JP2003103739A - Laminated polyester film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated thermoplastic resin film with high electromagnetic conversion properties which exhibits outstanding anti-blocking properties, flatness and suitability for processing when the film is used as a base film for a metal vapor-deposited magnetic recording medium. SOLUTION: This laminated polyester film is formed of a polyester layer A and a polyester layer B laminated on one of the sides of the former. A polyester constituting the polyester layer B has an intrinsic viscosity of 0.55 or more and a terminal carboxyl group density of 35 eq/10<6> g or more and contains an ester wax composed of an inert particle (B), an ester wax composed of an aliphatic monocarboxylic acid with eight or more carbon atoms and a polyhydric alcohol. In addition, the film has an exposed face of its polyester layer A side which indicates a centerline roughness WRaA (25) of 0.1 to 4 nm when measured by a non-contact three dimensional roughness meter at 25X magnification and a centerline roughness WRaA (2.5) of 1 to 15 nm when measured by the same roughness gauge at 2.5X magnification.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated polyester film. More specifically, a laminated polyester useful as a support for a magnetic recording medium excellent in electromagnetic conversion characteristics and running durability, particularly a ferromagnetic metal thin film type magnetic recording medium for recording digital data, such as a digital video cassette tape or a data storage tape. Regarding film.

[0002]

2. Description of the Related Art In recent years, progress has been made in the densification of magnetic recording media. Metal thin film magnetic recording media are being developed and put to practical use. For example, Co vapor deposition tape (Japanese Patent Laid-Open No. 54-147010), Co-C
Perpendicular magnetic recording medium made of r alloy (Japanese Patent Laid-Open No. 52-134)
No. 706) is known.

In a conventional coating type magnetic recording medium (a magnetic recording medium prepared by mixing magnetic powder in an organic polymer binder and coating it on a non-magnetic support), the thickness of the magnetic layer is as thick as about 2 μm or more, and The recording density is low and the recording wavelength is long.
On the other hand, the metal thin film in the ferromagnetic metal thin film type magnetic recording medium 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.

Therefore, the degree of influence of the surface condition of the non-magnetic support (base film) on the surface property of the magnetic recording layer is much larger in the metal thin film. That is, in the case of a ferromagnetic metal thin film type magnetic recording medium, the surface condition of the non-magnetic support is directly expressed as the unevenness of the surface of the metal thin film, which causes noise of 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, conveyance in the processing step, winding and unwinding, it is preferable that the film has excellent slipperiness. If the film surface is too smooth, the slipperiness between the film and the film is deteriorated and the surface is likely to be scratched, resulting in a decrease in product yield and an increase in product manufacturing cost. Therefore, from the viewpoint of manufacturing cost, the surface of the non-magnetic support is preferably as rough as possible.

Further, in the case of a metal thin film type magnetic recording medium, in order to improve the adhesion between the metal thin film and the base film, the surface of the base film, which is called ion bombardment treatment, is activated by ions before forming the metal thin film. Process to convert. Then, when forming the metal thin film, the back surface of the film is cooled so that the film surface is heated at a considerably high temperature and the base film is not melted or physical properties such as mechanical properties are deteriorated. For this backside cooling, a method of winding a base film around a drum-shaped cooling body is usually adopted.
At that time, both ends of the base film are masked so that a metal thin film is not formed on the drum surface.

Therefore, at both ends of the sample roll that has passed through the vapor deposition process, the portions where the metal thin film has not been formed by this masking are continuously formed in the longitudinal direction with the surface being activated by the ion bombardment treatment. Exists in. And this part, in the state rolled up in a roll, will come into contact with the opposite surface side with high force,
It is easy to cause blocking. When a metal thin film type magnetic recording medium is manufactured, a back coat layer and, if necessary, a top coat layer are provided after vapor deposition of a metal thin film, but when the blocking occurs in these processing steps, There is a problem that the film is likely to be cut or wrinkled, and the yield is significantly reduced. In order to prevent such blocking, the surface of the non-magnetic support is preferably rough.

As described above, the surface of the non-magnetic support is required to be smooth from the viewpoint of electromagnetic conversion characteristics,
On the other hand, roughness is required from the viewpoints of handleability, manufacturing cost, and blocking prevention. By the way, in order to satisfy the conflicting requirements as described above, a laminated film composed of two layers, in which the surface of one layer is rougher than the surface of the other layer (for example, Japanese Patent Publication No. 1-263338) is proposed. ing. However, in this laminated film, the high projections of the rough surface layer are transferred to the flat surface layer, and the large particles added to the rough surface layer push up to the flat surface layer, resulting in electromagnetic conversion characteristics when used as a magnetic recording medium. Has a problem of deterioration.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to be excellent in blocking resistance, flatness and processability, and to be excellent when used as a metal vapor deposition thin film type magnetic recording medium. Another object of the present invention is to provide a laminated thermoplastic resin film having excellent electromagnetic conversion characteristics.

[0010]

According to the present invention, an object of the present invention comprises a polyester layer A and a polyester layer B laminated on one side thereof, and the polyester constituting the layer B has an intrinsic viscosity of Inactive particles (B) having a terminal carboxyl group concentration of 35 eq / 10 ⁶ g or more at 0.55 or more
And an ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol, and the exposed surface on the polyester layer A side of the laminated polyester film is 25 times as magnified by a non-contact three-dimensional roughness meter. The center line roughness WRaA (25) measured by
Center line roughness WR measured at a magnification of 2.5 times with the same roughness meter
Achieved by a laminated polyester film characterized in that the aA (2.5) is in the range of 1-15 nm.

In a preferred embodiment of the present invention, the average particle size of the inert particles (B) is 50 to 1000 nm.
The content of the particles is in the range of 0.001 to 1% by weight based on the weight of the polyester layer B, and the non-contact three-dimensional surface of the polyester layer B on the side not in contact with the polyester layer A. Ten-point average roughness measured by a roughness meter (WR
zB) is in the range of 30 to 300 nm, the polyester constituting the polyester layers A and B is polyethylene terephthalate or polyethylene-2,6-naphthalate, and the surface of the polyester layer A not in contact with the polyester layer B is The coating layer C is laminated, and the coating layer C contains 0.5 to 3 of the inert particles C having an average particle diameter of 10 to 50 nm and a volume shape factor of 0.1 to π / 6.
0% by weight, the exposed surface on the side of the polyester layer A of the laminated polyester film forms the ferromagnetic metal thin film layer, and is used as a support for the magnetic recording medium. It also includes a laminated polyester film that satisfies the requirement of being a tape.

Furthermore, according to the present invention, there is also provided a magnetic recording medium having as a support the laminated polyester film for a magnetic recording medium according to the present invention.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The laminated polyester film of the present invention is a laminated film in which a polyester layer B is laminated on one side of a polyester layer A.

Examples of the polyesters A and B forming the polyester layers A and B include aliphatic polyesters and aromatic polyesters, and aromatic polyesters are particularly preferable. The polyesters A and B may be the same type or different types.

As the aromatic polyester, polyethylene terephthalate, polyethylene isophthalate,
Examples thereof include polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, and polyethylene-2,6-naphthalate (polyethylene-2,6-naphthalene dicarboxylate). Of these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferred.

These polyesters may be homopolyesters or copolyesters. In the case of copolyesters, for example, polyethylene terephthalate or polyethylene-2,6-naphthalate copolymerization components include diethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyethylene glycol, 1,4-cyclohexanediene. Other diol components such as methanol and p-xylylene glycol, adipic acid,
Sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (in the case of polyethylene-2,6-naphthalate), 2,6-naphthalenedicarboxylic acid (in the case of polyethylene terephthalate), 5-sodium sulfoisophthalic acid, etc. And dioxycarboxylic acid components such as p-oxyethoxybenzoic acid. The amount of these copolymerization components is 20 mol% or less, and further 10 mol% unless the effects of the present invention are impaired.
The following is preferable.

Further, trimellitic acid, pyromellitic acid,
It is also possible to copolymerize a polyfunctional compound having three or more functional groups such as pentaerythritol. In this case, it is preferable to copolymerize the polymer in a substantially linear amount, for example, 2 mol% or less.

The copolymerization components in the case of polyesters other than polyethylene terephthalate and polyethylene-2,6-naphthalate may be considered in the same manner as described above.

The polyester may be a pigment, a dye, an antioxidant, an antistatic agent, a light stabilizer, a light-shielding agent (for example, carbon black, etc.) as long as the effects of the present invention are not impaired.
If desired, additives such as titanium oxide) can be included.

In the laminated polyester film of the present invention, the polyester layers A and B are preferably made of the same polyester, but they may be made of different polyesters. For example, a laminated film in which the layers A and B are made of polyethylene terephthalate or polyethylene-2,6-naphthalate is preferable, but the layer A (or layer B) is polyethylene terephthalate and the layer B (or layer A) is polyethylene-2,6. It may be a laminated film made of naphthalate.

The polyester A forming the polyester layer A can be manufactured by a conventionally known method. For example, polyethylene terephthalate can be produced by a method in which terephthalic acid and ethylene glycol are esterified or dimethyl terephthalate and ethylene glycol are transesterified, and then the reaction product is polycondensed.

The polyester A obtained by the above method (melt polymerization) can be made into a polymer having a higher degree of polymerization by a polymerization method in a solid state (solid phase polymerization), if necessary.

Known catalysts can be used in this polymerization, and manganese, calcium, magnesium, titanium oxides, chlorides, carbonates, carboxylates and the like are preferable as the transesterification catalyst in the melt polymerization, and acetic acid is particularly preferable. Preferable salts include manganese acetate, calcium acetate, magnesium acetate and titanium acetate. Examples of polycondensation catalysts include antimony compounds, titanium compounds, and germanium compounds.

Preferred examples of the antimony compound include antimony trioxide, antimony pentoxide and antimony acetate. The titanium compound is preferably an organic titanium compound, for example, JP-A 5-2.
The thing described in the 98670 gazette can be mentioned. More specifically, titanium alcoholate or organic acid salt, a reaction product of a tetraalkyl titanate and an aromatic polyvalent carboxylic acid or an anhydride thereof, and the like can be exemplified, and preferable specific examples include titanium tetrabutoxide, titanium isopropoxide, and titanium oxalate. , Titanium acetate, titanium benzoate, titanium trimellitate, a reaction product of tetrabutyl titanate and trimellitic anhydride, and the like. Furthermore, examples of the germanium compound include those described in Japanese Patent No. 2792068. Specifically, amorphous germanium oxide, crystalline germanium, a solution of germanium oxide dissolved in glycol in the presence of an alkali metal or an alkaline earth metal or their compounds, or germanium oxide dissolved in water, glycol And a glycol solution of germanium oxide prepared by distilling off water to prepare a solution.

Further, it is preferable that the polyester A contains a phosphorus compound which is conventionally added in the polyester manufacturing process in order to maintain thermal stability. This phosphorus compound is not particularly limited, but orthophosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, tri-n
-Butyl phosphate is preferred.

The intrinsic viscosity of the polyester A is 0.45
The above is preferable. More preferably 0.47 or more,
Particularly preferably, it is 0.50 or more. When the intrinsic viscosity of this polyester A is less than 0.45, bleeding out of oligomers and the like, breakage in the film forming and winding step, etc. occur,
Not preferable. As a method of increasing the intrinsic viscosity of the polymer in the polyester A to 0.45 or more, a method of increasing the intrinsic viscosity of the raw material polymer, mild melt extrusion conditions (adoption of extrusion conditions to suppress polymer deterioration as much as possible), etc. Is used.

By the way, the exposed surface of the laminated polyester of the present invention on the side of the polyester layer A has a center line roughness WRaA (2) measured by a non-contact three-dimensional roughness meter at a magnification of 25 times.
5) is in the range of 0.1 to 4 nm, and the centerline roughness WRaA (2.5) measured by the same roughness meter at a magnification of 2.5 times is 1.
It should be in the range of -15 nm, preferably in the range of 2.5-12 nm, and particularly preferably in the range of 3-10. In order to achieve such a surface shape, it is preferable that the polyester layer A contains substantially no particles. When the polyester layer A contains substantially no particles, excellent electromagnetic conversion characteristics can be obtained when used as a magnetic recording medium.

The polyester B forming the polyester layer B in the present invention can be produced by a conventionally known method, like the polyester A. At that time, a known catalyst can be used, and it is preferable to use the same catalyst as the polyester A. Further, like the polyester A, it is preferable to contain a phosphorus compound.

The intrinsic viscosity of polyester B is 0.55 or more, preferably 0.57 or more, particularly preferably 0.60.
That is all. The intrinsic viscosity of this polyester B is 0.55
If it does not satisfy the above condition, the bleed-out of the oligomer or the like and the dropout of the protrusions become severe, and these are transferred to the opposite surface to cause a trouble of impairing the smoothness of the A layer. Polyester B
In order to make the intrinsic viscosity of 0.55 or more, the intrinsic viscosity of the raw material polymer is increased beforehand by the solid-state polymerization method or the melt extrusion condition is made mild (extrusion conditions that suppress polymer deterioration as much as possible are adopted. ) Etc. are used.

The concentration of the terminal carboxyl group of the polyester B in the present invention must be 35 eq / 10 ⁶ g or more. It is preferably 38 eq / 10 ⁶ g or more. When the terminal carboxyl group concentration is less than 35 eq / 10 ⁶ g, the affinity for the inactive particles B in the polyester B is poor, and the inactive particles B drop out during the film production and the metal thin film forming step, and the polyester layer A And the smoothness is reduced. A conventionally known method is used to adjust the terminal carboxyl group concentration of the polyester layer B to 35 eq / 10 ⁶ g or more, and for example, a method of holding the melt after completion of polycondensation can be exemplified. The upper limit of the terminal carboxyl group concentration of polyester B is 60 eq /
It is 10 ⁶ g or less, from the viewpoint of the thermal stability of the polyester B, and particularly preferably not more than 55eq / 10 ⁶ g.

By the way, as described above, the exposed surface on the polyester layer A side in the present invention has a center line roughness W measured by a non-contact three-dimensional roughness meter at a magnification of 25 times and a magnification of 2.5 times.
RaA (2.5) needs to be in a certain range. In order to achieve such a surface shape, it is preferable that the polyester layer A contains substantially no particles and the polyester layer B contains inert particles B. When the inert particles B are not contained, problems such as blocking occur in the film manufacturing process and the metal thin film molding process. The average particle diameter (dB) of the inert particles B is preferably 50 to 1,000 nm, more preferably 100 to 1000 nm.
800 nm, more preferably 150 to 700 n
m, most preferably 200 to 600 nm. Also,
The content of the inert particles B is preferably 0.001 to 1% by weight, more preferably 0.005 to 0.8% by weight, still more preferably 0.01 to 0% by weight based on the weight of the B layer. 0.6% by weight, most preferably 0.01-
It is in the range of 0.2% by weight. Furthermore, the shape of the inert particles B has a volume shape factor (f) of 0.1 to π / 6,
Further, it is preferably 0.2 to π / 6, and particularly preferably 0.4 to π / 6.

If the average particle diameter of the inert particles B is less than 50 nm or the content thereof is less than 0.001% by weight, the winding property and blocking resistance become poor. On the other hand, when the average particle diameter exceeds 1,000 nm or the content exceeds 1% by weight, the electromagnetic conversion characteristics are deteriorated by the shape transfer of the protrusion to the opposite surface or the protrusion of the protrusion from below the A layer. . Examples of preferable types of inert particles B include, for example,
(1) Heat-resistant polymer particles (for example, crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-
Formaldehyde resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, particles of cross-linked polyester, etc.), (2) metal oxide (eg, aluminum trioxide, titanium dioxide, silicon dioxide (silica), magnesium oxide, zinc oxide) , Zirconium oxide, etc.), (3) metal carbonates (eg magnesium carbonate, calcium carbonate etc.), (4) metal sulfates (eg calcium sulfate, barium sulfate etc.), (5) carbon (eg carbon). Examples include fine particles made of inorganic compounds such as black, graphite, diamond, etc.), and (6) clay minerals (eg, kaolin, clay, bentonite, etc.). Of these, crosslinked silicone resin particles, crosslinked polystyrene resin particles, melamine-formaldehyde resin particles, polyamideimide resin particles, other aluminum trioxide (alumina), titanium dioxide, silicon dioxide, zirconium oxide, synthetic calcium carbonate, barium sulfate, diamond. , Or kaolin is preferable. More preferred are fine particles of crosslinked silicone resin particles, crosslinked polystyrene resin particles, and other aluminum trioxide (alumina), titanium dioxide, silicon dioxide, or calcium carbonate.

The inert particles B may be used alone or in combination of two or more. When the inert particles B are composed of two or more kinds of particles, the average particle diameter d of the inert particles B is
As the second and third particles (fine particles) having an average particle size smaller than B, for example, colloidal silica, α, γ, δ, θ
Fine particles such as alumina having a crystal morphology such as are preferably used. Further, among the particle types exemplified as the inert particles B having the average particle size dB, fine particles having a small average particle size can also be used as the second and third particles (fine particles).

The average particle size of the fine particles is preferably 5
˜450 nm, more preferably 10 to 400 nm, particularly preferably 30 to 350 nm. The content of the second and third particles (fine particles) is preferably 0.005 to 1% by weight, and more preferably 0.01% by weight based on the B layer.
˜0.7% by weight, particularly preferably 0.02 to 0.5% by weight.

The laminated polyester layer B in the present invention is
Further, it is preferable to contain 0.001 to 1% by weight of a (partially saponified) ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol. Here, (partially saponified) ester wax includes ester wax and partially saponified ester wax.

The aliphatic monocarboxylic acid has 8 or more carbon atoms, preferably 8 to 34 carbon atoms. When the number of carbon atoms is less than 8, the heat resistance of the obtained ester product is insufficient, and the aliphatic monocarboxylic acid is easily decomposed under the heating conditions when dispersed in the polyester. Appropriate.

Examples of the aliphatic monocarboxylic acid having 8 or more carbon atoms include pelargonic acid, capric acid, undecyl acid,
Lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid,
Nonadecanoic acid, arachidic acid, pehenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, hentriacontanoic acid, petroselinic acid, oleic acid, erucic acid,
Examples thereof include linoleic acid and a mixture containing them.

The alcohol component of the (partially saponified) ester wax is a polyhydric alcohol having two or more hydroxyl groups. Further, from the viewpoint of heat resistance, a polyhydric alcohol having 3 or more hydroxyl groups is preferable. When monoalcohol is used, the heat resistance of the produced (partially saponified) ester wax is insufficient.

As the polyhydric alcohol having two hydroxyl groups, ethylene glycol, propylene glycol,
Trimethylene glycol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol And the like are preferred examples. Preferable examples of the polyhydric alcohol having 3 or more hydroxyl groups include glycerin, erythritol, trait, pentaerythritol, arabite, xylit, tarit, sorbit, and mannite.

Examples of the ester wax obtained from the aliphatic monocarboxylic acid and the polyhydric alcohol include monoesters, diesters and triesters, depending on the number of hydroxyl groups of the polyhydric alcohol. Among these,
From the viewpoint of heat resistance, diester rather than monoester,
Triesters are preferred over diesters. Specific preferred ester waxes include sorbitan tristearate, pentaerythritol tripehenate, glycerin tripalmitate, and polyoxyethylene distearate.

The partially saponified ester wax composed of the aliphatic monocarboxylic acid and the polyhydric alcohol is obtained by partially esterifying the polyhydric alcohol with a higher fatty acid having 8 or more carbon atoms, and then divalent or higher valent metal hydroxide. It is obtained by saponification with. Specific examples include wax E, wax OP, wax O, wax OM, and wax FL (all trade names manufactured by Hoechst KK) obtained by saponifying montanic acid diol ester with calcium hydroxide. The (partially saponified) ester wax is 1
They may be used alone or in combination of two or more.

B of the (partially saponified) ester wax
The amount added to the layer is 0.001 to 1% by weight, preferably 0.003 to 0.5% by weight, more preferably 0.00.
5 to 0.5% by weight, particularly preferably 0.01 to 0.3% by weight. When the content of the (partially saponified) ester wax is less than 0.001% by weight, the improvement of the winding property is insufficient and the blocking improving effect cannot be obtained. On the other hand, if it exceeds 1% by weight, in the film manufacturing process,
On the opposite surface, which comes into contact when wound up on a roll, layer B
A large amount of the bleed-out wax component is transferred to the surface of the, and therefore, for example, the adhesion between the metal vapor deposition layer and the base film is hindered, or dropout is caused.

The surface of the polyester layer B which is not in contact with the polyester A layer preferably has a ten-point average roughness WRzB measured by a non-contact three-dimensional roughness meter of 30 to 300.
nm, more preferably 40 to 250 nm, and particularly preferably 50 to 200 nm. This WRzB is 30
When the thickness is less than or equal to nm, the handleability of the laminated film is poor, and it is difficult to increase the sufficient productivity, and the blocking improving effect tends to be insufficient. On the other hand, when WRzB exceeds 300 nm, the transfer of the shape of the protrusion to the surface on the opposite side where the magnetic layer is provided becomes large, which may impair the electromagnetic conversion characteristics.

The laminated polyester film of the present invention has a magnetic layer on the surface on which the magnetic layer is provided, that is, on the surface of the polyester layer A (the surface not in contact with the polyester layer B), in order to improve various characteristics. Coating layer C
Is preferably provided. This coating layer C has an average particle size of 1
It is preferable to contain 0.5 to 30% by weight of the inert particles C having a volume shape factor of 0.1 to π / 6 and a volume shape factor of 0 to 50 nm. As the resin forming the coating layer C, 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.

In this aqueous polyester resin, the acid component is, for example, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid,
Sebacic acid, dodecane dicarboxylic acid, succinic acid, sodium 5-sulfoisophthalate, potassium 2-sulfoterephthalate, trimellitic acid, trimesic acid, monopotassium trimellitic acid, polyvalent carboxylic acids such as p-hydroxybenzoic acid Consists of one or more, glycol component,
For example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6
A polyester resin mainly composed of one or more polyhydroxy compounds such as hexanediol, 1,4-cyclohexanedimethanol, p-xylylene glycol, dimethylolpropane, and an ethylene oxide adduct of bisphenol A is preferably used. Further, a graft polymer or a block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or two kinds of polymers have a specific physical constitution within a micro particle (IPN (interpenetrating polymer network) type, core shell type, etc.) It may be an acrylic-modified polyester resin formed with. As the water-based polyester resin, a type that dissolves, emulsifies, and finely disperses in water can be freely used, but a type that emulsifies and finely disperses in water is preferable. Further, since these impart hydrophilicity, for example, a sulfonate group, a carboxylate group, a polyether unit or the like may be introduced into the molecule.

The inert particles C contained in the coating layer C are not particularly limited, but are unlikely to settle in the coating liquid,
Those having a relatively low specific gravity are preferable. For example, organic particles such as crosslinked silicone resin, acrylic resin, polystyrene, melamine-formaldehyde resin, aromatic polyamide resin, polyamideimide resin, crosslinked polyester, wholly aromatic polyester, particles made of silicon dioxide (silica), calcium carbonate, etc. Preferred examples include: Among them, crosslinked silicone resin particles, acrylic resin particles, silica particles, core-shell type organic particles (core: crosslinked polystyrene, shell: particles of polymethylmethacrylate, etc.) are particularly preferable.

The average particle diameter dC of the inert particles C is 10 to 10.
The thickness is 50 nm, preferably 12 to 45 nm, more preferably 15 to 40 nm. If this average particle size is less than 10 nm, the slipperiness of the film may be poor,
On the other hand, if the thickness exceeds 50 nm, the electromagnetic conversion characteristics of the magnetic recording medium may become poor, which is not preferable.

The shape of the inert particles C has a volume shape factor (f) represented by the following formula of 0.1 to π / 6, preferably 0.2 to π / 6, and more preferably 0.4 to π. / 6.

[0049]

[Number 1] f = V / D ³ [where, f is the volume shape factor, V is the volume of the particle (mu
m ³ ) and D are the maximum diameters (μm) of the projected surface of the particles. The shape of particles having a volume shape factor (f) of π / 6 is a sphere (a true sphere). That is, the volume shape factor (f)
Of 0.4 to π / 6 is substantially a sphere or a true sphere,
It includes an ellipsoidal sphere such as a rugby ball and is preferable as the inert particles C. Volume shape factor (f) is 0.1
If the particle size is less than 100 μm, for example, flaky particles, the running durability is deteriorated, which is not preferable.

The content of the above-mentioned inert particles C is such that the coating layer C
0.5 to 30% by weight, preferably 2 to 20% by weight, more preferably 3 to 10% by weight, based on (solid content of coating liquid).
Is. If the content is less than 0.5% by weight, the slipperiness of the film may be poor, while if it exceeds 30% by weight, the electromagnetic conversion characteristics of the magnetic recording medium may be poor. Not preferable. The thickness of the coating layer C is preferably 1 to 100 nm, more preferably 2 to 50 n.
m, more preferably 3 to 10 nm, most preferably 3
~ 8 nm.

The laminated polyester film of the present invention has an exposed surface on the side of the polyester layer A (a surface of the polyester layer A which is not in contact with the polyester layer B, and when the coating layer C is provided, it is the same as the polyester layer A of the coating layer C). The surface roughness (WRaA (25)) measured at 25 times with a non-contact three-dimensional roughness meter (the surface on the non-contact side) is 0.1 to 4 nm, preferably 0.2 to 3.5 nm, and more preferably 0.3 ~
3.0 nm, particularly preferably 0.4 to 2.5 nm. Furthermore, the roughness WRaA (2.5) measured with the same roughness meter at a magnification of 2.5 times is 1 to 15 nm, preferably 1.5.
-10 nm, more preferably 2-8 nm. WR
By having aA (25) and WRaA (2.5) in this range at the same time, it is possible to achieve both electromagnetic conversion characteristics and slipperiness. In order to form the exposed surface on the polyester layer A side in such a surface shape, for example, as described above, the polyester layer A does not contain the inert particles, but the polyester layer B contains the specific inert particles B. Just do it.

The total thickness of the laminated polyester film in the present invention is usually 2.5 to 20 μm, preferably 3.0.
10 to 10 μm, and more preferably 4.0 to 10 μm. The thickness constitution of the polyester layer A and the polyester layer B is preferably such that the thickness of the B layer is 1 of the total thickness of the laminated film.
/ 2 or less, more preferably 1/3 or less, particularly preferably 1/4 or less. The lower limit of the thickness ratio of layer B to the total thickness of the laminated film is not particularly limited, but is preferably 1/50 or more, more preferably 1/30 or more, and particularly preferably 1/20 or more.

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

For example, a biaxially oriented polyester film will be described. In the extrusion die or before the die (generally, the former is called a multi-manifold system, the latter is called a feed block system), the (partially saponified) ester wax,
Further, polyester B in which the inactive particles B are finely dispersed and contained and polyester A in which substantially no inactive particles are contained are respectively subjected to high precision filtration, and then laminated and composited in a molten state to obtain the above-mentioned preferable thickness. No laminated structure,
Then, the film is coextruded from the die at a temperature of melting point (Tm) to (Tm + 70) ° C. and then rapidly cooled and solidified by a cooling roll at 40 to 90 ° C. to obtain an unstretched laminated film. Then, the unstretched laminated film was uniaxially (longitudinal or transverse) in a conventional manner (Tg-10) to (Tg + 7).
0) ° C. (however, Tg: glass transition temperature of polyester) at a magnification of 2.5 to 8.0 times, preferably 3.
(Tg) to (Tg + 70) in a direction perpendicular to the stretching direction (when the first stage stretching is the longitudinal direction, the second stage stretching is the transverse direction). 2.5 to 8.0 times magnification at a temperature of .degree. C., preferably 3.0 to 7.
Stretch at a magnification of 5 times. Further, if necessary, it may be stretched again in the machine direction and / or the transverse direction. That is, stretching in two steps, three steps, four steps, or multiple steps may be performed. The total draw ratio is usually 9 times or more, preferably 1
It is 0 to 35 times, more preferably 12 to 30 times.

Further, the biaxially oriented film has (Tg +
Excellent dimensional stability is imparted by heat-fixing crystallization at a temperature of 70) to (Tm-10) ° C, for example, in the case of a polyethylene terephthalate film, at 180 to 250 ° C. At that time, the heat setting time is preferably 1 to 60 seconds.

In the production of the laminated polyester film, the polyesters A and B may optionally contain additives other than the above-mentioned inert particles, such as stabilizers, colorants, and specific resistance adjusting agents for molten polymers. .

The lamination of the coating layer C on the polyester layer A in the present invention is preferably carried out by a method of applying an aqueous coating liquid.

It is preferable that the coating is performed on the surface of the polyester layer A before the final stretching treatment, and after the coating, the film is stretched at least uniaxially. The film is dried before or during this stretching. Among them, the coating is preferably performed on an unstretched laminated film or a longitudinal (uniaxial) stretched laminated film, particularly a longitudinal (uniaxial) stretched laminated film. The coating method is not particularly limited, but examples thereof include a roll coating method and a die coating method.

The solid content concentration of the above-mentioned coating liquid, especially the aqueous coating liquid is
0.2 to 8% by weight, more preferably 0.3 to 6% by weight, especially 0.
It is preferably from 5 to 4% by weight. Then, other components, for example, other surfactants, stabilizers, dispersants, ultraviolet absorbers, thickeners, etc. can be added to the aqueous coating liquid within a range that does not impair the effects of the present invention.

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 set to the longitudinal and lateral directions. And usually 45
00N / mm ² or more and 6000 N / mm ² or more, preferably 4800N / mm ² or more and 6800N / mm ²
Or more, more preferably 5500N / mm ² or more and 8000 N / mm ² or more, particularly preferably 5500N /
mm ² or more and 10,000 N / mm ² or more.

The crystallinity of the polyester resins A and B is preferably 30 to 50% when the polyester is polyethylene terephthalate, and 28 to 38% when the polyester is polyethylene-2,6-naphthalate. If both are below the lower limit, the heat shrinkage rate will be large, while if it is above the upper limit, the abrasion resistance of the film will be deteriorated and white powder tends to be generated when sliding on the surface of the roll or the guide pin.

According to the present invention, a laminated polyester film obtained by laminating the polyester layer B on one surface of the polyester layer A, and a coating layer C on the surface of the polyester layer A (the surface not in contact with the polyester layer B). Also provided is a magnetic recording medium having a base film of each of the laminated polyester films laminated with each other.

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

The laminated polyester film of the present invention comprises iron, cobalt, nickel, chromium or a main component thereof on the surface of the polyester layer A, preferably the coating layer C, by a method such as vacuum deposition, sputtering or ion plating. It is particularly useful as a base film of a magnetic recording medium on which a ferromagnetic metal thin film layer (magnetic layer) made of an alloy or oxide is formed. The thickness of the metal thin film layer is 100-
It is preferably 300 nm.

In the laminated polyester film of the present invention, a protective layer such as diamond-like carbon (DLC) and a fluorine-containing carboxylic acid type lubricating layer are further provided on the surface of the ferromagnetic metal thin film layer according to the purpose, application and need. By providing a back coat layer on the surface of the polyester layer B on the side opposite to the magnetic layer by a known method, the output, S / N, C / N, etc., particularly in the short wavelength region can be sequentially provided. It is preferably used as a vapor-deposited magnetic recording medium for high-density recording, which has excellent electromagnetic conversion characteristics and has little dropout and error rate. This vapor-deposited magnetic recording medium is used for recording analog signals Hi8, digital signal recording digital video cassette recorder (DVC), data 8 mm, DD.
It is extremely useful as a magnetic tape medium for SIV, and is particularly suitable for use in digital video tape applications because excellent results can be obtained. It is also suitable for use as a data storage tape because excellent results can be obtained.

The laminated polyester film of the present invention has a polyester layer A, preferably a coating layer C, on the surface thereof.
Needle-shaped fine magnetic powder (metal powder) containing iron or iron as the main component
Is uniformly dispersed in a binder such as polyvinyl chloride or a vinyl chloride / vinyl acetate copolymer, and coated so that the magnetic layer has a thickness of 1 μm or less, preferably 0.1 to 1 μm. By providing a back coat layer on the surface opposite to the magnetic layer by a known method, the output in the short wavelength region, electromagnetic conversion characteristics such as S / N and C / N are excellent, and dropout and error The metal coated magnetic recording medium for high density recording with a low rate can be obtained. In addition, a non-magnetic layer containing fine titanium oxide particles or the like as a base layer of the metal powder-containing magnetic layer is dispersed on the surface of the polyester layer A or the coating layer C in the same organic binder as the magnetic layer, if necessary. It can also be painted. This metal coated magnetic recording medium is used for analog signal recording 8 mm video, Hi8, β-cam SP, W-
VHS, digital video cassette recorder (DVC) for digital signal recording, data 8 mm, DDSIV,
It is extremely useful as a magnetic tape medium for digital β-cam, D2, D3, SX, etc.

Further, in the laminated film of the present invention, needle-like fine magnetic powder such as iron oxide or chromium oxide or plate-like fine magnetic powder such as barium ferrite is coated on the surface of the polyester layer A, preferably the coating layer C. Evenly dispersed in a binder such as vinyl chloride or vinyl chloride / vinyl acetate copolymer, and the magnetic layer thickness is 1 μm or less, preferably 0.1 to
By applying a back coat layer on the surface of the polyester layer B opposite to the magnetic layer by a known method, the output, S / N, It is possible to obtain an oxide-coated magnetic recording medium for high-density recording, which has excellent electromagnetic conversion characteristics such as C / N and has little dropout and error rate. In addition, if necessary, a non-magnetic layer containing fine titanium oxide particles as an underlayer of the oxide powder-containing magnetic layer is formed on the surface of the polyester layer A or the coating layer C in an organic binder similar to that of the magnetic layer. It can also be dispersed and coated. This oxide-coated magnetic recording medium is useful as an oxide-coated magnetic recording medium for high-density recording such as a QIC for a data streamer for digital signal recording.

The magnetic recording medium of the present invention, as described above,
On the opposite surface of the magnetic layer forming surface, a back coat layer composed of solid fine particles and a binder, which may be formed by applying a solution containing various additives as required, may be provided. Known agents and additives can be used without any particular limitation. The thickness of the back coat layer is preferably 0.3 to 1.5 μm.

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

[0070]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, "parts" and "%" in Examples and Comparative Examples are parts by weight and% by weight, unless otherwise specified. The physical property values and characteristics in the present invention are measured and defined by the following methods.

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

(2) Terminal carboxyl group concentration (eq / 1
0 ⁶ g) A. It measured according to the method of Conix. (Makro
mal. Chem. 26, 226 (1958))

(3) Average particle size (I) of particles (Average particle size:
Shimadzu Corporation “CP-50 type Centrifugure particle size analyzer (Centr)
ifual Particle SizeAnaly
zer) ”. From the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, the particle size "equivalent sphere diameter" corresponding to 50 mass%
And read this value as the average particle size (nm) ("Particle size measurement technology", published by Nikkan Kogyo Shimbun, 1975,
Pages 242-247).

(4) Average particle size (II) of particles (Average particle size:
Particles having an average particle diameter of less than 60 nm that form small protrusions were measured by a light scattering method. That is, Nicomp Instrument Co., Ltd.
ts Inc. ) Product name "NICOMP MODE"
L 270 SUBMICRON PARTICLE
The average particle diameter (nm) is defined as the "equivalent spherical diameter" of the particles at 50% of all the particles obtained by "SIZER".

(5) Volume shape factor (f) A photograph of each particle was taken with a scanning electron microscope at a magnification corresponding to the size used, and an image analysis processor Luzex 500 (manufactured by Nippon Regulator Co., Ltd.) was used. Maximum diameter of projection plane (D) (μm) and volume of particle (V) (μm ³ )
Is calculated and calculated by the following formula.

[0076]

[Formula 2] f = V / D ³

(6) Thickness of Polyester Layers A and B and Thickness of Whole Film The thickness of the whole film was measured at 10 points randomly with a micrometer, and the average value was used. Regarding the layer thickness of the polyester layers A and B, the layer thickness of the thin polyester layer is measured by the method described below, and the layer thickness of the thick polyester layer is obtained by subtracting the layer thicknesses of the coating layer and the thin polyester layer from the total thickness. Ask for. That is, by using a secondary ion mass spectrometer (SIMS), the metal element (M ⁺ ) derived from the highest concentration of particles in the film in the depth range of 5,000 nm from the surface layer excluding the coating layer. The concentration ratio (M ⁺ / C ⁺ ) of the hydrocarbon (C ⁺ ) of polyester and that of polyester is used as the particle concentration, and analysis is performed in the thickness direction from the surface to a depth of 5,000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases.
In the case of the present invention, after the particle concentration once becomes a stable value 1,
There are cases where it rises to a stable value of 2 and cases where it decreases monotonically. Based on this distribution curve, the former has a depth that gives a particle concentration of (stable value 1 + stable value 2) / 2, and the latter has a depth at which the particle concentration becomes 1/2 of the stable value 1. (This depth is deeper than the depth that gives a stable value of 1)
To be the thickness (μm) of the thin polyester layer.
The measurement conditions are as follows.

(A) Measuring device Secondary ion mass spectrometer (SIMS); manufactured by Perkin Elmer Inc., "630"
0 ”(b) Measurement conditions Primary ion species: O ²⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm Analysis area: 30% gate Vacuum degree: 6.0 × 10 ^-9 Torr E- GUNN: 0.5KV-3.0A

If the most abundant particles in the range of 5,000 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 red) is performed while etching from the surface. External spectroscopy), and depending on the particles, the same concentration distribution curve as above is measured by XPS (X-ray photoelectric spectroscopy) or the like to determine the layer thickness (μm).

(7) Thickness of coating layer C A small piece of the film was fixed and molded with an epoxy resin, and an ultrathin section having a thickness of about 600 Å (cut parallel to the film flow direction) was prepared with a microtome.
A transmission electron microscope (Hitachi, Ltd .:
H-800 type), the boundary surface of the coating layer C is searched for, and the thickness (nm) of the coating layer is obtained.

(8) Surface Roughness Non-contact three-dimensional roughness meter manufactured by WRa WYKO Co., Ltd., trade name "T"
OPO-3D ", measurement magnification 25 times or 2.
The measurement was performed under a condition of 5 times to obtain a surface roughness profile (original data). The center plane average roughness (WRa) defined by the following equation is obtained by the surface analysis using the software with a built-in roughness meter.

[0082]

[Equation 3]

Zjk is j in each direction when the measurement direction and the direction orthogonal thereto are divided into M and N, respectively.
It is the height on the three-dimensional roughness chart at the th and kth positions. Ten-point average roughness Using a non-contact three-dimensional roughness meter made by WRzWYKO Co., Ltd., trade name "TOPO-3D", measurement was carried out at a measurement magnification of 25 times to obtain a surface roughness profile (original data). It was From the obtained profile of surface roughness, surface analysis using the software with a built-in roughness meter gave 5 points from the highest peak (Hp) and 5 points from the lowest valley (Hv), and defined by the following formula. 10 point average roughness (WRz).

[0084]

WRz = {(Hp1 + Hp2 + Hp3 + Hp4
+ Hp5)-(Hv1 + Hv2 + Hv3 + Hv4 + Hv
5)} / 5

(9) Young's modulus Using a tensile tester manufactured by Toyo Baldwin Co., Ltd., trade name "Tensilon", in a room controlled at a temperature of 20 ° C. and a humidity of 50%, a length of 300 nm and a width of 12.7.
The mm sample film is pulled at a strain rate of 10% / min and calculated using the first linear part of the tensile stress-strain curve according to the formula:

[0086]

## EQU00005 ## E = .DELTA..sigma ./. DELTA..epsilon. Here, E is Young's modulus, .DELTA..sigma. Is the stress difference due to the original average cross-sectional area between two points on the straight line, and .DELTA..epsilon. Is the strain difference between the same two points.

(10) Winding property After optimizing the winding condition at the slit, the width 600
mm × 12,000m size, 30 rolls, speed 1
The film is slit at a rate of 00 m / min, and a roll having no bumps, protrusions, or wrinkles is regarded as a good product on the film surface after slitting, and the winding property is evaluated according to the following criteria. ⊚: 28 or more non-defective rolls ○: 25 to 27 non-defective rolls ×: 24 or less non-defective rolls

(11) Production of magnetic tape and evaluation of characteristics (electromagnetic conversion characteristics) On the surface of the coating layer C of the laminated polyester film, 0.2 μm of a ferromagnetic thin film containing 100% cobalt was formed by a vacuum deposition method.
Two layers (each layer thickness is about 0.1 μm) are formed to have a thickness of m. A diamond-like carbon (DLC) film and a fluorine-containing carboxylic acid-based lubricating layer are sequentially provided on the surface of the formed ferromagnetic thin film, and a back coat layer is provided on the surface of the polyester layer A by a known method. After that, it was slit into a width of 8 mm and loaded into a commercially available 8 mm video cassette. Then, the characteristics (C / N) of the tape are measured using the following commercially available equipment. (A) Equipment used: 8 mm video tape recorder (manufactured by Sony Corporation, trade name “EDV-6000”) and noise meter (manufactured by Shibasoku Co., Ltd.) (b) Measuring method Recording wavelength 0.5 μm (frequency about 7.4 MHz) Is recorded, the ratio of the values of 6.4 MHz and 7.4 MHz of the reproduced signal is taken as the C / N of the tape, and the C / N of the commercially available 8 mm video deposition tape is taken as 0 dB, and the relative value is evaluated.

(12) Blocking resistance Two sample films were prepared, and the surface on the side of forming the A layer and the surface on the side of forming the B layer were superposed, and at this temperature, 50 ° C. × 70% RH.
In the atmosphere of, first, treated under a load of 1 N / mm ² for 10 hours, then treated under a load of 15 N / mm ² for 100 hours, cut into 5 cm wide strips, and loaded with a tensile tester. The peel strength (mN / 5 cm) of the portion to which is added is evaluated. The evaluation is based on the peel strength and the following criteria. ◯: 0 to 50 Δ: 50 to 100 ×: 100 to breakage

[Example 1] Dimethyl terephthalate 10
0.025 parts of manganese acetate tetrahydrate as a transesterification catalyst was added to a mixture of 0 parts and 70 parts of ethylene glycol, and the transesterification reaction was carried out while gradually raising the internal temperature from 150 ° C. When the transesterification reaction reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and after sufficiently stirring, 0.8 part of trimellitic anhydride and tetrabutyl tetrabutyl were added in 2.5 parts of ethylene glycol. Titanate 0.65
A solution obtained by reacting 1 part (titanium content is 11% by weight).
014 parts were added. Then, the reaction product was transferred to a polymerization reactor and subjected to polycondensation under high temperature vacuum (final internal temperature 295 ° C.) to obtain polyethylene terephthalate (resin A1) for polyester A having an intrinsic viscosity of 0.60.

Further, a transesterification reaction was carried out in the same manner as described above, and when the transesterification reaction reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and the mixture was thoroughly stirred and then mixed. 0.03 parts of antimony oxide was added. After sufficiently distilling water mixed in the system, silicone particles having an average particle diameter of 500 nm and θ-alumina having an average particle diameter of 100 nm were used as a lubricant (inert particles B) in the resin at 0.06% and After 0.2% addition and sufficient stirring, the reaction product was then transferred to a polymerization reactor and polycondensed under high temperature vacuum (final internal temperature 295 ° C) to obtain an intrinsic viscosity of 0.
70 polyethylene terephthalate was obtained. At this time, the residual amount of antimony in this polymer was 250 ppm.

In the obtained polyethylene terephthalate, as a (partially saponified) ester wax consisting of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol, sorbitan tristearate powder having a melting point of 55 ° C. 0 Polyester layer B with an inherent viscosity of 0.69 by adding and dispersing 0.15% and kneading with a biaxial ruder with a vent
To obtain polyethylene terephthalate (resin B1).

The obtained resin A1 and resin B1 were dried at 170 ° C. for 3 hours and then fed to two extruders.
Melting at a melting temperature of 280 to 300 ° C., average opening 11
After highly precise filtration with a μm steel wire filter, a resin layer B was laminated on one surface of the resin layer A using a multi-manifold type co-extrusion die, and was rapidly cooled to obtain an unstretched laminated polyester film with a thickness of 89 μm. .

The obtained unstretched film is preheated, and the film temperature is 100 ° C. between low speed and high speed rolls.
It was stretched 3 times and rapidly cooled to obtain a longitudinally stretched film. Next, an aqueous coating solution (total solid content concentration of 1.0%) having the composition (solid content conversion) shown below was applied to the A layer side of the longitudinally stretched film by a kiss coating method so that the thickness after drying was 8 nm.

Solid content composition of coating liquid Binder: Acrylic modified polyester (manufactured by Takamatsu Yushi Co., Ltd., IN-170-6) 60% Inactive particles C: Acrylic filler (average particle size 30 nm)
(Volume shape factor 0.40) (Nippon Shokubai Co., Ltd., Eposter) 7% Surfactant X: (Nippon Yushi Co., Ltd., Nonion NS-)
208.5) 3% Surfactant Y: (NONION NS-, manufactured by NOF CORPORATION)
240) 30% Then, it is supplied to the stenter, and at 110 ° C., 4.
It was stretched twice. The obtained biaxially stretched film is 220
After heat setting for 4 seconds with hot air at ℃, a laminated biaxially oriented polyester film having a total thickness of 6.4 μm and a polyester layer B thickness of 1.0 μm was obtained. The thickness of the polyester layers A and B of this film was adjusted by the discharge amount of two extruders. Young's modulus of the obtained laminated film lengthwise direction 5000N / mm ^2, was transverse 7000N / mm ^2. Table 1 shows the properties of the obtained laminated film and the properties of the ferromagnetic thin film deposition type magnetic tape used as a support using this film.

[Example 2] Lamination was carried out in the same manner as in Example 1 except that the type, average particle size and addition amount of the inert particles B contained in the polyester layer B were changed as shown in Table 1 (resin B2). A polyester film was obtained. Table 1 shows the characteristics of the obtained film and the characteristics of the ferromagnetic thin film deposition type magnetic tape using the film.

Example 3 Polyester layers A and B were prepared in the same manner as in Example 1 except that the same molar amount of dimethyl 2,6-naphthalenedicarboxylate was used instead of dimethyl terephthalate in polyester layer A and polyester layer B. Polyethylene-2,6-naphthalate (PE
N) (resins A3, B3) were obtained. Intrinsic viscosities were 0.60 for resin A3 and 0.67 for resin B3.

Each of the resins A3 and B3 was heated to 170 ° C.
After drying for 6 hours, the thickness of each layer was adjusted in the same manner as in Example 1 to obtain an unstretched laminated thermoplastic resin film having a thickness of 89 μm.

The obtained unstretched film is preheated, and the film temperature is 135 ° C. between low speed and high speed rolls.
It was stretched 6 times and rapidly cooled to obtain a longitudinally stretched film. Next, on the A layer side of the longitudinally stretched film, inactive particles C are provided with a core-shell filler (core; cross-linked polystyrene, shell; polymethylmethacrylate) (average particle diameter; 30 nm, volume shape factor 0.45) manufactured by JRS Co., Ltd., SX 872
An aqueous coating solution (total solid content concentration 1.0%) having the same composition as in Example 1 was applied in the same manner as in Example 1 except that the content was changed to "1".

Subsequently, it was supplied to a stenter and stretched 5.7 times in the transverse direction at 155 ° C. The obtained biaxially stretched film was heat set with hot air at 200 ° C. for 4 seconds to give a total thickness of 4.4.
A laminated biaxially oriented polyester film having a thickness of μm and a thickness of the thermoplastic resin layer B of 0.6 μm was obtained. The thickness of the thermoplastic resin layers A and B of this film was adjusted by the discharge amounts of the two extruders. Surface roughness WRa measured from the coating layer C side of the surface of the film, 1.2 nm, a Young's modulus of the film machine direction 5500N / mm ^2, was transverse 10,500N / mm ^2. Table 1 shows the other properties of this laminated film and the properties of the ferromagnetic thin film deposition type magnetic tape using this film.

Comparative Example 1 Example 1 except that the intrinsic viscosity of the raw material resin B forming the polyester layer B is 0.53.
A laminated polyester film was obtained in the same manner as in. In the obtained film, the frequency of the inactive particles B falling off from the polyester layer B during film running increased, and a large number of transfer to the opposite surface also occurred. Therefore, when used as a magnetic tape, sufficient electromagnetic conversion characteristics should be obtained. I couldn't. Table 1 shows other characteristics and characteristics of the ferromagnetic thin film deposition type magnetic tape using this film.

[Comparative Examples 2 and 3] A laminated polyester film was prepared in the same manner as in Example 1 except that the type, the average particle size and the addition amount of the inert particles B contained in the polyester layer B were as shown in Table 1. Got The film obtained is B
Transferring the oligomer bleeding out from the layer to the opposite surface was satisfactory, but in the case of Comparative Example 2, B
The degree of shape transfer to the opposite surface of the protrusion on the layer side was strong, and when a magnetic tape was used, sufficient electromagnetic conversion characteristics could not be obtained. In the case of Comparative Example 3, the B layer was too flat and good winding properties could not be obtained. Table 1 shows other characteristics and the characteristics of the ferromagnetic thin film deposition type magnetic tape using this film.
Shown in.

[0103]

[Table 1]

As is clear from Table 1, the laminated polyester film according to the present invention has very flat one side and little oligomer transfer from the opposite side, exhibits excellent electromagnetic conversion characteristics, and has extremely excellent windability. It is good. On the other hand, those which do not satisfy the requirements of the present invention cannot satisfy these characteristics at the same time.

[0105]

According to the present invention, it is possible to obtain a laminated polyester film which is excellent in winding property and processability, and particularly excellent in electromagnetic conversion characteristics when used as a metal vapor deposition thin film type magnetic recording medium.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiko Kosuge             3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture             People DuPont Films Co., Ltd. Sagamihara Research Center             In the center (72) Inventor Hirofumi Murooka             3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture             People DuPont Films Co., Ltd. Sagamihara Research Center             In the center F term (reference) 4F100 AK41A AK41B AK42A AK42B                       BA02 BA03 BA07 BA10C                       CA19B CA23B CC00C DD07B                       GB41 JA06B JK14B JK15                       JK16 JL11 YY00B                 4J002 BC02X BG00X CC18X CF00W                       CF00X CF04W CF05W CF06W                       CF08W CH05Y CL06X CM04X                       CP03X DA016 DA026 DA036                       DE076 DE096 DE106 DE136                       DE146 DE236 DG046 DG056                       DJ016 DJ036 EH047 EH057                       FD01X FD016 GF00 GS01                 5D006 CB01 CB05 CB07 CB08

Claims (9)

[Claims] 1. A polyester layer A and a polyester layer B laminated on one side thereof, wherein the polyester constituting the layer B has an intrinsic viscosity of 0.55 or more and a terminal carboxyl group concentration of 35 eq / 10 ⁶ g. As described above, the exposed surface on the polyester layer A side of the laminated polyester film containing the inert particles (B) and the ester wax composed of the aliphatic monocarboxylic acid having 8 or more carbon atoms and the polyhydric alcohol is not in contact. The centerline roughness WRaA (25) measured with a three-dimensional roughness meter at a magnification of 25 times is in the range of 0.1 to 4 nm, and the centerline roughness WRaA (2 measured with a magnification of 2.5 times with the same roughness meter. .5) is in the range of 1 to 15 nm. 2. The average particle diameter of the inert particles (B) is 50 to 1.
The laminated polyester film according to claim 1, wherein the content of the particles at 000 nm is in the range of 0.001 to 1% by weight based on the weight of the polyester layer B. 3. The ten-point average roughness (WRzB) measured by a non-contact three-dimensional roughness meter on the surface of the polyester layer B which is not in contact with the polyester layer A is in the range of 30 to 300 nm. Laminated polyester film. 4. The laminated polyester film according to claim 1, wherein the polyester constituting the polyester layer A and the polyester layer B is composed of polyethylene terephthalate or polyethylene-2,6-naphthalate. 5. The coating layer C is laminated on the surface of the polyester layer A which is not in contact with the polyester layer B.
~ 4 laminated polyester film. 6. The coating layer C comprises an inert particle C having an average particle diameter of 10 to 50 nm and a volume shape factor of 0.1 to π / 6, which is less than 0.1%.
The laminated polyester film according to claim 5, which contains 5 to 30% by weight. 7. The laminated polyester film according to claim 5, wherein the exposed surface of the laminated polyester film on the side of the polyester layer A forms a ferromagnetic metal thin film layer and is used as a support for a magnetic recording medium. 8. The laminated polyester film for a magnetic recording medium according to claim 7, wherein the magnetic recording medium is a digital recording type magnetic tape. 9. A magnetic recording medium comprising the laminated polyester film for a magnetic recording medium according to claim 1 and a base film, and a magnetic recording layer provided on one surface of the base film.