KR100277051B1 - 2-Axis Orientated Laminated Polyester Film - Google Patents

Abstract

(a1) a first polyester surface layer having a center line average roughness R _aA of 1 to 7.9 nm, (b1) a 10-point average roughness R _ZA of 15 to 400 nm, (c1) an R _ZA / R _aA of 11 to 51, ) greater 5 ~ 40nm center line of the average roughness than _{R aA R aB, (b2)} 10 -point average roughness of _{75 ~ 600nm R ZB, (c2} ) and a second polyester surface layer has an R _ZB / R _aB of less than 20 , Between the first polyester surface layer and the second polyester surface layer, the following relationship:

Of the biaxially oriented laminated polyester film.

The biaxially oriented laminated polyester film is excellent in lubrication, has excellent electromagnetic characteristics when used for high speed winding, workability and magnetic film, and is particularly useful particularly as a base film for magnetic recording media.

Description

2-Axis Orientated Laminated Polyester Film

FIG. 1 is a view showing an apparatus for measuring dynamic friction coefficient (.mu.k) of the biaxially oriented laminated polyester film of the present invention.

The present invention relates to a biaxially oriented laminated polyester film. More specifically, the present invention relates to a biaxially oriented laminated polyester film excellent in electromagnetic conversion when used for lubrication, high speed winding property, processability and magnetic film, and is particularly useful as a base film for magnetic recording media.

Biaxially oriented laminated polyester films have excellent properties and are therefore widely used in magnetic tapes, electrical products, photographic, metallization and packaging applications. Above all, due to its high strength and modulus, it is widely used as a substrate film for magnetic recording media such as video tape, audio tape, computer tape and floppy disk.

In the field of the above-mentioned media, the demand for high-density recording and high quality is increasing in recent years, and as a result, there is an increasing need for a polyester film as a base film to have a smooth surface.

However, as the flatness of the film surface increases, for example, a film for a magnetic tape has an increased coefficient of friction and has a problem of poor running or scratching. Another problem is that, with the increase of film surface flatness, the shape of the crimped film is severely deteriorated in the film crimping step, making it difficult to obtain a good-shaped crimped film roll. In addition, there is a need to increase the crimp ratio, and it is necessary to expand the film in order to obtain the high reactivity of the required film, and this requirement makes it more and more difficult to obtain a crimped film roll having a good shape.

Therefore, it is necessary that the polyester film as the base film is excellent in lubrication not only in flatness but also in good crimp shape.

A method of mixing inorganic fine particles of silicon oxide or calcium carbonate with polyester to improve the lubricity of the film or a method of precipitating fine particles containing calcium, lithium or phosphorus in a polymerization system for synthesizing polyester. In the above method, when a film is formed with a polyester, the microprojections of fine particles are formed on the film surface to improve the lubrication of the film.

In the above-described method for improving the lubrication property of the film by using the fine protrusions of fine particles, the lubrication is generally improved as the roughness of the film surface is increased. However, when the above-mentioned surface is used as a substrate film for a magnetic recording medium, the surface of the magnetic layer obtained by applying the magnetic coating composition on the surface-irregularized film may also have irregularities And the electromagnetic characteristics tend to deteriorate.

Japanese Unexamined Patent Publication No. 289029/1988 discloses a process for producing an alkoxysilane which is obtained by condensation reaction of hydrolysis and alkoxysilane and has an average particle diameter of 0.01 to 3.0 탆 and a [d ₁₀ / d ₉₀ ] value defined by the following formula (I) (B) having a [D ₂ / D ₁ ] value of 1.1 to 3.0, which is defined by the following formula (2), in an amount of 0.01 to 5.0% by weight based on the total amount of the spherical fine silica particles (fine particles ) Is disclosed as a single-layer polyester film.

Japanese Patent Publication No. 284534/1989 discloses a spherical silica particle having an average particle diameter of 0.12 to 0.6 占 퐉 and an aspect ratio (long particle diameter / short particle diameter) of 1.0 to 1.2 as a first component, 0.01 to 2.0% Formed from a polyester containing 0.005 to 1.8% by weight of spherical silica particles having a particle size of less than 0.1 탆 and a particle size of 0.02 to 0.5 탆 and smaller than a first component having an aspect ratio (long particle diameter / short particle diameter) of 1.0 to 1.2 Layer polyester film is disclosed.

On the other hand, as a method for obtaining flatness and lubrication in contrast to each other, a biaxially oriented laminated film having different surface roughness between the front surface and the back surface, such as an irregularized film such that one surface is smooth and the other surface is lubricated Is proposed.

However, in the above method, one surface is smooth, and therefore, the improvement in the coiling property must be obtained only by other irregularized surfaces. As a result, the front and back surfaces have the same roughness, and the uneven surface of the laminated film needs to have a higher roughness than the roughness of the single-layer film, and it is essential to make the surface irregular by mixing a large amount of the inert fine particles to be.

In Japanese Patent Application Laid-Open No. 143836/1990, a polyester containing particles having an intrinsic viscosity of 0.56 to 0.8 and an average particle diameter of 0.02 to 1.0 탆 is coated on one surface of a polyester film and a surface of a biaxially oriented laminate Surface roughness parameters obtained by superimposing a thickness of ~ 5 mu m and having at least one surface in which the elongation ratios of longitudinal and transverse directions of the new elongation are 10 or less are 8.0 or less (the maximum point of the roughness curve and the center line average roughness Ra : Ratio of Rt / Ra) of the biaxially oriented laminated polyester film.

Japanese Patent Application Laid-Open No. 211054/1991 discloses a lubricant-containing surface having a plurality of fine projections,

Wherein one exposed surface (surface A) of the film is a lubricating surface having an average roughness (Ra _A ) of 0.01 to 0.03 μm and the other surface of the film (surface B) has an average roughness Ra _B of 0.15 μm or less, Discloses a biaxially oriented polyester film having a smooth surface satisfying Ra _B < Ra _A and a surface having an air leaking ratio of the film / film contact surface of 300 seconds or less.

Japanese Patent Application Laid-Open No. 81806/1992 discloses a composite film reinforced in a uniaxial or biaxial direction by coextrusion, biaxial stretching and re-stretching, in which an exposed surface (surface A) is formed, ⁽²⁾ (mu) of 0.005 to 0.030 and a film provided with a smooth and smooth surface having a roughness Ra ⁽¹⁾ (mu) of 0 to 0.015 and another exposed film (surface B) A film comprising a surface provided with:

Ra ⁽¹⁾ and Ra ⁽²⁾ satisfy the following relational formula [I]

The F ₅ value (kg / mm ² ) (5% elongation tensile strength) of the film in the longitudinal axis direction satisfies the following relational expression [II]

A composite film for a metal-coated 8 mm video tape having a scratch number of 0.1 mm or more on the surface A is 0 to 500 / mm ² .

In recent years, magnetic recording has tended to become more and more densified, so that the smooth surface of the base film needs to have a high flatness. When the uneven surface of the base film is further irregularly formed on the crimped surface, the base film causes the following problems: when the magnetic tape is formed by processing, the base film shows a decrease in abrasion resistance, Due to the shrinkage, the uneven surface of the uneven surface is printed on the magnetic layer formed on the smooth surface to make the magnetic layer surface irregular, and the magnetic tape exhibits deteriorated electromagnetic characteristics.

The present inventors have intensively studied to overcome the above-mentioned problems and have developed a film which is suitable for a high-quality magnetic tape, has a suitable smoothness, excellent in winding-up property, excellent in roll form at the time of winding, and remarkable in wear resistance and workability. As a result, Completed.

An object of the present invention is to provide a biaxially oriented laminated polyester film excellent in lubricity, abrasion resistance and scratch resistance, having high smoothness for obtaining high-density recording and high-quality magnetic tape, excellent in winding- .

Other objects and advantages of the invention are apparent from the following description.

According to the present invention, the above objects and advantages of the present invention are achieved by the following:

(a1) center line average roughness R _aA of 1 to 7.9 nm

(b1) a 10-point average roughness R _ZA of 15 to 400 nm and

(c1) R _ZA / R _aA of 11 to 51.

A first polyester surface layer having

(a2) a center line average roughness R _aB greater than R _aA and 5 to 40 nm,

(b2) a 10-point average roughness R _ZB of 75 to 600 nm and

(c2) R _ZB / R _aB of 20 or less

And a second polyester surface layer between the first polyester surface layer and the second polyester surface layer,

By weight of the biaxially oriented laminated polyester film.

The polyester constituting the film in the present invention is preferably selected from a polyester mainly composed of an alkylene terephthalate and / or an alkylene naphthalate.

In the polyester, a copolymer in which a total of at least 80 mol% of the carboxylic acid component is derived from terephthalic acid and / or 2,6-naphthalene dicarboxylic acid and a total of at least 80 mol% of the glycol component derived from ethylene glycol is preferable Polyethylene terephthalate and polyethylene-2,6-naphthalate. In this case, in addition to terephthalic acid and / or 2,6-naphthalene dicarboxylic acid, up to 20 mol% of the total acid component may contain isophthalic acid, biphenyldicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylethanecarboxylic acid, Aromatic dicarboxylic acids such as diphenyl sulfone dicarboxylic acid and diphenyl ketone dicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexane-1,4-dicarboxylic acid Lt; / RTI > dicarboxylic acid. In addition, not more than 20 mol% of the total glycol component may contain, in addition to ethylene glycol, glycols such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol, alicyclic glycols such as cyclohexanedimethanol, Aromatic diols such as resorcin and 2,2-bis (4-hydroxyphenyl) propane, alicyclic diols such as 1,4-dihydroxymethylbenzene, and aliphatic diols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol Polyalkylene glycols (polyoxyalkylene glycols).

The polyester used in the present invention is a polyester derived from a dicarboxylic acid component such as an aromatic hydroxy acid such as hydroxybenzoic acid and w-hydroxycaproic acid based on the total dicarboxylic acid component and the hydroxycarboxylic acid component (Co) polyester wherein at most 20 mol% of the (co) polyester is copolymerized or bonded.

Further, the polyester used in the present invention is a polyester obtained by reacting a component derived from a polyhydroxy compound having three or more functional groups such as polycarboxylic acid or trimellitic acid or pentaerythritol with a polyester based on the total carboxylic acid component There is a copolymer containing an amount of 2 mol% or less, which is substantially linear.

The polyester is known per se and can be prepared in a manner known per se.

The intrinsic viscosity of the polyester measured in o-chlorophenol at 35 DEG C is preferably about 0.4 to 0.8, more preferably 0.5 to 0.7, particularly preferably 0.55 to 0.65.

The biaxially oriented laminated polyester film of the present invention is formed of two or more layers.

These two layers may be the same or different, but the two layers are preferably the same.

In the biaxially oriented laminated polyester film of the present invention, the surface centerline average roughness (R _aA : nm unit) of one surface layer is required to be 1 to 7.9 nm. When R _aA is too large, the volume layering represents the other hand, is improved, a magnetic tape of poor electromagnetic characteristics. When R _aA is too small, undesirably, the film exhibits poor lubricity and tends to form bump-shaped protrusions, or, if crimped in the form of rolls, a poor roll shape is obtained. From this viewpoint, R _aA is preferably 1 to 5.8 nm, more preferably 2 to 4.8 nm.

The first polyester surface layer has a ten-point average roughness R _ZA of 15 to 400 nm. The R _ZA is preferably 40 to 240 nm, more preferably 40 to 130 nm.

The ratio (R _ZA / R _aA ) of the center line average roughness (R _aA ) to the ten-point average roughness (R _ZA : nm unit) of the first polyester surface layer is required to be 11 to 51.

If this ratio (R _ZA / R _aA ) is too small, the film undesirably exhibits poor air extrusion performance and, when rolled in the form of rolls, forms a nonuniform resultant section, . From this viewpoint, this ratio (R _ZA / R _aA ) is preferably 13 to 30, particularly preferably 14 to 21.

The above-mentioned surface characteristics of the first polyester surface layer can be obtained mainly by mixing the inert fine particles with the polyester forming the first polyester surface layer, and adjusting the average particle diameter and the content of the inert fine particles.

The polyester containing the inert fine particles is generally produced by, for example, an ester exchange reaction in a transesterification method, a polycondensation reaction, optionally, or in a direct polymerization method, that is, when a reaction for forming a polyester is carried out, Can be prepared by adding inert microparticles (preferably in the form of their slurries in a glycol) to the reaction system. Preferably, inert microparticles are added to the reaction system at the beginning of the polycondensation reaction, for example, before the reaction mixture has an intrinsic viscosity of about 0.3.

Examples of inert particulates include (1) silicon dioxide (including hydrates, siliceous sand and silica); (2) alumina; (3) silicates containing at least 30 wt% SiO ₂ (e.g., amorphous or crystalline clay minerals, aluminosilicates (including fired products and hydrates), creosote, zircon and fly ash); (4) oxides of Mg, Zn, Zr or Ti; (5) sulfates of Li, Na or Ca (including monohydrates and dihydrates); (7) benzoates of Li, Na or K; (8) terephthalate of Ca, Ba, Zn or Mn; (9) titanates of Mg, Ca, Ba, Zn, Cd, Pd, Sr, Mn, Fe, Co or Ni; (10) a chromate of Ba or Pb; (11) carbon (e.g., carbon black or graphite); (12) glass (e.g., glass powder or glass beads); (13) a carbonate of Ca or Mg; (14) fluorspar; (15) ZnS; And (16) crosslinked polymeric moieties (e.g., crosslinked polystyrene particles or crosslinked silicone resin particles).

In the present invention, two kinds of inert fine particles of an inert fine particle having a large average particle diameter and an inert fine particle having a small average particle diameter are blended in a polyester to form a first polyester surface layer.

For example, 0.05 to 1.5% by weight of the first small inactive fine particles having an average particle diameter (dx: μm unit) of 0.01 to 0.5 μm and the first small inactive fine particles having an average particle diameter (dx: It is preferable to mix the first inert fine particles having a volume of 1/4 or less of the first inert fine particles. It is preferable that the average particle size (dy) of the first large inert particles is larger than the average particle size of the first small inert particles by 0.1 탆 or more.

When the average particle diameter (dx) of the first small-inactive particles is too small or the content of the first small-inactive particles is too small, blocking tends to occur when the film is wound, and the number of bump- . When the average particle diameter dx is too large or the content of the first small-inactive fine particles is too large, the tape tends to exhibit poor electromagnetic characteristics in an undesirable manner. From this viewpoint, the average particle diameter dx of the first small-deactivation fine particles is preferably 0.05 占 퐉 or more, more preferably 0.09 占 퐉 or more, and particularly preferably 0.15 占 퐉 or more. Further, it is preferably 0.34 占 퐉 or less, more preferably 0.29 占 퐉 or less, particularly preferably 0.24 占 퐉 or less. The content of the first microbially inactive fine particles is preferably 0.09% by weight or more, more preferably 0.19% by weight or more, particularly preferably 0.29% by weight or more. Further preferably 1.2% by weight or less, more preferably 0.9% by weight or less, particularly preferably 0.5% by weight or less.

When the average particle diameter (dy) of the first major inert particles is too small or the content of the first major inert particles is too small, bump-like protrusions are likely to be generated in the rolls when the film is crimped. When the average particle diameter (dy) is too large or the content of the first large inert particles is too large, the film is likely to form a nonuniform resultant surface when it is crimped in a roll form undesirably. In view of this, the average particle size (dy) of the first and second inert fine particles is preferably not less than 0.2 mu m, more preferably not less than 0.3 mu m, particularly preferably not less than 0.4 mu m, particularly preferably not less than 0.51 mu m. The thickness is preferably 2.0 占 퐉 or less, more preferably 1.4 占 퐉 or less, and particularly preferably 0.9 占 퐉 or less. The content of the first major inert fine particles is preferably 0.001% by weight or more, more preferably 0.002% by weight or more, particularly preferably 0.003% by weight or more. It is also preferably not more than 0.2% by weight, more preferably not more than 0.09% by weight, particularly preferably not more than 0.03% by weight.

The first small-inactive microparticles may be selected from the inert microparticles. Preferred are silicic anhydride, hydrous silicic acid (silicon dioxide), aluminum oxide (alumina), aluminum silicate, titanium dioxide and kaolin. More preferred are silicon dioxide, titanium dioxide and alumina. Alumina is particularly preferred, among which θ-alumina is particularly preferred.

The first large inert particles may be selected from the inert particles described above. Heat-resistant crosslinked polymer particles, calcium carbonate, barium sulfate and silicon dioxide. More preferably heat resistant crosslinked polymer particles, more preferably crosslinked silicone resin particles and crosslinked polystyrene particles.

It is preferable to use the first small-inactive particles and the first-inactive fine particles as the inert fine particles which are mixed with the polyester to form the first polyester surface layer, and the third small- The inert fine particles may be mixed. The amount of other inert fine particles based on the total amount of the inert fine particles may be 30 wt% or less, and 10 wt% or less.

In the biaxially oriented laminated polyester film of the present invention, the center line average roughness (R _aB : nm unit) of the other surface layer needs to be larger than the center line average roughness (R _aA : nm unit) of the first polyester surface layer.

R _aB is preferably larger than R _aA and is 5 to 25 nm.

The 10-point average roughness of the second polyester surface layer is required to be 75 to 600 nm. R _ZB is preferably 75 to 350 nm, more preferably 110 to 300 nm.

In the second polyester surface layer, R _ZB / R _aB is required to be 20 or less, preferably 5 to 11, more preferably 7 to 11.

In the present invention, the polyester forming the second polyester surface layer preferably contains at least one inert fine particle. When one or more inert fine particles are mixed, it is preferable to use the second inert medium fine particles having an average particle diameter (de: 탆 unit) of 0.3 to 2 탆. When the average particle diameter is too small, the film exhibits poor running and winding property. If the average particle size is too large, the film undesirably exhibits poor abrasion resistance. In view of the above, the average particle diameter de is preferably 0.4 mu m or more, and more preferably 0.5 mu m or more. Further, it is preferably 1.4 mu m or less, more preferably 0.7 mu m or less. The content (We: weight% unit) of the second inert medium fine particles is preferably 0.1 to 5% by weight, and the product de x We of the average particle diameter and content We is preferably 0.06 to 1.5 to be. The product is preferably at least 0.1, more preferably at least 0.6, particularly preferably at least 0.9, and preferably at most 1.0.

When two or more kinds of inert fine particles are mixed, it is preferable to use two or more kinds of inert fine particles having different average particle diameters. For example, 0.05 to 3% by weight of the second microparticle-inactive fine particles having an average particle diameter (dp: μm unit) of 0.03 to 1 μm and an average particle diameter (dq: It is preferable to use 0.005 to 2% by weight of the second major inert particles. When the average particle diameter dp of the second fine particles is too small or the content of the second small inactive particles is too small, blocking is apt to occur when the film is crimped, and a large number of bump-like protrusions are likely to be generated. When the average particle diameter (dp) is too large or the content of the second small-inactive particles is too large, the film exhibits poor abrasion resistance undesirably. In view of this, the average particle diameter dp of the second small-deactivation fine particles is preferably 0.05 mu m or more, more preferably 0.09 mu m or more, particularly preferably 0.16 mu m or more. Further preferably not more than 2.0 mu m, more preferably not more than 1.4 mu m, particularly preferably not more than 0.9 mu m, particularly preferably not more than 0.7 mu m.

In addition, when the average particle diameter dq of the second large inert particles is too small or the difference between the average particle diameter dp of the second small inert particles and the average particle diameter dq is too small, It is easy to exhibit poor winding property and it is difficult to obtain a high processing rate. From this viewpoint, the average particle diameter dq is preferably larger than the average particle diameter dp by at least 0.15 mu m, more preferably at least 0.25 mu m, particularly preferably at least 0.35 mu m, Lt; / RTI > The average particle diameter dq is preferably 2.5 占 퐉 or less, more preferably 1.9 占 퐉 or less, particularly preferably 1.4 占 퐉 or less, particularly preferably 0.9 占 퐉 or less.

In the biaxially oriented laminated polyester film of the present invention, the relationship between the first polyester surface layer and the second polyester surface layer is required to satisfy the following formula.

(1) The surface of the film on which the magnetic layer is formed may have irregularities or the surface roughness of the other surface (running side) may be printed on the surface of the magnetic layer so that the surface of the magnetic layer is uneven, And exhibits poor electromagnetic characteristics. In this regard, The value is preferably 30 or less, more preferably 20 or less, particularly preferably 13 or less, particularly preferably 10 or less. The lower limit is preferably 5, more preferably 7.

In relation (2) Is too small, bump-like protrusions are liable to be generated when the film is crimped into a roll form. If the value is too large, undesirably the film roll is likely to form a non-uniform surface. In this regard, The value is preferably 200 or more, more preferably 400 or more, particularly preferably 700 or more. Further, it is preferably 2,000 or less, more preferably 1,500 or less, particularly preferably 1,200 or less, particularly preferably 1,000 or less.

The thickness of the biaxially oriented laminated polyester film of the present invention is preferably 3 to 20 占 퐉, more preferably 4 to 16 占 퐉. The thickness of the second polyester surface layer is preferably 0.1 to 3 탆 or less, and more preferably 0.5 to 2.5 탆.

The biaxially oriented laminated polyester film of the present invention can be produced by a method known in the art. For example, the non-oriented laminated film may be produced first and then the non-oriented laminated film may be oriented in two directions. The non-oriented laminated film can be produced using known techniques in the field. For example, it can be produced by a method of laminating a film layer which forms a surface in a state of melting or cooling and solidifying a polyester (stream), and a film layer which forms another surface or a center layer. More specifically, it can be produced by a co-extrusion lamination method.

The laminated film obtained by the above method can be biaxially-oriented by a method known in the art. For example, the polyester is melted and co-extruded at its melting point (Tm: 캜) to (Tm + 70) 캜 to obtain an unstretched laminated film having an intrinsic viscosity of 0.4 to 0.8 dl / g, (Tg + 10) 占 폚 (Tg = glass transition temperature of the polyester) at a stretching ratio of not less than 2.5, preferably not less than 3 at a stretching ratio of not less than 2.5 Or more, preferably 3 or more, in the direction perpendicular to the stretching direction. The obtained biaxially oriented laminated polyester film is further stretched in the longitudinal direction and / or the transverse direction as required. As the area stretching ratio, the total stretching ratio is preferably 9 or more, more preferably 12 to 35, particularly preferably 15 to 25. It is also preferable to heat-harden the biaxially oriented film for 1 to 60 seconds at (Tg + 70 ° C) to (Tm - 70) ° C (Tm = melting point of polyester), preferably at 180 to 250 ° C.

The surface hardness of the biaxially oriented laminated polyester film obtained by the above method is preferably 21 or more, more preferably 23 or more, particularly preferably 28 or more. When the surface hardness is too low, undesirably, the film shows poor scratch resistance.

The biaxially oriented laminated polyester film of the present invention can be suitably used as a base film for a magnetic recording medium.

That is, according to the present invention, there is provided a magnetic recording medium comprising a biaxially oriented laminated polyester film of the present invention and a magnetic recording layer formed on a first polyester surface layer of a biaxially oriented laminated polyester film do.

In the manufacture of magnetic recording media, for example, ferromagnetic iron oxides (e.g. containing gamma-Fe ₂ O ₃ or gamma-Fe ₂ O ₃ cavities) or ferromagnetic metal powders (such as pure Fe and Fe- (Iron alloy such as Fe-Ni-Co) is kneaded together with a binder and coated on a first polyester surface layer (non-magnetic support) to prepare a magnetic coating composition, The magnetic recording layer can be formed on the first polyester surface layer of the oriented laminated polyester film. The biaxially oriented laminated polyester film of the present invention is particularly suitable for a high-quality magnetic recording medium containing a ferromagnetic iron oxide powder.

The present invention is described in detail in the following examples.

The physical values and characteristics of the present invention are defined and measured as follows.

(1) average particle diameter of particles (d)

(Measured by a CP-50 type centrifugal particle size analyzer manufactured by Shimadzu Corporation). Based on the obtained centrifugal precipitation curve, an integration curve of particles and its amount was plotted, and a particle size corresponding to 50 mass% was measured based on the integration curve Quot; Technique of Particle Size Measurement ", Nikkan Kogyo Press, 1975, pp. 242-247).

(2) Centerline average roughness (R _a ) and 10-point average roughness (R _z )

Measure centerline mean roughness (R _a ) and 10 - point mean roughness (R _z ) with JIS - B601. The present invention uses a stylus surface roughness tester (SURFCORDER SE-30C, manufactured by Kosaka Laboratory, Ltd.) under the following conditions.

(a) Radius of stylus tip: 2 탆

(b) Measuring pressure: 30 mg

(c) Cut off: 0.08 mm

(d) Measuring length: 8.0 mm

(e) Summary method of data: The measurement is taken 8 times in one sample, and the maximum value is deleted. The remaining seven values are averaged to measure the centerline average roughness (R _a ) and the 10-point average roughness (R _z ).

(3) Static friction coefficient (㎲)

There is provided a stationary glass sheet on which two superposed films are placed. The film placed on the lower side (film contacting with the glass sheet) was rolled with a certain ratio of rolls (about 10 cm / minute) and the measuring device was fixed to one end of the upper film (opposite to the winding direction of the underlying film) The film tensile strength (F) is measured. In this case, the sled located on the upper film has a bottom surface area of 50 cm ² (80 mm x 62.5 mm) and its surface in contact with the film is formed of 80 ° neoprene rubber. Its weight (P) is 1.2 kg.

The coefficient of static friction is calculated on the basis of the following relational expression.

(4) Dynamic friction coefficient of film (μk)

Measurements are made using the apparatus shown in the figure in the following manner. In Figure 1, numeral 1 represents a pulling reel, numeral 2 represents a tensioning arm, numbers 3, 5, 6, 8, 9 and 11 represent free rollers, numeral 4 represents a tensile detector, Numeral 7 denotes a fixing rod (outer diameter 5 mmΦ) of stainless steel SUS 304, numeral 10 denotes a tensile detector (outlet), numeral 12 denotes a guide roller, and numeral 13 denotes a crimp reel.

A film cut of a width of 1/2 inch was applied to the fixing bar 7 (surface roughness 0.3 탆) at an angle of? = 152/180 π radian (152 °), and at a rate of 200 cm / min under conditions of 20 ° C. and humidity 60% (Rubbed). Tensioner 2 is adjusted to an inlet tension T1 of 35 g. After running the film for 90 m, the exit tension (T ₂ : g) is detected by an external tension detector. The travel running coefficient μk is calculated on the basis of the following relation.

(5) Calender Abrasion resistance

The abrasion resistance of the running surface of the film is measured with a 3-roll mini supercalender. The calender is a 3-roll calender using nylon rolls and steel rolls and the film runs at a film running speed of 150 m / min under a linear load of 200 kg / cm on the film at a processing temperature of 80 占 폚. When the film is run at a total length of 6,000 m, the abrasion resistance of the base film is evaluated based on the dust adhering to the upper roller of the calendar.

[Evaluation by five addition]

Class 1: Nylon rolls have no dust at all.

Level 2: Nylon rolls have very little dust.

Class 3: Nylon rolls have some dust, but dry cloth can remove dust.

Class 4: Nylon rolls are dusty and can not be cleaned with a dry cloth, but can be cleaned using a solvent such as acetone.

Grade 5: Nylon rolls are dusty and can not be cleaned even when solvent is used.

(6) The shape of the roll

The film was crimped at a speed of 300 m / min in the form of a roll having a width of 1,100 mm and a length of 15,000 m, and the appearance of the obtained roll was carefully observed and evaluated on the basis of the following five grades.

A uniform cross section is evaluated based on the deviation of the section length in the width direction of the film as shown in Table 1. [

Based on the number of bump-shaped protrusions having a diameter of 2 mm or more, the bump-shaped protrusions are evaluated as shown in Table 1.

[Table 1]

(7) Electromagnetic characteristics of magnetic tapes

Signals prepared by superposing a 50% white level signal (peak of 100% white signal: peak voltage of 0.714 V) and a 100% chroma level signal were recorded on a commercially available VTR for commercial use, and a noise meter (Shibasoku noise meter: type 952R). The definition of chroma S / N follows the following definition (Shibasoku).

ES (p-p) = 0.714V (p-p), and EN (rms) is the square of the peak voltage of the chroma signal level.

[Examples 1 to 4 and Comparative Examples 1 to 3]

Dimethylterephthalate and ethylene glycol were polymerized in the conventional manner in the presence of manganese acetate as an ester exchange catalyst, tin trioxide as a polymerization catalyst, phosphoric acid as a stabilizer, and lubricant as shown in Table 2 or 3, 2, an intrinsic viscosity of 062 (o-chlorophenol, 35 DEG C) for the polyester surface layer.

The polyethylene terephthalate was dried at 170 캜 for 3 hours and fed to a differential extruder of a co-extruded film-forming apparatus to form first and second polyester surface layers, and the first polyester surface layer A layer): co-extruded so that the thickness ratio of the second polyester surface layer (hereafter referred to as layer B) is 95: 5 to obtain an unstretched film.

The unstretched film was preheated at 78 占 폚 and heated to 2.3 times in the longitudinal direction by heating with an IR heater at a surface temperature of 850 占 폚 located at 15 mm on the film between the high and low speed rolls, At 4.0 캜 in the transverse direction at 100 캜.

Further, the biaxial oriented stretched film was preheated at 110 DEG C and stretched 2.2 times in the longitudinal direction between the low speed and the high speed rolls. The resulting film was thermally cured at 215 DEG C for 4 seconds with hot air to obtain a biaxially oriented laminated polyester film having a thickness of 7.5 mu m.

Separately, 5 parts by weight of an isocyanate compound (Desmodur L, supplied by Bayer AG) was added to the composition, the mixture was subjected to stress-dispersion at high speed for 1 hour A magnetic coating composition is obtained.

Composition for a magnetic coating composition:

100 parts by weight of acicular Fe particles

Vinyl chloride-vinyl acetate copolymer 15 parts by weight

(Eslec, manufactured by Sekisui Chemical Co., Ltd.)

Thermoplastic polyurethane resin 5 parts by weight

Chromium oxide 5 parts by weight

Carobone black 5 parts by weight

Lecithin 2 parts by weight

Fatty acid ester 1 part by weight

Toluene 50 parts by weight

Methyl ethyl ketone 50 parts by weight

50 parts by weight of cyclohexanone

The magnetic coating composition was coated on one surface (layer A) of the biaxially oriented laminated polyester film to form a 3 mu m-thick magnetic layer, the magnetic layer was subjected to orientation treatment in a direct magnetic field of 2,500 gauss, And super-calendered (linear pressure 200 kg / cm, temperature 80 ° C). The film is then crimped in the form of a roll. The film rolls are left in the oven for 3 days at 55 < 0 > C. In addition, a back coating composition shown below was coated to form a 1 μm thick back coating, and after drying, the coated film was cut to obtain a magnetic tape.

Backcoat composition:

Carobone black 100 parts by weight

Thermoplastic polyurethane resin 60 parts by weight

18 parts by weight of an isocyanate compound

(Coronate L, manufactured by Nippon Polyurethane Kogyo K.K.)

Silicone oil 0.5 part by weight

Methyl ethyl ketone 250 parts by weight

Toluene 50 parts by weight

Table 2 shows the characteristics of the film and the magnetic tape obtained as described above.

As apparent from Tables 2 and 3, the film or magnetic tape according to the present invention exhibits a low coefficient of friction or excellent lubricity, has excellent winding properties, and has remarkable electromagnetic characteristics and abrasion resistance. The F - 5 value of each film is 19 kg / mm ² in the longitudinal direction and 12 kg / mm ² in the transverse direction.

[Table 2]

[Table 2a]

[Table 3]

[Table 3a]

According to the present invention, it is possible to provide a biaxially oriented laminated polyester film excellent in lubricity, abrasion resistance and scratch resistance, having excellent smoothness capable of obtaining high-density recording and high-quality magnetic tape, .

Claims (13)

(a1) a first polyester surface layer having a center line average roughness R _aA (b1) of 1 to 7.9 nm and a 10-point average roughness R _ZA (c1) of 15 to 400 nm and a R _ZA / R _aA of 11 to 51; and (a2) big 5 ~ 40nm center line of the average roughness than _aA R _aB (b2) 10-point average roughness of 75 ~ 600nm R _ZB (c2) and a second polyester surface layer has an R _ZB / R _aB of less than or equal to 20, the first poly Between the ester surface layer and the second polyester surface layer, Of the biaxially oriented laminated polyester film. The biaxially oriented laminated polyester film according to claim 1, wherein the first polyester surface layer has an R _aA of 1 to 5.8 nm. The biaxially oriented laminated polyester film according to claim 1, wherein the first polyester surface layer has an R _ZA of 40 to 240 nm. The biaxially oriented laminated polyester film according to claim 1, wherein the first polyester surface layer has an R _ZA / R _aA of 13 to 30 nm. The biaxially oriented laminated polyester film according to claim 1, wherein R _aB of the first polyester surface layer is larger than R _aA and 5 to 25 nm. The biaxially oriented laminated polyester film according to claim 1, wherein R _ZB of the first polyester surface layer is 75 to 350 nm. The biaxially oriented laminated polyester film according to claim 1, wherein R _ZB / R _aB of the first polyester surface layer is 5 to 11 nm. The biaxially oriented laminated polyester film according to claim 1, wherein the biaxially oriented laminated polyester film satisfies the relational expression between the first polyester surface layer and the second polyester surface layer represented by the following formula (1) - 1. The biaxially oriented laminated polyester film according to claim 1, wherein the biaxially oriented laminated polyester film satisfies the relational expression between the first polyester surface layer and the second polyester surface layer represented by the following formula (2) - 1. 2. The polyester resin composition according to claim 1, wherein the first polyester surface layer contains 0.05 to 1.5 wt% of the first microparticles having an average particle diameter of 0.01 to 0.5 mu m, the average particle diameter of the first microparticles is larger than the average particle diameter of the first microparticles, Biaxially oriented laminated polyester film containing the first major inactive fine particles of 0.1 to 2.5 占 퐉 in an amount of not more than 1/4 of the first small inactive particles. The biaxially oriented laminated polyester film according to claim 1, wherein the second polyester surface layer contains 0.1 to 5 wt% of the second inert fine particles having an average particle diameter of 0.3 to 2 탆. The nonaqueous secondary battery according to claim 1, wherein the second polyester surface layer contains 0.05 to 3% by weight of the second microparticle-free microparticles having an average particle size of 0.03 to 1 m and is larger than the average particle size of the second micro- 0.005 to 2% by weight The biaxially oriented laminated polyester film containing the second major inert particles. A magnetic recording medium comprising the biaxially oriented laminated polyester film defined in claim 1 and a magnetic recording layer formed on the first polyester surface layer of the biaxially oriented polyester film.