JP2002240223A - Laminated biaxially-oriented polyester film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated biaxially-oriented polyester film excellent in winding characteristics and in electromagnetic conversion characteristics when the film is used for a magnetic recording medium. SOLUTION: The laminated biaxially-oriented film has a constitution wherein a polyester B-layer is laminated on one side of a polyester A-layer. The average roughness of the central surface found by measuring the surface of a polyester ○-layer with a magnification ▵ is expressed as WRa (▵) ○. Then, WRa (25) A=2-10 nm. WRa (2.5) A=3-10 nm. WRa (25) B=3-15 nm. WRa (2.5)B=5-15 nm.

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, and more particularly, to a laminated biaxially oriented polyester film which is excellent in flatness and windability and has excellent electromagnetic conversion characteristics when used as a magnetic recording medium. About the film.

[0002]

2. Description of the Related Art In recent years, in a digital signal recording type magnetic recording medium, higher density and higher capacity have been promoted, and flatness and thinner thickness of a base film have been demanded. However, when the surface of the base film is flattened in order to maintain excellent electromagnetic conversion characteristics, slipperiness and air squeezability become insufficient, for example, when the film is rolled up, wrinkles are formed, and the surface of the film roll becomes uneven. Therefore, the appropriate range of tension, contact pressure, and speed at the time of lowering the product yield or winding up becomes narrow, and it becomes very difficult to wind up.

[0003] As a means for achieving both the contradictory characteristics of improving the winding property and the electromagnetic conversion characteristics, a laminated film is used to flatten the surface on which the magnetic layer is applied and improve the electromagnetic conversion characteristics. Means for improving and roughening the opposite side to improve winding and productivity are widely known.

[0004]

However, in the conventional method, when the surface roughness of the rough surface is rough, the irregularities are transferred to the surface coated with the magnetic layer, thereby deteriorating the electromagnetic conversion characteristics, or the roughness of the rough surface is too high. And, in the film processing process, etc., the disadvantage that particles easily fall off due to contact with equipment, or, if the magnetic layer coating surface is flattened more than necessary,
The problem that the surface of the film is shaved in the coating process occurs.

[0005] Regarding the winding property, when the surface properties of the front and back surfaces are different as in a laminated film, the air squeezability on the front and back sides of the film is important, and it is not sufficient to simply roughen the surface of the rough surface. In many cases, the film handling property, particularly the film winding property, was poor during the above operation.

An object of the present invention is to provide a laminated biaxially oriented polyester film having excellent winding properties and excellent electromagnetic conversion characteristics when used as a magnetic recording medium and useful as a base film for a magnetic recording medium. And

[0007]

SUMMARY OF THE INVENTION The present invention relates to a laminated biaxially oriented film having a polyester B layer laminated on one side of a polyester A layer, wherein the non-contact three-dimensional surface roughness meter for the polyester A layer surface is provided. W measured at 25 × magnification using
Ra (25) A is 2 to 10 nm, WRa (2.5) A measured at a magnification of 2.5 is 3 to 10 nm, and a magnification of 25 using a non-contact three-dimensional surface roughness meter for the surface of the polyester B layer.
WRa (25) B measured at a magnification of 3 to 15 nm, and WRa (2.5) B measured at a magnification of 2.5 times is 5 to 15 nm.
And a laminated biaxially oriented film.

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. Such polyesters are substantially linear and have film-forming properties, especially by melt-forming.
Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. Can be. Examples of the aliphatic glycol include a polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, and an alicyclic group such as cyclohexanedimethanol. Diols and the like can be mentioned.

As such a polyester, a polyester containing alkylene terephthalate and / or alkylene naphthalate as a main component is preferably used. Among them, not only polyethylene terephthalate and polyethylene-2,6-naphthalate, but also, for example, terephthalic acid and / or 2,6-naphthalenedicarboxylic acid account for 80% by mole or more of all dicarboxylic acid components,
Copolymers in which at least 80 mol% of all glycol components are ethylene glycol are particularly preferred. At that time, not more than 20 mol% of the total acid component is terephthalic acid and / or 2,6-
The above-mentioned aromatic dicarboxylic acids other than naphthalenedicarboxylic acid can be used, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid; cyclohexane-1,
An alicyclic dicarboxylic acid such as 4-dicarboxylic acid can be used.

Also, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol. For example, hydroquinone, resorcin, 2,2
Aromatic diols such as 2-bis (4-hydroxyphenyl) propane; aliphatic diols having an aromatic ring such as 1,4-dihydroxydimethylbenzene; polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol (Polyoxyalkylene glycol) and the like. Further, in the polyester of the present invention, for example, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid or an aliphatic oxyacid such as ω-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. And those which are copolymerized or bonded at 20 mol% or less based on the total amount of

Further, the polyester in the present invention includes:
For amounts in a range that is substantially linear, e.g., for all acid components,
Also included are those obtained by copolymerizing trifunctional or higher functional polycarboxylic acid or polyhydroxy compound, for example, trimellitic acid, pentaerythritol and the like in an amount of 2 mol% or less.

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

The laminated biaxially oriented polyester film of the present invention comprises two layers, a polyester A layer and a polyester B layer. The two layers of polyester may be the same or different from each other, but the same polyester is preferable.

The laminated biaxially oriented polyester film of the present invention has a center plane average roughness WRa measured at a magnification of 25 using a non-contact three-dimensional surface roughness meter on the surface of the polyester A layer.
(25) A is 2 to 10 nm, preferably 2 to 7 nm, more preferably 2 to 5 nm, and the center plane average roughness WRa (2.5) A measured at a magnification of 2.5 is 3 to 10 nm, preferably It has a characteristic of 3 to 8 nm, more preferably 3 to 6 nm.

If the WRa (25) A is less than 1.5 nm or the WRa (2.5) A is less than 3 nm, the surface of the polyester film becomes extremely flat, so that wrinkles occur in the film production process. Property becomes poor,
Productivity deteriorates. On the other hand, if the WRa (25) A or WRa (2.5) A exceeds 10 nm, the surface of the film becomes rough, and when used as a magnetic recording medium, the output is reduced and noise is increased, which is not preferable.

The laminated biaxially oriented polyester film of the present invention further has a center plane average roughness WRa (25) B of the surface of the polyester B layer measured at a magnification of 25 using a non-contact three-dimensional surface roughness meter. 3 to 15 nm, preferably 3 to 1
2 nm, more preferably 5 to 10 nm, and a center plane average roughness WRa (2.5) B measured at a magnification of 2.5 times is 5 to 1
5 nm, preferably 5 to 13 nm, more preferably 7 to
It has a characteristic of 13 nm.

If the WRa (25) B is less than 3 nm or the WRa (2.5) B is less than 5 nm, the air squeezability deteriorates and the winding property of the film deteriorates. On the other hand, WRa (25) B or WRa (2.5) B is 15n.
If it exceeds m, the coarse protrusions on the surface B are transferred to the surface A and the surface A is roughened.

The center plane average roughness WRa of the laminated biaxially oriented polyester film of the present invention measured at a magnification of 2.5 times using a non-contact three-dimensional surface roughness meter on the surface of the polyester A layer.
(2.5) A is preferably larger than the center plane average roughness WRa (25) A measured at a magnification of 25 using a non-contact three-dimensional surface roughness meter on the surface of the polyester A layer.

2.5 mm × 1.9 m of WRa (2.5)
The method of roughening the surface A over a wide area of m is not particularly limited, but when a polyester film is formed, the melt-extruded polyester is cooled and solidified on a rotating cooling drum provided with fine irregularities, so that the rotational cooling is performed. It is preferable that the surface (the surface B) that comes into contact with the drum be provided with an uneven shape and the undulation be formed by the pushing-up action toward the surface A.

In the laminated biaxially oriented polyester film of the present invention, the polyester A layer has an average particle size of 0.01 to
It preferably contains 0.6 μm of inert particles. The average particle size of the particles is preferably 0.05 to 0.4 μm
And more preferably 0.1 to 0.2 μm. When the average particle size exceeds 0.6 μm, the surface becomes rough,
Electromagnetic conversion characteristics are deteriorated. On the other hand, if it is less than 0.01, the air squeezability between the films is deteriorated and the winding property is deteriorated, which is not preferable.

The content of the particles is 0.005 to 0.5.
5% by weight, preferably 0.05 to 0.4% by weight;
More preferably, the content is 0.01 to 0.3% by weight. The inert particles function as a lubricant. The inert particles may be a mixture of a plurality of types. If the content exceeds 0.5% by weight, the abrasion resistance and the electromagnetic conversion characteristics are deteriorated.
If it is less than 1, the running property is remarkably deteriorated, which is not preferable.

In the laminated biaxially oriented polyester film of the present invention, the polyester B layer has an average particle size of 0.2 to 0.2.
It preferably contains 1.0 μm of inert particles α.
The average particle size of the particles α is preferably 0.3 to 0.8 μm.
m, and more preferably 0.4 to 0.6 μm.
When the average particle size exceeds 1.0 μm, the surface becomes rough and the abrasion resistance is deteriorated. On the other hand, when the average particle size is less than 0.2, the running property and the air squeezability between the films are unfavorably deteriorated.

The content of the particles α is 0.005 to
The content is 0.5% by weight, preferably 0.05 to 0.4% by weight, and more preferably 0.01 to 0.3% by weight. If the content exceeds 0.5% by weight, the abrasion resistance deteriorates, while if it is less than 0.005% by weight, the running property and the winding property deteriorate, which is not preferable.

Further, the polyester B layer preferably contains inert particles β having an average particle size of 0.05 to 0.5 μm. The average particle size of the particles β is preferably 0.0
5 to 0.4 μm, more preferably 0.1 to 0.2
μm. When the average particle size exceeds 0.5 μm, the abrasion resistance deteriorates, and when the average particle size is less than 0.05, the running property deteriorates, which is not preferable.

The content of the particles β is 0.01 to
The content is 1.0% by weight, preferably 0.1 to 0.5% by weight, and more preferably 0.2 to 0.4% by weight. If the content exceeds 1.0% by weight, the abrasion resistance deteriorates, and if it is less than 0.01% by weight, the winding property deteriorates. Note that these inert particles α and β function as a lubricant.

In the laminated biaxially oriented polyester film of the present invention, the lubricant particles α,
It is preferable that at least one of β is selected from heat-resistant polymer particles and spherical silica particles, because the effect of improving abrasion resistance becomes more remarkable. Examples of the heat-resistant polymer particles include cross-linked polystyrene resin particles, cross-linked silicone resin particles, cross-linked acrylic resin particles, cross-linked styrene-acryl resin particles, cross-linked polyester particles, polyimide particles, and melamine resin particles. Among these, it is preferable to include crosslinked polystyrene resin particles or crosslinked silicone resin particles, because the effects of running properties and abrasion resistance become more remarkable.

In the laminated biaxially oriented polyester film of the present invention, the ratio (t) of the thickness tB of the polyester B layer to the average particle size dβ of the inactive particles β contained in the polyester B layer.
B / dβ) is preferably 10 to 30, and more preferably 1
It is preferably from 0 to 20. This ratio (tB / dII)
Is more than 30, the abrasion resistance is deteriorated. On the other hand, if it is 9 or less, the running property and the winding property are deteriorated.

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 manufactured by first producing an unoriented laminated film and then biaxially orienting the film. This unoriented laminated film can be produced by a conventionally accumulated method for producing 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, for example, it can be manufactured by a method such as coextrusion and extrusion lamination.

The film laminated by the above method can be further made into a biaxially oriented film in accordance with a conventionally accumulated method for producing a biaxially oriented film. For example, a polyester is melted and co-extruded at a temperature of melting point (Tm: ° C) to (Tm + 70) ° C to obtain an unstretched laminated film,
The unstretched laminated film is uniaxially (longitudinal or transverse) at a temperature of (Tg-10) to (Tg + 70) ° C. (Tg: glass transition temperature of polyester) at least 2.5 times, preferably 3 times. The film is stretched at the above magnification and then at a temperature of Tg to (Tg + 70) ° C. in a direction perpendicular to the stretching direction 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. In this way, the total stretching ratio is preferably 9 times or more as the area stretching ratio.
It is more preferably from 35 to 35 times, particularly preferably from 15 to 25 times. Furthermore, the biaxially oriented film is (Tg + 70) ° C.
It can be heat-set at a temperature of ~ (Tm-10) ° C, for example, preferably at 180-250 ° C. The heat setting time is preferably 1 to 60 seconds.

In the present invention, the laminated biaxially oriented polyester film obtained in this manner has a longitudinal direction (M
D) has a Young's modulus of 6 GPa / mm ² or more, preferably 6.5 GPa / mm ² or more, and more preferably 7.5 GPa / mm ² or more.
a / mm ² or more is desired. If the Young's modulus is less than 6 GPa / mm ² , the durability is insufficient when used as a magnetic recording medium, which is not preferable. Further, the Young's modulus in the width direction (TD) is 4 GPa / mm ² or more, preferably 4.5 GPa / mm ^2.
mm ² or more is desired. This Young's modulus is 4G
If it is less than Pa / mm ² , edge damage is likely to occur when a magnetic recording medium is used, which is not preferable.

The total thickness of the laminated biaxially oriented polyester film of the present invention is 2 to 10 μm, preferably 3 to 10 μm.
It is desired that the thickness be 8 μm, more preferably 4 to 6 μm. If the overall thickness is less than 2 μm, it is undesirably elongated. On the other hand, if the thickness is 10 μm or more, the thickness becomes large and it is difficult to increase the capacity.

The thickness of the polyester B layer is 0.5 to
It is preferably 2.5 μm, preferably 1-2 μm, more preferably 1.5-2 μm. When the polyester B layer is thinner than 0.5 μm, the number of inert particles contained in the B layer decreases, and the protrusion to the surface layer decreases,
Since the number of small protrusions on the surface background is reduced, the surface roughness is extremely reduced and the running property is deteriorated. 2.5
If the thickness exceeds μm, the particles contained in the B layer are more protruded from the surface of the A layer, and the surface of the A layer is roughened.

The laminated biaxially oriented polyester film of the present invention is suitable for use as a base film of a magnetic recording medium and also as a base film of a coating type magnetic recording medium, especially for a linear digital recording type magnetic recording medium. When used as is, excellent results can be obtained, which is preferable.

The following are examples of the magnetic recording medium of the present invention. Needle-like fine magnetic powder such as iron oxide or chromium oxide, or plate-like fine magnetic powder such as barium ferrite on a polyester A layer of a laminated biaxially oriented polyester film is coated with vinyl chloride, vinyl chloride / vinyl acetate copolymer, or the like. 1. Uniformly dispersed in a binder, the magnetic layer thickness is 2.
Electromagnetic conversion characteristics such as output in a short wavelength region, output, etc., particularly by coating in a thickness of 5 μm or less, preferably 0.1 to 1 μm and further providing a back coat layer on the surface of the polyester B layer by a known method. A coating-type magnetic recording medium with excellent error rate and low error rate. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like is dispersed and coated in the same organic binder as the magnetic layer as an underlayer of the oxide powder-containing magnetic layer on the layer A. You can also.
This coating type magnetic recording medium is a DL for data streamer.
It is useful as a digital recording type magnetic recording medium of a linear recording system such as T and QIC.

In the present invention, various physical properties and characteristics can be measured and evaluated as follows.

(1) Average Particle Size of Particles Centrifugal Particle Size Analyzer CP-50, manufactured by Shimadzu Corporation
alyzer). The particle size corresponding to 50% by mass was read from the integrated curve of the particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, and this value was defined as the above average particle size ("particle size measurement technology"). Nikkan Kogyo Shimbun, 1975, pp. 242 to 247).

(2) Content of Particles The solvent in which the polyester is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is defined as the particle content.
In some cases, the combined use of infrared spectroscopy is also effective.

(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 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 for the measurement are as follows. Primary ion species: O2 + Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6.0 × 10 ⁻³ Torr E-GUN: 0.5 KV− 3.0A

By the way, when 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-ray photoelectron spectroscopy), IR ( Infrared spectroscopy) may be used to measure the same depth profile as above to determine the surface layer thickness.

(4) Surface roughness a. WRa (2.5) Non-contact type three-dimensional surface roughness meter (manufactured by WYKO: NT-20)
00), measuring magnification 2.5 times, measuring area 2.5 mm
Under the condition of × 1.9 mm (4.75 mm ² ), the roughness of the film surface (A surface, B surface) is measured with the number of measurements (n) of 10 or more. Then, a calculation process represented by the following equation is performed by surface analysis software built in the roughness meter, and the center plane average roughnesses WRa (2.5) A and WRa (2.
5) Find B. In the following equation, _Zjk is the measurement direction (2.5
mm) and the direction perpendicular to it (1.9 mm) are the height on the two-dimensional roughness at the j-th and k-th positions in each direction when divided into m and n, respectively.

[0042]

(Equation 1)

B. WRa (25) Non-contact type three-dimensional surface roughness meter (manufactured by WYKO: NT-20)
00), measurement magnification 25 times, measurement area 246.6 μm
Under the conditions of mx187.5 μm (0.0462 mm ² ), the film surface (A surface, B
Surface) is measured. Then, using the surface analysis software built into this roughness meter, perform the calculation processing shown by the following equation,
Center surface average roughness WRa (25) A and W of each surface
Find Ra (25) B. In the following equation, Z _jk is the measurement direction (246.6 μm) and the direction perpendicular thereto (187.5).
μm) is the height on the two-dimensional roughness at the j-th and k-th positions in each direction when m division and n division, respectively.

[0044]

(Equation 2)

(5) Young's modulus of the film The film was cut into a sample having a width of 10 mm and a length of 150 mm, and the distance between the chucks was set to 100 mm. . The Young's modulus is calculated from the tangent at the rising portion of the obtained load-elongation curve.

(6) Electromagnetic conversion characteristics Detachable media evaluation device (MS: manufactured by Mediascope)
4500), and the output of the magnetic tape was measured.
With reference to Example 1 shown in Table 1 below. ◎: +3 dB or more ：: -3 dB or more to less than +3 dB ×: less than -3 dB The drive used here is of the DLT type.

(7) Winding property The film is wound at a speed of 200 m / min, and the wound film roll is observed to evaluate the winding property. <Judgment> ◎: No wrinkles or the like at all ○: Some wrinkles or the like are observed, but practically no problem x: Many wrinkles or the like occur

[0048]

Example 1 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and an average particle size of 0.1 μm for a layer A as a lubricant. 0.25% by weight of spherical silica particles, and 0.05% by weight of crosslinked silicone particles having an average particle size of 0.6 μm for the layer B,
And 0.4% by weight of alumina particles having an average particle diameter of 0.1 μm
Was added and the mixture was polymerized by a conventional method to obtain polyethylene terephthalate pellets for the A layer and the B layer having an intrinsic viscosity of 0.60. The polyethylene terephthalate pellets for the polyester A layer contained 0.25% by weight of spherical silica particles having an average particle size of 0.1 μm as inert particles. The polyethylene terephthalate pellets for the polyester B layer have an average particle diameter of 0.6 μm as inert particles.
m of crosslinked silicone particles and 0.4% by weight of alumina particles having an average particle size of 0.1 μm. Each of these pellets was dried at 170 ° C. for 3 hours, and then supplied to two extruder hoppers, melted at 300 ° C., and layer A was laminated on one side of layer B using a multi-manifold type coextrusion die. It was extruded onto a rotating cooling drum having a surface temperature of 20 ° C. with fine cracks formed on the surface to obtain a laminated unstretched film.

The thus obtained laminated unstretched film is preheated to 78 ° C., and further cooled between low-speed and high-speed rolls.
mm from above and stretched 2.3 times by heating with an infrared (IR) heater with a surface temperature of 850 ° C, quenched, and then supplied to a stenter, and stretched 3.6 times horizontally at 110 ° C. did. Subsequently, it is preheated at 110 ° C., stretched 2.0 times in the longitudinal direction between low-speed and high-speed rolls, further supplied to a stenter, and stretched 1.5 times in the transverse direction at 90 ° C. The obtained biaxially stretched film was heat-set with hot air at 220 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 6 μm. The thickness of each layer was adjusted by changing the discharge amounts of the two extruders. The Young's modulus of this film is 7.5 GPa / mm ^{2 in} the vertical direction and 4.5 G in the horizontal direction.
Pa / mm ² .

In order to manufacture a magnetic tape from the thus obtained laminated biaxially oriented polyester film, first, a material for a magnetic paint having the following composition was prepared. In addition, here, Sekisui Chemical S-LEC 7A was used as a vinyl chloride-vinyl acetate copolymer. Acicular Fe particles 100 parts by weight Vinyl chloride-vinyl acetate copolymer 15 parts by weight Thermoplastic polyurethane resin 5 parts by weight Chromium oxide 5 parts by weight Carbon 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 Cyclohexanone 50 parts by weight.

This material for magnetic paint is put into a ball mill,
After kneading and dispersing for 16 hours, 5 parts by weight of an isocyanate compound (Desmodur L manufactured by Bayer AG) was added, and the mixture was sheared and dispersed at a high speed for 1 hour to obtain a magnetic paint.

Further, a material for a non-magnetic base coating material was prepared by replacing the needle-like iron particle component in the above-mentioned magnetic coating material with 100 parts by weight of titanium oxide. This was treated in the same manner as the magnetic paint to produce a non-magnetic undercoat.

Further, a backcoat paint having the following composition was prepared. Here, Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd. was used as the isocyanate compound. Carbon black 100 parts by weight Thermoplastic polyurethane resin 60 parts by weight Isocyanate compound 18 parts by weight Silicone oil 0.5 part by weight Methyl ethyl ketone 250 parts by weight Toluene 50 parts by weight

First, on the one side (layer A) of the biaxially oriented laminated polyester film, the thus obtained non-magnetic undercoating and magnetic coating are applied in a multi-layered form, heated and dried at 100 ° C. 0.8 μm, the coating thickness of the magnetic layer was set to 0.2 μm, and then subjected to an orientation treatment in a DC magnetic field of 2500 Gauss, dried by heating at 100 ° C., and then subjected to a super calender treatment (linear pressure 300 kg / cm, temperature 80
° C) and wound up.

Further, the backcoat layer paint having the above composition was coated on the film opposite to the magnetic layer by a thickness of 0.5 μm.
The coated roll was dried, held in a 55 ° C. oven for 3 days, and then cut into イ ン チ inch width to obtain a magnetic tape.

The laminated biaxially oriented polyester film and the magnetic tape thus obtained were evaluated by the above-described evaluation methods. The results are shown in Table 1.

[0057]

Example 2 When a base film was produced in the same manner as in Example 1, the inert particles contained in the pellets for the polyester A layer were changed to spherical silica particles having an average particle size of 0.05 μm and the content was changed to 0. 0.01% by weight. Further inert particles to be contained in the polyester B layer pellets,
Content of crosslinked silicone particles having an average particle size of 0.5 μm is 0.
015 wt% and alumina particles having an average particle diameter of 0.1 μm were replaced with a content of 0.4 wt%. Further, the stretching ratio of the film was changed to 2.3 times the longitudinal stretching ratio, 4.5 times the transverse direction stretching ratio, 2.3 times the longitudinal direction stretching ratio, and 1.3 times the transverse direction stretching ratio. did.

A laminated biaxially oriented polyester film having a thickness of 6 μm was produced in the same manner as in Example 1 except for the other conditions. Further processing this film in the same manner as in Example 1,
A magnetic tape was manufactured. Table 1 shows the properties of the thus obtained laminated biaxially oriented polyester film and magnetic tape.

[0059]

Example 3 When a base film was produced in the same manner as in Example 1, the inert particles contained in the pellets for the polyester A layer were changed to spherical silica particles having an average particle size of 0.1 μm and the content was changed to 0. 0.01% by weight. Further, inert particles to be contained in the pellets for the polyester B layer include 0.15% by weight of spherical silica particles having an average particle diameter of 0.3 μm,
It was replaced with 0.2% by weight of spherical silica particles having an average particle size of 0.1 μm. Then, polyethylene-2,6-naphthalate (PEN) for a polyester AB layer was obtained in the same manner as in Example 1, except that dimethyl-2,6-naphthalate was used instead of dimethyl terephthalate.

The thus obtained pellets for the layer A and the layer B were dried at 170 ° C. for 6 hours, and a laminated unstretched film was obtained in the same manner as in Example 1. However, the surface temperature of the rotary cooling drum was set to 60 ° C. Subsequently, the laminated unstretched film was preheated at 120 ° C., further heated by an IR heater having a surface temperature of 900 ° C. from 15 mm above between low-speed and high-speed rolls, stretched 5.2 times, and rapidly cooled. Subsequently, it was supplied to a stenter and stretched 4.3 times in the horizontal direction at 145 ° C. The obtained biaxially stretched film was heat-set with hot air at 210 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 6 μm. Further, a magnetic tape was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and magnetic tape.

[0061]

Comparative Example 1 A laminated biaxially oriented polyester film having a thickness of 6 μm was obtained in the same manner as in Example 1 except that a flat rotary cooling drum having no cracks was used in the production of the base film. Further, a magnetic tape was prepared in the same manner as in Example 1. Table 2 shows the properties of the obtained laminated biaxially oriented polyester film and magnetic tape.

[0062]

Comparative Example 2 When a base film was produced in the same manner as in Example 1, the inert particles contained in the pellets for the polyester A layer were changed to spherical silica particles having an average particle diameter of 0.3 μm and the content was changed to 0. 0.1% by weight. Further, the inert particles contained in the pellets for the polyester B layer include crosslinked silicone particles having an average particle size of 0.5 μm having a content of 0.15%.
% Of alumina particles having an average particle size of 0.1 μm was replaced with 0.4% by weight.

A laminated biaxially oriented polyester film having a thickness of 6 μm was produced in the same manner as in Example 1 except for the other conditions. Further processing this film in the same manner as in Example 1,
A magnetic tape was manufactured. Table 2 shows the properties of the laminated biaxially oriented polyester film and the magnetic tape thus obtained.

[0064]

Comparative Example 3 When a base film was produced in the same manner as in Example 1, the pellets for the polyester A layer did not contain inert particles. Further, the inert particles contained in the pellets for the polyester B layer were replaced with only 0.2% by weight of spherical silica particles having an average particle diameter of 0.1 μm.

A laminated biaxially oriented polyester film having a thickness of 6 μm was manufactured in the same manner as in Example 1 except for the above conditions. Further processing this film in the same manner as in Example 1,
A magnetic tape was manufactured. Table 2 shows the properties of the laminated biaxially oriented polyester film and the magnetic tape thus obtained.

[0066]

Comparative Example 4 A polyethylene terephthalate pellet containing 0.2% by weight of crosslinked silicone particles having an average particle size of 0.5 μm and 0.4% by weight of alumina particles having an average particle size of 0.1 μm was dried at 170 ° C. for 3 hours. Thereafter, the mixture was supplied to an extruder hopper, melted at 300 ° C., extruded through a 1 mm slit die onto a rotating cooling drum having a mirror-finished surface temperature of 20 ° C., and an unstretched film having a thickness of 120 μm was obtained.

The unstretched film thus obtained was stretched in the same manner as in Example 1 to obtain a biaxially oriented polyester film having a thickness of 6 μm. It was created. Table 2 shows the properties of the obtained biaxially oriented polyester film and magnetic tape.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

As is clear from Tables 1 and 2, those according to the present invention (Examples 1 to 3) show excellent winding characteristics and electromagnetic conversion characteristics, but those which fall outside the present invention (comparative examples) Examples 1 to 4) were inferior in any of the characteristics.

That is, according to the present invention, a laminated biaxially oriented polyester film having excellent winding characteristics and electromagnetic conversion characteristics can be provided. This polyester film is useful as a base film for a magnetic recording medium, particularly as a base film for a linear digital recording magnetic recording medium.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 5/733 G11B 5/733 // B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 9 : 00 9:00 (72) Inventor Hirofumi Murooka 3-37-19 Koyama, Sagamihara-shi, Kanagawa Prefecture F-term in the Sagamihara Research Center, Teijin Limited (Reference) AK01B AK01H AK41A AK41B AK42 AK51 BA02 CA23A CA23B CA23H DE01B DE01H DE04B DE04H EH20 EJ38 GB41 JJ03B JJ03H JK15 JK15A JK15B JL02 YY00A YY00B 4F210 AA24 AB17 AC04 AG01 AG03 AH38 QC05 QC06 QG01 QG15 QG18 4J002 BC032 BC072 BG022 CC182 CF002 CF061 CF081 CM042 CP032 DJ016 FA082 FA086 GS01 5D006 CB01 CB07 CB08 EA01 FA09

Claims (11)

[Claims] 1. A laminated biaxially oriented film in which a polyester B layer is laminated on one side of a polyester A layer, which is measured at a magnification of 25 times using a non-contact three-dimensional surface roughness meter on the surface of the polyester A layer. Center surface roughness WRa (2
5) A is 2 to 10 nm, center plane average roughness WRa (2.5) A measured at a magnification of 2.5 was 3 to 10 nm, and magnification was measured using a non-contact three-dimensional surface roughness meter on the surface of the polyester B layer. 2
The center surface average roughness WRa (25) B measured at 5 times is 3 to
A laminated biaxially oriented polyester film, wherein the center plane average roughness WRa (2.5) B measured at 15 nm and further at a magnification of 2.5 is 5 to 15 nm. 2. WRa (2.5) A> WRa (25) A
The laminated biaxially oriented polyester film according to claim 1, wherein 3. The polyester A layer having an average particle size of 0.0
The laminated biaxially oriented polyester film according to any one of claims 1 to 2, comprising 0.005 to 0.5% by weight of inert particles of 1 to 0.6 µm. 4. The polyester B layer contains inactive particles α having an average particle diameter dα of 0.2 to 1.0 μm in an amount of 0.005 to 0.5 μm.
5% by weight and an average particle diameter dβ of 0.05 to 0.5
The laminated biaxially oriented polyester film according to any one of claims 1 to 3, which contains 0.01 to 1.0% by weight of inactive particles β of μm, and dα> dβ. 5. The laminated biaxially oriented polyester film according to claim 4, wherein at least one of the inert particles α and β is a particle selected from heat-resistant polymer particles and spherical silica particles. 6. The ratio (tB / dβ) of the thickness tB of the polyester B layer to the average particle size dβ of the inactive particles β is 10 to 3
The laminated biaxially oriented polyester film according to any one of claims 4 to 5, wherein the value is 0. 7. The laminated biaxially oriented polyester film according to claim 1, wherein the total thickness of the film is 2 to 10 μm. 8. The polyester B layer has a thickness of 0.5 to 0.5.
The laminated biaxially oriented polyester film according to claim 4, wherein the thickness is 2.5 µm. 9. The film has a Young's modulus in the longitudinal direction of 6 GP.
a / mm ² or more and Young's modulus in the lateral direction is 4 GPa / m
The laminated biaxially oriented polyester film according to any one of claims 1 to 8, wherein m is ² or more. 10. A magnetic recording medium having an information recording layer formed on a base film by a coating method, wherein the base film is the laminated biaxially oriented polyester film according to any one of claims 1 to 9. Magnetic recording medium. 11. The magnetic recording medium according to claim 10, wherein the information is recorded as digital information by a linear recording method.