was not obtained.

  Specimen No. 3 is a comparative example in which the dry film thickness (film thickness) is less than the range of the present invention. Specimen No. No. 3 resulted in the infrared emissivity of the film not meeting the criteria of the present invention. In addition, specimen No. The color tone of 3 was a reddish black color tone, and a good black appearance as the object of the present invention was not obtained.

  Specimen No. 4 is a comparative example which does not contain the copper compound which is an essential component in the precoat film. Specimen No. No. 4 resulted in the infrared emissivity of the film not meeting the criteria of the present invention. Moreover, the color tone was a reddish black color tone, and the good black appearance aimed at by the present invention was not obtained.

  Specimen No. 7 is a comparative example which does not contain a copper compound. Specimen No. In No. 7, the color tone after molding became reddish black, and a good black appearance as the object of the present invention was not obtained.

  Specimen No. 11 is a comparative example in which the dry film thickness (film thickness) is larger than the range of the present invention. Specimen No. No. 11 resulted in inferior moldability because the film was peeled off when drawing.

  Specimen No. No. 12 is a comparative example in which the amount of carbon black added is larger than the range of the present invention and does not contain a copper compound. Specimen No. No. 12, although a good black appearance was obtained, the film was peeled off during drawing, resulting in poor moldability.

  Specimen No. 13 is a comparative example in which the amount of carbon black added is greater than the range of the present invention. Specimen No. No. 13 resulted in inferior moldability because the film was peeled off during drawing.

  Specimen No. 14 is a comparative example in which the gel fraction of the precoat film is lower than the range of the present invention. Specimen No. No. 14, as a result of the rubbing test, the film was discolored. That is, the test material No. No. 14 had poor cleaning durability.

  Specimen No. 15 is a comparative example in which the gel fraction of the precoat film is higher than the range of the present invention. Specimen No. No. 15 resulted in inferior moldability because the film was peeled off when drawing.

  Specimen No. 16 is a comparative example in which the glass transition temperature of the base resin of the precoat film is lower than the range of the present invention. Specimen No. No. 16 was scratched in both drawability and cleaning durability.

  Specimen No. 19 is a comparative example in which the glass transition temperature of the base resin of the precoat film is higher than the range of the present invention. Specimen No. No. 19 resulted in inferior moldability because the film was peeled off when drawing.

  Specimen No. 20 and 21 are comparative examples in which the type of base resin and the type of curing agent in the precoat film do not satisfy the present invention. Specimen No. Nos. 20 and 21 resulted in inferior moldability because the film was peeled off when drawing.

  Specimen No. 22 is a comparative example in which the type of curing agent for the precoat film does not satisfy the present invention. Specimen No. In No. 22, as a result of carrying out a rubbing test, the film was discolored. That is, the test material No. No. 22 had poor cleaning durability.

  Specimen No. No. 23 is a comparative example in which alkali degreasing and phosphoric acid chromate treatment were not performed as the base treatment. Specimen No. No. 23 was inferior in moldability because the film was peeled off when drawing.

  Specimen No. other than the above 5, 6, 8 to 10, 17, and 18 are examples that satisfy the present invention, and good results were obtained in all results.

[Second Example]
A temperature rise curve on a flat plate was created for four types of specimens with different infrared emissivities, assuming a lower temperature and shorter time of the soldering process.
The test material used for the experiment was No. 1 in the first example. 1 (emissivity ε = 0.35), No. 1 4 (emissivity ε = 0.66), no. 10 (emissivity ε = 0.88), no. 12 (emissivity ε = 0.88). Specimen No. 10 and test material No. No. 12 has the same value as the infrared emissivity at a wavelength of 3 to 3 μm, but the presence or absence of copper phthalocyanine is different. Therefore, it carried out in order to confirm the effect of the near infrared region of copper phthalocyanine.
The experiment was performed by attaching a thermocouple to a 100 mm × 200 mm flat specimen and measuring a temperature rise curve up to 1 minute after being placed in an infrared oven at 250 ° C. The measurement results are shown in FIG.

  As shown in FIG. 3, it can be confirmed that the higher the emissivity of the test material, the higher the temperature rise curve is, and the easier it is to heat. In addition, the test material No. having the same emissivity. 10 and test material No. In comparison with test sample No. 12, test material No. having copper phthalocyanine was used. No. 10 is the specimen no. Although it showed a tendency to be slightly heated rather than 12, it was suggested that heat absorption is effective in the near infrared region. Therefore, it was suggested that the capacitor formed by using the precoated aluminum plate according to the present invention has a rapid increase in temperature and may improve solderability.

  The precoated aluminum plate according to the present invention has been described in detail with reference to the best mode and examples, but the gist of the present invention is not limited to the above-described contents, and the scope of the right is claimed. Must be interpreted based on the description. Needless to say, the contents of the present invention can be modified and changed based on the above description.

1 Pre-coated aluminum plate for capacitor case (pre-coated aluminum plate)
2 Aluminum plate 3 Precoat film (film)
4 Phosphoric acid chromate film 5 Carbon black 6 Copper compound 7 Cross-linked polyester resin

Claims (2)

A pre-coated aluminum plate for a capacitor case comprising an aluminum plate and a film formed on one side of the aluminum plate,
The surface of the aluminum plate is previously degreased with an alkaline degreasing solution and then subjected to phosphoric acid chromate treatment,
The film includes a crosslinked polyester resin obtained by crosslinking a polyester resin having a glass transition temperature of 20 to 60 ° C. with a melamine curing agent, carbon black, and a copper phthalocyanine compound, and the carbon included in the film The black content is 3% by mass or more and 18% by mass or less, the integral emissivity of infrared rays having a wavelength of 3 to 30 μm is 0.7 or more at a temperature of 25 ° C., and the thickness of the film is 3 μm or more and 12 μm or less. A pre-coated aluminum plate for a capacitor case, wherein the gel fraction satisfies 70% to 95%. 2. The precoated aluminum plate for a capacitor case according to claim 1, wherein the content of the copper phthalocyanine compound contained in the film is 0.1% by mass or more and 1.6% by mass or less.

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