JP3200347B2 - Laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

Conventional coating type magnetic recording media (magnetic recording media obtained by mixing magnetic powder in an organic polymer binder and coating on a non-magnetic support) have a low recording density and a long recording wavelength. While the thickness of the layer is as thick as about 2 μm or more, the ferromagnetic metal thin film formed by thin film forming means such as vacuum deposition, sputtering or ion plating has a very thin thickness of 0.2 μm or less and is extremely thin. Also in the case of the layer coating type, although the non-magnetic underlayer is provided,
A thickness of μm has been proposed and is very thin.

For this reason, in the above-mentioned high-density magnetic recording medium, the surface condition of the non-magnetic support (base film) has a great influence on the surface properties of the magnetic layer. Indicates that the surface state of the nonmagnetic support is directly expressed as irregularities on the surface of the magnetic layer (magnetic recording layer),
This causes noise in the recording / reproducing signal. Therefore, it is desirable that the surface of the non-magnetic support is as smooth as possible.

On the other hand, from the viewpoint of handling of a non-magnetic support (base film) such as film formation, transportation, scratching, winding and unwinding in the film forming process, if the film surface is too smooth, the film-film mutual The slipperiness of the material deteriorates, the booking phenomenon occurs, the shape when wound on a roll (roll formation) deteriorates, the product yield decreases,
As a result, the production cost of the product increases. Therefore, from the viewpoint of manufacturing cost, a non-magnetic support (base film)
Is desirably as rough as possible.

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

Further, in the case of a 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 material powder is mixed in an organic polymer bander and applied to a base film, a lubricant is dispersed in the binder to improve the running property of the magnetic layer surface. I can,
In the case of a metal thin film type magnetic recording medium, such measures cannot be taken, and it is extremely difficult to maintain a stable running property. Have.

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.

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

[0010]

However, in the above-mentioned method of applying a discontinuous film or a continuous film having fine irregularities by coating, the problems such as slipping between films and blocking can be solved, but the base film can be solved. In terms of handling, such as film formation, transport, scratching, winding and unwinding in the film forming process, from the viewpoint of product yield and product cost, the base film for high density and large capacity magnetic recording media There are problems with the application. Similar problems also exist in the conventional coextrusion technique or in the technique of combining the coextrusion technique with a discontinuous film or a continuous film. Further, in the case of a metal thin film type magnetic recording medium, there still remains a problem of running properties under high temperature and high humidity conditions.

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

[0012]

The object of the present invention is to provide, according to the present invention, first, inert particles A having an average particle size of 40 to 400 nm and a volume shape factor (f) of 0.1 to π / 6. On one surface of the thermoplastic resin layer A containing a surface protrusion frequency of 50,000 to 50,000 particles / mm ² , the surface containing inert particles B and having a surface rougher than the thermoplastic resin layer A. Is a biaxially oriented laminated film having a total thickness of 2.5 to 20 μm, wherein the surface of the thermoplastic resin layer A has a direction of 0 ± 10 degrees with respect to the longitudinal direction of the film. in is accomplished by the height 2～85Nm, laminated film characterized by having in wavy protrusions of 4-2500 cells / mm ² frequency of average width 20 to 500 [mu] m.

[0013] Examples of the thermoplastic resin in the present invention include polyester resins, polyamide resins, polyimide resins, polyether resins, polycarbonate resins, polyvinyl resins, polyolefin resins, and the like. Of these, polyester resins and aromatic polyesters are preferred.

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

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

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

In the present invention, the biaxially oriented laminated film has a thermoplastic resin layer A and a thermoplastic resin layer B, but the thermoplastic resins of the layers A and B may be the same or different.
Among them, the same resin is preferable. In particular, layer A and layer B are polyethylene terephthalate or polyethylene
It preferably comprises 2,6-naphthalenedicarboxylate.

The biaxially oriented laminated film of the present invention comprises:
It has a flat surface layer (that is, the thermoplastic resin layer A) and a rough surface layer (that is, the thermoplastic resin layer B).

This thermoplastic resin layer A has an average particle size of 40
To 400 nm, preferably 50 to 200 nm, more preferably 60 to 120 nm, and a volume shape factor of 0.1
Inactive particles A having a surface protrusion frequency of 50,000 to 50,000 particles / mm ² , preferably 0.75 to 40,000 particles / m 2.
m ² , more preferably 10,000 to 30,000 / mm ² .

The frequency of protrusions on this surface is 50,000 / mm ²
If it is less than 1, the friction of the magnetic layer against the magnetic head is high, the durability of the magnetic layer in repeated running is poor, and the transportability and scratch resistance in the film forming process are also poor. On the other hand, if the frequency of the protrusions is greater than 50,000 / mm ² , the dropout of the protrusions and the dropout will increase, which is not preferable.

The inert particles A have an average particle size of 40 nm.
If it is less than 1, the friction of the magnetic layer against the magnetic head is high, the durability of the magnetic layer in repeated running is poor, and the transportability and scratch resistance in the film forming process are also poor. On the other hand, when the average particle size is larger than 400 nm, the electromagnetic conversion characteristics as a high-density magnetic recording medium are adversely affected, which is not preferable.

The shape of the inert particles A is represented by the following formula 2.

[0023]

[Number 2] f = V / D ³ ······ 2

Here, f is the volume shape factor, V is the volume of the particle (μm ³ ), and D is the maximum diameter of the particle (μm). Has a volume shape factor (f) of 0.1 to π / 6, preferably 0.3 to π / 6, and more preferably 0.4 to π / 6. The shape whose volume shape coefficient (f) is π / 6 is a sphere (true sphere). Therefore, those having a volume shape factor (f) of 0.4 to π / 6 include substantially spheres, true spheres, and elliptical spheres such as rugby balls.
These are particularly preferred. Particles having a volume shape factor (f) of less than 0.1, for example, acicular particles, are not preferred because they lower the magnetic properties of the magnetic layer.

The inert particles A may be internally precipitated particles or additive particles as long as the above characteristics are satisfied, but the additive particles are more preferable. Examples of the added particles include crosslinked silicone resin, crosslinked polystyrene, crosslinked styrene-divinylbenzene copolymer, polymethyl methacrylate, methyl methacrylate copolymer, crosslinked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride, and polyacrylonitrile. , Fine particles comprising a heat-resistant organic polymer such as a benzoguanamine resin, silica,
Any of fine particles made of an inorganic compound such as alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, barium sulfate and the like may be used.

The thermoplastic resin layer A according to the present invention further has a height of 2 to 85 n in a roughness profile measured in the direction of 0 ± 10 degrees with respect to the longitudinal direction of the film on the surface.
m, preferably 2 to 50 nm, more preferably 2 to 25
nm, average width 20 to 500 μm, preferably 20 to 30
0 μm, more preferably 4 to 2500 undulations / mm ² , preferably 10 to 200
0 pieces / mm ² , more preferably 10 to 1000 pieces / mm
^It has surface properties that exist at a frequency of ² .

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

On the other hand, if the height of the undulations exceeds 85 μm, the electromagnetic conversion characteristics will be impaired, and it is not suitable as a base film for a high-density magnetic recording medium. If the average width of the undulating projection is less than 20 μm, the height of the undulating projection is 2
In the region of 5 nm or less, the transportability in the film forming process and the running property of the tape become insufficient.

The direction of measurement of the undulating projection is 0 ± 10 degrees with respect to the longitudinal direction of the film, which is the same as that of the magnetic recording system to which the high-density magnetic recording tape using the base film according to the present invention is applied. By aligning in the same direction as the track scanned by the head on the tape.

The undulations in the thermoplastic resin layer A are not limited by the method of forming the undulations, but are caused by the push-up action of the layer A accompanying the stretching of the inert particles B contained in the thermoplastic resin layer B. Is preferred.

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

[0032]

Equation 3] preferably set to _{4 ≦ t A / d B ≦} 40 ...... 1 so as to satisfy the. The t _A / d _B is from 4 to 25, further 4-16, particularly preferably 4-8.

The waviness-like projections have a very long width or period especially in comparison with the wavelength (less than 1.0 μm) on the surface of the high-density magnetic recording medium, and the fine inert particles contained in the thermoplastic resin layer A The height of the protrusions is equal to or less than the height of the protrusions, and the protrusions due to the fine particles of the thermoplastic resin layer A, the long-term undulation, and the rough surface of the thermoplastic resin layer B can be obtained without adversely affecting the electromagnetic conversion characteristics. The synergistic effect of the three
An object of the present invention is to solve all the problems of a conventional base film for a high-density magnetic recording medium.

The thermoplastic resin layer A according to the present invention has a surface roughness of 10 nm or less in center plane average roughness.
Further, it is preferably 5 nm or less, particularly preferably 2 nm or less, particularly preferably 1 nm or less. If the surface roughness is too rough, the electromagnetic conversion characteristics and the like decrease, which is not preferable.

In the present invention, the thermoplastic resin layer B forming the rough surface contains the inert particles B as described above. This surface has a surface roughness greater than that of the thermoplastic resin layer A. In other words, the center plane average roughness WRa ^B of the thermoplastic resin layer ^B and the center plane average roughness W of the thermoplastic resin layer A
Ra ^A is the following formula 3.

[0036]

[Formula 4] WRa ^B > WRa ^A ... 3

Here, WRa ^A and WRa ^B are non-contact 3 measured on the outer surface of each of the thermoplastic resin layers A and B.
The dimensional center plane average roughness. To be satisfied. WRa ^B is W
It is preferable that Ra is larger than Ra ^A by 1 nm or more, more preferably 1.5 nm or more. The center plane average roughness WRa ^B is 2 nm or more and less than 15 nm, more preferably 3 to 10 nm, particularly 3
It is preferably about 7 nm.

The surface roughness WRa ^B of the thermoplastic resin layer ^B is 1
If it is 5 nm or more, it is difficult for the height and average width of the undulating protrusions on the surface of the thermoplastic resin layer A to satisfy the above-mentioned requirements, and if it is less than 2 nm, handling properties such as transportability, tape running properties, etc. Insufficient and undesirable. Further W
When Ra ^B is less than WRa ^A , the handling properties such as transport, scratching, winding and unwinding of the base film in the film forming process are deteriorated due to its flatness.
The blocking phenomenon occurs due to the deterioration of the slipperiness between the films, the shape (roll formation) when wound on a roll deteriorates, the productivity decreases, the product yield decreases,
As a result, the production cost of the product is increased, which is not preferable.

In order to impart the above-mentioned surface characteristics to the thermoplastic resin layer B and to make the thermoplastic resin layer A exhibit the above-mentioned undulations, the average particle diameter dB of the inert particles _B is 0.2 to 0.2. 1
μm, further 0.2-0.8 μm, especially 0.2-0.6 μm
m is preferable. The average particle diameter d _B is the average particle size in the case where the inert particles B are made of a single particle, and when composed of two or more kinds of particles having different sizes average particle of the largest particles of these Means diameter.

[0040] As the inert particles having an average particle diameter d _B, may be mentioned those exemplified as the inert particles A. Further, when the particles are composed of two or more kinds of particles,
As the third small particles, fine particles having an average particle size of 0.01 μm or more and 0.1 μm or less, for example, colloidal silica,
Fine particles such as alumina having crystal forms such as α, γ, δ, and θ can be preferably used. Inert particles A
Fine particles having an average particle size of 0.01 μm or more and 0.1 μm or less can be used.

The content of the fine particles is 0.001 to 5% by weight, more preferably 0.005 to 1% by weight, particularly 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 thickness construction of the flat layer A and the rough surface layer B, as wavy projections generated on the surface of the flat layer A, the average particle diameter d _B and the flat layer A of the inert particles B to be added to Somenso B Is set to a suitable thickness from the above layer thickness t _A. Is by the thickness t _A of the flat layer A is 0.8μm or more, and the thickness t _B of the rough surface layer B is more than 1/2 of the average particle diameter d _B of the inert particles B ([mu] m) Is preferred.

The laminated film of the present invention can be manufactured by a conventionally known method or a method accumulated in the art. Among them, it is preferable to produce by a co-extrusion method. For example, in the case of a biaxially oriented polyester film, in the extrusion die or before the die (generally, the former is referred to as a multi-manifold method, and the latter is referred to as a feed block method), the polyester A of the flat layer containing the inert particles A described above is used. The polyester B of the rough surface layer containing the inert particles B is laminated and compounded in a molten state to form a laminated structure having the above-described preferred thickness ratio, and then the melting point Tm ° C to (Tm
+70) After co-extrusion in the form of a film at a temperature of
It is rapidly cooled and solidified at 90 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is uniaxially (longitudinal or transverse) (Tg-10) to (Tg + 7) according to a conventional method.
0) At a temperature of 0 ° C. (however, Tg: glass transition temperature of the polyester) at a magnification of 2.5 to 8.0 times, preferably 3.
The film is stretched at a magnification of 0 to 7.5 times, and then at a temperature perpendicular to the above direction at a temperature of Tg to (Tg + 70) ° C at a magnification of 2.5 to 8.0 times, preferably 3.0 to 7.5 times. It is stretched at a magnification of. 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 stretching ratio is usually 9 times or more, preferably 12 to 35 times, more preferably 15 to 26 times as the area stretching ratio. Subsequently, the biaxially oriented film is heat-set and crystallized at a temperature of (Tg + 70) to (Tm-10) ° C., for example, at 180 to 250 ° C., so that excellent dimensional stability is imparted. The heat setting time is 1 to
60 seconds is preferred.

By this method, a biaxially oriented laminated polyester film having good interlayer adhesion can be obtained.

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

In the production of the laminated film, additives other than the above-mentioned inert particles, such as a stabilizer, a coloring agent, a specific resistance modifier for the molten polymer, and the like can be added to the thermoplastic resin, if desired.

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

The laminated film of the present invention is formed on the thermoplastic resin layer A, that is, on the flat surface by iron, cobalt, chromium or an alloy containing these as a main component by a method such as vacuum deposition, sputtering, or ion plating. Alternatively, a ferromagnetic metal thin film layer composed of an oxide is formed, 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. By providing a known back coat layer on the surface of the thermoplastic resin layer B side, the output in the short wavelength region, the electromagnetic conversion characteristics such as S / N, C / N, etc. are particularly excellent, and the high density with little dropout and error rate is provided. It can be used as an evaporation type magnetic recording medium for recording. This vapor-deposited electromagnetic 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 tape medium for DDSIV.

The laminated film of the present invention is also characterized in that the thermoplastic resin layer A, ie, the flat surface side surface, is coated with iron or a needle-like fine magnetic powder containing iron as a main component by vinyl chloride, vinyl chloride / vinyl acetate copolymer. Etc., uniformly dispersed in a binder, and applied so that the magnetic layer thickness is 1 μm or less, preferably 0.1 to 1 μm, and further provided a back coat layer on the surface of the thermoplastic resin layer B side by a known method. In particular, the output in the short wavelength region, and excellent electromagnetic conversion characteristics such as S / N and C / N,
A metal-coated magnetic recording medium for high-density recording with low dropout and error rate can be obtained. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like may be dispersed and coated on the layer A in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. Can also. This metal-coated magnetic recording medium is an 8 mm video for analog signal recording, Hi8, β cam SP, W-VH
It is very useful as a tape medium for S, digital video cassette coder (DVC) for recording digital signals, data 8 mm, DDSIV, digital β cam, D2, D3, SX, etc.

The laminated film of the present invention is also characterized in that, on the thermoplastic resin layer A, that is, on the flat surface side surface, acicular fine magnetic powder such as iron oxide or chromium oxide or plate-like fine magnetic powder such as barium ferrite is chlorided. Uniformly dispersed in a binder such as vinyl, vinyl chloride / vinyl acetate copolymer, and applied so that the thickness of the magnetic layer is 1 μm or less, preferably 0.1 to 1 μm, and further known to the surface of the thermoplastic resin layer B side. By providing the back coat layer by the method described above, the vapor-deposited magnetic recording medium for high-density recording is particularly excellent in output in the short wavelength region, excellent in electromagnetic conversion characteristics such as S / N, C / N, etc., and has little dropout and error rate. It can be. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like may be dispersed and coated on the layer A in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. You can also. This oxide-coated magnetic recording medium is useful as a high-density oxide-coated magnetic recording medium such as a data streamer QIC for digital signal recording.

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

[0052]

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

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

(2) Average particle size I of particles (average particle size: 0.1
06μm or more) Shimadzu CP-50 Centrifugal Particle Size Analyzer (Centrifugal Particle)
It is measured using a Size Analyzer). From the integrated curve of particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, the particle size “equivalent sphere diameter” corresponding to 50 mass percent is read, and this value is defined as the above average particle size. (Book
"Granularity measurement technology", published by Nikkan Kogyo Shimbun, 1975, page 2
42-247).

(3) Average particle size II 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 In
instruments Inc. NICOMP M
ODEL 270 SUBMICRON PARTIC
Expressed as the "equivalent spherical diameter" of the particle at the point of 50% by weight of the total particle as determined by LE SIZER.

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

[0057]

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

(5) Frequency of Projection on Film Surface The frequency of projection on the film surface is measured by a scanning electron microscope. That is, a photograph of the surface of the laminated film was taken at a magnification of 5000.
Five images were taken randomly at 1 × or 10000 ×, the frequency of surface protrusions was counted, and the average value was converted into the number of protrusions per 1 mm ² , and this value was taken as the surface protrusion frequency of the film.

(6) Layer Thickness The total thickness of the film is randomly 10 micrometers.
Measure the points and use the average value. The layer thickness is obtained by measuring the layer thickness on the thinner side by the method described below, and subtracting the layer thickness on the thicker side from the layer thickness on the thinner side than the total thickness. That is, using a secondary ion mass spectrometer (SIMS), a concentration ratio (M ⁺ /) of an element originating from the highest concentration particle among the particles in the film having a depth of 5000 nm from the surface layer to the carbon element of the polyester. C ⁺ ) is defined as the particle concentration and the depth from the surface is 500
Analysis in the thickness direction is performed up to 0 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, there are cases where the particle concentration once reaches a stable value 1 and then increases or decreases to a stable value 2 and cases where the particle concentration monotonously decreases. Based on this distribution curve, in the former case, the depth gives a particle concentration of (stable value 1 + stable value 2) / 2, and in the latter case, the depth at which the particle concentration becomes 1/2 of the stable value 1 The thickness (this depth is deeper than the depth giving a stable value of 1) was taken as the layer thickness of the layer.

The measurement conditions are as follows. Measurement device Secondary ion mass spectrometer (SIMS); West Germany, ATOM
IKA A-DIDA3000 Measurement conditions Primary ion species: O2 + Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6.0 × 10 ⁻⁹ Torr E-GUNN : 0.5KV-3.0A

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

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

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

[0064]

(Equation 6)

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

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

[0067]

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) Winding property After optimizing the winding conditions at the time of slitting, the width is 560 mm ×
A roll having a size of 9000 m and a slit of 10 rolls is evaluated according to the following criteria based on the number of rolls that can be commercialized according to the occurrence of film wrinkles after being left for one week.

(11) Manufacture of Magnetic Tape and Characteristic Evaluation A 100% cobalt ferromagnetic thin film was formed to a thickness of 0.02 μm on the thermoplastic resin A of the biaxially oriented laminated film, that is, on the flat surface side by vacuum evaporation. Two layers (each layer having a thickness of 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 known method is further provided on the surface of the thermoplastic resin B side. To form a back coat layer. 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 EDV
-6000 C / N measurement: Noise meter manufactured by Shibasoku Co., Ltd. C / N measurement A signal with a recording wavelength of 0.5 μm (frequency: about 7.4 MHz) is recorded, and the reproduction signal of 6.4 MHz and 7.4 MHz is measured. The ratio is expressed as a relative value, where the C / N of the tape is O / dB, and the C / N of a commercially available 8 mm video-evaporated tape is OdB. Running property under high temperature and high humidity When the tape is continuously played back under high temperature and high humidity of 50 ° C. and 80% RH, the reproduced image is observed, and it is determined whether or not the image fluctuates.

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

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 inerts shown in Tables 1 and 2 as lubricants The particles are added and polymerized by a conventional method to obtain polyethylene terephthalate (PE) for layers A and B having an intrinsic viscosity of 0.60.
T) (resin A and resin B, respectively) were obtained.

After drying each of the resin A and the resin B at 170 ° C. for 3 hours, they were supplied to two extruders and melted at a melting temperature of 28 ° C.
The resin layer was melted at 0 to 300 ° C., a resin layer B was laminated on one side of the resin layer A using a multi-manifold type co-extrusion die, and rapidly cooled to obtain a 129 μm-thick unstretched laminated film.

The obtained unstretched film is preheated, stretched 3.2 times at a film temperature of 95 ° C. between low-speed and high-speed rolls, quenched, and then supplied to a stenter.
The film was stretched 4.1 times in the transverse direction at ℃. The obtained biaxially stretched film was heat-set with hot air of 220 ° C. for 4 seconds, and the thickness was 9.
An 8 μm laminated biaxially oriented polyester film was obtained. The thickness of each layer was adjusted by the discharge amount of two extruders. The Young's modulus of this film is 500 kg /
mm ² , and 700 kg / mm ² in the lateral direction.

[0075] surface properties of the laminated biaxially oriented film, of the inert particles contained in the thickness t _A and the rough surface layer B of the flat layer A, the ratio of the average particle diameter d _B of the largest particles t _A / d _B ,
Table 3 shows the winding properties and the characteristics of the magnetic tape deposited with a ferromagnetic thin film using this film.

[Examples 2, 3 and Comparative Examples 1, 2, 5, 6]
A laminated biaxially oriented polyester film was obtained in the same manner as in Example 1, except that the particles shown in Table 1 were used and the layer thicknesses of the rough surface layer B and the flat layer A were adjusted as shown in Tables 1 and 2. . However, Comparative Examples 5 and 6 are films having a single-layer structure. Table 3 shows the characteristics of the obtained laminated biaxially oriented films and the characteristics of the magnetic tape deposited with a ferromagnetic thin film using these films.

[Examples 4 to 7, Comparative Examples 3, 4, 7, and 8]
For the flat layer A and the rough layer B in the same manner as in Example 1 except that the particles shown in Table 1 were used and the same molar amount of dimethyl 2,6-naphthalenedicarboxylate was used instead of dimethyl terephthalate. Polyethylene-2,6-naphthalate (PEN) (resin A and resin B, respectively) was obtained.

The resin A and the resin B were dried at 170 ° C. for 6 hours, respectively, and an unstretched laminated film in which each layer thickness was adjusted in the same manner as in Example 1 was obtained. However, Comparative Examples 7 and 8 are films having a single-layer structure.

The unstretched film thus obtained is preheated, and is further rolled between low and high speed rolls at a film temperature of 135 ° C. for 3.6.
Stretched twice, quenched and then fed to a stenter,
The film was stretched 6.0 times in the transverse direction at 5 ° C. 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 (however, Comparative Examples 7 and 8 have a single-layer structure).

The Young's modulus of these films was 65
0 kg / mm ^2, was laterally 1100 kg / mm ^2. However, Examples 6 and 7 each have a vertical magnification of 4.85 × horizontal magnification 5.0 and a total thickness of 5.9 μm; a vertical magnification of 4.0 × horizontal magnification 5.0 and a total thickness of 7.5 μm. The Young's modulus of the polyester film is 700 kg / mm in the longitudinal direction.
² , 730 kg / mm ^{2 in the} horizontal direction; 600 kg / m in the vertical direction
m ² and 900 kg / mm ² in the lateral direction. Table 3 shows the surface characteristics of these films and the characteristics of the ferromagnetic thin film-deposited magnetic tape using these films.

As is clear from Table 3, the laminated film according to the present invention is excellent in scratch resistance, very flat on one side, has excellent electromagnetic conversion characteristics, and has very small protrusions on the surface. And stable running property under high temperature and high humidity as a tape due to an effect having both a low height and a large width undulation which does not adversely affect the electromagnetic conversion characteristics, and a surface opposite to the undulation. Due to the both effects of the rough surface, the film has an extremely excellent winding property as a base film. On the other hand, the film of the comparative example cannot satisfy these four requirements at the same time.

[0082]

[Table 1]

[0083]

[Table 2]

[0084]

[Table 3]

[0085]

According to the present invention, winding property, defect-free property,
It is possible to provide a laminated film which is excellent in slipperiness and handling properties, and is particularly useful for a high-density magnetic recording medium having excellent electromagnetic characteristics, dropout, running properties of a magnetic layer, and durability.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideaki Watanabe 3-37-19 Koyama, Sagamihara City, Kanagawa Prefecture Tegami Co., Ltd. Sagamihara Research Center (56) References JP-A-5-84818 (JP, A) JP-A-4-294124 (JP, A) JP-A-5-77318 (JP, A) JP-A-58-68225 (JP, A) JP-A-4-138251 (JP, A) JP-A-6-114923 (JP) JP-A-5-220835 (JP, A) JP-A-3-210339 (JP, A) JP-A-2-16051 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B32B 1/00-35/00 EPAT (QUESTEL) WPI / L (QUESTEL)

Claims (12)

(57) [Claims] 1. An inert particle A having an average particle diameter of 40 to 400 nm and a volume shape factor (f) of 0.1 to π / 6 in such an amount that the frequency of protrusions on the surface becomes 50,000 to 50,000 / mm ² . A thermoplastic resin layer B containing inert particles B on one surface of a thermoplastic resin layer A and having a rougher surface than the thermoplastic resin layer A
There are laminated, the total thickness of a biaxially oriented laminated film Ru 2.5~20μm der, the surface of the thermoplastic resin layer A,
In the direction of 0 ± 10 degrees to the film longitudinal direction, height 2
4 undulating protrusions having a thickness of 85 nm and an average width of 20 to 500 μm.
A laminated film having a frequency of up to 2500 pieces / mm ² . 2. The inert particle B is composed of a single particle or two or more types of particles having different sizes,
2. The laminated film according to claim 1, wherein the average particle diameter of the largest particle among the particles of the kind or more and the thickness of the thermoplastic resin layer A satisfy the following formula 1. [Number 1] _{4 ≦ t A / d B ≦} 40 ······ 1 wherein, t _A is the thickness of the thermoplastic resin layer A (μm), d _B is an average particle diameter ([mu] m alone particle ) Or the average particle diameter (μm) of the largest particle of the two or more particles. 3. The laminated film according to claim 2, wherein the inert particles B have an average particle diameter of a single particle or an average particle diameter of the largest particle among two or more particles is 0.2 to 1 μm. 4. The laminated film according to claim 1, wherein the center surface average roughness WRa ^A of the surface of the thermoplastic resin layer ^A is 10 nm or less. 5. The laminated film according to claim 1, wherein the center plane average roughness WRa ^B of the surface of the thermoplastic resin layer ^B is 2 nm or more and less than 15 nm. In 6. 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 laminated fill-beam according to. 7. The laminated film according to claim 1, wherein each of the thermoplastic resins of the layers A and B is an aromatic polyester. 8. The laminated film according to claim 7 , wherein the aromatic polyester is polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate. 9. The laminated film according to claim 1, which is a base film of a magnetic recording medium. 10. The laminated film according to claim 9 , wherein the magnetic recording medium is a metal thin film type magnetic recording medium. 11. The magnetic recording medium according to claim 1, wherein the thickness of the magnetic layer is 1 μm.
The laminated film according to claim 9 , which is the following coating type magnetic recording medium. 12. The laminated film according to claim 9, wherein the magnetic recording medium is a digital signal recording type magnetic recording medium.