JPH02219648A - Laminated film - 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 [Field of Industrial Application] The present invention relates to a thin polyester film having a support, and more specifically, in the laminated film, the polyester film is smoother than the polyolefin support. This invention relates to a polyester film that can be peeled off, has no defects such as pinholes, and is excellent as a dielectric for capacitors.

[Prior Art] In recent years, as electronic machines have become smaller and lighter, applications such as capacitors have become smaller and smaller, and the films used in them are also required to be thinner.
We have entered the submicron era. Examples of such ultra-thin films include, for example, JP-A-58-5526, JP-A-58-132520, and JP-A-58-13641.
As in Publication No. 7, different types of polymers are stretched in a laminated state to form a laminated film, and then one side is peeled off.
It is known to be used as an ultra-thin film.

[Problems to be Solved by the Invention] Such conventional laminated films are easily torn when peeled off, and pinholes are easily formed. Further, there was a problem in that the capacitor properties of the obtained ultra-thin film were significantly inferior.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a laminated film having a thin polyester layer that is hard to tear, has good peeling stability, has extremely few pinholes, and is excellent as a capacitor film. It is.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration, that is, in a laminated film formed by combining a polyester film on at least one side of a polyolefin film, the intrinsic viscosity of the polyester film is 0.58 or more1.
5 or less and a friction coefficient of 0.7 or more and 1.5 or less.

The polyolefin film in the present invention refers to a non-oriented, -axially oriented or biaxially oriented film made of an olefin polymer or copolymer, and the thickness is not particularly limited, but a film of 1 to 10 μm is preferred. Appropriate for inventions.

Typical examples of polyolefins include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, polybutene-1,
Examples include poly-4-methyl-pentene-1, copolymers and mixtures thereof, but preferred in the present invention is a propylene copolymer (hereinafter abbreviated as PPC) having a melting point of 100 to 160°C. Among these, propylene copolymers having a melting point of 100 to 155°C are preferred.

This copolymer is preferably a copolymer of 80 to 97 mol% of propylene and 3 to 20 mol% of an olefin other than propylene. Furthermore, the polyolefin layer of the present invention contains various known mold release agents, such as silicone,
It is preferable to add petroleum resins, terpene resins, higher fatty acid waxes, and the like. Furthermore, there is no problem even if various known additives such as antioxidants, antistatic agents, coloring pigments, antiblocking agents, and ultraviolet absorbers are added.

The polyester of the present invention includes linear aromatic polyester,
For example, it means polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, poly 1,4-cyclohexane dimethylene terephthalate, and the like. These may be homopolymers or may be copolymerized with other components in an amount of 20% or less of the number of repeating structural units. Particularly preferred for the present invention is polyethylene terephthalate (hereinafter abbreviated as PET).

The polyester film of the present invention is stretched in two wheel directions and is substantially biaxially oriented.

The intrinsic viscosity of the polyester film is 0.58 or more1.
5 or less, preferably 0.62 or more and 1.3 or less, more preferably 0.65 or more and 1.0 or less. If it is smaller than 0.58, the number of pinholes will increase and the breakdown voltage will drop significantly.
If the intrinsic viscosity is greater than 1.5, troubles tend 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 0.7 or more and 1.0 or less. If the coefficient of friction is less than 0.7, the film has good running properties, but it is likely to cause misalignment during vapor deposition, microslitting, etc. On the other hand, if it is greater than 1.5, the running properties of the film will be poor, resulting in an extremely thin polyester film. It is undesirable because it is easily damaged, leading to an increase in pinholes and a decrease in dielectric breakdown voltage.

In order to keep the friction coefficient of the polyester film within the range of the present invention, the type of inorganic or organic particles, such as silica, siloid, calcium carbonate, calcium phosphate, kaolin, titanium oxide, alumina, epoxy particles, etc., and their particle diameters are required. This can be achieved by appropriately combining the amounts added 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 siloid 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 0.3~1゜5μm1
Preferably it is 0.3 to 1.0 μm.

If the thickness is less than 0.3 μm, it is not preferable because there is a problem of tearing during film formation or peeling.

Further, if the thickness is more than 1.5 μm, preferably 1.0 μm, it is not preferable because the workability of the film alone is good and there is no need to form a laminated film as in the present invention.

The laminated film of the present invention is a laminate of the above-mentioned polyolefin layer and polyester layer, and the laminated structure is not particularly limited.
A triple layer of PPC/polyester is preferred. Further, in the case of a three-layer structure of polyester/PPC/polyester, the thickness of the polyester films on both sides may be the same or may be different 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/an ~
The range is 0.7 g/cm. Average value of peeling force is 0.2
If it is less than g/cm, the polyester film and the polyolefin film tend to peel off during film formation, which is not preferable.

Moreover, if the average value of the peeling force exceeds 0.7 g/an, it is not preferable because the film is likely to break or holes (pinholes) in the polyester film will occur during peeling.

The stability of the peeling force is preferably the average value of the peeling force ±0.
．． 1 g/an, more preferably ±0.05 g/an, and even if the average value is in the range of 0.2 to 0.7 g/an, poor stability may result in pinholes etc. This is not desirable because it can happen.

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 depressions due to the protrusions on the surface of the polyester film biting into the surface of the polyolefin film have an average diameter of 0. .2 to 5 μm, and its distribution density is 500 μm.
~5000 pieces 10.1mff1. Another 1000-30
00 pieces and 10.1 mtrr is preferable. If it exceeds this range, the variation in peeling force between the polyester film and the polyolefin film will increase, which is not preferable.

That is, when metal is vapor-deposited on the surface of the polyester film of the laminated film of the present invention and then peeled off to produce a capacitor element, winding misalignment is likely to occur. If it is less than this range, the peeling force tends to be stable, but the slipperiness of the polyester film deteriorates, which is not preferable.

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

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

3. The laminated sheet is heated in the longitudinal direction at a temperature of 80 to 110°C.
Stretched 0 to 4.0 times and 4.0 to 5.5 times in the width direction at a temperature of 90 to 120°C, and then stretched to 180 to 230°C.
The laminated film of the present invention can be obtained by heat treatment at a temperature of .

For stretching the laminated film, either a sequential biaxial stretching method or a simultaneous biaxial stretching method can be applied.

The thus obtained laminated film is subjected to vapor deposition, coating, lamination, etc. on the polyester film surface, and then
The PPC layer is peeled off and used.

This peeling method is not particularly limited, but continuous peeling is easy if the laminated film is nipped between a set of nip rolls and peeled with the polyester film running along the surface of one of the rolls. Note that the above-mentioned vapor deposition etc. may be performed after peeling.

The laminated film of the present invention can be used in many applications such as dielectrics for capacitors and ribbons for thermal transfer.

[Measurement method] The measurement method and evaluation criteria for physical properties and the like used in the present invention are as follows.

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

■Friction coefficient Measured using a slip tester according to ASTM D-1894. All values are dynamic friction coefficients in a laminated state.

■ Film thickness Measurements were made 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 peel angle of 180 degrees for 200 mm.
The tension applied to the polyester film during peeling at a speed of mm/min was measured using a tensiometer. If this tension is T (g), the peeling force is T/W (g/
an).

■ Stability of peeling force The peeling force was recorded on a chart, and the variation with respect to the average value was determined and expressed according to the following criteria. At that time, ±0.05g
The peeling force is said to be stable within /cm.

○: Within ±0.05g/cm △: ±0. Within Ig/an The average diameter of the depressions caused by penetration into the surface of the polyolefin film and the distribution density of the depressions were determined from the photographs taken.

■ Peel off the pinhole number laminated film using a slitter and layer the peeled polyester film on top of the white film without wrinkles. Magic ink was sprayed over the entire surface of the 1M area, and the number of spots formed on the white film was defined as the number of pinholes.

◎: 0 pinholes 0: 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 Pressure increase rate: 50V/5ee (9) When a capacitor processable laminated film is subjected to vapor deposition, microslitting, and element winding, a case where misalignment occurs on the end face in any process is called winding misalignment, Capacitor workability was judged based on the degree of the change.

O: End face misalignment within 0.3 mm Δ: End face misalignment more than 0.3 mm and less than 1.0 mm ×: End face misalignment 1.0 mm or more In addition, when the slippage was poor and wrinkles were formed, it was rated as “×”.

[Effects of the Invention] By setting the structure of the laminated film of the present invention within the scope of the present invention, fluctuations in the peeling force of the ultra-thin polyester film layer are reduced, making it easier to process capacitors, and improving the durability of the polyester film. The resulting polyester laminated film has improved voltage and electrical properties and is suitable for use in capacitors.

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

PET: Intrinsic viscosity 0.75 dl/g Melting point: 260°C. Particle size 0゜ as outer grain 0.25% and 5μm wet silica and those with an average particle size of 1.5 μm are Contains 03%.

ppc: melting point 130°C. A propylene-ethylene random copolymer with an ethylene content of 6% by weight. Toshi silicone (SH3-46) as a mold release agent 0. Contains 03%.

These 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-shaped nozzle to form a three-layer structure of polyester/PPC/polyester. It was wound around a hot water drum at 65°C and cooled and solidified to form a three-layer laminated sheet.

After heating this sheet to 90°C, 3.
It was stretched 5 times and immediately cooled. Then again at 100℃
Stretched 4.5 times in the width direction, heat treated at 210°C for 6 seconds while maintaining tension, then 5%
The sample was relaxed, slowly cooled to room temperature, and rolled up. Thus, the thickness of the polyester layer on both sides is 0.
The thickness of the PPC layer at the center of 5μm is 5μm, and the total thickness is 6μ.
A laminated film of m was obtained.

When the PET layer is peeled off, the peeling force is 0.55±0°03g
/cm, which was very stable. The intrinsic viscosity of this ultra-thin polyester film was 0.72 dl/g, and the number of pinholes was 0/i, with no occurrence at all. The coefficient of friction is 0.8, and the dents in the peeled PPC layer have an average diameter of 1.5 μm and a density of 1,500 dents. It is ini,
Even in vapor deposition, microslit, and capacitor element windings, no winding misalignment occurs, and the dielectric breakdown voltage is 33.
It was good at 0V/μm. The results are shown in Table 1.

Example 2 Mold release agent for PPC layer (Toshi Silicone 5H-3746)
A film was formed in the same manner as in Example 1 except that the amount of addition was changed to 0.01%. Peeling force is 0.65±0. 10g/an
Slightly unstable, 3 pinholes, peeled PPC
The density of the depressions in the layer was 1600 and 10.1 mm.

Comparative Example 1 Completely the same as Example 1 except that the amount of wet silica with an average particle size of 0.5 μm added to the polyester layer was 0.5%, and the amount of wet silica with an average particle size of 1.5 μm was 0.075%. A film was formed. The peeling force was very unstable at 0.58±0.24g/an, there were 3 pinholes/a, the density of the dents in the peeled PPC layer was as high as 3300 10.1mm, and the dielectric breakdown voltage was 300v/μm. It was slightly worse than in Example 1.

The friction coefficient was 0.55, and winding misalignment occurred during vapor deposition.

The intrinsic viscosity of the PET film was 0.70 dl/g. The results are shown in Table 1.

Comparative Example 2 The intrinsic viscosity of the polyester chip of Example 1 was set to 0°53d.
A film was formed in the same manner as in Example 1, except that the ratio was 1/g. The peeling force was stable at 0.56±0.04g/an,
The number of pinholes in the peeled ultra-thin PET film is 50/d.
The dielectric breakdown voltage also decreased to 270 V/μm. The intrinsic viscosity of this film is 0.52 dl/g
Met.

Comparative Example 3 Same as Example 1 except that the amount of wet silica with an average particle size of 0.5 μm added to the polyester layer was 0.05%, and the amount of wet silica with an average particle size of 1°5 μm was 0.03%. A film was formed. Although the peeling force was very stable at 0.52±0.02 g, the friction coefficient was very high at 1.8, which caused problems in the winding and running properties of the film and caused damage to the film.

Number of pinholes: 5/d1 depression density: 400 10.1
It was mff1.

Claims (2)

[Claims] (1) In a laminated film formed by combining a polyester film on at least one side of a polyolefin film, 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. A laminated film characterized by: (2) The thickness of the polyester film is 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
The depressions caused by the protrusions on the surface of the polyester film on the peeled surface after peeling into the surface of the polyolefin film have an average diameter of 0.2 to 5 μm, and a distribution density of 500 to 5000 pieces/0.1 mm^2. The laminated film according to claim 1, characterized in that: