JPS60230306A - Biaxial orientation polyester film for capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a biaxially oriented polyester film for capacitors with improved electrical properties.

[Prior art and its problems]

In recent years, with the trend toward ultra-miniaturization of electronic devices, there has been a growing demand for ultra-thin capacitor films of 5μ or less, and even 1.5μ or less for use as capacitor dielectrics. The polyester film must have a volume resistivity in the temperature range where electrical equipment rises, specifically in the temperature range from room temperature to 150°C.
It is necessary that the dielectric breakdown voltage is maintained high.

Conventionally, as a method for improving the above-mentioned electrical properties, a method has been proposed in which a phosphorus compound is added to produce a polyester film with high electrical insulation resistance (for example, Japanese Patent Publication No. 48-41277,
Special Publication No. 4B-41712) is known. but,
These polyester films are extremely thin with a thickness of 5μ or less,
Furthermore, ultra-thin materials with a thickness of 1.5 μm or less have the disadvantage that their electrical properties, particularly their dielectric breakdown voltage, are not sufficiently high.

[Purpose of the invention]

The object of the invention is to avoid the above-mentioned disadvantages, viz.

An object of the present invention is to provide a polyester film for capacitors having a high dielectric breakdown voltage.

[Structure of the invention]

In order to achieve the above object, the present invention has a ninth-order configuration, that is, a melting temperature of 240 to 255°C and an intrinsic viscosity of 0.
62 [A biaxially oriented polyester film for capacitors in which a metal compound containing at least one metal element of Mn and Ca elements and a compound containing a phosphorus element are mixed in the following ratio. This is a characteristic feature.

07≦(M/P　)≦1.4 Mn in the polyester film.

Total number of moles of Ca element, P: number of moles of phosphorus element in the polyester film.

The polyester film referred to in the present invention is a polyethylene terephthalate copolymer copolymerized with terephthalic acid or its ester as an acid component, ethylene bole as a glycol component, and a small amount of a sixth component (described later). It is a biaxially oriented film.

The melting temperature of this film is in the range 240-255°C, preferably 245-250°C. Melting temperature is 240℃
If it is too small, it will be difficult to dry before extrusion.

In order to make the melting temperature of this film 240 to 255°C, acid components such as inphthalic acid, naphthalene-2,6-dicarboxylic acid, and adipic acid, diethylene glycol, tetramethylene glycol, and neopentyl glycol are required as the sixth component. .

It is necessary to copolymerize glycol components such as cyclohexane dimetatool and bisphenol S. Among these, isophthalic acid, cyclohexane dimetatool, and bisphenol S are particularly preferred, and cyclohexane dimetatool is most preferred. For tools, the copolymerization ratio is preferably 1 to 10 molar (to terephthalic acid or its ester).

The film of the present invention has an intrinsic viscosity of 0.620 or more, preferably 0.655 or more. There is no particular upper limit to the intrinsic viscosity, but if you try to make it softer, the polycondensation time will become longer, the load on the extruder screw during molding will be greater, which is unfavorable from the productivity point of view, and the thickness may become uneven. big shi,
As a result, variations in dielectric breakdown voltage (hereinafter abbreviated as BDV) increase. Typically, the upper limit is 0.680.

It is necessary that the film of the present invention contains a metal compound containing at least one of the metal elements Mn and Ca and a compound containing the phosphorus element so as to satisfy the following formula.

0.7≦(M/P)≦1.4 Preferably.

0.8≦(M/P　)≦1. Ma However, 1M: Mn in the polyester film.

Total number of moles of Ca element, P: number of moles of phosphorus element in the polyester film. If M/P is less than 0.7, the polycondensation rate will decrease and 0°62
It is difficult to obtain a polyester film with an intrinsic viscosity of 0 or more. On the other hand, if M/P exceeds 1.4, the electrical insulation properties of the polyester film will be insufficient, and the desired effect of increasing the BDV will not be achieved.

That is, 0.7≦(M/P)≦1.4. Preferably, the range of 0.8≦(M/'P)≦1.2 is essential in terms of increasing the BDv.

Mn contained in the polyester film of the present invention.

Specific examples of the metal compound containing at least one metal element of the Ca element include calcium acetate, manganese acetate, manganese chloride, etc.A.

The compound containing the phosphorus element contained in the polyester film of the present invention is phosphoric acid, phosphorous acid, mono-, di-, or triester of phosphoric acid, phosphonic acid, and phosphonate.

The film of the present invention is a biaxially oriented film, that is, a biaxially stretched film. Although the degree of orientation is not particularly limited, the refractive index of the film in the longitudinal and lateral directions is measured and the values are about 1.600 to 1.700, respectively. Note that the refractive index is measured using an Abbe refractometer.

Next, a method for producing a polyester film for capacitors according to the present invention will be explained.

First, terephthalic acid or its ester, ethylene glycol, and the sixth component to be copolymerized are subjected to a diesterification or transesterification reaction using a conventional method.
It is desirable to add the metal compound containing at least one metal element such as the ca element into the polyester raw material at the initial stage of polycondensation.

The phosphorus compound can be added at any time from the substantial completion of transesterification or esterification to the initial stage of polycondensation. When adding two or more types of phosphorus compounds, the order of addition is not particularly limited.

In order to obtain a predetermined M/P in a polyester film, when using a phosphorus element-containing compound that easily scatters during one reaction, it is necessary to carefully adjust the amount at the incorporation stage.

In addition, in the production of conventional capacitor films, known inert particles effective for improving lubricity, such as calcium carbonate, barium sulfate, titanium oxide, and kaolin, can be used. When adding the inert particles, they may be added at any stage as long as they can be uniformly dispersed, but it is most suitable to add them as an ethylene glycol slurry.

Then, after completing the transesterification or esterification reaction 9
Polyester can be obtained by carrying out a polycondensation reaction using a commonly used polymerization catalyst. As the polycondensation reaction catalyst, antimony trioxide, germanium dioxide, titanium compounds, etc. are preferable. Using the thus obtained polyester as a raw material, the polyester is first cast into a sheet by melt extrusion according to a conventional method.Then, the sheet is biaxially stretched and heat treated by a known method to produce the biaxially oriented polyester film for capacitors of the present invention. Manufacture.

〔Effect of the invention〕

The present invention has the following excellent effects as a polyester film for capacitors.

(1) Breakdown voltage (BIIV) is significantly improved.

(2) High insulation resistance, as a dielectric material from room temperature to 150%
Can withstand long-term use in the ℃ range.

(3) The film is less likely to break during film formation and is useful for film formation of ultra-thin objects.

Therefore, by using the capacitor film of the present invention, it is possible to make the capacitor ultra-small.

[Method of measuring characteristics]

Note that the method for measuring characteristics in the present invention is as follows.

(1) Intrinsic viscosity of polymer and film Measured at 25°C using 0-chlorophenol as a solvent.

(2) Breakdown voltage (BDV) Using a DC withstand voltage tester, , r z 5-C-2! i
Measured according to No. 18.

(3) Melting temperature (Tm) 10 mg of the sample was placed in a DSC-It model manufactured by PerkinElmer, and the atmosphere was replaced with nitrogen. Next, the heating rate is 10”07
The sample is heated to 280° C. in minutes and held at this state for 5 minutes.Then, the sample is quickly quenched in liquid nitrogen. The rapidly cooled sample was placed in a DSC-■ mold that had been cooled to room temperature, and the atmosphere was replaced with nitrogen again.
The temperature is raised at a rate of 1/min, and an endothermic peak due to melting of the sample is drawn. Let T be the temperature at the valley of this peak.

(4) Metal analysis Mn and Ca in the film were determined by atomic absorption spectrometry, and phosphorus was determined by colorimetry.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on Examples.

Example 1 100 parts by weight of dimethyl teleketalate, 70 parts by weight of ethylene glycol, 2.3 parts by weight of cyclohexane dimetatool, and 0.0 parts by weight of calcium acetate as a transesterification catalyst.
09 parts by weight 9 Antimony trioxide as polymerization catalyst 0.05
Parts by weight were added, and a theoretical amount of methanol was distilled out between 140 and 220°C to complete the transesterification. Subsequently, 0.1 part by weight of dimethylphenylphosphonate and 0.0 parts of phosphorous acid were added to the system.
．． After adding 0.6 parts by weight, the pressure in the system was gradually reduced, and the temperature was raised to 285° C. under a reduced pressure of 1 mmHg or less to distill off ethylene glycol, and the reaction was completed in 4 to 5 hours.

The intrinsic viscosity of the obtained polyester copolymer was 0.650.
Met.

The polymer was melt-extruded using a 90 mmφ extruder at 290°C to obtain an unstretched sheet, and then longitudinally stretched at a longitudinal stretching ratio of 3.
Biaxially stretched at 5x and lateral stretching ratios of 3 and 7x.

A film with a thickness of 4μ was obtained by heat treatment at 200°C.

The BDV of the film was 550 V/p, and it was confirmed that it exhibited excellent properties. Also, Ca in the film
, when the amount of phosphorus was determined by metal analysis, Ca was 195pp.
m= Phosphorus detected at 150 ppm.

When M/P was calculated, it was 1.01. T is 248.8"
0. The intrinsic viscosity was 0.631.

Examples 2-5. Comparative Examples 1-7 As shown in Table 1, Examples 2-5. and comparative example 1~
Example 7 was carried out in exactly the same manner as in Example 1, except that the conditions such as the third component, the metal compound, the phosphorus compound zero polycondensation time, and the film thickness were changed.

Table 1 shows the evaluation results for each example and comparative example.

Examples 2 to 5 all meet the requirements of the present invention, and the BDV is very high and good.

On the other hand, since Comparative Examples 1 to 7 do not satisfy any of the requirements of the present invention, the BDV is low and inferior.

As is clear from Table 1, only when the two requirements of the present invention are met, the film exhibits excellent high BDV characteristics and is useful as a polyester film for capacitors.

Claims (1)

[Claims] (1) Melting temperature is 240-255℃, intrinsic viscosity is 062
0 or more, and a metal compound containing at least one metal element selected from Mn and ca elements. A biaxially oriented polyester film for capacitors containing a compound containing elemental phosphorus in the following proportions. 0.7≦(M/P)≦1.4 where 1M: Mn in the polyester film. Total number of moles of Ca element, P: number of moles of phosphorus element in the polyester film.