JPH0515537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to ultrathin polyester films, particularly
The present invention relates to a method for producing a polyester film having a thickness of 0.1 to 4 μm, more specifically, a thickness of 0.1 to 2 μm. Such a film is particularly suitable as a dielectric for a capacitor.

[Prior art and its drawbacks]

As a manufacturing method for ultra-thin polyester film,
A method of coextruding and laminating polyester and polyolefin and peeling the polyester film from the resulting laminated film is described in JP-A-57-176125, 58-5226, 58-136417, etc. It is well known. However, this conventional method has the disadvantage that the resulting ultra-thin polyester film has many insulation defects and is difficult to use for electrical purposes, such as as a dielectric for capacitors.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing an ultra-thin polyester film with few insulation defects as described above.

[Structure of the invention]

In order to achieve the above object, the present invention has the following configuration, that is, a method for manufacturing an ultra-thin polyester film by peeling a polyester film from a laminated film in which a polyolefin film and a polyester film are closely laminated.
A method for producing an ultra-thin polyester film, which is characterized in that a modified silicone oil into which at least one of an amino group, a carboxyl group, and a polyoxyalkylene group has been introduced in advance is contained in the polyolefin before close lamination. It is something to do.

The polyolef in film in the present invention is:
consisting of an olefin polymer or copolymer,
It refers to a non-oriented, uniaxially oriented or biaxially oriented film, and the thickness is not particularly limited, but it is usually 5.
~50μm. Typical examples of polyolefins include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, polybutene-1, poly-4-methyl-pentene-1, or copolymers and mixtures thereof. However, particularly preferred for the present invention is a propylene copolymer with a melting point of 100 to 150°C, and among these, a propylene copolymer with a melting point of
Most preferred is a propylene-ethylene copolymer at 100-140°C. This copolymer is made of propylene 80-98
% by weight and 2 to 20% by weight of ethylene, particularly preferably an ethylene content of 2.5 to 8.0% by weight.
% propylene-ethylene random copolymer. This copolymer may be a terpolymer in which a third copolymer component, such as butene-1, is further copolymerized to an extent less than the ethylene content. This copolymer also contains 50% by weight
Other polyolefins, such as polyethylene and polybutene-1, may be mixed within a range not exceeding . In addition, this copolymer contains various known additives, such as antioxidants, antistatic agents,
A lubricant, a plasticizer, an antiblocking agent, an ultraviolet absorber or a coloring pigment may be added.

The ultra-thin polyester film in the present invention is a uniaxially or biaxially oriented polyester film with a thickness of 0.1 to 4.0 μm, particularly 0.1 to 2.0 μm. Polyester is a polymer or copolymer in which 50 mol% or more, preferably 75 mol% or more of the polymer chains are connected by ester bonds, and includes polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene Bis(2-chlorophenoxy)ethane-4,
Typical examples include 4'-dicarboxylate or a condensation polymer of cyclohexanedimethanol and dicarboxylic acid, but polyethylene terephthalate is particularly preferred in the present invention. The polyethylene terephthalate mentioned here is one in which ethylene terephthalate units account for 90 mol% or more. In other words, within a range not exceeding 10 mol%,
other molecular units, such as ethylene isophthalate,
Butylene terephthalate, ethylene adipate,
Alkylene glycol, polyalkylene glycol, etc. may be copolymerized. This polyethylene terephthalate may contain known additives such as inorganic fine particles, coloring pigments, coloring inhibitors, and waxes.

Now, the laminated film formed by closely laminating a polyolefin film and a polyester film as used in the present invention is one in which a polyolefin film and a polyester film are overlapped with each other with substantially no voids, and is not particularly limited. The peeling force when peeling the polyester film is preferably from 0.1 to 10 g, more preferably from 0.1 to 1.0 g per 1 cm width of the polyester film.
(Measured at room temperature with a peel angle of 180 degrees and a peel speed of 200 mm/min). This laminated film may be a two-layer laminated film in which a polyester film is laminated on one side of a polyolefin film, or a three-layer laminated film in which a polyester film is laminated on both sides of a polyolefin film. Such a laminated film can be made by a so-called co-extrusion method in which polyolefin and polyester are melted together and laminated together and extruded into a sheet from a die.The co-extruded sheet is then uniaxially or biaxially By stretching in this direction, the laminated film of the present invention can be easily obtained.

Now, the gist of the present invention is to contain a modified silicone oil into which at least one group selected from among an amino group, a carboxyl group, and a polyoxyalkylene group has been introduced in advance into a polyolefin film of a laminated film consisting of a polyolefin and a polyester. It is a good idea to keep it. As is well known, common silicone oils, ie dimethylpolysiloxane and diphenylpolysiloxane, do not have amino groups, carboxyl groups or polyoxyalkylene groups. Even if such a common silicone oil is used for the purpose of the present invention, the effect of reducing insulation defects in ultra-thin polyester films, which is the object of the present invention, is small. This insulation defect occurs when a polyolefin film and a polyester film are peeled off, such as pinholes or creases, so this portion becomes an insulation defect. Further, even if insulation defects can be reduced to some extent, other problems such as metal deposition on a polyester film may reduce its adhesion, which is not preferable.

Now, the amino group, carboxyl group, or polyoxyalkylene group may be bonded in any form in the organopolysiloxane chain, but specific examples include the following chemical structures.

(1) Examples of amino groups (referred to as amino-modified silicone oil) (2) Examples of carboxyl groups (referred to as carboxyl-modified silicone oil) (3) Examples of polyoxyalkylene groups (referred to as polyoxyalkylene-modified silicone oil) However, Me: Methyl group _R1 : Hydrocarbon group having 0 to 20 carbon atoms _R2 : Hydrogen or hydrocarbon group having 1 to 20 carbon atoms x: An integer from 1 to 50 y: An integer from 2 to 50 n: 1 to 5 Of course, it is not necessary that all monomeric units in the organopolysiloxane chain have undergone such modification; the monomeric units that have undergone modification,
It may also be in the form of a copolymer with ordinary unmodified siloxane units (such as dimethylsiloxane units). The ratio of monomer units undergoing modification is generally referred to as the modification rate, and the modification rate of the modified silicone oil used in the present invention is preferably in the range of 0.3 to 99%, and preferably in the range of 45 to 99%. More preferred. Furthermore, among the various modified silicone oils described above, the one most suitable for the present invention is polyoxyalkylene modified silicone oil, and in particular,
Polyoxyethylene or polyoxypropylene modified materials are desirable. The viscosity of the modified silicone oil suitable for the present invention is preferably in the range of 40 to 40,000 centistokes, more preferably in the range of 100 to 10,000 centistokes, as measured at 25°C. Such modified silicone oil may be used by mixing it with ordinary dimethylpolysiloxane or diphenylpolysiloxane, but in that case, the ratio of modified silicone oil to the total amount should be 50% or more. is desirable.

The amount of modified silicone oil contained in the polyolefin film is preferably in the range of 0.01 to 1% based on the weight of the polyolef film.
The range of 0.05 to 0.5% is more preferable. If the content is less than this range, it becomes difficult to reduce insulation defects such as pinholes and creases in the ultra-thin polyester film, which is the objective of the present invention. On the other hand, if the content is higher than this range, certain silicone oils will transfer to the resulting polyester film, resulting in decreased adhesion of metal deposition and further compatibility with adhesives, printing inks, toners, etc. This is undesirable because it deteriorates adhesion.

Next, specific examples of the method of the present invention will be described, but of course the present invention is not limited thereto.

First, polyethylene terephthalate (abbreviated as PET) and propylene-ethylene copolymer (abbreviated as PEC) containing 0.1% of modified silicone oil are fed into separate extruders.
Melt extrusion at a temperature of 300℃, PET and
Combine the PEC layers to form PET/PEC/PET
Form into a sheet consisting of layers. This sheet is wrapped around a cooling drum with a surface temperature of 30°C to cool and solidify, creating a three-layer laminated sheet. This sheet is 80~
Heating to 130℃, each in the longitudinal direction and width direction.
Stretch 2.5 to 5 times. The stretching method may be either a so-called sequential biaxial stretching method in which the material is first stretched in the longitudinal direction and then in the width direction, or a so-called simultaneous biaxial stretching method in which the material is simultaneously stretched in the longitudinal direction and the width direction. It's okay. The stretched laminated film is heat treated at a temperature of 150 to 230°C for 1 to 10 seconds,
This is slowly cooled to room temperature to obtain a laminated film in which three layers of PET/PEC/PET are closely laminated. The thickness of each layer of this film is, for example, 0.5 μm for the PET layers on both sides and 15 μm for the PEC layer at the center. From this laminated film,
By continuously peeling off the surface PET film, an extremely thin PET film with a thickness of, for example, 0.5 μm can be obtained. Also, another method is
A metal such as aluminum or zinc may be deposited to a thickness of 100 to 2000 Å on the PET surface of the laminated film by a conventional method, and then the deposited PET layer may be peeled off. In addition, the vapor-deposited laminated film was
The deposited PET layer may be peeled off after being microslit into a tape with a width of ~20 mm.
Make two sets of this tape-shaped vapor-deposited PET film,
Capacitor elements can also be made by rolling the two layers together, peeling off the deposited PET layers from each layer.
By attaching terminals to both ends of this element using a method such as metal spraying, a foil-wound capacitor can be created.

[Effects of the present invention]

The present invention provides an ultra-thin polyester film obtained by containing a specific modified silicone oil in the polyolefin film of a laminated film in which a polyolefin film and a polyester film are closely laminated. This has the effect of significantly reducing the number of insulation defects. If insulation defects are reduced, the quality of capacitor elements made using this polyester film as a dielectric will be improved, and the quality of capacitors obtained from this element will also be improved. Useful for polyester films.

[Method of measuring physical properties]

The methods for measuring physical properties etc. used in the present invention are as follows.

(1) Film thickness Films thicker than 1 μm were measured using a dial gauge. For films of 1 μm or less, stick the film on a glass support without wrinkles, run it on a stylus-type surface roughness meter, and measure the boundary between the area where the film is absent and the area where the film is present. The difference in level was measured and this was taken as the film thickness.

(2) Melting point Using DSC, the temperature was raised at a rate of 20°C/min, and the melting point was defined as the temperature corresponding to the top of the endothermic peak accompanying melting (sample amount: 10 mg).

In addition, when two or more melting point peaks appeared, the temperature at the top of the higher peak was taken as the melting point.

(3) Number of insulation defects An ultra-thin polyester film with aluminum deposited on one side is spread out on a copper plate without wrinkles. At this time, the polyester film is sandwiched between copper and aluminum with the vapor deposition surface facing upward. Then, using copper and aluminum as electrodes, the film thickness is
Apply a DC voltage of 100V per 1μm. Then,
Since current flows between the electrodes and the vapor-deposited surface partially disappears in the insulation defect area, the number of insulation defects per unit area of the film can be determined using this method.
Here, the number of insulation defects is expressed as (pieces/m ² ). The smaller the number, the better the film for capacitors.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on Examples. Of course, this example does not restrict the content of the present invention.

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

PET: Polyethylene terephthalate with a melting point of 259°C and an intrinsic viscosity of 0.62 (dl/g). Average particle size 0.03μ
Contains 0.1% by weight of synthetic silica fine particles and 0.1% by weight of sodium montanate.

PEC: Propylene with 5.5% ethylene content by weight
Ethylene random copolymer. Melting point: 125℃.
Contains 0.15% by weight of polyoxyethylene modified silicone oil (modification rate 80%, viscosity 1800 centistokes at 25°C).

These two types of raw materials are fed to separate extruders.
Melt extrusion is carried out at 280°C, and each melt is combined in a T-shaped nozzle to form a three-layer structure of PET/PEC/PET, which is then wrapped around a cooling drum with a surface temperature of 25°C and cooled and solidified. , a three-layer laminated sheet. The thickness of the PET layers on both sides was 5 μm each, and the thickness of the PEC layer in the center was 150 μm. After heating this sheet to 90℃, it was stretched 3.1 times in the longitudinal direction,
It was immediately cooled to 30°C. Next, the film was heated again to 100°C, stretched 3.2 times in the width direction, and while maintaining the tension, was heat treated at 200°C for 6 seconds, slowly cooled, cooled to room temperature, and wound up. The thickness of the PET layers on both sides of the obtained film is different from each other.
The thickness of the PEC layer was 0.5 μm, and the thickness of the central PEC layer was 15 μm.

Aluminum is deposited on the PET layer surfaces on both sides of this laminated film by a conventional method, and then the deposited PET layer is peeled off to form a 0.5 μm thick deposit.
Obtained PET film. In addition, the peeling force at this time is
It was 0.2g/cm. When the number of insulation defects in this film was measured, it was found to be extremely small at 6 defects/m ² , indicating that it is suitable as a film for capacitors.

Comparative Example 1 A 0.5 μm vapor-deposited PET film was produced by removing the polyoxyethylene-modified silicone oil from the PEC layer of Example 1 and keeping all other conditions the same. This film had a fairly large number of insulation defects, 42/m ² , and was not very good as a capacitor film.

Example 2 Instead of the polyoxyethylene-modified silicone oil of Example 1, amino-modified silicone oil (modification rate 75%, viscosity 1200 centistokes at 25°C) was used.
Using the same method as in Example 1, a vapor-deposited PET film with a thickness of 0.5 μm was produced.

When we measured the number of insulation defects in the film, we found that
7 pieces/m ² , showing good results similar to Example 1.

Claims (1)

[Claims] 1 From a laminated film formed by closely laminating a polyolefin film and a polyester film,
In a method for manufacturing an ultra-thin polyester film by peeling a polyester film, a modified silicone oil into which at least one group among an amino group, a carboxyl group, and a polyoxyalkylene group has been introduced in advance is contained in the polyolefin before adhesive lamination. A method for producing an ultra-thin polyester film characterized by the following.