KR20200130245A - Biaxially oriented polypropylene film, metallized film, film capacitor, and film roll - Google Patents

Abstract

The thickness is 1.0 µm to 3.0 µm, and the difference between the heat contraction rate at 140°C in the first direction and the heat contraction rate at 130°C in the first direction is 0% or more and less than 2.0%, at right angles to the first direction. Phosphorus Biaxially stretched polypropylene film in which the difference between the heat shrinkage rate at 140°C in the second direction and the heat shrinkage rate at 130°C in the second direction is 0% or more and less than 2.3%.

Description

Biaxially oriented polypropylene film, metallized film, film capacitor, and film roll

The present disclosure relates to a biaxially stretched polypropylene film, a metallized film, a film capacitor, and a film roll.

Biaxially stretched polypropylene films are used as dielectrics for film capacitors because they have excellent electrical properties such as high withstand voltage and low dielectric loss properties, and have high moisture resistance.

As shown in FIGS. 1 and 2, the metallized film 5 constituting the film capacitor includes a biaxially stretched polypropylene film 10 and a metal layer 30 formed on the biaxially stretched polypropylene film 10 do. A metal layer 30 is formed on one of both surfaces of the biaxially stretched polypropylene film 10. On the other hand, FIG. 1 is a cross-sectional view taken along the line I-I in FIG. 2.

As shown in FIG. 2, in the metallized film 5, an insulating margin 21 extending continuously in the longitudinal direction D1 is formed at one end 51 in the width direction D2. Usually, the insulation margin 21 is formed by covering a predetermined position of the biaxially stretched polypropylene film 10 with oil before metal-evaporating the biaxially stretched polypropylene film 10.

A metal layer 30 is positioned next to the insulating margin 21 (in the width direction D2). The metal layer 30 extends from the other end 52 in the width direction D2 to the insulation margin 21. The area of the metal layer 30 is larger compared to that of the insulation margin 21.

The thickness of the metal layer 30 is large at the end portion 52 of the metallized film 5. The portion 31 of the metal layer 30 having a large thickness is sometimes referred to as a heavy edge portion. Hereinafter, the portion 31 is referred to as a heavy edge portion 31. The heavy edge portion 31 extends continuously in the longitudinal direction D1. The heavy edge portion 31 is formed to strengthen the bonding between the metallized film 5 and the metallic electrode. On the other hand, in the metal layer 30, the portion 32 between the heavy edge portion 31 and the insulating margin 21 is sometimes referred to as an active portion. Hereinafter, the portion 32 is referred to as an active portion 32. The thickness of the active portion 32 is smaller than that of the heavy edge portion 31.

In order to produce such a metallized film 5, for example, a molten polypropylene resin is extruded into a sheet with a T-die to obtain a cast master sheet, and heat setting is performed by biaxially stretching the cast master sheet. , When winding it up to obtain a biaxially stretched polypropylene film, attaching oil to the biaxially stretched polypropylene film, performing metal deposition thereon, and producing a metallized film 6 (see Fig. 3) before slit There is.

As shown in FIG. 3, the pre-slit metallized film 6 includes a plurality of insulating margins 21 continuously extending in the longitudinal direction D1, and a plurality of heavy edge portions 31 continuously extending in the longitudinal direction D1. It includes a metal layer 300 having ). In this way, in the pre-slit metallized film 6, the insulating margin 21 and the metal layer 300 are alternately arranged in the width direction D2. Each metal layer 300 includes two active portions 32 and a heavy edge portion 31 positioned between the active portions 32. That is, in each metal layer 300, the first active portion 32, the heavy edge portion 31, and the second active portion 32 are arranged in this order in the width direction D2.

A cutting blade is put in the center in the width direction (center in the width direction (D2)) of each insulating margin 21 in the pre-slit metallized film 6 and the center in the width direction of each heavy edge portion 31, The metallized film 5 can be obtained by dividing the all-metallized film 6 in a plurality in the width direction D2 (hereinafter, referred to as "slit process"). Following this procedure, the width of the insulation margin 21 in the metallized film 5 (the width in the width direction D2) is equal to the width of the insulation margin 21 in the metallized film 6 before the slit. It becomes half. The width (width in the width direction D2) of the heavy edge portion 31 in the metallized film 5 is also half the width of the heavy edge portion 31 in the metallized film 6 before the slit . Here, the rod-shaped arrows shown in FIG. 3 indicate the position of the cutting blade and the cutting direction.

Japanese Patent Application Publication No. 2015-195367

It is preferable that the metallized film obtained in this order has the same width of the insulating margin at one end in the longitudinal direction (eg, the slit start end) and the other end in the longitudinal direction (eg, the slit end). This is because a metallized film whose width of the insulation margin differs greatly at one end and the other end may have an unpredictable influence on the film capacitor.

However, when the thickness of the biaxially stretched polypropylene film is 1.0 µm or more and 3.0 µm or less, in the metallized film after the slit process, a shift in width in the insulation margin is likely to occur at one end in the longitudinal direction and the other end in the longitudinal direction. This is because the thinner the thickness of the biaxially stretched polypropylene film increases the heat shrinkage.

The object of the present disclosure is, in spite of the thin thickness of the biaxially stretched polypropylene film, in the metallized film after the slit process, the deviation of the width in the insulation margin at one end in the longitudinal direction and the other end in the longitudinal direction (hereinafter, It is to provide a biaxially stretched polypropylene film capable of suppressing the "insulation margin width deviation").

The first biaxially oriented polypropylene film (the first biaxially oriented polypropylene film according to the present invention) of the present disclosure has a thickness of 1.0 µm to 3.0 µm, and a heat shrinkage rate of 140° C. in the first direction and the first The difference in the thermal contraction rate at 130°C in the direction is 0% or more and less than 2.0%, and the heat contraction rate at 140°C in the second direction perpendicular to the first direction and the heat contraction rate at 130°C in the second direction The difference in shrinkage is 0% or more and less than 2.3%.

The biaxially stretched polypropylene film of the second present disclosure (the biaxially stretched polypropylene film according to the second present invention) has a thickness of 1.0 µm to 3.0 µm, and a width of 1200 mm or less in the second direction,

It is a biaxially stretched polypropylene film in which the difference between the maximum value and the minimum value of the slow axis angle obtained by the following methods (1) to (3) is less than 6°.

<How to find the difference between the maximum and minimum values of the ground axis angle>

(1) When the total length in the width direction is 100%, a sample for measurement of 50 mm x 50 mm centered at a position at 10% intervals from both ends is cut out,

(2) the second direction of the measurement sample is set to 0°, and the angle of the acute angle between the second direction and the slow axis of each measurement sample is measured,

(3) Of the 9 measurement samples, the maximum and minimum difference of the angle measured in (2) above is calculated.

Here, a description will be given of how the present inventors arrived at the biaxially stretched polypropylene film of the present disclosure.

<The first process and its invention (first invention)>

In the metallized film after the slit process, the inventors have carefully investigated the cause of the deviation of the width in the insulation margin at one end in the longitudinal direction and the other end in the longitudinal direction, and the cause is at the place where the oil for forming the insulation margin is adhered. The inventors of the present invention initially thought that the temperature of the axially stretched polypropylene film was high, and the heat shrinkage was large at that location and that the heat shrinkage was small at the location where oil was not adhered. It was thought that this oil is usually vaporized in order to adhere directly to the biaxially stretched polypropylene film, and adheres at about 130°C to 140°C.

As a cause other than the misalignment of the insulation margin width, the temperature of the biaxially stretched polypropylene film locally increases due to metal vapor (e.g., zinc vapor) for forming the heavy edge, and the temperature distribution in the plane occurs, resulting in large heat shrinkage. It was also thought that points and small points occur. The reason for this thought is that since the temperature of the metal vapor is high, for example, the zinc vapor is about 600°C, the heat shrinkage is considered to be large in the portion to which the metal vapor for forming the heavy edge portion is attached.

However, considering the specific heat of oil and the specific heat of metal, the inventors of the present invention thought that oil has a greater influence than metal vapor on the local temperature increase in the biaxially stretched polypropylene film. In addition, in the process of adhering metal vapor, oil has a greater influence than metal vapor in that the surface opposite to the surface on which the metal vapor of the biaxially stretched film is adhered is intensively cooled by a cooling roll. Thought.

Therefore, in order to suppress the insulation margin width misalignment, referring to the temperature of the insulation margin forming oil as a reference, the thermal contraction rate of 130°C in the first direction and the heat contraction rate of 130°C in the second direction orthogonal to the first direction The inventors focused on reducing the shrinkage rate.

However, the inventors of the present invention found out that the deviation of the insulation margin width does not necessarily depend on the thermal contraction rate of 130°C in the first and second directions.

More specifically, the difference in insulation margin width is the difference between the heat shrinkage rate of 140°C in the first direction and the heat shrinkage rate of 130°C in the first direction, and the heat shrinkage rate of 140°C in the second direction The inventors of the present invention found that the difference in the thermal contraction rate of 130°C in the two directions largely depends.

Based on these findings, the present inventors have come to topcoat the biaxially stretched polypropylene film of the first present disclosure.

In the above configuration, the biaxially stretched polypropylene film is

That the ratio (S _TD140 / S _MD140) a heat shrinkage (S _MD140) of 140 ℃ in the second heat shrinkage percentage (S _TD140) of 140 ℃ in the direction and to the first direction 0.200 more than 0.325 or less is preferred .

When the ratio (S _TD140 /S _MD140 ) is within the above range, the heat shrinkage in the plane in the 140°C region has a good balance (since the heat shrinkage in the first direction and the second direction is balanced), the knitting accuracy is It is more excellent, and the deviation of the insulation margin width can be further suppressed.

In the above configuration, the biaxially stretched polypropylene film is

The width in the second direction is 1200 mm or less,

It is preferable that the difference between the maximum value and the minimum value of the slow axis angle obtained by the following methods (1) to (3) is less than 6°.

<How to find the difference between the maximum and minimum values of the ground axis angle>

(1) When the total length in the width direction is 100%, a sample for measurement of 50 mm x 50 mm centered at a position at 10% intervals from both ends is cut out,

(2) the second direction of the measurement sample is set to 0°, and the angle of the acute angle between the second direction and the slow axis of each measurement sample is measured,

(3) Of the 9 measurement samples, the maximum and minimum difference of the angle measured in (2) above is calculated.

If the difference is less than 6°, the precision of knitting of the biaxially stretched polypropylene film is more excellent. In addition, when a metallized film is produced from the biaxially stretched polypropylene film, the shrinkage variation in the in-plane direction is small, wrinkles and sagging are suppressed, so that it can be preferably used.

Meanwhile, the biaxially stretched polypropylene film of the first disclosure may be for a capacitor.

In addition, the first present disclosure relates to a metallized film, and the first metallized film comprises a biaxially stretched polypropylene film of the first present disclosure and a metal layer laminated on one or both sides of the biaxially stretched polypropylene film. Can have.

Regarding the film capacitor of the first present disclosure, the film capacitor of the first present disclosure may have a metallized film of the first present disclosure wound, or may have a configuration in which a plurality of metallized films of the first present disclosure are stacked. .

Regarding the film roll of the first present disclosure, the film roll of the first present disclosure can be configured such that the biaxially stretched polypropylene film of the first present disclosure is wound in a roll shape.

<The second process and its invention (2nd invention)>

The present inventor examined the influence of oil in the same manner as in the first process. After that, in order to suppress the deviation of the insulation margin width, the present inventors paid attention to the slow axis angle of the biaxially stretched polypropylene film. As a result, the inventors found out that the deviation of the insulation margin width largely depends on the difference between the maximum value and the minimum value of the slow axis angle. Based on these findings, the present inventors have come to topcoat the biaxially stretched polypropylene film of the second present disclosure.

In the above configuration, the biaxially stretched polypropylene film is

That the ratio (S _TD140 / S _MD140) a heat shrinkage (S _MD140) of 140 ℃ in the second heat shrinkage percentage (S _TD140) of 140 ℃ in the direction and to the first direction 0.200 more than 0.325 or less is preferred . The reason is the same as in the case of the first invention.

In the above configuration, the biaxially stretched polypropylene film is

The difference between the heat contraction rate at 140°C in the first direction and the heat contraction rate at 130°C in the first direction is 0% or more and less than 2.0%, and 140°C in the second direction perpendicular to the first direction It is preferable that the difference between the thermal contraction rate of and the thermal contraction rate at 130° C. in the second direction is 0% or more and less than 2.3%.

Meanwhile, the biaxially stretched polypropylene film of the second present disclosure may be for a capacitor.

In addition, the second present disclosure also relates to a metallized film, and the metallized film of the second present disclosure comprises a biaxially stretched polypropylene film of the second present disclosure and a metal layer laminated on one or both sides of the biaxially stretched polypropylene film. Can have.

The second present disclosure also relates to a film capacitor, and the film capacitor of the second present disclosure may have a wound metallized film of the present disclosure, or may have a configuration in which a plurality of metalized films of the second present disclosure are laminated.

Regarding the film roll of the second present disclosure, the film roll of the second present disclosure can be configured such that the biaxially stretched polypropylene film of the second present disclosure is wound in a roll shape.

The biaxially stretched polypropylene film of the present disclosure (the first and second present disclosures) suppresses the deviation of the insulation margin width in the metallized film after the slit process, despite the thin thickness of the biaxially stretched polypropylene film. can do.

1 is a cross-sectional view of a metallized film, and more specifically, a cross-sectional view taken along line II in FIG. 2.
2 is a plan view of a metallized film.
3 is a plan view of a pre-slit metallized film.
4 is a plan view of pre-slit metallized films produced in Examples and Comparative Examples.

Hereinafter, an embodiment of the present invention will be described. However, the present invention is not limited only to these embodiments.

In this specification, the expressions "contain" and "include" include the concepts of "contains", "includes", "consists substantially" and "consists of only".

In this specification, the expression "capacitor" includes the concept of "capacitor", "capacitor element", and "film capacitor".

Since the biaxially stretched polypropylene film of this embodiment is not a microporous film, it does not have many pores.

Although the biaxially stretched polypropylene film of the present embodiment may be constituted by a plurality of layers of two or more layers, it is preferable to be constituted by a single layer.

The biaxially stretched polypropylene film of the present embodiment achieves the above problem in the case of a very small (thin) thickness of 1.0 to 3.0 µm. The biaxially stretched polypropylene film of the present embodiment is not assumed to have a large (thick) case such as 4.5 µm or 5 µm in thickness.

Two directions appearing in this embodiment will be first described here. In the present embodiment, the first direction refers to the same direction as the longitudinal direction of the biaxially stretched polypropylene film. In this embodiment, the first direction is also the same direction as the Machine Direction (hereinafter referred to as "MD direction"). In the following, the first direction is mainly referred to as the MD direction. However, the present invention is not limited to a form in which the first direction points in the same direction as the longitudinal direction, and is not limited to a form in which the first direction points in the same direction as the MD direction. On the other hand, the second direction refers to the same direction as the width direction of the biaxially stretched polypropylene film. In this embodiment, the second direction is also the same direction as the Transverse Direction (hereinafter, referred to as "TD direction"). In the following, the second direction is mainly referred to as the TD direction. However, the present invention is not limited to a form in which the second direction points in the same direction as the width direction, and is not limited to a form in which the second direction points in the same direction as the TD direction.

<Embodiment according to the first invention>

The thickness of the biaxially stretched polypropylene film according to the present embodiment is in the range of 1.0 to 3.0 µm. The thickness of the biaxially stretched polypropylene film according to the present embodiment is preferably 1.2 µm or more, more preferably 1.5 µm or more, and even more preferably 2.0 µm or more. Further, the thickness of the biaxially stretched polypropylene film according to the present embodiment is preferably less than 3.0 µm, more preferably 2.9 µm or less, still more preferably 2.8 µm or less, and particularly preferably 2.5 µm or less. In the case where the thickness of the biaxially oriented polypropylene film according to the present embodiment is within each of the above ranges, including the preferred range, the insulation margin width in the metallized film after the slit process, despite the thin thickness of the biaxially oriented polypropylene film In addition to being able to enjoy the excellent effect of suppressing the shift as much as possible, it is possible to obtain a film capacitor with a smaller size and a larger capacity.

In addition, since the thickness of the polypropylene film is 3.0 µm or less, the electrostatic capacity per unit volume in the case of a capacitor element can be increased, so it can be preferably used for a capacitor.

This point will be described in detail below.

As the thickness of the polypropylene film is thinner, the electrostatic capacity per unit volume can be increased. More specifically, the capacitance (C) is expressed as follows using the dielectric constant (ε), the electrode area (S), and the dielectric thickness (d) (thickness (d) of the polypropylene film).

C=εS/d

Here, in the case of a film capacitor, since the thickness of the electrode is three orders of magnitude or more thinner than the thickness of the polypropylene film (dielectric), if the volume of the electrode is ignored, the volume (V) of the capacitor is represented as follows.

V=Sd

Therefore, from the above two equations, the electrostatic capacity per unit volume (C/V) is expressed as follows.

C/V=ε/d ²

As can be seen from the above equation, the capacitance per unit volume (C/V) is inversely proportional to the square of the thickness of the polypropylene film. In addition, the dielectric constant ε is determined by the material to be used. In that case, it can be seen that, unless the material is changed, the electrostatic capacity per unit volume (C/V) cannot be improved other than thinning the thickness.

That is, assuming that a film capacitor is produced from the same material, (1) when a film capacitor of the same size is produced, a film capacitor having a large capacity is obtained by using a thin polypropylene film. In addition, (2) in the case of producing a film capacitor of the same capacity, using a thin polypropylene film provides a film capacitor having a small size, and space saving is possible.

The thickness of the biaxially stretched polypropylene film refers to a value measured in accordance with JIS-C2330, except that it was measured at 100±10 kPa using a paper thickness meter MEI-11 manufactured by Citizen Seimitsu.

In the biaxially stretched polypropylene film according to the present embodiment, the difference between the thermal contraction rate of 140°C in the MD direction and the thermal contraction rate of 130°C in the MD direction (hereinafter referred to as “MD thermal contraction rate difference”) is 0%. It is not less than 2.0%, and the difference between the thermal contraction rate at 140°C in the TD direction and the thermal contraction rate at 130°C in the TD direction (hereinafter, referred to as “TD thermal contraction rate difference”) is 0% or more and less than 2.3%. In the present specification, the heat contraction rate of 140°C in the MD direction is S _MD140 , the heat contraction rate of 130°C in the MD direction is S _MD130 , and the heat contraction rate of 140°C in the TD direction is S _TD140 and TD direction. In some cases, the thermal contraction rate at 130°C is referred to as S _TD130 . In the present specification, the difference in MD heat shrinkage is _referred to as S _MD140 -S _MD130 , and the difference in TD heat shrinkage is _sometimes referred to as S _TD140 -S _TD130 .

The biaxially stretched polypropylene film according to the present embodiment has a thickness in the range of 1.0 μm to 3.0 μm, but in the metallized film after the slit process, the width in the insulation margin at one end in the length direction and the other end in the length direction It is possible to suppress the deviation of. On the other hand, the width of the insulation margin is measured in the width direction of the biaxially stretched polypropylene film.

The reason why the deviation of the insulation margin width can be suppressed is estimated as follows.

First of all, when forming an insulating margin on a biaxially stretched polypropylene film, it is considered that a temperature variation occurs in the plane of each insulating margin by the insulating margin forming oil.

It is considered that this temperature deviation can be largely divided into a temperature deviation in the TD direction and a temperature deviation in the MD direction.

In the temperature deviation in the TD direction, it is considered that the temperature at the center portion in the TD direction is higher than the temperature at both ends in the TD direction as each insulation margin. It is considered as described above because the oil vapor for forming the insulation margin is ejected in a line shape from the slit of the nozzle, so that the amount of oil in the central portion in the TD direction in the insulation margin becomes larger than that of both ends in the TD direction.

On the other hand, with regard to the occurrence of the temperature deviation in the MD direction, the oil vapor for forming the insulation margin is adjusted to be injected with a constant momentum, but it cannot be declared strictly constant, and it is thought that there is a slight variation in the momentum. It is estimated that a temperature deviation in the MD direction occurs by.

Further, it is considered that the temperature range of the temperature deviation within each insulation margin surface is about 130°C to 140°C. What is considered as such is a case where the oil vapor for forming an insulation margin is usually injected at about 130°C to 140°C. Hereinafter, a region thought to be about 140°C (a region where the amount of oil is considered to be relatively large) is sometimes referred to as a 140°C region or a high temperature region, and a region thought to be about 130°C (a region where the amount of oil is considered to be relatively small) is 130 It is sometimes referred to as the °C range.

It is considered that the biaxially stretched polypropylene film according to the present embodiment can suppress wrinkles and sagging that have conventionally occurred due to such temperature variation. It is conceived as described above, in the biaxially stretched polypropylene film according to the present embodiment, the heat shrinkage rate at 140°C, which corresponds to the temperature in the high temperature region of the insulation margin, and 130°C, which corresponds to the temperature in the 130°C region of the insulation margin. The heat contraction rate of is close in two directions forming a right angle. In other words, when a temperature distribution occurs within each insulation margin in the insulation margin forming oil, a large distribution does not occur in the heat shrinkage rates at 130°C and 140°C of the biaxially stretched polypropylene film, that is, the biaxially stretched polypropylene film Since the values of the thermal contraction rate at 130°C and the thermal contraction rate at 140°C are close to each other, it is considered that wrinkles and sagging can be suppressed.

As a result of suppressing such wrinkles and sagging, it is estimated that the deviation of the insulating margin width can be suppressed by the biaxially stretched polypropylene film according to the present embodiment.

TD orientation ratio of the (second direction), the heat shrinkage rate (S _MD140) of 140 ℃ in the heat shrinkage rate (S _TD140) and the MD direction (the first direction) of 140 ℃ in, that S _TD140 / S _MD140 is 0.200 Above are preferable, 0.240 or more are more preferable, 0.280 or more are still more preferable, and 0.290 or more are especially preferable. In addition, as for S _TD140 /S _MD140 , 0.385 or less is preferable, 0.360 or less is more preferable, 0.330 or less is more preferable, 0.325 or less is still more preferable, 0.320 or less is particularly preferable, and 0.315 or less is particularly even more preferable. Do. In addition, S _TD140 /S _MD140 is preferably 0.200 or more and 0.385 or less, more preferably 0.240 or more and 0.360 or less, and even more preferably 0.280 or more and 0.320 or less, with respect to the range in which the upper and lower limits are defined. When S _TD140 /S _MD140 is within the above range, the heat shrinkage in the plane in the 140°C region has a good balance (since the heat shrinkage in the TD direction and the MD direction is balanced), the flattening accuracy is more excellent and insulation The deviation of the margin width can be further suppressed.

The ratio of the thermal contraction rate of 130°C in the TD direction (S _TD130 ) and the thermal contraction rate of 130°C in the MD direction (S _MD130 ), that is, S _TD130 /S _MD130 is preferably 0.140 or less, and 0.070 or more and 0.130 or less It is more preferable, and 0.080 or more and 0.100 or less are still more preferable. When S _TD130 /S _MD130 is within the above range, the balance of heat shrinkage in the plane in the 130°C region is good (since the balance of heat shrinkage in the TD direction and the MD direction is taken), the flattening accuracy is more excellent and insulation The deviation of the margin width can be further suppressed.

The ratio of the TD heat shrinkage difference (S _TD140 -S _TD130 ) and the MD heat shrinkage difference (S _MD140 -S _MD130 ), that is, (S _TD140 -S _TD130 )/(S _MD140 -S _MD130 ) is preferably 0.920 or more and 1.350 or less. , 0.930 or more and 1.200 or less are preferable, and 0.960 or more and 1.080 or less are more preferable. When (S _TD140 -S _TD130 )/(S _MD140 -S _MD130 ) is within the above range, the balance of heat shrinkage in the plane in the 130-140°C region is good (since the balance of heat shrinkage in the TD and MD directions is taken. ), the flattening precision is more excellent, and the deviation of the insulation margin width can be further suppressed.

Both the MD heat contraction rate difference (S _MD140 -S _MD130 ) and the TD heat shrinkage rate difference (S _TD140 -S _TD130 ) are the speed of the take-up roll that _{winds up the} polypropylene film after biaxial stretching at the downstream of the tenter (hereinafter referred to as “take-up. Speed") and the conveyance speed of the polypropylene film in the MD direction in the tenter stretching part (hereinafter, referred to as "film-forming line speed"), and also the heat setting temperature. These will be described in detail when describing biaxial stretching.

The difference in MD thermal contraction rate (S _MD140 -S _MD130 ) is preferably 0.1% or more, more preferably 0.5% or more, still more preferably 1.0% or more, and particularly preferably 1.5% or more. The difference in MD thermal contraction rate is preferably 1.9% or less, and more preferably 1.8% or less.

On the other hand, the TD heat shrinkage difference (S _TD140 -S _TD130 ) is preferably 0.1% or more, more preferably 0.5% or more, even more preferably 1.0% or more, and particularly preferably 1.5% or more. The difference in TD thermal contraction rate is preferably 2.2% or less, more preferably 2.0% or less, still more preferably 1.9% or less, and particularly preferably 1.8% or less.

The heat contraction rate (S _MD140 ) of 140°C in the MD direction is preferably 10.0% or less, more preferably 9.0% or less, and still more preferably 8.5% or less. The thermal contraction rate (S _MD140 ) at 140°C in the MD direction is preferably 1.0% or more, more preferably 3.0% or more, even more preferably 5.0% or more, and particularly preferably 7.0% or more.

The heat contraction rate (S _TD140 ) at 140°C in the TD direction is preferably 5.0% or less, more preferably 4.0% or less, still more preferably 3.5% or less, and particularly preferably 2.7% or less. The heat contraction rate at 140°C in the TD direction is preferably 0.1% or more, more preferably 0.5% or more, still more preferably 1.0% or more, and particularly preferably 2.0% or more.

The width of the biaxially stretched polypropylene film in the TD direction (second direction) is not particularly limited. However, when the difference between the maximum value and the minimum value of the slow axis angle obtained by the following methods (1) to (3) is less than 6°, the width in the TD direction (second direction) is preferably 1200 mm or less.

That is, the biaxially stretched polypropylene film

The width in the TD direction (second direction) is 1200 mm or less,

It is preferable that the difference between the maximum value and the minimum value of the slow axis angle obtained by the following methods (1) to (3) is less than 6°. This point will be described below.

Here, the slow axis will be described.

The biaxially stretched polypropylene film according to the present embodiment is stretched biaxially in the first direction and in the second direction orthogonal thereto. Since the polymer is oriented in-plane by the biaxial stretching, the biaxially oriented film has birefringence. In the film plane, the orientation at which the refractive index becomes maximum is called the slow axis in terms of the orientation at which the speed of light travel is slow (the phase is slow).

For example, in the sequential biaxial stretching method, first, a cast original sheet is stretched in the traveling direction (MD direction), and then the sheet is stretched in the transverse direction (TD direction). In this case, with respect to the slow axis of the biaxially stretched polypropylene film, the refractive index in the transverse direction in the second direction tends to be greater than the refractive index in the advancing direction in the first direction. Here, the horizontal direction in the second direction becomes the slow axis.

In stretching in the transverse direction (TD direction), when stretching is performed in the completely transverse direction (when stretching is completely performed in the direction orthogonal to the traveling direction), the slow axis angle defined in the present specification is 0°. However, in practice, Poisson's contraction stress, mechanical external force, thermoplastic, etc. of the film act upon stretching, so that it is not completely stretched in the transverse direction (TD direction), and the slow axis angle tends to be greater than 0°. In addition, in the sequential biaxial stretching method, the slow axis angle tends to increase as both ends of the biaxially stretched film become larger.

In this embodiment, the smaller the difference between the maximum value and the minimum value of the slow axis angle is, the more optically the orientation of the two directions orthogonal to the traveling direction in the first direction (MD direction) and the transverse direction in the second direction (TD direction). It can be said that the deviation of the orientation axis is small. Therefore, when producing a metallized film, shrinkage in the oblique direction at the time of heating decreases, and it becomes easy to balance the heat shrinkage in the first direction and the second direction. As a result, wrinkles and sagging during processing are suppressed, and the film can be preferably used. In addition, at the time of film stretching, since the film is deformed in the transverse direction (TD direction) in which the stretching stress acts, the obtained film has excellent knitting accuracy.

In addition, as the maximum value of the slow axis angle is smaller, when the biaxially stretched polypropylene film is formed, it is difficult to apply a deformation force in an oblique direction different from the transverse direction (TD direction). This tends to be excellent. In particular, since the biaxially stretched polypropylene film of the present embodiment has a very small thickness (thin) of 1.0 to 3.0 µm, the effect is remarkable.

The difference between the maximum and minimum values of the slow axis angle according to the present embodiment is not anisotropy of the optical alignment intensity indicated by birefringence, that is, the maximum and minimum values of the second direction and the slow axis, not the size and direction of the orientation itself. It represents the angle formed, that is, the variation width in the width direction of the slow axis angle. In this embodiment, it is a preferred aspect to control the difference to be small.

The reason why it is preferable to control the difference small is that even if the orientation strength by biaxial stretching is given to the flexible material polypropylene to give a certain machining strength, the amount of thermal dimensional change occurring during metal deposition processing is not sufficiently reduced. Rather, it is clear from the result that suppressing the deviation or fluctuation in the orientation direction is useful for suppressing the shrinkage deviation in the in-plane direction.

In addition, the polypropylene film of the present embodiment is characterized by a very small (thin) thickness of 1.0 to 3.0 µm, and is greatly influenced by the temperature of metal vapor deposition. For this reason, the balance of the orientation becomes important as well as the thermal contraction rate. In this embodiment, by reducing the fluctuation width in the width direction of the slow axis angle, it is possible to maintain the balance of the orientation of the thermal contraction.

<How to find the difference between the maximum and minimum values of the ground axis angle>

(1) When the total length in the width direction is 100%, a sample for measurement of 50 mm x 50 mm centered at a position at 10% intervals from both ends is cut out,

(2) the second direction of the measurement sample is set to 0°, and the angle of the acute angle between the second direction and the slow axis of each measurement sample is measured,

(3) Of the 9 measurement samples, the maximum and minimum difference of the angle measured in (2) above is calculated.

The difference between the maximum value and the minimum value of the slow axis angle is preferably less than 6°, more preferably 5.5° or less, even more preferably 5° or less, and particularly preferably 4.5° or less. If the difference is less than 6°, the precision of knitting of the biaxially stretched polypropylene film is more excellent. In addition, when a metallized film is produced from the biaxially stretched polypropylene film, the shrinkage variation in the in-plane direction is small, wrinkles and sagging are suppressed, so that it can be preferably used.

The maximum value of the slow axis angle is preferably less than 15°, more preferably 14.5° or less, even more preferably 13° or less, and particularly preferably 12° or less. When the maximum value is within the above numerical range, when the biaxially stretched polypropylene film is formed, fracture tends to be small and continuous productivity tends to be excellent.

When the difference between the maximum value and the minimum value of the slow axis angle is less than 6°, the width in the TD direction (the second direction) is preferably 1200 mm or less, more preferably 1100 mm or less, and even more preferably 1000 mm or less. In addition, when the difference is less than 6°, the width in the TD direction (the second direction) may be 500 mm or more, 550 mm or more, 600 mm or more.

The measurement apparatus and measurement conditions when determining the difference between the maximum and minimum values of the slow axis angle are as follows.

<Measurement device, measurement conditions>

Measurement device: Retardation measurement device RE-100 manufactured by Otsuka Electronics Co., Ltd.

Light source: Laser light emitting diode (LED)

Band pass filter: 550 nm (measurement wavelength)

Measurement interval: 0.1sec

Integration count: 10time

Measurement score: 15 points

Gain: 10dB

Measurement environment: temperature 23℃, humidity 60%

The difference between the maximum and minimum values of the slow axis angle tends to increase when the heat setting temperature is lowered, and tends to increase when the ratio of the take-up speed to the film forming line speed is increased.

The maximum value of the slow axis angle tends to increase when the heat setting temperature is lowered, and tends to increase when the ratio of the take-up speed to the film forming line speed is increased.

Each of the biaxially stretched polypropylene film and metallized film is wound in a roll shape, and is preferably in the form of a film roll. The film roll may or may not have a winding core (core). It is preferable that the film roll has a winding core (core). The material of the core of the film roll is not particularly limited. Examples of the material include paper (paper tube), resin, fiber reinforced plastic (FRP), and metal. Examples of the resin include polyvinyl chloride, polyethylene, polypropylene, phenol resin, epoxy resin, and acrylonitrile-butadiene-styrene copolymer. Plastics constituting the fiber-reinforced plastic include polyester resins, epoxy resins, vinyl ester resins, phenol resins, and thermoplastic resins. Fibers constituting the fiber-reinforced plastic include glass fiber, aramid fiber (Kevlar (registered trademark) fiber), carbon fiber, polyparaphenylene benzoxazole fiber (Zyron (registered trademark) fiber), polyethylene fiber, boron fiber Etc. are mentioned. Examples of the metal include iron, aluminum, and stainless steel. The core of the film roll also includes a core formed by impregnating the resin into a paper pipe. In this case, the material of the winding core is classified as resin.

Next, preferred raw materials and production methods of the biaxially stretched polypropylene film according to the present embodiment will be described below. However, the raw material and the manufacturing method of the biaxially stretched polypropylene film according to the present embodiment are not limited to the following descriptions, respectively.

The biaxially stretched polypropylene film contains a polypropylene resin. The content of the polypropylene resin is preferably 75% by mass or more, and more preferably 90% by mass or more with respect to the entire biaxially oriented polypropylene film (when the entire biaxially oriented polypropylene film is 100% by mass). , More preferably 95% by mass or more. The upper limit of the content of the polypropylene resin is, for example, 100% by mass, 98% by mass, or the like with respect to the entire biaxially stretched polypropylene film. The polypropylene resin and the biaxially stretched polypropylene film according to the present embodiment may contain one type of polypropylene resin alone, or may contain two or more types of polypropylene resins.

The weight average molecular weight (Mw) of the polypropylene resin is preferably 280,000 or more and 450,000 or less, and more preferably 280,000 or more and 400,000 or less. When the weight average molecular weight (Mw) of a polypropylene resin is 280,000 or more and 450,000 or less, resin fluidity becomes suitable. As a result, it is easy to control the thickness of the cast original sheet, and it becomes easy to produce a thin stretched film.

The molecular weight distribution (Mw/Mn) of the polypropylene resin is preferably 5 or more, more preferably 6.1 or more, even more preferably 6.5 or more, even more preferably 7.2 or more, and particularly preferably 7.5 or more. Further, the molecular weight distribution of the polypropylene resin is preferably 12 or less, more preferably 11 or less, still more preferably 10 or less, and particularly preferably 9.5 or less. It is preferably 5 or more and 12 or less, more preferably 5 or more and 11 or less, and even more preferably 5 or more and 10 or less with respect to the range in which the upper and lower limits of the molecular weight distribution of the polypropylene resin are defined.

In the present specification, the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw/Mn) of the polypropylene resin are values measured using a gel permeation chromatography (GPC) device. More specifically, it is a value measured using HLC-8121GPC-HT (brand name) manufactured by Tosoh Corporation, a differential refractometer (RI) built-in high-temperature GPC measuring instrument. As a GPC column, three TSKgel GMHHR-H(20)HT manufactured by Tosoh Corporation were connected and used. The column temperature was set to 140° C., and trichlorobenzene as an eluent was flowed at a flow rate of 1.0 ml/10 minutes to obtain measured values of Mw and Mn. Using standard polystyrene manufactured by Tosoh Corporation, a calibration curve for its molecular weight (M) is prepared, and the measured values are converted into polystyrene values to obtain Mw and Mn. Here, the logarithm of the base 10 of the molecular weight (M) of standard polystyrene is referred to as the logarithmic molecular weight ("Log(M)").

It is preferable that it is -5% or more and 14% or less of the difference (D _M ) of the fine powder distribution value of a polypropylene resin, It is more preferable that it is -4% or more and 12% or less, and it is still more preferable that it is -4% or more and 10% or less. Here, the "differential distribution value difference (D _M )" is the difference in the molecular weight differential distribution curve by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when the logarithmic molecular weight Log (M) = 4.5. .

On the other hand, "the differential distribution value difference (D _M ) is -5% or more and 14% or less" means a component having a molecular weight of 10,000 to 100,000 on the low molecular weight side from the value of Mw of the polypropylene resin (hereinafter, referred to as "low molecular weight component Log (M) as a representative distribution value of a component having a logarithmic molecular weight Log (M) = 4.5 as a representative distribution value of ") and a component having a molecular weight of around 1 million on the high molecular weight side (hereinafter, also referred to as a "high molecular weight component"). When comparing the components before and after )=6.0, it can be understood that when the difference is positive, there are many low molecular weight components, and when the difference is negative, there are many high molecular weight components.

That is, even if the molecular weight distribution (Mw/Mn) is 5 to 12, it is only showing the width of the molecular weight distribution, and the quantitative relationship between the high molecular weight component and the low molecular weight component is not known. Thus, from the viewpoint of stable film forming property and thickness uniformity of the cast sheet, polypropylene resin has a wide molecular weight distribution, and at the same time, in order to properly include low molecular weight components, a molecular weight of 10,000 to 100,000 components is compared with a molecular weight of 1 million components. Therefore, it is preferable to use a polypropylene resin so that the differential distribution value difference is -5% or more and 14% or less.

The differential distribution value is a value obtained by using GPC as follows. A curve representing the intensity with respect to time obtained by a differential refraction (RI) detection system of GPC (generally also referred to as "elution curve") is used. By using a calibration curve obtained using standard polystyrene and converting the time axis to a logarithmic molecular weight (Log(M)), the elution curve is converted to a curve representing the intensity versus Log(M). Since the RI detection intensity has a proportional relationship with the component concentration, if the total area of the curve indicating the intensity is 100%, an integral distribution curve for the logarithmic molecular weight Log (M) can be obtained. The differential distribution curve is obtained by differentiating this integral distribution curve by Log(M). Therefore, "differential distribution" means a differential distribution with respect to the molecular weight of a concentration fraction. The differential distribution value at a specific Log (M) is read from this curve.

The mesopentad fraction ([mmmm]) of the polypropylene resin is preferably 94% or more, more preferably 95% or more, even more preferably more than 95%, particularly preferably 95.5% or more, and particularly more than 96% More particularly preferred. Further, the mesopentad fraction of the polypropylene resin is preferably 98.5% or less, more preferably 98.4% or less, even more preferably 98% or less, particularly preferably less than 98.0%, and particularly preferably 97.5% or less. , 97.0% or less is particularly more preferable. The mesopentad fraction of the polypropylene resin is preferably 94% or more and 99% or less, and more preferably 95% or more and 98.5% or less. By using such a polypropylene resin, the crystallinity of the resin is suitably improved by a moderately high stereoregularity, and the initial withstand voltage resistance and the long-term withstand voltage are improved. On the other hand, the desired stretchability is obtained by an appropriate solidification (crystallization) rate at the time of forming the cast original sheet.

The mesopentad fraction ([mmmm]) is an index of stereoregularity that can be obtained by high temperature nuclear magnetic resonance (NMR) measurement. Specifically, it can be measured using, for example, Nippon Denshi Co., Ltd. product, high-temperature Fourier transform nuclear magnetic resonance apparatus (high-temperature FT-NMR), and JNM-ECP500. The observation nucleus is ¹³ C (125 MHz), the measurement temperature is 135° C., ortho-dichlorobenzene (ODCB: A mixed solvent of ODCB and deuterated ODCB (mixing ratio = 4/1)) can be used as a solvent for dissolving the polypropylene resin. have. The measurement method by high-temperature NMR can be performed, for example, by referring to the method described in "Japanese Analytical Chemistry and Polymer Analysis Research Conference, New Polymer Analysis Handbook, Kinokuniya Bookstore, 1995, page 610".

The measurement mode can be single-pulse proton broadband decoupling, pulse width of 9.1 μsec (45° pulse), pulse interval of 5.5 sec, integration frequency of 4500 times, and shift standard of CH ₃ (mmmm) = 21.7 ppm.

The pentad fraction representing the three-dimensional regularity is derived from the combination (mmmm and mrrm, etc.) of the five grids (pentads) of the co-arranged lattice ``Meso (m)'' and the bidirectional latticed ``racemo (r)'' It is calculated as a percentage based on the integral value of the intensity of each signal. Each signal derived from mmmm and mrrm, etc. is, for example, "T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988).

The heptane insoluble content (HI) of the polypropylene resin is preferably 96.0% or more, and more preferably 97.0% or more. In addition, the heptane insoluble content (HI) of the polypropylene resin is preferably 99.5% or less, and more preferably 99.0% or less. Here, the more heptane insoluble content is, the higher the stereoregularity of the resin is. When the heptane-insoluble content (HI) is 96.0% or more and 99.5% or less, the crystallinity of the resin is suitably improved due to an appropriately high stereoregularity, and the voltage resistance under high temperature is improved. On the other hand, the speed of solidification (crystallization) at the time of forming a cast original sheet becomes suitable, and it has an appropriate stretchability.

The melt flow rate (MFR) of the polypropylene resin is preferably 1.0 to 8.0 g/10 min, more preferably 1.5 to 7.0 g/10 min, and still more preferably 2.0 to 6.0 g/10 min.

Polypropylene resins can generally be prepared using a known polymerization method. As a polymerization method, a gas phase polymerization method, a bulk polymerization method, and a slurry polymerization method can be illustrated, for example. On the other hand, it is of course possible to use a commercial item as a polypropylene resin.

It is preferable that the total ash resulting from polymerization catalyst residues and the like contained in the polypropylene raw material resin or in the biaxially stretched polypropylene film of the present embodiment is as small as possible in order to improve the electrical properties. The total ash content is preferably 50 ppm or less, more preferably 40 ppm or less, and particularly preferably 30 ppm or less based on polypropylene resin (100 parts by weight).

The polypropylene resin may contain an additive. Examples of the additives include antioxidants, chlorine absorbers, ultraviolet absorbers, lubricants, plasticizers, flame retardants, and antistatic agents. The polypropylene resin may contain an additive in an amount that does not adversely affect the biaxially stretched polypropylene film.

Hereinafter, each polypropylene resin in the case of using two or more polypropylene resins will be described.

When using two or more polypropylene resins, the following linear polypropylene resin A-1 and the following linear polypropylene resin B-1, the following linear polypropylene resin A-2 and the following linear polypropylene resin B-2, the following linear polypropylene resin Preferred examples include propylene resin A-3 and the following linear polypropylene resin B-3, or a combination of the following linear polypropylene resin A-4 and the following linear polypropylene resin B-4. In this embodiment, the expression of linear polypropylene resin A includes the concept of linear polypropylene resin A-1, linear polypropylene resin A-2, linear polypropylene resin A-3, and linear polypropylene resin A-4. . The expression straight-chain polypropylene resin B includes the concepts of straight-chain polypropylene resin B-1, straight-chain polypropylene resin B-2, straight-chain polypropylene resin B-3, and straight-chain polypropylene resin B-4. However, in the present invention, the polypropylene resin is not limited to the following resins.

<Linear polypropylene resin A>

(Linear polypropylene resin A-1)

A linear polypropylene resin having a differential distribution value difference (D _M ) of 8.0% or more.

(Linear polypropylene resin A-2)

A straight-chain polypropylene resin having a heptane insoluble content (HI) of 98.5% or less.

(Linear polypropylene resin A-3)

A linear polypropylene resin having a melt flow rate (MFR) of 4.0 to 10.0 g/10 min at 230°C.

(Linear polypropylene resin A-4)

A linear polypropylene resin having a weight average molecular weight (Mw) of 280,000 or more and 340,000 or less.

<Linear polypropylene resin B>

(Linear polypropylene resin B-1)

A linear polypropylene resin having a differential distribution value difference (D _M ) of less than 8.0%.

(Linear polypropylene resin B-2)

A straight-chain polypropylene resin having a heptane insoluble content (HI) exceeding 98.5%.

(Linear polypropylene resin B-3)

A linear polypropylene resin having a melt flow rate (MFR) of 0.1 to 3.9 g/10 min at 230°C.

(Linear polypropylene resin B-4)

A linear polypropylene resin having a weight average molecular weight (Mw) of more than 340,000.

It is preferable that the weight average molecular weight (Mw) of linear polypropylene resin A is 280,000 or more. Further, the weight average molecular weight (Mw) of the linear polypropylene resin A is preferably 450,000 or less, more preferably 400,000 or less, still more preferably 350,000 or less, and particularly preferably 340,000 or less. When the weight average molecular weight (Mw) of linear polypropylene resin A is 280,000 or more and 450,000 or less, resin fluidity becomes suitable. As a result, it is easy to control the thickness of the cast original sheet, and it becomes easy to produce a thin biaxially stretched polypropylene film. Further, it is preferable that variations in the thickness of the cast original sheet and the biaxially stretched polypropylene film are less likely to occur, and adequate stretchability can be obtained.

The molecular weight distribution (Mw/Mn) of the linear polypropylene resin A is preferably 8.5 or more and 12.0 or less, more preferably 8.5 or more and 11.0 or less, and still more preferably 9.0 or more and 11.0 or less.

When the molecular weight distribution (Mw/Mn) of the straight-chain polypropylene resin A is within the above-described preferred range, it is difficult to cause variation in the thickness of the cast original sheet and the biaxially stretched polypropylene film, and appropriate stretchability is obtained, which is preferable.

The differential distribution value difference (D _M ) of the linear polypropylene resin A is preferably 8.0% or more, more preferably 8.0% or more and 18.0% or less, even more preferably 9.0% or more and 17.0% or less, and 10.0% or more and 16.0% or less. It is particularly preferred.

When the differential distribution value difference (D _M ) is 8.0% or more and 18.0% or less, when the low molecular weight component is compared with the high molecular weight component, it contains a large amount in a ratio of 8.0% or more and 18.0% or less. Therefore, it becomes easy to obtain the surface of the biaxially stretched polypropylene film in this embodiment, and is preferable.

The mesopentad fraction ([mmmm]) of the linear polypropylene resin A is preferably 99.8% or less, more preferably 99.5% or less, and still more preferably 99.0% or less. Further, the mesopentad fraction is preferably 94.0% or more, more preferably 94.5% or more, and even more preferably 95.0% or more. When the mesopentad fraction is within the above numerical range, the crystallinity of the resin is suitably improved by an appropriately high stereoregularity, and the voltage resistance under high temperature is improved. On the other hand, the speed of solidification (crystallization) at the time of forming a cast sheet becomes appropriate, and it has an appropriate stretchability.

The heptane insoluble content (HI) of the linear polypropylene resin A is preferably 96.0% or more, and more preferably 97.0% or more. In addition, the heptane insoluble content (HI) of the linear polypropylene resin A is preferably 99.5% or less, more preferably 98.5% or less, and still more preferably 98.0% or less.

The melt flow rate (MFR) of the linear polypropylene resin A at 230°C is preferably 1.0 to 15.0 g/10 min, more preferably 2.0 to 10.0 g/10 min, and furthermore 4.0 to 10.0 g/10 min. It is preferable, and 4.3-6.0 g/10min is especially preferable. When the MFR at 230° C. of the linear polypropylene resin A is within the above range, since the flow characteristics in the molten state are excellent, unstable flow referred to as a melt fracture hardly occurs, and breakage during stretching is also suppressed. Therefore, since the film thickness uniformity is good, there is an advantage that the formation of a thin-walled portion that is liable to cause insulation breakdown is suppressed.

It is preferable that it is 55 mass% or more with respect to the whole biaxially stretched polypropylene film, and, as for the content rate of linear polypropylene resin A, it is more preferable that it is 60 mass% or more. The content rate of the linear polypropylene resin A is preferably 99.9% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, when the total polypropylene resin in the polypropylene film is 100% by mass, It is particularly preferably 80% by mass or less.

The weight average molecular weight (Mw) of the linear polypropylene resin B is preferably 300,000 or more, more preferably 330,000 or more, more preferably more than 340,000, still more preferably 350,000 or more, and more than 350,000 It is particularly preferred. Moreover, it is preferable that it is 400,000 or less, and, as for the weight average molecular weight (Mw) of linear polypropylene resin B, it is more preferable that it is 380,000 or less.

The molecular weight distribution (Mw/Mn) of the linear polypropylene resin B is preferably 6.0 or more and less than 8.5, more preferably 6.5 or more and 8.4 or less, still more preferably 7.0 or more and 8.3 or less, and particularly preferably 7.2 or more and 8.2 or less.

When the molecular weight distribution (Mw/Mn) of the linear polypropylene resin B is within the above preferable range, it is difficult to cause variation in the thickness of the cast original sheet and the biaxially stretched polypropylene film, and appropriate stretchability is obtained, which is preferable.

The difference in fine powder distribution value (D _M ) of the linear polypropylene resin B is preferably less than 8.0%, more preferably -20.0% or more and less than 8.0%, still more preferably -10.0% or more and 7.9% or less, and -5.0% or more It is particularly preferably 7.5% or less.

The mesopentad fraction ([mmmm]) of the linear polypropylene resin B is preferably less than 99.8%, more preferably 99.5% or less, and still more preferably 99.0% or less. Further, the mesopentad fraction is preferably 94.0% or more, more preferably 94.5% or more, and even more preferably 95.0% or more. When the mesopentad fraction is within the above numerical range, the crystallinity of the resin is suitably improved by an appropriately high stereoregularity, and the voltage resistance under high temperature is improved. On the other hand, the speed of solidification (crystallization) at the time of casting a cast sheet becomes suitable, and it has an appropriate stretchability.

The heptane insoluble content (HI) of the straight-chain polypropylene resin B is preferably 97.5% or more, more preferably 98% or more, still more preferably more than 98.5%, and particularly preferably 98.6% or more. Further, the heptane insoluble content (HI) of the linear polypropylene resin B is preferably 99.5% or less, and more preferably 99% or less.

The melt flow rate (MFR) of the linear polypropylene resin B at 230°C is preferably 0.1 to 6.0 g/10 min, more preferably 0.1 to 5.0 g/10 min, and furthermore 0.1 to 3.9 g/10 min. desirable.

When the linear polypropylene resin B is used as the polypropylene resin, the content of the linear polypropylene resin B is preferably 10% by mass or more, and 15% by mass assuming that the total polypropylene resin in the polypropylene film is 100% by mass. It is more preferable that it is more than %, and it is still more preferable that it is 20 mass% or more. In addition, similarly, the content rate of the linear polypropylene resin B is preferably 45% by mass or less, and more preferably 40% by mass or less when the total polypropylene resin in the polypropylene film is 100% by mass.

When a linear polypropylene resin A and a linear polypropylene resin B are used together as a polypropylene resin, if the total polypropylene resin is 100% by mass, then 55 to 90% by weight of the linear polypropylene resin A and 45 to 10% by weight of the linear chain It is preferable to contain polypropylene resin B, more preferably 60 to 85% by weight of linear polypropylene resin A and 40 to 15% by weight of linear polypropylene resin B, more preferably 60 to 80% by weight of linear polypropylene resin. It is particularly preferable to contain propylene resin A and 40 to 20% by weight of linear polypropylene resin B.

When the polypropylene resin contains the linear polypropylene resin A and the linear polypropylene resin B, the biaxially stretched polypropylene film is in a finely mixed state (phase separated state) of the linear polypropylene resin A and the linear polypropylene resin B, The withstand voltage (especially withstand voltage at high temperatures) is improved, and the capacity in the case of a film capacitor element is improved.

The above description is a description of each polypropylene resin in the case of using two or more polypropylene resins.

The biaxially stretched polypropylene film may contain a resin other than polypropylene resin (hereinafter, also referred to as "other resin"). Other resins include polyolefins other than polypropylene such as polyethylene, poly(1-butene), polyisobutene, poly(1-pentene), and poly(1-methylpentene); Copolymers of α-olefins such as an ethylene-propylene copolymer, a propylene-butene copolymer, and an ethylene-butene copolymer; Vinyl monomer-diene monomer random copolymers such as styrene-butadiene random copolymers; Vinyl monomer-diene monomer-vinyl monomer random copolymers, such as a styrene-butadiene-styrene block copolymer, etc. are mentioned. The biaxially stretched polypropylene film may contain these other resins in an amount within a range that does not adversely affect the biaxially stretched polypropylene film. It is preferable that the biaxially stretched polypropylene film of this embodiment is comprised by polypropylene resin as resin.

The cast original sheet before stretching for producing a biaxially stretched polypropylene film can be produced as follows.

First, polypropylene resin pellets, dry-mixed polypropylene resin pellets, or mixed polypropylene resin pellets prepared by melt-kneading in advance are supplied to an extruder and heated and melted.

The rotational speed of the extruder at the time of heating and melting is preferably 5 to 40 rpm, and more preferably 10 to 30 rpm. Moreover, 220-280 degreeC is preferable and, as for the setting temperature of an extruder at the time of heating and melting, 230-270 degreeC is more preferable. Further, the resin temperature at the time of heating and melting is preferably 220 to 280°C, more preferably 230 to 270°C. The resin temperature at the time of heating and melting is a value measured with a thermometer inserted into the extruder.

On the other hand, the number of rotations of the extruder during heating and melting, the set temperature of the extruder, and the resin temperature are selected in consideration of the physical properties of the crystalline thermoplastic resin used. On the other hand, deterioration of the resin can also be suppressed by making the resin temperature at the time of heating and melting within such a numerical range.

Subsequently, the molten resin is extruded into a sheet using a T-die, cooled and solidified in at least one metal drum to form an unstretched cast master sheet.

The surface temperature of the metal drum (the temperature of the metal drum first contacted after extrusion) is preferably 50 to 100°C, more preferably 90 to 100°C. The surface temperature of the metal drum can be determined according to the properties of the polypropylene resin used.

The biaxially stretched polypropylene film can be produced by subjecting a cast original sheet to a stretching treatment. The stretching is preferably biaxially oriented biaxially vertically and horizontally, and a sequential biaxial stretching method is preferred as the stretching method. As a sequential biaxial stretching method, for example, first, a cast original sheet is passed between rolls having a difference in speed, and stretched 3 to 7 times in the traveling direction (MD direction). Next, the sheet is guided by a tenter and stretched 3 to 11 times in the transverse direction (TD direction). The temperature at the time of stretching in the advancing direction (also referred to as the vertical stretching temperature) is preferably 130 to 150°C. Further, the temperature at the time of stretching in the width direction (also referred to as the horizontal stretching temperature) is preferably 155-170°C. After that, relaxation and heat setting are performed, and the take-up roll is wound up. By the above, a biaxially stretched polypropylene film is obtained.

Both the MD heat shrinkage difference and the TD heat shrinkage difference of the biaxially stretched polypropylene film are as described above, the speed of the take-up roll (take-up speed) for winding the polypropylene film after the biaxial stretching to the downstream of the tenter, and the tenter. It is influenced by the conveyance speed (film-forming line speed) of the polypropylene film in the MD direction in a stretched part. In addition, the difference between the maximum and minimum values of the slow axis angle and the maximum value of the slow axis angle are affected by the take-up speed and the film production line speed. Thus, the ratio of the take-up speed to the film-forming line speed (take-up speed/film-forming line speed) will be described. This ratio is preferably 1.01 or more and 1.20 or less, more preferably 1.02 or more and 1.18 or less, still more preferably 1.03 or more and 1.15 or less, particularly preferably 1.05 to 1.09. By adjusting this ratio to 1.20 or less, it is possible to suppress the tension of the polypropylene film after biaxial stretching on the take-up roll so as to be low so as not to bend, and it is possible to suppress the thermal dimensional deformation preferably small. It is considered that the reason why it is possible to suppress thermal dimensional deformation is that it is possible to suppress the progress of orientation of the polymer molecular chain. By adjusting this ratio to 1.20 or less, it is also possible to suitably suppress the breakage of the polypropylene film after biaxial stretching on the take-up roll. When the ratio of the take-up speed to the film-forming line speed (take-up speed/film-forming line speed) is increased (higher), S _MD140 -S _MD130 , S _TD140 -S _TD130 and S _TD140 /S _MD140 all tend to _rise , and the ratio When is lowered (lowered), S _MD140 -S _MD130 , S _TD140 -S _TD130 and S _TD140 /S _MD140 all tend to go down.

Both the MD heat shrinkage difference and the TD heat shrinkage difference are affected by the heat setting temperature in heat setting after biaxial stretching, as well as the ratio of the take-up speed to the film forming line speed. Further, the difference between the maximum and minimum values of the slow axis angle and the maximum value of the slow axis angle are affected by the heat setting temperature. Thus, the heat setting temperature will be described. The present inventors believe that the phenomenon that the motility of the polymer molecular chain changes depending on the temperature affects the temperature dependence of the thermal contraction rate. In other words, the present inventors speculate that both the MD heat shrinkage difference and the TD heat shrinkage difference are affected by the heat setting temperature, since it is considered that the mobility of the polymer molecular chain with respect to temperature change is changed by the heat setting temperature. . The heat setting temperature is preferably from 159°C to 169°C, more preferably from 161°C to 167°C, still more preferably from 162°C to 166°C, and particularly preferably from 162°C to 164°C. It is preferable that 169°C or less is less than 2.0% of MD heat shrinkage difference and less than 2.3% of TD heat shrinkage difference. 169°C or less is preferable for suppressing fracture of the polypropylene film after biaxial stretching directly on the take-up roll, and for forming a film with good knitting accuracy. Here, the knitting precision refers to the degree of uniformity of the thickness in the TD direction in the biaxially stretched polypropylene film. When the heat setting temperature in heat setting after biaxial stretching is raised (if it is increased), S _MD140 -S _MD130 , S _TD140 -S _TD130 and S _TD140 /S _MD140 all tend to go down, and when the heat setting temperature is lowered ( Lower), S _MD140 -S _MD130 , S _TD140 -S _TD130 and S _TD140 /S _MD140 all tend to _rise .

In this way, the polypropylene film after biaxial stretching is heat-set at 159°C or more and 169°C or less, and winding it up at a ratio of 1.01 or more to 1.20 or less of the take-up speed to the film-forming line speed, whereby the MD heat shrinkage difference is preferably 2.0% While it is possible to set it as less than that, the TD heat contraction rate difference can be made less than 2.3%.

The biaxially stretched polypropylene film may be subjected to corona discharge treatment online or offline after completion of the stretching and heat setting steps for the purpose of enhancing the adhesive properties in post-processes such as metal vapor deposition processing steps. Corona discharge treatment can be performed using a known method. It is preferable to use air, carbon dioxide gas, nitrogen gas, or a mixed gas thereof as the atmospheric gas.

On one side of the biaxially stretched polypropylene film, oil having a pattern corresponding to the pattern of the insulation margin is applied to form an oil mask for insulation margin, and metal vapor deposition is performed thereon to obtain a pre-slit metallized film. The insulating margin oil mask is for preventing metal particles from adhering to a portion of the biaxially stretched polypropylene film that becomes the insulating margin during the deposition process. The insulating margin oil mask can be formed by vaporizing oil stored in an oil tank and applying oil directly to a biaxially stretched polypropylene film from a nozzle formed in the tank. Here, "direct application" means that oil is ejected from a slit of a nozzle, and the oil is adhered to a biaxially stretched polypropylene film. On the other hand, metal deposition is carried out when the biaxially stretched polypropylene film after formation of the insulating margin oil mask passes through the cooling roll. The cooling roll is maintained at -30°C to -20°C, for example. That is, metal deposition is performed when a biaxially stretched polypropylene film having an oil mask for insulating margin passes through the space between the cooling roll and the evaporation source for metal deposition. In this way, in this space, metal vapor is ejected from both sides of the biaxially stretched polypropylene film toward the side on which the oil mask for insulation margin is formed, and adheres to the biaxially stretched polypropylene film. The cooling roll is used to prevent the biaxially stretched polypropylene film from being deformed by the heat of the metal vapor. Metals used in metal deposition include simple metals such as zinc, lead, silver, chromium, aluminum, copper, nickel, mixtures of a plurality of these, and alloys thereof. However, the environment, economy, and film capacitor performance, etc. In consideration, it is preferable to use aluminum for the active portion and zinc and aluminum for the heavy edge portion. Such a metal layer, for example, in a biaxially stretched polypropylene film having an insulating margin oil mask, deposits aluminum on both sides of the area where the active part is to be formed and the area where the heavy edge is to be formed, and to form the heavy edge part. It can be formed by further depositing zinc in the region to be formed. Instead, for example, it is possible to form by depositing aluminum only in the area where the active part is to be formed and zinc deposited only in the area where the heavy edge part is to be formed. On the other hand, in the case of forming a margin pattern on the active part, between the formation of the oil mask for the insulation margin and metal deposition, that is, after the formation of the oil mask for the insulation margin and before the metal deposition, the oil mask for the pattern is placed on both sides of the biaxially stretched polypropylene film It may be formed on the surface on which the oil mask for the insulating margin is formed. The pattern oil mask is usually formed of a plate roll. The temperature of the oil for forming the patterned oil mask is lower than that for forming the insulating margin oil mask. The oil for forming the pattern oil mask is applied to a biaxially stretched polypropylene film, for example, at room temperature (40° C. or less as an example).

The thus obtained pre-slit metallized film and the metallized film obtained by dividing the pre-slit metallized film will be described with reference to the drawings.

As shown in FIG. 3, the pre-slit metallized film 6 includes a plurality of insulating margins 21 continuously extending in the MD direction D1 and a metal layer 300 continuously extending in the MD direction D1. . In the pre-slit metallized film 6, the insulating margin 21 and the metal layer 300 are alternately arranged in the TD direction D2. Each metal layer 300 includes two active portions 32 and a heavy edge portion 31 positioned between the active portions 32. That is, in each metal layer 300, the first active portion 32, the heavy edge portion 31, and the second active portion 32 are arranged in this order in the TD direction D2. In this way, the first active part 32 extends in the TD direction D2 from one end of the heavy edge part 31 in the TD direction D2, and the other part of the heavy edge part 31 in the TD direction D2 The second active part 32 extends from the end in the TD direction D2. The first and second active portions 32 continuously extend in the MD direction D1. The heavy edge portion 31 also extends continuously in the MD direction D1. On the other hand, in the example shown in FIG. 3, the insulating margins 21 are formed at both ends in the TD direction D2 in the pre-slit metallized film 6, but the heavy edge portions ( 31) may be formed.

In the slit process of the pre-slit metallized film 6, the center in the TD direction D2 in each insulating margin 21 (hereinafter, sometimes referred to as ``the center in the TD direction''), and each heavy edge portion ( A cutting blade is put in the center of the TD direction of 31), and the metallized film 6 before slit is divided into plural in the TD direction D2, and the metallized film 5 (refer FIG. 1-2) is obtained. Specifically, a roll-shaped pre-slit metallized film 6 is unwound, and a cutting blade is inserted in the center of each insulation margin 21 in the TD direction and in the center of each heavy edge portion 31 in the TD direction to cut the metallized film. (5) is wound up in a roll shape. Thereby, a plurality of metallized films 5 can be obtained. The width of the insulating margin 21 in the metallized film 5 is half of the width of the insulating margin 21 in the metallized film 6 before the slit. The width of the heavy edge portion 31 in the metallized film 5 is also half the width of the heavy edge portion 31 in the metallized film 6 before the slit. On the other hand, the metallized film 5 has a capacitor element width.

1 and 2, the metallized film 5 thus obtained includes a biaxially stretched polypropylene film 10 and a metal layer 30 formed on one side of the biaxially stretched polypropylene film 10. Equipped. The thickness of the metal layer 30 is preferably 1 to 200 nm.

In the metallized film 5, an insulating margin 21 extending continuously in the MD direction D1 is formed at one end 51 in the TD direction D2. The length of the insulation margin 21 is larger than the width of the insulation margin 21.

A metal layer 30 is positioned next to the insulation margin 21 in the TD direction D2. The metal layer 30 extends from the other end 52 in the TD direction D2 to the insulation margin 21. Although not shown, the metal layer 30 extends continuously between both ends of the MD direction D1 in the metallized film 5. That is, the metal layer 30 extends continuously from one end in the MD direction D1 in the metallized film 5 to the other end in the MD direction D1 in the metallized film 5. The width of the metal layer 30 is larger than that of the insulating margin 21. For example, the width of the metal layer 30 is preferably 1.5 to 300 times the width of the insulation margin 21. Here, the width of the metal layer 30 refers to a value measured by ignoring the margin pattern. Meanwhile, the width of the metal layer 30 is measured in the TD direction D2 of the metallized film 5.

The metal layer 30 of the metallized film 5 includes a heavy edge portion 31. The heavy edge portion 31 is located at the end portion 52 in the TD direction D2 in the metallized film 5. The heavy edge portion 31 extends continuously in the MD direction D1. More specifically, the heavy edge part 31 extends continuously between both ends of the MD direction D1 in the metallized film 5. That is, the heavy edge portion 31 extends continuously from one end in the MD direction D1 in the metallized film 5 to the other end in the MD direction D1 in the metallized film 5 . The thickness of the heavy edge portion 31 is larger than that of the active portion 32. The heavy edge portion 31 may have, for example, an aluminum film formed on the biaxially stretched polypropylene film 10 and a zinc portion formed on the aluminum film. As such, in the heavy edge portion 31, an aluminum film may be positioned between the biaxially stretched polypropylene film 10 and the zinc portion.

The metal layer 30 of the metallized film 5 includes an active part 32. The active part 32 extends continuously in the MD direction D1. More specifically, the active part 32 extends continuously between both ends of the MD direction D1 in the metallized film 5. That is, the active part 32 extends continuously from one end in the MD direction D1 in the metallized film 5 to the other end in the MD direction D1 in the metallized film 5. The active part 32 may have an aluminum film. The aluminum film of the active portion 32 is connected to the aluminum film of the heavy edge portion 31. A margin pattern, for example, a T margin pattern, or the like may be formed in the active portion 32. The film resistance of the heavy edge portion 31 is usually about 1 to 8 Ω/□, preferably about 1 to 5 Ω/□.

The metallized film 5 can be laminated or wound by a conventionally known method to form a film capacitor. For example, so that the metal layer 30 and the biaxially stretched polypropylene film 10 in the metallized film 5 are alternately laminated, and the insulation margin 21 becomes a reverse guide, 2 sheets 1 pair The metallized film 5 is superimposed and wound. At this time, it is preferable to stack two metallized films 5 by shifting 1 to 2 mm in the TD direction D2. The winding machine to be used is not particularly limited, and for example, an automatic winding machine 3KAW-N2 type manufactured by Kaido Corporation, etc. can be used. In the case of manufacturing a flat capacitor, after winding, a press is usually performed on the obtained winding. Pressing promotes the winding tension of the film capacitor and forming the capacitor element. In terms of controlling and stabilizing the interlayer gap, the optimum value of the applied pressure varies depending on the thickness of the biaxially stretched polypropylene film 10, but is, for example, 2 to 20 kg/cm 2. Following the press, a film capacitor is produced by spraying metal on both ends of the wound to form metallic electrodes.

In this way, the film capacitor may have a configuration in which a plurality of metallized films 5 are stacked, or may have a wound metallized film 5. Such film capacitors can be suitably used for capacitors for inverter power supplies that control drive motors such as electric vehicles and hybrid vehicles. Further, it can be suitably used for railway vehicles, wind power generation, solar power generation, general home appliances, and the like.

In Figs. 1 to 3, the metallized film 5 in which the metal layer 30 is formed on one side of the biaxially stretched polypropylene film 10 is described, but the metallized film of the present invention is applied to the metallized film 5 of this structure. Of course it is not limited. For example, the metallized film of the present invention may have metal layers formed on both sides of a biaxially stretched polypropylene film.

Although the metallized film which has a heavy edge part was demonstrated in this embodiment, it goes without saying that it is good even if the metallized film does not have a heavy edge part.

<Embodiment according to the second invention>

Hereinafter, an embodiment according to the second invention will be described. On the other hand, in the biaxially stretched polypropylene film according to the second embodiment of the present invention, the difference between the heat shrinkage rate at 140°C in the first direction and the heat shrinkage rate at 130°C in the first direction is 0% or more and 2.0%. It does not need to be less than, and the difference between the heat shrinkage rate of 140°C in the second direction perpendicular to the first direction and the heat shrinkage rate of 130°C in the second direction need not be 0% or more and less than 2.3%.

The polypropylene film according to the second embodiment according to the present invention (hereinafter, also referred to as “second embodiment”) has a thickness of 1.0 μm to 3.0 μm, a width in the second direction of 1200 mm or less, and the following (1) It is a biaxially stretched polypropylene film in which the difference between the maximum value and the minimum value of the slow axis angle obtained by the method of -(3) is less than 6°.

<How to find the difference between the maximum and minimum values of the ground axis angle>

(1) When the total length in the width direction is 100%, a sample for measurement of 50 mm x 50 mm centered at a position at 10% intervals from both ends is cut out,

(2) the second direction of the measurement sample is set to 0°, and the angle of the acute angle between the second direction and the slow axis of each measurement sample is measured,

(3) Of the 9 measurement samples, the maximum and minimum difference of the angle measured in (2) above is calculated. The biaxially stretched polypropylene film according to the second embodiment of the present invention is excellent in knitting precision. Further, when a metallized film is produced from the biaxially stretched polypropylene film, there is little variation in shrinkage in the in-plane direction, and wrinkles and sagging are suppressed.

In the above configuration, in the biaxially stretched polypropylene film, the difference between the thermal contraction rate of 140°C in the first direction and the thermal contraction rate of 130°C in the first direction is 0% or more and less than 2.0%, and the first direction It is preferable that the difference between the thermal contraction rate of 140°C in the second direction perpendicular to the skeletal and the thermal contraction rate of 130°C in the second direction is 0% or more and less than 2.3%. Other preferred thermal contraction rates of the biaxially stretched polypropylene film according to the present embodiment, and the difference in the thermal contraction rate and the explanation of the ratio of the thermal contraction rate are described in the section of ``First Embodiment According to the Invention'' Is the same as For this reason, description is omitted here. In the second embodiment according to the present invention, for the basis of correction, technical description, and the like, the terms of "the first embodiment according to the present invention" can be cited here.

Preferred aspects of the biaxially stretched polypropylene film according to the present embodiment are the same as those of the "embodiment according to the first invention". For example, (1) physical properties of each film (eg, thickness, total ash, etc.) of the biaxially stretched polypropylene film according to the present embodiment, (2) types, properties, ratios, combinations of polypropylene resins included Etc., (3) types, physical properties, ratios, combinations, etc. other than the polypropylene resin contained, (4) The description of the production method of the biaxially stretched polypropylene film according to the present embodiment, etc. It is the same as the description in the section of "Embodiment according to the invention" In addition, for the description of (5) each physical property of the metallized film according to the present embodiment, a configuration and a method of manufacturing the same, and (6) each physical property of a film capacitor, a configuration, and a method of manufacturing the same, the ``first present invention It is the same as the description in the section of "Embodiment according to". For this reason, description is omitted here. In the second embodiment according to the present invention, for the basis of correction, technical description, and the like, the terms of "the first embodiment according to the present invention" can be cited here.

Example

Next, the present invention (the first invention and the second invention) will be described more specifically by way of examples, but these examples are for explaining the invention, and do not limit the invention at all. In addition, unless specifically stated, "part" and "%" in an example represent "mass part" and "mass%", respectively.

<Measurement of weight average molecular weight (Mw), molecular weight distribution (Mw/Mn), and fine powder distribution value of polypropylene resin>

It measured and calculated under the following conditions using GPC (gel permeation chromatography).

Measuring instrument: High temperature GPC HLC-8121GPC/HT type with built-in differential refractometer (RI) manufactured by Tosoh Corporation

Column: Three connected TSKgel GMHhr-H(20)HT, manufactured by Tosoh Corporation

Column temperature: 145°C

Eluent: Trichlorobenzene

Flow rate: 1.0ml/min

A calibration curve was prepared using standard polystyrene manufactured by Tosoh Corporation, and the value of the measured molecular weight was converted to the value of polystyrene to obtain a weight average molecular weight (Mw) and a number average molecular weight (Mn). The molecular weight distribution (Mw/Mn) was obtained using this Mw and Mn value.

The differential distribution value was obtained by the following method. First, the time curve (elution curve) of the intensity distribution detected using the RI detection system is a distribution curve for the molecular weight M (Log (M)) of standard polystyrene using the calibration curve prepared using the standard polystyrene. Converted. Next, after obtaining the integral distribution curve for Log(M) when the total area of the distribution curve is 100%, the differential distribution curve for Log(M) is obtained by differentiating this integral distribution curve by Log(M). Could The differential distribution values at Log(M)=4.5 and Log(M)=6.0 were read from this differential distribution curve. On the other hand, a series of operations until obtaining the differential distribution curve was performed using the analysis software built into the used GPC measuring device.

<Mesopentad fraction>

Polypropylene resin was dissolved in a solvent, and measured under the following conditions using a high-temperature Fourier transform nuclear magnetic resonance apparatus (high-temperature FT-NMR).

High-temperature nuclear magnetic resonance (NMR) device: manufactured by Nihon Denshi Co., Ltd., high-temperature Fourier transform nuclear magnetic resonance device (high-temperature FT-NMR), JNM-ECP500

Observation nucleus: ¹³ C (125MHz)

Measurement temperature: 135℃

Solvent: Ortho-dichlorobenzene (a mixed solvent of ODCB:ODCB and deuterated ODCB (mixing ratio = 4/1))

Measurement mode: Single pulse proton broadband decoupling

Pulse width: 9.1 μsec (45° pulse)

Pulse interval: 5.5sec

Integration frequency: 4,500 times

Shift standard: CH ₃ (mmmm) = 21.7ppm

The pentad fraction representing the three-dimensional regularity is derived from the combination (mmmm, mrrm, etc.) of the five grids (pentads) of the co-arranged lattice "Meso (m)" and the bidirectionally arranged grid "racemo (r)" It was calculated as a percentage (%) from the intensity integral value of each signal. Regarding the attribution of each signal originating from mmmm or mrrm, for example, see “T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988), etc.

<Measurement of melt flow rate (MFR)>

For each resin, the melt flow rate (MFR) in the form of raw resin pellets was measured in accordance with the condition M of JIS K 7210 using a melt indexer of Toyo Seiki Co., Ltd. Specifically, first, a sample weighed at 4 g was inserted into a cylinder at a test temperature of 230°C, and preheated for 3.5 minutes under a load of 2.16 kg. Then, the weight of the sample extruded from the bottom hole for 30 seconds was measured, and MFR (g/10min) was calculated|required. The above measurement was repeated three times, and the average value was taken as the measured value of MFR.

<Measurement of heptane insoluble content (HI)>

Each resin was press-molded to 10 mm x 35 mm x 0.3 mm to prepare about 3 g of a sample for measurement. Then, about 150 mL of heptane was added, and Soxhlet extraction was performed for 8 hours. The heptane insoluble content was calculated from the mass of the sample before and after extraction.

<Example 1>

[Production of cast original sheet]

PP resin A1 [Mw = 320,000, Mw/Mn = 9.3, differential distribution value difference (D _M ) = 11.2, mesopentad fraction [mmmm] = 95%, HI = 97.3%, MFR = 4.9g/10min, prime Polymer production] and PP resin B1 [Mw = 350,000, Mw/Mn = 7.7, differential distribution value difference (D _M ) = 7.2, mesopentad fraction [mmmm] = 96.5%, HI = 98.6%, MFR = 3.8 g/10min, manufactured by Daehan Emulsion] is supplied to the extruder at a ratio of 65:35, melted at a resin temperature of 250°C, extruded using a T-die, and wound around a metal drum maintaining a surface temperature of 95°C to solidify. And produced a cast original sheet.

[Production of biaxially stretched polypropylene film]

The resulting cast original sheet was maintained at a temperature of 140°C, passed between rolls having a speed difference, stretched 4.5 times in the advance direction, and immediately cooled to room temperature. Subsequently, the stretched film was guided by a tenter and stretched 10 times in the width direction at 160°C, and then relaxation and heat setting were performed, and a 2.3 µm-thick biaxially stretched polypropylene film was wound up on a take-up roll at the tenter outlet. The heat setting temperature during the heat setting was 164°C. The speed of the take-up roll was 1.09 times the speed of the film forming line. That is, the ratio of the take-up speed to the film-forming line speed (take-up speed/film-forming line speed) was set to 1.09.

[Preparation of metallized film before slit]

The biaxially stretched polypropylene film was released from the roll, and an oil mask for insulating margins was formed on the biaxially stretched polypropylene film. Next, an oil mask for patterns having a pattern corresponding to the electrode pattern was formed on the biaxially stretched polypropylene film on which the oil mask for insulation margin was formed. Next, metal vapor deposition was performed on the biaxially stretched polypropylene film on which the pattern oil mask was formed. Thereby, a pre-slit metallized film was obtained.

Here, in order to form an oil mask for insulating margins, vapor of foamblin oil was sprayed on one of both surfaces of the biaxially stretched polypropylene film through a nozzle slit. The insulating margin oil mask was formed in an arc shape (stripe shape) on the entire surface of the biaxially stretched polypropylene film (see Fig. 4).

The pattern oil mask was formed with a plate roll. The pattern oil mask was formed in a pattern substantially corresponding to the electrode pattern of the metal vapor deposition electrode in a region on the entire surface of the biaxially stretched polypropylene film where the arc-shaped insulating margin oil mask was not formed.

In metal deposition, first, aluminum was deposited. The vapor deposition of aluminum was performed on the entire surface of the biaxially stretched polypropylene film on which the oil mask for insulation margin and the oil mask for pattern were formed (hereinafter referred to as "oil mask formation surface"). Then, zinc was vapor-deposited to form a heavy edge part. Zinc was deposited by selecting a region where the heavy edge portion is to be formed on the oil mask formation surface. Metal deposition, that is, aluminum deposition and zinc deposition, was performed while cooling the biaxially stretched polypropylene film with a cooling roll maintained at -30°C to -20°C. That is, when passing the space between the cooling roll and the evaporation source for metal deposition through the biaxially stretched polypropylene film, aluminum was deposited, and then zinc was deposited.

The thus obtained pre-slit metallized film will be described with reference to FIG. 4. As shown in Fig. 4, the pre-slit metallized film (pre-slit metallized film 6) has three insulating margins 21 continuously extending in the MD direction D1, and continuously extending in the MD direction D1. It was to include two metal layers (300). Each insulation margin 21 extends continuously from one end in the MD direction (D1) in the pre-slit metallized film 6 to the other end in the MD direction (D1) in the pre-slit metallized film 6 Has become. Each metal layer 300 also extends continuously from one end in the MD direction (D1) in the pre-slit metallized film 6 to the other end in the MD direction (D1) in the pre-slit metallized film 6, have. In the pre-slit metallized film 6, the insulating margin 21 and the metal layer 300 are alternately arranged in the TD direction D2. Each metal layer 300 includes two active portions 32 and a heavy edge portion 31 positioned between the active portions 32. That is, in each metal layer 300, the first active portion 32, the heavy edge portion 31, and the second active portion 32 are arranged in this order in the TD direction D2. The first and second active portions 32 extend continuously in the MD direction D1. The heavy edge portion 31 also extends continuously in the MD direction D1.

On the other hand, when evaluating the margin accuracy of the pre-slit metallized film 6, of the three insulation margins 21, a cutting blade was inserted into the insulation margin 21 located at the center in the TD direction (D2), and the insulation margin width was adjusted. Measured.

<Example 2>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 1 except that the thickness of the biaxially stretched polypropylene film was set to 2.4 µm.

<Example 3>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 1, except that the thickness of the biaxially stretched polypropylene film was 2.5 µm.

<Example 4>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 1, except that the thickness of the biaxially stretched polypropylene film was 2.8 µm.

<Example 5>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 1, except that the heat setting temperature was 162°C and the speed of the take-up roll was 1.05 times the film forming line speed.

<Example 6>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 4, except that the heat setting temperature was 166°C and the speed of the take-up roll was 1.15 times the film forming line speed.

<Example 7>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 1, except that the heat setting temperature was 161°C and the speed of the take-up roll was 1.02 times the film forming line speed.

<Example 8>

Polypropylene resin B2 instead of polypropylene resin B1 (Mw = 380,000, Mw/Mn = 8.3, D _M = 0.6, mesopentad fraction [mmmm] = 96.7%, HI = 98.8%, MFR = 2.3g/10min, A cast original sheet was produced in the same manner as in Example 1, except for using). Except having used this cast original sheet, it carried out similarly to Example 1, and obtained the biaxially-stretched polypropylene film and the pre-slit metallization film made from this biaxially-stretched polypropylene film.

<Example 9>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 4, except that the heat setting temperature was 166°C and the speed of the take-up roll was 1.12 times the film forming line speed.

<Comparative Example 1>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 3, except that the heat setting temperature was 158°C and the speed of the take-up roll was 1.10 times the film forming line speed.

<Comparative Example 2>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 1, except that the heat setting temperature was 160°C and the speed of the take-up roll was 1.21 times the film forming line speed.

<Comparative Example 3>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 4, except that the heat setting temperature was 160°C and the speed of the take-up roll was 1.21 times the film forming line speed.

<Comparative Example 4>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 8, except that the heat setting temperature was 160°C and the speed of the take-up roll was 1.21 times the film forming line speed.

<Comparative Example 5>

A biaxially stretched polypropylene film and a pre-slit metallized film produced therefrom were obtained in the same manner as in Example 1 except that the heat setting temperature was 170°C and the speed of the take-up roll was 1.22 times the film forming line speed.

<Comparative Example 6>

Polypropylene resin A2 (Mw = 270,000, Mw/Mn = 5.7, D _M = 8.8, HI = 97.8%, MFR = 5.6 g/10min) was used instead of polypropylene resin A1 to replace polypropylene resin B1. Except for using resin B2 (Mw = 380,000, Mw/Mn = 8.3, D _M = 0.6, mesopentad fraction [mmmm] = 96.7%, HI = 98.8%, MFR = 2.3g/10min, manufactured by Daehan Petrochemical) In the same manner as in Example 1, a cast original sheet was produced. Except having used this cast original sheet, it carried out similarly to Example 1, and obtained the biaxially-stretched polypropylene film and the pre-slit metallization film made from this biaxially-stretched polypropylene film.

<Thickness measurement>

In addition to measuring at 100±10 kPa using a paper thickness measuring instrument MEI-11 manufactured by Citizen Semitsu, the thickness of the biaxially stretched polypropylene film was measured in accordance with JIS-C2330.

<Continuous productivity>

Production of a biaxially stretched polypropylene film was initiated using a biaxial stretching device set to a predetermined thickness, and biaxially stretched from the point when the thickness of the obtained biaxially stretched polypropylene film reached ±2% of the target thickness. Until the polypropylene film breaks, the time (hereinafter referred to as "continuous film forming time") that can be continuously formed was measured. On the other hand, when the thickness reaches the target thickness ±2%, a sample is cut out from the center in the width direction of the biaxially stretched polypropylene film, and this sample is made according to JIS-C2330 using a micrometer (JIS-B7502). It confirmed by measuring the thickness of. Based on the obtained continuous film forming time, continuous productivity was evaluated according to the following evaluation criteria.

A: Even if it exceeded 8 hours, it was able to form a film without extending|stretching fracture.

B: In more than 1 hour and less than 8 hours, it was able to form a film without extending|stretching fracture.

C: It stretched and fractured within 1 hour, and film formation exceeding 1 hour was impossible.

＜precision of flat thickness＞

First, a sample was cut out from a biaxially stretched polypropylene film, and the thickness of this sample was measured in accordance with JIS-C2330 using a micrometer (JIS-B7502), and the average and standard deviation of 30 points in the width direction were obtained. Next, the coefficient of variation was calculated based on the equation A. Based on the obtained coefficient of variation, the flattening accuracy was evaluated according to the following evaluation criteria.

Coefficient of variation = standard deviation/mean × 100… Equation A

(Evaluation criteria for the precision of cut meat)

A: Less than 0.9%

B: 0.9% or more, less than 1.5%

C: 1.5% or more

＜130℃ Heat Shrinkage Rate＞

First, in order to measure the thermal contraction rate in the MD direction, a biaxially stretched polypropylene film was cut into a rectangle having a size of 20 mm x 130 mm, and a mark of 100 mm was drawn using a ruler to obtain a sample. In this sample, a side of 130 mm extends in the MD direction. The upper end of this sample was clipped, placed in a dryer, and subjected to heat treatment at 130° C. for 15 minutes. A sample was taken out of the dryer, the interval between the marks was measured with a ruler, and the heat contraction rate was calculated using the following equation.

Heat Shrinkage Rate = (Mark interval before heat treatment-Mark interval after heat treatment) / Mark interval before heat treatment × 100

A sample for measuring the thermal contraction rate in the TD direction was also prepared, and the above-described heat treatment was performed thereon to calculate the thermal contraction rate. In this sample, it is the same as the sample for MD direction measurement except that the side of 130 mm extends in the TD direction.

＜140℃ Heat Shrinkage Rate＞

It measured by the same method as 130 degreeC heat shrinkage except having changed the temperature of heat treatment to 140 degreeC instead of 130 degreeC.

＜120℃ Heat Shrinkage Rate＞

It measured by the same method as 130 degreeC heat shrinkage except having set the temperature of heat treatment to 120 degreeC instead of 130 degreeC.

<Margin precision>

The pre-slit metallized film is unwound from the roll of the pre-slit metallized film, and an insulation margin of 2.0 mm width is divided at the center by a cutting blade, and an insulation margin of 1.0 mm width is provided at the left and right ends, and further 60 mm. A metallized film having a width of the capacitor element was wound up in a roll shape. After sliting for 3000 m, the insulation margin width was measured, and the deviation width with respect to the 1.0 mm width was calculated by difference calculation. Based on this deviation width, the margin accuracy was evaluated according to the following evaluation criteria.

(Evaluation criteria for margin accuracy)

AA: The deviation width is less than 0.1mm

A: The deviation width is more than 0.1mm and less than 0.2mm

B: The deviation width is more than 0.2mm, less than 0.3mm

C: The deviation width exceeds 0.3mm

<Difference between the maximum and minimum values of the ground axis angle>

The biaxially stretched polypropylene films produced in Examples and Comparative Examples were divided into equal portions (slit) so as to be rolls having a width of 1200 mm.

Of the obtained plurality of rolls having a width of 1200 mm, the roll 1 at the end in the width direction of the roll before the slit was taken as Roll 1.

In addition, among the obtained plurality of rolls having a width of 1200 mm, a roll including a central portion (when the central portion overlaps with a slit, any roll on both sides of the central portion) was used as Roll 2.

About Roll 1 and Roll 2, the difference between the maximum value and the minimum value of the slow axis angle was calculated|required according to the following <how to obtain the difference between the maximum value and the minimum value of the ground axis angle>. In addition, the measurement apparatus and measurement conditions are as follows.

<Measurement device, measurement conditions>

Measurement device: Retardation measurement device RE-100 manufactured by Otsuka Electronics Co., Ltd.

Light source: Laser light emitting diode (LED)

Band pass filter: 550 nm (measurement wavelength)

Measurement interval: 0.1sec

Integration count: 10time

Measurement score: 15 points

Gain: 10dB

Measurement environment: temperature 23℃, humidity 60%

<How to find the difference between the maximum and minimum values of the ground axis angle>

(1) When the total length in the width direction was set to 100%, a sample for measurement of 50 mm x 50 mm centered on a position at intervals of 10% from both ends was cut out. That is, (1200/9)mm, ([1200/9]×2)mm, ([1200/9]×3)mm, ([1200/9]×4)mm, ([1200/ 9]×5)㎜, ([1200/9]×6)㎜, ([1200/9]×7)㎜, ([1200/9]×8)㎜, ([1200/9]×9)㎜ A total of 9 samples for measurement of 50 mm x 50 mm centered on the point of were cut out.

(2) Next, the second direction of the measurement sample was set to 0°, and the angle of the acute angle between the second direction and the slow axis of each measurement sample (a total of 9 measurement samples) was measured.

(3) Finally, of the nine measurement samples, the maximum and minimum difference of the angle measured in the above (2) was calculated. Table 5 shows the results. Table 5 also shows the maximum and minimum values.

In this example, when the width of the biaxially stretched polypropylene film was 1200 mm, it was shown that the difference between the maximum value and the minimum value of the slow axis angle was less than 6°. It is clear that the difference becomes smaller as the width (width in the TD direction) decreases. Therefore, in the present embodiment, the example is shown only when the width of the biaxially stretched polypropylene film is 1200 mm, but even when the width is 1200 mm or less (for example, width 600 mm), the difference is naturally less than 6°. It is obvious to be.

<Measurement of ash content>

About the biaxially stretched polypropylene film of an Example and a comparative example, it measured as follows.

Approximately 200 g of a sample was weighed, transferred to a platinum dish, and incinerated at 800°C for 40 minutes. The ash content (ppm) was measured from the obtained ash residue.

As a result, the ash content of the biaxially stretched polypropylene films of Examples and Comparative Examples were all 20 ppm.

[Manufacture of capacitor]

The pre-slit metallized film prepared in Examples was slit to a width of 60 mm. Then, the two metallized films were put together. Using the automatic winding machine 3KAW-N2 type manufactured by Kaido Co., Ltd., the metallized films that were facing each other were wound by 1137 turns at a winding tension of 250 g, a contact pressure of 880 g, and a winding speed of 4 m/s. Element The wound element was subjected to heat treatment at 120°C for 15 hours while pressing with a load of 5.9 kg/cm 2. After that, zinc metal was sprayed onto the cross section of the device. As a thermal spraying condition, a feed rate of 15 mm/s, a thermal spraying voltage of 22 V, and a thermal spraying pressure of 0.3 MPa were used, and spraying was performed so that the thickness was 0.7 mm. In this way, a flat capacitor was obtained. The lead wire was soldered to the end face of the flat capacitor. After that, the flat capacitor was sealed with an epoxy resin. The curing of the epoxy resin was performed by heating at 90°C for 2.5 hours and then heating at 120°C for 2.5 hours. All of the finished film capacitors had a capacitance of 75 μF.

5 metallized film
6 slit pre-metallized film
10 Biaxially oriented polypropylene film
21 insulation margin
30 metal layer
31 Heavy Edge
32 active part
51 One end of the metallized film
52 The other end of the metallized film
300 metal layer

Claims (7)

Thickness is 1.0㎛ to 3.0㎛,
The difference between the heat contraction rate at 140°C in the first direction and the heat contraction rate at 130°C in the first direction is 0% or more and less than 2.0%,
A biaxially stretched polypropylene film in which a difference between a heat shrinkage rate of 140°C in a second direction perpendicular to the first direction and a heat shrinkage rate of 130°C in the second direction is 0% or more and less than 2.3%. The method of claim 1,
The ratio of the heat contraction rate (S _TD140 ) of 140°C in the second direction and the heat contraction rate (S _MD140 ) of 140°C in the first direction (S _TD140 /S _MD140 ) is 0.200 or more and 0.325 or less, biaxial Stretched polypropylene film. The method according to claim 1 or 2,
The width in the second direction is 1200 mm or less,
Biaxially stretched polypropylene film in which the difference between the maximum and minimum values of the slow axis angle obtained by the following methods (1) to (3) is less than 6°:
<How to find the difference between the maximum and minimum values of the ground axis angle>
(1) When the total length in the width direction is set to 100%, a sample for measurement of 50 mm x 50 mm centered at a 10% interval from both ends is cut out;
(2) measuring the angle of the acute angle between the second direction and the slow axis of each measurement sample with the second direction of the measurement sample being 0°;
(3) Of the 9 measurement samples, the maximum and minimum difference of the angle measured in (2) above is calculated. The method according to any one of claims 1 to 3,
Biaxially stretched polypropylene film for capacitors. The biaxially stretched polypropylene film of any one of claims 1 to 4, and
Metallized film having a metal layer laminated on one side or both sides of the biaxially stretched polypropylene film. A film capacitor having a structure in which the metallized film of claim 5 is wound or a plurality of metallized films of claim 5 are laminated. A film roll, wherein the biaxially stretched polypropylene film according to any one of claims 1 to 4 is wound in a roll shape.

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