JPH09226063A - Laminated film - Google Patents

Abstract

(57) [Abstract] [Problem] Excellent winding property, slipperiness, and handling property,
In particular, the present invention provides a laminated film useful as a base film of a magnetic recording medium, which is excellent in electromagnetic conversion characteristics, dropout, running property, and durability. SOLUTION: A thermoplastic resin layer B containing inert particles is laminated on one surface of a thermoplastic resin layer A which does not substantially contain particles, and the other surface of the thermoplastic resin layer A is averaged on the other surface. Particle size 10 to 50 nm, volumetric shape factor 0.1
A laminated film in which a coating layer C containing ~ π / 6 inactive particles C is laminated, and the surface of the coating layer C has a height of 30% or more of the average particle diameter of the inert particles C of 200 or more. % Fine protrusions at a frequency of ² to 20 million pieces / mm ² , and a wavy protrusion having a height of 2 to 85 nm and an average width of 20 to 500 μm in a direction of 0 ± 10 degrees with respect to the longitudinal direction of the film. the multilayer film characterized by having a frequency of from 4 to 2,500 pieces / mm ^2.

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 specifically, it has excellent winding properties, slipperiness, handling properties, etc., and particularly electromagnetic conversion properties, dropouts, running properties,
The present invention relates to a laminated film useful as a base film of a magnetic recording medium having excellent durability.

[0002]

2. Description of the Related Art In recent years, remarkable progress has been made in increasing the density of magnetic recording media. For example, a metal thin film in which a ferromagnetic metal thin film is formed on a nonmagnetic support by a physical deposition method such as vacuum evaporation or sputtering or a plating method. The development and commercialization of a thin-layer coated magnetic recording medium in which a needle-shaped magnetic powder such as a metal powder or an iron oxide powder is coated to a thickness of 2 μm or less has been promoted. Examples of the former include, for example, a vapor deposition tape of Co (JP-A-54-147010) and a perpendicular magnetic recording medium made of a Co-Cr alloy (JP-A-52-134706).
For example, high density magnetic recording using an ultrathin coating magnetic recording medium (Technical Report of the Institute of Electronics and Communication Engineers MR94-78 (1995-02)) and the like are known. .

Conventional coating type magnetic recording media (magnetic recording media obtained by mixing 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 layer is as thick as about 2 μm or more, the ferromagnetic metal thin film formed by thin film forming means such as vacuum deposition, sputtering or ion plating has a very thin thickness of 0.2 μm or less and is extremely thin. Also in the case of the layer coating type, although the non-magnetic underlayer is provided,
A thickness of μm has been proposed and is very thin.

Therefore, in the above-mentioned high density magnetic recording medium, the surface condition of the non-magnetic support (base film) has a great influence on the surface property of the magnetic layer, especially in the case of a metal thin film type magnetic recording medium. Means that the surface condition of the non-magnetic support is expressed as it is as unevenness on the surface of the magnetic layer (magnetic recording layer),
That causes noise in the recording / playback signal. Therefore, it is desirable that the surface of the non-magnetic support is as smooth as possible.

On the other hand, from the viewpoint of handling such as film formation of the non-magnetic support (base film), conveyance in the film forming process, scratches, winding, and unwinding, if the film surface is too smooth, the film-film mutual action is prevented. Slipping property deteriorates, a booking phenomenon occurs, the shape when rolled into a roll (roll formation) deteriorates, product yield decreases,
As a result, the production cost of the product increases. Therefore, from the viewpoint of manufacturing cost, a non-magnetic support (base film)
Is desirably as rough as possible.

As described above, the surface of the non-magnetic 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 the metal thin film type magnetic recording medium, the running property of the metal thin film surface is a serious problem when it is actually used. In the case of a coating type magnetic recording medium prepared by mixing magnetic powder in an organic polymer bander and coating the base film, a lubricant may be dispersed in the binder to improve the running property of the magnetic layer surface. I can, but
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. Have. Further, in this case, there is also a drawback that the output value after repeated use is large as compared with the coating type magnetic recording medium.

Therefore, in order to manufacture a high-density magnetic recording medium of excellent quality, it is necessary to satisfy the above-mentioned trade-off properties at the same time.

As a specific method for this purpose, a method of applying a specific coating agent to the surface of the film to form a discontinuous film (Japanese Patent Publication No. 3-80410, JP-A-60-180839).
No., JP-A-60-180838, JP-A-60-180
No. 837, JP-A-56-16937, JP-A-58-6
No. 8223), and a method of coating and forming a continuous film having fine irregularities on the surface of the film (JP-A-5-194772).
No. 5-210833), and a method of making the front and back surfaces different by a technique such as a coextrusion method (JP-A-2-214657).
No. 7-80282), or a method in combination with (Japanese Patent Application Laid-Open No. 3-73409).

[0010]

However, in the method for coating and forming the discontinuous film or the continuous film having fine irregularities, the problems such as film-to-film slippage and blocking can be solved, but the base film is solved. Film forming, transport in film forming process, scratching, winding, and unwinding are not sufficient in terms of handling, and from the viewpoint of product yield and product cost, it can be used as a base film for high-density and large-capacity magnetic recording media. There is a problem in application. Further, the conventional coextrusion technique or the technique of combining the coextrusion technique and the discontinuous coating or the continuous coating also has the same problem. Further, in the case of a metal thin film type magnetic recording medium, the problems of running property under high temperature and high humidity conditions and reduction of output during repeated use are still held.

The 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, scratch resistance, and winding property in the film forming process, and further, having these characteristics, and a metal thin film. (EN) Provided is an inexpensive biaxially oriented laminated film for a high-density magnetic recording medium, which is excellent in runnability under high temperature and high humidity conditions and retains output during repeated use even when used as a magnetic recording medium.

[0012]

The object of the present invention is, according to the invention, firstly: a thermoplastic resin containing inert particles on one surface of a substantially resin-free thermoplastic resin layer A. A resin layer B is laminated, and a coating layer C containing inert particles C having an average particle diameter of 10 to 50 nm and a volume shape factor of 0.1 to π / 6 is laminated on the other surface of the thermoplastic resin layer A. And the height of the surface of the coating layer C is 30% or more of the average particle diameter of the inert particles C and 200% or more.
% Fine protrusions at a frequency of ² to 20 million pieces / mm ² , and a height of 2 to 85 nm and an average width of 20 to 500 μm in a direction of 0 ± 10 degrees with respect to the longitudinal direction of the film.
This is achieved by a laminated film characterized in that it has waviness protrusions at a frequency of ⁴ to 2500 / mm ² .

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

As the aromatic polyester, polyethylene terephthalate, polyethylene isophthalate,
Preferably, polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate and the like can be preferably exemplified. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are preferred.

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

Further, a polyfunctional compound having three or more functional groups such as trimellitic acid and 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.

The above polyester is known per se, and can be produced by a method known per se.

In the present invention, the biaxially oriented laminated film has the thermoplastic resin layer A and the thermoplastic resin layer B, but the thermoplastic resins of the layer A and the layer B may be the same or different.
Among them, the same resin is preferable. In particular, layer A and layer B are polyethylene terephthalate or polyethylene-
It is preferably composed of 2,6-naphthalenedicarboxylate. As these polyesters, those having an intrinsic viscosity of about 0.4 to 0.9 measured at 35 ° C. as a solution in o-chlorophenol are preferred.

In the present invention, it is necessary that the thermoplastic resin layer A contains substantially no particles. Here, the phrase "substantially free of particles" means that it does not contain externally added particles or internally precipitated particles that form projections on the film surface, but may be caused by, for example, a catalyst essential for polymerization of polyester, Mean that a very small amount of particles that do not substantially exhibit the above-mentioned may be contained.

When the thermoplastic resin layer A contains externally-added particles or internally-added particles that form protrusions on the film surface, coarse protrusions are generated due to the overlapping of the particles, and in particular, vapor-deposited metal thin film magnetic When used as a recording medium, it becomes a defect that causes deterioration of electromagnetic conversion characteristics and increase of dropout. Further, in order to obtain the required frequency of surface protrusions, a large amount of particles are contained, which causes a problem of high cost.

If necessary, the thermoplastic resin layer A may contain other additives such as antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, etc. (excluding particles that form surface protrusions). Can be included.

In the laminated film of the present invention, as described above, the thermoplastic resin layer B containing the inert particles B must be laminated on one surface of the thermoplastic resin layer A containing substantially no particles. There is. This inert particle B is a layer B
It has the effect of forming a desired surface roughness on the surface of, and forming waviness-like projections on the surface of the layer A and further on the surface of the coating layer C. If the thermoplastic resin layer B containing the inert particles B is not laminated, the surface of the base film will be extremely flat, so that the base film may be conveyed, scratched, wound up or unwound in the film forming process. As a result of the deterioration of the handling property, and the deterioration of the film-to-film mutual sliding property, the booking phenomenon occurs, the shape when rolled into a roll (roll formation) deteriorates, productivity deteriorates, product yield decreases, and eventually Increases the manufacturing cost of products.

The surface of the thermoplastic resin layer B has a coating layer C.
It has a rougher surface roughness than the surface of. In other words, the thermoplastic resin layer center plane average roughness of the center surface average and roughness WRa ^B coating layer C of the B WRa ^C and the following formula 2

[0024]

[Expression 2] WRa ^B > WRa ^C ...... 2 Here, WRa ^B and WRa ^C are non-contact three-dimensional center plane average roughness measured on the outer surfaces of the thermoplastic resin layer B and the coating layer C, respectively. . To be satisfied. WRa ^B is WRa ^C
1 nm or more, and more preferably 1.5 nm or more. The center surface average roughness WRa ^B is 2 nm.
Or more and less than 15 nm, further 3 to 10 nm, especially 3 to 7 n
m is preferable.

The surface roughness WRa ^B of the thermoplastic resin layer ^B is 1
When the thickness is 5 nm or more, it is difficult for the height and average width of the wavy protrusions on the surface of the coating layer C to satisfy the requirements described later, and 2n
When it is less than m, handling property such as transportability and running property of the tape are insufficient, which is not preferable. Furthermore WRa ^B
Blocking phenomenon due to deterioration in the slipperiness of the film cross - but in the following WRa ^C, the transfer at the film forming process of the base film due to the flatness, scratches, winding, Kitaichi deterioration of handling property such as unwinding and film Occurs, the shape when rolled into a roll (roll formation) is deteriorated, productivity is deteriorated, product yield is reduced, and product manufacturing cost is increased, which is not preferable.

In order to impart the above-mentioned surface characteristics to the thermoplastic resin layer B and to cause the coating layer C to have a specific wavy projection, the average particle diameter dB of the inert particles _B is 0.2 to 1 μm, Further, it is preferably 0.2 to 0.8 μm, and particularly preferably 0.2 to 0.6 μm. This average particle diameter d _B is the average particle diameter of the inert particles B when it is composed of a single particle, and is the average particle diameter of the largest particles when it is composed of two or more kinds of particles of different sizes. Means diameter.

Examples of the inert particles having an average particle diameter d _B, for example, (1) particulate polymer particles (such as crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine - formaldehyde resin, aromatic polyamide resin, polyimide resin, (Polyamideimide resin, crosslinked polyester, etc.), (2) metal oxide (for example, amylnium oxide, titanium oxide, silicon dioxide, magnesium oxide,
Zinc oxide, zirconium oxide, etc.), (3) metal carbonates (eg magnesium carbonate, calcium carbonate, etc.),
Preferred are (4) metal sulfates (eg, calcium sulfate, barium sulfate, etc.), (5) carbon (eg, carbon black, graphite, diamond, etc.), and (6) clay minerals (eg, kaolin, clay, bentonite, etc.). To be Among these, crosslinked silicone resin particles, crosslinked polystyrene particles, melamine-formaldehyde resin particles, polyamideimide resin particles, aluminum oxide (alumina), titanium dioxide, silicon dioxide, zirconium oxide, calcium carbonate, barium sulfate, diamond and kaolin Preferred are crosslinked silicone resin particles, crosslinked polystyrene particles, alumina, titanium dioxide, silicon dioxide and calcium carbonate.

Further, when the particles are composed of two or more kinds of particles, the second and third small particles have an average particle diameter of 0.01 μm.
Fine particles having a size of 0.1 μm or more, for example, fine particles of colloidal silica, alumina having a crystal morphology of α, γ, δ, θ or the like can be preferably used. Further, among the particle species exemplified as the inert particles having the average particle diameter d _B , fine particles having an average particle diameter of 0.01 μm or more and 0.1 μm or less can also be used.

The content of the inert particles B is 0.001 to
5% by weight, further 0.005-1% by weight, especially 0.01
It is preferably about 0.5% by weight.

The laminated film of the present invention has an average particle size of 10 to 5 on the other surface of the thermoplastic resin layer A.
0 nm, preferably 12 to 45 nm, more preferably 1
Volume shape factor of 0.1 to π / 6, preferably 0.3 to π / 6, and more preferably 0.4 to π / 6 at 5 to 45 nm.
Inactive particles C of 2 million to 200
0,000 pieces / mm ² , preferably 2.5 to 18 million pieces /
mm ² , more preferably 3 to 15 million pieces / mm
It is necessary that the coating layer C contained in an amount of ² be laminated. The height of the fine protrusions is 30% or more and less than 200% of the average particle diameter of the inert particles C, preferably 40 to 180%,
More preferably, the protrusion is 50 to 160%.

When the average particle diameter of the above-mentioned inert particles C is less than 10 nm, there is no effect in improving the winding property and running durability.
If it exceeds 0 nm, the electromagnetic conversion characteristics deteriorate.

The volumetric shape factor (f) of the inert particles C is expressed by the following equation 3

[0033]

F = V / R ³ ...... 3 where f is the volume shape factor, and V is the volume of the particle (μ
m ³ ) and R are the average particle diameter (μm) of the particles. The shape with a volume shape factor of π / 6 is a sphere (true sphere)
It is. Therefore, the volume shape factor (f) is 0.4 to π / 6.
Those which substantially include spheres or true spheres and ellipsoidal spheres such as rugby balls, and these are particularly preferable. Particles having a volumetric shape factor (f) of less than 0.1, for example, flaky particles, are not preferable because they deteriorate the winding property during product slitting and deteriorate the magnetic properties of the magnetic layer.

When the surface protrusion frequency is less than 2 million pieces / mm ² , the winding property at the time of product slitting is poor, and when the magnetic recording medium is used, the degree of output deterioration due to repeated contact with the magnetic head (referred to as still characteristics) ) Is large, and there is a problem in practical use. On the other hand, if it exceeds 20 million pieces / mm ² ,
It adversely affects the electromagnetic conversion characteristics.

Further, the height of the fine protrusions is such that the inert particles C are
If the average particle size is less than 30%, the friction coefficient with the magnetic head becomes too high when used as a magnetic recording medium, and the still characteristics deteriorate. On the other hand, when the protrusion height is 200% or more of the average particle diameter of the inert particles C, the repeated running durability deteriorates when used as a magnetic recording medium.

The type of the above-mentioned inert particles C is not particularly limited, but those having a relatively low specific gravity, which does not easily settle in the coating liquid, are preferable. For example, particles made of heat resistant polymer (for example, crosslinked silicone resin, crosslinked acrylic resin, crosslinked polystyrene, melamine / formaldehyde resin, aromatic polyamide resin, polyamideimide resin, crosslinked polyester, wholly aromatic polyester, etc.), silicon dioxide (silica) ) And calcium carbonate are preferred.
Particularly preferred are crosslinked silicone resins, core / shell type organic particles (core: crosslinked polystyrene, shell: polymethylmethacrylate, etc.) and silica.

In the coating layer C of the present invention, a binder resin is used to fix the inert particles C, and examples of the binder resin include an aqueous polyester resin and
A water-based acrylic resin, a water-based polyurethane resin and the like are preferable, and a water-based polyester resin is particularly preferable.

The aqueous polyester resin has acid components such as isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid,
Sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-N
a Sulfoisophthalic acid, 2-K sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic acid monopotassium salt, polyvalent carboxylic acid such as P-hydroxybenzoic acid, and the glycol component is ethylene glycol,
Diethylene glycol, propylene glycol, 1,4
-Butanediol, 1,6-hexanediol, 1,4
-A polyester resin mainly composed of a polyvalent hydroxy compound such as cyclohexanedimethanol, P-xylylene glycol, dimethylolpropanoic acid, and an ethylene oxide adduct of bisphenol A can be preferably exemplified, and an acrylic polymer chain is bonded to the polyester chain. Graft polymers or block copolymers, or two polymers with specific physical composition (IPN,
An acrylic-modified polyester resin forming the core shell) may be used. As this aqueous polyester resin,
A type that dissolves, emulsifies, or finely disperses in water can be freely used, and in order to impart hydrophilicity, for example, a sulfonate group, a carboxylate group, a polyether unit, or the like may be introduced. .

The coating layer C in the present invention has, in addition to the above-mentioned fine projections on the surface thereof, 0 ± 0 in the longitudinal direction of the film.
The roughness profile measured in the direction of 10 degrees has a height of 2 to 85 nm, preferably 2 to 50 nm, more preferably 2 to 25 nm, and an average width of 20 to 500 μm, preferably 20 to 300 μm, and more preferably 20 to 200 μm. 4 to 2500 protrusions / mm ² , preferably 9
1,600 pieces / mm ^2, more preferably has a surface characteristic that is present at a frequency of 16 to 900 pieces / mm ^2.

The wavy protrusions have a height of less than 2 nm, a width of more than 500 μm, or a frequency of 4 /
If it is less than mm ² , it may be conveyed in the film forming process, the film may be scratched, the product roll may be wound, the film-to-film blocking phenomenon may occur, and the film may be used for metal thin film type magnetic recording under high temperature and high humidity conditions. Is insufficient in terms of running property of the tape.

On the other hand, when the height of the wavy projections exceeds 85 μm or the frequency exceeds 2000 pieces / mm ² , the electromagnetic conversion characteristics are impaired, and it is not suitable as a base film for high density magnetic recording media. When the average width of the wavy projections is less than 20 μm, the height of the wavy projections is 25 nm or less, and the transportability in the film forming step and the tape running property are insufficient.

The measuring direction of the wavy projections is 0 ± 10 degrees with respect to the longitudinal direction of the film, which is the direction of the magnetic recording system to which the high density magnetic recording tape using the base film according to the present invention is applied. By aligning the same direction as the track that the magnetic head scans on the tape.

The waviness-like projections in the coating layer C are not restricted by the formation method thereof, but the pushing-up action of the layer A associated with the stretching of the inert particles B contained in the thermoplastic resin layer B, and further, It is preferable that the undulation projections formed on the surface of the layer A act.

In order to develop this pushing-up effect more efficiently, the average particle size of the inert particles B and the thermoplastic resin layer A are
It is preferable that the thickness and the thickness satisfy a specific relationship. That is, the inert particles B are composed of a single particle or two or more kinds of particles having different sizes, and the average particle diameter of the single particle or the largest particle of the two or more kinds of particles is d _B.
(Μm) and the thickness of the layer A is t _A (μm), the following equation 1

[0045]

## EQU4 ## It is preferable to satisfy 4 ≦ t _A / d _B ≦ 40. This t _A / d _B is preferably 4 to 25, more preferably 4 to 16, and especially 4 to 8.

The wavy protrusions have a very long width or period, particularly in comparison with the wavelength (less than 1.0 μm) on the surface of the high density magnetic recording medium, and the fine inert particles C contained in the coating layer C have the same shape. Since it is equal to or lower than the height of the protrusion based on it,
A conventional high-density magnetic recording medium is produced by the synergistic effect of the projections of the fine particles C of the coating layer C, the long-term undulation, and the rough surface of the thermoplastic resin layer B, without adversely affecting the electromagnetic conversion characteristics. This is to solve all the problems that the base film for mobile phones had.

The surface roughness of the coating layer C in the present invention is preferably not more than 10 nm, more preferably not more than 5 nm, especially not more than 2 nm, especially not more than 1 nm in terms of center plane average roughness (WRa ^C ). . If the surface roughness is too rough, electromagnetic conversion characteristics and the like are deteriorated, which is not preferable.

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 constitution of the thermoplastic resin layer A and the thermoplastic resin layer B is such that the average particle size db of the inert particles B added to the layer _B and the layer A of the layer A are such that waviness-like protrusions are formed on the surface of the layer A. _A suitable thickness is set based on the layer thickness t _A. It is preferable that the thickness t _A of the layer A is at 0.8μm or more, and the thickness t _B of the layer B is 1/2 times or more the average particle diameter d _B of the inert particles B ([mu] m) .
The thickness of the coating layer C is 1 of the average particle diameter of the inert particles C.
/ 100 times or more and less than the average particle size (twice), more preferably 2/100 times or more of the average particle size and 80
/ 100 times or less, particularly preferably 3/10 of the average particle size
It is 0 times or more and less than 50/100 times.

The laminated film of the present invention can be manufactured by a conventionally known method or a method accumulated in the art. Among them, the laminated structure of the thermoplastic resin particles A and the thermoplastic resin B is preferably produced by a coextrusion method, and the coating layer C is preferably laminated by a coating method.

For example, a biaxially oriented polyester film will be described. Inside the extrusion die or before the die (generally, the former is called a multi-manifold system, the latter is called a feed block system), the polyester A containing no particles and the inert particles are used. Polyester B containing B is laminated and composited in a molten state to form a laminated structure having the above-mentioned suitable thickness ratio, and then coextruded into a film at a temperature of melting point Tm ° C to (Tm + 70) ° C from a die, It is rapidly cooled and solidified at 40 to 90 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is subjected to a temperature (Tg-10) to (Tg + 70) ° C. (where T
g: glass transition temperature of the polyester).
The film is stretched at a magnification of 0 times, preferably at a magnification of 3.0 to 7.5 times, and then Tg to (Tg + 7
0) The film is stretched at a temperature of ° C at a magnification of 2.5 to 8.0 times, and preferably at a magnification of 3.0 to 7.5 times. Further, if necessary, it may be stretched again in the machine direction and / or the transverse direction. That is,
It is preferable to perform two-stage, three-stage, four-stage, or multi-stage stretching. The total draw ratio is usually 9 times or more, preferably 12 to 35 times, more preferably 15 to 26 times as an area draw ratio. Subsequently, the biaxially oriented film was placed on the film (Tg + 7).
0) to (Tm-10) ° C, for example, 180 to 250
Excellent dimensional stability is imparted by heat set crystallization at ° C. The heat fixing time is preferably 1 to 60 seconds.

In the above method, the aforementioned inert particles C are used.
And a coating liquid containing a binder resin, preferably an aqueous coating liquid. The application is preferably performed on the surface of the polyester A before the final stretching treatment, and after the application, the film is preferably stretched in at least one direction. Before or during this stretching, the coating film is dried. Among them, the coating is preferably performed on an unstretched laminated film or a longitudinally (uniaxially) stretched laminated film, particularly a longitudinally (uniaxially) stretched laminated film. The coating method is not particularly limited, for example, roll coating method,
Examples thereof include die coating method.

The solid content of the above coating solution, especially the aqueous coating solution, is 1
It is preferably 10 to 10% by weight, more preferably 1.5 to 8% by weight, and particularly preferably 2 to 6% by weight. If desired, other components such as a surfactant, a stabilizer, a dispersant, a UV absorber, a thickener and the like can be added to the coating liquid (preferably an aqueous coating liquid).

The above examples are suitable when the thermoplastic resin layers A and B are both polyethylene-2,6-naphthalene dicarboxylate or polyethylene terephthalate, but only the layer A or the layer B is polyethylene-2. 6-
The same applies to naphthalene dicarboxylate or polyethylene terephthalate.

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 specific resistance adjusting agent for the molten polymer.

In the present invention, in order to improve various performances such as head touch as a magnetic recording medium and running durability, and at the same time to achieve a thin film, the Young's modulus of the laminated film in the longitudinal direction and in the lateral direction respectively. 450 kg / mm ² or more, 600 kg / mm ² or more, and further 480 kg / mm
² or more, 680 kg / mm ² or more, especially 550 kg / m
m ² or more, 800kg / mm ² or more, especially 550kg /
mm ² or more, and preferably 1000 kg / mm ² or more. Further, the crystallinity of the polyethylene terephthalate layer is preferably 30 to 50%, and the crystallinity of the polyethylene-2,6-naphthalenedicarboxylate layer is preferably 28 to 38%. If any of them is below the lower limit, the heat shrinkage increases, while 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 a ferromagnetic film made of iron, cobalt, chromium or an alloy or oxide containing these as the main components on the surface of the coating layer C by a method such as vacuum deposition, 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 for the purpose, purpose, and need.
By providing a fluorine-containing carboxylic acid type lubricating layer in sequence and further providing a known back coat layer on the surface of the thermoplastic resin layer B side, output in the short wavelength region, electromagnetic conversion characteristics such as S / N, C / N, etc. It is possible to provide a vapor-deposited magnetic recording medium for high density recording which is excellent in dropout and has a small error rate. This vapor-deposited electromagnetic recording medium is used for analog signal recording H
It is extremely useful as a tape medium for i8, digital video cassette recorder (DVC) for recording digital signals, data 8 mm, and DDSIV.

The laminated film of the present invention also has a coating layer C.
Iron or fine needle-shaped magnetic powder containing iron as a main component is uniformly dispersed in a binder such as polyvinyl chloride or vinyl chloride / vinyl acetate copolymer on the surface of, and the magnetic layer has a thickness of 1 μm or less, preferably 0.1 μm or less. To a coating layer having a thickness of 1 μm and a back coat layer formed on the surface of the thermoplastic resin layer B side by a known method so that the output, particularly in the short wavelength region, S
It is possible to obtain a metal-coated magnetic recording medium for high-density recording, which has excellent electromagnetic conversion characteristics such as / N and C / N, and has little dropout and error rate. Further, if necessary, a nonmagnetic layer containing fine titanium oxide particles or the like may be dispersed and coated on the layer A in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. You can also This metal coated magnetic recording medium is used for analog signal recording 8 mm video, Hi8, β-cam SP, W-VHS, digital signal recording digital video cassette coder (DV).
C), data 8 mm, DDSIV, digital β cam, D
It is extremely useful as a tape medium for 2, D3, SX, etc.

The laminated film of the present invention also has a coating layer C.
On the surface of, needle-shaped fine magnetic powder such as iron oxide or chromium oxide,
Alternatively, a plate-like fine magnetic powder such as barium ferrite is uniformly dispersed in a binder such as polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, etc., and applied so that the magnetic layer thickness is 1 μm or less, preferably 0.1 to 1 μm. In addition, by providing a back coat layer on the surface of the thermoplastic resin layer B side by a known method, the output, S / N, C, especially in the short wavelength region,
/ N or the like, and can be a vapor-deposited magnetic recording medium for high-density recording with low dropout and low error rate. Further, if necessary, a nonmagnetic layer containing fine titanium oxide particles or the like may be dispersed and coated on the layer A in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. You can also This oxide-coated magnetic recording medium is useful as a high-density oxide-coated 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 HD.
The film of the present invention is applicable to recording of a TV signal, and can be said to be a very useful base film for these magnetic recording media for HDTV-compatible VTRs.

[0060]

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 Determined from the value measured at 35 ° C. in an orthochlorophenol solvent.

(2) Average particle size I of particles (average particle size: 0.
06μm or more) Shimadzu CP-50 Centrifugal Particle Size Analyzer (Centrifugal Particle)
It is measured using a Size Analyzer). From the integrated curve of particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, the particle size “equivalent sphere diameter” corresponding to 50 mass percent is read, and this value is defined as the above average particle size. (Book
"Granularity measurement technology", published by Nikkan Kogyo Shimbun, 1975, page 2
42-247).

(3) Average particle size II (average particle size: 0.
Particles having an average particle size of less than 0.06 μm, which form small protrusions,
It is measured using a light scattering method. That is, Nicomp In
instruments Inc. NICOMP M
ODEL 270 SUBMICRON PARTIC
Expressed as the "equivalent spherical diameter" of the particle at the point of 50% by weight of the total particle as determined by LE SIZER.

(4) Volume shape factor f A photograph of each particle was taken at a magnification corresponding to the size used by a scanning electron microscope, and the maximum diameter of the projection surface was measured using an image analysis processor Luzex 500 (manufactured by Nippon Regulator). Then, the volume of the particles is calculated and calculated by the following formula.

[0065]

F = V / D ³ where f is the volume shape factor, V is the volume of the particle (μm ³ ),
D represents the maximum diameter (μm) of the projection surface.

(5) Frequency of protrusions on the surface of the film The frequency of protrusions on the surface of the film is measured by a scanning electron microscope. That is, the surface photograph of the laminated film is magnified 3000 times.
30 images were taken at random at 0 times, the surface protrusion frequency was counted, and the average value was converted into the number of protrusions per 1 mm ² , and this value was used as the film surface protrusion frequency.

(6) Layer Thickness 1) Thickness of thermoplastic resin layers A and B and total thickness The total thickness of the film is measured at 10 points randomly with a micrometer, and the average value thereof is used. The thickness of each of the layers A and B is determined by measuring the layer thickness on the thin side by the method described below, and the layer thickness on the thick side is obtained by subtracting the coating layer and the layer thickness on the thin side from the total thickness. That is, by using a secondary ion mass spectrometer (SIMS), the concentration of the element derived from the highest concentration of particles in the film in the depth range of 5000 nm from the surface layer excluding the coating layer and the carbon element of the polyester The ratio (M ⁺ / C ⁺ ) is the particle concentration, and the depth from the surface is 50
Analyze in the thickness direction up to 00 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 the particle concentration monotonously decreases. Based on this distribution curve, in the former case, (stable value 1 + stable value 2) / 2
Layer thickness of the layer with a depth that gives a particle concentration of, and in the case of the latter, a depth at which the particle concentration becomes 1/2 of a stable value of 1 (this depth is deeper than a depth that gives a stable value of 1). And

The measurement conditions are as follows. Measuring device Secondary ion mass spectrometer (SIMS); PERKIN
ELMER 6300 Measurement conditions 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 ⁻⁹ Torr E-GUNN: 0 When the particles most contained in the range of 5000 nm from the surface layer are organic polymer particles other than the silicone resin, SI
Since measurement is difficult with MS, the same concentration distribution curve as above is measured by FT-IR (Fourier transform infrared spectroscopy) while etching from the surface, or XPS (X-ray high electron spectroscopy) depending on the particles, and the layer is measured. Find the thickness. 2) Thickness of coating layer C A small piece of the film is fixedly molded with an epoxy resin, and an ultrathin section having a thickness of about 600 Å (cut parallel to the flow direction of the film) is prepared with a microtome.
This sample was subjected to a transmission electron microscope (H-80 manufactured by Hitachi, Ltd.).
(Type 0) and the thickness of the coating layer is determined by searching for the boundary surface of the coating layer C.

(7) Wavy protrusions on the film surface Using a non-contact three-dimensional roughness meter (TOPO-3D) manufactured by WYKO, according to the size and height of the wavy protrusions, the measurement magnification is 40 times and the measurement area is 234 μm × 240 μm (0.056
mm ² ), or measurement magnification 10 times, measurement area 956 μm ×
It is measured at 980 μm (0.937 mm ² ), and the height of waviness and the average width are read from the obtained three-dimensional roughness chart. The measurement was carried out on a sample cut in the direction of 5 to 10 degrees with respect to the longitudinal direction of the film.

(8) Center surface average roughness Using a non-contact three-dimensional roughness meter (TOPO-3D) manufactured by WRa WYKO, the measurement magnification is 40 times and the measurement area is 242 μm × 239 μ.
The measurement is performed under the condition of m (0.058 mm ² ), and from the surface analysis by the built-in software of the roughness meter, WRa uses a value calculated and output by the following equation.

[0071]

(Equation 6)

Z _jk is the measurement direction (242 μm), and the direction orthogonal to it (239 μm) is divided into M and N, respectively.
The height on the three-dimensional roughness chart at the j-th and k-th positions in each direction when divided.

(9) Protrusion Height Using an atomic force microscope (AFM) Nano Scope II manufactured by Digital Instruments, 2
An area of μm × 2 μm is measured by the number of pixels of 256 lines × 256 pixels, and Rz (10-point average roughness) calculated is defined as the protrusion height.

(10) Young's modulus Using a tensile tester Tensilon 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%. Tensile at a strain rate of 10% / min, calculated using the first linear part of the tensile stress-strain curve according to the formula:

[0075]

E = Δσ / Δε 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, and Δε is the same 2
It is the difference in strain between points.

(11) Winding property After optimizing the winding condition at the slit, a width of 700 mm ×
The length is 10000m, 30 rolls and speed 100
After slitting at m / min and leaving for 1 week, the occurrence of film wrinkles is closely examined up to the core layer, and the roll having no wrinkles is regarded as a good product, and the winding property is evaluated according to the following criteria.

[0077]

(12) Manufacture of magnetic tape and evaluation of characteristics On the surface of the coating layer C of the biaxially oriented laminated film, a ferromagnetic thin film of 100% cobalt of 0.02 μm was formed by a vacuum deposition method.
2 layers (each layer thickness about 0.1 μm) are formed to have a thickness of about 0.1 μm, and a diamond-like carbon (DLC)
A film and a fluorinated carboxylic acid-based lubricating layer are sequentially provided, and a back coat layer is provided on the surface of the thermoplastic resin B side by a known method. After that, slit to a width of 8 mm, 8 mm on the market
Load in video cassette. Next, the properties of the tape are measured using the following commercially available equipment.

Equipment used: 8 mm video tape recorder EDV manufactured by Sony Corporation
-6000 C / N measurement: Noise meter C / N measurement manufactured by Shibasoku Co., Ltd. A signal having a recording wavelength of 0.5 μm (frequency of about 7.4 MHz) was recorded, and the reproduced signal of 6.4 MHz and 7.4 MHz was recorded. The ratio is defined as the C / N of the tape, and the C / N of the commercially available vapor deposition tape for video of 8 mm is defined as OdB, and the relative values are shown. Running Durability After recording / reproducing was repeated 500 times at a tape running speed of 85 cm / min at 40 ° C. and 80% RH, C / N was measured, and the deviation from the initial value was judged according to the following criteria. ⊚: +0.0 dB or more with respect to the reference value ◯: 〃 −1.0 dB to +0.0 dB ×: 〃 less than −1.0 dB Still characteristics A video signal of 4.2 MHz is recorded on the above vapor deposition tape, and the time until the reproduction output is attenuated to 50% is measured. Judgment is made according to the following criteria from this time. ⊚: Decay time at 50% is 120 minutes or more ◯: 〃 60 minutes to 120 minutes ×: 〃 less than 60 minutes

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 inert particles shown in Table 1 as a lubricant. Layer A having an intrinsic viscosity of 0.60 after being added and polymerized by a conventional method
Terephthalate (PET) for layer B and
(Resin A and Resin B, respectively) were obtained.

Each of the resins A and B was dried at 170 ° C. for 3 hours, then fed to two extruders and melted at a temperature of 28.
The resin layer B was melted at 0 to 300 ° C., and the resin layer B was laminated on one surface of the resin layer A using a multi-manifold type coextrusion die, and was rapidly cooled to obtain an unstretched laminated film having a thickness of 87 μm.

The unstretched film obtained was preheated, and the film temperature was 3.3 at a film temperature of 100 ° C. between low speed and high speed rolls.
Double stretching, rapid cooling, and then an aqueous coating solution containing the binder resin and particles C shown in Table 2 on the layer A side of the longitudinally stretched film (total solid content concentration: 1.5% by weight, HLB value of 1 as a surfactant).
The polyoxyethylene nonyl phenyl ether of 7.1 was contained in the solid content in an amount of 15% by weight) was applied by a kiss coat method, subsequently supplied to a stenter, and stretched 4.2 times in the transverse direction at 110 ° C. The obtained biaxially stretched film was
The film was heat-set with hot air at 0 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 6.3 μm. The thickness of each layer was adjusted by the discharge amount of the two extruders. Young's modulus of the film is longitudinally 500 kg / mm ^2, it was transverse 700 kg / mm ^2.

[0083] surface properties of the laminated biaxially oriented film, of the inert particles contained in the thickness t _A and the layer B of the layer A, the largest ratio t _A / d _B between the average particle diameter d _B of the particle, wound Table 3 shows the workability and the characteristics of the ferromagnetic thin film vapor-deposited magnetic tape using this film.

[Examples 2 to 4, Comparative Examples 1 to 7 and 9] Tables 1 and 2 show the binder resin and particles of the coating layer C, the particles contained in the thermoplastic resin particle layers A and B, and the layer thickness. A laminated biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the above modification was made. However, in Comparative Example 4, the coating layer C was not provided. Comparative Example 9 is a film having a single layer structure. Table 3 shows the characteristics of the films thus obtained and the characteristics of the ferromagnetic thin film vapor-deposited magnetic tape using these films.

Examples 5 to 9 and Comparative Example 8 Same as Example 1 except that the particles B shown in Table 1 were used and dimethyl 2,6-naphthalenedicarboxylate was used in the same molar amount instead of dimethyl terephthalate. Polyethylene-2,6-naphthalate (PEN) (resin A, resin B) for layers A and B was obtained by the method of 1.

Each of the resins A and B was dried at 170 ° C. for 6 hours and the thickness of each layer was adjusted in the same manner as in Example 1 to obtain an unstretched laminated film satisfying each example and comparative example.

The unstretched film thus obtained is preheated, and the film temperature is set to 135 between the low speed and high speed rolls.
The film was stretched at a temperature of 3.6 ° C by 3.6 times and rapidly cooled, and then the aqueous coating solution of the coating layer C shown in Table 2 was applied in the same manner as in Example 1, followed by feeding to a stenter and then transversely at 155 ° C. It was 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. Young's modulus of these films is 560 kg / mm ^{2 in} the vertical direction and 1100 kg / mm in the horizontal direction.
^{Was 2} . However, in Example 5, the longitudinal magnification was 4.0 × the lateral magnification was 5.0, and the Young's modulus of the laminated biaxially oriented polyester film was 600 kg / mm ^{2 in the} longitudinal direction and 900 kg in the lateral direction.
/ Mm ² . Table 3 shows the characteristics of the films thus obtained and the characteristics of the ferromagnetic thin film vapor-deposited magnetic tape using these films.

As is clear 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, fine particles of a specific shape contained in the coating layer C and electromagnetic conversion characteristics. The high-temperature and high-humidity running durability when used as a magnetic recording medium and the still characteristics are excellent due to the synergistic effect of the low-height, large-width wavy protrusions that do not adversely affect the performance of the base film. It is also easy to handle. On the other hand, those which do not satisfy the requirements of the present invention cannot satisfy these characteristics at the same time.

[0089]

[Table 1]

[0090]

[Table 2]

[0091]

[Table 3]

[0092]

INDUSTRIAL APPLICABILITY According to the present invention, it is excellent in winding property, slipperiness, and handling property, and particularly for a high density magnetic recording medium excellent in electromagnetic conversion characteristics, dropout, running property of magnetic layer, and durability. Laminated films useful for use can be provided.

Claims (13)

[Claims] 1. A thermoplastic resin layer B containing inert particles is laminated on one surface of a substantially resin-free thermoplastic resin layer A, and the other surface of the thermoplastic resin layer A is laminated on the other surface. Average particle size 10 to 50 nm, volume shape factor 0.1
A laminated film in which a coating layer C containing ~ π / 6 inactive particles C is laminated, and the surface of the coating layer C has a height of 30% or more of the average particle diameter of the inert particles C of 200 or more. % Fine protrusions at a frequency of ² to 20 million pieces / mm ² , and a wavy protrusion having a height of 2 to 85 nm and an average width of 20 to 500 μm in a direction of 0 ± 10 degrees with respect to the longitudinal direction of the film. the multilayer film characterized by having a frequency of from 4 to 2,500 pieces / mm ^2. 2. The inert particle B is composed of a single particle or two or more kinds of particles having different sizes, and the average particle diameter of the single particle or the average particle diameter of the largest particle of the two or more kinds of particles and the thermoplastic resin layer. The laminated film according to claim 1, wherein the thickness of A satisfies the following formula 1. ## EQU1 ## 4 ≦ t _A / d _B ≦ 40 (1) where t _A is the thickness (μm) of the thermoplastic resin layer A, and d _B is the average particle size (μm) of single particles or two types. The average particle size (μm) of the largest particle among the above particles. 3. The laminated film according to claim 2, wherein the average particle diameter of the single particles of the inert particles B or the largest particle diameter of the two or more kinds of particles is 0.2 to 1 μm. 4. The center plane average roughness WRa of the surface of the coating layer C.
The laminated film according to claim 1, wherein ^C is 10 nm or less. 5. The laminated film according to claim 1, wherein the center plane average roughness WRa ^B of the surface of the thermoplastic resin layer ^B is 2 nm or more and less than 15 nm. 6. The thermoplastic resin layer A has a thickness of 0.8 μm or more, and the thermoplastic resin layer B has a thickness of ½ times or more of the average particle diameter d _B of the inert particles B. The laminated film described in 1. 7. The total thickness of the laminated film is 2.5 to 20 μm.
The laminated film according to claim 1, wherein the laminated film is m. 8. The laminated film according to claim 1, wherein the thermoplastic resin of each of the layers A and B is an aromatic polyester. 9. The laminated film according to claim 8, wherein the aromatic polyester is polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate. 10. The laminated film according to claim 1, which is a base film of a magnetic recording medium. 11. The laminated film according to claim 10, wherein the magnetic recording medium is a metal thin film type magnetic recording medium. 12. A magnetic recording medium having a magnetic layer thickness of 1 μm.
The laminated film according to claim 10, which is the following coating type magnetic recording medium. 13. The laminated film according to claim 10, 11 or 12, wherein the magnetic recording medium is a digital signal recording type magnetic recording medium.