JPH11309820A - Laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated film which is excellent in travel durability and electromagnetic conversion, has extremely reduced drop-out, and is good in blocking resistance and useful as a base film for magnetic recording medium by reducing large-sized projections which causes drop-out due to a coating film layer forming coating liquid. SOLUTION: In a laminated film comprising a base layer A of a thermoplastic resin A and a coating film layer B existing on one surface of the base layer A, the coating film layer B comprises a binder resin, inactive fine particles, and 1 surfactant, and the corona treatment blocking delamination of the layer B is 15 g/10 cm or below.

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 a laminated film which is excellent as a base film of a magnetic recording medium having excellent corona booking resistance, running durability, electromagnetic conversion characteristics and extremely low dropout. .

[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. Development and commercialization of a thin-film magnetic recording medium in which a needle-shaped magnetic powder such as a metal powder or an iron oxide powder is applied to a thickness of 2 μm or less have been promoted. An example of the former is disclosed in JP-A-54-147.
No. 010 discloses that the first Co thin-film magnetic layer having a thickness greater than the thickness of the first Co thin-film magnetic layer is interposed on the first Co thin-film magnetic layer adhered on the substrate made of the non-magnetic material via the non-magnetic material layer. 2nd C
o A magnetic recording medium having a thin film magnetic layer formed thereon is disclosed, and JP-A-52-134706 discloses Co-
A perpendicular magnetic recording medium made of a Cr alloy is disclosed.

As an example of the latter, the IEICE Technical Report MR94-78 (1995-02) discloses high-density magnetic recording using an extremely thin layer-coated magnetic recording medium.

[0004] 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 layer is as thick as about 2 μm or more, the ferromagnetic metal thin film formed by thin film forming means such as vacuum evaporation, sputtering or ion plating has a very thin thickness of 0.2 μm or less and is extremely thin. Also in the case of a layer coating type, although a non-magnetic underlayer is provided,
A thickness of 13 μm is provided and is very thin.

For this reason, in the above-described high-density magnetic recording medium, the surface condition of the non-magnetic support (base film) greatly affects the surface properties of the magnetic layer. , The surface state of the nonmagnetic support is directly expressed as irregularities on the surface of the magnetic layer (magnetic recording layer).

Further, in the case of the metal thin film type magnetic recording medium, a serious problem when actually used is the 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 running property of the magnetic layer surface. However, in the case of a metal thin-film magnetic recording medium, such measures cannot be taken, and it is extremely difficult to maintain a stable running property, and the running property is particularly poor under high temperature and high humidity conditions. It has disadvantages such as. Further, in this case, there is a drawback that the output decrease during repeated use is greater than that of the coating type magnetic recording medium.

In the case of a metal thin film type magnetic recording medium, the surface of the base film called ion bombardment is activated by ions before forming the metal thin film in order to improve the adhesion between the metal thin film and the base film. Processing is performed.

During the formation of the metal thin film, the back surface is cooled so that high-temperature heat is applied to the film surface and the base film is not melted or physical properties such as mechanical properties are not deteriorated. In many cases, the back surface cooling is performed by winding a base film around a drum-shaped cooling body. At this time, both ends of the base film are masked so that a thin metal film is not formed on the surface of the drum.

Therefore, portions where only the ion bombardment process is performed and a metal thin film is not formed are continuously generated in the same portion in the longitudinal direction of the film, and are both edges of the roll. Because the surface of the base film is ultra-flat, this portion is wound, whereby the activated base surface and the opposite base surface come into contact with each other, which easily causes blocking and causes process trouble.

On the other hand, from the viewpoint of handling such as film formation of the non-magnetic support (base film), transport / scratching, winding and unwinding in the processing step, if the film surface is too smooth, mutual contact between the film and the film may occur. Slipperiness is deteriorated, and here also, a blocking phenomenon occurs, and the shape when wound on a roll (roll formation) is deteriorated, resulting in a lower product yield and a higher product manufacturing cost.
Therefore, from the viewpoint of manufacturing cost, the surface of the nonmagnetic support (base film) is preferably 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.
Roughness is required from the viewpoint of blocking resistance, handling properties, and film cost. In particular, in order to improve the blocking resistance, a rough surface is required to reduce the contact area of the film.

Therefore, in order to manufacture a high-density magnetic recording medium of excellent quality, it is necessary to simultaneously satisfy the above two conflicting properties.

In Japanese Patent Application Laid-Open No. 5-194772, a primer layer for a magnetic layer, which is a continuous thin film, is coated on one surface of a polyester film, and the surface of the continuous thin film of the primer layer is (A). And (B) small protrusions having a height of 13 nm or less and having particles having an average particle diameter of less than 0.06 μm as nuclei.
30 n height with particles having an average particle size of 0.06 μm or more as nuclei
m and small projections made only of the resin forming the primer layer (C), and the number of these projections is represented by the following formula: A _N ≧ 1.0 × 10 ⁶ (pieces / mm ² ) B _N ≧ 1.05 × 10 ⁴ (pieces _{^{/ mm 2) A N ≦ -3.4}} × 10 2 · B N + 13.6 × 10 6 ( pieces _{^{/ mm 2) C N ≦ 4.0}} × 10 6 ( pieces / mm ² ) [However, A _N is the number of small projections (pieces / mm ² ), _BN is the number of large projections (pieces / mm ² ), and C _N is the number of minute projections (pieces / m ² ).
m ² ). ] Satisfied, and micro surface roughness Ra ^S only by a continuous thin film of the resin for forming the primer layer is not more than 1.10 nm, and a surface roughness Ra of the continuous film is 1 to 10 nm, the magnetic recording A polyester film for media is disclosed.

In Japanese Patent Application Laid-Open No. Hei 5-298670, a primer layer for a magnetic layer composed of a continuous thin film is coated on one surface of a polyester film, and the surface of the continuous thin film of the primer layer is (A). And (B) small protrusions having a height of 13 nm or less and having particles having an average particle diameter of less than 0.06 μm as nuclei.
30 n height with particles having an average particle size of 0.06 μm or more as nuclei
m and small protrusions having a maximum major axis of 0.30 μm or less are formed only by the resin forming the primer layer (C), and the number of these protrusions is represented by the following formula: A _N ≧ 1.0 × 10 ⁶ (Pcs / mm ² ) B _N ≧ 1.05 × 10 ⁴ (pcs / mm ² ) A _N ≦ −3.4 × 10 ² · B _N + 13.6 × 10 ⁶ (pcs / mm ² ) 1.0 × 10 (pieces / mm ² ) ≦ C _N ≦ 1.0 × 10
⁴ (pieces / mm ² ) [where, A _N is the number of small projections (pieces / mm ² ), _BN is the number of large projections (pieces / mm ² ), and C _N is the number of micro projections (pieces / m ² ).
m ² ). ] Satisfied, micro surface roughness Ra ^S of the continuous thin film portion by only the resin for forming the primer layer is not more than 1.10 nm, a further surface roughness Ra of the continuous film is 1 to 10 nm, and the As a continuous thin film, a polyester film for a magnetic recording medium is disclosed which can suppress the precipitation rate of polyester oligomer microcrystals on the film surface to 0.8% or less when the film is continuously heated in air at 160 ° C. for 5 minutes. .

According to the polyester film as described above, although the smoothing of the base film on the magnetic layer side can be realized to some extent, the problem of causing dropout due to the presence of the cohesive coarse projections derived from the coating layer is solved. I couldn't.

In the above method, particles are added to the base film on the side of the magnetic layer in order to improve running durability. However, since the particles have poor dispersibility, there are many coarse projections.
This causes problems such as dropout, and uneven output of the magnetic head, resulting in lower output.

Further, even with these treatments, the problem that the blocking phenomenon occurs at the roll edge activated by the ion bombardment treatment cannot be solved.

[0018]

An object of the present invention is to provide a laminated film useful as a base film for a magnetic recording medium.

Another object of the present invention is to significantly reduce coarse projections, which cause dropout, derived from a coating solution for forming a coating film layer, and have excellent running durability and electromagnetic conversion characteristics, and extremely low dropout. An object of the present invention is to provide a laminated film for providing a magnetic recording medium having a small amount and good blocking resistance. Still other objects and advantages of the present invention will become apparent from the following description.

[0020]

According to the present invention, the above objects and advantages of the present invention include a base layer A made of a thermoplastic resin A and a coating layer B present on one surface of the base layer A. Wherein the coating layer B comprises a binder resin, inert fine particles and a surfactant, and has a corona-treated blocking release of 15 g / 10 c.
m or less.

In the present invention, the thermoplastic resin A forming the base layer A includes polyester resin, polyamide resin, polyimide resin, polyether resin, polycarbonate resin, polyvinyl resin, polyolein resin and the like. Can be exemplified. Of these, polyester resins and aromatic polyesters are preferred.

As the aromatic polyester, polyethylene terephthalate, polyethylene isophthalate,
Preferable examples include polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, and polyethylene-2,6-naphthalenedicarboxylate. 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, copolymerization components of polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate include, for example, diethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyethylene glycol, Diol components such as 1,4-cyclohexanedimethanol, p-xylylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (provided that polyethylene-2,
6-naphthalene dicarboxylate), 2,6-
Other dicarboxylic acid components such as naphthalenedicarboxylic acid (in the case of polyethylene terephthalate), 5-sodium sulfoisophthalic acid, and oxycarboxylic acid components such as p-oxyethoxybenzoic acid are included. The amount of these copolymer components is 20 mol% or less, and more preferably 10 mol%.
It is preferable to set the following.

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

It will be understood that copolymerization components in the case of other polyesters than polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are considered in the same manner as described above.

The above-mentioned polyesters are known per se and can be produced by a method known per se.

The thermoplastic resin A forming the base layer A is
It may or may not substantially contain inert fine particles.

When having inert particles A, the inert fine particles preferably have an average particle diameter of 30 to 400 nm and a volume shape factor of 0.1 to π / 6.
It is. The average particle size is more preferably 40 to 200 n.
m, particularly preferably 50 to 120 nm. Further, the volume shape factor is more preferably 0.4 to π / 6.

Further, on the surface of the coating layer B on the side not in contact with the base layer A, 50,000 to 100,000 particles are formed due to the inert particles A contained in the thermoplastic resin A. It is preferable that the thermoplastic resin A contains the inert particles A at a rate at which protrusions are formed at a density of / mm ² . The projection density is more preferably 0.75 to 60,000 / mm ² , and still more preferably 10,000 to 30,000 / mm ² .

When the average particle diameter is less than 30 nm or when the projection density is less than 50,000 / mm ² , satisfactory running durability cannot be obtained, while when the average particle diameter exceeds 400 nm. When the protrusion density is more than 100,000 / mm ² , the electromagnetic conversion characteristics are inferior, which is not preferable.

The volume shape factor (f) of the particles is given by the following equation:

[0032]

F = V / R ³ [where f is the volume shape factor, and V is the volume of the particles (μ
m ³ ) and R are the average particle size (μm) of the particles. ]. A shape having a coefficient (f) of π / 6 is a sphere (true sphere). The shape having the coefficient (f) of 0.4 to π / 6 substantially includes a sphere (true sphere) and an elliptical sphere such as a rugby ball. It is difficult to obtain sufficient running durability with particles having a volume shape factor (f) of less than 0.1, for example, flaky particles.

In the laminated film of the present invention, a coating layer B containing a binder resin, inert fine particles and a surfactant is present on one surface of the base layer A.

As the binder resin, 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.

As the aqueous polyester resin, for example, the acid component is 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, monopotassium trimellitate, and at least one polyvalent carboxylic acid such as p-hydroxybenzoic acid. Polyhydric hydroxy such as glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, p-xylylene glycol, dimethylolpropane, and ethylene oxide adduct of bisphenol A A polyester resin mainly composed of one or more compounds is preferably used. Similarly, an acrylic modified polyester resin in which a graft polymer or a block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or an acrylic modified polyester resin in which two kinds of polymers form a specific physical configuration (IPN, core shell) in a micro molecule. Used.

As the aqueous polyester resin, any type which can be dissolved, emulsified or finely dispersed in water can be used freely, but a type which is emulsified or finely dispersed in water is preferable. These may have, for example, a sulfonic acid group, a carboxylic acid group, a polyether unit, or the like introduced into the molecule to impart hydrophilicity.

More preferably, the softening point (measured by drying the binder resin) measured in accordance with JIS K7206 is 50 ° C. or higher in order to improve the blocking resistance against corona treatment. However, if the Tg of the resin of the coating layer B is too high, the surface of the coating layer B may be roughened and the electromagnetic conversion characteristics may be poor depending on the coating conditions and the like.

Therefore, when a binder having a high Tg is used, it is necessary to devise coating conditions so as not to roughen the surface. The roughness in this case is AF
Mean square roughness measured at 10 μm square by M (scanning atomic force microscope), preferably 2.0 μm or less, more preferably 1.8 nm or less, particularly preferably 1.5 nm or less. It is.

The type of the inert fine particles is not particularly limited, but is preferably one having a relatively low specific gravity which does not easily settle in the coating liquid. For example, heat-resistant polymers (eg, cross-linked silicone resin, cross-linked acrylic resin, cross-linked polystyrene, melamine-formaldehyde resin, aromatic polyamide resin,
Particles composed of a polyamideimide resin, a crosslinked polyester, a wholly aromatic polyester, etc.), silicon dioxide (silica), calcium carbonate and the like are preferred. Among these, particularly preferred are crosslinked silicone resin particles, silica, and core-shell type organic particles (eg, core: crosslinked polystyrene, shell: polymethyl methacrylate particles, etc.).

These inert fine particles have an average particle size of 10
It is preferably in the range of ５０50 nm. The average particle size is more preferably from 15 to 45 nm, even more preferably from 18 to 40 nm.

These inert fine particles are contained in an amount of preferably 0.5 to 30% by weight, more preferably 2 to 20% by weight, based on the solid content of the coating layer B.

On the surface of the coating layer B which is not in contact with the base layer A, projections originating from inert fine particles contained in the coating layer B are preferably 1 to 40 / μm ² , more preferably Is 2 to 20 / m ² , particularly preferably 2.5 to 18
Particles / μm ² , especially at a density of 3 to 15 particles / μm ² .

On the surface of the coating layer B which is not in contact with the base layer A, coarse projections having a height of 4 nm or more calculated from a surface roughness profile obtained by a non-contact three-dimensional roughness meter are preferably used. May be present at a density of 200 particles / mm ² or less, more preferably 100 particles / mm ² or less, and excellent running durability is exhibited by the presence of the protrusions.

The surfactant (X) is used in an amount of 10 per solid content of the coating solution.
It is used in an amount of up to 50% by weight, preferably 12 to 40% by weight, particularly preferably 15 to 30% by weight.

The amount of the surfactant (X) is 10
When the amount is less than 50% by weight (based on total solids), it is not possible to suppress the generation of coarse projections that may cause dropout.
Streaky coating defects occur due to foaming.

The softening point (measured by drying a surfactant) measured according to JIS K7206 is preferably 30 ° C. or higher, in order to improve the corona treatment blocking resistance. However, when applying the coating liquid, in order to lower the surface tension of the coating liquid so as not to cause the coating omission, a surfactant (Y) other than the above is added at 10% by weight.
They may be used in combination within a range not exceeding (per total solids).

The surfactant (X) is preferably a nonionic surfactant, and particularly preferably a surfactant obtained by adding (poly) ethylene oxide to an alkyl alcohol, an alkylphenyl alcohol, a higher fatty acid, or the like.

As surfactants, as polyoxyethylene alkylphenyl ether compounds, trade names manufactured by NOF Corporation, "Nonion NS-230",
S-240 "," HS-220 "," HS-24 "
0 ", a product name of Sanyo Chemical Co., Ltd.," Nonipol 20
0 "," Nonipol 400 "," Nonipol 500 ",
"Octapol 400"; trade name, manufactured by NOF Corporation, "Nonion E-230", "K-220", "K-230" as polyoxyethylene alkyl ether-based compound; Examples of the ethylene ester-based compound include “Nonion S-15.4” and “S-40” manufactured by NOF Corporation.

The laminated film of the present invention, as described above,
On the surface of the coating layer B which is not in contact with the base layer A, coarse projections having a height of 4 nm or more calculated from a surface roughness profile obtained by a non-contact three-dimensional roughness meter are preferably 20.
It is present at a density of 0 / mm ² or less.

When the density of the coarse projections exceeds 200 / mm ² , the head itself becomes a cause of dropout, and when the coarse projections are caused by poor dispersion of the inert fine particles A, the head tends to cause uneven wear. It is not preferable because the electromagnetic conversion characteristics are also deteriorated.

In order to enhance the dispersibility of the inert fine particles A in the thermoplastic resin layer A, for example, when a polyester is used as the thermoplastic resin A, the timing of charging the slurry as a glycol slurry during the polymerization of the polyester is optimized. It is preferable to use a method of optimizing the feeding rate of the glycol slurry, or a method of performing high-precision filtration before extruding a molten polymer from an extrusion die during film formation. In this high-precision filtration, it is preferable that the average opening of the filter, particularly the sintered metal fiber filter, be 50 times or more, more preferably 80 times or more the average particle size of the inert fine particles A. In particular, it is preferable to combine the optimization of the particle addition method with the optimization of the average aperture during high-precision filtration.

The laminated film of the present invention preferably has the thin film layer C on the other surface of the base layer A, that is, on the surface which is not in contact with the coating layer B.

The thin film layer C preferably contains inert fine particles. Further, the thin film layer C can be a coating layer or a thermoplastic resin layer formed by co-extrusion.

When the thin film layer C is the coating layer C, the coating layer C
Can be composed of a binder resin and inert fine particles C, and can further contain a surfactant. As the binder resin, the inert fine particles C and the surfactant, the same ones as described for the coating layer B can be used. The inert fine particles C preferably have an average particle size of 0.01 to 0.1 μm, more preferably 0.02 to 0.08 μm, and particularly preferably 0.02 to 0.08 μm.
〜0.06 μm is used. The amount of the inert fine particles C is preferably 0.5 to 30% by weight, more preferably 1 to 20% by weight, and particularly preferably 2 to 10% by weight. In this case, as the surfactant, the surfactant (X) can be used alone or in combination. Therefore, the composition of the thin film layer C is
Can be the same composition as

Further, the thin film layer C is made of a thermoplastic resin layer containing inert fine particles C, and may be formed by co-extrusion with the base layer A. At this time, the following formula is preferably set between the thickness of the thin film layer C and the average particle size of the inert fine particles C.

[0056]

## EQU3 ## 0.001 ≦ (dc) ³ × Cc × tc ≦ 100
Here, dc (μm) is the average particle size of the inert fine particles C, Cc (% by weight) is the content of the inert fine particles C,
Further, tc (nm) is the thickness of the thin film layer C. To be satisfied.

When the thin film layer C is a coating layer, the above relationship is preferably

[0058]

## EQU4 ## 0.001 ≦ (dc) ³ × Cc × tc ≦ 0.1 In the case of a co-extruded layer, the above relation is preferably

[0059]

## EQU5 ## 0.1 ≦ (dc) ³ × Cc × tc ≦ 100.

In this case, the thin film layer C formed by co-extrusion contains inert fine particles C. The inert fine particles C have the following average particle size and are contained in the following amounts.

The average particle size d _C of the inert fine particles _C is 0.1 to
1 μm, further 0.15 to 0.8 μm, especially 0.2 to
It is preferably 0.7 μm. The content of the inert fine particles C having the average particle diameter d _C is 0.0001 to 1% by weight, and more preferably 0.001 to 1% by weight based on the thin film layer C.
It is preferably 0.5% by weight, particularly preferably 0.005 to 0.1% by weight.

[0062] inert fine particles C having an average particle diameter d _C
Examples thereof include (1) heat-resistant polymer particles (for example, particles made of crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, crosslinked polyester, etc.) (2) metal oxides (for example, aluminum trioxide, titanium dioxide,
Silicon dioxide, magnesium oxide, zinc oxide, zirconium oxide, etc.), (3) metal carbonates (eg, magnesium carbonate, calcium carbonate, etc.), (4) metal sulfates (eg, calcium sulfate, barium sulfate, etc.), (5)
Preferred are carbon (eg, carbon black, graphite, diamond, etc.) and (6) clay minerals (eg, kaolin, clay, bentonite, etc.).
Among these, particularly, crosslinked silicone resin particles, crosslinked polystyrene particles, melamine-formaldehyde resin particles,
Polyamideimide resin particles, aluminum trioxide (alumina), titanium dioxide, silicon dioxide, zirconium oxide, synthetic calcium carbonate, barium sulfate, diamond, and kaolin are preferred, and particularly, crosslinked silicone resin particles, crosslinked polystyrene resin particles, alumina, titanium dioxide , Silicon dioxide and calcium carbonate are preferred.

When the inert fine particles are composed of two or more kinds of particles, as the second and third particles having an average particle diameter smaller than the average particle diameter d _C of the inert fine particles C, for example, colloidal silica, Fine particles such as alumina having crystal forms such as α, γ, δ, and θ can be preferably used.
Further, among the particle types exemplified as the inert fine particles C having the average particle size d _C , fine particles having a small average particle size can be used.

The average particle size of the fine particles is 5 to 400 n.
m, even 10-300 nm, especially 30-250 nm
And the average particle diameter d _C is preferably at least 50 nm, more preferably at least 100 nm, especially at least 150 nm. The content of the second and third particles (fine particles) is 0.005 to 1% by weight, more preferably 0.01 to 0.7% by weight, particularly 0.05 to 0.5% by weight with respect to the thin film layer C. % By weight.

The thermoplastic resin C forming the thin film layer C may be the same as or different from the thermoplastic resin A forming the base layer A. Preferably they are the same. In particular, the base layer A
And the thin film layer C is preferably made of polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate. As these polyesters, o-
It is preferred that the solution in chlorophenol has an intrinsic viscosity of about 0.4 to 0.9 measured at 35 ° C.

The laminated film of the present invention has an air bleeding index (“air leak index” measured using a Beck smoothness tester, manufactured by Toyo Seiki Co., Ltd.) due to the presence of the thin film layer C.
It is preferable to show 1 to 15 m / hr.

The laminated film of the present invention has the above-mentioned thin film layer C and exhibits an air bleeding index in the above range, so that the film can be improved in handleability and winding property without impairing the electromagnetic conversion characteristics. Achieved.

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 of the thin film layer C is preferably 以下 or less, more preferably １ ／ or less, particularly preferably ４ or less of the total thickness of the laminated film. The coating layer B has a thickness of 1 to 100 nm, and more preferably 2 to 5 nm.
nm, particularly preferably 3 to 10 nm, more preferably 3 to 8 nm.

The laminated film of the present invention can be obtained according to a conventionally known method or a method accumulated in the art. The base layer A and the thin film layer C
Is preferably manufactured by a co-extrusion method, and the coating layer B is preferably formed by a coating method.

For example, in the case of a biaxially oriented polyester film, the above-mentioned inert fine particles A are finely dispersed and contained in the extrusion die or before the die (generally, the former is called a multi-manifold system, and the latter is called a feed block system). After the polyester A and the fine particles of the inert fine particles C are finely dispersed and further filtered with high precision, the polyester C is laminated and composited in a molten state to form a laminated structure having the above-described preferred thickness ratio. Melting point Tm ° C ~ (T
m + 70) After co-extruding into a film at a temperature of
It is quenched and solidified by a cooling roll at ~ 90 ° C to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is uniaxially (longitudinal or transverse) (Tg-1) according to a conventional method.
0) to (Tg + 70) ° C. (where Tg: glass transition temperature of the polyester) at a magnification of 2.5 to 8.0 times, and preferably at a magnification of 3.0 to 7.5 times, Next, at a temperature of Tg to (Tg + 70) ° C. and a magnification of 2.5 to 8.0 times in a direction perpendicular to the above direction, preferably 3.0 to 8.0.
Stretch at 7.5 times magnification. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. That is, stretching in two, three, four, or multiple stages may be performed. The total draw ratio is usually 9 times or more, preferably 12 to 35 times, more preferably 15 to 35 times, as the area draw ratio.
It is 30 times. Subsequently, the biaxially oriented film is heated at a temperature of (Tg + 70) to (Tm−10) ° C., for example, 1 ° C.
Excellent dimensional stability is provided by heat set crystallization at 80-250 ° C. The heat setting time is 1 to 60.
Seconds are preferred.

In the above method, a coating liquid containing the above-mentioned inert fine particles, a binder resin and a surfactant, preferably an aqueous coating liquid, is applied. The coating is preferably performed on the surface of the polyester layer A before the final stretching treatment, and after the coating, 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 application method is not particularly limited, and examples thereof include a roll coating method and a die coating method.

The solid content of the above-mentioned coating solution, especially the aqueous coating solution,
0.2 to 8% by weight, more preferably 0.3 to 6% by weight, in particular 0.
It is preferably 5 to 4% by weight. The coating liquid (preferably an aqueous coating liquid) contains other components, for example, other surfactants, stabilizers, dispersants, UV absorbers, thickeners, and the like, as long as the effects of the present invention are not impaired. Can be added.

The above example is suitable when both the thermoplastic resin A and the thermoplastic resin of the thin film layer C are polyethylene-2,6-naphthalenedicarboxylate or polyethylene terephthalate. The same applies when only C is polyethylene-2,6-naphthalenedicarboxylate or polyethylene terephthalate.

In the production of the laminated film, additives other than the above-mentioned inert particles may be added to the thermoplastic resin, if desired.
For example, a stabilizer, a colorant, a specific resistance modifier for the molten polymer, and the like can be added and contained.

In the present invention, in order to improve various functions 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 must be increased in the vertical and horizontal directions. 450kg / mm
² or more and 600 kg / mm ² or more, and further 480
kg / mm ² or more and 680 kg / mm ² , especially 55
0 kg / mm ² or more and 800 kg / mm ² or more, especially 550 kg / mm ² or more and 1,000 kg / mm
^It is preferably at least ² . The crystallinity of the polyethylene terephthalate layer is 30 to 50%,
The crystallinity of the 2,6-naphthalenedicarboxylate layer is desirably 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.

According to the present invention, a magnetic recording medium comprising the laminated film of the present invention as a base film, that is, a magnetic recording medium comprising the laminated film of the present invention and a magnetic layer present on the coating layer B of the laminated film Is provided as well.

An embodiment for producing a magnetic recording medium from the laminated film of the present invention is as follows.

The laminated film of the present invention is prepared by coating the surface of the coating layer B with iron, cobalt, chromium, or an alloy or oxide containing these as a main component by a method such as vacuum deposition, sputtering, or ion plating. And a protective layer such as diamond-like carbon (DLC) and a fluorinated carboxylic acid-based lubricating layer are sequentially provided on the surface of the ferromagnetic metal thin film layer, if necessary, and if necessary. By providing a back coat layer on the surface on the side of the thin film layer C by a known method, the output in the short wavelength region, the electromagnetic conversion characteristics such as S / N and C / N are particularly excellent, and the dropout and the error rate are low. It can be a vapor deposition type magnetic recording medium for density recording. 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 B
Iron or iron-like fine magnetic powder containing iron as a main component (metal powder) is uniformly dispersed in a binder such as polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, and the magnetic layer thickness is 1 μm or less, Preferably, the coating is performed so as to have a thickness of 0.1 to 1 μm, and if necessary, a back coat layer is provided on the surface on the side of the thin film layer C by a known method. / N, etc., and a metal-coated 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 as an underlayer of the metal powder-containing magnetic layer is dispersed in the same organic binder as the magnetic layer on the base layer A,
It can also be painted. 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, and D
It is extremely useful as a magnetic tape medium for DSIV, digital β cam, D2, D3, SX, etc.

The laminated film of the present invention further comprises a coating layer B
Fine magnetic powder of needles, such as iron oxide or chromium oxide, or fine magnetic powder, such as barium ferrite, is uniformly dispersed in a binder such as polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, The coating is performed so that the layer thickness is 1 μm or less, preferably 0.1 to 1 μm, and if necessary, a back coat layer is provided on the surface on the side of the thin film layer C by a known method, so that output in a short wavelength region is particularly high. , S / N, C / N, etc., and an oxide-coated magnetic recording medium for high-density recording with low dropout and low error rate. If necessary, a non-magnetic layer containing fine titanium oxide particles or the like is dispersed and coated in the same organic binder as the magnetic layer on the layer C as an underlayer of the magnetic layer containing the magnetic powder. 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 W-VHS is an analog HDTV signal recording VTR, and the DVC is a digital HTV.
The film of the present invention is applicable to DTV signal recording, and can be said to be a very useful base film for these HDTV-compatible VTR magnetic recording media.

[0082]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. In the Examples and Comparative Examples, “parts” and “%” are based on weight unless otherwise specified, and the physical property values and properties in the present invention are measured and defined by the following methods, respectively, and are defined. is there.

(1) Intrinsic viscosity It is determined from the value measured at 35 ° C. in an orthochlorophenol solution.

(2) Average particle size I of particles (average particle size: 0.1
06μm or more) Product name “CP-50 type Centrifugal Particle Size Analyzer (Ce) manufactured by Shimadzu Corporation
ntrifugal Particle Size A
(Analyser) ". From the integrated curve of the particles having 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,
See pages 242-247).

(3) Average particle size II of particles (average particle size: 0.
The particles having an average particle diameter of less than 0.06 μm forming small projections are:
It is measured using a light scattering method. That is, Nicomp Instrument Inc.
nts Inc. ) Brand name "NICOMP MOD
EL 270SUBMICRON PARTICLE
The particle is represented by the "equivalent spherical diameter" of the particle at a point of 50% by weight of all the particles determined by "SIZER".

(4) Thickness of thermoplastic resin layers A and C and total thickness The thickness of the entire film is measured at random at 10 points with a micrometer, and the average value is used. The thicknesses of the layers A and C are determined by measuring the thickness of the layer on the thin side by the method described below, and the thickness of the layer on the thick side is obtained by subtracting the thickness of the coating layer and the thickness of the thin side from the entire thickness. That is, using a secondary ion mass spectrometer (SIMS), a metal element (M ⁺ ) originating from the highest concentration of particles in a film having a depth of 5,000 nm from the surface layer excluding the coating layer. The concentration ratio (M ⁺ / C ⁺ ) of the carbon element (C ⁺ ) to the polyester is defined as the particle concentration, and the analysis in the thickness direction is performed from the surface to a depth of 5,000 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 is a case where the particle concentration once reaches a stable value 1 and then increases to a stable value 2 or a case where the particle concentration monotonously decreases. Based on this distribution curve, in the former case,
(Stable value 1 + Stable value 2) / 2, and in the latter case, the particle concentration is 1/1 / Stable value 1.
A depth of 2 (this depth is deeper than the depth that gives a stable value of 1) is defined as the layer thickness of the layer.

The measurement conditions are as follows. Measuring device Secondary ion mass spectrometer (SIMS): PERKIN ELMER INC.
Measuring conditions: Primary ion species: O ₂ + Primary ion accelerating 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: 0.5 KV-3.0 A When the particles most contained in the range of 5,000 nm from the surface layer are organic polymer particles other than the silicone resin, it is difficult to measure by SIMS. A density distribution curve similar to the above is measured by -IR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectric spectroscopy) or the like depending on the particles, and the layer thickness is determined.

(5) Density of protrusions on the surface of the coating layer B due to the inert fine particles B (measured at 35,000 times) Measurement of the protrusion density on the surface of the film is performed by a scanning electron microscope. That is, 25 photographs of the surface of the coating layer B of the laminated film were taken at random at a magnification of 35,000, the frequency of surface projections was counted, and the average value was converted into the number of projections per 1 mm ^2. Is the projection density of the inert fine particles B on the surface of the coating layer B.

(6) Projection density of inert fine particles A on the surface of coating layer B (measured at 5,000 times) The measurement of the projection density on the film surface is performed by a scanning electron microscope. That is, 25 photographs of the surface of the coating layer B of the laminated film were taken at random at a magnification of 5,000 times, the frequency of surface protrusions was counted, and the average value was converted into the number of protrusions per 1 mm ^2. Is the projection density of the inert fine particles A on the surface of the coating layer B.

(7) Center surface average roughness Non-contact three-dimensional roughness meter manufactured by WRa WYKO Co., Ltd., trade name “T
OPO-3D ”, measurement magnification 40 times, measurement area 2
The measurement is performed under the conditions of 42 μm × 239 μm (0.058 mm ² ) to obtain a surface roughness profile (original data). WRa uses the value calculated and output by the following equation by the surface analysis using the built-in roughness meter software.

[0091]

(Equation 6)

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

(8) Number of Coarse Protrusions Using the surface roughness profile (original data) obtained in (7) above, 15 consecutive divisions of this profile in the measurement direction (for example, j = 1 to 15) ) And an area (15 × 15) formed by 15 continuous divisions (for example, k = 1 to 15) in a direction orthogonal to the above (orthogonal direction).
The average value of the heights in the divided area is calculated, and (j, k)
== (1,1) average height. Next, when one division position in the measurement direction or the orthogonal direction is moved by one (for example, j = 2 to 16, k = 1 to 15, or j = 1 to 15,
k = 2 to 16) An average value of heights in an area of 15 × 15 divisions is obtained, and (j, k) = (2, 1) or (1, 2)
And the average height. Further, by moving the division position one by one, for example, the average value of the heights in the 15 × 15 divisional area of j = p to p + 14 and k = q to q + 14 is calculated, and (j, k) = ( The average height of (p, q) is obtained, and the calculation of the average height is repeated up to 256 divisions in the measurement direction and 256 divisions in the orthogonal direction. The surface roughness profile constituted by these average heights corresponds to the undulation of the film surface.

The profile (reconstructed data) of the film surface is reconstructed by subtracting the undulating surface component from the original data. The reconstructed data is analyzed by a built-in roughness meter software, and protrusions having a height of 4 nm or more are counted as coarse protrusions. This measurement is performed 10 times at different measurement points, and the average value is counted per 1 mm ^2. The value converted to is the number of coarse projections.

(9) Young's modulus Using a tensile tester manufactured by Toyo Baldwin Co., Ltd., trade name “Tensilon”, in a room adjusted to a temperature of 20 ° C. and a humidity of 50%, a length of 300 mm and a width of 12.7.
mm sample film is pulled at a strain rate of 10% / min and is calculated by the following equation using the first straight line portion of the tensile stress-strain curve.

[0096]

Where E is the 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 strain difference between points.

(10) Air bleeding property First, using a Beck smoothness tester manufactured by Toyo Seiki Co., Ltd., 40 films were superimposed, and the remaining 39 films were removed except for the one that came to the top of the sample table. Drill a hole with a diameter of 5 mmφ and set it on the sample stage. At this time, the center of the hole is set at the center of the sample stage. In this state, 0.5kg
/ Cm ² , and set the vacuum attainment to 550 mmHg. After reaching 550 mmHg, air flows between the films in order to return to normal pressure. At this time, the degree of vacuum (mmHg) falling every 30 seconds during one hour was measured, and the slope of the straight line when the degree of vacuum with respect to the measurement time (hr) was linearly approximated (= mmHg /
hr) is the air leak index G.

(11) Number of Micro Protrusions The surface of the coating layer B, on which aluminum was deposited to a thickness of 0.5 μm, was subjected to differential interference using an optical microscope manufactured by NIKON CORP., Trade name “OPTIPHOT”. Observation at 400 times magnification by the method
count the protrusions of 5 μm in the mx width direction and count 1 mm
The number of microprojections is converted to the number of ^two .

(12) Corona treatment blocking peeling force: 100 mm in the longitudinal direction of the roll film, 2 mm in the width direction.
The sample is sampled into a rectangle of 00 mm, and the base layer A is subjected to corona treatment in an environment of room temperature 25 ± 5 ° C. and humidity 50 ± 5%.

The processing was performed by Kasuga Electric Co., Ltd., trade name "C
The processing is performed under the following conditions using a "G-102" type high frequency power supply. Current: 4.5 A Distance between electrodes: 1.0 mm Processing time: Processing is performed by passing between electrodes at a speed of 1.2 m / min.

The treated film was immediately brought into contact with the surface opposite to the base layer A, aged at a pressure of 100 kg / cm ² at room temperature of 60 ° C. and humidity of 80% for 17 hours, and then subjected to a tensile tester ( "Tensilon") width 10
The peel force per 0 mm is determined.

(13) AFM Surface Roughness Digital Instrument Co., Ltd.
l Instruments Inc. ) Atomic force microscope, trade name "Nano Scope IIIAFM"
Is used, and the root mean square roughness calculated under the following conditions is measured under the following conditions. Deep needle: single bond silicon sensor Scanning mode: tapping mode Scanning range: 10 μm × 10 μm Pixels: 256 × 256 data points Scanning speed: 2.0 Hz Measurement environment: room temperature, in air Numerical values are displayed as the average value measured five times .

(14) Production of Magnetic Tape and Characteristic Evaluation A 100% cobalt ferromagnetic thin film having a thickness of 0.2 μm was 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 fluorine-containing carboxylic acid-based lubricating layer are sequentially provided on the surface, and a back coat layer is further formed on the surface of the thermoplastic resin C by a known method. Provide. Then, it is slit into an 8 mm width and loaded on a commercially available 8 mm video cassette. Next, the properties of the tape are measured using the following commercially available equipment.

Equipment used: 8 mm video tape recorder: Sony Corporation, trade name "EDV-6000" C / N measurement: Shibasoku Co., Ltd., noise meter C / N measurement Recording wavelength 0.5 μm (frequency about 7.4 MHz) ) Is recorded, the ratio of 6.4 MHz to 7.4 MHz of the reproduced signal is defined as the C / N of the tape, and the C / N of the commercially available 8 mm video tape is defined as 0 dB. Judgment Criteria Basic A: +5 dB or more compared to a commercially available 8 mm tape. ：: +1 dB or more and less than +5 dB compared to a commercially available 8 mm tape. X: Less than +1 dB compared to a commercially available 8 mm tape.

Dropout Using a dropout counter manufactured by Shibasoku Co., Ltd., a dropout of 3 μsec / 10 dB or more is set to 1
Measure for 0 minutes and convert to the number per minute.

The judgment is made based on the following criteria. ：: 10 drops / min or less. X: Dropout of 11 or more / min.

Running Durability A video signal of 4.2 MHz was recorded on the above-mentioned vapor-deposited tape, and a tape running speed of 41 m / min and a rewind speed of 41 m / min were run at a temperature of 25 ° C. and a humidity of 50% RH. And the output fluctuation after a total of 200 repetitions is examined.
Judgment is made based on the output fluctuation based on the following criteria. ：: output fluctuation after 200 repetitions is 0 dB to -0.3
dB. ：: Output fluctuation after repeating 200 times is -0.3 dB to-
0.6 dB. X: The output fluctuation after repeating 200 times is -0.6 dB or less.

Example 1 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, titanium trimellitate as a polymerization catalyst, phosphorous acid as a stabilizer, and a lubricant as shown in Table 3 Active fine particles were added and polymerized by a conventional method to obtain polyethylene terephthalate (PET) (resin A and resin C, respectively) for layer A and layer C having an intrinsic viscosity of 0.60.

The resin A and the resin C were dried at 170 ° C. for 3 hours, respectively, and then supplied to two extruders.
After melting at 0 to 300 ° C. and high-precision filtration with a steel wire filter having an average opening of 11 μm, the resin layer C is laminated on one side of the resin layer A using a multi-manifold type coextrusion die, and quenched. An unstretched laminated film having a thickness of 89 μm was obtained.

The obtained unstretched film was preheated, and further between a low-speed and high-speed roll at a film temperature of 100 ° C.
The film was stretched three times, quenched, and then an aqueous coating solution having a composition shown in Table 2 (total solid concentration: 1.0% by weight) was applied to the layer A side of the longitudinally stretched film by a kiss coat method, and then applied to a stenter. It was supplied and stretched 4.2 times in the transverse direction at 110 ° C.
The obtained biaxially stretched film was heat-set with hot air at 220 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 6.4 μm. The thicknesses of the layers A and C were adjusted by the discharge amounts of the two extruders. The Young's modulus of this film is 500 kg / mm ^{2 in} the vertical direction and 700 kg / mm in the horizontal direction.
^{Was 2} .

Table 1 shows the surface characteristics of this laminated film and the characteristics of a ferromagnetic thin film-deposited magnetic tape using this film.

Example 2 A laminated film was obtained in the same manner as in Example 1, except that polyethylene terephthalate having an intrinsic viscosity of 0.60 and containing no inert fine particles was used as the thermoplastic resin for Layer A. Table 1 shows the properties and the like of the obtained film.

Example 3 An unstretched film having a thickness of 89 μm was obtained in the same manner as in Example 1 from polyethylene terephthalate having the same intrinsic viscosity of 0.60 and containing no inert fine particles.

The obtained unstretched film was preheated, and further between a low-speed and high-speed roll at a film temperature of 100 ° C.
The film was stretched three times, quenched, and then an aqueous coating solution (B1) having the composition shown in Tables 2 and 3 was applied to both sides of the longitudinally stretched film by a kiss coat method.
The film was stretched 4.2 times in the transverse direction at ℃. The obtained biaxially stretched film is heat-set with hot air at 220 ° C. for 4 seconds to have a thickness of 6.
A 4 μm laminated biaxially oriented polyester film was obtained. The thicknesses of the layers A and C were adjusted by the discharge amounts of the two extruders. The Young's modulus of this film is 500k in the vertical direction.
g / mm ² and 700 kg / mm ² in the lateral direction.

Table 1 shows the surface characteristics of this laminated film and the characteristics of a ferromagnetic thin film-deposited magnetic tape using this film.

Example 4 The procedure of Example 3 was repeated, except that the aqueous paint (B1) and the aqueous paint (B4) having the compositions shown in Tables 2 and 3 were applied between the obtained longitudinally stretched films. It carried out similarly to Example 3. Table 1 shows the results.

Example 5 A 5.6 μm-thick layer composed of polyethylene terephthalate having an intrinsic viscosity of 0.6, in which the base layer does not contain inert fine particles, and 0.1% of silicone particles having an average particle diameter of 0.6 μm. Θ- with an average particle size of 0.06 μm
Example 4 is the same as Example 4 except that the film is a laminated film composed of a 0.8 μm thick layer made of polyethylene terephthalate containing 0.3% of alumina particles. However, the coating layer B was present on the layer containing no inert fine particles, and the coating layer C was present on the layer containing the inert fine particles. Table 4 shows the results.

Comparative Example 2 After supplying the thermoplastic resin A to the extruder, the lamination was performed in the same manner as in Example 1 except that the aperture of the steel wire filter used for high-precision filtration was changed to 4.8 μm. A film was obtained. Table 11 shows the characteristics of the laminated film and the ferromagnetic thin film-deposited tape using this film. As is evident from Table 11, this film has a large number of surface roughness projections, so that the film has many dropouts when formed into a tape, and the running durability is lowered due to uneven wear of the head.

[Examples 6 and 7] The same procedures as in Example 1 were carried out except that the added inert fine particles and the thickness of the layers A and C were as shown in Table 6, and the composition of the coating layer B was as shown in Table 5. A similar laminated film was obtained. Properties of the resulting film, and
Table 4 shows the characteristics of the ferromagnetic thin film deposited magnetic tape using this film.

Examples 8 to 10 Instead of dimethyl terephthalate, the same moles of dimethyl 2,6-naphthalenedicarboxylate were used.
The polyethylene-2,6-naphthalate (P) for layers A and C was prepared in the same manner as in Example 1 except that the fine particles shown in FIG.
EN) (Resin A, Resin C).

After drying Resin A and Resin C at 170 ° C. for 6 hours, 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 reduced between low and high speed rolls.
At 35 ° C., 3.3 times in Example 8 and 3.6 times in Example 9
In Example 10, the film was stretched to 4.0 times, quenched, and then an aqueous coating solution of the coating film B shown in Tables 5 and 9 was applied in the same manner as in Example 1, and then supplied to a stenter. In the lateral direction, 6.4 times in Example 8, 5.6 times in Example 9,
In Example 10, the film was stretched 5.2 times. The obtained biaxially stretched film was heat-set with hot air at 200 ° C. for 4 seconds to obtain a laminated film. Tables 4 and 8 show the properties of the obtained film and the properties of the ferromagnetic thin film-deposited magnetic tape using this film.

Comparative Example 1 The same procedures as in Example 1 were carried out except that the added inert fine particles and the layer thickness of the layers A and C were as shown in Table 13 and the composition of the coating layer B was as shown in Table 12. Similarly, a laminated film was obtained. Table 11 shows the properties of the obtained film and the properties of a ferromagnetic thin-layer deposited magnetic tape using this film.

Examples 11 to 14 and Comparative Examples 3 to 5 A laminated film was obtained in the same manner as in Example 1 except that the composition of the coating layer B was as shown in Tables 9, 12 and 15. Tables 8, 11 and 14 show the properties of the obtained film and the properties of the ferromagnetic thin-layer deposited magnetic tape using this film.

[0125]

[Table 1]

[0126]

[Table 2]

[0127]

[Table 3]

[0128]

[Table 4]

[0129]

[Table 5]

[0130]

[Table 6]

[0131]

[Table 7]

[0132]

[Table 8]

[0133]

[Table 9]

[0134]

[Table 10]

[0135]

[Table 11]

[0136]

[Table 12]

[0137]

[Table 13]

[0138]

[Table 14]

[0139]

[Table 15]

[0140]

[Table 16]

As is evident from Tables 1, 4, 8, 11 and 14, the laminated films of the examples show excellent electromagnetic conversion characteristics, and have not only a small number of fine projections causing dropout, but also a high resistance to dropout. Good corona blocking peeling force. Furthermore, in the laminated film of the example, since the inert fine particles added to the layer A corresponding to the magnetic layer surface side are appropriate and the number of coarse particles is small, the dropout due to these is small and the running durability is excellent. ing. On the other hand, the comparative film cannot satisfy these characteristics at the same time.

[0142]

According to the present invention, a magnetic recording medium having good blocking resistance against corona treatment, excellent running durability and electromagnetic conversion characteristics even when used as a vapor-deposited metal thin film type magnetic recording medium, and extremely low dropout. A laminated film capable of producing a medium can be provided.

Claims (17)

[Claims] 1. A laminated film comprising a base layer A made of a thermoplastic resin A and a coating layer B present on one surface of the base layer A, wherein the coating layer B is a binder resin, A laminated film comprising fine particles and a surfactant and having a corona-treated blocking release of 15 g / 10 cm or less. 2. The laminated film according to claim 1, wherein the thermoplastic resin A forming the base layer A does not substantially contain inert fine particles. 3. The thermoplastic resin A forming the base layer A has an average particle size of 30 to 400 nm and a volume shape factor of 0.1 to π /.
The laminated film according to claim 1, which contains the inert fine particles A of No. 6. 4. A density of 50,000 to 100,000 particles / mm ² on the surface of the coating layer B on the side not contacting the base layer A due to the inert fine particles A. The laminated film according to claim 3, which is contained in the thermoplastic resin A in such a proportion as to produce protrusions. 5. On the surface of the coating layer B which is not in contact with the base layer A, projections originating from inert fine particles contained in the coating layer B are present at a density of 1 to 40 / μm ^2. Claim 1
3. The laminated film according to item 1. 6. The inert fine particles in the coating layer B have an average particle diameter in the range of 10 to 50 nm, and the content thereof is 0.5 to 30% by weight based on the solid content of the coating layer B. The laminated film according to claim 1. 7. On the surface of the coating layer B which is not in contact with the base layer A, the density of coarse projections having a height of 4 nm or more calculated from a surface roughness profile obtained by a non-contact three-dimensional roughness meter is used. ^2. The laminated film according to claim 1, wherein the number is 200 / mm ² or less. 8. The laminated film according to claim 1, wherein the surfactant is a nonionic surfactant. 9. The laminated film according to claim 1, wherein the binder resin of the coating layer B is an aqueous polyester resin. 10. The laminated film according to claim 1, further comprising a thin film layer C on a surface of the base layer A that is not in contact with the coating layer B. 11. The thin film layer C is a coating layer comprising a binder resin, inert fine particles and a surfactant.
3. The laminated film according to item 1. 12. The laminated film according to claim 10, wherein the thin film layer C has the same composition as the coating layer B. 13. The laminated film according to claim 10, wherein the thin film layer C comprises a thermoplastic resin layer containing inert fine particles C, and is formed by co-extrusion with the base layer A. 14. The thin film layer C has the following formula: 0.001 ≦ (dc) ³ × Cc × tc ≦ 100 where dc (μm) is the average particle size of the inert fine particles C, and Cc ( % By weight) is the content of inert fine particles C,
Further, tc (nm) is the thickness of the thin film layer C. The laminated film according to claim 13, which satisfies the following. 15. The laminated film has an air bleeding index of 1 to 15.
The laminated film according to claim 10 or 13, which shows mmHg / hr. 16. A magnetic recording medium comprising the laminated film according to claim 1 and a magnetic layer present on the coating layer B of the laminated film. 17. The magnetic recording medium according to claim 16, which is for Hi8 for recording an analog signal, a digital video cassette recorder for recording a digital signal or 8 mm data, and for DDSIV.