KR20160128314A - Biaxially oriented polypropylene film - Google Patents

Abstract

It is an object of the present invention to provide a biaxially oriented polypropylene film which has high strength and low heat shrinkage and is excellent in transparency and can be suitably used as a film for a production process such as a film for flat panel display or a display or a film for a capacitor. The value of the sum of the tensile elastic modulus E _MD in the longitudinal direction of the film and the tensile elastic modulus E _TD in the transverse direction of E _{MD + TD} is 4.5 GPa or more, the total haze is 1% or less, and the heat shrinkage rate after treatment at 85 캜 for 100 hours is The biaxially oriented polypropylene film is 1.0% or less in both the longitudinal direction and the width direction of the film.

Description

Biaxially oriented polypropylene film {BIAXIALLY ORIENTED POLYPROPYLENE FILM}

The present invention relates to a biaxially oriented polypropylene film which can be suitably used as a film for a manufacturing process such as a film for flat panel display or a display, or a film for a capacitor, which has high strength and low heat shrinkage and is excellent in transparency.

Since the biaxially oriented polypropylene film is excellent in transparency, mechanical properties, and electric characteristics, it is used for various applications such as packaging use, release use, tape use, cable wrapping, and electric applications including capacitors.

Further, in recent years, studies have been made to develop the film as a flat panel display film, such as a polarizer protective film or a retardation film, taking advantage of the optical characteristics and productivity of the polypropylene film (for example, Patent Documents 1 and 2). However, in the polypropylene film, the surface of the film is rough and the haze of the film is increased due to the? Crystals of polypropylene produced during melt extrusion, and visibility is sometimes lowered when used for display purposes. Particularly, in a biaxially oriented film, fibrils due to? Crystals are generated in the stretching process in the width direction, and the haze is sometimes increased. In order to improve the transparency of the polypropylene film, it is possible to use a polypropylene having a low stereoregularity as the raw material, a method of increasing the content of the polyethylene component, or a method of adding a petroleum resin or the like to decrease the crystallinity of the polypropylene However, since the above component is generally a flexible component or has a low heat resistance, the strength and heat resistance of the film sometimes deteriorate when the addition amount is large. Further, in the production method, in order to prevent the transparency from deteriorating, a method of non-stretching or longitudinal uniaxial stretching can be considered, but the strength of the film is sometimes lowered. For example, Patent Document 3 discloses that syndiotactic polypropylene is used as a raw material and the cooling roll after extrusion is made low to suppress the crystal formation of the non-oriented sheet, and further, 1 to 4 times in the longitudinal direction An example of improving the transparency of a polypropylene film by axial stretching is disclosed. In these polypropylene films, the syndiotactic polypropylene having a low crystallinity was used as the raw material, and the film had a low stretching magnification and was also uniaxially stretched, resulting in insufficient strength of the film. If the strength of the film is insufficient, for example, when the polarizer and the film of the present invention are adhered to each other in the flat panel display film, the film is deformed by the tension of the apparatus and the phase difference is changed, . Further, in the capacitor application, the withstand voltage sometimes decreased.

Examples of both strength and transparency of a polypropylene film are disclosed in Patent Documents 4 and 5. However, both the strength and the transparency were insufficient for use as a flat panel display.

Japanese Patent Application Laid-Open No. 2013-152455 Japanese Patent Application Laid-Open No. 2010-164733 Japanese Patent Application Laid-Open No. 2010-195993 Japanese Patent Application Laid-Open No. 2003-170485 Japanese Patent Application Laid-Open No. 2009-012225

An object of the present invention is to solve the above problems. That is, it is an object of the present invention to provide a biaxially oriented polypropylene film which can be suitably used as a film for a production process such as a film for flat panel display, a display, or the like, and a capacitor, which has high strength and low heat shrinkage and is excellent in transparency. In the present invention, strength refers to strength of a material which is hard to be deformed, and a tensile modulus of elasticity is used as an index thereof. That is, in this specification, high strength refers to a high tensile modulus.

In order to solve the above problems and to achieve the object, the biaxially oriented polypropylene film of the present invention is characterized in that the sum of the tensile elastic modulus E _MD in the longitudinal direction of the film and the tensile elastic modulus E _TD in the width direction of the film E _{MD + TD} A value of 4.5 GPa or more, a total haze of 1% or less, and a heat shrinkage rate after 100 hours of processing at 85 占 폚 is 1.0% or less in both the longitudinal direction and the width direction of the film.

The biaxially oriented polypropylene film of the present invention can be suitably used as a film for a production process such as a film for flat panel display or a display or a film for a capacitor because of its high strength, low heat shrinkage and excellent transparency.

In the biaxially oriented polypropylene film of the present invention, the value of the sum of the tensile elastic modulus E _MD in the longitudinal direction of the film and the tensile elastic modulus E _TD in the width direction E _{MD + TD} is not less than 4.5 GPa. When the value of E _{MD + TD} is less than 4.5 GPa, when the film is used as a film for flat panel display, for example, when the polarizer and the film of the present invention are bonded to each other, the film is deformed by the tension of the apparatus, The color tone of the display may be shifted. Further, in the capacitor application, the withstand voltage may be lowered. The value of E _{MD + TD} is more preferably 5.0 GPa or more, still more preferably 5.5 GPa or more, and particularly preferably 6.0 GPa or more. The value of E _{MD + TD} is preferably as large as possible, but is about 20 GPa upper limit, more preferably 10 GPa or lower, and still more preferably 7 GPa or lower. It is also preferable that the values of E _MD and E _TD are all 2 GPa or more. Even if the value of E _{MD + TD} is 4.5 GPa or more, there is a case where the difference in tensile modulus between the longitudinal direction and the transverse direction is greater than or equal to a certain value, the handling property such as cracking of the film may be deteriorated. In order to set the value of E _{MD + TD} to the above-mentioned range, it is necessary to set the raw material composition of the film to the range described below, to obtain a high transparency film while reducing the flexibility component such as low stereoregularity polypropylene, , And stretching the film at a high magnification to obtain a biaxially oriented polypropylene film.

In the biaxially oriented polypropylene film of the present invention, the value of E _MD / E _TD is preferably 0.5 or more and 2.0 or less. If the value of E _MD / E _TD is out of the above range, the alignment balance of the biaxially oriented polypropylene film becomes poor and the film tends to be easily cracked during handling. The value of E _MD / E _TD is more preferably 0.55 or more and 1.5 or less, and still more preferably 0.57 or more and 1.2 or less. In order to set the value of E _MD / E _TD within the above range, it is preferable to obtain a biaxially oriented polypropylene film by setting the stretching conditions of MD and TD and the heat fixing conditions within the ranges described later.

In the present application, a direction parallel to the film-forming direction of the film is referred to as a film-forming direction or a longitudinal direction or MD direction, and a direction orthogonal to the film-forming direction within the film surface is referred to as a width direction or a TD direction.

The biaxially oriented polypropylene film of the present invention has a total haze of 1% or less. If the total haze exceeds 1%, the visibility of the display may be lowered when used as a film for a flat panel display. Further, in the use of a capacitor, in particular, in the case of a thin film having a thickness of 2 탆 or less, a film tear may occur at the time of vapor deposition of a metal layer. This is thought to be due to the fact that the minute voids inside the film caused by the beta crystal of polypropylene cause tearing of the film. The total haze is more preferably 0.8% or less, and still more preferably 0.5% or less. The lower the haze in terms of transparency, the better, but the lower the haze is substantially 0.05%.

In order to set the total haze to the above-mentioned range, it is preferable that the raw material composition of the film is set within the range described below, and the cast condition and the longitudinal stretching condition are set within the range described later, and the β crystal of the cast sheet is reduced.

The biaxially oriented polypropylene film of the present invention has a heat shrinkage rate of 1.0% or less in both the longitudinal direction and the transverse direction of the film after the treatment at 85 캜 for 100 hours. When the heat shrinkage percentage exceeds 1.0%, when the flat panel display is used at a high temperature, the film is peeled off due to the shrinkage stress of the film to decrease the visibility, or the phase difference changes due to the shrinkage stress of the film, . In the capacitor application, the film itself shrinks due to the heat of the capacitor manufacturing process and the use process, and the withstand voltage property may be lowered due to the poor contact with the device end metallocon. The heat shrinkage percentage is more preferably 0.5% or less, further preferably 0.3% or less, and most preferably 0.1% or less. The lower limit is not particularly limited, but the film may be excessively expanded, and substantially -1.0% is the lower limit. In order to keep the heat shrinkage within the above-mentioned range, the raw material composition should be kept within the range described below, and the addition amount of the low melting point component should be reduced as much as possible while maintaining the transparency and the longitudinal stretching condition, transverse stretching condition, heat fixing condition, It is preferable to reduce the heat shrinkage while maintaining the strength.

The biaxially oriented polypropylene film of the present invention preferably has a ten-point average roughness SRz of at least 500 nm. When at least SRz of one side is 500 nm or less, the visibility of the display can be made higher when used as a film for a flat panel display. The SRz of at least one side is more preferably 200 nm or less, still more preferably 150 nm or less, and most preferably 100 nm or less. At least the SRz of one side is preferably as low as possible, but practically about 1 nm is the lower limit. In order to set the SRz to the above-mentioned range, it is preferable to reduce the β crystal of the cast sheet by setting the raw material composition of the film to the range described later, and also casting conditions and longitudinal stretching conditions within the ranges described later.

The biaxially oriented polypropylene film of the present invention preferably has a center average surface roughness SRa of at least 50 nm at least on one side. When the SRa of at least one surface is 50 nm or less, the visibility of the display can be made higher when it is used as a film for a flat panel display. The SRa of at least one side is more preferably 20 nm or less, and still more preferably 15 nm or less. The lower the SRa of at least one side is, the better, but the lower limit is substantially 1 nm or so. In order to set the SRa within the above-mentioned range, it is preferable to reduce the β crystal of the cast sheet by setting the raw material composition of the film to a range described later and casting conditions and longitudinal stretching conditions within a range described later.

In the biaxially oriented polypropylene film of the present invention, the in-plane retardation Ret of the film is preferably 0.1 to 500 nm. In the flat panel display film, the required retardation of the film differs depending on the part to be used, and is about 0.1 to 100 nm for an optically isotropic film such as a polarizer protective film and about 50 to 500 nm for a retardation film such as a quarter- . If the retardation exceeds 500 nm, the color tone of the display may change. In the capacitor applications, the higher the retardation is, the higher the orientation of the film is and the withstand voltage is improved. In order to set the value of Ret to the above range, it is preferable that the raw material composition, the longitudinal stretching condition, the transverse stretching condition, the heat fixing condition, and the relax condition are within the ranges described later.

In the biaxially oriented polypropylene film of the present invention, when the retardation in the thickness direction of the film is defined as Rth, it is preferable that the ratio Rth / Ret of the retardation value to Ret is 1 or less. In the flat panel display film, when the value of Rth / Ret is 1 or less, the viewing angle characteristics are improved. The value of Rth / Ret is more preferably 0.8 or less, and still more preferably 0.5 or less. The value of Rth / Ret is a lower limit value that can be controlled to about 0.1, although the target value is appropriately set according to the configuration of the display to be used. In order to set the value of Rth / Ret within the above range, it is preferable that the raw material composition, the longitudinal stretching condition, the transverse stretching condition, the heat fixing condition, and the relax condition are within the ranges described later.

In the biaxially oriented polypropylene film of the present invention, the coefficient of static friction μ s between one side of the film and the back side thereof is preferably 0.5 or less. If the static friction coefficient s exceeds 0.5, the slipperiness of the film is deteriorated and handling becomes difficult, and wrinkles may be formed during film formation or subsequent processing, or the wound shape of the product roll may be deteriorated. The static friction coefficient μs is more preferably not more than 0.45, and still more preferably not more than 0.4. It is preferable that the static friction coefficient s is low from the viewpoint of handling property. However, in order to lower the static friction coefficient s, the surface must be roughened, and the haze rises and the transparency deteriorates. In order to set the static friction coefficient s in the above range, it is preferable to set the composition of the raw material, the lamination structure of the film, the longitudinal stretching condition, and the transverse stretching condition within the range described later.

The biaxially oriented polypropylene film of the present invention preferably has a melting point Tm of 158 DEG C or higher. If the melting point Tm is less than 158 占 폚, there are cases where the heat resistance is insufficient and the heat shrinkage ratio is large or the content of the ethylene component is large, so that the tensile rigidity is lowered and fish eyes are likely to occur. The melting point Tm is more preferably 160 DEG C or higher, and still more preferably 163 DEG C or higher. From the viewpoint of reducing the heat shrinkage ratio, the melting point Tm of the biaxially oriented polypropylene film is preferably as high as possible, but practically, the upper limit is about 180 deg. In order to keep the melting point Tm within the above-mentioned range, it is preferable to set the composition of the raw material to fall within the range described below, to reduce the content of the ethylene component having a low heat resistance, to set the longitudinal stretching condition, transverse stretching condition, . When two or more melting peak temperatures of the film are observed in the differential scanning calorimeter, the melting point Tm of the biaxially oriented polypropylene film is defined as the peak temperature with the lowest temperature.

The thickness of the biaxially oriented polypropylene film of the present invention is suitably adjusted according to the application, and is not particularly limited, but is preferably 0.5 m or more and 100 m or less. If the thickness is less than 0.5 mu m, handling may become difficult. When the thickness exceeds 100 mu m, the thickness of the non-stretch sheet becomes thick, so that the cooling rate in the cooling roll at the time of extrusion is slowed, The haze of the film may be increased. More preferably, the thickness is in the range of 5 to 60 mu m for flat panel display use, and more preferably 5 to 30 mu m. In the capacitor application, it is preferably 0.5 to 10 탆, more preferably 1 to 3 탆. The thickness can be adjusted by the number of screw revolutions of the extruder, the width of the non-extruded sheet, the film forming speed, the stretching magnification, and the like within a range not deteriorating other physical properties.

Next, preferred polypropylene raw materials which are used in a biaxially oriented polypropylene film will be described.

In the biaxially oriented polypropylene film of the present invention, it is preferable to use at least two types of polypropylene raw materials (referred to as polypropylene raw material A and polypropylene raw material B). As the polypropylene raw material A, it is preferable to use a highly crystalline polypropylene raw material in order to improve the strength of the film. As the polypropylene raw material B, a polypropylene raw material having a low stereoregularity Is preferably used.

The polypropylene raw material A is preferably polypropylene having a cold xylene soluble portion (hereinafter referred to as CXS) of 4 mass% or less and a meso pentad fraction of 0.95 or more. If these are not satisfied, the film-forming stability may deteriorate, the strength of the film may decrease, and the dimensional stability and the withstand voltage may be deteriorated.

Here, the cold xylene soluble portion (CXS) refers to a polypropylene component dissolved in xylene when the film is completely dissolved in xylene and then precipitated at room temperature. The polypropylene component is low in crystallinity and low in molecular weight, It is considered to be a hard component. If such a component is contained in a large amount in the resin, the thermal dimensional stability of the film may deteriorate, or the dielectric breakdown voltage at a high temperature may be lowered. Therefore, CXS is preferably 4 mass% or less, more preferably 3 mass% or less, and particularly preferably 2 mass% or less. The lower the CXS is, the better, but the lower limit is about 0.1 mass%. Such a CXS-containing polypropylene can be prepared by a method of increasing the catalytic activity in obtaining the resin and a method of washing the obtained resin with a solvent or a propylene monomer itself.

From the same viewpoint, the mesopentad fraction of the polypropylene raw material A is preferably 0.95 or more, more preferably 0.97 or more. The meso pentad fraction is an index showing the stereoregularity of the crystalline phase of polypropylene measured by a nuclear magnetic resonance method (NMR method). The higher the numerical value, the higher the degree of crystallization, the higher the melting point, and the higher the breakdown voltage It is preferable. The upper limit of the meso pentad fraction is not specifically defined. In order to obtain such a highly stereoregular resin, a method of cleaning a resin powder obtained with a solvent such as n-heptane, a method of properly selecting a catalyst and / or a cocatalyst, and a method of appropriately selecting a composition are employed.

More preferably, the polypropylene raw material A has a melt flow rate (MFR) of 1 to 10 g / 10 min (230 캜, 21.18 N load), particularly preferably 2 to 5 g / 10 min ) Is preferable from the viewpoints of film formability and film strength. In order to adjust the melt flow rate (MFR) to the above-mentioned value, a method of controlling the average molecular weight and the molecular weight distribution is adopted.

As the polypropylene raw material A, a homopolymer of propylene is mainly included, but other unsaturated hydrocarbon-based copolymer components and the like may be contained within the scope of not impairing the object of the present invention, and a polymer which is not propylene alone may be blended. As a monomer component constituting such a copolymerization component or blend, for example, ethylene, propylene (in the case of a copolymerized blend, 1-butene, 1-pentene, 3-methylpentene-1,3-methylbutene- 1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl- 2-norbornene, etc. The copolymerization amount or the blend amount is preferably less than 1 mol% as a copolymerization amount and less than 10 mass% as a blend amount from the viewpoint of resistance to dielectric breakdown and dimensional stability Do.

Next, the polypropylene raw material B will be described.

As the polypropylene raw material B, it is preferable that the polypropylene raw material is low in crystallinity and stereoregularity so as to have good compatibility with the above-mentioned polypropylene raw material A and to obtain high transparency. As the polypropylene raw material B, amorphous polypropylene, low stereoregular polypropylene, syndiotactic polypropylene, alpha -olefin copolymer and the like can be used, but from the viewpoint of obtaining excellent transparency with a small addition amount, Polypropylene and low stereoregular polypropylene are particularly preferred.

The amorphous polypropylene preferably used as the polypropylene raw material B is preferably a polypropylene polymer having mainly atactic stereoregularity as a main component, and more specifically, a copolymer with a homopolymer or an? -Olefin have. In particular, the latter, that is, an amorphous polypropylene -? - olefin copolymer is preferable. In the present invention, the term " main component " means that the specific component accounts for 50% or more by mass of the total components, more preferably 80% by mass or more, further preferably 90% 95% by mass or more.

The amorphous polypropylene can be produced as a by-product of isotactic polypropylene upon homopolypropylene polymerization. Since the glass transition temperature is lower than that of general polypropylene, it can be extracted as boiling n-heptane (or xylene) soluble fraction of homopolypropylene. It is also possible to polymerize the amorphous polypropylene independently by varying the catalyst and polymerization conditions to be applied in the production of the crystalline polypropylene. The amorphous polypropylene preferably used in the present invention is not particularly limited as long as it is produced by a conventionally known production method. As the amorphous polypropylene having the above characteristics, a commercially available product such as "Thapselen" manufactured by Sumitomo Chemical Co., Ltd. can be suitably selected and used.

When the amorphous polypropylene-? -Olefin copolymer is used as the amorphous polypropylene in the present invention, examples of the? -Olefin include 1-butene, 1-pentene, 1-hexene, 1-decene, 4-methyl-1-pentene, or propylene-ethylene-1-butene.

Examples of the amorphous polypropylene-? -Olefin copolymer using such? -Olefin include propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, propylene-1-butene copolymer, propylene / ethylene / cycloolefin Copolymers, propylene / ethylene / butadiene copolymers, and the like.

The low stereoregular polypropylene preferably used as the polypropylene raw material B is preferably a homopolymer of propylene and produced by using a metallocene catalyst as a polymerization catalyst. The melting point of the low stereoregular polypropylene is 100 DEG C or lower, more preferably 60 DEG C to 90 DEG C, and particularly preferably 65 DEG C to 85 DEG C. The weight average molecular weight is preferably 40,000 to 200,000, and the molecular weight distribution Mw / Mn is preferably 1 to 3 (Mw: weight average molecular weight, Mn: number average molecular weight). As the low stereoregular polypropylene having the above characteristics, a commercially available product such as "ELMODY" manufactured by Idemitsu Kosan Co., Ltd. can be suitably selected and used.

In addition, the biaxially oriented polypropylene film of the present invention may contain branched polypropylene H in addition to the polypropylene raw material A and the polypropylene raw material B from the viewpoints of improving the strength and improving the withstand voltage. When added, it is preferably 0.05 to 10% by mass, more preferably 0.5 to 8% by mass, further preferably 1 to 5% by mass. By containing the branched chain polypropylene H, the size of spherical crystals produced in the cooling step of the melt-extruded resin sheet can be controlled to be small, and a polypropylene film excellent in transparency and strength can be obtained.

The branched chain polypropylene H preferably has a melt flow rate (MFR) in the range of 1 to 20 g / 10 min, more preferably 1 to 10 g / 10 min, from the viewpoint of film formability. The melt tension is preferably in the range of 1 to 30 cN, more preferably in the range of 2 to 20 cN. Herein, the branched chain polypropylene H is polypropylene having 5 or less internal tri-substituted olefins among 10,000 carbon atoms. The presence of this internal tri-substituted olefin can be confirmed by the proton ratio of ¹ H-NMR spectrum.

In the biaxially oriented polypropylene film of the present invention, it is preferable that the content of the ethylene component contained in the polymer constituting the film is 10 mass% or less. More preferably 5 mass% or less, and further preferably 3 mass% or less. The higher the content of the ethylene component, the lower the crystallinity and the better the transparency. However, when the content of the ethylene component exceeds 10% by mass, the strength may be lowered and the heat resistance may be lowered to deteriorate the heat shrinkage ratio.

In the biaxially oriented polypropylene film of the present invention, the content of the petroleum resin contained in the polymer constituting the film is preferably 5% by mass or less. More preferably not more than 3% by mass, still more preferably not more than 1% by mass, most preferably not containing a petroleum resin. By adding a petroleum resin, transparency and strength can be improved. However, when the content of the petroleum resin exceeds 5% by mass, the heat resistance is lowered and the heat shrinkage ratio is lowered and the cost of the raw material is increased.

In the biaxially oriented polypropylene film of the present invention, the content of the cycloolefin polymer contained in the polymer constituting the film is preferably 5 mass% or less. More preferably not more than 3% by mass, still more preferably not more than 1% by mass, most preferably not containing a cycloolefin polymer. When the content of the cycloolefin polymer is more than 5% by mass, transparency deteriorates due to the compatibility with polypropylene and the haze deteriorates and the cost of the raw material is reduced .

The biaxially oriented polypropylene film of the present invention preferably has a content of the polypropylene polymer contained in the polymer constituting the film of 95 mass% or more from the viewpoints of transparency, heat resistance and strength. More preferably 96 mass% or more, further preferably 97 mass% or more, and most preferably 98 mass% or more.

The polypropylene raw material of the present invention may contain various additives such as a nucleating agent, an antioxidant, a heat stabilizer, a sliding agent, an antistatic agent, an antiblocking agent, a filler, a viscosity adjusting agent, And the like.

The selection of the kind and amount of the antioxidant is important from the standpoint of long-term heat resistance. That is, the antioxidant is a phenol type having sterically hindered properties, and at least one of them is preferably a high molecular weight type having a molecular weight of 500 or more. Specific examples thereof include various ones. For example, 1,3,5-trimethyl-2,4,6-tris (2,2,6-trimethyl-2,4,6-tris 1,3,5-di (tert-butyl) -4-hydroxybenzyl) benzene (for example, Irganox (registered trademark) 1330: molecular weight 775.2, manufactured by BASF) or tetrakis (for example, Irganox (registered trademark) 1010: molecular weight 1177.7, manufactured by BASF), and the like are preferably used in combination. The total content of these antioxidants is preferably in the range of 0.03 to 1.0 mass% with respect to the total amount of the polypropylene. If the amount of the antioxidant is too small, the polymer may be deteriorated in the extrusion process, resulting in coloring of the film or deterioration in long-term heat resistance. If the amount of the antioxidant is too large, the transparency of the antioxidant may deteriorate due to bleed-out. The more preferable content is 0.1 to 0.9 mass%, particularly preferably 0.2 to 0.8 mass%.

A nucleating agent may be added to the polypropylene raw material of the present invention within a range not contrary to the object of the present invention. As already explained, the branched polypropylene (H) has already had a crystal nucleating agent effect of an? -Crystal or? -Crystal itself, but it is difficult to use a kind of? -Crystalline nucleating agent (dibenzylidene sorbitol, sodium benzoate etc.) Amide compounds such as potassium 1,2-hydroxystearate, magnesium benzoate, and N, N'-dicyclohexyl-2,6-naphthalenedicarboxamide, quinacridone compounds, etc.). However, the excess amount of the nucleating agent may cause transparency or strength deterioration due to stretching property, void formation, etc. Therefore, the addition amount is usually 0.5% by mass or less, preferably 0.1% by mass or less, 0.05 mass% or less, and most preferably not added.

The biaxially oriented polypropylene film of the present invention is obtained by biaxially stretching using the above-mentioned raw materials. The biaxial stretching method can be obtained by any of biaxial stretching by simultaneous inflation, biaxial stretching by stenter simultaneous biaxial stretching, and stenter biaxial stretching. Among them, film forming stability, thickness uniformity, It is preferable to adopt the stenter biaxial stretching method in terms of controlling the high strength and dimensional stability.

Next, the structure of the film using the polypropylene raw material will be described.

The biaxially oriented polypropylene film of the present invention preferably has a laminated structure of at least two layers in order to simultaneously satisfy high strength, high transparency and low heat shrinkage.

In the biaxially oriented polypropylene film of the present invention, at least one layer (hereinafter referred to as I layer) of the laminated structure preferably contains 96 mass% or more of polypropylene raw material A from the viewpoint of high strength and low heat shrinkage. The content of the polypropylene raw material A in the I layer is more preferably 97% by mass or more, and still more preferably 98% by mass or more. When the content of the polypropylene raw material A in the I layer is less than 96% by mass, the orientation of the film is lowered and the strength is lowered, and in the case where many additive components with low heat resistance are present, the heat shrinkage may be increased.

In the biaxially oriented polypropylene film of the present invention, at least one layer (hereinafter referred to as II layer) of the lamination structure has a mixing ratio of the polypropylene raw material A and the polypropylene raw material B of 50: 50 to 95: 5 (mass ratio, the same shall apply hereinafter). More preferably 60:40 to 95: 5, and still more preferably 70:30 to 93: 7. If the mixing ratio of the polypropylene raw material B in the II layer exceeds 50, the strength and heat resistance may be lowered. If it is less than 5, the stereoregularity of the unstretched film becomes too high, and transparency may be lowered at the time of stretching.

The biaxially oriented polypropylene film of the present invention has a laminated structure of at least two layers and preferably includes at least one layer of the above-described I layer and II layer. The layer thickness ratio of the I layer in the thickness direction of the film is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, particularly preferably 2% or more. The layer thickness ratio of the II layer is preferably 1% or more, more preferably 10% or more, still more preferably 15% or more, and most preferably 20% or more.

In the biaxially oriented polypropylene film of the present invention, it is preferable that at least the surface layer of one side (hereinafter referred to as lubricant particle) is contained in at least one side of the lamination structure from the viewpoint of reducing the friction coefficient. Examples of the inorganic particles include silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black, and zeolite particles. Examples of the organic particles include acrylic resin A resin particle, a styrene resin particle, a polyester resin particle, a polyurethane resin particle, a polycarbonate resin particle, a polyamide resin particle, a silicone resin particle, a fluorine resin particle, Or more of the monomer copolymerized resin particles. However, since the polypropylene resin has a low surface energy, when the resin is stretched by adding particles, voids may be generated due to peeling of the particle interface at the time of drawing, and haze may rise to lower transparency. From the viewpoint of improving the transparency, it is preferable to use the above-mentioned inorganic particles or organic particles subjected to a silane coupling treatment on the surface, particularly silica particles treated with a silane coupling treatment.

The average particle diameter of the lubricant particles is preferably from 0.1 mu m or more to less than 1.0 mu m. If the average particle diameter is less than 0.1 占 퐉, the particles may aggregate to form coarse particles, which may lower the transparency. If the average particle diameter is 1.0 占 퐉 or more, voids are likely to be generated at the particle interface at the time of stretching, and transparency may be lowered. Further, the particles added to the surface layer fall off into the film, the surface roughness increases, and the haze increases. The average particle diameter is more preferably from 0.1 탆 to less than 0.9 탆, and further preferably from 0.1 탆 to less than 0.8 탆. In addition, from the viewpoint of improving handling properties, particles having two or more different average particle diameters may be used in combination.

The biaxially oriented polypropylene film of the present invention preferably has at least two layered laminated structures and at least the surface layer of one side contains the lubricant particles. The thickness of the layer containing the lubricant particles is preferably 0.05 to 2.0 mu m. When the thickness is less than 0.05 탆, the live particles sometimes fall off during film formation. If it is more than 2.0 占 퐉, the haze increases and the transparency may be lowered. The thickness of the layer containing the lubricant particles is more preferably 0.1 to 1.0 占 퐉, and still more preferably 0.2 to 0.8 占 퐉.

The content of the lubricant particles in the raw material of the layer containing the lubricant particles is preferably 0.01 mass% or more and less than 1.0 mass%. When the content is less than 0.01% by mass, the effect of reducing the friction coefficient may not be obtained. When the content is 1.0% by mass or more, the haze increases and transparency may be lowered. The content is more preferably 0.05 mass% or more and less than 0.9 mass%, and still more preferably 0.1 mass% or more and less than 0.8 mass%.

Next, a method of producing the biaxially oriented polypropylene film of the present invention will be described, but the present invention is not limited thereto.

First, the polypropylene raw material A was fed to a single-screw extruder for the A-layer, and the raw material in which the polypropylene raw material A and the polypropylene raw material B were dry blended at a ratio of 90:10 (mass ratio) was fed to the B- Thereby performing melt extrusion. Then, the foreign matters and the modified polymer were removed with a filter installed in the middle of the polymer tube, and then laminated so as to have a lamination thickness ratio of 1/4 to 1/200 in the multi-manifold type A-layer / B-layer composite T- And a laminated unoriented sheet having a layer structure of the A layer / B layer is obtained. Here, the lamination structure may be a three-layer lamination structure of A layer / B layer / A layer, and the lamination thickness ratio (ratio of individual A layer and B layer) at that time is also preferably 1/4 to 1/200. At this time, the surface temperature of the cast drum is preferably 10 to 40 DEG C from the viewpoint of transparency. Further, it is preferable that the A layer comes into contact with the drum from the viewpoint of transparency. Further, the three-layer laminated structure of layer A / layer B / layer A may be used. As a method of closely contacting the casting drum, any one of an electrostatic application method, a contact method using surface tension of water, an air knife method, a press roll method or an underwater casting method may be used. However, The air knife method is preferred. The air temperature of the air knife is preferably 0 to 50 ° C, preferably 0 to 30 ° C, and the jet air speed is preferably 130 to 150 m / s. In order to improve the uniformity in the width direction, . Further, in order to prevent the film from being vibrated, it is preferable to appropriately adjust the position of the air knife so that air flows to the film downstream side.

Further, by forcibly cooling the surface of the non-casting drum of the film after the film is brought into close contact with the casting drum, generation of crystal of the uncasted drum surface can be suppressed and the haze of the film can be reduced or the smoothness can be improved . In particular, when the thickness of the film is large, even if the temperature of the casting drum is set to be low, and the β crystal of the casting drum surface of the film is reduced, the temperature of the uncasted drum surface is not abruptly lowered, Which may lead to deterioration of haze and planarity. Since the temperature at which the &bgr; crystal is liable to be generated is 80 to 120 ° C, it is preferable that the noncasting drum surface of the film is forcibly cooled to 80 ° C or less after it is brought into close contact with the casting drum. The time for lowering to 80 占 폚 or lower is preferably within 5 seconds after casting, and more preferably within 4 seconds. The cooling method of the uncasting drum surface may be any one of an air knife method, a press roll method and an underwater casting method. However, it is preferable to use an air knife method which is simple in facility, easy in surface roughness control, and excellent in smoothness.

The obtained unstretched sheet is cooled in air and then introduced into a longitudinal stretching process. In the longitudinal stretching step, the non-stretched sheet is first brought into contact with a plurality of metal rolls maintained at a temperature of 120 ° C or more and less than 150 ° C, and the temperature is raised to the stretching temperature. In this preheating step, , It is preferable from the viewpoint of improvement of transparency. Specifically, for example, in the case where there are six preheating rolls, the temperature is gradually raised by setting the first temperature at 100 ° C and the second temperature at 140 ° C, and the third and fourth temperatures are set at 155 ° C, And the conditions are such that both sides are in contact with the rolls in succession, and the fifth and sixth rolls are set at 140 DEG C and preheated to the stretching temperature. The reason why transparency is improved by the above-described method is considered as follows. On the surface of the unstretched sheet after casting, minute β crystals exist after being air-cooled in the air. However, in the succeeding longitudinal stretching process and transverse stretching process, β crystals are cleaved to form fibrils, which causes haze, In some cases. In the preheating step of longitudinal stretching, the surface of the unstretched film is once brought into contact with the metal roll at 150 to 170 DEG C so that the? Crystals of the surface of the unstretched film can be transferred to the? Crystals, and the resulting biaxially oriented polypropylene film It is believed that the transparency of the film is improved. After being once contacted with a metal roll at 150 to 170 캜, the roll is preheated to a stretching temperature by a roll maintained at 120 캜 or more and less than 150 캜, stretched 3 to 8 times in the longitudinal direction, and then cooled to room temperature. If the stretching temperature is 150 占 폚 or more, the orientation of the film is weakened and the strength may be lowered. If the stretching ratio is less than 3 times, the orientation of the film is weakened and the strength may be lowered.

Subsequently, the longitudinal uniaxially stretched film is led to a tenter, and the end of the film is held by a clip, and the transverse stretching is performed at a temperature of 140 to 165 DEG C in the width direction by 7 to 13 times. If the stretching temperature is low, the film may be broken or the transparency may be deteriorated. If the stretching temperature is too high, the orientation of the film may be weak and the strength may be lowered. If the magnification is high, the film may be broken. If the magnification is low, the orientation of the film may be weak and the strength may be lowered.

According to the present invention, in the subsequent heat treatment and relaxation processing steps, while relaxing in the width direction in the width direction with the clip, relaxation is performed at a relaxation rate of 2 to 20% in the width direction, ), The heat treatment is carried out in a multistage manner so as to perform the heat fixing (the second step) under the condition of exceeding the above-mentioned heat fixing temperature and below the transverse stretching temperature while gripping the transverse direction by the clip, From the viewpoint of compatibility.

The relaxation ratio is more preferably 5 to 18%, and still more preferably 8 to 15% from the viewpoint of obtaining thermal dimensional stability. If the content exceeds 20%, the film may be excessively stretched in the tenter, and wrinkles may enter the product. If the relaxation rate is less than 2%, the thermal dimensional stability may not be obtained.

The first stage heat treatment / relaxation temperature is more preferably 100 ° C or more and less than 130 ° C, and more preferably 110 ° C or more and less than 130 ° C. At a heat treatment temperature of less than 100 占 폚, the film is not sufficiently relaxed, heat shrinkage becomes large, or the film flakes and wrinkles sometimes enter. On the other hand, in the case of heat treatment at 130 占 폚 or higher, since the molecular chain orientation relaxation proceeds, the strength of the film may be lowered.

Since the second-stage heat treatment temperature is higher than the first-stage heat treatment temperature and lower than the first-stage heat treatment temperature + 30 占 폚, the amorphous molecular chain having a high mobility insufficient mobility in the first- High strength and low heat shrinkage. From this viewpoint, the second-stage heat treatment temperature is more preferably a first-stage heat treatment temperature + 5 ° C or higher, a first-stage heat treatment temperature + 25 ° C or lower, more preferably a first- More preferred is a treatment temperature + 15 ° C or less.

After the heat treatment in the multistage mode, the tape is guided to the outside of the tenter through a cooling process at 80 to 100 DEG C while gripping the tape in the transverse direction with a clip, releasing the clip of the film end, slitting the film edge portion in the winder process , And a roll of film product is wound.

 The biaxially oriented polypropylene film of the present invention thus obtained can be used for various purposes such as packaging films, release films, process films, sanitary products, agricultural products, building products, medical supplies, And can be preferably used as a film for a flat panel display such as a retardation film or a polarizer protective film, a film for a manufacturing process such as a display, or an element for a film capacitor because of its excellent transparency.

When the biaxially oriented polypropylene film of the present invention is used as a film for flat panel display, the biaxially oriented polypropylene film of the present invention can be bonded to at least one side of the polarizer and used as a polarizing plate. When used as a retardation film, it can be used by providing the biaxially oriented polypropylene film of the present invention at a predetermined angle on the outside of the liquid crystal cell, the polarizer and the polarizer. For example, the above-described retardation film or polarizing plate may be disposed on both surfaces of a liquid crystal panel, and the light source may be used as a liquid crystal display.

When the biaxially oriented polypropylene film of the present invention is used as a film for a capacitor, a metal film is first formed on the surface. A method for forming a metal film laminated film by forming a metal film is not particularly limited. For example, a method of depositing aluminum on at least one side of a polypropylene film to form a metal film such as an aluminum evaporated film to be an internal electrode of the film capacitor Is preferably used. At this time, other metal components such as nickel, copper, gold, silver, chromium and zinc may be deposited simultaneously or sequentially with aluminum. Further, a protective layer may be formed on the vapor deposition film with oil or the like.

In the present invention, if necessary, after the metal film is formed, the metal film laminated film can be annealed at a specific temperature or subjected to heat treatment. Further, at least one surface of the metal film laminated film may be coated with polyphenylene oxide or the like for insulation or other purposes.

The metal film laminated film thus obtained can be laminated or wound by various methods to obtain a film capacitor. A preferred manufacturing method of the wound film capacitor is as follows.

Aluminum is vapor deposited on one side of the polypropylene film under reduced pressure. At this time, the film is deposited in a stripe shape having a margin portion extending in the longitudinal direction of the film. Next, a tape-like take-up reel is prepared in which a blade is slit by putting a blade at the center of each vapor deposition portion on the surface and the center of each margin portion, and the surface has a margin on one side. A tape-shaped take-up reel having a margin on the left side or right side is wound by overlapping two pieces of the left margin and the right margin one by one in the width direction so that the vapor deposition portion is evacuated from the margin portion.

In the case of depositing on both sides, the deposition is performed in the form of a stripe having a margin portion extending in the longitudinal direction of one surface, and the deposition is performed in a stripe shape so as to be located at the center of the side deposition portion. Next, a blade is slit by inserting a blade in the center of the margin of each of the front and rear sides, and a tape-like take-up reel having both sides of one side margin (for example, margins on the left side if there is a margin on the right side of the surface) is produced. One each of the obtained customized films of reels and non-deposited films is rolled by overlapping two sheets of metal film in the width direction so as to be outwardly projected from the fitting film, thereby obtaining a rolled body.

 The core material is removed from the winding body manufactured as described above, pressed, and the metallic wire is sprayed on the both end faces to form an external electrode, and a lead wire is welded to the metallic wire to obtain a wound film capacitor. The film capacitor is used for various purposes such as a railroad car, an automobile (hybrid car, an electric car), a photovoltaic power generator, a wind power generator, and a general household appliance, and the film capacitor of the present invention can be suitably used for these applications. have.

Example

Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) film thickness

Five points were measured using a micro thickness meter (manufactured by ANRITSU CO., LTD.) And the average value was obtained.

(2) The tensile modulus (E _MD , E _TD ) in the longitudinal direction and the width direction

The biaxially oriented polypropylene film was cut into a rectangle having a test direction length of 150 mm and a width of 10 mm to form a sample. Measurement was carried out five times in an atmosphere of 25 DEG C and 65% RH in accordance with the method specified in JIS K 7127: 1999 using a tensile tester (Orientech Tensilon AMF / RTA-100), and the average value was determined. However, the point at which the load passed 1 N after the start of the test was set as the origin of the elongation at an initial chuck distance of 50 mm and a tensile speed of 300 mm / min.

(3) The total haze of the film

The biaxially oriented polypropylene film of the present invention was measured for haze value (%) at 23 ° C three times in accordance with JIS K 7136: 2000 using a haze meter (NDH-5000, manufactured by Nippon Denshoku Kogyo K.K.) , And the mean value was used.

(4) Surface roughness of the film (SRa, SRz)

The biaxially oriented polypropylene film was measured under the following measurement conditions based on JIS B 0601: 2001 using a surface roughness meter (SURFCORDER ET4000A: Kosaka Gensho Co., Ltd.), and the center average surface roughness SRa (nm ) And a 10-point average roughness SRz (nm). However, the measurement was made at three points with respect to the surface contacting the cast drum at the time of extrusion, and the average value was obtained.

<Measurement Conditions>

Measuring speed: 0.1mm / S

Measurement range: 1000 占 퐉 in the longitudinal direction, 400 占 퐉 in the width direction

Measurement pitch: 1 占 퐉 in the longitudinal direction, 5 占 퐉 in the width direction

Cut-off value lambda c: 0.2 mm

Radius of stylus tip: 0.5㎛

(5) In-plane retardation and thickness retardation (Ret, Rth)

The in-plane retardation and the thickness direction retardation for a light beam having a wavelength of 548.3 nm were measured using an automatic birefringence system (KOBRA-21ADH) manufactured by Oji Keisuke Co., Ltd.

(6) Heat shrinkage rate after treatment at 85 ° C for 100 hours in the longitudinal and transverse directions

Five specimens having a width of 10 mm and a length of 200 mm (measuring direction) were cut out for each of the longitudinal direction and the width direction of the film, and a mark was drawn at a position of 25 mm from both ends in the form of a bar chart. The distance between the bar charts was measured with a universal projector, and a length (l _0). Then, the test piece was put in a paper, taken out in an oven kept at 85 캜 under a load of 0, heated for 100 hours, cooled at room temperature, and then measured with a universal projector to measure a dimension ( ₁₁ ) The average of the five values was defined as the heat shrinkage ratio.

Heat shrinkage rate = {(l ₀ -l ₁ ) / l ₀ } x 100 (%)

(7) Coefficient of static friction μs

The initial rising resistance value when the MD side was rubbed against each other so that one side of the film and the back side of the film were in contact with each other was measured according to ASTM-D1894 (1999) using a Toyo Tester high-friction meter and the maximum value was stopped Friction coefficient μs. However, measurement was impossible when the initial rise was large and exceeded the upper limit of the measured value (5.0). The sample was cut into 5 sets (10 pieces) with a width of 80 mm and a length of 200 mm. The measurement was carried out five times, and an average value was obtained.

(8) Melting point of the film Tm

5 mg of the biaxially oriented polypropylene film was taken as a sample in a pan made of aluminum and measured using a differential scanning calorimeter (RDC220 manufactured by Seiko Denshi Kogyo). First, the temperature is raised from the room temperature to 260 ° C at 10 ° C / min under a nitrogen atmosphere (first run), held for 10 minutes, and then cooled to 20 ° C at 10 ° C / min. After maintaining the temperature for 5 minutes, the melting peak temperature observed when the temperature was raised again (second run) at 10 ° C / min was defined as the melting point Tm of the film.

(Example 1)

TF850H, intrinsic viscosity [侶]: 1.8 dl / g, MFR: 2.9 g / 10 min, isotactic index: 96% as crystalline polypropylene raw material for surface layer (A) ) Was fed to the single-layer melt-extruder for layer A, and 90 parts by mass of the crystalline PP (a) and the low stereoregularity PP (b) (manufactured by Idemitsu Kosan Co., Ltd.) , Elmodu S901, MFR: 50 g / 10 min, molecular weight distribution Mw / Mn: 2, melting point: 80 占 폚) were dry-blended and fed to a single-shaft melt extruder for layer B and melt extruded at 240 占 폚, After removing foreign matters with a sintered filter of a cut, it was laminated at a thickness ratio of 1/8/1 in a feed block type A / B / A composite T-die and discharged to a cast drum controlled at a surface temperature of 30 캜 to obtain a cast sheet . Subsequently, preheating was performed at 140 占 폚 using seven ceramic rolls (the roll temperature was 100 占 폚 for the first roll, 125 占 폚 for the second roll, and 140 占 폚 for the third roll and the seventh roll) . Next, the end was gripped and introduced into a tenter-type stretching machine, preheated at 170 DEG C for 3 seconds, and then stretched at 165 DEG C to 8.0 times. In the subsequent heat treatment process, heat treatment at 120 占 폚 was carried out while imparting 10% relaxation in the width direction as the first-stage heat treatment and relaxation treatment, and as a second-stage heat treatment, And heat treatment was performed for 3 seconds. Thereafter, the film was cooled at 100 DEG C to the outside of the tenter, and the clip of the film end was released, and the film was wound around the core to obtain a biaxially oriented polypropylene film having a thickness of 12 mu m. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Example 2)

A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that the temperature of the fourth and fifth of the seven ceramic rolls in the longitudinal stretching step of Example 1 was set to 155 캜. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Example 3)

A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that in the heat treatment step of Example 1, the relaxation rate was 15%. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Example 4)

TF850H, intrinsic viscosity [侶]: 1.8 dl / g, MFR: 2.9 g / 10 min, isotactic index: 96% as crystalline polypropylene raw material for surface layer (A) ) Were fed to the single-layered single-screw extruder for layer A and 85 parts by mass of the crystalline PP (a) and a low stereoregularity PP (b) (trade name, manufactured by Idemitsu Kosan Co., Ltd.) , Elmordy S901, MFR: 50 g / 10 min, molecular weight distribution Mw / Mn: 2, melting point: 80 占 폚) were dry-blended and fed to a single-shaft melt extruder for the B layer and melt extruded at 240 占 폚, After removing foreign matters with a sintered filter of a cut, the sheet was laminated with a thickness ratio of 1/10/1 in a feed block type A / B / A composite T-die and discharged to a cast drum controlled at a surface temperature of 30 ° C, . Subsequently, preheating was performed at 140 占 폚 using seven ceramic rolls (the roll temperature was 100 占 폚 for the first roll, 125 占 폚 for the second roll, and 140 占 폚 for the third roll and the seventh roll) . Next, the end was gripped and introduced into a tenter-type stretching machine, preheated at 170 DEG C for 3 seconds, and then stretched at 165 DEG C to 8.0 times. In the subsequent heat treatment process, heat treatment at 120 占 폚 was carried out while imparting 10% relaxation in the width direction as the first-stage heat treatment and relaxation treatment, and as a second-stage heat treatment, And heat treatment was performed for 3 seconds. Thereafter, the film was cooled at 100 DEG C to the outside of the tenter, the clip of the end of the film was released, and the film was wound around the core to obtain a biaxially oriented polypropylene film having a thickness of 12 mu m. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Example 5)

First, 99.3 parts by mass of crystalline PP (a) (TF850H, manufactured by Prime Polymer Co., MFR: 2.9 g / 10 min.) And silica particles treated with a surface silane coupling agent (SFP-20MHE manufactured by Denki Kagaku Kogyo Co., 0.5 parts by mass as an antioxidant, and IRGANOX1010 and IRGAFOS168 as antioxidants were added to a twin-screw extruder through a weighing hopper so that 0.1 part by mass of each of them was mixed at this ratio, and melt-kneaded at 260 DEG C, Discharged from the die in a strand shape, cooled and solidified in a water bath at 25 DEG C, and cut into chips to obtain a raw material for polypropylene for layer A (1).

As the polypropylene raw material for the surface layer (A), the polypropylene raw material (1) was fed to the single-layer uniaxial melt extruder for the layer A, and 90 parts by mass of the crystalline PP (a) 10 parts by mass of low stereoregularity PP (b) (Elmodew S901, manufactured by Idemitsu Kosan Co., Ltd., MFR: 50 g / 10 min, molecular weight distribution Mw / Mn: 2, melting point: 80 占 폚) Extruded at a temperature of 240 占 폚 to remove impurities with a 60 占 퐉 -cut sintered filter and then laminated at a thickness ratio of 1/15/1 in a feed block type A / B / A composite T-die, And discharged to a cast drum controlled at a surface temperature of 30 DEG C to obtain a cast sheet. Subsequently, preheating was performed at 140 占 폚 using seven ceramic rolls (the roll temperature was 100 占 폚 for the first roll, 125 占 폚 for the second roll, and 140 占 폚 for the third roll and the seventh roll) . Next, the end was gripped and introduced into a tenter-type stretching machine, preheated at 170 DEG C for 3 seconds, and then stretched at 165 DEG C to 8.0 times. In the subsequent heat treatment process, heat treatment at 120 占 폚 was carried out while imparting 10% relaxation in the width direction as the first-stage heat treatment and relaxation treatment, and as a second-stage heat treatment, And heat treatment was performed for 3 seconds. Thereafter, the film was cooled at 100 deg. C, guided to the outside of the tenter, released from the clips of the film end, and wound up on the core to obtain a biaxially oriented polypropylene film having a thickness of 12 mu m. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Example 6)

The above polypropylene raw material (1) was fed to the single-layer uniaxial melt extruder as the raw material for the surface layer (A), and the crystalline PP (a) was used as a raw material for the core layer (B) Extruded at 240 占 폚 to remove impurities with a 60 占 퐉 cut sintered filter and then laminated at a thickness ratio of 1/30/1 in a feed block type A / B / A composite T-die, To form a cast sheet. After casting, the cast sheet was cooled by spraying air with air at a temperature of 30 DEG C and a pressure of 0.3 MPa on the surface of the uncooled drum of the cast sheet to obtain a cast sheet. The temperature of the non-casting drum surface after 4 seconds from the casting was 75 deg. Subsequently, preheating was performed at 140 占 폚 using seven ceramic rolls (the roll temperature was 100 占 폚 for the first roll, 125 占 폚 for the second roll, and 140 占 폚 for the third roll and the seventh roll) . Next, the end was gripped and introduced into a tenter-type stretching machine, preheated at 170 DEG C for 3 seconds, and then stretched at 165 DEG C to 8.0 times. In the subsequent heat treatment process, heat treatment at 120 占 폚 was carried out while imparting 10% relaxation in the width direction as the first-stage heat treatment and relaxation treatment, and as a second-stage heat treatment, And heat treatment was performed for 3 seconds. Thereafter, the film was cooled at 100 deg. C, guided to the outside of the tenter, released from the clip of the film end, and the film was wound around the core to obtain a biaxially oriented polypropylene film having a thickness of 25 mu m. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Comparative Example 1)

In the same manner as in Example 1 except that the crystalline PP (a) was used as the polypropylene raw material for the core layer (B) (the same raw material was used for the surface layer and the core layer) in Example 1, To obtain an oriented polypropylene film. The crystallinity of the raw material was high and the transparency deteriorated. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Comparative Example 2)

Except that 50 parts by mass of the crystalline PP (a) as the polypropylene raw material for the core layer (B) and the syndiotactic PP (c) (syndiotactic pentad fraction: 0.92, MFR: 3.5 g / Min) was dry-blended and fed to the uniaxial melt extruder for layer B. A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except for the above. The crystallinity and heat resistance of the raw material were low and the transparency was improved, but the strength and heat shrinkage deteriorated. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Comparative Example 3)

In the heat treatment step of Example 4, heat treatment was performed at 145 占 폚 while imparting 10% relaxation in the width direction as the first-stage heat treatment and relaxation treatment. In the same manner as in Example 4, To obtain an oriented polypropylene film. Since the temperature at the time of relaxation was high, the orientation relaxation progressed and the strength of the film deteriorated. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Comparative Example 4)

A biaxially oriented polypropylene film was obtained in the same manner as in Example 4 except that in the transverse stretching step of Example 4, the transverse stretch magnification was 5.5 times. The thickness of the obtained film was 17 占 퐉. The stretching magnification was low, so the alignment was weak and the strength of the film deteriorated. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Comparative Example 5)

A biaxially oriented polypropylene film was obtained in the same manner as in Example 6 except that no cooling by air was performed after casting in Example 6. The thickness of the obtained film was 25 占 퐉. Since no cooling was performed, the haze and planarity of the film deteriorated. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Comparative Example 6)

The same polypropylene raw material (1) as used for the surface layer (A) was used for the polypropylene raw material for the core layer (B) in Example 6, Axis oriented polypropylene film was obtained. The thickness of the obtained film was 25 占 퐉. The haze of the film deteriorated because particles were contained in the whole layer. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

(Comparative Example 7)

In Example 5, 1.25 parts by mass of a silica particle Silton AMT-20S (particle diameter 1.7 탆, no surface treatment) manufactured by Mizusawa Chemical Industries, Ltd. was used in place of the silica particles SFP-20MHE manufactured by Denki Kagaku Kogyo Co., A biaxially oriented polypropylene film was obtained in the same manner as in Example 5 except for the above. The thickness of the obtained film was 12 占 퐉. At the time of stretching, voids were generated at the interface between the particles and the polypropylene, and the haze of the film deteriorated. Table 1 shows the physical properties and evaluation results of the biaxially oriented polypropylene film.

Claims (11)

The value of the sum of the tensile elastic modulus E _MD in the longitudinal direction of the film and the tensile elastic modulus E _TD in the transverse direction of E _{MD + TD} is 4.5 GPa or more, the total haze is 1% or less, and the heat shrinkage rate after treatment at 85 캜 for 100 hours is A biaxially oriented polypropylene film having a longitudinal direction and a width direction of not more than 1.0% both in the film. The biaxially oriented polypropylene film according to claim 1, wherein the 10-point average roughness SRz of at least one surface is 500 nm or less. The biaxially oriented polypropylene film according to claim 1 or 2, wherein the center average surface roughness SRa of at least one side is 50 nm or less. The biaxially oriented polypropylene film according to any one of claims 1 to 3, wherein the in-plane retardation Ret of the film is 0.1 to 500 nm. The biaxially oriented polypropylene film according to any one of claims 1 to 4, wherein the retardation value Rth in the film thickness direction and the value Rth / Ret of the ratio of the in-plane retardation Ret of the film are 1 or less. The biaxially oriented polypropylene film according to any one of claims 1 to 5, wherein a static friction coefficient s between the one surface of the biaxially oriented polypropylene film and the back surface thereof is 0.5 or less. The biaxially oriented polypropylene film according to any one of claims 1 to 6, wherein the biaxially oriented polypropylene film has a melting point Tm of 158 캜 or higher. The biaxially oriented polypropylene film according to any one of claims 1 to 7, used as a film for a flat panel display. A flat panel display using the biaxially oriented polypropylene film according to claim 8. The biaxially oriented polypropylene film according to any one of claims 1 to 7, which is used as an element for a film capacitor. A film capacitor using the biaxially oriented polypropylene film according to claim 10.