JP2000043213A - Laminated biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated biaxially oriented polyester film excellent in film taking-up properties and handling properties and imparting excellent electromagnetic conversion characteristics when used as a base film for a high density magnetic recording medium, especially, a digital recording type magnetic recording medium and an ultrahigh density magnetic recording medium. SOLUTION: A polyester A layer is laminated on a polyester B layer and the center surface average roughness of the A layer is 4-15 nm and the ten-point average roughness thereof is 100-20 nm while the center surface average roughness of the B layer is 0.5-3.5 nm and the ten-point average roughness thereof is 10-80 nm and the coefficients of friction (μkA, μkB) to a metal of the surfaces of the A layer and the B layer are 0.4 or less and μkA is equal to or larger than μkB and the film coefficient of friction of the surfaces of the A layer and the B layer is 0.5 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated biaxially oriented polyester film. More specifically, excellent electromagnetic conversion when used as a base film as a high-density magnetic recording medium, especially a digital recording type magnetic recording medium, particularly an ultra-high-density magnetic recording medium, with excellent film winding and handling properties. The present invention relates to a laminated biaxially oriented polyester film imparting properties.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate films have been used for a wide range of applications because of their excellent physical and chemical properties, especially as base films for magnetic recording media.

In recent years, higher density and higher capacity of magnetic recording media have been promoted, and accordingly, flatness and thinner thickness of the base film have been demanded.
Particularly, recently, a multilayer metal type tape having a performance comparable to that of a vapor-deposited tape has been developed, and the demand for flattening a base film has been further increased.

[0004] However, when the surface of the base film is flattened to maintain excellent electromagnetic conversion characteristics, the slip or air squeezability deteriorates, and when rolled up in a roll form, wrinkles or bumps are easily formed. And it becomes very difficult to wind up. Also, in the film processing step, if the sliding property is poor, the friction with the metal roll in contact increases, and the film is wrinkled, so that the magnetic layer cannot be applied well or the calender cannot be applied properly.

[0005] In general, the slipperiness of a polyester film can be improved by, for example, (i) a method of depositing inert particles from a catalyst residue in a raw material polymer during the production process, or (ii) a method of adding inert particles. A method of providing fine irregularities on the film surface is employed. In general, the larger the size of the particles in these films and the greater the content thereof, the greater the improvement in the slipperiness.

On the other hand, as described above, the surface of the base film is required to be as smooth as possible from the viewpoint of improving the electromagnetic conversion characteristics. When the surface roughness of the base film is rough, when the magnetic film is processed into a magnetic recording medium, the surface irregularities of the base film protrude from the surface of the magnetic layer even after the application of the magnetic layer, thereby deteriorating the electromagnetic conversion characteristics. In this case, as the size and the content of the particles in the base film increase, the surface roughness increases, and the electromagnetic conversion characteristics deteriorate.

[0007] As means for achieving both the contradictory characteristics of the improvement of the slipperiness and the improvement of the electromagnetic conversion characteristics, the surface on which the magnetic layer is coated is made smooth by improving the electromagnetic conversion characteristics by forming a laminated film. Means for improving the smoothness by roughening the surface are widely known.

However, even when the surface opposite to the surface on which the magnetic layer is applied (hereinafter referred to as a rough surface) is roughened by using the above-described laminated biaxially oriented polyester film, the base film is thin, but the surface is rough. The amount and type of lubricant added to the surface side,
Depending on the particle size, it affects the surface to which the magnetic layer is applied, causing undulations and the like on a smooth surface, and causing a problem that the smoothness is deteriorated.

In particular, in recent high-density magnetic recording media, further smoothing of the magnetic layer is required, and a metal calender having a large line thickness is used, and protrusions of a smooth surface are pushed up from a rough surface side. The adverse effect on the surface properties due to is increasing.

In order to reduce the protrusion of the smooth surface projections from the rough surface side, a method of reducing the particle size of the lubricant to be contained on the rough surface side or a method of slightly containing a large particle size lubricant is proposed. Have been. However, in the former case, the height of the formed projections is low, so that sufficient air squeezability cannot be obtained. In the latter case, the frequency of the formed projections is small, so that the film has sufficient slipperiness. Can not be obtained. Further, when the film is wound into a roll, there is a problem that vertical wrinkles occur in the former case and bumps occur in the latter case, and a sufficient product yield cannot be obtained.

On the other hand, in order to improve the electromagnetic conversion characteristics, further smoothing of the film surface on the side of the magnetic layer is required, and a smooth layer substantially containing no lubricant has been proposed. There is a new problem that the transportability on the smooth surface side during processing becomes poor, wrinkles are formed in the process, and the product yield is greatly reduced.

[0012]

The inventors of the present invention have made intensive studies to develop a film which simultaneously solves the above-mentioned problems. As a result, the film was formed into a laminated biaxially oriented polyester film, and a coating containing colloid particles on the smooth surface side. Laminated biaxial orientation with excellent electromagnetic conversion characteristics and excellent winding and transport properties as a base film by providing a layer and making the surface properties on the smooth and rough sides a certain value. The inventors have found that a polyester film can be obtained, and have reached the present invention.

[0013]

That is, the present invention relates to a laminated biaxially oriented polyester film comprising a polyester B layer laminated on a polyester B layer.
The center plane average roughness (WRaA) of the polyester A layer is 4 to
15 nm, 10-point average roughness (WRzA) 100 to 20
and the center-point average roughness (WRaB) of the polyester B layer is 0.5 to 3.5 nm, the 10-point average roughness (WRzB) is 10 to 80 nm, and (2) the metal on the surface of the polyester A layer. Coefficient of friction (μkA) with respect to the metal is 0.4 or less, the coefficient of friction (μkB) with respect to the metal on the surface of the polyester B layer is 0.4 or less, and μk
A and μkB have the relationship of the following equation, and

[0014]

[Expression 3] μkA ≧ μkB

(3) The film friction coefficient (μkf) between the polyester A layer surface and the polyester B layer surface is 0.5
A laminated biaxially oriented polyester film characterized by the following: This film is formed by adding a water-dispersible copolymerized polyester resin to the polyester B layer with an average particle diameter of 10%.
It is preferable to provide a coating layer mainly composed of colloid particles having a thickness of about 50 nm.

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. The polyester is substantially linear and has film forming properties, especially by melt molding. As the aromatic dicarboxylic acid, for example, terephthalic acid, 2,6
-Naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracene dicarboxylic acid and the like. Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, and 1,4-cyclohexanedimethanol. And alicyclic diols.

In the present invention, as the polyester, alkylene terephthalate and / or alkylene
Those containing 2,6-naphthalate as a main component are preferred.

Of these polyesters, in particular, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, terephthalic acid and / or 2,6-naphthalenedicarboxylic acid account for at least 80 mol% of all dicarboxylic acid components, 80 of all glycol components
A copolymer in which at least mol% is ethylene glycol is preferred. At that time, 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and also alicyclic dicarboxylic acids such as adipic acid and sebacic acid. Acid; an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid; Further, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol. For example, hydroquinone,
Resorcinol, 2,2-bis (4-hydroxyphenyl)
Aromatic diols such as propane; aliphatic diols having an aromatic ring such as 1,4-dihydroxydimethylbenzene; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like. You can also. Of these, polyethylene-2,6-naphthalate is preferred.

Further, the polyester in the present invention includes:
For example, aromatic oxyacids such as hydroxybenzoic acid, ω-
Also included are those which copolymerize or combine a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid at 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component.

Further, the polyester in the present invention includes:
An amount in the range that is substantially linear, for example, 2 for the total acid component
Also included are those obtained by copolymerizing a tri- or higher functional polycarboxylic acid or polyhydroxy compound such as trimellitic acid or pentaerythritol in an amount of not more than mol%.

The above polyesters are known per se and can be produced by a method known per se.
As the above-mentioned polyester, the intrinsic viscosity measured at 35 ° C. as a solution in O-chlorophenol is 0.4 to
0.9 is preferable, 0.5 to 0.7 is more preferable, and 0.55 to 0.65 is particularly preferable.

The laminated biaxially oriented polyester film of the present invention comprises two layers, polyester layer A and polyester layer B.
It is composed of layers. The two layers of polyester may be the same or different, but are preferably the same.

The laminated biaxially oriented polyester film of the present invention has an overall thickness of 2 to 10 μm. Preferably it is 3-7 μm, more preferably 4-6 μm. If the thickness exceeds 10 μm, the tape thickness increases, for example, the length of the tape in a cassette becomes short, and a sufficient magnetic recording capacity cannot be obtained. On the other hand, if the thickness is less than 2 μm, the film thickness is small, so that the film is frequently broken during film formation, the film winding property is poor, and a good film roll cannot be obtained. In addition, the thickness of the flat layer is reduced, the influence of the surface property from the rough surface side to the smooth surface is increased, and satisfactory surface properties of the smooth surface cannot be obtained.

The laminated biaxially oriented polyester film of the present invention has a Young's modulus in the longitudinal direction of 500 to 1000 kg /.
mm ² , transverse Young's modulus is 500 to 1400 kg / m
In m ² , the sum of the Young's modulus in the vertical direction and the horizontal direction is 1300 to 20
It is preferably 00 kg / mm ² . When the tape is used as a tape for a helical magnetic recording medium, it is more preferable that the Young's modulus in the horizontal direction is larger than the Young's modulus in the vertical direction from the viewpoint of improving the contact between the tape and the magnetic head. If the Young's modulus in the vertical direction is less than 500 kg / mm ² , the magnetic tape has low longitudinal strength, and if a strong force is applied in the vertical direction during recording / reproduction, the magnetic tape is easily broken. If the Young's modulus in the transverse direction is less than 500 kg / mm ² , the transverse strength of the magnetic tape is weakened, the contact between the tape and the magnetic head is weakened, and satisfactory electromagnetic conversion characteristics cannot be obtained. On the other hand, the Young's modulus in the vertical direction is 1000k
If it exceeds g / mm ² , the strength in the lateral direction is reduced, the contact between the tape and the magnetic head is weakened, and it is difficult to obtain satisfactory electromagnetic conversion characteristics. The Young's modulus in the horizontal direction is 140
If it exceeds 0 kg / mm ² , the strength in the vertical direction will decrease, and if a strong force is applied in the vertical direction during recording / reproducing, it will be easily broken.

The sum of the Young's modulus in the vertical and horizontal directions is 13
If it is less than 00 kg / mm ² , the contact between the tape and the magnetic head becomes weak, and satisfactory electromagnetic conversion characteristics cannot be obtained. On the other hand, if it exceeds 2,000 kg / mm ² , the draw ratio becomes high during film formation, the film breaks frequently, and the product yield is remarkably deteriorated.

The surface roughness of the laminated biaxially oriented polyester in the present invention is determined by measuring the average roughness of the center plane (W
RaA) is 4 to 15 nm, preferably 6 to 14 nm, more preferably 8 to 13 nm, and 10-point surface roughness (WRzA) is 100 to 200 nm, preferably 100.
１６０160 nm, more preferably 100-140 nm. If the WRaA is less than 4 nm, when the film is wound into a roll, the slip of the film becomes worse, and the film is not smooth. On the other hand, WRaA is 15n
If it is larger than m, projections will be pushed up to a smooth surface in a calendering step, and projections will be transferred to a magnetic layer surface in a curing step, and the magnetic layer surface will be roughened, and electromagnetic conversion characteristics will be deteriorated. If the WRzA is less than 100 nm, the air squeezability deteriorates, vertical wrinkles are generated, and winding is difficult. On the other hand, if the WRzA is larger than 200 nm, the protrusions on the smooth surface are raised in the calendering step, and the protrusions are transferred to the magnetic layer surface in the curing step, so that the magnetic layer surface is roughened and the electromagnetic conversion characteristics deteriorate.

The laminated biaxially oriented polyester film also has a center plane average roughness (WRa) of the polyester B layer.
B) is 0.5 to 3.5 nm, preferably 0.5 to 3.0 nm.
nm, more preferably 0.5 to 2.5 nm,
The zero point average roughness (WRzB) is 10 to 80 nm, preferably 10 to 60 nm, more preferably 10 to 50 nm. This WRaB is less than 0.5 nm or WRzB
When the film thickness is less than 10 nm, the film surface is apt to be scratched during film formation, and the generated shavings adhere to the film surface, which causes an increase in dropout when taped. On the other hand, when WRaB is larger than 3.5 nm or WRzB is larger than 80 nm, when the magnetic layer is applied, the surface of the magnetic layer becomes rough and the electromagnetic conversion characteristics deteriorate.

The laminated biaxially oriented polyester film of the present invention has a coefficient of friction of 0.4 or less with respect to the surface of the polyester A layer and the polyester B layer, respectively.
Preferably, it is 0.35 or less, more preferably 0.30.
It should be: If the friction coefficient exceeds 0.4, the slipperiness with the metal roll during the tape processing step becomes worse, the film sticks to the metal roll, and wrinkles are generated,
The magnetic layer or the BC layer cannot be applied well, and the calendering cannot be performed properly in the calendering step.

The coefficient of friction (μkA) between the polyester A layer and the metal roll and the coefficient of friction (μkB) between the polyester B layer and the metal roll are given by the following equations.

[0030]

## EQU4 ## μkA ≧ μkB

The relationship is as follows. The coefficient of friction (μkA) of the polyester A layer is calculated by the coefficient of friction (μkB) of the polyester B layer.
In order to lower the thickness, it is necessary to roughen the surface of the polyester A layer or to provide a coating layer containing colloidal particles on the polyester A layer similarly to the polyester B layer. However, in the former case, the surface of the polyester A layer becomes too rough, and the surface roughness on the magnetic surface side becomes rough in the calendering step or the curing step, and the electromagnetic conversion characteristics deteriorate. In the latter case, a coating layer is provided on the polyester A layer and the polyester B layer. If the film is exposed to high temperatures during storage or transportation, it will be blocked and cannot be used.

The film friction coefficient between the polyester A layer and the polyester B layer is 0.5 or less, preferably 0.45 or less, and more preferably 0.35 or less. When the film friction coefficient exceeds 0.5, when the film is wound into a roll, slippage between the films is deteriorated, so that the film is broken and the film cannot be wound well.

In the laminated biaxially oriented polyester film of the present invention, it is preferable to provide a coating layer mainly composed of a water-dispersible copolymerized polyester resin and colloid particles having an average particle diameter of 10 to 50 nm on the polyester B layer.

The water-dispersible copolymerized polyester resin is not particularly limited, but preferably has an acid component of 40 to 99.
Mol% of 2,6-naphthalenedicarboxylic acid, 0.1 to 5
Mol% of an aromatic dicarboxylic acid having a sulfonic acid salt group and 0 to 55 mol% of another aromatic dicarboxylic acid, wherein the glycol component is 40 to 100 mol% of ethylene glycol and 0 to 66 mol% of bisphenol A A water-dispersible copolymerized polyester resin comprising another glycol component containing a lower alkylene oxide adduct is preferred.

The average particle size of the colloid particles is 10 to 50 n.
m, preferably 10 to 40 nm, more preferably 10
It is preferably 30 nm. If the average particle size is less than 10 nm, the particles are too small and the coefficient of friction of the film cannot be reduced. On the other hand, if the average particle size exceeds 50 nm, the particles are too large and the particles are liable to fall off.

The polyester A layer in the present invention preferably contains at least two kinds of lubricants of lubricant I and lubricant II having different average particle diameters. In the case of a single lubricant system, it is difficult to achieve both reciprocal winding properties and electromagnetic conversion characteristics.

As the lubricant, a spherical inert lubricant having a particle diameter ratio (major axis / minor axis) in the range of 1.0 to 1.2 is preferable. As the spherical inert lubricant, heat-resistant polymer particles and inorganic particles are preferable. Examples of the heat resistant polymer particles include crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acryl resin particles, crosslinked polyester particles, polyimide particles, melamine resin particles, and the like. Among them, the use of crosslinked polystyrene resin particles or crosslinked silicone resin particles is preferable because the effects of the present invention become more remarkable. Further, spherical silica particles are preferable as the inorganic particles.

The polyester B layer contains substantially no externally added lubricant, or has an average particle size of 0.05 to 0.2.
Those containing an externally added lubricant in a range of 0.005 to 0.1 wt% are preferable. As this lubricant,
The above-mentioned heat-resistant polymer particles or spherical silica particles are preferable, and spherical silica is particularly preferable.

The polyester A layer according to the present invention and / or
Alternatively, the polyester B layer is preferably made of polyethylene terephthalate or polyethylene-2,6-naphthalate, and more preferably made of polyethylene-2,6-naphthalate.

In particular, when the film has a thickness of 6 μm or more, it may be made of polyethylene terephthalate.
If it is less than 6 μm, polyethylene-2,6-naphthalate, which can increase Young's modulus, is preferable.

The laminated biaxially oriented polyester film of the present invention can be produced according to a conventionally known method or a method accumulated in the art. For example, it can be obtained by first producing an unoriented laminated film and then biaxially orienting the film. This unoriented laminated film can be manufactured by a conventionally accumulated method for manufacturing a laminated film. For example, a method of laminating a polyester A layer and a polyester B layer forming the opposite surface in a molten state of the polyester or a state of being cooled and solidified can be used. More specifically, it can be manufactured by a method such as co-extrusion or extrusion lamination. The film laminated by the above-mentioned method can be made into a biaxially oriented film by further following the conventional method for producing a biaxially oriented film. For example, polyester is melted and co-extruded at a temperature of melting point (Tm: ° C) to (Tm + 70) ° C to obtain an unstretched laminated film, and the unstretched laminated film is uniaxially (longitudinal or transverse) (Tg-10). ) To (Tg + 70) ° C. (Tg: glass transition temperature of polyester) at a ratio of 2.5 times or more, preferably 3 times or more, and then Tg to (Tg + 70) in a direction perpendicular to the drawing direction. It is preferable that the film is stretched at a temperature of ° C at a magnification of 2.5 times or more, preferably 3 times or more. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. Thus, the total stretching ratio is preferably 9 times or more as the area stretching ratio, and 12 to 3 times.
5 times is more preferable, and 15 to 30 times is particularly preferable.
Furthermore, the biaxially oriented film has a (Tg + 70)-
It can be heat-set at a temperature of (Tm−10) ° C., for example, preferably at 180 to 250 ° C. The heat setting time is preferably 1 to 60 seconds.

In the laminated biaxially oriented polyester film of the present invention, iron or a needle-like fine magnetic powder containing iron as a main component is coated on the surface of the polyester B layer with a binder such as polyvinyl chloride or a vinyl chloride / vinyl acetate copolymer. Uniformly dispersed in
The coating is performed so that the thickness of the magnetic layer is 1 μm or less, preferably 0.1 to 1 μm.
A metal-coated magnetic recording medium for high-density recording with excellent electromagnetic conversion characteristics such as C / N and low dropout and error rate can be obtained. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like can be dispersed in the same organic binder as the magnetic layer and coated as a base layer of the metal powder-containing magnetic layer. This metal-coated magnetic recording medium is an 8 mm video for analog signal recording, Hi8,
It is extremely useful as a tape medium for β cam SP, W-VHS, digital video cassette coder (DVC) for recording digital signals, 8 mm data, DDSIV, digital β cam, D2, D3, SX, etc.

The various physical properties and properties in the present invention are measured and defined as follows.

(1) Average particle size (A) Particles added to polyester film CP-50 type centrifugal particle size analyzer (Centrifugal Particle) manufactured by Shimadzu Corporation
It is measured using a Size Analyzer). From the integrated curve of particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, the particle size “equivalent sphere diameter” corresponding to 50 mass percent is read, and this value is defined as the above average particle size. (Book
"Granularity measurement technology", published by Nikkan Kogyo Shimbun, 1975, page 2
42-247).

(B) Colloidal particles added to the coating layer A photograph of each particle was taken with a scanning electron microscope at a magnification corresponding to the size used, and the particles were analyzed using an image analysis processor Luzex 500 (manufactured by Nippon Regulator). Is calculated.

(2) Particle Content The sample was dissolved in a solvent in which the polyester was dissolved but the particles were not dissolved, the particles were centrifuged from the solution, and the particle content was calculated as a ratio (% by weight) to the total amount of the particles. And

(3) Layer Thickness Using a secondary ion mass spectrometer (SIMS), an element originating from the highest concentration of particles in the film ranging from the surface layer to a depth of 3000 nm and a carbon element of polyester The concentration ratio (M ⁺ / C ⁺ ) is defined as the particle concentration, and the analysis in the thickness direction is performed from the surface to a depth of 3000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. Then, the particle concentration that has once reached the maximum value starts to decrease again. Based on the concentration distribution curve, a depth at which the surface particle concentration becomes 1/2 of the maximum value (this depth is deeper than the depth at which the maximum value is obtained) is determined, and this is defined as the surface layer thickness.

The conditions are as follows. Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster region: 400 μm □ Analysis region: Gate 30% Measurement vacuum degree: 6.0 × 10 ⁻³ Torr E-GUN: 0. 5KV-3.0A In the case where the particles most contained in the range from the surface layer to the depth of 3000 nm are organic polymer particles, it is difficult to measure by SIMS. Therefore, XPS (X
(Line photoelectron spectroscopy), IR (infrared spectroscopy) and the like may be used to measure the same depth profile to determine the surface layer thickness.

(4) Overall Film Thickness Ten films are stacked so that dust does not enter, and the thickness is measured with a dot-type electronic micrometer to calculate the film thickness per one film.

(5) Young's modulus A film was cut into a sample having a width of 10 mm and a length of 15 cm, and the distance between the chucks was set to 100 mm. The tensile speed was 10 mm / min and the chart speed was 500 mm / min. Pull. The Young's modulus is calculated from the tangent at the rising portion of the obtained load-elongation curve.

(6) Electromagnetic conversion characteristics A signal having a frequency of 7.4 MHZ is recorded using the following equipment, and the ratio of the 6.4 MHZ and 7.4 MHZ values of the reproduced signal is set as the C / N of the tape, and compared. The C / N of Example 4 is Od
B and expressed as a relative value. ◎: +3 dB or more ○: +1 dB or more and less than +3 dB ×: less than +1 dB Equipment to be used 8 mm video recorder: EDV-60 manufactured by Sony Corporation
00 C / N measurement: Noise meter manufactured by Shibasoku Co., Ltd.

(7) Surface roughness (WRa, WRz) Non-contact type three-dimensional roughness meter (NT-200) manufactured by WYKO
0) using a measurement magnification of 40 times and a measurement area of 246.6 μm
Under the condition of m × 187.5 μm (0.0462 mm ² ), the measurement was performed with the number of measurements (n) of 10 or more, and the center plane average roughness (WR) was measured by the surface analysis software built in the roughness meter.
a) and 10-point average roughness (WRz) are determined.

(A) Center plane average roughness (WRa) This is a value calculated by the following equation and output.

[0054]

(Equation 5)

Z _jk is divided into m in the measurement direction (246.6 μm) and the direction perpendicular thereto (187.5 μm).
This is the height on the two-dimensional roughness chart at the j-th and k-th positions in each direction when divided into n.

(B) 10-point average roughness (WRz) Five points are taken from the higher peak (HP) and five points from the lower valley (Hv), and the average roughness is defined as WRz.

[0057]

WRz = [(Hp1 + Hp2 + Hp3 + Hp4 + Hp5)
− (Hv1 + Hv2 + Hv3 + Hv4 + Hv5)] / 5

(8) Winding property The number of the bumps having a size of 2 mmφ or more (see FIG. 1) and the occurrence of vertical wrinkles (see FIG. 2) when the film is wound into a 6000 m roll with a width of 1000 mm are shown. It is measured, and the number of bumps is proportionally converted per 1 m of product width. The evaluation is performed by obtaining an average value per one winding when winding ten or more windings and evaluating as follows. (A) Butts ：: 0 to 2 pcs / m ○: 3 to 5 pcs / m △: 6 to 10 pcs / m ×: 11 pcs / m or more (B) Vertical wrinkles 未 満: 0 to less than 10% ：: 10 Less than 20% △: Less than 20-30% ×: 30% or more

(9) Transportability The occurrence of process wrinkles due to poor slippage between the film smooth surface and the metal roll in the magnetic layer coating step or the calendaring step when a roll of 1000 mm in width is taped is described as follows. judge. ◎: No wrinkles were generated at all. ○: Wrinkles were slightly generated, but there was no problem in the process. △: Wrinkles were generated, but they could be used in the process. ×: Wrinkles were generated but could not be used.

(10) Coefficient of friction of film μs A fixed glass plate is placed under the two superposed films, and the film under the superposed film (the film in contact with the glass plate) is put on a low-speed roll. (10 cm / min), and a detector is fixed to one end of the upper film (the end opposite to the direction in which the lower film is taken) to detect the tensile force at the start between the films. The thread used at that time weighs 1 kg and the lower area is 100
cm ² is used. The coefficient of friction (μs) was determined by the following equation.

[0061]

Μs = tensile force at start (kg) / load 1 kg

(11) Film friction coefficient μ against metal
k In an environment of a temperature of 20 ° C. and a humidity of 60%, the surface of the polyester A layer or the surface of the polyester B layer is brought into contact with a SUS rod having a diameter of 3 mm at an angle θ = π radian (180 °) for 20 minutes per minute.
Move (friction) at a speed of 0 cm. Inlet tension T
_{When the} tension controller 2 is adjusted so that ₁ becomes 35 g, the film is adjusted to have an outlet tension (T ₂ : g) of 6 gm.
After traveling m, it is detected by the exit tension detector, and the traveling friction coefficient μk is calculated by the following equation. This measurement is performed ten times, and the average value is adopted.

[0063]

[Equation 8] μk = (2.303 / θ) log (T 2 / T 1) = 0.733log (T 2/35)

[0064]

EXAMPLES The present invention will be further described below with reference to examples. In addition, “parts” means parts by weight.

Examples 1 to 3 and Comparative Example 3 <Production of copolymerized polyester resin> 90 parts of dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate 6
Parts, 5-sodium sulfoisophthalic acid (4 parts), ethylene glycol (70 parts), and bisphenol A ethylene oxide adduct (30 parts) represented by the following structural formula were charged into a transesterification reactor.
Five parts were added and the mixture was heated under a nitrogen atmosphere while controlling the temperature at 230 ° C., and the produced methanol was distilled off to carry out a transesterification reaction.

[0066]

Embedded image

(However, m + n = 4 (average value))

Next, Irganox 1 was added to this reaction system.
After adding 0.6 parts of 010 (manufactured by Ciba Geigy), the temperature is gradually increased to 255 ° C., and the polycondensation reaction is carried out by reducing the pressure of the system to 1 mmHg to obtain a copolyester resin having an intrinsic viscosity of 0.64. Obtained. Table 1 shows the composition of the copolymerized polyester resin.

<Preparation of Aqueous Dispersion of Polyester> 20 parts of this copolymerized polyester resin was dissolved in 80 parts of tetrahydrofuran, and 180 parts of water was added dropwise to the resulting solution under high-speed stirring at 10,000 rpm to give a bluish milky white. Was obtained. Subsequently, this dispersion was distilled under a reduced pressure of 20 mmHg to remove tetrahydrofuran. Thus, a polyester aqueous dispersion having a solid content of 10 wt% was obtained.

Polyester aqueous dispersion 1 thus obtained
A water-based coating solution (solid content: 1.8 wt.%) Composed of 20 parts of colloidal particles having an average particle diameter of 25 nm shown in Table 1 and 14 parts of polyoxyethylene nonyl phenyl ether having an HLB of 12.8 as a surfactant, relative to 00 parts. %)created.

<Preparation of Biaxially Oriented Polyester Film>
Dimethyl-2,6-naphthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer,
Further, the additive particles shown in Table 1 were added as a lubricant, and the mixture was polymerized by a conventional method to obtain an intrinsic viscosity (orthochlorophenol, 35
° C) polyethylene-2,6 for layer A and layer B of 0.61
-Naphthalate (PEN) was obtained.

After drying these polyethylene-2,6-naphthalate pellets at 170 ° C. for 6 hours, they were supplied to two extruder hoppers, melted at a melting temperature of 280 to 300 ° C., and then used with a multi-manifold type coextrusion die. Layer A on one side of layer B, and extruded on a rotating cooling drum having a surface finish of about 0.3S and a surface temperature of 60 ° C, and a thickness of 90 µm.
Was obtained.

The thus obtained laminated unstretched film is preheated to 120 ° C., and further cooled between low-speed and high-speed rolls.
The film was stretched 4.0 times by heating with an IR heater having a surface temperature of 900 ° C. from above 5 mm, and after cooling, the coating solution prepared above was applied to the polyester B layer side of the uniaxially stretched film by d.
It was applied to a thickness of 10 nm in the ry state. Subsequently, it was supplied to a stenter and stretched 5.0 times in the horizontal direction at 145 ° C. The obtained biaxially stretched film is heated at 210 ° C. with hot air.
Heat fixing was performed for 2 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 4.5 μm. Young's modulus of these films are longitudinal 600 kg / mm ^2, was transverse 900 kg / mm ^2.

The method for producing the magnetic tape was as follows. The composition shown below was put into a ball mill, kneaded and dispersed for 16 hours, and then 5 parts of an isocyanate compound (Desmodur L, manufactured by Bayer AG) was added. Composition of magnetic paint: needle-shaped Fe particles 100 parts vinyl chloride-vinyl acetate copolymer 15 parts (Sekisui Chemical Co., Ltd. SREC 7A) thermoplastic polyurethane resin 5 parts chromium oxide 5 parts carbon black 5 parts lecithin 2 parts fatty acid ester 1 part toluene 50 parts Methyl ethyl ketone 50 parts Cyclohexanone 50 parts

This magnetic paint was applied to one side (layer B) of a biaxially oriented laminated polyester film so as to have a coating thickness of 0.5 μm, and then subjected to an orientation treatment in a DC magnetic field of 2500 gauss and heated at 100 ° C. After drying, it was subjected to spar calender treatment (linear pressure: 300 kg / cm, temperature: 80 ° C.) and wound up. The wound roll was kept in an oven at 55 ° C. for 3 days, and then cut into a width of 8 mm to obtain a magnetic tape. Table 1 shows the results.

Example 4 The additive particles shown in Table 1 were added to the polyester A layer and the polyester B layer, and the film had a Young's modulus of 550 kg / mm ^{2 in} the vertical direction and 1 in the horizontal direction.
Performed in the same manner as in Example 1 except that the stretching ratio in the machine direction and the transverse direction was changed to 200 kg / mm ² ,
A laminated biaxially oriented polyester film was obtained, and then a magnetic tape was obtained in the same manner as in Example 1. Table 1 shows the results.
Shown in

Comparative Examples 1-2 The magnetic tape was prepared in the same manner as in Example 1 except that the additive particles shown in Table 1 were added to the polyester A layer and the B layer, and after uniaxial stretching, the coating layer was not provided. Obtained. Table 1 shows the results.

Comparative Example 4 A magnetic tape was obtained in the same manner as in Example 1, except that the additive particles shown in Table 1 were used in a single-layer system, and after uniaxial stretching, the coating layer was not provided. Table 1 shows the results.
Shown in

[0079]

[Table 1]

As is evident from Table 1, the device according to the present invention has excellent winding properties and transporting properties while exhibiting excellent electromagnetic conversion properties.

[0081]

According to the present invention, it is possible to provide a laminated biaxially oriented polyester film having excellent electromagnetic conversion characteristics and also excellent characteristics such as winding property and transportability. This polyester film is used as a base film of a magnetic recording medium, particularly, a 1/2 inch video tape, 8
It is useful as a base film for magnetic tapes such as mm video tapes, data cartridge tapes, and digital video tapes.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing the occurrence of bumps when a film is wound into a roll.

FIG. 2 is a schematic explanatory diagram for determining the occurrence state of film vertical wrinkles and its ratio.

[Procedure amendment]

[Submission date] April 23, 1999 (1999.4.2
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

ΜkA ≧ μkB (3) A laminated biaxially oriented polyester film, characterized in that the film friction coefficient (μkf) between the polyester A layer surface and the polyester B layer surface is 0.5 or less.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 10

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

[0013]

That is, the present invention relates to a laminated biaxially oriented polyester film comprising a polyester B layer laminated on a polyester B layer.
The center plane average roughness (WRaA) of the polyester A layer is 4 to
15 nm, 10-point average roughness (WRzA) 100 to 20
0 nm, and the center plane average roughness (WRaB) of the polyester B layer is 0.5 to 3.5 nm, the 10-point average roughness (WRzB) is 10 to 80 nm, and (2) the polyester A layer surface The coefficient of friction (μkA) for metal is 0.4 or less, the coefficient of friction (μkB) for metal on the surface of the polyester B layer is 0.4 or less, and μk
A and μkB have the relationship of the following equation, and

 ────────────────────────────────────────────────── ─── Continued on the front page F-term (reference) 4F100 AA20A AA22H AA29H AA37H AB02 AK15J AK22J AK41A AK41B AK41C AK41J AK42A AK42B AK51 AL01 AL01C BA02 BA03 BA07 BA13 CA05 CA19A CA19B DD07A DD07B DE07A DD07B JA07 JK16A JK16B JL01 JM01C JM01H YY00 YY00A YY00B YY00C YY00H 4J002 BC022 BC032 CC182 CF002 CF061 CF081 CG002 CM042 CP032 DJ016 FA082 FA086 FD172 FD176 GF00 GS01 5D006 CB01 CB05 FA07

Claims (13)

[Claims] 1. A polyester A layer on a polyester B layer
A laminated biaxially oriented polyester film obtained by laminating layers, wherein (1) a polyester A layer has a center plane average roughness (WRaA) of 4 to 15 nm and a 10-point average roughness (WRz).
A) is from 100 to 20 nm and polyester B
The center plane average roughness (WRaB) of the layer is 0.5 to 3.5 n
m, the 10-point average roughness (WRzB) is 10 to 80 nm, (2) the coefficient of friction (μkA) of the polyester A layer surface against metal is 0.4 or less, and the friction coefficient of the polyester B layer surface on metal ( μkB) is 0.4 or less, and μkA and μkB have a relationship of the following equation:
ΜkA ≧ μkB (3) A laminated biaxially oriented polyester film having a film friction coefficient (μkf) between the surface of the polyester A layer and the surface of the polyester B layer of 0.5 or less. 2. The laminated biaxially oriented polyester film according to claim 1, wherein a coating layer mainly composed of a water-dispersible copolymerized polyester resin and colloid particles having an average particle diameter of 10 to 50 nm is provided on the surface of the polyester B layer. 3. The laminated biaxially oriented polyester film according to claim 1, wherein the polyester A layer contains at least two kinds of lubricants containing lubricants I and II having different average particle diameters. 4. The laminated biaxially oriented polyester film according to claim 3, wherein the lubricants I and II contained in the polyester A layer are spherical inert particles. 5. The laminated biaxially oriented polyester film according to claim 4, wherein the lubricant I and the lubricant II contained in the polyester A layer are heat-resistant polymer particles or spherical silica particles. 6. The laminated biaxially oriented polyester film according to claim 4, wherein the lubricant I and the lubricant II contained in the polyester A layer are spherical silica particles. 7. The average particle size (D _I ) of the lubricant I contained in the polyester A layer is 0.2 to 0.6 μm, and the average particle size (D _I ) of the lubricant _I and the average particle size of the lubricant II (D _I ) 5. The laminated biaxially oriented polyester film according to claim 4, wherein the difference of (D _II ) is 0.1 (μm) ≦ (D _I -D _II ) ≦ 0.4 (μm). 8. The laminated biaxially oriented polyester film according to claim 1, wherein the polyester B layer contains substantially no lubricant. 9. The polyester B layer has an average particle diameter of 0.05 to 0.05.
The laminated biaxially oriented polyester film according to any one of claims 1 to 7, further comprising a lubricant in an amount of 0.2 µm and an addition amount of 0.005 to 0.1 wt%. 10. The film has a Young's modulus in the longitudinal direction of 500.
~1000kg / mm ^2, the transverse direction Young's modulus is 500
1400 kg / mm ² , Young's modulus in vertical and horizontal directions is 13
00~2000kg / mm ² is laminated biaxially oriented polyester film of claim 1, wherein. 11. The laminated biaxially oriented polyester film according to claim 10, wherein the Young's modulus in the horizontal direction of the film is larger than the Young's modulus in the vertical direction. 12. The laminated biaxially oriented polyester film according to claim 1, wherein the polyester A layer and the polyester B layer are a polyethylene-2,6-naphthalate film. 13. The laminated biaxially oriented polyester film according to claim 1, which is used for a digital recording type magnetic recording tape.