JP3195235B2 - Laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film, and more particularly, to an excellent winding property, no defect, excellent slipperiness and handling property, and excellent electromagnetic conversion properties, dropout, running property and durability. The present invention relates to a laminated film useful as a base film for a high-density magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, remarkable progress has been made in increasing the density of magnetic recording. For example, a ferromagnetic metal thin film formed on a nonmagnetic support by a physical deposition method such as vacuum evaporation or sputtering or a plating method. Development and commercialization of thin-film magnetic recording media and thin-layer-coated magnetic recording media in which needle-shaped magnetic powder such as metal powder or iron oxide powder is applied to a thickness of 2 μm or less are in progress.

Examples of the former include, for example, Co-deposited tape (Japanese Patent Laid-Open No. 54-147010), Co-Cr
Perpendicular magnetic recording medium made of an alloy (Japanese Unexamined Patent Publication No.
No. 06 is disclosed, and as an example of the latter, for example, high-density magnetic recording using an extremely thin layer-coated medium (IEICE Technical Report MR94-78 (1995-02)) and the like are known.

Conventional coating type magnetic recording media (magnetic recording media obtained by mixing a magnetic powder in an organic polymer binder and coating on a non-magnetic support) have a low recording density and a long recording wavelength. While the thickness of the magnetic layer is as thick as about 2 μm or more, the metal thin film formed by thin film forming means such as vacuum deposition, sputtering or ion plating is very thin, not more than 0.2 μm, and extremely thin. In the case of a layer coating type medium, the non-magnetic underlayer
A coating type magnetic layer having a thickness of 3 μm has been proposed and is very thin.

Therefore, in the above-described high-density magnetic recording medium, the surface condition of the non-magnetic support greatly affects the surface properties of the magnetic recording layer. In particular, in the case of a metal thin film type magnetic recording medium, The surface state of the non-magnetic support is directly expressed as irregularities on the surface of the magnetic recording layer, which causes noise in recording / reproducing signals. Therefore, it is desirable that the surface of the nonmagnetic support is as smooth as possible.

On the other hand, from the viewpoint of handling of a non-magnetic support (base film), such as film formation, transportation in the film formation process, scratching, winding and unwinding, if the film surface is too smooth, the film-film mutual The slipping property of the sheet deteriorates, the booking phenomenon occurs, the shape when wound on a roll (roll formation) deteriorates, the product yield decreases, and the product manufacturing cost increases. Therefore, it is desirable that the surface of the non-magnetic support (base film) is as rough as possible from the viewpoint of manufacturing cost.

As described above, the surface of the nonmagnetic support is required to be smooth from the viewpoint of electromagnetic conversion characteristics, and is required to be rough from the viewpoint of handling properties and film cost.

Further, in the case of a vapor-deposited metal thin film type magnetic recording medium, a serious problem when actually used is insufficient running property of the metal thin film surface. In the case of a coating type magnetic recording medium in which a magnetic substance powder is mixed into an organic polymer binder and applied to a base film, a lubricant is dispersed in the binder to improve the runnability of the magnetic surface. Although it is possible, in the case of a metal thin film type magnetic recording medium, such measures cannot be taken, and it is extremely difficult to maintain a stable running property. Has the disadvantage of

Therefore, in order to supply a base film for a high-density recording medium of excellent quality at a low cost, it is necessary to simultaneously satisfy the above two trade-offs.

As a specific method for this purpose, a method of applying a specific coating agent to the film surface to form a discontinuous film (Japanese Patent Publication No. 3-80410, Japanese Patent Application Laid-Open No. 60-1808).
39, JP-A-60-180838, JP-A-60-180837, JP-A-56-16937, JP-A-58-68223, and the like. Forming method (JP-A-5-194)
772, JP-A-5-210833), a method of forming a different surface by co-extrusion and the like (Japanese Patent Laid-Open No.
Japanese Unexamined Patent Publication (Kokai) No. 213657/1995, Japanese Patent Publication No. 7-80282), and a method using + or a combination of + (Japanese Patent Laid-Open No. 3-73409) have been proposed.

[0011]

However, in the method of forming a discontinuous film or a continuous film having fine irregularities, problems such as slipping and blocking between film and film can be solved. It is insufficient in handling points such as film formation, transportation, scratching, winding and unwinding in the film forming process, and it is suitable for application to base film for high density and large capacity magnetic recording media from the viewpoint of product yield and product cost. Has a problem. Similar problems also exist in the conventional co-extrusion technology or the combination of a co-extrusion technology with a discontinuous film or a continuous film. Further, in the case of a metal thin film type magnetic recording medium, there still remains a problem of running properties under high temperature and high humidity conditions.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a laminated film having excellent transportability, anti-scratching property and winding property in a film-forming process, and further having these properties, An object of the present invention is to provide an inexpensive biaxially oriented laminated film for a high-density magnetic recording medium that has excellent running properties under high-temperature and high-humidity conditions even when used for a thin-film magnetic recording medium.

[0013]

The present invention has the following arrangement to attain the object. Average particle size 10-5
0 nm, an inert particle C having a volume shape factor (F) of 0.1 to π / 6 is contained in such an amount that the frequency of protrusions on the surface becomes 2.0 to 50.0 particles / μm ² , and the height of the protrusions is 30% of the particle size of
The coating layer C having an average particle size of 40 to 4
On one surface of the thermoplastic resin layer A containing inactive particles A having a volume shape factor (F) of 0.1 to π / 6 and a projection frequency of 5,000 to 50,000 / mm ^2. A three-layer laminated film comprising a thermoplastic resin layer B containing inert particles B and having a rougher surface than the thermoplastic resin layer C on another surface of the thermoplastic resin layer A. The roughness profile measured in the direction of 0 ± 10 degrees with respect to the longitudinal direction on the surface of the coating layer C is 4 to 2500 undulations having a height of 2 to 85 nm and an average width of 20 to 500 μm.
A laminated film having a frequency of mm ² .

Examples of the thermoplastic resin in the present invention include polyester resins, polyamide resins, polyimide resins, polyether resins, polycarbonate resins, polyvinyl resins, and polyolefin resins. Among these, polyester-based resins, and aromatic polyesters are preferred.

Preferred aromatic polyesters include polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, and poly-1,4.
-Cyclohexylene dimethylene terephthalate, polyethylene 2,6 naphthalenedicarboxylate and the like. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are particularly preferred.

These polyesters may be homopolyesters or copolyesters. In the case of a copolyester, as a copolymerization component of polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate, for example, diethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyethylene glycol, p-xylene Glycol, diol component such as 1,4-cyclohexanedimethanol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (however, in the case of polyethylene 2,6 naphthalenedicarboxylate), 2,6- Naphthalenedicarboxylic acid (however, in the case of polyethylene terephthalate), a dicarboxylic acid component such as 5-sodium sulfoisophthalic acid, p
And oxycarboxylic acid components such as -oxyethoxybenzoic acid. The amount of these copolymer components is preferably at most 20 mol%, more preferably at most 10 mol%.

Further, a trifunctional or higher functional polyfunctional compound such as trimellitic acid or pyromellitic acid can be copolymerized. In this case, it is preferable to copolymerize the polymer in a substantially linear amount, for example, 2 mol% or less.

In the present invention, the biaxially oriented laminated film has a coating layer C, a thermoplastic resin layer A, and a thermoplastic resin layer B. Even if the thermoplastic resins of the layers A and B are the same, Although the objects of the present invention can be achieved even if they are different, the same resin is preferable. In particular, it is preferable that the layers A and B are made of polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate. Also,
The coating layer C may be the same as or different from the thermoplastic resin layer A or the thermoplastic resin layer B.

The laminated film of the present invention comprises a coating layer C, a layer having a flat surface (ie, a thermoplastic resin layer A), and a layer having a rough surface (ie, a layer having a rough surface).
It has a three- layer structure of a thermoplastic resin layer B).

The coating layer C has an average particle size of 10 to 50 nm,
Preferably 12 to 45 nm, more preferably 15 to 45 nm
inactive particles C having a volume shape factor of 0.1 to π / 6 and a projection frequency of 2.0 to 50.0 particles / μm ² ,
Preferably 3.0 to 40.0 units / [mu] m ^2, more preferably contain an amount containing 4.0 to 30.0 units / [mu] m ^2, and the projection height of the particles formed in the particle size of the particles C It is necessary to be 30% or more and less than 200%, preferably 40% to 180%, more preferably 50% to 160%.

When the average particle diameter of the inert particles C is less than 10 nm, the winding property as a base film is insufficient, and the degree of output deterioration due to repeated contact with the tape head is large (still durability). On the other hand, if it exceeds 50 nm, the electromagnetic conversion characteristics deteriorate.

The volume shape factor F of the inert particles C defined by the following equation (2) is more preferably from 0.3 to π /
6, and more preferably a substantially spherical or elliptical sphere of 0.4 to π / 6. This is because F is smaller than 0.1 and, for example, in the case of flaky particles, the roll formation at the time of winding the base film is deteriorated, and when the thin film magnetic recording medium is used, the magnetic characteristics of the thin film magnetic layer are deteriorated.

The shape of the inert particles A is a volume shape factor (F) defined by the following equation (2).

[0024]

## EQU2 ## F = V / D ³ (2)

Where F is the volume shape factor, V is the volume (μm ³ ) of the inert particles, and D is the maximum diameter (μm ) of the inert particles.
m) .

The material of the inert particles C is not particularly limited. For example, a heat-resistant polymer (crosslinked silicone resin,
Polystyrene, cross-linked styrene divinylbenzene copolymer, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine resin, etc.)
And inorganic fine particles such as silica, alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, and barium sulfate.
Particularly preferred are crosslinked silicone resin particles, silica, and particles having a core-shell structure (core: crosslinked polystyrene, silica, etc., shell: methyl methacrylate, etc.).

The frequency of surface protrusions in the coating layer C is 2.0 / μ.
If it is less than m ² , the roll formation of the base film is poor, and the output of the magnetic recording medium due to repeated contact with the head is greatly deteriorated (still characteristics are poor), which poses a practical problem. On the other hand, when it exceeds 50.0 particles / μm ² , the electromagnetic conversion characteristics are deteriorated, and the particles are liable to drop off, which is not preferable.

If the protrusion height of the coating layer C is less than 30% of the average particle size of the inert particles C, the friction with the head becomes too high when used as a magnetic recording medium. If the height of the protrusions is 200% or more of the average particle size of the inert particles C, the electromagnetic conversion characteristics deteriorate, which is not preferable.

The polymer material of the coating layer C may be the same as or different from the thermoplastic resin layer A or the thermoplastic resin layer B, and can be realized by, for example, a known co-extrusion method or an in-line or off-line coating method. Anything should do. As the binder resin when the coating layer C is formed by the coating method, for example, an aqueous polyester resin, an aqueous acrylic resin, an aqueous polyurethane resin, and the like are preferable, and an aqueous polyester resin is particularly preferable.

The aqueous polyester resin has an acid component such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, adipic acid,
Sebacic acid, dodecane ditrimellitic acid, succinic acid, 5
-Na sulfoisophthalic acid, 2-K sulfoterephthalic acid, trimellitic acid, trimesic acid, monopotassium trimellitic acid, polyvalent carboxylic acids such as p-hydroxybenzoic acid, and the glycol component is, for example, ethylene glycol, diethylene glycol, or propylene. Glycol,
Polyester mainly composed of polyhydric hydroxy compounds such as 1,4-butadinediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, p-xylylene glycol, dimethylolpropionic acid, and ethylene oxide adduct of bisphenol A A graft polymer or a block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or two types of polymers.
Core-shell). As the aqueous polyester resin, a type that dissolves, emulsifies, and finely disperses in water can be used freely, and these have, for example, a sulfonic acid group, a carboxylic acid group, and a polyether unit in the molecule for imparting hydrophilicity. It may be introduced.

The average thickness (t _C ) of the coating layer C is from 1 to 500.
nm, and the average particle size of the inert particles C is d _C
In this case, it is preferable that the relationship represented by the following expression (3) is satisfied.

[0032]

## EQU3 ## 0.1 ≦ t _C / d _C ≦ 10 (3)

One embodiment of the coating layer C in the present invention will be described below. The coating layer C is a coating liquid containing the particles C and the binder resin described above on one surface of the thermoplastic resin layer A,
It is preferably formed by applying and drying an aqueous coating solution, and the solid content of the coating solution is 1 to 10% by weight, and more preferably 1.
It is preferably from 5 to 8% by weight, particularly preferably from 2 to 6% by weight. Further, other components such as a surfactant, a stabilizer, a dispersant, a UV absorber, a thickener, and the like can be added to these coating liquids (preferably aqueous coating liquids), if desired.

The coating is preferably performed on the laminated thermoplastic resin film before the final stretching treatment, and is preferably stretched in at least one direction after the coating. Before or during this stretching, the coating film is dried. Among them, the coating is preferably performed on an unstretched laminated thermoplastic resin film or a longitudinally (uniaxially) stretched laminated thermoplastic resin film, particularly a longitudinally (uniaxially) stretched laminated thermoplastic resin film. The application method is not particularly limited, but examples include a roll coating method and a die coating method.

The flat thermoplastic resin layer A in the present invention has an average particle size of 40 to 400 nm, preferably 50 to 20 nm.
0 nm, more preferably 60 to 120 nm, and the frequency of surface protrusions when measuring the inactive particles A having a volume shape factor of 0.1 to π / 6 on the surface of the coating layer C is 5,000 to 50,000 / m
m ² , preferably 7500 to 40,000 pieces / mm ² , more preferably 30 to 30,000 pieces / mm ² .

If the frequency of protrusions on the surface is less than 5,000 / mm ² , the friction of the magnetic layer against the magnetic head is high, the durability of the magnetic layer for repeated running is poor, and the transportability and scratch resistance in the film forming process are reduced. The sticking property is also poor, which is not preferable. On the other hand, if the frequency of the projections is larger than 50,000 / mm ² , the dropout of the projections and the dropout will increase, which is not preferable.

The inert particles A have an average particle size of 40 nm.
If it is less than 10, the friction of the magnetic layer against the VTR head is high, the repetitive running durability of the magnetic layer is poor, and the transportability and scratch resistance in the film forming process are also poor. On the other hand, the average particle size is 400 n
If it is larger than m, the electromagnetic conversion characteristics as a high-density magnetic recording medium are hindered, which is not preferable.

The inert particles A have a volume shape factor (F) of 0.3 as defined by the equation (2) in the same manner as the inert particles C described above.
It is necessary to satisfy 1 to π / 6, but 0.3 to π /
6 is preferable, and a substantially sphere having a size of 0.4 to π / 6 or an elliptical sphere having a rugby ball shape is more preferable. This is because F is smaller than 0.1, and, for example, in the case of acicular particles, the magnetic properties of the thin film magnetic layer are deteriorated. Examples of the material include cross-linked silicone resin, polystyrene, cross-linked styrene divinyl benzene copolymer, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride, and poly (vinylidene fluoride). Acrylonitrile, organic polymer particles such as benzoguanamine resin, silica,
Any of inorganic fine particles such as alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, and barium sulfate may be used.

The thermoplastic resin layer C in the present invention has a height of 2 to 85 in the roughness profile measured in the direction of 0 ± 10 degrees with respect to the longitudinal direction of the film on the surface.
nm, preferably 2 to 50 nm, more preferably 2 to 2 nm.
5 nm, average width of 20 to 500 μm, preferably 20 to 500 μm
4 to 2500 undulations / mm ² , preferably 10 to 300 μm, more preferably 20 to 200 μm.
２０００2000 / mm ² , more preferably 10-1000
It has surface properties that are present at a frequency of pcs / mm ² .

If the undulations have a height of less than 2 nm or a width of more than 500 μm, the undulations may be transported during the film forming process.
It is insufficient in terms of film damage, winding of product rolls, blocking phenomenon between film and film, and running property of tape under high temperature and high humidity conditions when used for metal thin film deposited magnetic recording.

On the other hand, if the height of the undulations exceeds 85 nm, the electromagnetic conversion characteristics will be impaired, and it is not suitable as a base film for high-density magnetic recording. If the average width of the undulations is less than 20 μm, the undulation height is not more than 25 nm in the region where the undulation height is 25 nm or less, resulting in insufficient transportability and tape running property in the film forming process.

The direction of measurement of the undulation is 0 ± 10 degrees with respect to the longitudinal direction of the film. This is a magnetic recording system to which a high-density magnetic recording tape using a base film according to the present invention is applied. On the tape in the same direction as the track scanned by the head.

The undulations on the surface of the thermoplastic resin layer C are not limited by the method of forming the undulations. However, the undulating protrusions on the surface of the thermoplastic resin layer B due to the stretching of the inert particles B contained in the thermoplastic resin layer B are not limited. It is preferable to use the pushing action.

In order to exhibit this pushing-up action more efficiently, the average particle size of the inert particles B and the thermoplastic resin layer A
It is preferable that the thickness satisfy a specific relationship. That is, the inert particle B is a single particle or a particle having a different size.
It consists seed or more particles, the average particle size or a single particle an average particle size of the largest particles of two or more particles d _B (mu
m) and the thickness of the layer A is t _A (μm), the following equation (1)

[0045]

Equation 4] _{4 ≦ t A / d B ≦} 40 (1)

It is preferable to satisfy the following. The t _A / d _B is 4-25, further 4-16, particularly preferably 4-8.

The undulating protrusions have a very long width or period, especially compared to the wavelength (less than 1.0 μm) on the surface of the high-density magnetic recording medium. The height of the protrusions due to the fine particles of the thermoplastic resin layer A, the long-period undulation, and the thermoplastic resin layer B are equal to or less than the height of the protrusions based on the inactive particles, so that the electromagnetic conversion characteristics are not adversely affected. Due to the synergistic effect of the three rough surfaces, the problems of the conventional base film for high-density magnetic recording can be solved at once.

The thermoplastic resin layer A in the present invention has a surface roughness of 10 nm or less, more preferably 5 nm or less, especially 2 nm or less, as measured on the surface of the coating layer C, as measured on the center plane average roughness. In particular, it is preferably 1 nm or less. If the surface roughness exceeds 10 nm, electromagnetic conversion characteristics are undesirably reduced.

On the other hand, the thermoplastic resin layer B forming the rough surface in the present invention contains the inert particles B as described above. This surface has a surface roughness greater than that of the thermoplastic resin layer A. In other words, necessary to satisfy the center plane average roughness of the thermoplastic resin layer A were measured on the center surface average roughness Ra _B and the coating layer C surface of the thermoplastic resin layer B Ra _C Togashiki (4) It is.

[0050]

## EQU5 ## Ra _B > Ra _C (4)

Here, Ra _B and Ra _C are non-contact three-dimensional center plane average roughnesses measured on the outer surfaces of the thermoplastic resin layer B and the coating layer C, respectively.

Ra _B is at least 1 nm greater than Ra _C , and
It is preferably 5 nm or more. The center plane average roughness Ra _B is 2 nm or more and less than 15 nm, and 3
It is preferably from 10 to 10 nm, particularly preferably from 3 to 7 nm.

The surface roughness Ra _B of the thermoplastic resin layer _B is 15
If it is not less than nm, the height of the undulating protrusions on the surface of the coating layer C,
It is difficult for the average width to satisfy the above-mentioned requirements, and when the average width is less than 2 nm, the handling properties such as transportability and the running property of the tape are insufficient, which is not preferable. Further, when Ra _B is less than Ra _A , the handling properties such as transport, scratching, winding and unwinding in the base film forming process are deteriorated due to the flatness, and the slip property between the film and the film is also increased. As a result, the booking phenomenon occurs due to the deterioration, and the shape (roll formation) when wound on a roll is deteriorated, which leads to a decrease in productivity, a decrease in product yield, and an increase in product manufacturing cost, which is not preferable.

In order to impart the above-mentioned surface characteristics to the thermoplastic resin layer B and to develop the above-mentioned undulations on the surface of the coating layer C, the average particle diameter dB of the inert particles _B is 0.2 to 0.2. 1μ
m, more preferably 0.2 to 0.8 μm, particularly preferably 0.2 to 0.8 μm
It is preferably 0.6 μm. This average particle size d
_B means the average particle diameter when the inert particles consist of single particles, and the average particle diameter of the largest particle among these particles when the inert particles consist of two or more particles having different sizes.

[0055] As the inert particle B having an average particle diameter d _B, may be mentioned those exemplified as the inert particles A. Further, in the case where it is composed of two or more kinds of particles, the second,
As the third small particles, fine particles having an average particle diameter of 0.01 μm or more and 0.1 μm or less, for example, colloidal silica,
Fine particles such as alumina having crystal forms such as α, γ, δ, and θ can be preferably used. Inert particles A
Fine particles having an average particle diameter of 0.01 μm or more and 0.1 μm or less can be used.

The content of the fine particles is 0.001 to 5% by weight, more preferably 0.005 to 1% by weight, especially 0.01 to 5% by weight.
Preferably, it is 0.5% by weight.

In the present invention, the total thickness of the laminated film is
Usually 2.5 to 20 μm, preferably 3.0 to 10 μm,
More preferably, it is 4.0 to 10 μm. The layer thickness configuration of the flat layer A and the rough layer B is substantially thin (1 to 500 n
m) the surface of the coating layer C as preferred wavy projections described above occurs, the preferred and a thickness t _A of the average particle diameter d _B and the flat layer A of the inert particles B to be added to Somenso B Set to thickness. It has a thickness t _A of the flat layer A is 0.8μm or more,
The thickness t _B of the rough surface layer B is preferably 1/2 or more of the average particle diameter d _B of the inert particles B.

The laminated film comprising the thermoplastic resin layers A and B in the present invention can be manufactured by a conventionally known method or a method accumulated in the art.
Among them, it is preferable to produce by a coextrusion method. For example, in the case of a biaxially oriented polyester film, the extruding die or the base before the die (generally, the former is referred to as a multi-manifold method, and the latter is referred to as a feed block method), is incompatible with the polyester A of the flat layer containing the inert particles A described above. The polyester B of the rough surface layer containing the active particles B is laminated and compounded in a molten state to form a laminated structure having the above-mentioned preferred thickness ratio, and then formed into a film at a melting point Tm ° C. to (Tm + 70) ° C. from a die. After co-extrusion, the mixture is cooled and solidified at 40 to 90 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is uniaxially (longitudinal or lateral) in a conventional manner at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg: glass transition temperature of the polyester).
The film is stretched at a magnification of 5 to 8.0 times, preferably at a magnification of 3.0 to 7.5 times, and then has a Tg-
The film is stretched at a temperature of (Tg + 70) ° C. at a magnification of 2.5 to 8.0 times, preferably at a magnification of 3.0 to 7.5 times. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. That is, two-stage, three-stage, four-stage, or multi-stage stretching may be performed. The total stretching ratio is usually 9 times or more, preferably 12 to 35 times, more preferably 1 to 10 times as the area stretching ratio.
It is 5 to 26 times. Further subsequently, the biaxially oriented film is provided with excellent dimensional stability by heat set crystallization at a temperature of (Tg + 70) to (Tm-10) ° C, for example, 180 to 250 ° C. The heat setting time is 1 to 60.
Seconds are preferred.

By this method, a biaxially oriented laminated polyester film having good interlayer adhesion and satisfying the requirements of the present invention can be obtained.

The above example is suitable when both thermoplastic resin layers A and B are made of polyethylene 2,6 naphthalene dicarboxylate or polyethylene terephthalate.
The same applies to the case where only the layer A or only the layer B is made of polyethylene 2,6 naphthalene dicarboxylate or polyethylene terephthalate.

As described above, the coating layer C may be formed by a coating method, or may be formed by a co-extrusion method simultaneously with the layers A and B using a thermoplastic resin instead of a binder resin. .

In the production of the laminated film, the thermoplastic resin may optionally contain additives other than the above-mentioned inert particles, such as a stabilizer, a colorant, and a modifier for the specific electric resistance of the molten polymer.

In the present invention, in order to improve various performances such as head touch and running durability as a magnetic recording medium, and to achieve thinning at the same time, the Young's modulus of the laminated film is set in the vertical and horizontal directions, respectively. 450 kg / mm ² or more, 600 kg / mm ² or more, or 480 each
kg / mm ² or more, 680 kg / mm ² or more, especially 550 kg / mm ² or more, 800 kg / mm ² or more, especially 550 kg / mm ² or more, 1000 kg / m, respectively
m ² or more. The degree of crystallinity of the polyethylene terephthalate layer is preferably 30% to 50%, and the degree of crystallinity of the polyethylene 2,6 naphthalene dicarboxylate layer is preferably 28% to 38%. If any of them is below the lower limit, the heat shrinkage increases, and if it exceeds the upper limit, the abrasion resistance of the film deteriorates, and white powder is liable to be generated when the film slides on the roll or guide pin surface.

The laminated film of the present invention is formed on the surface of the coating layer C by a method such as vacuum evaporation, sputtering, or ion plating. A metal thin film layer is formed, and a protective layer such as diamond-like carbon (DLC) is formed on the surface of the metal thin film layer, if necessary,
By sequentially providing a fluorinated carboxylic acid-based lubricating layer and further providing a known back coat layer on the surface of the thermoplastic resin layer B side, output in a short wavelength region, electromagnetic conversion such as S / N, C / N, etc. It is possible to obtain a vapor-deposited magnetic recording medium for high-density recording that has excellent characteristics and low dropout and error rate. This vapor-deposited magnetic recording medium is extremely useful as a Hi8 for analog signal recording, a digital video cassette recorder (DVC) for digital signal recording, an 8 mm data, and a DDSIV tape medium.

The laminated film of the present invention further comprises a coating layer C
On the surface of, iron or fine needle-shaped magnetic powder containing iron as a main component is uniformly dispersed in a binder such as vinyl chloride, vinyl chloride / vinyl acetate copolymer, and the magnetic layer thickness is 1 μm or less, preferably 0.1 to By applying a coating having a thickness of 1.0 μm and further providing a back coat layer on the surface of the thermoplastic resin layer B side by a known method, the output in a short wavelength region, particularly, S / S
Excellent electromagnetic conversion characteristics such as N, C / N, dropout,
A metal-coated magnetic recording medium for high-density recording with a low error rate can be obtained. If necessary, a non-magnetic layer containing fine titanium oxide particles or the like is dispersed and coated on the coating layer C in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. You can do it. This metal-coated magnetic recording medium includes 8 mm video for recording analog signals, Hi8, β cam SP, W-VHS, digital video cassette recorder (DVC) for recording digital signals, 8 mm data, DDSIV, digital β cam, It is extremely useful as a tape medium such as D2, D3, and SX.

The laminated film of the present invention further comprises a coating layer C
On the surface of, needle-shaped fine magnetic powder such as iron oxide or chromium oxide,
Alternatively, plate-like fine magnetic powder such as barium ferrite is uniformly dispersed in a binder such as vinyl chloride, vinyl chloride / vinyl acetate copolymer, and the thickness of the magnetic layer is 1 μm or less, preferably 0.1 to 1.0 μm. By coating and further providing a back coat layer on the surface of the thermoplastic resin layer B side by a known method, output in a short wavelength region, S / N, C
/ N and the like, and an oxide-coated magnetic recording medium for high-density recording with low dropout and low error rate can be provided. If necessary, a non-magnetic layer containing fine titanium oxide particles or the like is dispersed and coated on the layer A in the same organic binder as the magnetic layer as an underlayer of the magnetic layer containing the oxide magnetic powder. You can do it. The oxide-coated magnetic recording medium is useful as a high-density oxide magnetic recording medium such as a data streamer QIC for digital signal recording.

The above-mentioned W-VHS is an analog HDTV signal recording VTR, and DVC is a digital HDTV signal.
The film of the present invention is applicable to TV signal recording, and can be said to be a very useful base film for these HDTV-compatible VTR magnetic recording media.

[0068]

The present invention will be described below in more detail with reference to examples. The measuring method used in the present invention is as follows.

(1) Intrinsic Viscosity Number Determined from the value measured at 35 ° C. in an orthochlorophenol solvent.

(2) Average particle diameter I of the particles (average particle diameter: 0.
06μm or more) Shimadzu CP-50 Centrifugal Particle Size Analyzer (Centrifuga)
l Particle Size Analyzer)
It measured using. 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% by mass was read, and this value was referred to as the average particle size. ("Book Particle Size Measurement Technology", published by Nikkan Kogyo Shimbun, 1975, pages 242 to 24)
7).

(3) Average particle size II of particles (average particle size: 0.
Particles having an average particle size of less than 0.06, which form small projections, were measured using a light scattering method. That is, Nicomp Inst
devices Inc. NICOMMODE MODEL
L 270 SUBMICRON PARTICLE
The particle size was represented by the "equivalent spherical diameter" of the particle at a point of 50% by weight of all the particles determined by Sizer.

(4) Volume Shape Count F A photograph of each particle was taken with a scanning electron microscope at a magnification corresponding to the size used, and the maximum diameter of the projected surface was measured using an image analysis processor Luzex 500 (manufactured by Nippon Regulator). And the volume of the particles were calculated by the following equation (5).

[0073]

F = V / D ³ (5)

In the formula, V represents the volume of the particle (μm ³ ), and D represents the maximum diameter (μm) of the projection surface.

(5) Frequency of Surface Particles of Thermoplastic Resin Layer A The frequency of particles on the surface of the thermoplastic resin layer A was measured by a scanning electron microscope. That is, five photographs of particles on the surface of the thermoplastic resin layer A from the surface of the coating layer C were randomly taken at a magnification of 5,000 or 10,000 times, the frequency of the surface particles was counted, and the average value per 1 mm ² was obtained. This value was taken as the particle frequency on the surface of the thermoplastic resin layer A.

(6) Frequency of protrusions on the surface of the coating layer C The frequency of protrusions on the surface of the coating layer C was measured by a scanning electron microscope. That is, the photograph of the surface of the coating layer C was magnified by 3
Thirty images were taken randomly at 0000 times, the surface particle frequency was counted, the average value was converted to the number of particles per 1 mm ² , and this value was used as the surface protrusion frequency of the coating layer C.

(7) Layer Thickness The total thickness of the film was randomly determined by a micrometer.
The points were measured and indicated by the average value. The layer thickness was measured by measuring the layer thickness on the thin side by the method described below, and the layer thickness on the thick side was obtained by subtracting the layer thickness on the thinner side than the total thickness. That is, using a secondary ion mass spectrometer (SIMS), the concentration ratio (M ⁺ /) of the element resulting from the highest concentration of the particles in the film having a depth of 5000 nm from the surface layer to the carbon element of the polyester. C ⁺ ) as the particle concentration and a depth of 5000 from the surface
Analysis in the thickness direction was performed up to 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. In the case of the present invention, there are cases where the particle concentration once reaches a stable value 1 and then increases or decreases to a stable value 2 and cases where it monotonously decreases. Based on this distribution curve, in the former case, (stable value 1 + stable value 2) /
2 and, in the latter case, a depth at which the particle concentration becomes 1/2 of the stable value 1 (this depth is deeper than the depth at which the stable value 1 is given) and the layer thickness of the layer. did. The measurement conditions are as follows. Measurement device Secondary ion mass spectrometer (SIMS); Physical Elect
6300 SIMS manufactured by ronics Measurement conditions Primary ion species: O2 + Secondary ion polarity: Positive ion Incident angle: 60 ° Primary ion energy: 2 keV (1 keV / particle) Primary ion current amount: 200 nA Raster area: 400 μm × 400 μm Analysis area: 120 μm × 120 μm electron beam correction: yes

When the particles most contained in the range of 5000 nm from the surface layer are organic polymer particles other than silicone resin, it is difficult to measure by SIMS. Therefore, FT-IR (Fourier transform infrared spectroscopy) is performed while etching from the surface. Method), and for some particles, the same concentration distribution curve as above was measured by XPS (X-ray high electron spectroscopy) or the like, and the layer thickness was determined.

(8) Undulating protrusions on the film surface Using a non-contact three-dimensional roughness meter (TOPO-3D) manufactured by WYKO, a measurement magnification of 40 times and a measuring area were determined according to the size and height of the undulating projections. 234 μm × 240 μm (0.056
mm ² ) or measurement magnification 10 times, measurement area 956 μm
The size was measured at 980 μm (0.937 mm ² ), and the undulation height and average width were read from the obtained three-dimensional chart. The measurement was performed on a sample cut in a direction of 5 to 10 degrees with respect to the longitudinal direction of the film.

(9) Non-contact three-dimensional center plane average roughness (R
a) Using a non-contact three-dimensional roughness meter (TOPO-3D) manufactured by WYKO, a measurement magnification of 40 times and a measurement area of 242 μm × 239.
The measurement was performed under the condition of μm (0.058 mm ² ), and Ra was used as a value calculated and output by the following equation (6) from the surface analysis using the built-in software of the roughness meter.

[0081]

(Equation 7)

Z _jk is divided into M in the measurement direction (242 μm) and the direction perpendicular thereto (239 μm).
3 at the j-th and k-th positions in each direction when divided
Defined by the height on the dimensional roughness chart.

(10) Young's Modulus Using a tensile tester manufactured by Toyo Baldwin Co., Ltd., a sample film having a length of 300 mm and a width of 12.7 mm was prepared in a room controlled at a temperature of 20 ° C. and a humidity of 50%. It was pulled at a strain rate of 10% / min, and was calculated by the following equation (7) using the first straight line portion of the tensile stress-strain curve.

[0084]

E = Δσ / Δε (7)

Here, E is Young's modulus (kg / mm ² ),
Δσ is the stress difference due to the original average cross-sectional area between two points on the straight line,
Δε is the strain difference between the same two points.

(11) Winding property After optimizing the winding conditions at the time of slitting, the width is 560 mm ×
A slit of 10 rolls was formed at a size of 9000 m, and the rollability was evaluated based on the following criteria based on the number of rolls that can be commercialized based on the occurrence of film wrinkles after standing for one week.

(12) Manufacture of Magnetic Tape and Evaluation of Properties Two layers of a 100% cobalt ferromagnetic thin film having a thickness of 0.2 μm were formed on the surface of the coating layer C of the biaxially oriented laminated film by a vacuum evaporation method. (Each layer thickness is about 0.1 μm), a diamond-like carbon (DLC) film and a fluorinated carboxylic acid-based lubricating layer are sequentially provided on the surface, and a back coat layer is formed on the surface of the thermoplastic resin layer B side by a known method. Was provided. Then, it slit into 8 mm width, and was loaded on a commercially available 8 mm video cassette. Next, the characteristics of the tape were measured using the following commercially available instruments. Equipment used: 8mm video tape recorder Sony Corporation EDV-6000 C / N measurement: Shivasoku Corporation Neusmeter

C / N Measurement A signal having a recording wavelength of 0.5 μm (frequency of about 7.4 MHz) was recorded, and the ratio of the value of the reproduced signal between 6.4 MHz and 7.4 MHz was defined as the C / N of the tape. The C / N of the 8 mm video tape was set to 0 dB and expressed as a relative value.

Runability under High Temperature and High Humidity After repeating recording and reproduction 500 times at normal speed under high temperature and high humidity of 40 ° C. and 80% RH, the C / N was measured, and the C / N was measured from the initial value. The deviation was determined based on the following criteria. ◎: +0.0 dB or more with respect to the reference value ○: -1.0 to +0.0 dB with respect to the reference value ×: less than -1.0 dB with respect to the reference value

Still Characteristics A video signal of 4.2 MHz was recorded on the above-mentioned vapor deposition tape,
The time until the reproduced output attenuated to 50% was measured. From this time, judgment was made according to the following criteria. ：: Time to decay to 50% is 120 minutes or more ：: Time to decay to 50% is 60 to 120 minutes ×: Time to decay to 50% is less than 60 minutes

(13) Scratch of the film The film was sampled from the final product roll after slitting, and the flat surface side surface was observed with an optical microscope at a magnification of 100 times.
The number of scratches in 20 visual fields was counted. The criteria are as follows.

(14) Projection height Using an atomic force microscope (AFM) Nano Scope II manufactured by Digital Instruments,
Rz (10-point average roughness) calculated by measuring an area of 2 μm × 2 μm by the number of pixels of 256 lines × 256 pixels
Was the projection height.

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 a lubricant as shown in Tables 1 and 2 were used. The active particles are added and polymerized by a conventional method to obtain an intrinsic viscosity of 0.1.
As a result, 60 polyethylene terephthalates for layers A and B (resin A and resin B, respectively) were obtained.

The resin A and the resin B were dried at 170 ° C. for 3 hours, respectively, and then supplied to two extruders.
The resin layer B was melted at 80 to 300 ° C., and a resin layer B was laminated on one side of the resin layer A using a multi-manifold type coextrusion die, and rapidly cooled to obtain an unstretched laminated film having a thickness of 83 μm.

The unstretched film obtained in this way is preheated, and the film temperature is reduced between low and high speed rolls.
In order to form a coating layer C on the side of the layer A of the longitudinally stretched film, the aqueous coating solution containing the resin and particle material shown in Table 1 (pre-solid A polyoxyethylene nonylphenyl ether having an HLB value of 17.1 as a surfactant (containing 15% by weight of the total solid content) was applied by a kiss coat method, and then the longitudinally stretched film was supplied to a stenter. Then, the film was stretched 4.1 times in the transverse direction at 110 ° C. The obtained biaxially stretched film was heat-fixed with hot air at 220 ° C. for 4 seconds to have a thickness of 9.8 μm.
m was obtained. The thickness of each layer was adjusted by changing the discharge amount of the two extruders. The Young's modulus of this film is 5
00kg / mm ^2, was transverse 700 kg / mm ^2.

[0096] surface properties of the film obtained in this manner, flat layer in the thickness t _A and the rough surface layer inert particles B contains the A, the ratio t _A and the average particle diameter d _B of the largest particles /
d _B, winding property, the characteristics of the ferromagnetic thin film deposition magnetic tape using this film are shown in Table 3.

[Examples 2 to 4 and Comparative Examples 1 to 6 and 9] The resins forming the coating layer C and the inert particles, the particles contained in the thermoplastic resin layers A and B, and the layer thicknesses are shown in Tables 1 and 2. A laminated biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film was changed as shown in FIG. However, in Comparative Example 4, no coating layer was provided. Comparative Example 9 is a conventional single-layer film. Table 3 shows the properties of the films thus obtained and the properties of the ferromagnetic thin film-deposited magnetic tape using these films.

Examples 5 to 9 and Comparative Examples 7 and 8 Example 1 was repeated except that the particles shown in Tables 1 and 2 were used and dimethyl 2,6-naphthalenedicarboxylate was used instead of dimethyl terephthalate. In the same manner as above, polyethylene 2,6 naphthalate (PE) for the flat layer A and the rough layer B
N) Resin A and resin B were obtained.

After drying each of the resin A and the resin B at 170 ° C. for 6 hours, the thickness of each layer was adjusted in the same manner as in Example 1.
Unstretched laminated films satisfying the respective examples and comparative examples were obtained.

The unstretched film thus obtained is preheated, and the film temperature is reduced between low and high speed rolls.
The film was stretched 3.6 times at 5 ° C., quenched, and then an aqueous coating solution of the coating layer C shown in Table 1 was applied in the same manner as in Example 1, then supplied to a stenter, and fed at 155 ° C. in the transverse direction. Stretched 6.0 times. The obtained biaxially stretched film was heat-set with hot air at 200 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 4.6 μm. The Young's modulus of these films is 560 kg / mm ^{2 in} the vertical direction and 1100 kg / m in the horizontal direction.
m ² . However, in Examples 7, 8 and 9, the vertical magnification was 4.
And 0 × horizontal magnification 5.0, the Young's modulus of the laminated biaxially oriented polyester film, the longitudinal direction 600 kg / mm ^2, was transverse 900 kg / mm ^2. Table 3 shows the properties of the films thus obtained and the properties of the ferromagnetic thin film-deposited magnetic tape using these films.

[0101]

[Table 1]

[0102]

[Table 2]

[0103]

[Table 3]

As is evident from Table 3, the laminated film according to the present invention has a very flat one side and excellent electromagnetic conversion characteristics, and at the same time, has a very small particle size and a specific shape contained in the coating layer C. Synergy due to the combination of fine particles contained in the thermoplastic resin layer A to form fine protrusions on the surface thereof and undulating protrusions having a low height and a large width that do not adversely affect electromagnetic characteristics. Due to the effect, it is extremely excellent in running durability and still characteristics under high temperature and high humidity when used as a magnetic recording medium, and as an extremely excellent base film due to the effects of both undulating projections and the rough surface on the opposite side. It has the rewinding property. On the other hand, the film according to the conventional technique shown in the comparative example cannot satisfy these four requirements at the same time.

[0105]

According to the present invention, high winding density, excellent defect-free properties, excellent slipperiness, and easy handling, and particularly high density with excellent electromagnetic conversion characteristics, dropout, running properties of the magnetic layer, and durability. A laminated film useful for use as a magnetic recording medium can be provided.

────────────────────────────────────────────────── ─── Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 EPAT (QUESTEL) WPI / L (QUESTEL)

Claims (15)

(57) [Claims] 1. An average particle diameter of 10 to 50 nm and a volume shape factor
(F) 0.1 to π / 6 inactive particles C are contained in such an amount that the frequency of protrusions on the surface is 2.0 to 50.0 particles / μm ² , and the height of the protrusions is 30 times the particle diameter of the particles. % Or less and less than 200% of the inactive particles A having an average particle diameter of 40 to 400 nm and a volume shape factor (F) of 0.1 to π / 6. mm ² of the thermoplastic resin layer A, which is provided on one surface of the thermoplastic resin layer A, and contains the inert particles B on the other surface of the thermoplastic resin layer A and contains the thermoplastic resin layer C.
3 in which a thermoplastic resin layer B having a rougher surface is laminated
A laminated film having a layered structure, in which the surface of the coating layer C has undulating protrusions having a height profile of 2 to 85 nm and an average width of 20 to 500 μm in a roughness profile of 0 ± 10 degrees with respect to the longitudinal direction. A laminated film having a frequency of 2500 pieces / mm ² . 2. The inert particle B is composed of a single particle or two or more types of particles having different sizes, and the average particle size of the single particle or the average particle size of the largest particle of the two or more types of particles is different from the average particle size. The laminated film according to claim 1, wherein the thickness of the plastic resin layer (A) satisfies the following expression (1). [Number 1] _{4 ≦ t A / d B ≦} 40 (1) where, t _A is the thickness of the thermoplastic resin layer A (μm), d _B is the average particle size or a single particle of two or more particles Is the average particle diameter (μm) of the largest particle. 3. The single particle of the inert particles B or the largest particle of the two or more particles has an average particle size of 0.2 to 1.
The laminated film according to claim 2, which has a thickness of 0 µm. 4. The center plane average roughness Ra _C of the surface of the coating layer _C.
Is 10 nm or less. 5. The laminated film according to claim 1, wherein the coating layer C is a film layer stretched in at least one direction. 6. The laminated film according to claim 1, wherein the center surface average roughness Ra _B of the surface of the thermoplastic resin layer _B is 2 nm or more and less than 15 nm. In 7. The thickness of the thermoplastic resin layer A is 0.8μm or more, according to claim 1 or 2 thickness of the thermoplastic resin layer B is 1/2 or more the average particle diameter d _B of the inert particles B The laminated film according to the above. 8. The laminated film according to claim 1, wherein the total thickness is 2.5 to 20 μm. 9. The laminated film according to claim 1, wherein the thermoplastic resins of the layers A and B are each an aromatic polyester. 10. The laminated film according to claim 9, wherein the aromatic polyester is polyethylene terephthalate or polyethylene 2,6 naphthalenedicarboxylate. 11. The laminated film according to claim 1, which is a base film of a magnetic recording medium. 12. The laminated film according to claim 11, wherein the magnetic recording medium is a metal thin film magnetic recording medium. 13. The magnetic recording medium according to claim 1, wherein the thickness of the magnetic layer is 1 μm.
The laminated film according to claim 11, which is used for the following coating type magnetic recording media. 14. The laminated film according to claim 11, wherein the magnetic recording medium is a digital signal recording type magnetic recording medium. 15. The laminated film according to claim 11, wherein the magnetic recording medium is for an HDTV signal recording type magnetic recording medium.