JP2001257129A - Capacitor case laminating polyester film, laminated aluminium material for capacitor case and capacitor case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminium plate laminating polyester film for molding a capacitor case, which is particularly suitable for a molding of the capacitor case, by a method, where the polyester film is superior in its follow-up properties to a molding of an aluminium plate and moreover, the polyester film is superior in the adhesion of the polyester to the aluminium plate and its corrosion protection properties to the aluminium plate and furthermore, the polyester film holds favorably these advantages even after its heat history. SOLUTION: A capacitor case laminating polyester film is characterized by that the polyester film comprises a copolymer polyester of a melting point of 210 to 245 deg.C, the polyester film is a film of a plane orientation coefficient of 0.10 to 0.16 and stresses in the polyester film at the time of the extension of 100% of the polyester film at 100 deg.C in the MD direction and the TD direction are respectively in the range of 10 to 150 MPa and a laminated aluminium material for the capacitor case and the capacitor case are formed using the polyester film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyester film for bonding a capacitor case, a laminated aluminum material for the capacitor case using the same, and a capacitor case. More specifically, the present invention, in a capacitor case obtained by molding an aluminum plate, improves the ability to follow the deformation of the aluminum plate during molding, the adhesion to the aluminum plate, and the corrosion resistance of the aluminum plate, and The present invention relates to a polyester film for laminating a capacitor case, which retains these improved properties even after a heat history.

[0002]

2. Description of the Related Art Conventionally, a capacitor case has been manufactured by molding an aluminum plate covered with an organic film. The method of providing an organic film on an aluminum plate includes (1) a resin coating baking method such as an epoxy, polyester, vinyl chloride or acrylic resin, (2) a fluorine resin coating baking method, and (3) various resin layers. And a dry lamination method in which the components are bonded with an adhesive. Among them, in the method (3), the material following the resin layer and the adhesive are appropriately selected, so that the molding followability,
Although the adhesiveness and anticorrosion are simultaneously satisfied, the method (1) has poor corrosion resistance of the formed aluminum plate, and the method (2) has adhesion to the aluminum plate. There is a drawback that the film is easily peeled off during molding due to poor properties. Therefore, as a method of providing an organic film on an aluminum plate, the dry lamination method (3) has been preferably used.

As a specific dry lamination method, a laminated aluminum material for a capacitor case in which a polyolefin resin layer or a polyamide film is bonded to an aluminum material with an adhesive containing an aziridine compound (Japanese Patent Laid-Open No. 4-127413). Or a laminated aluminum material for a capacitor case in which a polyamide film, a polyolefin resin layer or a polyester film is bonded to an aluminum material with an adhesive containing an isocyanate compound (JP-A-4-266004). I have.

As the organic film for coating the aluminum plate, there are the above-mentioned polyamide-based film, polyolefin-based resin layer and polyester-based film, but the polyolefin-based resin is significantly deteriorated by heat applied at the time of molding. The film has a drawback of being colored by heating, and the use of a polyester film excellent in heat resistance has been strongly desired.

A method of laminating a polyester film to an aluminum plate by a dry lamination method is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Hei 4-266004. In the embodiment, in particular, a polyethylene terephthalate film having a melting point of 260.degree. Is disclosed. However, recently, due to the miniaturization and complexity of the shape of the capacitor case, it has been required to further follow the forming process, adherence and anticorrosion, and prevent the resin layer from being deteriorated due to heat during mounting and use of the capacitor. Even with the polyester film disclosed in JP-A-4-266004, it has become impossible to sufficiently cope with it.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to improve the followability of forming an aluminum plate, the adhesion to an aluminum plate, and the anticorrosion of an aluminum plate. It is an object of the present invention to provide a polyester film for bonding a capacitor case, which retains the characteristics well after a heat history, a laminated aluminum material for the capacitor case and a capacitor case using the same.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have further improved molding followability, adhesion and anticorrosion properties, and have these properties good even after thermal history. As a result of diligent research to find a polyester film to be retained in the film, the melting point of the polyester, the plane orientation coefficient of the film after forming into a film, and the 100 ° C at 100 ° C.
The inventors have determined that the stress at the time of% elongation has a close effect, and have reached the present invention.

[0008] Thus, according to the present invention, the melting point is 210-
245 ° C is a film having a plane orientation coefficient of 0.10 to 0.16, and has a MD direction and T
The stress at 100% elongation at 100 ° C. in the D direction is
A polyester film for bonding a capacitor case, which is in the range of 10 to 150 MPa, and a laminated aluminum material and a capacitor case for the capacitor case using the same are provided.

In the present invention, the “MD direction” refers to a direction parallel to the film surface and along the film forming direction.
The “TD direction” refers to a direction parallel to the film surface and perpendicular to the film-forming direction, and the plane orientation coefficient refers to a general formula (from the refractive index of each direction component of the film measured by Abbe method) Means calculated by 1).

(Equation 1)

(Wherein P is the plane orientation coefficient, n _MD is the refractive index of the film in the MD direction, n _TD is the refractive index of the film in the TD direction, and n _Z is the refractive index in the thickness direction perpendicular to the film surface. .)

Hereinafter, the present invention will be described in detail. A first feature of the polyester film for bonding a capacitor case of the present invention is that the copolymerized polyester constituting the film has a melting point in the range of 210 to 245 ° C. Those having a melting point of less than 210 ° C. are inferior in heat resistance and, for example, cannot withstand the heat of solder when mounting the substrate of the capacitor. On the other hand, those having a melting point exceeding 245 ° C. are too rigid and inferior in moldability. The preferred range of the melting point of the copolymerized polyester is from 212 to 235 ° C. Examples of the main repeating unit of the copolymerized polyester used in the present invention include ethylene terephthalate, tetramethylene terephthalate, ethylene-2,6-naphthalate, tetramethylene-2,6-naphthalate and the like. Copolymerized polyethylene terephthalate containing an ethylene terephthalate unit as a main component is preferable because it can maintain good molding followability, adhesion, and corrosion resistance even after heat history. Here, the term "containing ethylene terephthalate unit as a main constituent" means that the terephthalic acid component contains at least 75 mol% of all dicarboxylic acid components and the ethylene glycol component contains at least 75 mol% of all diol components.

The copolymerization component of polyethylene terephthalate is not particularly limited as long as the properties of the obtained film do not exceed the scope of the present invention. Preferred dicarboxylic acid components include isophthalic acid, orthophthalic acid,
2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid,
Preferred diols such as aromatic dicarboxylic acid components such as 4'-biphenylenedicarboxylic acid, alicyclic dicarboxylic acid components such as cyclohexane-1,4-dicarboxylic acid, and aliphatic dicarboxylic acid components such as succinic acid, adipic acid and sebacic acid. The components include aliphatic diol components such as propylene glycol, trimethylene glycol and tetramethylene glycol, alicyclic diol components such as cyclohexane-1,4-dimethanol, aromatic diol components such as bisphenol A, diethylene glycol, and polyethylene glycol. , A polycondensed diol component such as polytetramethylene glycol, and a component other than the preferred dicarboxylic acid and diol component, p-
Hydroxycarboxylic acid components such as hydroxybenzoic acid, ω-hydroxybutyric acid, ω-hydroxyvaleric acid, and lactic acid; carbonic acid components such as those found in polycarbonate; and trifunctional or higher functional components such as trimellitic acid, pyromellitic acid and glycerin Is mentioned. Among these, isophthalic acid, 2,2,3
6-Naphthalenedicarboxylic acid or diethylene glycol is particularly preferred. The proportion of these copolymer components may be adjusted so that the melting point of the copolymerized polyester is in the range of 210 to 245 ° C. For example, when isophthalic acid is copolymerized with polyethylene terephthalate, the total dicarboxylic acid component The proportion of isophthalic acid occupying is preferably in the range of approximately 5.5 to 18 mol%.

By the way, the above polyester film is
It is preferable to contain particles having an average particle size of 2.5 μm or less, since an appropriate slip property can be obtained, and as a result, the film is excellent in handleability and moldability. Although the type of the particles is not particularly limited, silica, alumina, titanium oxide, calcium carbonate, inorganic fine particles such as kaolin, precipitated fine particles of catalyst residue and / or silicone, crosslinked polystyrene,
Preferred examples include organic fine particles such as an acrylic crosslinked product. If the average particle size exceeds 2.5 μm, the particles are likely to fall off during the molding process. On the other hand, the lower limit of the average particle diameter is preferably at most 0.01 μm, because if it is too small, handling such as prevention of aggregation of particles becomes difficult. The added amount of such particles is preferably in the range of 0.001 to 40% by weight. If the addition amount exceeds 40% by weight, particles may drop off during molding as in the case of a large grain system.
If the content is less than 001% by weight, it is difficult to improve the slipperiness by adding the particles. Needless to say, the polyester film for bonding the capacitor case of the present invention is, in addition to the above-mentioned particles, various additives such as a stabilizer, an antistatic agent, a dye, a pigment and a flame retardant as long as the effects of the present invention are not impaired. May be contained.

The polyester film for bonding a capacitor case of the present invention has, besides the above-mentioned melting point, a plane orientation coefficient in the range of 0.10 to 0.16 and a 100 ° C. at 100 ° C. in the MD and TD directions. % Elongation stress is in the range of 10 to 150 MPa, respectively.

First, the plane orientation coefficient indicates the orientation of molecular chains in the film. If it exceeds 0.16, the molecular chains are excessively oriented. It is not easily deformed, and the followability to the forming of the aluminum plate is poor. On the other hand, if the plane orientation coefficient is less than 0.10, embrittlement is likely to occur after lapse of time or heat history because the molecular chains are almost non-crystalline with little orientation. The preferred range of the plane orientation coefficient is 0.10 to 0.1.
14.

Next, the elongation at 100 ° C. is a measure of the formability indicating the deformation mode at a typical working temperature. When the stress at 100% elongation in the MD direction or TD direction exceeds 150 MPa, rigidity increases. On the other hand, if it is less than 10 MPa, no excessive stress is applied at the time of deformation, so that it is difficult to uniformly deform.
The preferred range of the stress is 20 to 110 MPa in both the MD and TD directions.

A polyester film having such a plane orientation coefficient and a stress at the time of 100% elongation can be produced by appropriately adjusting a conventionally known film production method, and among them, in the MD and TD directions of the film. In each case, a biaxial stretching method capable of easily changing film properties such as a plane orientation coefficient is preferable. Specifically, pellets of the copolymerized polyester used in the present invention are dried and melted, extruded from a die onto a cooling drum, and cooled to obtain an unstretched film. Then, the unstretched film is moved in the MD direction by 2.0 to
What is necessary is just to stretch sequentially and simultaneously 4.5 times and 2.0 to 5.0 times in TD direction, and to heat-set at 150 to 230 degreeC for 1 to 180 seconds. If the stretching ratio in the MD or TD direction is less than 2.0, the orientation of the molecules is insufficient, and it becomes extremely difficult to obtain the plane orientation coefficient defined in the present invention.
The capacitor case is likely to be inferior in aging embrittlement resistance. On the other hand, when the stretching ratio in the MD direction exceeds 4.5 times or the stretching ratio in the TD direction exceeds 5.0 times, molecules in the film are excessively oriented, and it becomes difficult to obtain the range of the plane orientation coefficient in the present invention, As a result, the moldability of the capacitor case tends to be poor. Further, the heat setting temperature of the film is 150
If the temperature is lower than ℃, the heat shrinkage is large and the misalignment is liable to occur during laminating. On the other hand, if the temperature is higher than 230 ° C, the orientation of the film is loosened, which causes sagging due to its own weight. In addition, in order to reduce heat shrinkage, it is also preferable to appropriately perform a relaxation treatment at the time of heat setting. The thickness of the film is not particularly limited, but is preferably 0.5 to 250 μm.

The method for bonding the polyester film of the present invention to an aluminum plate is not particularly limited.
For example, a conventionally known method such as dry lamination via an adhesive can be used. In this case, in order to further improve the adhesion between the film and the adhesive, an easy-adhesion (primer) layer may be provided on the film, or a corona discharge treatment, a plasma treatment, a flame treatment, or the like may be performed.
In addition, the primer layer may be provided by applying a film in a film forming-stretching-heat fixing step.

The aluminum plate to which the polyester film of the present invention is bonded has high adhesion between the aluminum plate and the polyester film, and maintains the adhesion during the forming process due to the excellent followability of the polyester film of the present invention. Have been. Therefore, defects such as peeling between the aluminum plate and the polyester film are unlikely to occur,
It is also excellent in the corrosion protection of aluminum plates. Moreover, since the film is made of polyester having excellent heat resistance, these advantages can be maintained well even after the heat history, and when used as a capacitor case, a material having excellent insulation properties can be obtained.

[0020]

The present invention will be described in more detail with reference to the following examples. The properties of the obtained polyester film were measured and evaluated by the following methods.

(1) Melting point The obtained polyester film was sampled in an amount of 20 mg, and filled in an aluminum pan.
uPont Instrument 910 DSC), and the temperature was raised from room temperature at a rate of 20 ° C./min. The change in calorific value is recorded against an empty aluminum pan, and the temperature corresponding to the endothermic peak in the hottest part is the melting point (° C).
And

(2) Plane Orientation Coefficient Refractive index in each direction of the obtained polyester film was measured by Abbe's method and calculated by the general formula (1).

(Equation 2) (Where P is the plane orientation coefficient, n _{MD is} the refractive index in the MD direction, n
_TD: shows TD direction refractive index, n _Z film surface to the refractive index of the thickness direction perpendicular respectively)

(3) As a device for measuring stress at 100% elongation, a tensile tester (Tensilon (registered trademark) manufactured by Toyo Baldwin Co., Ltd.) in which a chuck portion was covered with a heating chamber was used. In the MD direction and the TD direction, sampling was performed in the elongation direction of 150 mm × the width direction of 10 mm, respectively, and the sample was fixed in a chamber heated to 100 ° C. in advance in a chamber of the apparatus and set at a distance of 100 mm, and then fixed at 100 mm / min. And the load was measured with a load cell attached to the tester. Then, the load at the time when the distance between the chucks was extended by 100 mm was read, and the stress (MPa) was calculated by dividing the load by the sample cross-sectional area before the tension. The display of the measurement results in the MD and TD directions indicates a direction corresponding to the extension direction of sampling.

(4) Molding Followability and Adhesion The obtained polyester film was treated with 100 parts by weight of a modified nylon 6 (melting point 220 ° C., decomposition temperature 280 ° C.), 15 parts by weight of isocyanate compound and epoxy resin 10
After being pressure-bonded to one side of an aluminum plate (JIS 1100, thickness 0.30 mm) via an adhesive consisting of parts by weight (thickness 15 μm), a heat treatment at 250 ° C. was performed to obtain a laminated aluminum material. Then, the laminated aluminum material was subjected to drawing at a drawing ratio of 3.5 with the film surface inside, and formed into a case having an inner diameter of 30 mm and a height of 60 mm. The appearance of the film in the body of the case was observed and evaluated according to the following criteria. ：: No change in appearance was observed. Δ: peeling of the film was slightly observed, and / or
Although the film does not peel, whitening is observed in the film. X: Remarkable peeling of the film is observed.

(5) Anticorrosive property 5 g of copper sulfate pentahydrate and 5 g of concentrated hydrochloric acid were added to 1000 cm of water.
Prepare a test solution diluted in ³ and add the above (4) in the test solution.
Was immersed at room temperature for 3 minutes. The state of deposition of metallic copper on the film surface after immersion was evaluated according to the following criteria. ：: No precipitation of metallic copper was observed. ×: Metallic copper is precipitated.

(6) Heat resistance After the aluminum surface of the case prepared in (4) was brought into contact with a solder bath at 270 ° C. for 10 seconds, the same evaluation as in (5) was performed.

Example 1 Intrinsic Viscosity in Dry State 0.65
(Measured in o-chlorophenol at 35 ° C., the same applies hereinafter)
Polyethylene (terephthalate-isophthalate) copolymer (terephthalic acid (TA) component / isophthalic acid (I
A) Pellets having a component molar ratio of 88/12) (containing 0.1% by weight of spherical silica particles having an average particle size of 1.5 μm)
Was supplied to an extruder and melt-extruded on a rotary cooling drum maintained at 20 ° C. to obtain a 240 μm-thick unstretched film. Next, the unstretched film is stretched 3.0 times in the MD direction, and both ends of the unstretched film along the MD direction are gripped and stretched 3.2 times in the TD direction. While giving 3% relaxation in the TD direction, heat treatment was performed at 190 ° C. to obtain a biaxially stretched polyester film having a thickness of 25 μm. Table 1 shows the properties of the obtained film.

Example 2 Instead of a polyethylene (terephthalate-isophthalate) copolymer, a polyethylene (terephthalate-naphthalene-2,6-dicarboxylate) copolymer having an intrinsic viscosity of 0.65 (terephthalic acid (TA) ) Component / naphthalene-2,6-dicarboxylic acid (NDCA) component molar ratio = 88/12), except that the same operation as in Example 1 was repeated. Table 1 shows the properties of the obtained film.

Examples 3 and 4, Comparative Examples 1 and 2 The same as Example 1 except that the molar ratio between the terephthalic acid (TA) component and the isophthalic acid (IA) component was changed as shown in Table 1. The operation was repeated. Table 1 shows the properties of the obtained film.

Comparative Example 3 A film having a thickness of 25 μm was obtained by inflation using a polyethylene copolymerized polyolefin as a film material. Table 1 shows the properties of the obtained film.

Comparative Example 4 The thickness of the unstretched film was 41
The same operation as in Example 1 was repeated, except that the thickness was changed to 8 μm and the stretching ratio in the MD and TD directions was changed to 3.8 times and 4.4 times. Table 1 shows the properties of the obtained film.
Shown in

Comparative Example 5 The same operation as in Example 1 was repeated, except that the unstretched film was changed to 36 μm, and the stretching ratio was changed to 1.2 times in both the MD and TD directions. Table 1 shows the properties of the obtained film.

[0033]

[Table 1]

[0034]

According to the present invention, excellent followability to the forming of an aluminum plate, excellent adhesion to the aluminum plate, excellent corrosion resistance of the aluminum plate, and these advantages are retained even after the heat history. There is provided a polyester film for bonding an aluminum plate for forming a capacitor case, which is particularly suitable for forming a capacitor case.

Continued on front page F term (reference) 4F071 AA43 AA46 AA84 AD06 AF02 AF15Y AF47 AF58 AH12 BB08 BC01 BC02 BC17 4J002 BC022 BG002 CF061 CF071 CF081 DE136 DE146 DE236 DJ016 DJ036 FD172 FD176 GF00 GQ00

Claims (4)

[Claims] 1. A film comprising a copolyester having a melting point of 210 to 245 ° C. and having a plane orientation coefficient of 0.10 to 0.16, and having a 100% elongation at 100 ° C. in the MD and TD directions. A polyester film for bonding a capacitor case, wherein stress is in a range of 10 to 150 MPa. 2. The polyester film for bonding a capacitor case according to claim 1, wherein the copolymerized polyester contains 0.001 to 40% by weight of particles having an average particle size of at most 2.5 μm. 3. A laminated aluminum material for a capacitor case, wherein the polyester film for bonding a capacitor case according to claim 1 or 2 is bonded to at least one surface of an aluminum plate. 4. A capacitor case using the laminated aluminum material for a capacitor case according to claim 3.