TWI544110B - Precoated aluminum plates for capacitor housings - Google Patents

Description

Precoated aluminum plate for capacitor housing

The present invention relates to a precoated aluminum sheet used for forming a capacitor case of an aluminum electrolytic capacitor or the like.

Aluminum has been used in various applications because of its various advantages such as small specific gravity and good thermal conductivity. Since this aluminum is excellent in corrosion resistance in a natural environment, surface treatment for preventing corrosion is less likely to occur, but in recent years, surface treatment for the purpose of imparting functions has been increasing.

For example, in applications requiring light weight such as notebook computers, thin televisions, and car stereos, pre-coated aluminum sheets using an aluminum plate as a raw material and having a functional film (pre-coated film) on the aluminum plate have been added. When the precoated aluminum sheet is used, it is advantageous in productivity or cost compared with the coating method after performing individual surface treatment after press-forming an aluminum sheet which has not been subjected to surface treatment in advance.

The cover of a thin-disc drive device mounted on a notebook computer is one of the representative uses of pre-coated aluminum. Pre-coated aluminum used in this application requires (1) Lubricity (to reduce the manufacturing cost in order to omit the step of washing the pressurized oil, and to focus on the quick-drying pressurized oil that does not require washing) (continued molding), (2) scratch resistance, fingerprint resistance (focus on improving appearance quality), (3) conductivity (focus on ensuring antistatic property or grounding).

An example of a precoated aluminum sheet that satisfies such requirements is known as, for example, the technique described in Patent Document 1. Patent Document 1 discloses that a specific corrosion-resistant film and a specific resin film are formed on at least one surface of an aluminum plate having a specific arithmetic mean roughness Ra, and conductivity is improved by specifying a surface resistance value thereof, and other contents are also satisfied. Aluminum plates for electronic machines that require performance.

However, the frame (cover or the like) of the electronic device for the live use of the optical disk drive device and the like which are estimated in the patent document 1 is applied to a case where the aluminum plate is bent at 90 degrees to form a box shape. A technique of forming a box-shaped frame by bending is used to establish a technique in which a coil-shaped plate is used, and a continuous forming method using a feed mold is used, and productivity is high. Further, since the technique of forming a box-shaped frame by bending is also known to have a continuous forming technique using quick-drying pressurized oil, it is also advantageous in terms of production cost without requiring a washing step after press forming. Therefore, the technique of forming a box-shaped frame by bending is an excellent method.

However, on the other hand, there is a gap in the corner of the side wall portion of the frame made by the bending process. Therefore, in applications in which a liquid material such as an electrolytic solution is fed into the inside of an outer casing such as an electrolytic capacitor, liquid leakage from a gap existing in a corner of the side wall portion cannot be prevented.

The shape of the container, such as a capacitor case, which does not allow liquid leakage, is not a box shape bent by bending, and must be a container shape obtained by deep drawing. Moreover, when the container-shaped product is pre-coated with aluminum, it is more than the original The aluminum sheet of the material is also required to have a large deformation following the deep drawing process than the pre-coated film.

For example, Patent Document 2 discloses a pre-coated aluminum sheet which is presumed to be deformable with a deep coating process. The precoated aluminum plate is in the intermolecular cross-linked state of the thermosetting resin formed on the surface of the aluminum plate, and the coagulation rate after the heat treatment is compared before and after the heat treatment at 220° C. The value of the gel fraction is continuously decreased from the value of the gel fraction before the heat treatment. Further, by controlling the precoated aluminum plate to a temperature of 220 ° C for 10 minutes, the value of the gel fraction before the heat treatment is less than 10%, and the depth is satisfied. Pulling processability.

As a technique other than the pre-coated aluminum plate listed above, a film laminated aluminum plate obtained by laminating a thermoplastic resin film excellent in workability is used in the case of the outer casing of the electrolytic capacitor. Since the film laminated aluminum plate is not crosslinked by the molecules of the resin constituting the film, the film can be largely deformed, and has characteristics favorable for deep drawing processing.

For example, Patent Document 3 discloses that 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 can be used to prevent resin coating while maintaining moldability. The outer casing of the electronic component in which the film is discolored is coated with a laminated aluminum plate. Further, Patent Document 3 describes a use of a polyamide resin such as nylon or a saturated polyester resin such as PET as a thermoplastic resin film.

Further, for example, Patent Document 4 discloses that a chemical conversion film is provided on an aluminum alloy plate, and a capacitor case is provided with a resin layer coated with an aluminum alloy plate. In the resin-coated aluminum alloy sheet for a capacitor case, the resin in the aluminum alloy sheet is mainly composed of an epoxy resin as a main component, and is added by a group of phenol, acrylic, urethane, or urea. At least one or two or more types are formed. Further, Patent Document 4 describes that the number average molecular weight of the resin is from 5,000 to 30,000, and the lubricant is contained in an amount of from 0.1 to 10 parts by weight based on 100 parts by weight of the resin, and the tensile strength of the resin layer is 40 N/mm ² or more. The elongation is 2% or more, the thickness is 3 to 30 μm, and the checkerboard residual ratio of the checkerboard test when the resin-coated aluminum alloy sheet is rolled to 40% of the reduction ratio is 60% or more.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4237975

[Patent Document 2] Japanese Patent No. 4783051

[Patent Document 3] Japanese Patent No. 4003915

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2006-334917

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

The invention described in Patent Document 1 is intended to be an invention in which a disc drive is used. Therefore, as described above, it is considered that the frame system of the bending process is premised. According to this, the invention described in Patent Document 1 is applied. In the case of a capacitor case, the film does not follow deformation for a shape having a large deformation amount such as deep drawing, and it is considered that film breakage or peeling may occur. Further, in the invention described in Patent Document 1, since the film thickness is extremely thin, it is needless to say that it is a black appearance predetermined by the present invention, and all the coloring is difficult.

The invention described in Patent Document 2 is intended to be a deep drawing processor and is also intended to be applied to a capacitor case. However, the low temperature or short time of soldering which is technically required is not considered, and additional energy is required to make the load on the environment high. Further, the review of the coloring or pigment addition which is intended to be dominated by the black appearance of the present invention is not described.

As described in Patent Document 3, a film made of a thermoplastic resin as a base resin is produced, and since the film laminate which is laminated on the surface of the aluminum plate is a thermoplastic resin film, there is a limit in heat resistance. For example, when a polyamide resin represented by nylon is used as the base resin, the adhesion to the aluminum plate is good, and excellent formability is obtained. However, in a high temperature environment, heat is easily caused in a short period of time. The problem that the base resin turns yellow or brown. Further, when a thermoplastic resin such as PET is used as the base resin, the adhesion to the aluminum plate is good, and the moldability is excellent, and the base resin is not easily thermally discolored even in a high temperature environment. Since the base resin is easily hydrolyzed, the durability in a high-temperature wet environment tends to be deteriorated. Moreover, the low temperature or short time of welding at a low temperature as predetermined by the present invention is not considered.

Further, Patent Document 3 also discloses an example in which a polyolefin resin represented by polyethylene or polypropylene is used as a film laminate of a base resin. However, in the case of the above configuration, the base resin is basically composed of carbon and hydrogen, and does not contain nitrogen. Or oxygen. Accordingly, there is no starting point of a functional group or a chemical bond such as a hydroxyl group, a carboxyl group, an ester bond, an isocyanate group, a urethane bond, an amine group or a guanamine bond, and the adhesion to an aluminum plate is deteriorated.

The invention described in Patent Document 4 is an application of a pre-coated aluminum material with a thermosetting resin having an epoxy resin as a base, and is intended to be applied to a capacitor case. In general, an epoxy resin is characterized in that it has excellent heat resistance as a resin, but is essentially a hard resin, so that a limit is naturally generated when the deep drawability is further improved. Further, Patent Document 4 does not review the review regarding the coloring or pigment addition which is intended to be dominated by the black appearance of the present invention.

Further, if the pre-coated aluminum sheet is formed by slow molding, it may not need to be washed after molding, but it is necessary to use pressurized oil in deep drawing or the like where the molding conditions are severe. When pressurized oil is used, it is necessary to wash the precoated aluminum plate with a detergent such as trichloroethylene after deep drawing. Therefore, pre-coated aluminum sheets subjected to deep drawing are required to have excellent cleaning durability.

The present invention has been made in view of the above problems, and has been proposed to provide a precoated aluminum sheet for molding a capacitor case such as an aluminum electrolytic capacitor, and of course, has excellent deep drawability or cleaning durability required for the application. And having the following features not considered in the prior art for this use, that is, in the soldering step, since the capacitor is easily heated, the soldering step can be lowered or shortened, and the capacitor case having an excellent black appearance can be used. Coated aluminum plate

The precoated aluminum plate for a capacitor case of the present invention comprises a precoated aluminum plate for a capacitor case formed of an aluminum plate and a film formed on one side of the aluminum plate, wherein the surface of the aluminum plate is degreased in advance with an alkaline degreasing liquid. And the phosphoric acid chromate treatment is carried out, and the 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-based curing agent, and carbon black and a copper compound. The content of the carbon black contained in the film is 3% by mass or more and 18% by mass or less, and the integrated radiance 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. Further, when the thickness is 12 μm or less, the gel fraction is satisfied to be 70% or more and 95% or less.

According to this configuration, the precoated aluminum plate for the capacitor case of the present invention is subjected to degreasing treatment with an alkaline degreasing liquid in advance, and then subjected to a chromate treatment, so that the film provided on one side of the aluminum plate contains melamine. The curing agent is a crosslinked polyester resin obtained by crosslinking a polyester resin having a specific glass transition temperature, and has a gel fraction which satisfies a specific range, so that it has excellent moldability and washing durability. Further, carbon black and a copper compound are added to the film at a specific ratio. However, by controlling the ratio, the film thickness of the above range is excellent, and the appearance is black, and the formability or the seaming property are not lowered. Further, since the film has an integrated radiance of 70% (0.7) or more in ensuring infrared rays, heat can be efficiently absorbed during soldering, and it is difficult to increase the temperature of the capacitor, and it is presumed that the solderability can be greatly improved.

In the precoated aluminum plate for a capacitor case of the present invention, the copper compound is preferably a copper phthalocyanine compound. According to this configuration, the black appearance of the precoated aluminum sheet for a capacitor of the present invention can be further improved.

In the precoated aluminum sheet for a capacitor case of the present invention, the content of the copper compound contained in the film is preferably 0.1% by mass or more and 1.6% by mass or less. According to this configuration, the black appearance of the precoated aluminum sheet for the capacitor case of the present invention is excellent, and the content of carbon black can be reduced, so that the economical efficiency of the film can be improved.

Since the precoated aluminum plate for a capacitor case of the present invention has the above configuration, it has an excellent black appearance and an infrared integrated radiance. Therefore, by using the precoated aluminum plate for the capacitor case of the present invention, the solderability can be excellent, and the soldering step can be lowered or shortened, and a capacitor having an excellent black appearance and its outer casing can be obtained. Further, since the precoated aluminum sheet for a capacitor case of the present invention has the above configuration, it has excellent moldability and cleaning durability.

1‧‧‧Pre-coated aluminum sheets for capacitor housings (pre-coated aluminum sheets)

2‧‧‧Aluminum plate

3‧‧‧Pre-coated film (film)

4‧‧‧chromate chromate film

5‧‧‧ carbon black

6‧‧‧ copper compounds

7‧‧• Crosslinked polyester resin

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial cross-sectional view schematically showing an embodiment of a precoated aluminum sheet for a capacitor case of the present invention.

Fig. 2 is a schematic view showing the preparation of a bottomed cylindrical container by deep drawing and ironing processing of the test material.

Fig. 3 is a graph showing temperature rise curves of the test materials No. 1, 4, 10, and 12.

[Pre-coated aluminum plate for capacitor housing]

Hereinafter, a form (embodiment) of a precoated aluminum plate for a capacitor case according to the present invention will be specifically described with reference to an appropriate drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view schematically showing an embodiment of a precoated aluminum sheet for a capacitor case of the present invention.

As shown in FIG. 1, a precoated aluminum sheet 1 (hereinafter also referred to simply as "precoated aluminum sheet 1") for a capacitor case is provided with an aluminum plate 2 and a precoat film 3 formed on one side of the aluminum plate 2. Further, a chromate film 4 is formed between the aluminum plate 2 and the precoat film 3. Moreover, although the phosphoric acid chromate film 4 is formed on the other side of the precoated aluminum sheet 1 shown in FIG. 1, the pre-coating film is formed on the other side of the pre-coated film. Membrane. The respective configurations 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 in order to form a deep-drawn outer casing, a non-heat-treated aluminum plate can be preferably used, and a 1000-series industrial pure aluminum plate, The 3000 series Al-Mn alloy plate can be preferably used. In particular, aluminum sheets such as A1070, A1050, A1100, A3003, A3004, and A3104 specified in JIS H 4000:2006 are recommended. Regarding tempering and thickness, various types can be selected depending on the purpose.

<Precoat film>

The precoat film 3 is a crosslinked polyester resin 7 containing a polyester resin having a glass transition temperature of 20 to 60 ° C by a melamine-based curing agent, and dispersed in the crosslinked polyester resin 7 The carbon black 5 is composed of a resin film of the copper compound 6. The integral emissivity of the infrared rays having a wavelength of 3 to 30 μm in the precoat film 3 is 0.7 or more at a temperature of 25 ° C, the film thickness is 3 μm or more and 12 μm or less, and the gel fraction is satisfied to be 70% or more and 95% or less.

[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 intermolecular crosslinking reaction using a melamine-based curing agent.

As for the intermolecular crosslinks which are not subjected to the thermosetting reaction, there is also a film laminate using a thermoplastic resin as the base resin, but as described in the foregoing prior art, the thermoplastic resin is used as the base resin in various aspects. The problem. However, when the crosslinked polyester resin 7 is selected to be a resin which is intermolecularly crosslinked by a thermosetting reaction or the like, the resin has an excellent adhesion to the aluminum plate 2 since it has a functional group for intermolecular crosslinking. . Moreover, by cross-linking, the washing durability or the chemical resistance can be improved, and the hydrolysis resistance can be improved.

In addition, as a resin for aluminum plate coating, in addition to polyester resin, epoxy resin or vinylidene fluoride resin, acrylic resin, and polycondensation Although ester-based resins and the like are also widely known, it is not appropriate for the present invention to comprehensively consider moldability, cost, and the like.

As the polyester resin, a saturated polyester resin obtained by condensation polymerization of a polyol and a polybasic acid is preferably used.

Among them, as the polyol, for example, a glycol such as ethylene glycol, propylene glycol, neopentyl glycol, 1,3-butylene glycol, 1,6-hexanediol or diethylene glycol, or glycerol or trishydroxyl can be used. A trihydric alcohol such as methylethane or trimethylolpropane, or a quaternary or higher alcohol can be used.

Further, as the polybasic acid, for example, a dibasic acid such as phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid or sebacic acid, or a tribasic acid such as trimellitic anhydride can be used, and a divalent or higher divalent compound can be used. acid.

These polyols and polybasic acids may be used singly or in combination of two or more kinds. Further, by combining the components, the glass transition temperature of the polyester resin can be adjusted.

The glass transition temperature is one of the transfer temperatures of the resin. Generally, the resin at a temperature equal to or higher than the glass transition temperature is in the form of a soft rubber, and the resin at a temperature below the glass transition temperature becomes a hard glass. Accordingly, in order to cause the precoat film 3 to follow during processing in which the deformation of the deep drawing process or the ironing process is large, it is theoretically necessary to lower the glass transition temperature below the processing temperature. However, in reality, the molecular weight of the polymer material is broad, and a branched structure is generated in the molecule, and the primary structure is not uniform, and the macroscopic observation such as the arrangement of the molecules or the high-order structure is not uniform. Accordingly, the glass transition temperature is only a representative value, and a slow transition occurs in a temperature range having a certain degree of amplitude. In addition, the polyester resin is even a glass below the glass transition temperature. In addition to a part of the state (a state in which crystallization is promoted in the state of the thermoplastic resin without crosslinking reaction), since it has a high elongation, it is high even if it is in a certain range. The glass transition temperature of the resin can still be formed as the crosslinked polyester resin 7. On the other hand, when the resin having a low glass transition temperature is used as the crosslinked polyester resin 7, the precoat film 3 becomes excessively soft and tends to be generated.

Accordingly, in the present invention, it is necessary to set the glass transition temperature of the crosslinked polyester resin 7 contained in the precoat film 3 to a 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 excessively soft and is liable to cause enthalpy. On the other hand, when the glass transition temperature of the crosslinked polyester resin 7 exceeds 60 ° C, the formability of the precoated aluminum sheet 1 is lowered, and the film is easily peeled off when the outer shell is molded. Further, the glass transition temperature of the crosslinked polyester resin 7 is preferably, for example, 30 to 45 °C. Here, the term "glass transition temperature" means a measurement by a differential scanning calorimetry (DSC) method.

Further, the crosslinking reaction cannot be caused only by the aforementioned polyester resin. In order to cause the crosslinking reaction required by the present invention, it is necessary to add a curing agent capable of reacting with a carboxyl group of the polyester resin, or to form a component which can exert the same function as the curing agent by the polyester resin itself, and to utilize a chemical reaction. Modification of polyester resin. The functional group reactive with a hydroxyl group or a carboxyl group may be an isocyanate group, an amine group, a hydroxyl group or the like, and a crosslinking agent may be easily promoted by adding a substance having three or more such functional groups as a curing agent. Such a hardener is exemplified by a polyisocyanate compound, a melamine compound, an epoxy compound, an amine compound, a phenol compound, a urea compound, etc., but is based on washing resistance. From the viewpoint of long-termness, the melamine-based hardener in the present invention is necessary.

[carbon black]

The carbon black 5 can be contained in the crosslinked polyester resin 7 of the precoat film 3, and it is ensured that the infrared integrated radiance of the precoat film 3 at a wavelength of 3 to 30 μm is 0.7 or more at a temperature of 25 °C. Further, since the crosslinked polyester resin 7 of the precoat film 3 contains carbon black 5, a black appearance can be imparted.

The type, the size, the form, and the like of the carbon black 5 can be variously changed without any particular limitation as long as the infrared radiance of the infrared ray having a wavelength of 3 to 30 μm is 0.7 or more at a temperature of 25 ° C.

When the ratio of the content of the carbon black 5 to the precoat film 3 is less than 3% by mass, the film thickness becomes 0.7 or more at a temperature of 25 ° C in order to satisfy the infrared radiance of 3 to 30 μm. Too thick, so the formability is lowered. Further, when the content of the carbon black 5 is less than 3% by mass, the color tone of the pre-coated film 3 becomes red-black, and a good black appearance cannot be obtained. On the other hand, when the content of the carbon black 5 is more than 18% by mass, the precoat film 3 itself becomes brittle and is easily peeled off from the aluminum plate 2, and the moldability is still low. Therefore, the content of the carbon black 5 in the precoat film 3 must be 3% by mass or more and 18% by mass or less. Further, the content of the carbon black 5 is preferably 6% by mass or more and 11% by mass or less.

[copper compound]

Copper compound 6 is used to ensure a good black appearance of the precoat film 3. It is contained in the crosslinked polyester resin 7 of the precoat film 3. When the copper compound is not contained, when the deep drawing is performed, or when the thickness of the film is thinned, and when the amount of carbon black added is small, the color tone may turn red and black, and the appearance may be lowered. This decrease in appearance can be improved by the inclusion of a copper compound.

The copper compound which can produce such an effect is, for example, CuO or CaO‧CuO‧4SiO ₂ , CuCr ₂ O ₄ , CuMn ₂ O ₄ or the like, but is excellent in dispersibility or appearance improvement effect in the precoat film 3 . The cyanine compound is preferred. Further, since copper phthalocyanine still has an absorption peak in a near-infrared region having a wavelength of 1000 nm or less, when the infrared radiance of 3 to 30 μm described in the present invention is the same, the addition of copper phthalocyanine has an increase in heat absorption. The complement of sex is better.

When the content of the copper compound exceeds 0% by mass, that is, even if it is contained in the precoat film 3 even if it is only a little, the effect of improving the appearance can be obtained according to the added amount. In addition, 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 0.2% by mass or more, from the viewpoint of more effective appearance improvement effect and economy. 1.4% by mass or less.

[film thickness]

The film thickness of the precoat film 3 is set to 3 μm or more and 12 μm or less. When the film thickness of the precoat film 3 is less than 3 μm, the integrated radiance of the infrared ray of the precoat film 3 and the infrared ray having 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 also becomes brittle and is easily peeled off during molding. The shape is worse. Further, the film thickness of the precoat film 3 can be controlled by adjusting the coating amount of the precoat film coating.

[Gel fraction of pre-coated film]

In the present invention, the gel fraction of the precoat film 3 is set to 70% or more and 95% or less. Since the gel fraction is a parameter of the crosslinking reactivity standard of the thermosetting resin film, the gel fraction of the original crosslinked polyester resin 7 alone should be discussed, but the cross-linked polycondensation of the pre-coated film 3 In addition to the ester resin 7, carbon black 5 and copper compound 6 are contained as essential components, so that it is difficult to strictly measure the gel fraction of only the crosslinked polyester resin 4 (base resin). Accordingly, in the present invention, the gel fraction of the precoat film 3 is replaced, and the gel fraction is specified.

When the gel fraction of the precoat film 3 is 70% or more, the crosslinked polyester resin 7 which forms the precoat film 3 has a high crosslinking density and can be used in an environment other than the washing durability. The precoat film 3 which is excellent in chemical resistance, heat resistance, and hydrolysis resistance is required. On the other hand, the upper limit of the gel fraction is set to 95%, and must not exceed this. When the gel fraction exceeds 95%, the film becomes too hard. Therefore, when it is formed into an outer shape of an elongated cylindrical shape, it is easily peeled off, and the formability is deteriorated. When the gel fraction is 70% or more and 95% or less, the sintering temperature at the time of sintering the coating film is preferably about 200 to 280 ° C, for example.

Further, the method for measuring the gel fraction can be carried out in accordance with the method of JIS K 6796:1998 (except that the extraction solvent is non-xylene, and 2-butanone is used). That is, the test material of the precoated aluminum plate 1 is immersed in boiling The mass change of the precoated aluminum sheet 1 before and after the immersion was measured for 60 minutes in 2-butanone (MEK). Subsequently, the mass of the aluminum plate 2 in which only the precoat film 3 was completely dissolved was measured, whereby the mass change of only the precoat film 3 was calculated, and the ratio was calculated by assuming that the component which was not dissolved in the MEK had been crosslinked. As a gel fraction.

[Integrated emissivity of pre-coated film]

The precoat film 3 of the present invention has an integral radiance of infrared rays having a wavelength of 3 to 30 μm as a temperature of 25 ° C of 0.7 or more. Emissivity is the ratio of the infrared radiant energy from the surface of an object divided by the infrared radiant energy from the surface of the black body to define the light of a particular wavelength at a particular temperature. The value that can be obtained ranges from 0 (white body) to 1 (black body), and the larger the number, the larger the infrared radiation energy. Integrate it into a certain wavelength region to integrate the radiance. According to the radiant type of Planck, in the temperature range (use temperature range) of the precoated aluminum sheet 1 of the present invention, that is, near room temperature, more specifically in the practical temperature range of 273 to 373 K (0 to 100 ° C) The infrared wavelength that occurs is concentrated in the wavelength region of 3 to 30 μm. In other words, infrared rays that deviate from the wavelength region of the wavelength region range can also be ignored. For this reason, in the present invention, infrared rays are limited to a wavelength region of 3 to 30 μm at 25 °C.

The low temperature or short time of the soldering step caused by the temperature rise of the capacitor in the soldering step to be realized by the precoated aluminum sheet 1 of the present invention is achieved by effectively absorbing heat from the surface of the outer casing. Therefore, the arsenal should not be discussed at the rate of emissivity, but if it is based on the rate of absorption, but according to Kirchhoff Law, the absorption rate and emissivity are equivalent in the thermal equilibrium state, so the absorption rate can be directly used instead of the emissivity. Since the temperature rise of the capacitor due to heat in the soldering process is not a state of thermal equilibrium but a phenomenon of non-equilibrium, the above description is strictly not correct, but the emissivity can be confirmed as shown in the examples and comparative examples described later. In the case where the higher case is lower, the solid temperature can be brought to a higher temperature by heating in a shorter time (refer to Fig. 3, and further, Fig. 3 is described later). That is, it is confirmed that the infrared radiance of the above-described conditions of the present invention is 0.7 or more.

Regarding the precoat film 3, if the integrated radiance of infrared rays having 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 is lowered, so that the time or temperature at which the capacitor is heated during soldering is insufficient. Further, the integral radiance of the infrared ray in the present invention is preferably, for example, 0.75 or more, more preferably 0.8 or more. When the integral radiance of the infrared ray having a wavelength of 3 to 30 μm is to be 0.7 or more, the specific amount of carbon black may be added, and the specific amount of the copper compound may be added.

The measurement of the integrated radiance of the infrared rays of the precoat film 3 can be measured, for example, by a commercially available simple emissivity meter (D&S Model AE, manufactured by D and S Co., Ltd.). The measurement range of the simple emissivity meter is 3 to 30 μm, so that the displayed number can be used as the integrated radiance as defined in the present invention.

[other]

The precoat film 3 may contain an additive which imparts various functions without departing from the scope of the invention.

For example, in order to further improve the formability, one or two or more kinds of polyethylene wax, carnauba wax, microcrystalline wax, lanolin, Teflon (registered trademark) wax, polyfluorene wax may be contained. , lubricants such as graphite lubricants and molybdenum lubricants. Further, organic fine particles or inorganic fine particles may be added for the purpose of improving the adhesion of the printing ink. Further, an antioxidant, an ultraviolet absorber, an antistatic agent or the like may be contained as long as the effects of the present invention are exerted.

<Base treatment>

In order to improve the adhesion to the precoat film 3, the surface of the aluminum plate 2 is subjected to degreasing treatment with an alkali degreasing liquid in advance, and it is necessary to apply a chromate treatment. As a degreasing agent suitable for the purpose, various degreasers for weak alkaline aluminum such as sodium carbonate, sodium citrate or sodium phosphate are commercially available, and any of these may be used in the present invention. Further, in addition to the alkali salt as an alkali builder, a chelating agent or an active agent for removing oil may be contained. The degreasing ability of the alkali-based agent can be controlled by the main component, concentration, and treatment temperature of the base to be used. However, when the degreasing ability is enhanced, since a large amount of smut is generated, if the subsequent washing is not sufficiently performed, There is also a case where the adhesion between the aluminum plate 2 and the precoat film 3 is lowered. Further, a strong alkali degreasing agent having a pH of more than 12 may be used. However, if the aluminum surface is strongly etched, the removal of the dirt is required. Therefore, after degreasing, it is preferred to carry out acid washing with sulfuric acid or nitric acid.

The aluminum plate 2 which has been subjected to alkali degreasing is subsequently subjected to a chromate treatment. The chromate phosphate treatment is a reaction type formation treatment in which a treatment liquid made of phosphoric acid, hydrofluoric acid or anhydrous chromic acid is sprayed on the surface of the aluminum plate 2 or the aluminum plate 2 is immersed in the treatment liquid. On the other hand, a film containing chromium phosphate (trivalent) as a main component is formed. The thickness of the film thus formed can be measured relatively easily and quantitatively by the conventional fluorescent X-ray method, so that the quality management of the precoated aluminum sheet 1 can be performed without hindering productivity. Further, the amount of adhesion of the substrate-treated film is preferably from 10 to 50 mg/m ² in terms of metal Cr. When 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. Further, when it is more than 50 mg/m ² , when the precoated aluminum sheet 1 is molded, the substrate-treated film itself is liable to be cracked.

[Examples] [First Embodiment]

Next, with respect to the precoated aluminum sheet of the present invention, a comparative example which satisfies the requirements of the present invention and a comparative example which does not satisfy the requirements of the present invention will be specifically described.

When reviewing the precoated aluminum sheet of the present invention, the aluminum sheet used as the raw material was a material having a thickness of 0.3 mm of alloy No. A1100-H24. The base treatment was carried out by alkaline degreasing with a sodium carbonate-based weak alkali degreaser, followed by treatment with a chromate phosphate. However, only the test material of No. 23 (hereinafter, the No. 23 corresponding to the test material is simply referred to as "test material No. 23") is a comparative material which is not subjected to degreasing or substrate treatment without chromate treatment. . The chromate phosphate treatment conditions were 20 mg/m ^{2 in} terms of chromium adhesion. Moreover, the mechanical properties of the aluminum plate used were tensile strength 130 MPa, endurance 120 MPa, and elongation 8%.

Next, the aluminum plate subjected to the substrate treatment (only the aluminum plate not subjected to the substrate treatment by No. 23) was applied to the precoat film in Table 1 by the coating agent of the component described in the paint column by a bar coater. On the surface. Next, the coating material was heated at the temperature described in the sintering temperature in Table 1 to prepare a precoated aluminum sheet as a test material. Further, the sintering temperature is the temperature at which the raw material finally reaches, and the sintering time is set to 40 seconds from the start to the end of the superheating.

Here, in the base resin shown in Table 1, "polyester melamine" is a polyester-based resin in which a melamine-based curing agent is blended, and "polyester isocyanate" is a polyester-based resin in which an isocyanate-based curing agent is blended. "Epoxy urea" is a compound in which a urea-based curing agent is blended in an epoxy resin, and "epoxyphenol" is a compound in which a phenolic curing agent is blended in an epoxy resin. Further, the glass transition temperature shown in the table is the glass transition temperature of each of the foregoing resins.

The necessary physical properties were tested for the test materials prepared as described above. That is, the integral radiance of the infrared ray of the precoated film at a wavelength of 3 to 30 μm at 25 ° C and the gel fraction of the film were measured. Moreover, the measuring method and the measuring apparatus of the integrated radiance are omitted as described above, and the gel fraction is described below.

(Measurement of gel fraction)

The gel fraction was measured using a test material in which 10 cm × 10 cm was cut out from the test material. After the test material was dried at 80 ° C for 60 minutes in advance, the initial mass (a) was measured, and the test material was immersed in boiling MEK for 60 minutes to dissolve the uncrosslinked component. Next, the test material was dried at 150 ° C. Minutes, the MEK remaining in the film was dried, and the mass after extraction (b) was measured. Finally, the film was completely dissolved in fuming nitric acid, and the mass (c) of only the aluminum plate was measured. Here, since (a)-(c) are only about the mass of the precoat film, and (b)-(c) are the quality of the crosslinked film, the gel fraction expressed by the following formula indicates the degree of crosslinking of the film. .

(gel fraction) = ((b) - (c) / (a) - (c)) × 100 (unit%)

Next, the moldability and the durability (washing durability) for the washing step after molding were examined for the test materials.

(deep drawing formability)

Fig. 2 is a schematic view showing the steps of performing deep drawing processing and ironing processing on a test piece to produce a bottomed cylindrical container. Using the procedure shown in Fig. 2, the deep drawability of the test piece was investigated.

First, after the cylindrical billet is pressed, deep drawing is performed. Then, after stretching and drawing, 12mm is obtained. ×15 mmL cylinder stretched molded article (intermediate molded article). Further, the intermediate molded article is ironed so that the thickness reduction rate of the cylindrical side wall portion is 20%, and trimming is performed to a final 10 mm. The shape of a cylindrical container of ×20 mmL was obtained to obtain a final molded article. The film state results of the final molded article obtained at this time were evaluated as the formability in Table 1. Further, as the pressurized oil, an aqueous emulsion wax containing a fatty acid ester and a surfactant as a main component is used. Moreover, the processing was carried out at room temperature (35 ° C).

In the evaluation of the film state, it was judged that the appearance was abnormal (◎), and the appearance was changed, but no peeling of the film was observed. It was judged to be good (○) when the shape was abnormal, and was judged to be bad (×) when the peeling occurred.

(cleaning durability)

A trichloroethylene was used as a detergent to carry out a friction test. That is, gauze was wound around the front end of a 2 lb. tweezers and fixed with a wheel rubber, and after trichloroethylene was immersed therein, it was rubbed back and forth 10 times on the film. Subsequently, the appearance of the film was visually confirmed. When the surface of the film was not abnormal, it was judged that the cleaning durability was excellent (?), discoloration or scratching, but the coating film was not dissolved, and if the aluminum substrate was not exposed, it was judged that the washing durability was good (○), and the coating film was clearly dissolved, and When the aluminum substrate was exposed, it was judged that the washing durability was poor (×).

(tone)

The surface of the coating film had a uniform black color, and the aluminum plate serving as the substrate was judged to be good (○), and the other appearances were judged to be defective (×). In addition, the evaluation of the color tone is performed on the state of the board before the deep drawing (referred to as "plate" in Table 1), and the final molded product after the deep drawing (in Table 1, "after molding") )get on.

(dry film thickness)

The dry film thickness was measured by an isotoscope.

The properties of the components of the precoat film coating or the precoat film evaluated as described above are shown in Table 1.

As shown in Table 1, the test material No. 1 is a comparative example of carbon black and a copper compound which do not contain an essential component in the precoat film. As a result of the test piece No. 1, the infrared radiance of the film did not satisfy the criteria of the present invention. Further, the color tone of the test material No. 1 was colorless, and the good black appearance of the object of the present invention was not obtained.

The amount of the test material No. 2 carbon black added was less than the comparative example of the scope of the present invention. As a result of the test piece No. 2, the infrared radiance of the film did not satisfy the criteria of the present invention. Further, the color of the test piece No. 2 was a reddish black tone, and a good black appearance for the purpose of the present invention was not obtained.

The test material No. 3 was a comparative example in which the dry film thickness (film thickness) was less than the range of the present invention. As a result of the test piece No. 3, the infrared radiance of the film did not satisfy the criteria of the present invention. Further, the color of the test piece No. 3 was a reddish black tone, and a good black appearance for the purpose of the present invention was not obtained.

A comparative example of a copper compound containing no essential component in the precoat film of the test material No. 4 was used. As a result of the test material No. 4, the infrared radiance of the film did not satisfy the criteria of the present invention. Moreover, the hue is a reddish black hue, and a good black appearance for the purpose of the present invention is not obtained.

The test material No. 7 is a comparative example containing no copper compound. As a result of the test piece No. 7, the color tone after the formation became red-black, and the good black appearance of the object of the present invention was not obtained.

The test material No. 11 was a comparative example in which the dry film thickness (film thickness) was more than the range of the present invention. When the test material No. 11 was peeled off during deep drawing, it was a result of poor formability.

The amount of carbon black added to the test material No. 12 is more than that of the present invention. A comparative example containing no copper compound. The test material No. 12 obtained a good black appearance, but peeling of the film at the time of deep drawing was a result of poor formability.

The amount of the test material No. 13-based carbon black added was more than that of the comparative example of the scope of the present invention. The test material No. 13 was a result of poor formability due to peeling of the film during deep drawing.

The gel fraction of the test material No. 14 pre-coated film was lower than that of the comparative example of the present invention. The test piece No. 14 was subjected to a friction test, and the film was discolored. That is, the test material No. 14 was inferior in cleaning durability.

The gel fraction of the sample No. 15 precoated film was higher than that of the comparative example of the present invention. The test material No. 15 was peeled off during deep drawing, and was a result of poor formability.

The glass transition temperature of the base resin of the test material No. 16 pre-coated film was lower than that of the comparative example of the present invention. The test piece No. 16 was cracked in both deep drawing formability and washing durability.

The glass transition temperature of the base resin of the sample No. 19 pre-coated film was higher than that of the comparative example of the present invention. The test material No. 19 was a result of poor formability due to peeling of the film during deep drawing.

The type of the base resin and the type of the hardener of the pre-coated film of the test materials No. 20 and 21 did not satisfy the comparative example of the present invention. The test materials No. 20 and 21 were the result of poor formability due to peeling of the film during deep drawing.

The type of the hardener of the test material No. 22 pre-coated film did not satisfy the comparative example of the present invention. Test No. 22 to carry out the friction test If the film changes color. That is, the test material No. 22 was inferior in cleaning durability.

The test material No. 23 was subjected to alkali degreasing and phosphoric acid chromate treatment as a comparative example of the substrate treatment. The test material No. 23 was a result of poor formability due to peeling of the film during deep drawing.

The test materials No. 5, 6, 8 to 10, 17, and 18 other than the above satisfy the examples of the present invention, and good results were obtained for all the results.

[Second embodiment]

The temperature of the flat plate is increased for a predetermined time, and the temperature rise curve of the flat plate is prepared for four kinds of test materials having different infrared radiances.

The test materials used in the experiment were No. 1 (emissivity ε = 0.35), No. 4 (emissivity ε = 0.66), No. 10 (emissivity ε = 0.88), No. 12 in the first embodiment. (Emission rate ε = 0.88). The infrared radiance of the test material No. 10 and the test material No. 12 having a wavelength of 3 to 3 μm was the same value, and the difference was the presence or absence of copper phthalocyanine. Therefore, it is implemented in order to confirm the effect of the near-infrared region of copper phthalocyanine.

The experiment was carried out by attaching a thermocouple to a flat test piece of 100 mm × 200 mm, putting it into an infrared oven at 250 ° C, and measuring the temperature rise curve up to 1 minute. The measurement results are shown in Fig. 3.

As shown in Fig. 3, the higher the emissivity of the test material, the higher the temperature rise curve rises, and it can be confirmed that it is easily heated. Further, when the test material No. 10 having the same emissivity and the test material No. 12 were compared, the test material No. 10 having copper phthalocyanine showed a tendency to be slightly heated compared with the test material No. 12. The heat absorption effectiveness in the near infrared region is taught. According to this, the teaching makes The temperature of the capacitor formed by the precoated aluminum sheet of the present invention is rapidly increased and the weldability is improved.

The preferred embodiments and examples of the precoated aluminum sheets of the present invention are described in detail above, but the gist of the present invention is not limited to the foregoing, and the scope of the claims should be construed based on the scope of the claims. Further, the content of the present invention can be changed, changed, etc. based on the above description.

1‧‧‧Pre-coated aluminum sheets for capacitor housings (pre-coated aluminum sheets)

2‧‧‧Aluminum plate

3‧‧‧Pre-coated film (film)

4‧‧‧chromate chromate film

5‧‧‧ carbon black

6‧‧‧ copper compounds

7‧‧• Crosslinked polyester resin

Claims (3)

A pre-coated aluminum plate for a capacitor casing, comprising a pre-coated aluminum plate for a capacitor casing formed on an aluminum plate and a film formed on one side of the aluminum plate, wherein the surface of the aluminum plate is degreased in advance with an alkaline degreasing liquid And the phosphoric acid chromate treatment is carried out, and the 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-based curing agent, and carbon black and a copper compound. The content of the carbon black contained in the film is 3% by mass or more and 18% by mass or less, and the integrated radiance 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. Below 12 μm, the gel fraction satisfies 70% or more and 95% or less. The capacitor casing of claim 1 is a precoated aluminum plate, wherein the copper compound is a copper phthalocyanine compound. The precoated aluminum sheet for forming according to claim 1 or 2, wherein the content of the copper compound contained in the film is 0.1% by mass or more and 1.6% by mass or less.