JP2757423B2 - Laminated film - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thin film polyester film having a support, and more particularly, to a laminated film in which a polyester film is more smoothly formed than a polyolefin support. The present invention relates to a polyester film which can be peeled off and has no defects such as pinholes, and is excellent as a dielectric for capacitors and the like.

[Prior art] In recent years, as electronic machines have become smaller and lighter, applications such as capacitors have been increasingly miniaturized, and thinner films have been required. It is entering the age. Examples of such ultra-thin films include, for example, JP-A-58-5526 and JP-A-58-5526.
As disclosed in JP-A-58-132520 and JP-A-58-136417, there is known a method in which different kinds of polymers are stretched in a laminated state to form a laminated film, and one is peeled off and used as an ultrathin film. Have been.

[Problems to be Solved by the Invention] Such a conventional laminated film is easily broken at the time of peeling, and a pinhole is easily formed. In addition, there is a problem that the obtained ultrathin film has extremely poor capacitor characteristics.

An object of the present invention is to provide a laminated film having a thin polyester layer, which eliminates the above-mentioned drawbacks, is resistant to tearing, has good peeling stability, has very few pinholes, and is excellent as a capacitor film. It is.

[Means for Solving the Problems] To achieve the above object, the present invention provides a laminated film comprising a polyester film on at least one side of a polyolefin film,
The polyester film comprises a laminated film having an intrinsic viscosity of 0.58 or more and 1.5 or less and a friction coefficient of 0.7 or more and 1.5 or less.

The polyolefin film in the present invention is a non-oriented, uniaxially or biaxially oriented film made of an olefin polymer or copolymer, and the thickness is not particularly limited, but a film having a thickness of 1 to 10 μm is used in the present invention. Is suitable for

Representative examples of the polyolefin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, and polybutene.
1, poly-4-methyl-pentene-1, or a copolymer or a mixture thereof, but preferred for the present invention is a propylene copolymer having a melting point of 100 to 160 ° C (hereinafter abbreviated as PPC). )), And among these, the melting point is 100.
Preferred is a propylene copolymer at ~ 155C. This copolymer is preferably a polymer composed of a copolymer of 80 to 97 mol% of propylene and 3 to 20 mol% of olefins other than propylene. Furthermore, in the polyolefin layer of the present invention,
It is preferable to add various known release agents, for example, silicon, petroleum resin, terpene resin, higher fatty acid waxes and the like. Also, various known additives, for example, antioxidants,
Even if an antistatic agent, a coloring pigment, an antiblocking agent, an ultraviolet absorber or the like is added, there is no problem.

The polyester of the present invention means a linear aromatic polyester, for example, polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, poly-1,4-cyclohexane dimethylene terephthalate and the like. These may be homopolymers or copolymers of other components in the range of 20% or less of the number of repeating structural units. Particularly preferred in the present invention is polyethylene terephthalate (hereinafter referred to as PE
T).

The polyester film of the present invention is biaxially stretched and substantially biaxially oriented.

The intrinsic viscosity of the polyester film is 0.58 or more and 1.5 or less, preferably 0.62 or more and 1.3 or less, more preferably 0.6 or more.
5 or more and 1.0 or less. If it is less than 0.58, pinholes increase and the breakdown voltage significantly decreases. If the intrinsic viscosity is more than 1.5, troubles are likely to occur during extrusion film formation, which is not preferable.

The coefficient of friction of the polyester film is 0.7 or more and 1.5 or less,
Preferably it is 0.7 or more and 1.0 or less. When the coefficient of friction is smaller than 0.7, the film running property is good, but it is easy to cause winding deviation at the time of vapor deposition, micro slit, etc. Conversely, when it is larger than 1.5, the film running property is poor, and the ultrathin polyester film is easily damaged, It is not preferable because it leads to an increase in pinholes and a decrease in breakdown voltage.

To make the coefficient of friction of the polyester film within the scope of the present invention, the type of inorganic particles or organic particles, for example,
It can be achieved by appropriately combining silica, thyroid, calcium carbonate, calcium phosphate, kaolin, titanium oxide, alumina, epoxy particles, and the like, and their particle diameters and amounts, and incorporating them into the polyester. In particular, in the present invention, it is preferable to contain one or a combination of two or more of spherical silica, porous silica, and thyroid having an average particle diameter in the range of 0.2 to 1.5 μm.

The thickness of the polyester layer of the present invention is 0.3 to 1.5 μm, preferably 0.3 to 1.0 μm. If the thickness is less than 0.3 μm, there is a problem that the film is broken during film formation or peeling, which is not preferable. Also, when the thickness is 1.5 μm, preferably more than 1.0 μm, the workability is good even with a single film,
It is not preferable because it is not necessary to form a laminated film as in the present invention.

The laminated film of the present invention is obtained by laminating the polyolefin layer and the polyester layer, and the lamination structure is not particularly limited, but two layers of polyester / PPC, polyester / PPC
/ Three layers of polyester are preferred. Also, polyester /
In the case of a three-layer construction of PPC / polyester, the polyester films on both sides may have the same thickness or different thicknesses within the scope of the present invention.

The average value of the peeling force between the polyester film and the polyolefin film of the laminated film of the present invention is 0.2 g / cm to 0.7 g /.
cm range. When the average value of the peeling force is less than 0.2 g / cm, a problem that the polyester film and the polyolefin film are peeled during the film formation is apt to occur, which is not preferable. On the other hand, when the average value of the peeling force exceeds 0.7 g / cm, the film is likely to be broken or a hole (pinhole) in the polyester film is likely to occur at the time of peeling.

Further, the stability of the peeling force is preferably the average value of the peeling force ±
0.1 g / cm, more preferably ± 0.05 g / cm, and even if the average value is in the range of 0.2 to 0.7 g / cm, poor stability may result in the occurrence of pinholes and the like. Not preferred.

At the interface between the polyester film and the polyolefin film of the laminated film of the present invention, that is, when the polyester film and the polyolefin film are peeled off, the depression due to the indentation of the protrusion of the polyester film surface into the polyolefin film surface has an average diameter of 0.2. -5 μm, and the distribution density is 500-50
The number is preferably 00 pieces / 0.1 mm ² , more preferably 1000 to 3000 pieces / 0.1 mm ² . Exceeding this range is not preferable because the fluctuation of the peeling force between the polyester film and the polyolefin film becomes large. That is, when a metal is deposited on the polyester film surface of the laminated film of the present invention and the capacitor element is formed while being peeled off, winding deviation or the like is likely to occur. If it is less than this range, the peeling force tends to be stable, but the lubricity of the polyester film deteriorates, which is not preferable.

Next, specific examples of the method for producing a laminated film of the present invention will be described. However, it is not limited to this example.

The polyester resin and the polyolefin resin containing the particles are supplied to separate extruders so as to fall within the scope of the present invention, melted, merged in a die, formed into a sheet, and the sheet is heated to 65 ° C. Wrap it around a metal roll, cool it,
It is a non-stretched laminated sheet.

The laminated sheet is longitudinally heated at a temperature of 80 to 110 ° C. to 3.0 to 4.
The laminated film of the present invention can be obtained by stretching the film at 0-fold and at a temperature of 90 to 120 ° C in a width direction of 4.0 to 5.5 times, and then performing a heat treatment at a temperature of 180 to 230 ° C. For the stretching of the laminated film, any of a sequential biaxial stretching method and a simultaneous biaxial stretching method can be applied.

The thus-obtained laminated film is subjected to vapor deposition, coating, lamination and the like on the polyester film surface, and then the PPC layer is peeled off and used. Although there is no particular limitation on the peeling method, continuous peeling is easy if the laminated film is nipped between a pair of nip rolls and the polyester film is peeled off along one roll surface. Note that the above vapor deposition and the like may be performed after peeling.

The laminated film of the present invention can be used for many uses such as a dielectric for a capacitor and a ribbon for thermal transfer.

[Measurement Method] The measurement methods such as physical properties and evaluation criteria used in the present invention are as follows.

(1) Intrinsic viscosity of polyester The polyester was dissolved in orthochlorophenol at 25 ° C, and the intrinsic viscosity was measured by a conventional method.

(2) Coefficient of friction According to ASTM D-1894, it was measured with a slip tester manufactured by Toray Industries, Inc. Each value is a dynamic friction coefficient in a laminated state.

(3) Film thickness The thickness was measured using an electronic micro thickness gauge.

(4) Peeling force When the width of the laminated film is W (cm), the polyester film layer is continuously peeled at a peeling angle of 180 ° at 200 mm / min.
The tension applied to the polyester film at the time of peeling was measured with a tensiometer. This tension is T
In the case of (g), the peeling force can be obtained by T / W (g / cm).

(5) Stability of Peeling Force The peeling force was recorded on a chart, the variation with respect to the average value was determined, and indicated by the following criteria. At that time, ± 0.05g / cm
It is said that the peeling force is stable within.

○: Within ± 0.05 g / cm △: Within ± 0.1 g / cm ×: Within ± 0.2 g / cm (6) Amount of penetration into the polyolefin film surface The laminated film was peeled off, and aluminum was deposited on the peeled side of the polyolefin film And the average diameter of the dents and the distribution density of the dents due to the penetration into the surface of the polyolefin film were determined from a photograph of the surface state taken with a differential interference microscope.

(7) Number of pinholes The laminated film is peeled off using a slitter, and the peeled polyester film is laminated on a white film without wrinkles. Magic ink was sprayed over the entire area of 1 m ² , and the number of spots formed on the white film was defined as the number of pinholes.

 ◎: 0 pinholes ○: 1 to 4 pinholes ×: 5 or more pinholes XX: 10 or more pinholes (8) Dielectric breakdown voltage (DC) Measured according to JIS C2319.

Electrode surface: 8mmφ Step-up speed: 50V / sec (9) Capacitor processability When a laminated film is deposited, micro-slit, or wound with an element, any deviation in the end face in any process is called winding deviation, The condenser processability was determined based on the degree.

 ：: End surface deviation within 0.3 mm △: End surface deviation of more than 0.3 mm and less than 1.0 mm ×: End surface deviation of 1.0 mm or more In addition, when slippage is poor and wrinkles or the like are formed, it was evaluated as ×.

[Effects of the Invention] By setting the configuration of the laminated film of the present invention within the range of the present invention, the fluctuation of the peeling force of the ultra-thin polyester film layer is reduced, the capacitor is easily processed, and the resistance of the polyester film is reduced. The voltage and electric characteristics were improved, and a polyester laminated film suitable for a capacitor could be obtained.

[Example] Example 1 The following two types of raw materials (pellets) were prepared.

PET: intrinsic viscosity 0.75dl / g, melting point 260 ° C. Wet silica with a particle size of 0.5 μm as the outer particle
Contains 0.25% and 0.03% of those with an average particle size of 1.5 μm.

PPC: melting point 130 ° C. A propylene / ethylene random copolymer having an ethylene content of 6% by weight. Contains 0.03% of Toray Silicone (SH3746) as a release agent.

The two types of raw materials are supplied to separate extruders and melt-extruded at 280 ° C., and the respective melts are combined in a T-type die to form a three-layer structure of polyester / PPC / polyester,
This is wrapped around a 65 ° C hot water drum to cool and solidify,
A three-layer laminated sheet was obtained.

After heating this sheet to 90 ° C, 3.5 mm in the longitudinal direction
The film was stretched twice and cooled immediately. Next, it is heated again to 100 ° C., stretched 4.5 times in the width direction, heat-treated at a temperature of 210 ° C. for 6 seconds while maintaining tension, then relaxed by 5%, gradually cooled, cooled to room temperature, and wound up. Was. Thus, a laminated film having a thickness of each polyester layer on both sides of 0.5 μm and a thickness of the central PPC layer of 5 μm, and a total of 6 μm was obtained.

When the PET layer was peeled off, the peeling force was very stable at 0.55 ± 0.03 g / cm. The intrinsic viscosity of this ultrathin polyester film was 0.72 dl / g, and the number of pinholes was 0 / m ^2, which was not generated at all. The coefficient of friction is 0.8 and the peeled P
The hollows in the PC layer have an average diameter of 1.5 μm and a density of 1500/0.
It was 1 mm ² , and no winding deviation occurred at all in the element winding of the vapor deposition, the micro slit, and the capacitor, and the dielectric breakdown voltage was as good as 330 V / μm. The results are shown in Table 1.

Example 2 A film was formed in exactly the same manner as in Example 1 except that the amount of the release agent (Toray Silicone SH-3746) added to the PPC layer was 0.01%. The peeling force was slightly unstable at 0.65 ± 0.10 g / cm, the pinholes were 3 holes / m ² , and the densities of the hollows of the peeled PPC layer were 1600 / 0.1
It was mm ^2.

Comparative Example 1 0.5% of wet silica having an average particle size of 0.5 μm was added to the polyester layer and 0.5% of wet silica having an average particle size of 1.5 μm was added to the polyester layer.
Except that it was set to 075%, a film was formed in exactly the same manner as in Example 1.
Peeling force is very unstable, 0.58 ± 0.24g / cm, 3 pinholes / m ² , Density of peeled PPC layer is 3300 / 0.1mm
² , which is a little worse than that of Example 1 with a dielectric breakdown voltage of 300 V / μm. The coefficient of friction was 0.55, and a winding deviation occurred during vapor deposition. The intrinsic viscosity of the PET film was 0.70 dl / g. Table 1 shows the results.

Comparative Example 2 The intrinsic viscosity of the polyester chip of Example 1 was 0.53 dl / g.
A film was formed in the same manner as in Example 1 except for the above. The peel force is
Although it was stable at 0.56 ± 0.04 g / cm, the number of pinholes in the peeled ultra-thin PET film increased sharply to 50 / m ^2, and the dielectric breakdown voltage decreased to 270 V / μm. The intrinsic viscosity of this film was 0.52 dl / g.

Comparative Example 3 0.05% of wet silica having an average particle size of 0.5 μm was added to the polyester layer, and wet silica having an average particle size of 1.5 μm was used.
A film was formed in the same manner as in Example 1 except that the content was 0.03%. The peel force is
Although it was very stable at 0.52 ± 0.02 g, the coefficient of friction was very high at 1.8, which caused problems in the winding property and running property of the film, and the film was damaged. 5 pinholes / m ² ,
The hollow density was 400 / 0.1 mm ² .

Claims (2)

(57) [Claims] 1. A laminated film comprising a polyolefin film and a polyester film compounded on at least one surface thereof, wherein the polyester film has an intrinsic viscosity of 0.58 or more and 1.5 or less and a friction coefficient of 0.7 or more and 1.5 or less. Laminated film. 2. The polyester film having a thickness of 0.3 to 1.5.
μm, and the average value of the peeling force between the polyolefin film and the polyester film is 0.2 to 0.7 g / cm, and the depression due to the indentation of the protrusions on the polyester film surface of the peeled surface after peeling into the polyolefin film surface has an average diameter of 0.2. ５5 μm, and the distribution density is 500-5000 pieces /
The laminated film according to claim (1), which is a 0.1 mm ^2.