JP2006334917A - Resin-coated aluminum alloy sheet for capacitor case and capacitor case using the sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor case in which a resin is not broken or peeled even when subjected to severe molding such as case processing or caulking processing, characteristics such as bending processability are not spoiled, discoloration by heat treatment in a solder reflow process is prevented. <P>SOLUTION: In a resin-coated aluminum alloy sheet for the capacitor case, the resin contains an epoxy resin as a main component and is incorporated with at least one selected from the group consisting of a phenol resin, an acrylic resin, a urethane resin, and a urea resin, the number average molecular weight of the resin is 5,000-30,000, a lubricant is contained in an amount of 0.1-10 pts.wt. per 100 pts.wt. of the resin, the tensile strength of a resin layer is at least 40 N/mm<SP>2</SP>, the elongation is at least 2%, the thickness is 3-30 μm, and a cross-cut survival rate in a cross-cut test is at least 60% when the resin-coated aluminum alloy sheet is rolled to a draft of 40%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a resin-coated aluminum alloy plate for a capacitor case that has an organic resin film with good adhesion and that provides stable insulation, and a capacitor case using the resin-coated aluminum alloy plate, particularly heat resistance, moldability, Provided is a resin-coated aluminum alloy plate for a capacitor case that is excellent in chemical resistance, temperature and humidity resistance.
The aluminum alloy plate of the present invention includes pure aluminum such as A1100 and A1050.

  In general, when manufacturing a capacitor, a process of producing a bottomed cylindrical case by deep drawing or squeezing an aluminum alloy plate, a lateral groove processing of the case side surface, and a case opening end to seal the inside of the case There is a process of curling. Of these, the lateral groove processing and curling processing are collectively referred to as “caulking”.

  By the way, in order to prevent the outer surface of the case from coming into contact with other electronic components and causing malfunctions, the case is used by being covered with a vinyl chloride cover. However, covering the aluminum case with a PVC cover insulatively impairs productivity, so instead of the aluminum bare material, a laminated material (a patent document 1) in which an aluminum alloy plate and a thermoplastic nylon resin are laminated, aluminum There has been proposed a method of omitting a step of covering a vinyl chloride cover using a coating material (Patent Document 2) in which a thermoplastic polyester resin is coated on an alloy plate.

In recent years, with the miniaturization of electronic components, Al electrolytic capacitors are also becoming smaller. For example, chip-type aluminum electrolytic capacitors that have been miniaturized by eliminating the lead wires for surface mounting (chip-on-board) are practical. However, in such a small aluminum electrolytic capacitor, it is extremely difficult to coat the heat shrinkable tube. Therefore, instead of the aluminum alloy plate, a laminate material in which a thermoplastic nylon resin film is laminated on an aluminum alloy plate, or aluminum A method has been proposed in which the coating of the heat-shrinkable tube is omitted using a coating material (Patent Document 3) obtained by coating a polymer polyester resin on an alloy plate.
Japanese Patent Laid-Open No. 08-1857 JP 09-275043 A JP 2002-319523 A

  Nylon resin-coated laminated aluminum material as shown in Patent Document 1 and thermoplastic polyester resin-coated laminated aluminum material as shown in Patent Document 2 are reduced in the adhesion between the resin film and the aluminum plate during caulking. Pinholes are generated in the resin, and the resin film is finely broken during use (pinhole breakage), resulting in a decrease in insulation. To prevent this, heat treatment is performed after caulking and productivity is poor. Moreover, when left in a high temperature and high humidity atmosphere, there is a problem that the adhesion of the resin film is lowered.

  Although the polyester resins shown in Patent Document 2 and Patent Document 3 have good moldability and can withstand severe molding processes, the resin is hydrolyzed in a high-temperature and high-humidity test (for example, maintained at 80 ° C. and 85% RH for 2000 hours). Therefore, there are problems that discoloration occurs in the appearance and printed characters are shifted.

  Furthermore, any of the materials in Patent Documents 1, 2, and 3 tends to cause a problem that the resin film turns yellow to brown due to the heat treatment in the solder reflow process, and in particular, the heat treatment temperature increases in recent years due to the lead-free solder. There is a problem that the degree of discoloration tends to increase due to the tendency.

  The present invention has been made in view of such a situation, and with respect to the above-described problems, there is no breakage or peeling of the resin even when subjected to severe molding such as case processing or caulking processing, and a metal plate such as bending workability. Resin-coated aluminum alloy plate for capacitor cases with excellent moldability and heat resistance, such as no discoloration due to heat treatment in the solder reflow process, without impairing the properties required for precoat materials, and capacitor cases using this For the purpose of provision.

As a result of intensive studies conducted by the inventors to achieve the above object, it has been found that the following performance is required for use as a capacitor case.
-Mechanical properties of the resin: Tensile strength is 40 N / mm ² or more and elongation is 2% or more.
-Work adhesion: The cross-cut remaining rate in the cross-cut test of the resin-coated aluminum alloy sheet rolled to a rolling reduction of 40% should be 60% or more.
-Heat resistance: No discoloration in appearance after heating at 260 ° C for 90 seconds. Specifically, the color difference ΔE before and after heating is 3 or less.
・ Moldability: No streaking or resin film peeling due to galling when molded into a capacitor case.
・ Chemical resistance: After the capacitor case is immersed in boiling perchlorethylene for 20 minutes, there should be no peeling of the resin film or coating film on the edge of the case.
・ Constant temperature / humidity resistance: The specimen must be kept in a constant temperature / humidity tank maintained at 80 ° C. × 85% RH for 2000 hours, and there should be no discoloration of the coating film or deviation of printed characters.
-Insulation property: The surface resistance value measured by a method according to JISK6911 must be 10 ⁷ Ω or more.

As a material satisfying these performances, the invention according to claim 1 is a resin-coated aluminum alloy plate in which a chemical conversion film is provided on an aluminum alloy plate and a resin layer is provided thereon. And a resin having a number average molecular weight of 5,000 to 30,000, and a lubricant, comprising at least one selected from the group consisting of phenolic, acrylic, urethane, and urea. The resin layer has a tensile strength of 40 N / mm ² or more, an elongation of 2% or more, a thickness of 3 to 30 μm, and a resin-coated aluminum alloy plate. Resin-coated aluminum alloy sheet for capacitor cases, characterized in that the cross-cut remaining rate in the cross-cut test when rolling down to a rolling reduction of 40% is 60% or more That.

  The invention described in claim 2 is a capacitor case obtained by molding the resin-coated aluminum alloy plate.

  The resin-coated aluminum alloy plate of the present invention is excellent in heat resistance, moldability, chemical resistance, constant temperature and humidity resistance, and insulation, and is suitably used for a capacitor case.

  The present invention is described in further detail below.

As the aluminum alloy plate of the present invention, any aluminum alloy plate in addition to pure aluminum plate can be applied.
The shape of the aluminum alloy plate is not particularly limited, such as a coil shape or a cut plate shape, but it is preferable to coat the coil shape in terms of productivity, cost, and uniformity of performance.
There is no particular limitation on the thickness of the aluminum alloy plate.

  When forming a resin layer on an aluminum alloy plate, it is preferable to clean the surface by a degreasing treatment or the like, but it is preferable to further form a base film in order to improve adhesion and corrosion resistance. As the undercoat, a chemical conversion film is generally used, but the type of the conversion film is not particularly limited. For example, chromate (phosphate chromate, chromate chromate), non-chromate (zirconium, titanium, phosphoric acid) Salt-based, oxalate-based, etc.) reaction type and coating type, and from the viewpoints of performance stability, productivity, cost, etc., it is preferably selected from chromate-based, zirconium-based and titanium-based. The chemical film may be formed by a normal method such as a reaction type or a coating type, and there is no particular limitation.

  As the type of the resin, a resin having an epoxy-based component as a main component and at least one or more selected from the group of phenol-based, acrylic-based, urethane-based, and urea-based resins is preferable. As the epoxy type, any glycidyl ether type epoxy resin such as bisphenol A type, bisphenol F type and novolac type can be used. In particular, epoxy-urea resins and epoxy-acrylic resins are more suitable as resins that are resistant to yellowing of the resin film due to heat treatment in the solder reflow process. preferable. In the polyester system, the ester bond is hydrolyzed in a constant temperature and humidity test (for example, maintained in an environment of 80 ° C. and 85% RH for 2000 hours), causing problems such as appearance discoloration and printed characters appearing to be shifted. Further, the heat treatment in the solder reflow process tends to cause yellowing of the resin film. In particular, the heat treatment temperature tends to increase as the solder becomes lead-free, and the degree of yellowing tends to increase. Polyamide resins (nylon 6, nylon 6,6, nylon 6,10, etc.) are prone to yellowing of the resin film due to heat treatment in the solder reflow process, and in particular, the heat treatment temperature tends to increase with the lead-free solder. There is a tendency for the yellowing degree to increase.

  About the molecular weight of the said resin, it is set to 5000-30000 by a number average molecular weight from a viewpoint of the above-mentioned heat-resistant yellowing and the process adhesiveness mentioned later. A higher molecular weight is less likely to cause heat-resistant yellowing because the degree of discoloration due to oxidation during heat treatment is smaller. Moreover, since the number of functional groups increases as the molecular weight increases, the processing adhesion of the coating film is improved. A more preferable range is 10,000 to 20,000. If the molecular weight is less than 5000, the resin is easily broken during molding, yellowing due to the heat treatment in the solder reflow process described above is likely to occur, and the work adhesion described later is further deteriorated. However, if the molecular weight exceeds 30000, the viscosity of the paint may be increased when the resin is diluted with a solvent to form a paint, and the appearance of the paint surface may deteriorate.

Regarding the mechanical properties of the resin layer, the tensile strength is 40 N / mm ² or more and the elongation is 2% or more. If the tensile strength is less than 40 N / mm ² , the resin tends to break during molding. Even if the elongation is less than 2%, the resin breaks during molding.

  The resin layer has a thickness of 3 to 30 μm, and more preferably 4 to 10 μm. If it is less than 3 μm, the resin film may be broken during molding, and the insulating properties are poor. If the thickness exceeds 30 μm, so-called galling occurs where the resin film is partially peeled during the drawing process, and vertical streaks and peeling of the coating film may occur. In addition, the resin film may be broken or peeled during the caulking process.

  As processing adhesion, it is necessary that the coating film residual ratio is 60% or more when a cross cut test is performed after rolling to a rolling reduction of 40%. If it is less than 60%, the coating film adhesion is inferior, so that when the resin case is molded, peeling of the resin film or film peeling occurs at the end of the case.

  For the lubricant, the addition amount is 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin. If it exceeds 10 parts by weight, the solvent resistance is lowered. Examples of the type include polyethylene wax, lanolin wax, carnauba wax, microcrystalline wax, and fluororesin (polytetrafluoroethylene (PTFE), polyvinyl fluoride, etc.), but there is no particular limitation.

  The surface on which the resin layer is provided on the aluminum alloy plate subjected to the base treatment may be single-sided or double-sided depending on the application and required performance, and is not particularly limited.

  About the formation method of a resin layer, you may heat-press the resin film formed beforehand on the aluminum alloy board which gave the base treatment, or heat-melt the resin film and affix it on an aluminum alloy board. Or you may heat-dry after apply | coating the coating material prepared suitably. As a coating method, a roll coater method, a die coater method, an air knife method, a spray method, an electrostatic coating method, or the like can be used, and drying can be performed by a general heating method, dielectric heating method, or the like.

  Moreover, you may add an antifoamer, a leveling agent, and a coloring agent (a pigment, dye, etc.) to a resin layer as needed in the range which does not impair the performance of the resin-coated aluminum alloy plate of this invention.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to a following example, unless the range of a claim is exceeded.

An aluminum alloy plate (A3003, plate thickness 0.3 mm) was degreased with a commercially available alkaline degreasing agent, washed with water, and then subjected to a base treatment to form a phosphate chromate film (chemical name: Alsurf 408/48, Japan) Paint Co., Ltd.). The amount of the undercoat at this time was 20 mg / m ² in terms of metal chromium. Thereafter, a coating material from A-1 to J shown in Table 1 was applied to one side of the aluminum alloy plate with a bar coater and baked and dried to obtain a resin-coated aluminum plate. In addition, the films shown in Table 1, K, L, and M were attached to an aluminum plate that had undergone a base treatment in a heated and melted state. As for the mechanical properties of the resins shown in Table 1, a tensile strength test was conducted by conducting a tensile test with a resin film (free film) having a thickness of 20 μm and a strip shape having a width of 30 mm and a length of 180 mm. Asked.

The following tests were performed on the obtained resin-coated aluminum alloy plate.
(1) Work adhesion After rolling to 40% of the original plate thickness with a rolling mill, a cross-cut test was performed on the coating surface in accordance with JIS K 5600, and the number of remaining cross-cuts was displayed as a percentage. . The cross-cut remaining rate was 60% or more.

(2) Heat resistance The L ^* , a ^* , b ^* values on the surface of the test piece were measured in advance with a multi-light source spectrocolorimeter manufactured by Suga Test Instruments, heated at 260 ° C. for 90 seconds, and then similarly L ^* , a ^* , b ^* Value was measured and ΔE ^* was calculated by the following formula.
ΔE ^* = ((ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ) ^(1/2)
A: ΔE ^* <1
○: ΔE ^* is 1 or more and less than 3 ×: ΔE ^* ≧ 3
Note that ΔE ^* of less than 3 was accepted.

(3) Formability A volatile press oil G-6284M (trade name, manufactured by Nippon Tool Oil) is applied to both sides of the test piece so that the resin-coated surface is on the outside, and the size: φ10 × L13 mm cylindrical shape After press molding into a capacitor case, the state of the coating film was visually observed.
○: No streaking or rupture of coating film (good)
○ △: Slightly streaks are generated (possible)
Δ: Streaks due to galling (no)
×: Streaking due to galling and breakage of coating film (No)
In addition, ○ △ or more was regarded as passing.

(4) Chemical resistance The case formed by the method of (3) above was evaluated by visual observation for the presence or absence of coating film peeling and the presence or absence of edge coating film after immersion for 20 minutes in boiling perchlorethylene.
Appearance coating film state ○: No coating film peeling ×: Coating film peeling end film state ○: No coating film peeling ×: Coating film peeling

(5) Constant temperature and humidity resistance A test piece printed with UV ink and cured by irradiating with ultraviolet rays and cured in a constant temperature and humidity chamber of 80 ° C. x 85% RH for 2000 hours, and then the coating is discolored. The printed character state was evaluated visually.
Appearance ○: No discoloration of coating film ×: Discoloration of coating film Character state ○: No change ×: Character misalignment

(6) Insulation The surface resistance was measured by a method according to JIS K 6911. As an apparatus, a digital ultrahigh resistance / microammeter manufactured by Advantest was used.
○: 10 ⁷ Ω or more ×: Less than 10 ⁷ Ω

The results are shown in Table 2.

  From the above results, it can be seen that the resin-coated aluminum plates of Invention Examples 1 to 26 are excellent in work adhesion, heat resistance, moldability, chemical resistance, constant temperature and humidity resistance, and insulation.

Comparative Examples 1-12.
In Comparative Example 1, since the molecular weight was small, the work adhesion was poor, and streaks due to galling at the time of molding and coating film breakage occurred. Moreover, heat resistance and chemical resistance were inferior.
In Comparative Example 2, since the amount of lubricant was too much, the work adhesion was inferior, and therefore the chemical resistance was inferior.
In Comparative Example 3, since there was no lubricant, streaks due to galling occurred during molding. Moreover, chemical resistance was inferior.
In Comparative Example 4, the resin was an epoxy simple substance and the number average molecular weight was low, so that the work adhesion and heat resistance were poor, and the elongation of the resin layer was low, so the moldability and chemical resistance were poor.
In Comparative Example 5, since a high-molecular polyester resin was used, heat resistance and temperature and humidity resistance were poor, and discoloration and character shift occurred.
In Comparative Example 6, since the resin is acrylic and the number average molecular weight is low, the heat resistance is poor, and since the tensile strength of the resin is low, the moldability and chemical resistance are inferior.
-Since the film thickness of the comparative example 7 was thin, insulation was inferior.
In Comparative Example 8, since the film thickness was thick, streaks due to galling occurred during molding. Moreover, chemical resistance was inferior.
-Since Comparative Example 9 was a polymer polyester film, heat resistance, constant temperature and high humidity resistance were poor, and discoloration and character shift occurred.
-Since Comparative Examples 10 and 11 were nylon films, heat resistance was inferior.
-In Comparative Example 12, since the molecular weight was too large, appearance defects such as coating unevenness and armpit occurred, and it was judged that a uniform coating film could not be obtained, and the performance test was stopped.

Claims (2)

In a resin-coated aluminum alloy plate in which a chemical conversion film is provided on an aluminum alloy plate and a resin layer is provided thereon, the resin is mainly composed of an epoxy-based resin and is selected from the group consisting of phenolic, acrylic, urethane, and urea-based resins. This resin comprises at least one selected from two or more selected, the resin has a number average molecular weight of 5,000 to 30,000, and contains 0.1 to 10 parts by weight of a lubricant with respect to 100 parts by weight of the resin. Cross-layer residual rate in a cross-cut test when the tensile strength of the layer is 40 N / mm ² or more, the elongation is 2% or more, the thickness is 3 to 30 μm, and the resin-coated aluminum alloy sheet is rolled to a reduction ratio of 40% A resin-coated aluminum alloy plate for capacitor cases, characterized in that is 60% or more. A capacitor case obtained by molding the resin-coated aluminum alloy plate according to claim 1.