JPH09314760A - Laminate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a biaxially oriented thermoplastic laminate film having a good winding property and useful as a base film of a high density electromagnetic recording medium. SOLUTION: The laminate film has at least a three layer structure having a covered layer, wherein a covering layer C having an average particle diameter of 10-50nm and containing a quantity of inactive particles A of a volume configuration coefficient of 0.1-π/6 to be 2.0-50.0pieces/μm<2> in its superficial projection frequency and its projection height being 30%-200% of a particle diameter of particles is formed on one surface of a thermoplastic resin layer A containing a quantity of inactive particles A of an average particle diameter of 40-400nm, and volume configuration coefficient frequency of 0.1-π/6 to be 5000-50000pieces/ mm<2> in its superficial projection frequency, and on the other surface, a thermoplastic resin layer B is laminated which contains inactive particles B and a coarser surface than that of the thermoplastic resin layer C, and further formed on the surface of the covering layer C is a waviness projection of a coarse profile height of 2-85nm and an average width of 20-500μm in the direction of 0±10 degue in the longitudinal direction.

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 is excellent in winding property, defect-free property, slipperiness and handling property, and is excellent in electromagnetic conversion characteristics, dropout, running property and durability. The present invention relates to a laminated film useful as a base film for high density magnetic recording media.

[0002]

2. Description of the Related Art In recent years, there have been remarkable progresses in increasing the density of magnetic recording. For example, a ferromagnetic metal thin film is formed on a non-magnetic support by a physical deposition method such as vacuum deposition or sputtering or a plating method. Development and practical application of thin-film magnetic recording media, thin-layer coating type magnetic recording media in which acicular magnetic powder such as metal powder or iron oxide powder is coated to 2 μm or less have been advanced.

As examples of the former, for example, Co vapor deposition tape (Japanese Patent Laid-Open No. 54-147010), Co-Cr
Perpendicular magnetic recording medium made of alloy (Japanese Patent Laid-Open No. 52-1347)
No. 06), and as an example of the latter, for example, high density magnetic recording using an ultrathin layer coating type 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 a magnetic powder in an organic polymer binder and coating on a non-magnetic support) have a low recording density and a long recording wavelength. While the thickness of the magnetic layer is as thick as about 2 μm or more, the metal thin film formed by thin film forming means such as vacuum deposition, sputtering or ion plating is very thin, not more than 0.2 μm, and extremely thin. In the case of a layer coating type medium, the non-magnetic underlayer
A coated magnetic layer having a thickness of 3 μm has been proposed and is very thin.

Therefore, in the above high-density magnetic recording medium, the surface state of the non-magnetic support has a great influence on the surface property of the magnetic recording layer, and particularly in the case of a metal thin film type magnetic recording medium. The surface state of the non-magnetic support is directly expressed as irregularities on the surface of the magnetic recording layer, which causes noise in the recording / reproducing signal. Therefore, it is desirable that the surface of the non-magnetic support be 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 Slip property deteriorates, a booking phenomenon occurs, the shape when rolled into a roll (roll formation) deteriorates, the product yield decreases, and eventually the manufacturing cost of the product increases. Therefore, from the viewpoint of manufacturing cost, it is desirable that the surface of the non-magnetic support (base film) be 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 handleability and film cost.

Further, in the case of a vapor-deposited metal thin film type magnetic recording medium, a serious problem in practical use is lack of running property of the metal thin film surface. In the case of a coating type magnetic recording medium prepared by mixing a magnetic powder in an organic polymer binder and coating the base film, a lubricant may be dispersed in the binder to improve the running property of the magnetic surface. However, in the case of a metal thin film type magnetic recording medium, such measures cannot be taken, and it is very difficult to maintain stable running properties, and especially running properties under high temperature and high humidity conditions are poor. Has the drawback of.

Therefore, in order to inexpensively supply a base film for a high-density recording medium of excellent quality, it is necessary to simultaneously satisfy the above contradictory properties.

As a specific method for this purpose, a method of applying a specific coating agent on the film surface to form a discontinuous film (Japanese Patent Publication No. 3-80410, JP-A 60-1808).
39, JP-A-60-180838, JP-A-60-180837, JP-A-56-16937, JP-A-58-68223), and a continuous film having fine irregularities. Forming method (Japanese Patent Laid-Open No. 5-194
772, JP-A-5-210833), a method of making the front and back different by a technique such as co-extrusion (JP-A-2).
No. 214-657, Japanese Patent Publication No. 7-80282), a method using + or a combination of + (Japanese Patent Laid-Open No. 3-73409), and the like are proposed.

[0011]

However, in the method for forming a discontinuous film or a continuous film having fine irregularities, the problems such as slip between films and film and blocking can be solved, but the base film Film formation, transport in film forming process, scratching, winding, and unwinding are not sufficient, and it is suitable for use as a base film for high-density and large-capacity magnetic recording media from the viewpoint of product yield and product cost. Has a problem. Further, the conventional coextrusion technology or the conventional technology of combining the coextrusion technology and the discontinuous coating or the continuous coating has the same problem. Further, the metal thin film type magnetic recording medium still has a problem of running property under high temperature and high humidity conditions.

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

[0013]

In order to achieve such an object, the present invention has the following constitution. Average particle size 10-5
Inert particles C having a size of 0 nm and a volume shape factor of 0.1 to π / 6 are contained in an amount such that the surface protrusion frequency is 2.0 to 50.0 particles / μm ² , and the protrusion height is the particle size of the particles. 30% or more of 2
The coating layer C having an average particle diameter of 40 to 400 n
m and a volume shape factor of 0.1 to π / 6 are provided on one surface of the thermoplastic resin layer A containing the amount of the inert particles A having a surface projection frequency of 5,000 to 50,000 particles / mm ^2. A laminated film having at least a three-layer structure in which a thermoplastic resin layer B containing inert particles and having a rougher surface than the thermoplastic resin layer C is laminated on the other surface of the thermoplastic resin layer A, which is a layer C Roughness profile measured in the direction of 0 ± 10 degrees with respect to the longitudinal direction on the surface of is 2 to 85 nm in height and 20 to 5 in average width.
4 to 2,500 waviness-shaped protrusions of 00 μm / mm ²
Laminated film having a frequency of.

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

Preferred aromatic polyesters are polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly-1,4.
Examples thereof include cyclohexylene dimethylene terephthalate and polyethylene 2,6 naphthalene dicarboxylate. Of these, polyethylene terephthalate and polyethylene 2,6 naphthalene dicarboxylate are particularly preferable.

These polyesters may be homopolyesters or copolyesters. In the case of copolyester, examples of the copolymerization component of polyethylene terephthalate and polyethylene 2,6 naphthalene dicarboxylate include diethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyethylene glycol, p-xylene. Glycol, diol component such as 1,4-cyclohexanedimethanol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (in the case of polyethylene 2,6 naphthalene dicarboxylate), 2,6- Naphthalene dicarboxylic acid (in the case of polyethylene terephthalate), dicarboxylic acid component such as 5-sodium sulfoisophthalic acid, p
Examples include oxycarboxylic acid components such as oxyethoxybenzoic acid. The amount of these copolymerization components is preferably 20 mol% or less, more preferably 10 mol% or less.

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

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

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

The coating layer C has an average particle size of 10 to 50 nm,
Preferably 12 to 45 nm, more preferably 15 to 45 nm
and the frequency of protrusions on the surface of the inactive particles C having a volume shape factor of 0.1 to π / 6 is 2.0 to 50.0 particles / μm ² ,
It is preferably 3.0 to 40.0 particles / μm ² , more preferably 4.0 to 30.0 particles / μm ² , and the projection height formed by the particles is smaller than the particle diameter of the particles C. It is necessary to be 30% or more and less than 200%, preferably 40% to 180%, and more preferably 50 to 160%.

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

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

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

[0024]

[Formula 2] F = V / R ³ (2)

Here, V represents the volume of the inert particles, and R represents the average particle size of the inert particles.

The material of the inert particles C is not particularly limited, but for example, a heat resistant polymer (crosslinked silicone resin,
Polystyrene, crosslinked styrene-divinylbenzene copolymer, polymethylmethacrylate, methylmethacrylate copolymer, crosslinked methylmethacrylate copolymer, polytetrafluoroethylene, polyvinylidenefluoride, polyacrylonitrile, benzoguanamine resin, etc.)
Preference is given to organic polymer particles consisting of silica, inorganic fine particles such as silica, alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black and barium sulfate.
Particularly preferred are crosslinked silicone resin particles, silica, and particles having a core-shell structure (core: crosslinked polystyrene, silica, etc., shell: methyl methacrylate, etc.).

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

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

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

The aqueous polyester resin has acid components such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, adipic acid,
Sebacic acid, dodecane ditrimellitic acid, succinic acid, 5
-Na sulfoisophthalic acid, 2-K sulfoterephthalic acid, trimellitic acid, trimesic acid, monopotassium trimellitic acid, polyvalent carboxylic acid such as p-hydroxybenzoic acid, and the glycol component is, for example, ethylene glycol, diethylene glycol, propylene. Glycol,
Polyester mainly composed of polyhydric hydroxy compounds such as 1,4-butazine diol, 1,6-hexane diol, 1,4-cyclohexane dimethanol, p-xylylene glycol, dimethylol propionic acid, and ethylene oxide adduct of bisphenol A A resin, a graft polymer or a block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or two polymers have a specific physical constitution (IPN,
Acrylic-modified polyester resin constituting the core shell) is included. As this water-based polyester resin, a type that dissolves in water, emulsifies, or is finely dispersed can be freely used, and in order to impart hydrophilicity, for example, a sulfonic acid group, a carboxylic acid group, a polyether unit, etc. are present in the molecule. It may be introduced.

The average thickness (t _C ) of the coating layer C is 1 to 500.
nm is preferable, and the average particle diameter of the inert particles C is d _C
It is preferable that the relation expressed by the following formula (3) is satisfied.

[0032]

## EQU3 ## 0.1 ≦ t _C / d _C ≦ 10 (3)

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

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

The flat thermoplastic resin layer A in the present invention has an average particle size of 40 to 400 nm, preferably 50 to 20.
0 nm, more preferably 60 to 120 nm, and the frequency of surface protrusions when the inert particles A having a volume shape factor of 0.1 to π / 6 is measured on the surface of the coating layer C is 5,000 to 50,000 / m
The content of m ² is preferably 7500 to 40,000 pieces / mm ² , and more preferably 1 to 30 thousand pieces / mm ² .

If the frequency of protrusions on this surface is less than 5,000 / mm ² , the friction of the magnetic layer with respect to the magnetic head is high, the repeated running durability of the magnetic layer is poor, and the transportability and scratch resistance in the film forming process are low. The sticking property is also bad and not preferable. On the other hand, if the frequency of the protrusions is larger than 50,000 / mm ^2, it is not preferable because the protrusions are more likely to come off and dropouts are increased.

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

Like the above-mentioned inert particles C, the above-mentioned inert particles A have a volume shape factor (F) defined by the equation (2) of 0.
It is necessary to satisfy 1 to π / 6, but 0.3 to π /
6 is preferable, and a substantially spherical or rugby ball-shaped elliptical sphere of 0.4 to π / 6 is more preferable. This is because F is smaller than 0.1 and, for example, acicular particles deteriorate the magnetic characteristics of the thin film magnetic layer. Further, as its material, crosslinked silicone resin, polystyrene, crosslinked styrene-divinylbenzene copolymer, polymethylmethacrylate, methylmethacrylate copolymer, methylmethacrylate copolymer crosslinked product, polytetrafluoroethylene, polyvinylidene fluoride, poly Organic polymer particles such as acrylonitrile and benzoguanamine resin, silica,
Any of inorganic fine particles such as alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black and barium sulfate may be used.

The thermoplastic resin layer C in the present invention further has a height of 2 to 85 in the roughness profile measured in the direction of 0 ± 10 degrees with respect to the longitudinal direction of the film on the surface thereof.
nm, preferably 2 to 50 nm, more preferably 2 to 2
5 nm, average width 20 to 500 μm, preferably 20 to
300 μm, more preferably 20 to 200 μm wavy protrusions 4 to 2500 / mm ² , preferably 10
~ 2000 / mm ² , more preferably 10-1000
It has surface characteristics that exist at a frequency of pcs / mm ² .

If the height of these wavy projections is less than 2 nm or the width exceeds 500 μm, they will be transported in the film forming process.
It is insufficient in terms of scratches on the film, winding shape of the product roll, blocking phenomenon between the film and film, and running property of the tape under high temperature and high humidity conditions when used for magnetic recording of metal thin film.

On the other hand, if the height of the wavy protrusion exceeds 85 nm, the electromagnetic conversion characteristics are impaired, and it is not suitable as a base film for high density magnetic recording. Further, if the average width of the wavy projections is less than 20 μm, the height of the waviness is in a region of 25 nm or less, which is insufficient in terms of transportability in the film forming process and running property of the tape.

The measuring direction of the waviness is 0 ± 10 ° with respect to the longitudinal direction of the film. This is a magnetic recording system to which a 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 head scans on the tape.

The waviness-like projections on the surface of the thermoplastic resin layer C are not restricted by the forming method thereof, but are formed on the layer A along with the stretching of the inactive particles B contained in the thermoplastic resin layer B. It is preferable to use a push-up action.

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 single particles or have different sizes.
The average particle size of a single particle or the largest particle of two or more particles is defined as d _B (μ
m) and the thickness of the layer A is t _A (μm), the following equation (1)

[0045]

Equation 4] _{4 ≦ t A / d B ≦} 40 (1)

It is preferable to satisfy the following. 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 wrinkles contained in the thermoplastic resin layer A. Since the height of the projections based on the inert particles is equal to or lower than the height of the projections, the projections due to the fine particles of the thermoplastic resin layer A, the long period undulation, and the thermoplastic resin layer B are not adversely affected. Due to the synergistic effect of the three rough surfaces, it is possible to solve all the problems of the conventional base film for high-density magnetic recording.

The thermoplastic resin layer A of the present invention has a surface roughness of 10 nm or less, more preferably 5 nm or less, particularly 2 nm or less, as measured on the surface of the coating layer C. In particular, it is preferably 1 nm or less. If the surface roughness exceeds 10 nm, the electromagnetic conversion characteristics deteriorate, which is not preferable.

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

[0050]

[Equation 5] Ra _B > Ra _C (4)

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

Ra _B is 1 nm or more than Ra _C , and 1.
It is preferably larger than 5 nm. The center surface average roughness Ra _B is 2 nm or more and less than 15 nm, and further 3
It is preferably 10 nm, particularly 3 to 7 nm.

The surface roughness Ra _B of the thermoplastic resin layer _B is 15
When the thickness is not less than nm, the height of the wavy protrusions on the surface of the coating layer C
It is difficult for the average width to satisfy the above requirements, and if it is less than 2 nm, handling properties such as transportability and tape running properties are insufficient, which is not preferable. Further, when Ra _B is Ra _A or less, handling property such as conveyance, scratches, winding, and unwinding in the film forming process of the base film is deteriorated due to the flatness, and the slip property between the film and the film is deteriorated. The deterioration causes a booking phenomenon, which deteriorates the shape when rolled into a roll (roll formation), deteriorates productivity, lowers the product yield, and eventually increases the manufacturing cost of the product, which is not preferable.

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

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

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

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

The laminated film composed of the thermoplastic resin layers A and B in the present invention can be manufactured by a method known in the art or accumulated in the art.
Among them, the coextrusion method is preferred. For example, in the case of a biaxially oriented polyester film, an extrusion die or a die before die (generally referred to as a multi-manifold type and a latter is referred to as a feed block type) is used as a flat layer polyester A containing the above-mentioned inert particles A and a polyester layer. The polyester B of the rough surface layer containing the active particles B is laminated and composited in a molten state to form a laminated structure having the above-mentioned suitable thickness ratio, and then formed into a film at a temperature of melting point Tm ° C to (Tm + 70) ° C from the die. After coextrusion, the mixture is cooled and solidified at 40 to 90 ° C. to obtain an unstretched laminated film. Then, the unstretched laminated film is uniaxially (longitudinally or laterally) at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester) according to a conventional method.
The film is stretched at a draw ratio of 5 to 8.0 times, preferably at a draw ratio of 3.0 to 7.5 times, and then stretched in a direction perpendicular to the above-mentioned direction by Tg.
Stretching is carried out at a temperature of (Tg + 70) ° C. at a draw ratio of 2.5 times to 8.0 times, preferably at a draw ratio 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 advisable to perform stretching in two steps, three steps, four steps, or multiple steps. The total draw ratio is usually 9 times or more, preferably 12 to 35 times, more preferably 1 as an area draw ratio.
5 to 26 times. Further subsequently, the biaxially oriented film is imparted with excellent dimensional stability by heat-fixing crystallization at a temperature of (Tg + 70) to (Tm-10) ° C, for example, 180 to 250 ° C. The heat setting time is 1 to 60
Seconds are preferred.

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

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

As described above, the coating layer C may be formed by the coating method, or a thermoplastic resin may be used in place of the binder resin and the layers A and B may be simultaneously formed by the coextrusion method. .

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 electric resistance modifier 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 achieve thinning, the Young's modulus of the laminated film is changed in the longitudinal direction and the transverse direction, respectively. 450 kg / mm ² or more, 600 kg / mm ² or more, and further 480 each
kg / mm ² or more, 680 kg / mm ² or more, especially 550 kg / mm ² or more, 800 kg / mm ² or more, especially 550 kg / mm ² or more, 1000 kg / m, respectively
It is preferably m ² or more. The polyethylene terephthalate layer preferably has a crystallinity of 30% to 50%, and the polyethylene 2,6 naphthalene dicarboxylate layer preferably has a crystallinity of 28% to 38%. If both are below the lower limit, the heat shrinkage ratio will be large, and if above the upper limit, the abrasion resistance of the film will be deteriorated, and white powder will easily be generated when sliding 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 them as a main component 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 according to the purpose, use, 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 a short wavelength region, electromagnetic conversion such as S / N, C / N, etc. It is possible to provide a vapor-deposited magnetic recording medium for high density recording, which has excellent characteristics and has a small dropout and error rate. This vapor-deposited magnetic recording medium is extremely useful as a Hi8 for analog signal recording, a digital video cassette recorder (DVC) for digital signal recording, a data 8 mm, and a tape medium for 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 vinyl 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. By coating so as to have a thickness of 1.0 μm and further providing a back coat layer on the surface of the thermoplastic resin layer B side by a known method, the output in a short wavelength region, S /
Excellent in electromagnetic conversion characteristics such as N, C / N, dropout,
A metal-coated magnetic recording medium for high density recording with a low error rate can be obtained. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like is dispersed and coated on the coating layer C as an underlayer of the metal powder-containing magnetic layer in the same organic binder as the magnetic layer. You can also do it. 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 recorder (DVC), data 8 mm, DDSIV, digital β cam, It is extremely useful as a tape medium such as D2, D3, and SX.

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

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

[0068]

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

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

(2) Average particle size I of particles (average particle size: 0.
Shimadzu CP-50 type centrifugal particle size analyzer (Centrifuga)
l Particle Size Analyzer)
It measured using. The particle diameter "equivalent sphere diameter" corresponding to 50 mass% is read from the integrated curve of the particles of each particle diameter calculated based on the obtained centrifugal sedimentation curve and the amount of the particles present, and this value is referred to as the above average particle diameter. ("Book particle size measurement technology", published by Nikkan Kogyo Shimbun, 1975, pages 242-24
7).

(3) Average particle size II (average particle size: 0.
Particles having an average particle diameter of less than 0.06 that form small protrusions were measured using a light scattering method. That is, Nicomp Inst
documents Inc. NICOMP MODE made by the company
L 270 SUBMICRON PARTICLE
The "equivalent sphere diameter" of the particles at the point of 50% by weight of all the particles determined by SIZER is shown.

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

[0073]

[Equation 6] F = V / D ³ (5)

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

(5) Surface Particle Frequency of Thermoplastic Resin Layer A The particle frequency on the surface of the thermoplastic resin layer A was measured by a scanning electron microscope. That is, five photographs of particles on the surface of the thermoplastic resin layer A from the surface of the coating layer C were randomly taken at a magnification of 5000 times or 10000 times, the surface particle frequency was counted, and from the average value, per 1 mm ² The particle number on the surface of the thermoplastic resin layer A was used as the particle frequency.

(6) Surface Protrusion Frequency of Coating Layer C The projection frequency on the surface of the coating layer C was measured by a scanning electron microscope. That is, the photograph of the surface of the coating layer C is magnified 3 times.
30 images were taken at random at 0000 times, the surface particle frequency was counted, and the average value was converted into the number of particles per 1 mm ² , and this value was defined as the surface protrusion frequency of the coating layer C.

(7) Layer Thickness The total thickness of the film is 10 at random with a micrometer.
The points were measured, and the average value was shown. The layer thickness was measured by measuring the layer thickness on the thin side by the method described below, and the layer thickness on the thick side was obtained by subtracting the layer thickness on the thin side from the total thickness. That is, by using a secondary ion mass spectrometer (SIMS), the concentration ratio (M ⁺ / of the element derived from the highest concentration of particles in the film in the depth range of 5000 nm from the surface layer to the carbon element of polyester) C ⁺ ) is the particle concentration and the depth from the surface is 5000
The analysis in the thickness direction was performed up to nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, the particle concentration once reaches the stable value 1 and then rises or decreases to reach the stable value 2 and may decrease monotonically. Based on this distribution curve, in the former case, (stable value 1 + stable value 2) /
With the depth that gives a particle concentration of 2, and in the latter case, the particle concentration has a depth that is 1/2 of the stable value 1 (this depth is deeper than the depth that gives a stable value 1) did. The measurement conditions are as follows. Measuring instrument Secondary ion mass spectrometer (SIMS); Physical Elect
6300 SIMS measurement conditions manufactured by ronics Primary ion species: O2 + secondary ion polarity: positive ion incident angle: 60 ° primary ion energy: 2 keV (1 keV / particle) primary ion current amount: 200 nA raster area: 400 μm × 400 μm analysis area: 120 μm × 120 μm electron beam correction: Yes

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

(8) Wavy protrusions on the film surface Using a non-contact three-dimensional roughness meter (TOPO-3D) manufactured by WYKO, depending on 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 was measured at × 980 μm (0.937 mm ² ) and the height and average width of the undulation were read from the obtained three-dimensional chart. The measurement was performed on a sample cut in the direction of 5 to 10 degrees with respect to the longitudinal direction of the film.

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

[0081]

(Equation 7)

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

(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 strain was applied at a strain rate of 10% / min, and calculation was performed by the following equation (7) using the first linear portion of the tensile stress-strain curve.

[0084]

[Equation 8] E = Δσ / Δε (7)

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

(11) Winding property After optimizing the winding condition at the slit, the width is 560 mm ×
A roll having a size of 9000 m was slit by 10 rolls, and after being left for 1 week, the roll-up property was evaluated based on the number of rolls that can be commercialized based on the occurrence of film wrinkles, and the following criteria.

(12) Manufacture of magnetic tape and evaluation of characteristics On the surface of the coating layer C of the biaxially oriented laminated film, two ferromagnetic thin films of 100% cobalt were formed by vacuum vapor deposition so as to have a thickness of 0.2 μm. (Each layer thickness is about 0.1 μm), a diamond-like carbon (DLC) film and a fluorine-containing carboxylic acid type lubricating layer are sequentially provided on the surface, and a back coat layer is formed on the surface of the thermoplastic resin layer B side by a known method. Was set up. After that, it was slit into a width of 8 mm and loaded into a commercially available 8 mm video cassette. The tape properties were then measured using the following commercially available equipment. Equipment used: 8 mm video tape recorder Sony EDV-6000 C / N measurement: Shibasoku Co., Ltd. Neumeter

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

Running property under high temperature and high humidity After recording / reproducing 500 times at a normal speed on a tape under high temperature and high humidity of 40 ° C. and 80% RH, C / N was measured and measured from the initial value. The deviation was judged according to the following criteria. ⊚: +0.0 dB or more with respect to the reference value ◯: −1.0 to +0.0 dB with respect to the reference value ×: Less than −1.0 dB with respect to the reference value

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

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

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

Example 1 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and lubricants shown in Tables 1 and 2 were used. Active particles were added and polymerization was carried out by a conventional method to obtain an intrinsic viscosity of 0.
60 polyethylene terephthalates for layer A and layer B (abbreviated as resin A and resin B, respectively) were obtained.

Each of the resins A and B was dried at 170 ° C. for 3 hours and then fed to two extruders to melt at a melting temperature of 2
The resin layer B was melted at 80 to 300 ° C., the resin layer B was laminated on one surface of the resin layer A using a multi-manifold type co-extrusion die, and rapidly cooled to obtain an unstretched laminated film having a thickness of 83 μm.

The unstretched film thus obtained is preheated, and the film temperature is set to 95% between low speed and high speed rolls.
In order to form a coating layer C on the A layer side of this longitudinally stretched film, the aqueous coating solution containing the resin and the particle materials shown in Table 1 (pre-solid A concentration of 1.5% by weight and polyoxyethylene nonylphenyl ether having an HLB value of 17.1 as a surfactant (containing 15% by weight in the total solid content) are applied by a kiss coat method, and then this longitudinally stretched film is supplied to a stenter. Then, it was stretched 4.1 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 have a thickness of 9.8 μm.
A laminated biaxially oriented polyester film of m was obtained. The thickness of each layer was adjusted by changing the discharge rate of the two extruders. Young's modulus of this film is 5
00kg / mm ^2, was transverse 700 kg / mm ^2.

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

[Examples 2 to 4, Comparative Examples 1 to 6 and 9] Table 1 and Table 1 show the resin and the inert particles forming the coating layer C, the particles contained in the thermoplastic resin 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 changes were made as shown in 2. However, in Comparative Example 4, no coating layer was provided. Further, Comparative Example 9 is a film having a conventional single-layer structure. Table 3 shows the properties of the films thus obtained and the properties of the ferromagnetic thin film-deposited magnetic tapes using these films.

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

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

The unstretched film thus obtained is preheated, and the film temperature is set to 13 ° C between low-speed and high-speed rolls.
It was stretched 3.6 times at 5 ° C. and rapidly cooled, then the aqueous coating solution of coating layer C shown in Table 1 was applied in the same manner as in Example 1, then fed to a stenter and transversely at 155 ° C. 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. The Young's modulus of these films is 560 kg / mm ^{2 in the} longitudinal direction and 1100 kg / m in the lateral direction.
m ² . However, in Examples 7, 8 and 9, the vertical magnification was 4.
And 0 × horizontal magnification 5.0, the Young's modulus of the laminated biaxially oriented polyester film, the longitudinal direction 600 kg / mm ^2, was transverse 900 kg / mm ^2. Table 3 shows the properties of the films thus obtained and the properties of the ferromagnetic thin film-deposited magnetic tapes using these films.

[0101]

[Table 1]

[0102]

[Table 2]

[0103]

[Table 3]

As is clear from Table 3, the laminated film according to the present invention has very flat one side and excellent electromagnetic conversion characteristics, and at the same time, it contains ultrafine particles of a specific shape contained in the coating layer C. The synergistic effect of the fine particles contained in the thermoplastic resin layer A forming fine projections on the surface, and also having waviness-like projections with a low height and a large width that do not adversely affect electromagnetic conversion characteristics. Due to the effect, it is extremely excellent in running durability and still characteristics under high temperature and high humidity when used as a magnetic recording medium, and also as an extremely excellent base film due to the effects of both the wavy projection and the rough surface on the opposite side. It also has the winding property of. On the other hand, the film according to the conventional technique shown in the comparative example cannot satisfy these four requirements at the same time.

[0105]

EFFECTS OF THE INVENTION According to the present invention, the high density which is excellent in the winding property, the defect-free property, the slipperiness and the easy handling property, especially the electromagnetic conversion property, the dropout, the running property of the magnetic layer, and the durability are excellent. A laminated film useful as a magnetic recording medium can be provided.

Claims (15)

[Claims] 1. Inert particles C having an average particle diameter of 10 to 50 nm and a volume shape factor of 0.1 to π / 6 have a surface projection frequency of 2.
The coating layer C, which is contained in an amount of 0 to 50.0 pieces / μm ² and has a protrusion height of 30% or more and less than 200% of the particle diameter of the particles, has an average particle diameter of 40 to 400 nm and a volume shape factor of 0. ．
The frequency of protrusions on the surface of the inert particles A of 1 to π / 6 is 5,000 to 5
Three layers provided on one surface of the thermoplastic resin layer A containing an amount of 10,000 pieces / mm ² and further laminated with a thermoplastic resin layer B containing inert particles B on the other surface of the thermoplastic resin layer A. A laminated film having a structure, wherein the surface of the coating layer C has 4 to 4 waviness-like protrusions having a roughness profile measured in a direction of 0 ± 10 degrees with respect to the longitudinal direction, having a height of 2 to 85 nm and an average width of 20 to 500 μm. A laminated film having a frequency of 2500 pieces / mm ² . 2. The inert particle B is composed of a single particle or two or more kinds of particles having different sizes, and the average particle diameter of the single particle or the average particle diameter and the heat of the largest particle of the two or more kinds of particles. The laminated film according to claim 1, wherein the thickness of the plastic resin layer 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 of single particles or two or more kinds of particles. It is the average particle size (μm) of the largest particle. 3. The average particle diameter of the single particles of the inert particles B or the largest particles of two or more kinds of particles is 0.2 to 1.
The laminated film according to claim 2, which has a thickness of 0 μm. 4. The center plane average roughness Ra _C of the surface of the coating layer _C.
Is 10 nm or less, The laminated film of Claim 1. 5. The laminated film according to claim 1, wherein the coating layer C is a film layer stretched in at least a uniaxial direction. 6. The laminated film according to claim 1, wherein the center plane average roughness Ra _B of the surface of the thermoplastic resin layer _B is 2 nm or more and less than 15 nm. In 7. The thickness of the thermoplastic resin layer A is 0.8μm or more, according to claim 1 or 2 thickness of the thermoplastic resin layer B is 1/2 or more the average particle diameter d _B of the inert particles B The laminated film described. 8. The laminated film according to claim 1, which has a total thickness of 2.5 to 20 μm. 9. The laminated film according to claim 1, wherein the thermoplastic resin of each of the layers A and B is an aromatic polyester. 10. The laminated film according to claim 9, wherein the aromatic polyester is polyethylene terephthalate or polyethylene 2,6 naphthalene dicarboxylate. 11. The laminated film according to claim 1, which is a base film for a magnetic recording medium. 12. The laminated film according to claim 11, wherein the magnetic recording medium is a metal thin film magnetic recording medium. 13. A magnetic recording medium having a magnetic layer thickness of 1 μm.
The laminated film according to claim 11, which is for the following coating type magnetic recording media. 14. The laminated film according to claim 11, 12 or 13, wherein the magnetic recording medium is a digital signal recording type magnetic recording medium. 15. The laminated film according to claim 11, wherein the magnetic recording medium is for an HDTV signal recording type magnetic recording medium.