JP6508043B2 - Biaxially oriented polypropylene film - Google Patents

Description

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

  A biaxially oriented polypropylene film is used for various applications such as packaging applications, mold release applications, tape applications, electrical applications such as cable wrapping and capacitors, etc. because it is excellent in transparency, mechanical properties, electrical properties, etc. .

  Furthermore, in recent years, studies have been carried out to develop the film for flat panel displays, such as a polarizer protective film and a retardation film, using the optical properties and productivity of a polypropylene film (for example, Patent Documents 1 and 2). However, in the case of a polypropylene film, the film surface may be roughened due to the β crystals of polypropylene produced during melt extrusion, and the haze of the film may be high, and the visibility may be reduced when used in display applications . In particular, in the biaxially stretched film, fibrils caused by β crystals are generated in the stretching step in the width direction, and the haze may be increased. In order to improve the transparency of the polypropylene film, it is necessary to lower the crystallinity of the polypropylene by using a polypropylene with low stereoregularity as a raw material, increasing the content of the polyethylene component, or adding a petroleum resin or the like. Although the method may be considered, the above components are generally soft components or low in heat resistance, so if the addition amount is large, the strength and heat resistance of the film may be lowered. Moreover, in the manufacturing method, in order to prevent the fall of transparency, although the method of setting it as unstretched or longitudinal uniaxial stretching is considered, there existed a case where the intensity | strength of a film fell. For example, in Patent Document 3, syndiotactic polypropylene is used as a raw material, and a cooling roll after extrusion is cooled to suppress crystal formation of an unstretched sheet, and uniaxially stretch in the longitudinal direction in a range of 1 to 4 times An example is described which improves the transparency of polypropylene films. Since these polypropylene films use syndiotactic polypropylene with low crystallinity as a raw material, and also have a low draw ratio and further uniaxial stretching, the film strength may be insufficient. In the film for flat panel displays, for example, when laminating the polarizer and the film of the present invention when the film strength is insufficient, the film is deformed by the tension of the device, the retardation changes, and the color tone of the display There was a case where it shifted. In addition, there was a case where the withstand voltage decreased in the capacitor application.

  Patent Documents 4 and 5 disclose examples in which the strength and transparency of a polypropylene film are compatible. However, both strength and transparency were insufficient for use in flat panel displays.

JP, 2013-152455, A JP, 2010-164733, A JP, 2010-195993, A Japanese Patent Application Publication No. 2003-170485 JP, 2009-012225, A

  An object of the present invention is to solve the above-mentioned problems. That is, to provide a biaxially oriented polypropylene film which is high in strength, low in heat yield and excellent in transparency, and can be suitably used as a film for a manufacturing process such as a film for flat panel display or display or a film for a capacitor. is there. In the present invention, the term "strength" refers to the strength of a property that is not easily deformed, and a tensile elastic modulus is used as an index. That is, in the present specification, high strength indicates that the tensile modulus is high.

In order to solve the problems described above and achieve the object, the biaxially oriented polypropylene film of the present invention comprises particles having an average particle diameter of 0.1 μm or more and less than 1.0 μm in the surface layer of at least one side, Sum of elastic modulus E _MD in the direction and tensile modulus E _TD in the width direction E _{MD + TD} value is 4.5 GPa or more, total haze is 1% or less, and thermal contraction rate after 100 ° C. treatment at 85 ° C. The film is characterized in that both the longitudinal direction and the width direction are 1.0% or less, and the ten-point average roughness SRz of at least one side is 500 nm or less.

  The biaxially oriented polypropylene film of the present invention has high strength, low heat recovery, and excellent transparency, so it can be suitably used as a film for a flat panel display, a film for a manufacturing process such as a display, or a film for a capacitor. it can.

Biaxially oriented polypropylene film of the present invention, the value of the sum _{E MD + TD} tensile modulus _{E TD} in the tensile elastic modulus _{E MD} and the width direction in the longitudinal direction of the film is not less than 4.5 GPa. When it is used as a film for flat panel displays that the value of E _{MD + TD} is less than 4.5 GPa, for example, when bonding the polarizer and the film of the present invention together, the film is deformed by the tension of the device and the retardation changes As a result, the color tone of the display may be shifted. In addition, the withstand voltage may decrease in capacitor applications. The value of E _{MD + TD} is more preferably 5.0 GPa or more, still more preferably 5.5 GPa or more, and most preferably 6.0 GPa or more. The higher the value of E _{MD + TD} , the better, but the upper limit is about 20 GPa, more preferably 10 GPa or less, and still more preferably 7 GPa or less. _Further, values of and _{E TD} of _{E MD} is preferably both 2GPa or more. Even when the value of E _{MD + TD} is 4.5 GPa or more, when there is a certain difference or more in the tensile modulus in the longitudinal direction and the width direction, the handleability may be deteriorated such as tearing of the film. In order to make the value of E _{MD + TD} into the above range, the raw material composition of the film is set to the range described later, and a highly transparent film is obtained while reducing the soft components such as low stereoregular polypropylene. Preferably, the film is stretched at a high magnification to obtain a biaxially oriented polypropylene film.

The biaxially oriented polypropylene film of the present invention preferably has an E _MD / E _TD value of 0.5 or more and 2.0 or less. If the value of E _MD / E _TD is out of the above range, the balance of orientation of the biaxially oriented polypropylene film may be deteriorated, and the film may be easily torn during handling. The value of E _MD / E _TD is more preferably 0.55 or more and 1.5 or less, still more preferably 0.57 or more and 1.2 or less. In order to make the value of E _MD / E _TD into the above-mentioned range, it is preferable to obtain a biaxially oriented polypropylene film by setting the stretching condition and the heat setting condition of MD and TD as described later.

  In the present application, a direction parallel to the film forming direction is referred to as a film forming direction, a longitudinal direction or an MD direction, and a direction perpendicular to the film forming direction in the film plane 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. When the total haze exceeds 1%, the visibility of the display may decrease when used as a film for a flat panel display. In addition, in a capacitor application, particularly when a thin film of 2 μm or less is formed, film breakage may occur when depositing a metal layer. It is considered that this is because the microvoids inside the film generated due to the β crystals of polypropylene are the cause of the film breakage. The total haze is more preferably 0.8% or less, still more preferably 0.5% or less. The total haze is preferably as low as possible from the viewpoint of transparency, but substantially the lower limit is about 0.05%.

  In order to make all the haze into the said range, it is preferable to make the raw material composition of a film into the range mentioned later, and to make casting conditions and longitudinal stretching conditions into the range which are mentioned later, and to reduce the beta crystal of a cast sheet.

  In the biaxially oriented polypropylene film of the present invention, the thermal shrinkage after treatment at 85 ° C. for 100 hours is 1.0% or less in both the longitudinal direction and the width direction of the film. When the heat shrinkage ratio exceeds 1.0%, when the flat panel display is used at high temperature, the shrinkage stress of the film causes the film to peel off, the visibility decreases, and the shrinkage stress of the film changes the retardation. May change. In a capacitor application, the heat of the capacitor manufacturing process and use process causes shrinkage of the film itself, and the voltage resistance may decrease due to a contact failure with the element end metallikon. The thermal shrinkage is more preferably 0.5% or less, still more preferably 0.3% or less, and most preferably 0.1% or less. The lower limit is not particularly limited, but the film may expand too much, and the lower limit is substantially about -1.0%. In order to make the heat shrinkage ratio into the above range, the raw material composition is in the range described later, and the addition amount of the low melting point component is reduced as much as possible while maintaining the transparency, longitudinal stretching condition, lateral stretching condition, thermal condition It is preferable to reduce heat collection while maintaining the strength while keeping the fixing condition and the relaxing condition in the range described later.

  The biaxially oriented polypropylene film of the present invention preferably has a ten-point average roughness SRz of 500 nm or less on at least one side. When it is used as a film for flat panel displays as SRz of at least one side is 500 nm or less, the visibility of the display can be made higher. 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. The lower the SRz of at least one side, the better, but the lower limit is substantially about 1 nm. In order to make SRz into the said range, it is preferable to make the raw material composition of a film into the range mentioned later, and to make casting conditions and longitudinal stretching conditions into the range which are mentioned later, and to reduce the beta crystal of a cast sheet.

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

  The biaxially oriented polypropylene film of the present invention preferably has an in-plane retardation Ret of 0.1 to 500 nm. In flat panel display films, the retardation of the film is different depending on the part used, and in optical isotropic films such as a polarizer protective film, retardations such as about 0.1 to 100 nm, 1⁄4 λ retardation films, etc. It is preferable that it is about 50-500 nm in a film. When the phase difference exceeds 500 nm, the color tone of the display may change. Moreover, in a capacitor application, the higher the phase difference, the higher the orientation of the film, and the higher the withstand voltage, which is preferable. In order to make the value of Ret into the above range, it is preferable to set the raw material composition, the longitudinal stretching condition, the transverse stretching condition, the heat setting condition, and the relaxation condition 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 Rth, the value of the ratio Rth / Ret to the above Ret is preferably 1 or less. In the flat panel display film, the viewing angle characteristics are improved when the value of Rth / Ret is 1 or less. The value of Rth / Ret is more preferably 0.8 or less, still more preferably 0.5 or less. The target value of Rth / Ret is appropriately set depending on the configuration of the display used, but about 0.1 is a controllable lower limit value. In order to set the value of Rth / Ret in the above range, it is preferable to set the raw material composition, the longitudinal stretching condition, the transverse stretching condition, the heat setting condition, and the relaxation condition within the ranges described later.

  The biaxially oriented polypropylene film of the present invention preferably has a coefficient of static friction μs between one surface of the film and its back surface of 0.5 or less. When the static friction coefficient μs exceeds 0.5, the film has poor slipperiness and handling becomes difficult, and wrinkles may be formed during film formation and post-processing, or the wound appearance of the product roll may be deteriorated. The coefficient of static friction μs is more preferably 0.45 or less, still more preferably 0.4 or less. The coefficient of static friction μs is preferably low from the viewpoint of handling, but in order to lower the coefficient of static friction μs, it is necessary to roughen the surface and the haze is increased to deteriorate transparency. About 1 is the lower limit. In order to set the static friction coefficient μs in the above range, it is preferable to set the raw material composition, the laminated constitution of the film, the longitudinal stretching condition, and the lateral stretching condition within the ranges described later.

  The biaxially oriented polypropylene film of the present invention preferably has a melting point Tm of 158 ° C. or more. If the melting point Tm is less than 158 ° C., the heat resistance may be insufficient and the thermal contraction rate may increase, or the tensile rigidity may decrease or a fish eye may easily occur because the ethylene component content is large. . The melting point Tm is more preferably 160 ° C. or more, still more preferably 163 ° C. or more. Although the melting point Tm of the biaxially oriented polypropylene film is preferably as high as possible from the viewpoint of reducing the heat shrinkage rate, the upper limit is practically about 180 ° C. In order to set the melting point Tm in the above range, the raw material composition is in the range described later, and in particular, the content of the ethylene component having low heat resistance is reduced, the longitudinal stretching condition, the lateral stretching condition, the heat setting condition, relaxation It is preferable to make conditions into the range mentioned later. In addition, in measurement by a differential scanning calorimeter, when two or more melting peak temperatures of a film are observed, let the peak temperature with the lowest temperature be melting point Tm of a biaxially oriented polypropylene film.

  The thickness of the biaxially oriented polypropylene film of the present invention is appropriately adjusted depending on the application and is not particularly limited, but preferably 0.5 μm or more and 100 μm or less. If the thickness is less than 0.5 μm, the handling may be difficult. If the thickness exceeds 100 μm, the thickness of the unstretched sheet becomes large, so the cooling speed on the cooling roll during extrusion becomes slow, Is likely to form and the haze of the film may be high. The thickness is more preferably 5 to 60 μm for flat panel display applications, and still more preferably 5 to 30 μm. It is preferable that it is 0.5-10 micrometers in a capacitor | condenser use, and it is still more preferable that it is 1-3 micrometers. The thickness can be adjusted by the screw rotation speed of the extruder, the width of the unstretched sheet, the film forming speed, the draw ratio, and the like within the range that does not deteriorate other physical properties.

  Next, preferred polypropylene raw materials for use in biaxially oriented polypropylene films will be described.

  In the biaxially oriented polypropylene film of the present invention, it is preferable to use at least two kinds of polypropylene raw materials (polypropylene raw material A and polypropylene raw material B). As the polypropylene raw material A, in order to improve the strength of the film, it is preferable to use a polypropylene raw material having high crystallinity, and as the polypropylene raw material B, a polypropylene raw material having low stereoregularity is used to improve the transparency of the film. Is preferred.

  The polypropylene raw material A is preferably a polypropylene having a cold xylene soluble portion (hereinafter CXS) of 4% by mass or less and a mesopentad fraction of 0.95 or more. If these conditions are not satisfied, the film formation stability may be poor, the strength of the film may be reduced, and the dimensional stability and voltage resistance may be greatly reduced.

  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, and has low stereoregularity, It is considered to be a component that is difficult to crystallize because of low molecular weight and the like. If a large amount of such components is contained in the resin, problems such as poor thermal dimensional stability of the film or a decrease in the dielectric breakdown voltage at high temperatures may occur. Accordingly, the content of CXS is preferably 4% by mass or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. The lower the CXS, the better, but the lower limit is about 0.1% by mass. In order to obtain such a CXS-containing polypropylene, methods such as a method of enhancing the catalytic activity when obtaining a resin, and a method of washing the obtained resin with a solvent or a propylene monomer itself can be used.

  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 mesopentad fraction is an index showing the stereoregularity of the crystalline phase of polypropylene measured by nuclear magnetic resonance method (NMR method), and the higher the value, the higher the degree of crystallinity and the higher the melting point, and it is at high temperature It is preferable because the dielectric breakdown voltage is high. The upper limit of the mesopentad fraction is not particularly limited. Thus, in order to obtain a resin having high stereoregularity, a method of washing a resin powder obtained with a solvent such as n-heptane, a method of selecting a catalyst and / or a cocatalyst, and appropriately selecting a composition, etc. It is preferably adopted.

  The polypropylene raw material A more preferably has a melt flow rate (MFR) of 1 to 10 g / 10 min (230 ° C., 21.18 N load), particularly preferably 2 to 5 g / 10 min (230 ° C., 21.18 N) The thing of the range of load) is preferable from a viewpoint of film forming property or film strength. In order to set the melt flow rate (MFR) to the above value, a method of controlling an average molecular weight or a molecular weight distribution is adopted.

  The polypropylene raw material A is mainly composed of a homopolymer of propylene, but may contain a copolymer component with other unsaturated hydrocarbon or the like as long as the object of the present invention is not impaired. Coalescing may be blended. For example, ethylene, propylene (in the case of a copolymerized blend), 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene as monomer components constituting such copolymer components or blends 1,1-Hexene, 4-methylpentene-1, 5-ethylhexene-1, 1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-ene Norbornene etc. are mentioned. The amount of copolymerization or the amount of blend is preferably less than 1 mol% in the amount of copolymerization and less than 10% by mass in the amount of the blend, from the viewpoint of resistance to dielectric breakdown and dimensional stability.

  Subsequently, the polypropylene raw material B will be described.

  The polypropylene raw material B is preferably a polypropylene raw material having low crystallinity and low stereoregularity in order to obtain good compatibility with the above-described polypropylene raw material A and to obtain high transparency. As such polypropylene raw material B, non-crystalline polypropylene, low stereoregular polypropylene, syndiotactic polypropylene, α-olefin copolymer, etc. can be used, but excellent transparency can be obtained with a small addition amount. Amorphous polypropylene and low stereoregular polypropylene are particularly preferred because they can

  As the non-crystalline polypropylene which is preferably used as the polypropylene raw material B, a polypropylene polymer having mainly atactic stereoregularity is preferably the main component, specifically, a homopolymer or a copolymer with an α-olefin. It can be mentioned. In particular, the latter, i.e., amorphous polypropylene-α-olefin copolymer is preferred. In the present application, the term "main component" means that the proportion of a specific component in all the components is 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, Preferably it is 95 mass% or more.

  The above amorphous polypropylene can be produced as a by-product of isotactic polypropylene during homopolypropylene polymerization. Because the glass transition temperature is lower compared to general polypropylene, it can be extracted as the boiling n-heptane (or xylene) soluble fraction of homopolypropylene. Alternatively, it is also possible to polymerize amorphous polypropylene independently by changing the catalyst and polymerization conditions applied at the time of production of crystalline polypropylene. The amorphous polypropylene preferably used in the present invention can be used without particular limitation as long as it is manufactured by a conventionally known manufacturing method. As the amorphous polypropylene having the characteristics as described above, commercially available products such as "Tough Selenium" manufactured by Sumitomo Chemical Co., Ltd. can be appropriately selected and used.

  When an amorphous polypropylene-α-olefin copolymer is used as the amorphous polypropylene in the present invention, examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene 4-methyl 1-pentene or propylene-ethylene-1-butene is preferable.

  Moreover, as the non-crystalline polypropylene-α-olefin copolymer using such α-olefin, a propylene / ethylene copolymer, a propylene / ethylene · 1-butene copolymer, a propylene-1-butene copolymer And propylene / ethylene / cyclic olefin copolymer, propylene / ethylene / butadiene copolymer and the like.

  The low stereoregular polypropylene which is preferably used as the polypropylene raw material B is preferably a homopolymer of propylene which is produced using a metallocene catalyst as a polymerization catalyst. The melting point of the low stereoregular polypropylene is 100 ° C. or less, more preferably 60 to 90 ° C., and particularly preferably 65 to 85 ° 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 low stereoregular polypropylene which has the above characteristics, commercial items, such as "El Modhu" by Idemitsu Kosan Co., Ltd., can be used, selecting it suitably.

  The biaxially oriented polypropylene film of the present invention may contain branched polypropylene H in addition to the above-described polypropylene raw material A and polypropylene raw material B from the viewpoint of strength improvement and withstand voltage improvement. When it is added, it is preferably 0.05 to 10% by mass, more preferably 0.5 to 8% by mass, and still more preferably 1 to 5% by mass. By containing the branched polypropylene H, it is possible to control the size of the spherulite formed in the cooling step of the melt-extruded resin sheet small, and a polypropylene film excellent in transparency and strength can be obtained.

As said branched polypropylene H, what has a melt flow rate (MFR) in the range of 1-20 g / 10min is preferable from a viewpoint of film forming property, and what is in the range of 1-10 g / 10 min is more preferable preferable. The melt tension is preferably in the range of 1 to 30 cN, and more preferably in the range of 2 to 20 cN. In addition, the branched polypropylene H as used herein is a polypropylene having five or less internal trisubstituted olefins in 10,000 carbon atoms. The presence of this internal trisubstituted olefin can be confirmed by the proton ratio of the ¹ H-NMR spectrum.

  In the biaxially oriented polypropylene film of the present invention, the content of the ethylene component contained in the polymer constituting the film is preferably 10% by mass or less. More preferably, it is 5% by mass or less, still more preferably 3% by mass or less. As the content of the ethylene component increases, the crystallinity is lowered and the transparency is easily improved. However, when the content of the ethylene component exceeds 10% by mass, the strength is lowered and the heat resistance is lowered to cause heat The contraction rate may be deteriorated.

  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, it is 3% by mass or less, more preferably 1% by mass or less, and it is most preferable not to contain a petroleum resin. By adding a petroleum resin, transparency and strength can be improved, but if the content of petroleum resin exceeds 5% by mass, the heat resistance decreases to deteriorate the heat shrinkage rate, and also the raw material cost May be higher.

  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% by mass or less. More preferably, it is 3% by mass or less, more preferably 1% by mass or less, and it is most preferable that no cycloolefin polymer is contained. By adding a cycloolefin polymer, heat resistance and strength can be improved, but when the content of the cycloolefin polymer exceeds 5% by mass, the transparency is lowered due to the problem of compatibility with polypropylene and the haze is It may deteriorate or the cost of raw materials may increase.

  It is preferable that content of the polypropylene polymer contained in the polymer which comprises a film from a viewpoint of transparency, heat resistance, and intensity | strength of the biaxially-oriented polypropylene film of this invention is 95 mass% or more. More preferably, it is 96 mass% or more, still more preferably 97 mass% or more, and most preferably 98 mass% or more.

  The polypropylene raw material of the present invention contains various additives such as crystal nucleating agent, antioxidant, heat stabilizer, slip agent, antistatic agent, antiblocking agent, filler, viscosity, as long as the object of the present invention is not impaired. Modifiers, color inhibitors and the like can also be contained.

  Among these, selection of the type and addition amount of the antioxidant is important from the viewpoint of long-term heat resistance. That is, as such an antioxidant, it is preferable to use a steric hindrance-type phenol-based one, and at least one of them is a high molecular weight one having a molecular weight of 500 or more. Although various things are mentioned as the specific example, For example, 1, 3, 5- trimethyl- 2, 4, 6- with 2, 6- di- t- butyl- p- cresol (BHT: molecular weight 220.4) Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (for example Irganox® 1330 from BASF: molecular weight 775.2) or tetrakis [methylene-3 (3,5-di-t-) It is preferable to use in combination with butyl-4-hydroxyphenyl) propionate] methane (for example, Irganox (registered trademark) 1010 manufactured by BASF, Inc .: molecular weight 1177.7) and the like. The total content of these antioxidants is preferably in the range of 0.03 to 1.0% by mass with respect to the total amount of polypropylene. If the amount of the antioxidant is too small, the polymer may be deteriorated in the extrusion step to cause the film to be colored or the long-term heat resistance may be poor. If the amount of the antioxidant is too large, the transparency may be reduced due to the bleeding out of these antioxidants. A more preferable content is 0.1 to 0.9% by mass, and particularly preferably 0.2 to 0.8% by mass.

  A crystal nucleating agent can be added to the polypropylene raw material of the present invention as long as the object of the present invention is not violated. As described above, branched polypropylene (H) already has a nucleating agent effect of α crystals or β crystals by itself, but other α crystals nucleating agents (dibenzylidene sorbitols, sodium benzoate etc. And β crystal nucleating agents (amide compounds such as potassium 1,2-hydroxystearate, magnesium benzoate, N, N'-dicyclohexyl-2,6-naphthalenedicarboxamide, quinacridone compounds, etc.) and the like. . However, excessive addition of the above-mentioned other nucleating agent may cause reduction in transparency and strength due to reduction in stretchability and void formation, so the addition amount is usually 0.5% by mass or less, preferably 0.1 It is preferable to set the content to not more than mass%, more preferably not more than 0.05 mass%, and it is most preferable not to add.

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

  Next, the structure of the film using the said polypropylene raw material is demonstrated.

  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 recovery.

  In the biaxially oriented polypropylene film of the present invention, at least one layer (hereinafter referred to as I layer) in the laminated constitution preferably contains 96 mass% or more of polypropylene raw material A from the viewpoint of high strength and low heat recovery. The content of the polypropylene raw material A in the layer I is more preferably 97% by mass or more, still more preferably 98% by mass or more. If the content of the polypropylene raw material A in the layer I is less than 96% by mass, the orientation of the film is lowered and the strength is lowered, or the heat recovery is increased when the additive component having low heat resistance is large. There is a case.

  Further, in the biaxially oriented polypropylene film of the present invention, at least one layer (hereinafter referred to as layer II) in the laminated constitution has a mixing ratio of polypropylene raw material A and polypropylene raw material B from the viewpoint of transparency and low heat recovery. It is preferable that they are 50: 50-95: 5 (mass ratio. The same below). More preferably, they are 60: 40-95: 5, More preferably, they are 70: 30-93: 7. When the mixing ratio of the polypropylene raw material B in the layer II exceeds 50, the strength and the heat resistance may decrease. If the ratio is less than 5, the stereoregularity of the unstretched film may be too high, and the transparency may decrease during stretching.

  The biaxially oriented polypropylene film of the present invention has a laminated structure of at least two layers, and it is preferable that at least one layer of each of the above-described I layer and II layer is included. The lamination thickness ratio of the I layer in the film thickness direction is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, and most preferably 2% or more. The lamination 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.

  Moreover, it is preferable that the biaxially-oriented polypropylene film of this invention contains particle | grains (henceforth a slippery particle) in the surface layer of at least one side among the laminated structure mentioned above from a viewpoint of a friction coefficient reduction. The slippery particles are not particularly limited as long as they do not impair the effects of the present invention, and as inorganic particles, silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black, zeolite particles, etc. organic particles Are used for the synthesis of acrylic resin particles, styrene resin particles, polyester resin particles, polyurethane resin particles, polycarbonate resin particles, polyamide resin particles, silicone resin particles, fluorine resin particles, or the above resin The copolymer resin particle etc. of 2 or more types of monomers can be mentioned. However, since polypropylene resin has a low surface energy, when adding and stretching particles, the particle interface exfoliates at the time of stretching and a void is generated, and the haze may increase to lower the transparency. From the viewpoint of improving transparency, it is preferable to use the above-mentioned inorganic particles or organic particles having a silane coupling treatment on the surface, and in particular, silica particles having a silane coupling treatment are preferable.

  The average particle size of the slippery particles is preferably 0.1 μm or more and less than 1.0 μm. When the average particle size is less than 0.1 μm, the particles may aggregate to become coarse particles, and the transparency may be reduced. When the average particle size is 1.0 μm or more, voids are easily generated at the particle interface during stretching, and the transparency may be reduced. In addition, particles added to the surface layer may fall off during film formation, the surface roughness may increase, or the haze may increase. The average particle size is more preferably 0.1 μm or more and less than 0.9 μm, and still more preferably 0.1 μm or more and less than 0.8 μm. In addition, in order to improve the handling property, two or more kinds of particles having different average particle sizes may be used in combination.

  The biaxially oriented polypropylene film of the present invention preferably has a laminated constitution of at least two layers, and preferably contains slippery particles in the surface layer of at least one side. At this time, the thickness of the layer containing slippery particles is preferably 0.05 to 2.0 μm. If it is less than 0.05 μm, slippery particles may fall off during film formation. If it exceeds 2.0 μm, the haze may increase and the transparency may decrease. The thickness of the layer containing slippery particles is more preferably 0.1 to 1.0 μm, and still more preferably 0.2 to 0.8 μm.

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

  Next, although the manufacturing method of the biaxially-oriented polypropylene film of this invention is demonstrated, it is not necessarily limited to this.

  First, a polypropylene raw material A is supplied to a single-screw extruder for layer A, and a raw material obtained by dry blending polypropylene raw material A and polypropylene raw material B at 90:10 (mass ratio) is supplied to a single-screw extruder for layer B Melt extrusion at 200-260 ° C. Then, after removing foreign substances and modified polymers with a filter installed in the middle of the polymer tube, the lamination thickness ratio of 1/4 to 1/200 is obtained with the multi-manifold type A layer / B layer composite T-die. The laminate is discharged onto a cast drum to obtain a laminated unstretched sheet having a layer configuration of A layer / B layer. Here, the lamination structure may be a three-layer lamination structure of A layer / B layer / A layer, and the lamination thickness ratio at that time (ratio of individual A layer to B layer) is also 1/4 to 1/200. Is preferred. At this time, the cast drum preferably has a surface temperature of 10 to 40 ° C. from the viewpoint of transparency. Further, it is preferable from the viewpoint of transparency that the layer A be in contact with the drum. Further, a three-layer lamination structure of A layer / B layer / A layer may be employed. The method of adhesion to the casting drum may be any of electrostatic application, adhesion using water surface tension, air knife method, press roll method, underwater casting method, etc. An air knife method that is good and capable of controlling the surface roughness is preferred. The air temperature of the air knife is 0 to 50 ° C., preferably 0 to 30 ° C., the blowing air speed is preferably 130 to 150 m / s, and the double tube structure is used to improve the uniformity in the width direction. Is preferred. In addition, it is preferable to appropriately adjust the position of the air knife so that air flows to the downstream side of the film formation so as not to cause vibration of the film.

  In addition, after the film is brought into close contact with the casting drum, the non-casting drum surface of the film is further forcedly cooled to suppress the formation of β crystals on the non-casting drum surface, thereby reducing the haze of the film and smoothness. Can be improved. In particular, when the film thickness is large, even if the temperature of the casting drum is set low to reduce the β crystals of the casting drum surface of the film, the temperature of the non-casting drum surface does not drop sharply, It may form and may lead to deterioration of haze and planarity. Since the temperature at which β crystals tend to form is 80 to 120 ° C., it is preferable to forcibly cool the non-casting drum surface of the film to 80 ° C. or less after closely adhering to the casting drum. The time for lowering to 80 ° C. or less is preferably within 5 seconds after casting, and more preferably within 4 seconds. The method of cooling the non-casting drum surface may be any of air knife method, press roll method, underwater cast method, etc., but it is simple as equipment, easy to control the surface roughness and smooth. Preferred is the air knife method which is good.

  The obtained unstretched sheet is allowed to cool in air and then introduced into the longitudinal stretching step. In the longitudinal stretching step, the unstretched sheet is first brought into contact with a plurality of metal rolls maintained at 120 ° C. or more and less than 150 ° C. to be preheated and heated to the stretching temperature. It is preferable from a viewpoint of transparency improvement to make the metal roll kept at -170 degreeC contact. Specifically, for example, when there are six preheating rolls, the temperature is gradually raised by setting the first roll at 100 ° C. and the second roll at 140 ° C., and setting the third and fourth rolls at 155 ° C. without drawing The two sides of the sheet may be brought into contact with the roll sequentially, and the fifth and sixth strands may be set to 140 ° C. to preheat to the stretching temperature. The reason why the transparency is improved by the method described above is considered as follows. After being allowed to cool in the air on the surface of the unstretched sheet after casting, small β crystals are present, but in the subsequent longitudinal stretching and transverse stretching steps, the β crystals are cleaved to form fibrils, resulting in haze This may cause the film to be less transparent. By bringing the surface of the unstretched film into contact with a metal roll of 150 to 170 ° C. in the preheating step of longitudinal stretching, β crystals on the surface of the unstretched film can be converted to α crystals, and the resulting biaxial It is believed that the transparency of the oriented polypropylene film is improved. Once in contact with a 150-170 ° C. metal roll, it is preheated to the draw temperature by the roll kept at 120 ° C. or more and less than 150 ° C., stretched 3 to 8 times in the longitudinal direction, and cooled to room temperature . When the stretching temperature is 150 ° C. or more, the orientation of the film may be weak and the strength may be reduced. If the draw ratio is less than 3 times, the orientation of the film may be weak and the strength may be reduced.

  Then, the longitudinally uniaxially stretched film is introduced into a tenter, the end of the film is held by a clip, and the transverse stretching is stretched 7 to 13 times in the width direction at a temperature of 140 to 165 ° C. When the stretching temperature is low, the film may be broken or the transparency may be reduced. When the stretching temperature is too high, the orientation of the film may be weak and the strength may be reduced. Also, 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 reduced.

  In the present invention, heat setting is performed at a temperature of 100 ° C. or more and less than 140 ° C. while giving relaxation with a relaxation rate of 2 to 20% in the width direction while keeping the width direction tightly tension-held in the subsequent heat treatment and relaxation treatment step After the step), heat treatment is performed in a multistage manner so that heat setting is performed under the conditions of exceeding the heat setting temperature and below the transverse stretching temperature while holding the width direction in tension in the clip (second step), It is preferable from the viewpoint of coexistence of high strength and low heat recovery.

  The relaxation rate is more preferably 5 to 18%, further preferably 8 to 15% from the viewpoint of obtaining thermal dimensional stability. If it exceeds 20%, the film may become too loose inside the tenter and wrinkles may occur in the product, and if the relaxation rate is less than 2%, thermal dimensional stability may not be obtained.

  The heat treatment / relaxation temperature of the first stage is more preferably 100 ° C. or more and less than 130 ° C., and still more preferably 110 ° C. or more and less than 130 ° C. At a heat treatment temperature of less than 100 ° C., the film may not be sufficiently relaxed, heat shrinkage may be increased, or the film may be flapped and wrinkles may occur. On the other hand, in the case of heat treatment at 130 ° C. or higher, the relaxation of the molecular chain orientation may progress and the strength of the film may be reduced.

  The second heat treatment temperature is higher than the first heat treatment temperature and is not higher than the first heat treatment temperature + 30 ° C., thereby relieving the non-motility non-crystalline molecular chain with insufficient mobility in the first heat treatment step It is possible to achieve both high strength and low heat recovery. From this point of view, the second-stage heat treatment temperature is more preferably the first-stage heat treatment temperature + 5 ° C. or more and the first-stage heat treatment temperature + 25 ° C. or less, and the first-stage heat treatment temperature + 8 ° C. or more first-stage heat treatment temperature +15 C. or less is more preferable.

  After multistage heat treatment, the film is cooled at 80 to 100 ° C while being held in tension in the width direction by a clip, led to the outside of the tenter, the film is released from the clip, and the film edge is slit in the winder process. And roll up the film product roll.

  The biaxially oriented polypropylene film of the present invention obtained as described above can be used in various applications such as packaging films, mold release films, process films, sanitary products, agricultural products, construction products, medical products and the like. However, since they are particularly high in strength, low in heat gain and excellent in transparency, they are preferable as films for flat panel displays such as retardation films and polarizer protective films and films for manufacturing processes such as displays and elements for film capacitors. It can be used.

  When using the biaxially-oriented polypropylene film of this invention as a film for flat panel displays, the biaxially-oriented polypropylene film of this invention can be bonded together to at least single side | surface of a polarizer, and it can use as a polarizing plate. Moreover, when using as a retardation film, it can be used by installing the biaxially-oriented polypropylene film of this invention at a predetermined angle between a liquid crystal cell and a polarizing plate, or the outer side of a polarizing plate. For example, the liquid crystal display can be used by arranging the above-described retardation film and polarizing plate on both sides of a liquid crystal panel and applying a light source from the back side.

  In the case of using the biaxially oriented polypropylene film of the present invention as a film for a capacitor, first, a metal film is provided on the surface. The method of providing a metal film and forming a metal film laminated film is not particularly limited. For example, a method of depositing aluminum on at least one surface of a polypropylene film to provide a metal film such as an aluminum deposited film to be an internal electrode of a film capacitor It is preferably used. At this time, other metal components such as, for example, nickel, copper, gold, silver, chromium and zinc can be deposited simultaneously or sequentially with aluminum. In addition, a protective layer can be provided on the vapor deposition film with oil or the like.

  In the present invention, if necessary, after forming the metal film, the metal film laminated film can be subjected to annealing treatment or heat treatment at a specific temperature. In addition, 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. The preferable manufacturing method of the wound film capacitor is as follows.

  Aluminum is deposited on one side of a polypropylene film under reduced pressure. At that time, the film is deposited in the form of stripes having a margin portion running in the longitudinal direction of the film. Next, a blade is inserted in the center of each deposition portion on the surface and in the center of each margin portion to make a slit, and a tape-like winding reel having a margin on the surface is produced. Two tape-like take-up reels with margins on the left or right, one each for the left margin and the right margin, two overlapping layers of the vapor deposition portion in the width direction, and winding them Get

  When vapor deposition is performed on both sides, it is vapor-deposited in the form of a stripe having a margin that runs in the longitudinal direction of one side, and the other side is striped so that the margin in the longitudinal direction is located at the center of the backside vapor deposition. Deposit in the form of Next, a blade is inserted at the center of each of the front and back margin portions and slitted, and a tape-like take-up reel having a margin on one side on each side (for example, a margin on the back side if there is a margin on the front side) is manufactured. Two pieces of the obtained reel and one non-deposited laminated film are superposed and wound so that the metallized film protrudes from the laminated film in the width direction, to obtain a wound body.

  The core material is removed from the wound body prepared as described above and pressed, and metallikon is sprayed on both end faces to form an external electrode, and a lead wire is welded to the metallikon to obtain a wound film capacitor. The film capacitors are used in a wide variety of applications such as railway cars, automobiles (hybrid cars, electric vehicles), solar power / wind power generation and general household appliances. The film capacitors of the present invention are also suitable for these applications. It can be used.

  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 gauge (manufactured by Anritsu Co., Ltd.), and the average value was determined.

(2) Longitudinal and transverse tensile modulus (E _MD , E _TD )
The biaxially oriented polypropylene film was cut out into a rectangle of 150 mm in length in the test direction and 10 mm in width as a sample. Using a tensile tester (Tensilon AMF / RTA-100 manufactured by ORIENTEC Co., Ltd.), perform measurement five times at 25 ° C and 65% RH according to the method defined in JIS K 7127: 1999, and determine the average value The However, the distance between initial chucks was 50 mm, the tensile speed was 300 mm / min, and the point at which the load passed 1 N from the start of the test was taken as the origin of elongation.

(3) Total Haze of Film The biaxially oriented polypropylene film of the present invention was measured for haze value at 23 ° C. according to JIS K 7136: 2000 using a haze meter (NDH, manufactured by Nippon Denshoku Kogyo Co., Ltd.). %) Was measured 3 times, and the average value was used.

(4) Surface roughness of film (SRa, SRz)
The biaxially oriented polypropylene film is measured under the following measurement conditions according to JIS B 0601: 2001 using a surface roughness meter (SURFCORDER ET 4000A: Kosaka Research Institute Co., Ltd.), and the center average surface roughness SRa ( nm) and ten-point average roughness SRz (nm) were determined. However, the measurement was performed at three points on the surface in contact with the cast drum during extrusion, and the average value was taken.

<Measurement conditions>
Measurement speed: 0.1 mm / S
Measurement range: 1000 μm in the longitudinal direction, 400 μm in the width direction
Measurement pitch: 1 μm in the longitudinal direction, 5 μm in the width direction
Cut-off value λc: 0.2 mm
Tip radius of the stylus: 0.5 μm
(5) In-plane retardation of film and retardation in thickness direction (Ret, Rth)
The in-plane retardation and the thickness direction retardation with respect to the light ray of wavelength 548.3 nm were measured using an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Scientific Co., Ltd.

(6) Thermal shrinkage after treatment at 85 ° C. for 100 hours in the longitudinal direction and width direction For each of the film in the longitudinal direction and width direction, 5 samples with a width of 10 mm and a length of 200 mm (measurement direction) are cut out. Mark the position of the mark as a marked line, measure the distance between the marked lines with a universal projector, and use it as the test length (l ₀ ). Next, the test piece is taken out of paper and taken out after heating for 100 hours in an oven kept at 85 ° C with no load, and after cooling at room temperature, the dimensions (l ₁ ) are measured with a universal projector. It calculated | required by the type | formula and made the average value of five a heat contraction rate.

Thermal contraction rate = {(l ₀ −l ₁ ) / l ₀ } × 100 (%)
(7) Coefficient of static friction μs
Initial rise resistance when using friction tester made by Toyo Tester Industrial Co., Ltd. and rubbing one another in the MD direction so that one surface of the film and its back surface contact each other according to ASTM-D1894 (1999) The value was measured, and the maximum value was taken as the static friction coefficient μs. However, when the initial rise was large and exceeded the upper limit of the measurement value (5.0), measurement was not possible. The sample was made into the rectangle of width 80 mm and length 200 mm, and 5 sets (10 sheets) were cut out. The measurement was performed 5 times and the average value was calculated.

(8) Melting point Tm of film
As a sample, 5 mg of biaxially oriented polypropylene film was collected in an aluminum pan and measured using a differential scanning calorimeter (RDC 220 manufactured by Seiko Instruments Inc.). First, the temperature is raised from room temperature to 260 ° C. at 10 ° C./min (first run) under a nitrogen atmosphere, and after being held for 10 minutes, it is cooled to 20 ° C. at 10 ° C./min. After holding 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
Crystalline PP (a) as a polypropylene material for surface layer (A) (TF850H manufactured by Prime Polymer Co., Ltd., intrinsic viscosity [η]: 1.8 dl / g, MFR: 2.9 g / 10 min, isotactic The index: 96%) is supplied to a single-axis melt extruder for A layer, and 90 parts by mass of the above crystalline PP (a) and a low stereoregular PP (b (b) as a polypropylene raw material for the core layer (B) ) (Made by Idemitsu Kosan Co., Ltd., Elmodu S901, MFR: 50 g / 10 min, molecular weight distribution Mw / Mn: 2, melting point: 80 ° C.) 10 parts by mass dry-blended and subjected to uniaxial melt extrusion for B layer Supply to the machine, melt extrusion at 240 ° C, remove foreign substances with a 60 μm cut sintered filter, and laminate with a feed block type A / B / A composite T die at a thickness ratio of 1/8/1. , Cass controlled surface temperature to 30 ° C The cast sheet was obtained by discharging to a todrum. Next, 7 ceramic rolls are used to preheat to 140 ° C (however, the roll temperature is 100 ° C for the first roll, 125 ° C for the second roll, and 140 ° C for the third roll at 4 ° C) 4 .6 times stretching was performed. Next, the end was held by a clip in a tenter-type drawing machine and introduced, and after preheating at 170 ° C. for 3 seconds, it was drawn to 8.0 times at 165 ° C. In the subsequent heat treatment step, heat treatment is performed at 120 ° C. while giving 10% relaxation in the width direction as the first heat treatment and relaxation treatment, and as the second heat treatment, the clip is held in the width direction with clips for 3 seconds at 140 ° C. Heat treatment was performed. Thereafter, it was guided to the outside of the tenter through a cooling process at 100 ° C. to release the clip at the end of the film, and the film was wound around a core to obtain a 12 μm thick biaxially oriented polypropylene film. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Example 2)
In the longitudinal stretching step of Example 1, a biaxial oriented polypropylene film was obtained in the same manner as in Example 1 except that the temperature of the fourth and fifth strands of the seven ceramic rolls was 155 ° C., except for the above. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Example 3)
In the heat treatment step of Example 1, a biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that the relaxation rate was set to 15%. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Example 4)
Crystalline PP (a) as a polypropylene material for surface layer (A) (TF850H manufactured by Prime Polymer Co., Ltd., intrinsic viscosity [η]: 1.8 dl / g, MFR: 2.9 g / 10 min, isotactic The index: 96%) is supplied to a single-axis melt extruder for A layer, and 85 parts by mass of the above crystalline PP (a) and a low stereoregular PP (b (b) as a polypropylene raw material for the core layer (B) ) (Made by Idemitsu Kosan Co., Ltd., Elmodu S901, MFR: 50 g / 10 min, molecular weight distribution Mw / Mn: 2, melting point: 80 ° C.) 15 parts by mass dry-blended and subjected to uniaxial melt extrusion for B layer Supply to the machine, melt extrusion at 240 ° C, remove foreign substances with a 60 μm cut sintered filter, and laminate with a feedblock type A / B / A composite T die at a thickness ratio of 1/10. , With a surface temperature controlled to 30 ° C The cast sheet was obtained by discharging onto a strike drum. Next, 7 ceramic rolls are used to preheat to 140 ° C (however, the roll temperature is 100 ° C for the first roll, 125 ° C for the second roll, and 140 ° C for the third roll at 4 ° C) 4 .6 times stretching was performed. Next, the end was held by a clip in a tenter-type drawing machine and introduced, and after preheating at 170 ° C. for 3 seconds, it was drawn to 8.0 times at 165 ° C. In the subsequent heat treatment step, heat treatment is performed at 120 ° C. while giving 10% relaxation in the width direction as the first heat treatment and relaxation treatment, and as the second heat treatment, the clip is held in the width direction with clips for 3 seconds at 140 ° C. Heat treatment was performed. Thereafter, it was guided to the outside of the tenter through a cooling process at 100 ° C. to release the clip at the end of the film, and the film was wound around a core to obtain a 12 μm thick biaxially oriented polypropylene film. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Example 5)
First, 99.3 parts by mass of crystalline PP (a) (manufactured by Prime Polymer Co., Ltd., TF850H, MFR: 2.9 g / 10 min), silica particles (SFP, manufactured by Denki Kagaku Kogyo Co., Ltd.) subjected to surface silane coupling treatment -20 MHE, average particle diameter 0.3 μm) 0.5 parts by mass, and further, each of 0.1 parts by mass of antioxidants IRGANOX 1010 and IRGAFOS 168 manufactured by Ciba Specialty Chemicals are mixed at this ratio. Raw materials are supplied from a hopper to a twin-screw extruder, melt-kneaded at 260 ° C., discharged from a die in strands, cooled and solidified in a water bath at 25 ° C., cut into chips, and polypropylene raw material for layer A I got (1).

  The above-mentioned polypropylene raw material (1) is supplied to a uniaxial melt extruder for A layer as a polypropylene raw material for surface layer (A), and 90 mass of the above crystalline PP (a) as a polypropylene raw material for core layer (B) Parts and 10 parts by mass of low stereoregular PP (b) (manufactured by Idemitsu Kosan Co., Ltd., Elmodu S 901, MFR: 50 g / 10 min, molecular weight distribution Mw / Mn: 2, melting point: 80 ° C.) The solution is supplied to a single-layer melt extruder for B layer, melt extrusion is performed at 240 ° C., foreign matter is removed by a 60 μm cut sintered filter, and then 1 by a feed block type A / B / A composite T die. A cast sheet was obtained by laminating at a thickness ratio of / 15/1, and discharging onto a cast drum whose surface temperature was controlled at 30 ° C. Next, 7 ceramic rolls are used to preheat to 140 ° C (however, the roll temperature is 100 ° C for the first roll, 125 ° C for the second roll, and 140 ° C for the third roll at 4 ° C) 4 .6 times stretching was performed. Next, the end was held by a clip in a tenter-type drawing machine and introduced, and after preheating at 170 ° C. for 3 seconds, it was drawn to 8.0 times at 165 ° C. In the subsequent heat treatment step, heat treatment is performed at 120 ° C. while giving 10% relaxation in the width direction as the first heat treatment and relaxation treatment, and as the second heat treatment, the clip is held in the width direction with clips for 3 seconds at 140 ° C. Heat treatment was performed. Thereafter, it was guided to the outside of the tenter through a cooling process at 100 ° C. to release the clip at the end of the film, and the film was wound around a core to obtain a 12 μm thick biaxially oriented polypropylene film. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Example 6)
The above-mentioned polypropylene raw material (1) is supplied to a uniaxial melt extruder for A layer as a polypropylene raw material for surface layer (A), and the above crystalline PP (a) is B as a polypropylene raw material for core layer (B). The solution is supplied to a single-layer melt extruder for layer formation, melt extrusion is carried out at 240 ° C, foreign substances are removed with a 60 μm cut sintered filter, and then 1/30 with a feed block type A / B / A composite T die. / 1 thickness ratio and discharged to a cast drum with controlled surface temperature at 30 ° C to form cast sheet, and after casting, temperature 30 ° C, pressure 0.3MPa on uncooled drum surface of cast sheet The compressed air was blown and cooled to obtain a cast sheet. The temperature of the non-casting drum surface 4 seconds after casting was 75 ° C. Next, 7 ceramic rolls are used to preheat to 140 ° C (however, the roll temperature is 100 ° C for the first roll, 125 ° C for the second roll, and 140 ° C for the third roll at 4 ° C) 4 .6 times stretching was performed. Next, the end was held by a clip in a tenter-type drawing machine and introduced, and after preheating at 170 ° C. for 3 seconds, it was drawn to 8.0 times at 165 ° C. In the subsequent heat treatment step, heat treatment is performed at 120 ° C. while giving 10% relaxation in the width direction as the first heat treatment and relaxation treatment, and as the second heat treatment, the clip is held in the width direction with clips for 3 seconds at 140 ° C. Heat treatment was performed. Thereafter, the film was cooled at 100 ° C. and led to the outside of the tenter to release the clip at the end of the film, and the film was wound around a core to obtain a 25 μm thick biaxially oriented polypropylene film. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Comparative example 1)
In Example 1, crystalline PP (a) is used as a polypropylene material for the core layer (B) (the surface layer and the core layer use the same material), and in the same manner as in Example 1 biaxially oriented otherwise A polypropylene film was obtained. The crystallinity of the raw material was high, and the transparency deteriorated. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Comparative example 2)
In Example 1, 50 parts by mass of crystalline PP (a) as a polypropylene material for the core layer (B), syndiotactic PP (c) (syndiotactic pentad fraction: 0.92, MFR: 3.3. 5 g / 10 min.) 50 parts by mass was dry-blended and supplied to a single-axis melt extruder for B layer, and a biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except the above. Although the crystallinity and heat resistance of the raw materials were low and the transparency was improved, the strength and heat recovery were deteriorated. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Comparative example 3)
In the heat treatment step of Example 4, a heat treatment is carried out at 145 ° C. while giving 10% relaxation in the width direction as the first step heat treatment and relaxation treatment, except for the biaxially oriented polypropylene film in the same manner as in Example 4. I got Since the temperature at the time of relaxation was high, orientation relaxation advanced and the strength of the film deteriorated. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Comparative example 4)
In the transverse stretching step of Example 4, a biaxially oriented polypropylene film was obtained in the same manner as in Example 4 except that the transverse stretching ratio was 5.5. The thickness of the obtained film was 17 μm. Since the draw ratio was low, the orientation was weak and the strength of the film was deteriorated. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Comparative example 5)
In Example 6, a biaxially oriented polypropylene film was obtained in the same manner as in Example 6 except that cooling with air was not performed after casting. The thickness of the obtained film was 25 μm. Since the cooling was not performed, the haze and the planarity of the film deteriorated. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Comparative example 6)
In Example 6, the same polypropylene raw material (1) as the polypropylene raw material for the surface layer (A) was used as the polypropylene raw material for the core layer (B), and in the same manner as in Example 6, biaxial was used. An oriented polypropylene film was obtained. The thickness of the obtained film was 25 μm. Since the particles contained in all layers, the haze of the film was deteriorated. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

(Comparative example 7)
In Example 5, 1.25 parts by mass of silica particle Shilton AMT-20S (particle diameter 1.7 μm, no surface treatment) manufactured by Mizusawa Chemical Co., Ltd. is used instead of silica particle SFP-20 MHE manufactured by Denki Kagaku Kogyo Co., Ltd. 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 μm. At the time of stretching, a void was generated at the interface between the particles and the polypropylene, and the haze of the film was deteriorated. Physical properties and evaluation results of the biaxially oriented polypropylene film are shown in Table 1.

Claims (10)

The surface of at least one surface contains particles having an average particle diameter of 0.1 μm or more and less than 1.0 μm, and the sum EMD + TD of the tensile elastic modulus EMD in the longitudinal direction of the film and the tensile elastic modulus ETD in the width direction is 4.5 GPa or more The total shrinkage is 1% or less, and the thermal shrinkage after treatment at 85 ° C. for 100 hours is 1.0% or less in both the longitudinal direction and the width direction of the film, and the ten-point average roughness on at least one side The biaxially-oriented polypropylene film whose SRz is 500 nm or less. The biaxially oriented polypropylene film according to claim 1, wherein the center average surface roughness SRa on at least one side is 50 nm or less. The biaxially-oriented polypropylene film of Claim 1 or 2 whose in-plane phase difference Ret of a film is 0.1-500 nm. The biaxially oriented polypropylene film according to any one of claims 1 to 3, wherein the value of the ratio Rth / Ret of the ratio of the retardation Rth in the thickness direction of the film to the in-plane retardation Ret of the film is 1 or less. The biaxially oriented polypropylene film according to any one of claims 1 to 4, wherein a static friction coefficient μs between 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 5, wherein the melting point Tm of the biaxially oriented polypropylene film is 158 ° C or more. The biaxially-oriented polypropylene film in any one of Claims 1-6 used as a film for flat panel displays. A flat panel display using biaxially oriented polypropylene film according to claims 1-7. The biaxially-oriented polypropylene film in any one of Claims 1-6 used as an element for film capacitors. A film capacitor using the biaxially oriented polypropylene film according to claim 9 .