JPH0721070B2 - Polyester film and capacitor using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester film and a capacitor using the same as a dielectric.

[Prior Art] Conventionally, various polyester films and capacitors using the same have been known.

[Problems to be Solved by the Invention] However, such a conventional polyester film is
In various electronic devices, there is a drawback that the dielectric loss becomes large at a temperature of 80 ° C or higher, and thus the operating temperature range is limited to 80 ° C or lower.

It is an object of the present invention to improve the drawbacks of such a conventional polyester film, and to provide a film having a small dielectric loss even at a high temperature of 80 ° C. or higher and having a wide operating temperature range, and a capacitor using the film.

[Means for Solving the Problems] The present invention provides (1) a plastic film containing polyethylene terephthalate as a main component, the second-order transition temperature of the plastic film measured by a differential scanning calorimeter being 80 ° C. or higher,
Moreover, the difference between the second-order transition temperature and the melting point is 100 to 170 ° C., the melting specific resistance value is 1 × 10 ⁸ Ω · cm or more, and the crystallinity by the X-ray method is ^{8 to} 2
5% polyester film, and (2) Polyethylene terephthalate as a main component, the second-order transition temperature measured by a differential scanning calorimeter is 80 ℃ or more, and the difference between the second-order transition temperature and the melting point. Is 100-170 ° C, melting specific resistance is 1 × 10 ⁸ Ω · cm or more, and crystallinity by X-ray method is 8-25%.
The present invention relates to a capacitor characterized by using the above-mentioned polyester film as a dielectric.

In the present invention, polyethylene terephthalate (hereinafter PE
A polyester whose main component is T) is used, and it is preferable that PET is contained in an amount of 75 to 95% by weight, preferably 80 to 95% by weight. If the PET component is less than the above range, the dimensional stability and mechanical properties that are characteristic of the film may not be sufficiently exhibited, and if it exceeds the above range, the dielectric loss (hereinafter abbreviated as tan δ) improving effect of the present invention small.

In the present invention, various polymers other than PET are contained in the range of 25 to 5% by weight, preferably 20 to 5% by weight. Examples of the various polymers include polyethylene naphthalate, polyethylene-α, β-bis (phenoxy) ethane 4,4 ′ dicarboxylate, polyarylate, and polycarbonate. Among them, polyarylate is particularly preferable. Further, an inorganic or organic additive such as an antioxidant, a heat stabilizer, a lubricant, an ultraviolet absorber, a nucleating agent or a surface protrusion forming agent may be appropriately added.

The film of the present invention is a film in which the polymer containing PET as a main component is biaxially oriented, and the second-order transition temperature (hereinafter abbreviated as Tg) measured by a differential scanning calorimeter (DSC) of the film. Temperature is 80 ° C or higher, and Tg and melting point (Tm
Abbreviated as “)” in the range of 100 to 170 ° C. Outside the above range, the tan δ improvement effect is small,
Further, it is not preferable in terms of film moldability.

The melting specific resistance value (hereinafter abbreviated as ρ) at 280 ° C. of the film of the present invention is 1 × 10 ⁸ Ω · cm or more, preferably 2 × 1.
0 ⁸ Ω · cm or more. When ρ is less than the above value, ta of the present invention
The effect of improving nδ is small, which is not preferable. The upper limit of ρ is not particularly limited, but is preferably 1 × 10 ¹⁰ Ω · cm or less from the viewpoint of maintaining the film formability.

The crystallinity of the film according to the present invention by the X-ray method is 8 to
It is in the range of 25%, preferably 10 to 20%. Crystallinity is 8
% Of the present invention or larger than 25% of the present invention
nδ Improvement effect is small.

The melt viscosity of the film of the present invention is 1000 to 6000 poise (temperature
280 ° C and a shear rate of 200 sec ^-1 ) are preferable from the viewpoint of film formability.

The surface roughness (cutoff: 0.25 mm) according to JIS-B-0601 of the film of the present invention is preferably in the range of 0.01 to 0.2 μm.

The thickness of the film constituting the dielectric material of the present invention is not particularly limited, but is preferably in the range of 0.5 to 30 μm.

The heat shrinkage rate of the film constituting the dielectric material of the present invention is not particularly limited, but the range of 0.1 to 5% in the length direction and -1 to 5% in the width direction is preferable at 150 ° C. for 30 minutes. .

The capacitor of the present invention is manufactured by a known method such as a winding method or a lamination method. The conductor may be either a metal foil formed by forming a metal into a foil or a metal thin film formed by forming a metal on the above-mentioned dielectric by a known method such as vacuum deposition or sputtering. Examples of the metal forming the conductor include aluminum, zinc, tin, titanium, nickel, and alloys thereof, but are not limited to these.

The capacitor of the present invention may have any shape, but may be either a tamper having a normal lead wire or a type having no lead wire and being directly soldered to the substrate surface (so-called chip capacitor). Further, the capacitor of the present invention can be used for both AC and DC applications.

Next, a method for producing a film according to the present invention will be described.

First, carboxylic acid having terephthalic acid as a main component or its alkyl ester and glycol having ethylene glycol as a main component are added to calcium, magnesium, lithium,
130-260 ℃ in the presence of catalytic metal compounds such as elemental manganese
To perform esterification or transesterification. afterwards,
A catalyst compound consisting of antimony, germanium, and titanium elements and a phosphorus compound are added, and the temperature is 220 to 300 under high vacuum.
Carry out polycondensation reaction at ℃. The type of the phosphorus compound, such as phosphorous acid, phosphoric acid, phosphoric acid triester, phosphonic acid, phosphonate, is not particularly limited,
Two or more of these phosphorus compounds may be used in combination. The amount of the additive of the above-mentioned catalyst compound is not particularly limited, but it is preferable that the ratio of the catalyst metal compound such as calcium, magnesium, lithium and manganese to the phosphorus compound is included so as to satisfy the following formula. Desirable to be 10 ⁸ Ω · cm or more.

0.5 ≦ (M / P) ≦ 1.5 However, M: total number of moles of calcium, magnesium, lithium and manganese elements in the film, P: number of moles of phosphorus element in the film.

Further, ρ of the above-mentioned film shows the same value as ρ previously measured at the stage of the extruded polymer.

Further, at any stage from esterification or transesterification to polycondensation, if necessary, an antioxidant, a heat stabilizer, a lubricant,
An ultraviolet absorber, a nucleating agent, a surface protrusion forming agent, etc. are added.

The polycondensed polymer thus obtained is fed to an extruder together with various polymers in the range of 5 to 25% by weight, melt-extruded from a slit-shaped die and cooled and solidified to prepare an unstretched film. In this case, the multi-type polymer may be added at the stage when the polycondensation of PET is substantially completed, or may be pelletized in advance with PET, and may be used in the form of pellets, but it was measured by the DSC of the film which is an essential requirement of the present invention. It is essential that Tg is 80 ° C or higher and the difference between Tg and the melting point (mp) is in the range of 100 to 170 ° C. Specifically, using a pelletizer equipped with PET and a variety of polymers in advance with a Dalmage-type screw, the temperature is 260 to 300 ° C, and the convection time is 5
Pelletizing within a range of up to 30 minutes is suitable for the tan δ improving effect of the present invention.

Next, this unstretched film is biaxially stretched and oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used, but the sequential biaxial stretching method is particularly preferable in order to bring the crystallinity of the film into the range of the present invention.

The conditions for sequential biaxial stretching are not particularly limited, but after stretching 2.5 to 4.5 times in one direction, 3.
It is preferable to set the crystallinity of the film within the range of the present invention to be 0 to 5.0 times.

The stretching temperature may be in the range of 70 to 130 ° C. Usually, the stretching speed is preferably in the range of 10 ^{3 to} 5 × 10 ⁴ % / min.

Next, this stretched film is heat-treated. As the heat treatment conditions, a temperature of 130 to 240 ° C., preferably 150 to 220 ° C., and a time of 1 to 60 seconds are effective in keeping the crystallinity of the film within the range of the present invention.

Next, a method of manufacturing the capacitor according to the present invention will be described.

The film obtained as described above is used as a dielectric, and a metal foil or a metal thin film is used as a conductor to wind it in a flat plate or the same circle to form a capacitor element, but it is better to use a metal thin film for the conductor. The tan δ improving effect of the invention is great. As the metal thin film forming method in this case, a well-known vapor deposition method, sputtering method or the like can be used. Particularly, a vapor deposition film having a dielectric film thickness of 1.5 to 5 μm and a vapor deposition film thickness of 100 to 5000 Å is used for a capacitor. The most preferable method is to obtain the effects of the present invention.

Next, this capacitor element is subjected to pressing, heat treatment, end face sealing and lead wire attachment according to a conventional method to obtain a capacitor.

Although the present invention is characterized by the above capacitor, the film may be subjected to a known corona discharge treatment, and also for the purpose of imparting adhesiveness, heat sealability, moisture resistance, lubricity, surface smoothness, and the like. Multi-layered polymer, organic and / or
Alternatively, it may be used in a form coated with an inorganic composition. The capacitor of the present invention may be impregnated with insulating oil or the like to be used as a so-called oil-immersed capacitor.

[Operation] The present invention optimizes the second-order transition temperature, melting specific resistance, and crystallinity of a film to obtain Tg of the film,
It is considered that each factor such as non-conductivity and molecular orientation subtly interacted with each other and contributed to improve the dielectric loss.

[Method of measuring characteristics and method of evaluating effects] (1) Put 10 mg of a sample in a Perkin Elmer DSC-II type and replace the atmosphere with nitrogen. Then at a heating rate of 16 ° C / min
The temperature is raised to 280 ° C. and kept in this state for 5 minutes. The sample is then quickly quenched in liquid nitrogen. Put the rapidly cooled sample in DSC-II type cooled to room temperature,
The atmosphere is replaced with nitrogen again. Then, raise the temperature at 16 ° C / min (2nd RUN) and measure Tg and Tm. Further, Tm-Tg was set to ΔTmg.

(2) Melt resistivity (ρ) Counter electrode with a 1 cm gap (short electrode area: electrode area:
25 cm ² each, empty insulation resistance between the electrodes: 10 ¹² Ω or more), and the sample is extruded at 280 ° C. Then DC500V between electrodes
Is applied and the current I (mA) flowing at that time is obtained. 280
Ρ in ° C is obtained from the following equation.

ρ (Ω · cm) = 1.25 × 10 ⁸ / I (3) Film crystallinity A film sample that has been made into a fine powder by the freeze pulverization method is placed on a standard aluminum frame of an X-ray diffractometer (Rigaku Denki Co., Ltd.). First, wide-angle X-ray diffraction measurement was performed by the reflection method.

From the chart obtained, the Johnson method (JEJohnson, J.App
The crystallinity was calculated by Applied Polymer Science, 2 (5), 205 ('59)).

(4) Dielectric loss (tan δ) characteristics of capacitor A capacitor (capacity 0.1μF) is used at a temperature of 20 ° C and 100 ° C in an oven using a capacitance bridge (YHP) at 1KHz.
The anδ was measured. The measurement was carried out for 1000 pieces each, and if the ratio of the average value of tan δ at 20 ° C / the average value of tan δ at 100 ° C is 2.6 or more, high temperature tanδ characteristics: good, and if less than 2.6, high temperature tanδ Characteristic: judged to be defective.

(5) Intrinsic viscosity This is a value measured at 25 ° C using o-chlorophenol as a solvent.

(6) Metal analysis in film The elements such as calcium, magnesium, lithium and manganese in the film were quantified by atomic absorption method, and phosphorus element was measured by colorimetric method.

[Examples] The present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

Example 1 (1) Preparation of film of the present invention 100 parts by weight of dimethyl terephthalate, ethylene glycol 7
0 parts by weight, using 0.09 parts by weight of calcium acetate as a catalyst, transesterification reaction is carried out by a conventional method, the product antimony trioxide 0.03 parts by weight, trimethyl phosphate 0.15 parts by weight, phosphorous acid 0.02 parts by weight and dioxide. 0.1 part by weight of silicon (particle size: 1.2 μm) was added, and polycondensation was performed by a conventional method to obtain a polymer pellet having an intrinsic viscosity of 0.64 (polymer A).

Then, in another reaction kettle, 50 parts by weight of terephthalic acid, 50 parts by weight of isophthalic acid, 188 parts by weight of 4,4′-diacetoxydiphenylpropane and 0.06 part by weight of tetrabutyl titanate as a catalyst were charged, and the mixture was heated at 200 ° C. to 245 ° C. Deacetic acid reaction was performed at ℃. Then, polycondensation reaction was performed under a high vacuum degree of 290 ° C. to obtain polymer pellets having an intrinsic viscosity of 0.625 (polymer B).

Then, the total amount of 100 kg in a ratio of 85 parts by weight of polymer A and 15 parts by weight of polymer B was vacuum dried at 180 ° C. for 4 hours, and then supplied to a pelletizer (Dalmade type screw, L / D = 35).
Pelletization was carried out at a temperature of 10 minutes for a pellet to obtain pellets.

Then, the pellets were vacuum dried at 180 ° C. for 4 hours, fed to an extruder, melt-extruded at 280 ° C., and wound on a cooling drum at 60 ° C. to prepare an unstretched sheet.

Next, this unstretched sheet was stretched 3.8 times in the longitudinal direction at 95 ° C. This stretching was carried out with a peripheral speed difference between the two sets of rolls, and the stretching speed was 10,000% / min. This uniaxially stretched film was stretched with a stenter at a stretching rate of 10,000% / min to produce 105
The film was stretched 4 times in the width direction at 0 ° C. and heat-treated at 180 ° C. for 10 seconds under a constant length to obtain a biaxially oriented film having a thickness of 6 μm.

The film Tg is 88 ℃, ΔTmg is 160 ℃, and the crystallinity is 16%.
Met. Also, ρ measured during melt extrusion is 3 × 10 ⁸
It was Ω · cm (film A).

(2) The film obtained in (1) above is set in an electron beam vacuum vapor deposition apparatus and aluminum is used to obtain a film resistance of 3Ω / □.
It was vapor-deposited so that. This vapor-deposited film is slit, a capacitor element is made by applying it to an element winding machine, and further end face sealing and lead wire attachment are performed by a conventional method.
A capacitor (capacity 0.1 μF) was made (capacitor A).

(3) For each of the 1000 capacitors created in Evaluation (2), 20 ℃,
The tan δ at 100 ° C was measured. Tan δ measured at each temperature
The average value ratio was 3.1, and the tan δ characteristic was good (Table 1).

Examples 2 to 4 and Comparative Examples 1 to 6 A capacitor (Example 2) prepared in exactly the same manner as in Example 1 except that the polymer B was changed to 20 parts by weight, and
Table 1 shows capacitors (Example 3) prepared in exactly the same manner except that the heat treatment temperature was changed, and capacitors (Example 4) prepared in exactly the same manner except that the kind of the polymer B was changed to polycarbonate. As shown, the tan δ characteristics were good.

However, in Example 1, the pelletizing conditions were changed, the film manufacturing conditions such as the heat treatment temperature were changed (Comparative Examples 1 to 4), and the metal / phosphorus ratio in the film was changed to change the melt specific resistance value of the film. Of the film (Comparative Example 5) having a different amount of PET, a film having a different amount of PET components, etc., the physical properties of the film, which is a dielectric, do not satisfy any of the requirements of the claims of the present invention.
A capacitor with improved tan δ characteristics under high temperature could not be obtained.

[Effects of the Invention] The film according to the present invention contains PET as a main component and T
Since the characteristics of g, ΔTmg, ρ, and crystallinity are optimized, it has the effect of improving the tan δ characteristics at high temperatures.

Good tan δ characteristics at high temperature means that AC,
Regardless of direct current, it is stable up to a high temperature range, that is, the operating temperature range is widened, and thus continuous long-term service is possible, which is particularly suitable for capacitor applications. Further, the film can be used not only for capacitors but also for cables, motors, and other electrical insulation applications.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 67:00 B29L 7:00 C08L 67:00

Claims (2)

[Claims] 1. A plastic film containing polyethylene terephthalate as a main component, which has a second-order transition temperature of 80 ° C. or higher measured by a differential scanning calorimeter of the plastic film and a difference between the second-order transition temperature and the melting point of 100. Polyester film having a melting specific resistance of 1 × 10 ⁸ Ω · cm or more and a crystallinity of 8 to 25% by X-ray method. 2. Polyethylene terephthalate as a main component, the second transition temperature measured by a differential scanning calorimeter is 80 ° C. or higher, the difference between the second transition temperature and the melting point is 100 to 170 ° C., and the melting specific resistance value is 1. A capacitor characterized by using a polyester film having a crystallinity of 8 to 25% by an X-ray method as × 10 ⁸ Ω · cm or more as a dielectric.