JPH0624821B2 - Laminated film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated film. More specifically, the present invention relates to a peelable laminated film in which an ultrathin polyethylene terephthalate film suitable for a capacitor dielectric, a stencil printing base paper or a typewriter ribbon base film is laminated by coextrusion.

[Prior art]

In recent years, as electric devices have become smaller and lighter, applications such as capacitors have become smaller and smaller, and thinner films have been required. As such an ultra-thin film, for example, Japanese Patent Laid-Open No.
8-5226, 58-132520, 58-13641
7, 57-176125, 52-37982 and the like, different kinds of polymers are stretched in a laminated state,
It is known that after forming a laminated film, one of them is peeled off and used as an ultrathin film.

[Problems to be solved by the invention]

Such a conventional laminated film is liable to be broken and pinholes are easily formed at the time of peeling. Further, the obtained ultrathin film had a problem that the water vapor transmission rate was larger than that of a normal film having a thickness of about 10 μm and the dielectric breakdown voltage was extremely small.

It is an object of the present invention to provide a laminated film having less of the above-mentioned drawbacks, that is, having a layer of an ultrathin polyethylene terephthalate film having a small water vapor transmission rate and a large dielectric breakdown voltage, and having good peelability. It is a thing.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention has the following constitution: a polyethylene terephthalate layer containing 0.05 to 1% by weight of a higher fatty acid wax is laminated on at least one surface of a propylene copolymer layer by coextrusion, The polyethylene terephthalate layer, which has been stretched,
The thickness is 0.2 to 2.0 μm, and the water vapor transmission rate is 4.0 to 4.0.
The laminated film has a releasability of 6.0 g / m ² · 24 hr / 0.1 mm.

The propylene copolymer (hereinafter abbreviated as PPC) layer in the present invention is a layer having a melting point of 100 to 150 ° C. and is not particularly limited as PPC, but propylene 80 to 97 mol% and other than propylene Olefin 3
Polymers consisting of copolymers with .about.20 mol% are preferred.
Specific examples thereof include a propylene / ethylene copolymer, a propylene / butene copolymer, a propylene / ethylene / butene terpolymer or a mixture thereof. The copolymerization method is preferably a random copolymer, but a block copolymer can also be used depending on the degree of block. In addition, it may be a mixture of a propylene copolymer and another polyolefin (for example, polyethylene, polybutene, etc.).

The intrinsic viscosity of PPC is preferably in the range of 1.0 to 2.0 d / g. Within this range, unevenness in the film thickness is reduced, which is preferable.

In addition, known additives, for example, non-particulate lubricants, inorganic fine particles, coloring pigments, waxes and the like may be added to the PPC.

The thickness of the PPC layer is preferably in the range of 5 to 30 μm.

Polyethylene terephthalate (hereinafter, P
The layer (abbreviated as ET) is a layer of a polymer in which 90 mol% or more of the molecular constitution is composed of ethylene terephthalate units, and the melting point of the polymer of the layer is 250 ° C. or more, preferably 2
It is preferably 55 ° C or higher. Of course, the copolymerized known molecular units, for example, ethylene isophthalate, butylene terephthalate, ethylene adipate, ethylene sebacate, polyethylene glycol, etc., may also be used as long as the ethylene terephthalate unit does not fall below 90 mol%. It is included in PET referred to in.

The thickness of the PET layer is 0.2 to 2.0 μm, preferably 0.2 to 1.5 μm. If the thickness is less than 0.2 μm, there is a problem of breaking during film formation, which is not preferable. When the thickness is 2.0 μm or more, preferably 1.5 μm or more, the workability of the film alone is good and the dielectric breakdown voltage can be kept large. Therefore, it is necessary to form the laminated film as in the present invention. There is no.

Further, the PET layer of the present invention needs to contain a higher fatty acid wax. The higher fatty acid wax contained is a fatty acid ester compound whose main component is a higher fatty acid having 17 to 33 carbon atoms and a polyhydric alcohol having 17 to 33 carbon atoms, and specific examples include:
Wax such as shellac wax, wax, insect wax, montan wax, wool wax, carnauba wax, cauliderilla wax, cotton wax, and synthetic wax, as well as replacing some or all of the fatty acid esters of these waxes with other alcohol components, or sodium, A modified product obtained by modifying a metal salt such as an alkali metal such as potassium or an alkaline earth metal such as calcium, magnesium and barium, and having a hydrocarbon compound content of 50% by weight or less and being solid at room temperature. Particularly desirable among these are carnauba wax, montan wax, synthetic waxes, and modifications thereof. Here, the main component means that the total amount of the fatty acid ester compound composed of a higher fatty acid having 17 to 33 carbon atoms and a polyhydric alcohol having 17 to 33 carbon atoms is 500% by weight or more.

Here, the number of carbon atoms in the higher fatty acid or polyhydric alcohol is 17
If it is less than the above, bleeding out of the higher fatty acid wax to the surface of the film is severe, troubles such as machine stains may occur in the film forming process, and vapor deposition on the PET layer or adhesiveness of the anchor coat may be significantly deteriorated. If the number of carbon atoms exceeds 33, holes are likely to be formed in the PET layer, which causes film breakage. The content of the higher fatty acid wax is PET
It should be 0.05 to 1% by weight, preferably 0.11 to 0.8% by weight, based on the layer. When the content is less than 0.05% by weight, the number of pinholes in the peeled ultrathin PET film increases, and the dielectric breakdown voltage and the water vapor transmission rate deteriorate. If the content exceeds 1% by weight, the thickness unevenness of the PET layer becomes severe and the film breaks during peeling.

Furthermore, the PET layer of the present invention has a water vapor transmission rate of 4.0 to 4.0.
It needs to be 6.0 g / m ² · 24 hr / 0.1 mm. A water vapor transmission rate of less than 4.0 is also preferable, but P
Achieving ET is difficult. If the water vapor transmission rate exceeds 6.0, the number of pinholes increases and the dielectric breakdown voltage decreases.

In addition, it is preferable that fine particles are added to the PET layer, and the particles have a number average protrusion diameter of 1.
Those having 5 to 4 μm are preferable, and 1.8 to 2.8 μm
Is more preferable. As the fine particles, inorganic fine particles, for example, dry silica, wet silica, zeolite, calcium carbonate, calcium phosphate, kaolin, kaolinite, clay, talc, titanium oxide, alumina, zirconia, aluminum hydroxide and the like, the addition amount thereof is preferable. 0.0
It is 1 to 1.0% by weight. It is preferable to add fine particles in this way because the effect of the higher fatty acid wax can be synergistically enhanced.

The laminated film of the present invention has the above-mentioned PET layer and PPC layer laminated by coextrusion, and the laminated constitution is not particularly limited, but it is two layers of PET / PPC, PET / PPC / PET.
3 layers, or PET / PPC / PET / PPC / P
Five layers of ET are preferred.

The ratio A / B between the thickness A of the PET layer 1 layer and the thickness of the PPC layer 1 layer (the thickest layer when there are multiple layers) B is 0.0.
1 to 0.2 is preferable. If it deviates from this range, it tends to be difficult to form a film. Further, the laminated film needs to be imparted with molecular orientation by stretching, and it is preferable to stretch biaxially simultaneously or sequentially.

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

PET chips containing a specific amount of higher fatty acid wax and PPC chips are supplied to different extruders,
An unstretched laminated sheet is produced by the coextrusion film forming method.

3.0 to 4.0 times in the longitudinal direction at 80 to 100 ° C, and then 4.0 to 5.5 times in the width direction at 90 to 120 ° C.
Then, the laminated film of the present invention can be obtained by heat treatment at 180 to 220 ° C.

Known methods can be applied to the coextrusion method, stretching method, heat treatment method and the like.

The laminated film thus obtained is printed, laminated, coated or vapor-deposited on the PET surface, and then PP
The C layer is peeled off and used. This peeling method is not particularly limited, but continuous peeling is easy when the laminated film is nipped between a pair of nip rolls and the PET film is peeled along the roll surface on one side. The above-mentioned printing may be performed after peeling.

The laminated film of the present invention can be used in many applications such as a capacitor derivative, a stencil printing base paper or a typewriter base film.

[Action]

According to the present invention, the laminated film contains the higher fatty acid wax in a specific amount in the PET layer, so that the peeling between the PET layer and the PPC layer is significantly improved, pinholes are reduced, and P
Even if particles are added to the ET layer, the affinity with the particles is improved and the voids are considered to disappear. Thereby,
It is considered that the dielectric breakdown voltage and water vapor permeability were improved.

[Method of measuring physical properties]

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

(1) Film thickness Films thicker than 2 μm were measured with a dial gauge. The film of 2 μm or less is on a glass support,
It was applied in a wrinkle-free state, and this was applied to a stylus-type surface roughness meter to measure the level difference between the place where there is no film and the place where the film exists, and this was taken as the film thickness.

(2) Wax content Films with various amounts of wax added are prepared, and H-NMR spectrum is measured at a resonance frequency of 400 MHz to prepare a calibration curve. PE from the relative comparison with the film to be measured
The wax content of the T layer was determined.

(3) Number average projection diameter Aluminum vapor deposition on PET film (thickness 0.1 μm)
Then, the number of surface protrusions of the film and each area of the protrusions were quantitatively measured using an optical microscope (32 × 8 times) and an analyzer (50 fields of view). The area of each protrusion was converted to the equivalent circle diameter, and the average value of the equivalent circle diameters was calculated to obtain the number average protrusion diameter.

(4) Water Vapor Transmission Rate A water vapor transmission rate (g / m ² · 24 hr / 0.1 mm) was obtained by making a sample cup by the method of JIS Z0208.

(5) Number of pinholes An ultra-thin PET film with aluminum evaporated on one side
Spread it on a copper plate without wrinkles. At this time, the PET film is sandwiched between copper and aluminum with the vapor deposition surface facing upward. And
Copper and aluminum are used as electrodes, and a direct current voltage of 100 V per 0.5 μm of film thickness is applied for 5 seconds therebetween. Then, in the pinhole portion, a current flows between the electrodes, and the vapor deposition surface partially disappears. Therefore, the number of pinholes per unit area of the film can be known by this method. Here, the number of pinholes is displayed.

(6) Dielectric breakdown strength (piece / 100 cm ² ) A DC voltage was applied to a 10 cm square film to measure the voltage at which dielectric breakdown occurred. The value (V / μm) obtained by dividing the dielectric breakdown voltage by the film thickness was expressed as the dielectric breakdown strength. The boosting rate was 50 V / sec.

〔Example〕

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

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

PET: Intrinsic viscosity 0.62 d / g. Melting point 259 [deg.] C. It contains 0.5% by weight of carnauba wax (the content in the film was adjusted to this value) and 0.5% by weight of dry silica.

PPC: Intrinsic viscosity 1.65 d / g. Melting point 120 [deg.] C. A propylene / ethylene random copolymer having an ethylene content of 6% by weight.

The two raw materials are fed to separate extruders to obtain 280
Melt extruded at ℃, let the melts merge in a T-shaped die to form a three-layer structure of PET / PPC / PET, wrap it around a cooling drum at 25 ° C., and cool and solidify it.
It was a three-layer laminated sheet. The thickness of the PET layer on each side is 8 each
The thickness of the central PPC layer was 230 μm.

This sheet was heated to 90 ° C., stretched 3.4 times in the longitudinal direction, and immediately cooled to 30 ° C. Then again 1
It was heated to 00 ° C., stretched 4.6 times in the width direction, heat-treated at a temperature of 200 ° C. for 6 seconds while keeping the tension as it was, gradually cooled, cooled to room temperature, and wound. The obtained film had a PET layer thickness of 0.5 μm on each side,
A laminated film having a thickness of the central PPC layer of 15 μm was obtained.

When the PET layer was peeled off, the peelability was good.

When the number of pinholes in the peeled ultra-thin PET film was measured, it was as small as 10/100 cm ^2, and the number average projection diameter was 2.0.
was μm. The water vapor transmission rate is 5.0 g / m ² ·
24 hr / 0.1mm, dielectric breakdown strength is 320V /
It was as good as μm.

Comparative Example 1 The carnauba wax added to the PET raw material of Example 1 was 1.
5% by weight and 0.5% by weight of dry silica were formed in the same manner. The stretchability was poor, and when the film was stretched horizontally, perforations of the film frequently occurred, and a satisfactory sample could not be obtained.

Comparative Example 2 Carnauba wax added to the PET raw material of Example 1 was added.
A film was formed in the same manner with 01% and 0.5% of dry silica. The resulting film had a PET layer thickness of 0.5 μm on each side and a central PPC layer thickness of 15 μm. 5 when the PET layer is peeled off and the number of pinholes is measured
The number was 0/100 cm ^2, which was more than in the examples. The number average protrusion diameter was 2.5 μm. The water vapor transmission rate of this ultra-thin PET film is 6.5 g / m ² · 24 hr / 0.1 mm, and the dielectric breakdown voltage is 270 V / μm, which is poor.

Comparative Example 3 Carnauba wax in the PET raw material of Example 1 was omitted, and 0.5% of only dry silica was added to form a film in the same manner. In the obtained film, the thickness of the PET layers on both sides was 0.5 μm, and the thickness of the central PPC layer was 15 μm. When the PET layer is peeled off and the number of pinholes is measured, 66
The number was 100 pieces / 100 cm ^2, which was larger than that in the example. The number average protrusion diameter was 2.6 μm. The water vapor transmission rate of this ultra-thin PET film is 6.2 g / m ² · 24 hr / 0.1 mm, and the dielectric breakdown voltage is 250 V / μm, which is considerably poor.

〔The invention's effect〕

In the laminated film of the present invention, since the PET layer contains an appropriate amount of the higher fatty acid wax, the releasability between the PET layer and the PPC layer was improved and pinholes were reduced. As its effect, the water vapor permeability and the dielectric breakdown strength are improved.

Claims (1)

[Claims] 1. A polyethylene terephthalate layer containing 0.05 to 1% by weight of a higher fatty acid wax on at least one side of a propylene copolymer layer, which is laminated by coextrusion and then stretched, and the polyethylene terephthalate layer. Is a releasable laminated film having a thickness of 0.2 to 2.0 μm and a water vapor transmission rate of 4.0 to 6.0 g / m ² · 24 hr / 0.1 mm.