JPH0680793A - Biaxially oriented syndiotactic polystyrene film for capacitor - Google Patents

Abstract

PURPOSE:To obtain the title film having good electrical characteristics and heat resistance, excellent traveling characteristics and abrasion resistance, and good handleability regardless of film thickness. CONSTITUTION:The film is made from a styrene polymer having a substantially syndiotactic configuration and has an internal haze (per 10mum) of at most 10%, a heat shrinkage at 200 deg.C of at most 5%, a three-dimensional surface roughness SDELTAa of 0.004 to 0.04 at least on one side and an air escape rate of at most 900 sec.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a syndiotactic polystyrene type biaxially stretched film for capacitors, and more specifically, it has good electric characteristics and heat resistance, and has good running property.
The present invention relates to a syndiotactic polystyrene-based biaxially stretched film for capacitors, which has excellent abrasion resistance and has good handling properties regardless of the film thickness.

[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. Further, in order to improve the production rate, the temperature applied to the film is increased, and the demand for heat resistance is becoming severe. The syndiotactic polystyrene biaxially stretched film is excellent in heat resistance and electrical properties, and is expected to be developed for use as a film for capacitors. However, in the syndiotactic polystyrene biaxially stretched film, if the film is simply thinned, the handling characteristics during the production and processing of the film will be poor. Also,
When a lubricant is added to improve the handling property, the syndiotactic polystyrene polymer is brittle, so that voids are generated around the lubricant. as a result,
Of the electrical characteristics, the withstand voltage characteristic and the life characteristic are deteriorated, and abrasion is apt to occur during film running. Also,
If the heat setting temperature is increased to improve the heat resistance, the brittleness increases, and the chipping is more likely to occur. As a film having good slipperiness, it is known that inorganic particles are added, the surface roughness Ra is in a specific range, and the coefficient of static friction is limited (JP-A-3-74437).

[0003]

However, with the above-described conventional film having good slipperiness, good handling characteristics can be obtained at low speed work, but there is a problem that the handling characteristics rapidly deteriorate at high speed work. . Further, in the syndiotactic polystyrene biaxially stretched film, the handling property tends to deteriorate particularly when the thickness of the film becomes thin, and the above-mentioned inorganic particles are added to define the range of the surface roughness Ra and the coefficient of static friction. The film has the same tendency, and even if good handling characteristics were obtained for that reason, desired handling characteristics could not be obtained when the thickness was changed.
Further, the syndiotactic polystyrene-based polymer is brittle, and voids are generated around the lubricant added to improve the slip property during stretching, which causes deterioration of withstand voltage characteristics and life characteristics of electrical characteristics. Become. Further, the voids also lead to scraping of the projections during the film running, causing scratches on the film surface and generation of white powder on the roll. Furthermore, when the heat setting temperature is increased to improve the heat resistance of the film, the syndiotactic polystyrene biaxially stretched film is particularly fragile and is likely to be scraped while the film is running. An object of the present invention is to provide a syndiotactic polystyrene biaxially stretched film for capacitors, which has excellent electrical properties and heat resistance, as well as excellent running properties and wear resistance, and excellent handling properties regardless of the film thickness. And

[0004]

DISCLOSURE OF THE INVENTION The present invention provides an internal haze (1
(Per 0 μm) is 10% or less, the three-dimensional surface roughness S Δa of at least one surface is 0.004 or more and 0.04 or less, and the air bleeding speed is 900 seconds or less, excellent electrical characteristics, and It is intended to provide a syndiotactic polystyrene biaxially stretched film having good handling properties regardless of the film thickness. The polystyrene polymer with stereoregularity having a syndiotactic structure used in the present invention has a tacticity of diad (two constitutional units) in which a phenyl group or a substituted phenyl group which is a side chain is quantified by a nuclear magnetic resonance method. It is desirable that the syndiotactic structure is 85% or more, and pentad (5 constitutional units) is 50% or more. Examples of the polystyrene-based polymer include polystyrene, poly (p-, m- or o-methylstyrene), poly (2,4-, 2,5-, 3,4- or 3,5-dimethylstyrene), poly (P-tertiarybutylstyrene) and other poly (alkylstyrene), poly (p-, m- or o-chlorostyrene), poly (p-, m- or o-bromostyrene), poly (p-, m -Or o-fluorostyrene), poly (o-methyl-p
-Poly (halogenated styrene) such as fluorostyrene), poly (halogen-substituted alkylstyrene) such as poly (p-, m- or o-chloromethylstyrene), poly (p-,
m- or o-methoxystyrene), poly (p-, m- or o-ethoxystyrene), etc. poly (alkoxystyrene), poly (p-, m- or o-carboxymethylstyrene), etc. poly (carboxyalkyl) Examples include poly (alkyl ether styrene) such as styrene) poly (p-vinylbenzylpropyl), poly (alkylsilylstyrene) such as poly (p-trimethylsilylstyrene), and poly (vinylbenzyldimethoxyphosphide).

In the present invention, polystyrene is particularly preferable among the polystyrene polymers. Also,
The polystyrene-based polymer having a syndiotactic structure used in the present invention is not necessarily a single compound, and if the syndiotacticity is within the above range, a polystyrene-based polymer having an atactic structure or an isotactic structure is used. It may be a mixture of, a copolymer and a mixture thereof. The polystyrene-based polymer used in the present invention has a weight average molecular weight of 10,000 or more, more preferably 50,000 or more. When the weight average molecular weight is less than 10,000, it is not possible to obtain a biaxially stretched film having excellent strength and elongation characteristics and heat resistance. The upper limit of the weight average molecular weight is not particularly limited, but if it is 1500,000 or more, breakage may occur due to an increase in stretching tension, which is not preferable. Furthermore, the syndiotactic polystyrene biaxially stretched film of the present invention may be a known method, for example, a sequential biaxial stretching method in which longitudinal stretching and transverse stretching are performed in order, and transverse / longitudinal stretching.
A stretching method such as a longitudinal stretching method, a longitudinal / transverse / longitudinal stretching method, or a longitudinal / longitudinal / transverse stretching method can be adopted, and the stretching method is selected according to various characteristics such as required strength and dimensional stability. Further, in order to improve the adhesive property and the like of the vapor deposition layer, an adhesive layer can be provided by in-line coating or off-line coating, corona treatment or the like can be performed. Then, the internal haze, the three-dimensional surface roughness S Δa, and the air bleeding speed are adjusted by the film forming conditions and the lubricant particles. The type and amount of the lubricant particles are not particularly limited as long as the internal haze, the three-dimensional surface roughness SΔa and the air bleeding speed fall within the predetermined ranges, but silica, titanium dioxide, talc, kaolinite, etc. Examples thereof include particles inactive to syndiotactic polystyrene-based polymers such as metal oxides, salts of metals such as calcium carbonate, calcium phosphate, and barium sulfate, or particles formed of 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 0.01 μm or more and 2.0 μm or less, and particularly 0.05 μm or more and 1.5 μm or more.
The particle size variation is preferably 25 μm or less, and the addition amount is 100% by weight of syndiotactic polystyrene polymer.
On the other hand, the content is preferably 0.005% by weight or more and 2.0% by weight or less, and particularly preferably 0.1% by weight or more and 1.0% by weight or less. In addition, it is preferable that the shape of the lubricant particles includes at least one kind having a surface 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) x 1
00 (%) The polystyrene-based polymer used in the present invention may contain, if necessary, a suitable amount of a known antioxidant, antistatic agent or the like. The blending amount is preferably 10% by weight or less with respect to 100% by weight of the polystyrene polymer. If it exceeds 10% by weight, breakage tends to occur during stretching, resulting in poor production stability. Internal haze of the syndiotactic polystyrene biaxially stretched film of the present invention
(Per 10 μm) is 10% or less, preferably 8% or less. If the internal haze (per 10 μm) exceeds 10%, the withstand voltage characteristics and life characteristics will be poor, and the lubricant with voids will be easily scraped off, resulting in poor wear resistance.

The heat shrinkage ratio of the syndiotactic polystyrene biaxially stretched film of the present invention at 200 ° C. is 5% or less, preferably 3% or less, more preferably 2% or less. If the heat shrinkage ratio is larger than 5%, shrinkage and irregularity of flatness occur in the capacitor manufacturing process, leading to defective products. Here, since the abrasion resistance becomes poor when the film is exposed to a high temperature for a long time in order to reduce the heat shrinkage rate, a relaxation treatment is performed after the longitudinal stretching treatment, and the heat setting temperature and time are kept within a certain range, Further, if necessary, it is preferable to perform lateral and / or longitudinal relaxation treatment after the heat setting treatment. Here, the longitudinal relaxation treatment after the longitudinal stretching is performed at a stretching temperature or higher and a cold crystallization temperature or lower so that the film after the longitudinal relaxation treatment has a shrinkage rate of 5% or less at 5% or less. 220 ℃ or more,
It is preferable to perform the treatment at a temperature below the melting point within 30 seconds, preferably within 10 seconds, and the relaxation treatment in the horizontal and vertical directions is preferably performed at a temperature not higher than the maximum temperature of the heat setting treatment so that the flatness is not disturbed. Further, the syndiotactic polystyrene-based biaxially stretched film of the present invention has at least one three-dimensional surface roughness S
Δa must be in the range of 0.004 to 0.04. When S Δa is less than 0.004, handling characteristics and running properties are poor, and when S Δa exceeds 0.04, withstand voltage characteristics and life characteristics are poor. Furthermore, the syndiotactic polystyrene biaxially stretched film of the present invention needs to have an air bleeding speed of 900 seconds or less. More preferably, it is 700 seconds or less.
That is, the air bleeding speed is 900 seconds or less, and more preferably 700
By setting the time to be equal to or less than a second, a syndiotactic polystyrene biaxially stretched film having good handling characteristics can be obtained regardless of the thickness and strength of the film even during high-speed work. On the other hand, if the air bleed speed exceeds 900 seconds, the handling characteristics during high-speed work will be poor, and, for example, when winding the film into a roll at high speed, air will be entrapped between the film and the take-up roll. Wrinkles are liable to occur, the winding shape becomes poor, and the film is meandered in the width direction due to the lubricating effect of the air layer in which the film is wound, resulting in uneven roll end surfaces.

[0007]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation method of the film is shown below. (1) Internal haze The film thickness was converted to 10 μm in conformity with JIS-K6714 using a Poic integrating sphere HTR meter SEP-H2D manufactured by Nippon Seimitsu Optical Co., Ltd. (2) Thermal shrinkage at 200 ° C. The shrinkage of the film in an atmosphere of 200 ° C. for 30 minutes without tension was determined.

(3) Three-dimensional surface roughness S Δa Using a stylus-type three-dimensional surface roughness meter (SE-3AK, manufactured by Kosaka Laboratory Ltd.) on the film surface, the radius of the needle is 2 μm and the load is
Cutoff value of 0 in the longitudinal direction of the film under the condition of 30 mg.
25 mm, measuring length 1 mm, 2 μm pitch
It is divided into 500 points and the height of each point is calculated by 3D roughness analyzer (SP
A-11). The same operation was continuously performed 150 times in the widthwise direction of the film at intervals of 2 μm, that is, over 0.3 mm in the widthwise direction of the film, and the data was taken into the analyzer. Next, SΔa was obtained using an analyzer. (4) Venting speed The measuring device shown in FIG. 1 is prepared. That is, a circular hole 1a is provided on the upper surface of the base 1, a glass plate 2 having a diameter of 70 mm is fixed in the hole 1a, and the glass plate 2 is fixed between the outer periphery of the glass plate 2 and the hole wall 1b. A groove is formed, and a ring-shaped groove 1c surrounding the hole 1b is opened, the groove 1c is communicated with the groove on the outer periphery of the glass flat plate 2, and the vacuum pump 4 is inserted through the pipe 3 into the groove 1c. Connect the suction port of. Then, a film sample 5 having a size that covers the glass flat plate 2 is placed on the upper surface of the base 1, and the outer periphery of the film sample 5 is hermetically fixed to the base 1 with an adhesive tape 6, and the vacuum pump 4 is driven to drive the glass flat plate. The time (seconds) from the appearance of the interference fringes on the outer peripheral portion of 2 to the spread of the interference fringes on the entire surface of the glass flat plate 2 and the movement thereof is measured, and this time (second) is defined as the air bleeding speed.

(5) Handling characteristics of film When slitting a wide slit roll at a high speed and rewinding it into a narrow roll, can a roll without problems be obtained without causing misalignment of the end of the roll, wrinkles, valves and the like? Please 4
It was graded and evaluated 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 can be obtained. (6) Film runnability and abrasion resistance When the film is slit into a narrow width and rubbed against a metal roll and run, the tape is tensioned after passing through a guide roll by applying a constant supply tension. The size, the occurrence of scratches, and the amount of white powder adhered to the roll are evaluated 5 times, and the results are shown in the following ranking. Runnability evaluation 1st class; large tension, many scratches 2nd class; tension, slightly large, scratches considerably 3rd class; medium tension, slight scratches 4th class; tension, small, almost no scratches 5th class; small tension, no scratches here If the resulting tensions and scratches have different ranks, the worse rank is used. Abrasion resistance evaluation 1st grade: White powder is very much generated 2nd grade: White powder is often generated 3rd grade: White powder is slightly generated 4th grade: White powder is hardly generated 5th grade: White powder is not generated

(7) Average particle size Lubricant particles were observed with a Hitachi Ltd. S-510 scanning electron microscope, and a photographed product was magnified and copied to trace the external shape of the lubricant. The individual particles were painted black. This image was measured for the Feret diameter in the horizontal direction of each particle using a Luzex 500 type image analyzer manufactured by Nikole Co., Ltd., and the average value was taken as the average particle diameter. Also,
The degree of variation in particle size was calculated by the following formula. Variance = (standard deviation of particle size / average particle size) x 100
(%) (8) Area shape factor 20 particles are arbitrarily selected from the trace image used to measure the average particle diameter, and the projected cross-sectional area of each particle is measured using the image analysis device used in (7). did. 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 particle) x 100 (%)

(9) Withstand voltage The test was performed according to JIS C-2318. Using a 10KV DC withstanding voltage test group, the voltage when the film was broken and short-circuited was read at a boosting rate of 100V / sec in an atmosphere of 23 ° C and 50% RH. (10) Life characteristics Aluminum was vapor-deposited on a syndiotactic polystyrene biaxially stretched film using a vacuum vapor deposition machine to create a capacitor with 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 rate of the element having a function as a capacitor was measured without short-circuiting among 100 pieces.

EXAMPLE As a lubricant, 3.0% by weight of calcium carbonate having an average particle size of 1.0 μm, a degree of variation of 20% and an area shape factor of 80% was added to 100% by weight of syndiotactic polystyrene (weight average molecular weight 300000). Chips and non-lubricated polymer chips were mixed at a weight ratio of 1: 9, dried, melted at 295 ° C, extruded through a T-die with a 200 μm lip gap, and cooled at 40 ° C. Then, they were brought into close contact with each other and solidified by cooling by the electrostatic loading method to obtain an amorphous sheet of 72 μm. The amorphous sheet is first preheated to 95 ° C. by a roll, four infrared heaters having a surface temperature of 680 ° C. are further heated, and the film is stretched at a film temperature of 133 ° C. by a factor of 3.6, and then a ceramic roll of 135 ° C. 13% longitudinal relaxation between metal rolls at 40 ℃
It was preheated to 0 ° C., stretched 3.3 times in the transverse direction at a stretching temperature of 120 ° C., and heat-set at 260 ° C. for 12 seconds. Then 6 at 225 ° C
% Lateral relaxation treatment, and further 3% longitudinal relaxation treatment at 210 ° C. The thickness of the obtained film was 6 μm.

Comparative Example The extrusion speed was changed so that the thickness of the amorphous sheet was 60 μm,
In the longitudinal stretching, the film temperature was raised to 100 ° C. by a metal roll, the film was stretched 3.0 times, heat-set at 270 ° C. for 60 seconds, and the relaxation treatment after heat-setting was not performed. The same operation was performed.

[0014]

[Table 1]

[0015]

As described above, according to the present invention, by adopting the constitution as set forth in the claims, electric characteristics and heat resistance are excellent, and running property and wear resistance are excellent. There is provided a film suitable as a dielectric material of a capacitor having excellent handling properties regardless of the film thickness, and therefore, the industrial value of the present invention is great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an apparatus for measuring an air escape rate according to the present invention.

[Explanation of symbols]

 1: Platform 2: Glass flat plate 3: Suction pipe 4: Vacuum pump 5: Film sample 6: Adhesive tape

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI technical display location B29L 31:34 4F C08L 25:06 (72) Inventor Tadashi Okuhira 2-1-1 Katata, Otsu City, Shiga Prefecture No. 1 Toyobo Co., Ltd.

Claims (1)

[Claims] 1. A styrene-based polymer having a substantially syndiotactic structure, an internal haze (per 10 μm) of 10% or less, and a thermal shrinkage at 200 ° C. of 5% or less, and at least one three-dimensional structure. A syndiotactic polystyrene biaxially stretched film for a condenser, which has a surface roughness S Δa of 0.004 or more and 0.04 or less and an air bleeding speed of 900 seconds or less.