JPH07186332A - Insulating film - Google Patents

Abstract

PURPOSE:To provide an insulating film excellent in electric characteristics even when the film is made thin. CONSTITUTION:An insulating film is composed of a plastic film having a ceramic membrane provided to at least the single surface thereof. As the ceramic membrane, a membrane composed of Al2O3 or ZrO2-SiO2 is designated. The ceramic membrane is formed by various vacuum vapor deposition methods, a sputtering method or a CVD method. This film is good in electric characteristics and heat resistance, excellent in running properties and abrasion resistance and good in handling characteristics regardless of the thickness of the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating film which is used as a printed wiring board film, a film for capacitors, etc., and which requires electrical insulation.

[0002]

2. Description of the Related Art At present, there is a strong demand for thinner dielectrics from the viewpoint of miniaturization of capacitors and increase of capacitance. In addition, in order to improve the production speed of capacitors and the like, the temperature applied to the dielectric is high, and the demand for heat resistance is becoming severe. Under such circumstances, the plastic film is excellent in heat resistance and electric characteristics, and is expected to be developed for use as an insulating film for capacitors.

[0003]

However, if the plastic film is simply thinned in order to downsize the capacitor and increase the electrostatic capacity, the film thickness is reduced even if the withstand voltage per unit film thickness is constant. The withstand voltage is reduced accordingly. Needless to say, the withstand voltage is the most basic property as an insulator in electric parts, and it is very inconvenient if the withstand voltage is reduced. Further, if the plastic film is simply thinned, the handling property at the time of manufacturing and processing of the film becomes poor at the same time. When a lubricant is added to improve the handling property, the polymer is brittle, so that voids are generated around the lubricant. As a result, the withstand voltage characteristic and the life characteristic of the electric characteristics are likely to deteriorate. Therefore, as a film having a large withstand voltage, a film having a sufficiently large film thickness is required.

An object of the present invention is to solve the above problems of the prior art and to provide an insulating film having excellent electric characteristics even when the film thickness is reduced.

[0005]

The insulating film of the present invention comprises a plastic film having a ceramic thin film on at least one surface.

The plastic film in the present invention is obtained by melt-extruding an organic polymer, stretching it in the longitudinal direction, the width direction, or the longitudinal direction and the width direction, if necessary, and then cooling and heat-setting. It is a film that can be used. Examples of the organic polymer include polyethylene terephthalate, polycarbonate, polypropylene, polystyrene, polyethylene, polyphenylene sulfide,
Syndiotactic polystyrene, polyethylene-2,
6-naphthalate, nylon 6, nylon 4, nylon 66, nylon 12, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamide, polyamideimide, polyimide, polyetherimide, polysulfone, polyphenylene oxide, etc. To be Further, these organic polymers may be copolymerized or blended with a small amount of another organic polymer.

The film of the present invention can be obtained by a known method, for example, a sequential method of sequentially carrying out longitudinal stretching and transverse stretching, as well as transverse / longitudinal / longitudinal stretching method, longitudinal / lateral / longitudinal stretching method, longitudinal / longitudinal / lateral stretching. A stretching direction such as a method can be adopted, and these methods are selected according to various properties such as required strength and dimensional stability. In addition, in order to improve the adhesive properties of the vapor deposition layer,
An adhesive layer may be provided by in-line coating or off-line coating, corona discharge treatment, glow discharge treatment, and other surface roughening treatments.

Further, known additives such as an ultraviolet absorber, an antistatic agent, a plasticizer, a lubricant and a coloring agent may be added to the above organic polymer. The lubricant particles are not particularly limited, but silica,
Metal oxides such as titanium dioxide, talc, kaolinite,
Examples are particles that are inert to organic polymers, such as particles made of metal salts such as calcium carbonate, calcium phosphate, barium sulfate, or organic polymers. Any one of these lubricants may be used alone, or two or more thereof may be used in combination, but the average particle size of the lubricant used is 0.
It is preferably from 0.1 to 2.0 μm, particularly preferably from 0.05 to 1.5 μm, and the degree of variation in particle diameter (ratio between standard deviation and average particle diameter) is preferably 25% or less. The amount of lubricant added is 0.005 to 2.0 with respect to 100% by weight of the organic polymer.
It is preferable to set it as a weight%, and especially 0.1-1.0 weight% is preferable. In addition, it is preferable that the shape of the lubricant particles include one or more kinds having a shape factor of 60% or more. This area shape factor is calculated by the following equation. Area shape factor = (projected cross-sectional area of particle / area of circle circumscribing particle) × 100 (%)

The polystyrene-based polymer used in the present invention may contain, if necessary, a known antioxidant, antistatic agent or the like in an appropriate amount. The blending amount is
10% by weight or less is desirable with respect to 100% by weight of the polystyrene polymer. If it exceeds 10% by weight, breakage easily occurs during stretching, resulting in poor production stability.

The thickness of the plastic film of the present invention is preferably in the range of 1 to 50 μm, more preferably 1 to 6 μm. Further, particularly preferably 1 to
It is in the range of 3 μm.

In the present invention, various vacuum vapor deposition methods, sputtering methods, CVD methods and the like are used as the method for producing the ceramic thin film. Of these, vacuum vapor deposition is preferable because it provides the highest deposition rate, but the present invention is not limited to this. Regarding the vacuum vapor deposition method, the heating method may be a single electron gun (hereinafter referred to as an EB gun) or a plurality of heating methods, or another heating method or a combination thereof. Other heating methods referred to here include resistance heating, high frequency induction heating, laser beam heating, and the like.
It is not particularly limited to this. Further, regarding the vacuum vapor deposition method and the sputtering method, the present invention is also applied to reactive vapor deposition and sputtering in which oxygen, nitrogen, water vapor, etc. are introduced as a reactive gas, or ozone, ion assist, etc. are used. it can. Also, add bias to the substrate,
The deposition conditions may be changed, such as raising or cooling the substrate temperature. The same applies to the sputtering method and the CVD method.

In the present invention, the thickness of the ceramic thin film is, for example, 1 to 0.005 μm, and 0.5 to 0.0.
1 μm is preferable.

The ceramic in the present invention, as generally defined, refers to a solid material composed of an inorganic non-metallic substance, including metal oxides, nitrides and carbides,
It also includes oxides, nitrides and carbides of semi-metals. Also included are compounds and mixtures of these oxides, nitrides and carbides. The ceramic used in the present invention is an insulator.

The above-mentioned metal is a single metal or an alloy or mixture of two or more kinds of metals, and examples of the metal include F.
e, Co, V, Pt, Ti, Mo, Ta, Nb, Mg,
Examples thereof include, but are not limited to, Ca, Al, Sn, Sb, and Y. Moreover, as an example of a semimetal,
Si is mentioned.

The above-mentioned oxide is a compound of a metal or a metalloid with oxygen. In the present invention, these oxides are preferable as a thin film material to be vapor-deposited on a plastic. These oxides include simple oxides and composite oxides of two or more kinds of metals. The simple oxide composition refers to an oxide composed of one kind of metal and oxygen. For example, Al
O ₂ , Al ₂ O ₃ , CeO ₂ , SiO, SiO ₂ , Si
Ox, Y ₂ O ₃ , HfO ₂ , Ta ₂ O ₅ , MgO, Ti
Examples thereof include O ₂ , ZrO ₂ , Nd ₂ O ₃ , PbO, ThO _{2 and the} like, but are not particularly limited thereto. Impurities may be included in the simple oxide composition within a range (about 3%) that does not impair the purpose. A complex oxide is a mixture or compound of two or more kinds of oxides, and for example,
_{Al 2 O 3 -SiO 2, SiO} -SiO 2, Al 2 O 3
_{-MgO-SiO 2, BaTi 2 O} (BaO-Ti
_{O 2), SrTiO 3, PbTiO} 3, ZnO-Al 2
_{O 3, ZnO-BiO 3,} TiO 2 -SiO 2, BaO
_{-Al 2 O 3 -SiO 2, Y} 2 O 3 -ZrO 2, ZrO
Complex oxide film such as ₂ -SiO _2, and the like, but not particularly limited to this.

The above-mentioned nitride is a compound in which a metal is combined with nitrogen. For example, TiN, BN, AlN, Si.
Examples thereof include ₃ N ₄ , HfN, ZrN, TaN, VN, NbN, etc., but are not particularly limited thereto.

The above-mentioned carbide is a compound of a metal and carbon, such as TiC, HfC, ZrC, SiC,
_{B 4 C, BXC, W 2} C, Cr 7 C 3 Cr 3 C 2, Ta
C, VC, NbC and the like are mentioned, but not limited thereto.

The compounds and mixtures of the above oxides, nitrides and carbides are, for example, SiAlON,
Si-ON, oxynitride such as SiYAlON, TiN-
A mixture of SiO and a nitride such as SiO, a mixture of SiN and carbides such as SiN-SiC, Y ₂ O ₃ -AlN etc. Y ₂
A mixture of O ₃ and nitride, Ta ₂ O ₅ —ZrN, etc. Ta ₂
A mixture of O ₅ and nitride, ZrO ₂ such as ZrO ₂ —SiN
However, the mixture is not limited to this.

Further, at least one surface of the film of the present invention preferably has a three-dimensional surface roughness SΔa within a range of 0.004 to 0.04. If SΔa is less than 0.004, handling characteristics and running performance will be poor, and 0.04
If it exceeds, the withstand voltage characteristics and life characteristics are likely to be poor.

Further, the air bleeding speed of the film of the present invention is preferably 900 seconds or less, more preferably 700 seconds or less. That is, by setting the air bleeding speed to 900 seconds or less, and more preferably 700 seconds or less, the handling property becomes good regardless of the thickness and strength of the film even during high-speed work. On the other hand, when the air bleeding speed exceeds 900 seconds, the handling characteristics at the time of high-speed work become poor, and for example, when the film is wound into a roll at high speed, air is entrapped between the film and the take-up roll to form wrinkles. It is apt to occur and the winding shape becomes poor, or the film is meandered in the width direction due to the lubricating effect of the air layer in which the film is wound, and the end face of the roll is uneven.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

First, the evaluation method of the film is shown below.

(1) Thermal Shrinkage Rate at 200 ° C. The shrinkage rate of the film in an atmosphere of 200 ° C. for 30 minutes without tension was determined.

(2) Three-dimensional surface roughness SΔa Stylus-type three-dimensional surface roughness meter (SE-3A
K, manufactured by Kosaka Laboratory Ltd.) using a needle radius of 2μ
Under conditions of m and load of 30 mg, the cutoff value is 0.25 mm in the longitudinal direction of the film, the measurement length is 1 mm, and the height of each point is divided into 500 points by a three-dimensional roughness analyzer. (SPA-11).
The same operation as this was continuously performed 150 times at intervals of 2 μm in the width direction of the film, that is, 0.3 m in the width direction of the film.
The data was taken into the analyzer for m. Next, SΔa was obtained using an analyzer.

(3) Air Venting Rate The measuring device shown in FIG. 1 was used. That is, a circular hole (1a) is provided on the upper surface of the base (1), and a glass flat plate (2) with a diameter of 70 mm is fixed in the hole (1a), and the outer circumference of the glass flat plate (2) and the hole wall are fixed.
(1b) to form a groove, further provided with a ring-shaped groove hole (1c) surrounding the hole (1b), the groove hole (1c) is the glass plate
The suction hole of the vacuum pump (4) is connected to the groove hole (1c) through the pipe (3) so as to communicate with the groove on the outer circumference of (2). And the base
A film sample (5) sized to cover the glass flat plate (2) is placed on the upper surface of (1), and the periphery of the film sample (1) is attached with adhesive tape (6).
After fixing the glass plate in a hermetically sealed manner, drive the vacuum pump (4), and the interference fringes will appear on the outer periphery of the glass plate (2).
Measure the time (seconds) until the interference fringes spread over the entire surface of (2) and stop its movement, and use this time (second) as the air bleeding speed.

(4) Handling characteristics of film When slitting a wide slit roll at a high speed and rewinding it into a small roll, there is no problem of roll misalignment, wrinkles, valves, etc. Whether or not it was evaluated on a 4-point scale according to the following ranking. 1st grade: It is extremely difficult to obtain a problem-free slit roll 2nd grade: A low-problem slit roll can be obtained 3rd grade: A medium-speed slit roll can be obtained 4th grade: A high-speed nonproblem slit Roll is obtained

(5) Runnability / Abrasion Resistance of Film When the film is slit into a narrow width and rubbed against a metal roll to run, the tension of the tape after passing through the guide roll against a constant supply tension, The occurrence of scratches and the amount of white powder adhered to the roll were evaluated on a scale of 5 according to the following ranking. Runnability evaluation 1st class; high tension, many scratches 2nd class: tension, slightly large, scratches fairly high 3rd class: medium tension, slight scratches 4th class: tension small, almost no scratches 5th class: small tension, no scratches here If the results obtained for tension and scratches are of different ranks, the worse rank is used. Abrasion resistance evaluation 1st grade: White powder generation is extremely high 2nd grade: White powder generation is high 3rd grade: White powder generation is slight 4th grade: White powder generation is almost zero 5th grade: White powder generation is not

(6) Average particle size Lubricant particles were observed with a Hitachi S-510 scanning electron microscope, and a photograph was taken of an enlarged copy.
The outer diameter of the lubricant was traced, and 200 particles were arbitrarily painted in black. This image is made by Nicolet Co., Ltd. Luzex 50
The Feret diameter in the horizontal direction of each particle was measured using a 0 type image analyzer, and the average value was taken as the average particle diameter.
The degree of variation in particle size was calculated by the following formula. Variability = (standard deviation of particle diameter / average particle diameter) × 10
0 (%)

(7) Area shape factor 20 particles are arbitrarily selected from the trace image used for measuring the average particle diameter, and the projected area of each particle is calculated by using the image analysis device used in the above (6). It was measured. Further, the area of the circle circumscribing these particles was calculated and calculated by the following formula. Area shape factor = (projected cross-sectional area of particle / area of circle circumscribing the sink) × 100 (%)

(8) Withstand voltage The test was carried out according to JIS C-2318. Using a 10 KV DC withstanding voltage tester, the voltage when the film was broken and short-circuited was read at a pressure rising rate of 100 V / sec in an atmosphere of 23 ° C. and 50% RH.

(9) Life characteristics Aluminum was vapor-deposited on a film sample using a vacuum vapor deposition machine to prepare a capacitor having a capacity of 0.1 μF, and a DC voltage of 300 V was applied between both terminals of this capacitor,
Within 2000 hours at 150 ° C., the residual ratio of 100 elements having a function as a capacitor without short circuit was measured.

[Example 1-a, b, c] Measured value 1 of thickness
On a PET film (manufactured by Toyobo Co., Ltd.), which is 2.3 μm, 6.1 μm, and 3.2 μm (Examples 1-a, 1-b, and 1-c, respectively), a ZrO ₂ —SiO ₂ -based thin film is formed. Was deposited. The thin film was formed by electron beam evaporation. That is, as shown in FIG.
A thin film was formed by an electron beam vapor deposition method using ZrO ₂ and SiO ₂ (purity 99.9%) having a particle size of about mm. As the vapor deposition material, two hearths were used without mixing. Using one EB gun as a heating source, ZrO ₂ and S
Each of the iO ₂ is heated in a time-division manner to obtain ZrO ₂ —SiO _{2.
A two-} system mixed film was prepared. EB gun acceleration voltage 6k at that time
V, emission current 200mA, ZrO ₂ and S
The heating ratio to iO ₂ was 48:12. The ultimate vacuum is 2.3 × 10 ^-5 Torr, and the vacuum during vapor deposition is 2.4 × 1.
It was 0 ⁻⁴ Torr. Substrate holder is water cooled to 10 ° C
And The vapor deposition time is 20 seconds. The resulting thin film has a thickness of 0.
It was 1 μm. The ZrO ₂ ratio in the thin film is 10 wt.
%Met.

[Example 2-a, b, c] Example 1-a,
An Al ₂ O ₃ -based thin film was deposited on a PET film having the same three thicknesses as used in b and c. The thin film was formed by electron beam evaporation. As a vapor deposition source, particulate Al ₂ O ₃ (purity 99.9%) having a size of about 1 to 3 mm was used. The vapor deposition material was placed in one hearth. An Al ₂ O ₃ based film was formed using one EB gun as a heating source. At that time, EB gun acceleration voltage 6kV, emission current 20
It was set to 0 mA. The other conditions are the same as in Example 1. The thickness of the obtained thin film was 0.1 μm.

[Comparative Example 1-a, b, c] Example 1-a,
The PET film itself had the same three kinds of thickness as those used in b and c, and a thin film was not attached. The film characteristics in this case were examined as Comparative Example 1.

[Comparative Example 2-a, b, c] Al vapor deposited thicknesses of 12.3, 6.1 and 3.2 μm (Comparative Example 2-
a, 2-b, 2-c) PET film (manufactured by Toyobo Co., Ltd.), Z with the same composition and conditions as in Example 1
A rO ₂ —SiO ₂ thin film was deposited. All conditions are the same as in Example 1 except that a thin film is applied on top of Al vapor deposition.

[Comparative Example 3-a, b, c] Al vapor-deposited thicknesses of 12.3, 6.1 and 3.2 μm (Comparative Example 3-respectively).
a, 3-b, 3-c) PET film (manufactured by Toyobo Co., Ltd.), under the same composition and conditions as in Example 2,
An l ₂ O ₃ -based thin film was deposited. The conditions are all the same as in Example 2 except that a thin film is applied on top of Al vapor deposition.

The characteristics of the film obtained as described above are shown in Tables 1 and 2. In Table 1, the withstand voltage of Examples 1-a, b, c and Example 2-a, b, c with the same film thickness increased as compared with the withstand voltage of Comparative Examples 1-a, b, c. Minutes are shown as "increase in withstand voltage due to thin film". From Table 1, it is clear that the withstand voltage of the films of Examples 1 and 2 of the present invention is higher than that of the film of Comparative Example 1 in which a thin film is not formed.

[0038]

[Table 1]

[Table 2]

Table 2 shows various properties of the films of Example 1-b, Example 2-b and Comparative Example 1-b. The films of Examples 1-b and 2-b of the present invention maintain the heat shrinkage ratio, the three-dimensional surface roughness SΔa, the running property and abrasion resistance of the film at high levels, and the air bleeding speed and resistance to abrasion. It has improved voltage and life characteristics. The "withstand voltage" in Table 2 indicates the withstand voltage per unit film thickness.

[0040]

As described above, according to the insulating film of the present invention, the heat shrinkage rate at 200 ° C., the three-dimensional surface roughness SΔa, the handling property of the film, the running property and abrasion resistance of the film are impaired. In addition, the air bleeding speed, the withstand voltage, and the life characteristics can be improved. Therefore, the insulating film of the present invention is suitable as a dielectric material for capacitors, which has excellent withstand voltage characteristics, running properties and abrasion resistance, and extremely excellent handling characteristics. Of course, it is needless to say that it is also useful in applications other than capacitor dielectrics where improvement in withstand voltage is desired. Therefore,
The insulating film of the present invention has great industrial value.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of an apparatus for evaluating an air escape speed.

FIG. 2 is a diagram showing a schematic configuration in a vacuum chamber of a thin film forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Platform 2 ... Glass flat plate 3 ... Suction pipe 4 ... Vacuum pump 5 ... Film sample 6 ... Adhesive tape 11 ... Water-cooled substrate holder 12 ... Film sample 13 ... Vacuum tank 14 ... Crucible 15 ... Electron gun

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Otani 2-1-1 Katata, Otsu City, Shiga Toyobo Co., Ltd. Research Institute (72) Inventor Yozo Yamada 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd.

Claims (1)

[Claims] 1. An insulating film comprising a plastic film having a ceramic thin film on at least one surface.