JP2002025043A - Composite film for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite polyester film for a magnetic recording medium and a magnetic recording medium comprising the film such that generation of oligomers or deformation of film layers in a vapor deposition process are prevented and that the obtained magnetic tape is free from error and excellent in electromagnetic conversion characteristics and has good handling property. SOLUTION: The composite film is obtained by laminating a specified coating layer (A) consisting of inert particles, surfactant and acryl-polyester resin containing acrylic resin synthesized from alkyl methacrylates, epoxy group- containing acrylic monomers and alkyl acrylates on one surface of a polyester film. The surface roughness of the composite film in the coating layer (A) side and the other side measured by using a noncontact three-dimensional surface roughness meter with 2.5 and 25 magnifications is controlled to the respectively specified range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite polyester film for a magnetic recording medium, and more particularly to a ferromagnetic metal thin film type magnetic recording medium excellent in electromagnetic conversion characteristics and running durability, especially for a digital video cassette tape and data storage. The present invention relates to a composite polyester film useful as a base film of a ferromagnetic metal thin film type magnetic recording medium for recording digital data such as a tape.

[0002]

2. Description of the Related Art Consumer digital video tapes put into practical use in 1995 have a metal magnetic thin film of Co provided on a base film by vacuum evaporation, and a diamond-like carbon film coated on the surface thereof. (Evaporation) Despite the flattened surface compared to tape,
It has the advantage of having good durability. The base film is mainly composed of a film having a metal magnetic film-forming surface roughness smaller than that of the Hi8ME base, for example, a polyester film, a polymer blend adhered to at least one surface of the polyester film, and fine particles having a particle size of 5 to 50 nm. A composite polyester film in which a water-soluble polyester copolymer is used as the discontinuous film and fine projections are formed on the discontinuous film by the fine particles (for example, Japanese Patent Publication No. -572
38 gazette).

However, in recent years, tapes have been required to be longer in order to increase the recording capacity, and for this purpose, the base film must be made thinner. In addition, there is a need to increase the speed of vapor deposition in order to increase the productivity of the vapor deposition tape. At the time of vapor deposition, a method of cooling the base film by bringing the nonmagnetic layer side surface of the base film into close contact with a cooling can is usually used, but as the base film becomes thinner and the vapor deposition speed increases, the heat load on the base film during vapor deposition is used. Are getting higher and higher. In a conventional base film, oligomers are generated when exposed to heat, causing an error, or the film is deformed by heat during deposition, resulting in a roughened surface of the deposited layer formed thereon. In addition, there is a problem that the electromagnetic conversion characteristics are deteriorated. As a method of preventing this problem, a technique of flattening the surface of the non-magnetic layer side of the base film to make it more closely adhered to the cooling can is also used, but in this case, the handling property at the time of the base film forming process and vapor deposition is remarkable. There was a problem of inferiority.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, to prevent the generation of oligomers and the deformation of the coating layer in the vapor deposition step, to obtain a magnetic tape with excellent error and electromagnetic conversion characteristics, and An object of the present invention is to provide a composite polyester film for a magnetic recording medium having good handling properties.

[0005]

The present invention has the following arrangement to solve the above-mentioned problem. Thus, according to the present invention, on one side of the polyester film, acrylic-
A coating layer comprising a composition of 40% to 89% by weight of a polyester resin, 1% to 20% by weight of inert particles having an average particle size of 5 nm to 50 nm, and 10% to 50% by weight of a surfactant. A, wherein the acrylic-polyester resin has a weight ratio of an acrylic resin component to a polyester resin component (acrylic resin component / polyester resin component) of 1/9 or more and 5 /
5 or less, and the acrylic resin component is an alkyl methacrylate component of 50 mol% to 95 mol%, an epoxy group-containing acrylic monomer component of 3 mol% to 30 mol%, and an alkyl acrylate component of 3 mol% to 30 mol%
The following composition was heated, and the surface roughness of the composite film measured by a non-contact type three-dimensional surface roughness meter was determined by coating layer A
The value of the surface on the side was measured at a magnification of 2.5 times (WRa _2.5A ) from 0.5 to 3.0 nm and the value measured at a magnification of 25 times (W
Ra _25A ) is in the range of 0.3 to 1.5 nm, and
The value (WRa _2.5B ) of the surface of the composite film measured on a side different from the coating layer A side (B side) at a magnification of 2.5 times is 2.0 to 2.0.
The value (WR) measured at 5.0 nm and 25 times magnification.
a _25B ) is in the range of 0.6 to 2.5 nm.

According to the present invention, among the above composite films for magnetic recording media, the polyester film is made of polyethylene terephthalate or polyethylene-2,6.
A composite film for a magnetic recording medium which is a film comprising naphthalene dicarboxylate, a composite film for a magnetic recording medium in which the thickness of a polyester film is less than 7 μm, or a composite film for a magnetic recording medium used for a digital recording type magnetic tape; Is done.

Further, according to the present invention, there is provided a magnetic recording medium in which a magnetic layer, particularly a ferromagnetic metal thin film is provided on the coating layer A side of the above-mentioned composite film for a magnetic recording medium.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The composite film for a magnetic recording medium according to the present invention comprises a polyester film as a base and a coating layer A laminated on one side thereof. The surface shapes of the polyester film, the coating layer A, and the composite film in the present invention and the method for producing them are described below.

First, a polyester film as a base constituting the composite film for a magnetic recording medium of the present invention will be described. In the present invention, the polymer constituting the polyester film is a polyester that becomes a high-strength film by molecular orientation. Among them, polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are preferred. This polyethylene terephthalate,
In the polyethylene-2,6-naphthalenedicarboxylate, 80 mol% or more of all the repeating units consist of ethylene terephthalate and ethylene-2,6-naphthalenedicarboxylate.

Examples of the copolymer component other than the ethylene terephthalate unit or the ethylene naphthalene dicarboxylate unit include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylene glycol and 1,4-cyclohexanedimethanol. , Adipic acid, sebacic acid, terephthalic acid (in case of polyethylene-2,6-naphthalenedicarboxylate), phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, 2,6-
Examples include naphthalenedicarboxylic acid (in the case of polyethylene terephthalate), dicarboxylic acid components such as 2,7-naphthalenedicarboxylic acid, polyfunctional acid components such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid. The polyester may be blended with another resin. For example, 5% by weight of at least one of an alkali metal salt derivative of a sulfonic acid which is not reactive with the polyester or a polyalkylene glycol which is substantially insoluble in the polyester. And those blended in a range not exceeding the above.

It is preferable that the polyester in the present invention does not substantially contain inert particles, or even if it does, it is 0.5% by weight or less based on the weight of the polyester. Examples of the inert particles include inert inorganic particles or organic particles represented by calcium carbonate, aluminum oxide, silicon oxide, and titanium oxide. When the content of the inert particles exceeds 0.5% by weight,
When formed into a magnetic tape, the electromagnetic conversion characteristics are poor. The average particle size of the inert particles is preferably from 30 to 300 nm, more preferably from 50 to 200 nm. When the particle size is less than 30 nm, the film tends to aggregate, and as a result, the surface of the film becomes rough and the electromagnetic conversion characteristics are easily reduced. On the other hand, when it exceeds 300 nm, the electromagnetic conversion characteristics are easily reduced.

The polyester film in the present invention may have a single-layer structure or a multilayer structure of two or more layers by a coextrusion method or the like. In the case of a multi-layer structure, the polyester of the surface layer on the side on which the magnetic layer is laminated contains substantially no inert particles or 0.5% by weight even if it does.
Is preferably within a range not exceeding. Incidentally, the polyester film in the present invention is preferably a biaxially oriented film, the thickness of which is less than 7 μm, particularly 2 μm
A thickness of less than 7 μm is preferable for a large-capacity magnetic recording medium. Further, the polyester may have a film-forming property improver (for example, an alkali metal salt compound, a quaternary phosphonium salt compound of sulfonic acid, etc.), a heat stabilizer (for example, phosphoric acid, phosphorous acid, derivatives thereof, etc.) An inhibitor (for example, a hindered phenol compound or the like) or other additives,
You may contain as needed within the range which does not impair the objective of this invention. The intrinsic viscosity of the above polyester (orthochlorophenol, 25 ° C, using an Oswald viscometer)
Is preferably 0.4 to 0.9.

Next, the film layer A constituting the composite film for a magnetic recording medium of the present invention will be described. The coating layer A is an acrylic-polyester resin having an average particle size of 5 nm or more and 50 or more.
It is composed of a composition of inert particles having a size of not more than nm and a surfactant. The proportion of the acrylic-polyester resin in the coating layer A must be 40% by weight or more and 89% by weight or less, preferably 50% by weight or more and 75% by weight or less.
When this proportion is less than 40% by weight, the adhesion to the polyester film is reduced and the coating layer A is easily shaved,
On the other hand, when the content exceeds 89% by weight, the ratio of the inert particles and the surface active agent is reduced, which impairs the tape properties and the coatability of the coating layer A. The adhesiveness between the coating layer A and the polyester film is ensured by the polyester resin component in the acrylic-polyester resin, and the abrasion resistance of the coating layer A and the oligomer suppressing effect of the base film are ensured by the acrylic resin component.

The acrylic-polyester resin (1)
Is used to mean an acrylic-modified polyester resin or a polyester-modified acrylic resin, in which an acrylic resin component and a polyester resin component are bonded to each other, and this bonding includes, for example, a graft type and a block type. . Such an acrylic-polyester resin is, for example, a radical initiator is added to both ends of a polyester resin component to cause polymerization of an acrylic monomer, or a radical initiator is added to a side chain of a polyester resin component to form an acrylic monomer. Or by adding a hydroxyl group to the side chain of the acrylic resin component and reacting it with a polyester resin component having an isocyanate group or a carboxyl group at the terminal.

The weight ratio of the polyester resin component / acryl resin component of the acrylic-polyester resin (1) is 1
/ 9 or more and 5/5 or less, preferably 2/8 or more and 4/6 or less. If this ratio is less than 1/9, the adhesion of the coating layer A to the polyester film is insufficient, while if it exceeds 5/5, the abrasion resistance of the coating layer A and the effect of suppressing oligomers of the base film are poor.

The polyester resin component constituting the acrylic-polyester resin can be produced by the following reaction between a polybasic acid or an ester-forming derivative thereof and a polyol or an ester-forming derivative thereof. That is,
Polybasic acid components include terephthalic acid, isophthalic acid,
Phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid, 5-sodium sulfoisophthalic acid and the like are preferred. Can be One or more of these acid components can be used. In addition, a hydroxycarboxylic acid such as an unsaturated polybasic acid component such as maleic acid, itaconic acid and p-hydroxybenzoic acid may be used in a small amount. Further, as the polyol component, ethylene glycol,
1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,
4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, poly (ethylene oxide)
Glycol and poly (tetramethylene oxide) glycol are preferred. One or more of these monomers can be used.

The acrylic resin component constituting the acrylic-polyester resin is composed of an alkyl methacrylate component of 50 mol% to 95 mol%, an epoxy group-containing acrylic monomer component of 3 mol% to 30 mol% and an alkyl acrylate component of 3 mol% or less. The composition comprising at least 30 mol% and not more than 30 mol% is reacted by heating. If the proportion of the alkyl methacrylate component is less than 50 mol%, polymerization of the acrylic-polyester resin is difficult,
On the other hand, if it exceeds 96 mol%, the proportion of the epoxy group-containing acrylic monomer component or the alkyl acrylate component is reduced as a result, and the abrasion and flatness are deteriorated. A preferable ratio of the alkyl methacrylate component is 60 mol% or more and 90 mol% or less. Examples of the alkyl group in the alkyl methacrylate component include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,
Isobutyl group, t-butyl group, 2-ethylhexyl group,
Examples thereof include a cyclohexyl group.

If the proportion of the epoxy group-containing acrylic monomer component is less than 3 mol%, the crosslink density of the resin is reduced, and the abrasion resistance of the coating layer A is deteriorated. The vapor deposition layer formed thereon is deformed and roughened, and when used as a magnetic recording medium, the electromagnetic conversion characteristics deteriorate. On the other hand, if the proportion of the epoxy group-containing acrylic monomer component exceeds 30 mol%, the background resin portion between the filler protrusions of the coating layer A becomes coarse, and the electromagnetic conversion characteristics deteriorate when used as a magnetic recording medium. The preferred proportion of the epoxy group-containing acrylic monomer component is 7 mol% or more and 25 mol% or less. Examples of the epoxy group-containing acrylic monomer include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether and the like.

The ratio of the alkyl acrylate component is as follows:
If the amount is less than 3 mol%, the background resin portion between the filler protrusions on the surface of the film layer A becomes coarse and the electromagnetic conversion characteristics deteriorate when used as a magnetic recording medium. Of the coating layer A is deformed by heat at the time of vapor deposition, and as a result, the surface of the vapor deposited layer formed thereon is roughened, and the electromagnetic conversion characteristics are deteriorated when used as a magnetic recording medium. . A preferable ratio of the alkyl acrylate component is 4 mol% or more and 20 mol% or less. As the alkyl group of the alkyl acrylate component, a methyl group,
Examples include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, and a cyclohexyl group.

The coating layer A in the present invention contains inert particles. The material of the inert particles includes polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, and methyl methacrylate copolymer crosslinked product. And any of organic substances such as polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine, and silicone; and inorganic substances such as silica, alumina, titanium dioxide, kaolin, calcium carbonate, talc, and graphite. Alternatively, core-shell particles having a multilayer structure composed of substances having different properties inside and outside may be used.
The inert particles preferably have a volume shape factor (f) defined by the following formula of 0.1 to π / 6, and more preferably 0.4 to π / 6.
A substantially sphere of π / 6 or a rugby ball-shaped elliptical sphere is preferred. The volume shape count (f) is less than 0.1,
For example, in the case of a flaky particle, when it is used as a magnetic recording medium, the electromagnetic conversion characteristics are likely to deteriorate.

[0021]

(Equation 1) Here, V represents the volume of the inert particles, and d represents the average particle size.

The average particle size of the inert particles is 5 to 50 nm.
And preferably 10 to 40 nm.
If the particle size is less than 5 nm, the running durability with the head is insufficient when the magnetic recording medium is used. Conversion characteristics deteriorate. The proportion of the inert particles in the coating layer A must be 1% by weight or more and 20% by weight or less, preferably 3% by weight or more and 10% by weight.
It is as follows. When the proportion is less than 1% by weight, the running durability with the head is insufficient when the magnetic recording medium is used. On the other hand, when the proportion exceeds 20% by weight, particles easily fall off from the coating layer A.

As the surfactant constituting the coating layer A in the present invention, any of an anionic type, a cationic type and a non-ionic type may be used, and among them, the non-ionic type is preferable. Examples of the nonionic surfactant include an ester type, an ether type, and an alkylphenol type. Specific examples of such a surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene monostearate, sorbitan stearate, and polyoxyethylene sorbitan monostearate.

The ratio of the surfactant in the coating layer A is 1
It must be 0% by weight or more and 50% by weight or less, preferably 15% by weight or more and 40% by weight or less. If this ratio is less than 10% by weight, the coatability deteriorates and the running durability of the magnetic recording medium with the head becomes insufficient.
If it exceeds 0% by weight, the particles are likely to fall off from the coating layer A. The coating layer A in the present invention may contain other components as desired, such as a stabilizer, a dispersant, a UV absorber, a thickener, and a release agent, as long as the effects of the present invention are not impaired. Good. The thickness of the coating layer A in the present invention may be determined in consideration of the composition of the binder resin, the roughness of the coating surface, the durability of the coating, etc., and is 0.5 to 30 nm, more preferably 2 to 10 nm.
It is preferred that

Further, according to the present invention, there is provided a composite recording medium for a magnetic recording medium.
The shape of the surface of the lum will be described. In the present invention,
The surface on the coating layer A side of the composite film is a non-contact three-dimensional surface
Surface roughness (WR) measured at 2.5 times magnification using a roughness meter
a_2.5A) Is 0.5 to 3.0 nm, preferably 0.5 to 3.0 nm.
Surface roughness (WRa) measured at 2.0 nm and 25 times magnification
_25A) Is from 0.3 to 1.5 nm, preferably from 0.4 to 1.
5 nm. This WRa_2.5AOr WRa_25AThroat
Even if it is lower than the lower limit, the running durability of magnetic tape
Lack of durability, while either of them exceeds the upper limit
And the output when using a magnetic tape is insufficient.

The surface of the composite film of the present invention on the side different from the coating layer A side (B side) has a surface roughness measured at a magnification of 2.5 times using a non-contact type three-dimensional surface roughness meter. (WRa _2.5B ) is 2.0 to 5.0 nm, preferably 2.
Surface roughness (W at 5 to 4.0 nm, measured at 25 × magnification)
Ra _25B ) is 0.6 to 2.5 nm, preferably 0.8 to 2.5 nm.
It has a characteristic of 2.0 nm. This WRa2.5B, WR
a If either of _25B is less than the lower limit, the coefficient of friction increases and the handleability of the film deteriorates, while if any of these exceeds the upper limit, the B side of the composite film when the film is wound on a roll Is transferred to the coating layer A side or the shape is transferred to roughen the surface of the coating layer A. In addition, the surface on the side of the coating layer A may be hereinafter referred to as the A side and the surface on the side different from the side of the coating layer A may be referred to as the B side.

In the present invention, the polyester film
The surface (B side) on the magnetic layer side is WRa_{2. 5B}Is WRa_2.5AThan
Larger is preferred. 2.5 measured at 2.5x magnification
Only the surface on the B side in a wide area of mm × 1.9mm
The method of roughening is not particularly limited, but polyester
When forming a film, the melt-extruded polyester
Cooling and solidifying on a casting drum with irregularities, and
The surface of the composite film in contact with the casting drum
Is a method of forming an uneven shape only on the B side by setting
preferable.

The surface (side B) of the polyester film of the present invention on the non-magnetic layer side is WRa _25B on WRa _25A.
It is preferably larger. 2 measured at 25x magnification
B in a narrow area of 46.6 μm × 187.5 μm
The method of roughening only the surface is not particularly limited, but a method of providing a coating layer B that forms a rougher surface than the coating layer A on the B side of the polyester film, a polyester film containing no fine particles and a polyester film containing fine particles A method in which the former is a coating layer A side and the latter is a B side, or two kinds of polyester films having different types, average particle diameters or contents of fine particles are laminated together,
For example, a method in which the surface roughness is set to the B side and the non-surface roughness is set to the A side can be exemplified.

The method for providing the coating layer B may be performed according to the method for providing the coating layer A. At that time, the average particle size is 10 to 2
5 nm (e.g., polyethylene particles, polyacrylic particles, silicone resin particles, calcium carbonate, silica, alumina, etc.)
To 40% by weight, more preferably 10 to 30% by weight,
Alternatively, a part of the binder resin (5 to 50% by weight, more preferably 10 to 40% by weight based on the weight of the coating layer B) may be spreadable with polyvinyl alcohol, gelatin, cellulose or a sulfonic acid group-containing styrene copolymer. It is preferable to roughen the surface using a resin having poor (stretchability). As the binder resin, a conventionally known binder resin can be used, and examples thereof include water-soluble (or water-dispersible) polyester, polyurethane, and acrylic resin. The thickness of the coating layer B is 3 to
It is preferably 50 nm, more preferably 5 to 30 nm.

As a method for laminating the polyester film, a co-extrusion method is preferably used. At this time, the thickness of the polyester film forming the side B of the laminated polyester film is preferably 1/2 to 1/10 of the thickness of the entire laminated polyester film. The fine particles used for the polyester film forming the B side of the laminated polyester film can be exemplified by calcium carbonate, silica, alumina, polystyrene particles or silicone resin particles, and the average particle size thereof is preferably 80 to 800 nm, Preferably 100 to 7
00 nm, and the amount of addition is preferably 0.0
It is 5 to 1.0% by weight, more preferably 0.08 to 0.8% by weight.

Further, a method for producing the composite film for a magnetic recording medium of the present invention will be described. The composite polyester film of the present invention is melt-molded, biaxially stretched, and in a normal plastic film manufacturing process including heat setting, a coating liquid for forming a coating layer A on one surface of the polyester film after stretching in one direction. After applying and drying, it can be manufactured by stretching in a perpendicular direction and heat setting.

For example, in the case of a single-layer film, polyester is extruded from a die at a melting point of Tm.degree. C. to (Tm + 70) .degree. C. into a film, and then closely adhered to a cooling drum to be rapidly cooled to obtain an unstretched film. Thereafter, the unstretched film is uniaxially (longitudinal or transverse) (Tg-1).
0) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester) at a magnification of 2.5 to 7.0 times, preferably 3.0 to 6.5 times. A coating liquid for forming the layer A is applied to one side of the film, and then Tg to (Tg +
70) The film is stretched at a temperature of ° C at a magnification of 2.5 to 7.0 times, preferably 3.0 to 6.5 times. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. That is, stretching may be performed in two steps, three steps, four steps, or more steps. The total stretching ratio is usually 9 times or more, preferably 12 to 32 times, more preferably 15 to
It is 30 times. Subsequently, the biaxially oriented film is heated to a temperature of (Tg + 70) to (Tm-10) ° C., for example, 18 ° C.
Excellent dimensional stability is provided by heat set crystallization at 0-250 ° C. The heat fixing time is preferably 1 to 60 seconds. In addition, a known method can be applied as the coating method. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife method, an impregnation method, a curtain coating method, or the like can be used alone or in combination. The solid content concentration of the coating liquid depends on the coating method, but is preferably 20% by weight or less, more preferably 15% by weight or less, and particularly preferably 10% by weight or less. Also. The lower limit concentration is preferably 0.5% by weight, more preferably 1% by weight.

The composite polyester film of the present invention is suitable as a polyester film for a magnetic recording medium comprising a ferromagnetic metal thin film layer, particularly when used for digital video tape applications, because excellent effects can be obtained. Also,
Excellent effects can be obtained for data storage tape applications, which is preferable.

Finally, a magnetic recording medium using the above-described composite polyester film will be described. The magnetic recording medium of the present invention is characterized in that a magnetic layer, in particular, a ferromagnetic metal thin film layer is provided on the coating layer A of the composite polyester film. This metal thin film layer can be formed by a known technique, and is not particularly limited. Iron, cobalt, nickel,
Those made of a ferromagnetic material of chromium or an alloy thereof are preferred. The thickness of the metal thin film layer is preferably from 100 to 300 nm.

In the magnetic recording medium of the present invention, a solution composed of solid fine particles and a binder and, if necessary, various additives is applied to the B side of the polyester film, and the solution is cured to form a back coat layer. May be formed. Known solid fine particles, binders and additives can be used and are not particularly limited. The thickness of the back coat layer is 0.3 to 1.5
μm is preferred.

[Method for Measuring and Evaluating Characteristics] The method for measuring and evaluating the film characteristics in the present invention is as follows. (1) Average particle size of particles The average spherical particle size is defined as the equivalent spherical diameter of the particles at 50% by weight of all the particles determined by the light scattering method.

(2) Volume Shape Factor A photograph of each particle is taken with a scanning electron microscope at a magnification corresponding to the size of the particle, and the maximum diameter of the projection surface and the volume of the particle are calculated using an image analysis processor Luzex. Then, it is calculated by the following equation.

[0038]

(Equation 2) Where f is the volume shape factor, V is the volume of the particles (μm ³ ),
d represents the maximum diameter (μm) of the projection surface.

(3) Surface roughness of film WRa _2.5 non-contact three-dimensional surface roughness meter (NT-20 manufactured by WYKO)
00), measuring magnification 2.5 times, measuring area 2.5 mm
Under the conditions of × 1.9 mm (= 4.75 mm ² ), the surface roughness of the composite film was measured on the A side and the B side with a measurement number (n) of 10 or more, and the surface built into the roughness meter was measured. The center surface average roughness (WRa _2.5 ) is obtained by analysis software.

[0040]

(Equation 3)

Zjk is a two-dimensional roughness chart at the j-th and k-th positions in each direction when the measuring method (2.5 mm) and the method perpendicular thereto (1.9 mm) are divided into m and n, respectively. Height.

WRa ₂₅ non-contact type three-dimensional surface roughness meter (manufactured by WYKO: NT-20)
00), measurement magnification 25 times, measurement area 246.6 μm
Under the conditions of mx187.5 μm (= 0.0462 mm ² ), the surface roughness of the composite film was measured on the A side and the B side with a measurement number (n) of 10 or more, and the composite film was incorporated in the roughness meter. The average roughness of the center plane (W
Ra ₂₅ ) is determined.

[0043]

(Equation 4)

Zjk is measured on the two-dimensional roughness chart at the j-th and k-th positions in each direction when the measuring method (246.6 μm) and the method orthogonal thereto (187.5 μm) are divided into m and n, respectively. Height.

(4) Film Layer Thickness A small piece of the film was fixed and molded with epoxy resin, and an ultrathin section (cut in parallel to the film flow direction) of about 60 nm thickness was prepared with a microtome. Observation with an equivalent electron microscope (H-800 manufactured by Hitachi, Ltd.)
The layer thickness is determined from the boundary line of the layer.

(5) Coefficient of friction of the film A fixed glass plate is placed under the two superposed films, and the film on the lower side of the superposed film (the film in contact with the glass) is rolled at a constant speed. (10 cm / min), and a detector is fixed to one end of the upper film (the side opposite to the direction in which the lower film is pulled) to detect the tension (F) between the films. The thread on the upper film used at that time is
The lower area is 50 cm 2 (80 mm × 62.5 mm), the surface in contact with the film is neoprene rubber having a hardness of 80 °, and its weight (W) is 1.2 kg.

The coefficient of static friction is calculated by the following equation, and is evaluated according to the following criteria.

[0048]

(Equation 5)

Evaluation criteria: ：: less than 0.4 Δ: 0.4 or more and less than 0.6 ×: 0.6 or more

(6) Spots of application A dyeing solution having the following composition (temperature: 50
C.) for 10 minutes, washed with water, and then observed with silent observation. <Staining solution> Methylene blue: 0.5% by weight Benzyl alcohol: 1.5% by weight Kayakaran red: 0.1% by weight Rhodamine B: 0.1% by weight Deionized water: 97.8% by weight

(7) Winding property The winding tension is 10 kg / m and the winding contact pressure is 1 by a slitter.
Under a condition of 40 kg / m, a winding speed of 100 m / min, an oscillation width of 100 mm, and an oscillation speed of 10 mm / min, ten polyester film rolls having a width of 500 mm and a length of 9000 mm are wound up, and after standing for 24 hours, the rolls are inspected. A roll having no wrinkles is evaluated as a good product according to the following criteria.

(8) Production of Magnetic Tape and Evaluation of Characteristics A 110-nm-thick cobalt-oxygen thin film was formed on the outside of the surface of the polyester film on which the coating layer A was formed by vacuum evaporation, followed by sputtering on the cobalt-oxygen thin-film layer. A diamond-like carbon is formed to a thickness of 10 nm by the method, a fluorine-containing carboxylic acid-based lubricant is further provided sequentially, and then a back coat layer made of carbon black, polyurethane, and silicone is provided on the opposite surface to a thickness of 500 nm, and a width of 8 mm is set by a slitter. Slit to 6.35 mm and wind up on a commercially available reel to make a magnetic tape. The electromagnetic conversion characteristics were determined by using a commercially available Hi8 type 8 mm video tape recorder to measure the video S / N ratio, and using a commercially available camera-integrated digital video tape recorder to drop out (D).
O) Find the number. For the measurement of S / N, a signal was supplied from a TV test signal generator, a video noise meter was used, and a commercially available standard Hi8ME tape was measured at zero decibel (d).
Comparative study will be made as B). ○: +2 dB or more compared to a commercial tape △: -2 dB or more to less than +2 dB compared to a commercially available tape ×: Less than -2 dB compared to a commercially available tape The number of DOs was measured by recording a 6.35 mm tape created with a commercially available digital video tape recorder with camera. Thereafter, the reproduction is performed for one minute, and the number of block mosaics appearing on the screen is counted.

The running durability is determined by measuring the S / N after repeating recording and reproduction 500 times at 40 ° C. and 80% RH, and determining the deviation from the initial value. ：: +0.0 dB or more with respect to the initial value Δ: -1.0 dB or more to less than +0.0 dB with respect to the initial value ×: less than -1.0 dB with respect to the initial value

[0054]

The present invention will be further described below with reference to examples.

Example 1 Pellets of polyethylene-2,6-naphthalenedicarboxylate containing substantially no inert particles were dried at 170 ° C. for 6 hours and then supplied to an extruder and melted at 305 ° C. . The molten polymer is filtered by a known method, extruded from an extruder into a sheet,
This was adhered to a casting drum having a surface crack of 60 ° C. with a fine crack formed on the surface using an antistatic application casting method such that the surface in contact with the drum was the non-magnetic surface B side. Then, it was cooled and solidified to prepare an unstretched film. The unstretched film thus obtained is
Preheat at 0 ° C, 15mm between low and high speed rolls
The film was heated by an IR heater at 900 ° C. from above and stretched 3.6 times in the machine direction, and subsequently, an aqueous solution having the following composition was applied to each film.

Film layer A (thickness (after drying): 4.8 nm) (a) Acrylic-polyester resin: 75% by weight Polyester resin part: terephthalic acid (70 mol%)
Isophthalic acid (18 mol%), 5-sodium sulfoisophthalic acid (12 mol%) / ethylene glycol (92 mol%)
Mol%), diethylene glycol (8 mol%)-Acrylic resin part: methyl methacrylate (80 mol%), glycidyl methacrylate (15 mol%), n-
Butyl acrylate (5 mol%) Molar ratio of polyester resin part / acryl resin part = 3/7 (b) Acrylic resin particles (average particle size: 15 nm): 5% by weight (c) Surfactant Nonion NS-24 manufactured by NOF Corporation
0: 20% by weight The composition of the acryl-polyester resin of the coating layer A is shown in Table 1, and the composition of the coating layer A is shown in Table 2.

Film layer B (thickness (after drying): 15 nm) (d) Copolyester resin: 60% by weight Terephthalic acid (97% by mole), isophthalic acid (1% by mole), 5-sodium sulfoisophthalic acid ( 2 mol%)
/ Ethylene glycol (60 mol%), diethylene glycol (8 mol%) (e) Silica particles (average particle size 60 nm): 10% by weight (f) Hydroxypropylmethylcellulose: 20% by weight (g) NONION NS-208 manufactured by NOF Corporation .5: 10% by weight

Subsequently, the mixture was supplied to a stenter, stretched 5.0 times in the transverse direction at 150 ° C., and further stretched to 1.12 at 200 ° C.
The film was heat-treated while being stretched twice to obtain a biaxially oriented film having a thickness of 4.7 μm. On the polyester film surface A (surface of the coating layer A), a cobalt-oxygen thin film
It was formed with a thickness of 10 nm. Next, a diamond-like carbon having a thickness of 10 nm was formed on the cobalt-oxygen thin film layer by a sputtering method. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone was provided with a thickness of 500 nm, slit to a width of 8 mm with a slitter, and wound on a reel to produce a magnetic tape. Table 3 shows the properties of the obtained polyester film and magnetic tape.
Shown in

[Examples 2 to 4, Comparative Examples 1 to 7] Example 1
, The same operation was repeated except that the type and ratio of the coating agent on the side A were changed as shown in Tables 1 and 2. Table 3 shows the properties of the obtained polyester film and magnetic tape.

[Example 5] In the production of the base film of Example 1, the polyethylene-2,6-naphthalenedicarboxylate was changed to polyethylene terephthalate, the drying time of the pellets was 3 hours, and the melt extrusion temperature was 295 ° C. And the longitudinal preheating temperature and the magnification were 8
0 ° C. and 3.0 times, the transverse stretching preheating temperature and the transverse stretching were 120 ° C. and 4.2 times, respectively, the heat treatment temperature was 210 ° C., and the thickness of the base film was 6.4 μm.
The same operation was repeated except for changing to. Table 3 shows the properties of the obtained polyester film and magnetic tape.

Example 6 The procedure of Example 1 was repeated except that polyethylene-2,6-naphthalenedicarboxylate contained 0.03% by weight of spherical silica having an average particle size of 60 nm. The operation was repeated. Table 3 shows the properties of the obtained polyester film and magnetic tape.

[Example 7] In the production of the base film of Example 1, the sheet extruded from the extruder was made of polyethylene-2,6-naphthalenedicarboxylate containing substantially no inert particles. The ratio of the thickness of A to the raw material B containing 0.3% by weight of silica having an average particle diameter of 300 nm in polyethylene-2,6-naphthalenedicarboxylate containing substantially no inert particles is 5:
The same operation was repeated except that the sheet material was changed to a sheet material by co-extrusion. Table 3 shows the properties of the obtained polyester film and magnetic tape.

[Comparative Example 8] In the production of the base film of Example 1, the same operation was repeated except that the thickness of the coating layer B was changed to 3 nm. Table 3 shows the properties of the obtained polyester film and magnetic tape.

[Comparative Example 9] In the production of the base film of Example 1, the same operation was repeated except that a flat casting drum having no crack on the surface was used.
Table 3 shows the properties of the obtained polyester film and magnetic tape.

[0065]

[Table 1]

Table 1 shows the composition of the acrylic-polyester resin in the coating layer A.

[0067]

[Table 2]

Table 2 shows the composition of the coating layer A. In Table 2, x and y indicate the type of the surfactant, respectively, x is Nonion NS-240 (manufactured by NOF Corporation), and y is Nonipol. Soft SS-7 (manufactured by Sanyo Chemical Co., Ltd.).

[0069]

[Table 3]

As is evident from Table 3, the composite polyester film of the present invention has no coating unevenness, has excellent handling properties, and when used as a magnetic tape, has an electromagnetic conversion characteristic and a D.
The resulting tape has excellent O characteristics and running durability.

[0071]

According to the present invention, it is possible to prevent the generation of oligomers and the deformation of the coating layer in the vapor deposition process, and to obtain a magnetic recording medium which has excellent error and electromagnetic conversion characteristics and excellent handling properties. A composite polyester film can be provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (reference) // C08L 67:02 C08L 67:02 F term (reference) 4F006 AA35 AA55 AA56 AB35 AB43 AB52 AB56 AB69 AB72 AB73 AB74 AB76 BA01 BA04 BA06 CA02 DA04 EA05 EA06 4F100 AA20H AA37 AA37H AB15 AK25B AK25H AK25J AK41B AK42A AK42J AK51 AK52 AL01 AL05B AR00C BA02 BA03 BA05 BA07 BA10A BA10C CA18B CA23B DD07 EHYB00 J05Y06 J03

Claims (5)

[Claims] 1. One side of a polyester film, 40% by weight or more and 89% by weight or less of an acryl-polyester resin,
1% by weight to 20% by weight of inert particles having an average particle size of 5 nm to 50 nm and 10% by weight to 5% by weight of a surfactant
An acrylic-polyester resin having a weight ratio of an acrylic resin component to a polyester resin component (acrylic resin component / polyester resin component) of 1/0. 9 to 5/5 and the acrylic resin component is an alkyl methacrylate component of 50 mol% to 95 mol%, an epoxy group-containing acrylic monomer component of 3 mol% to 30 mol% and an alkyl acrylate component of 3 mol% to 30 mol % Or less of the composition, and the surface roughness of the composite film measured by a non-contact type three-dimensional surface roughness meter was measured by measuring the surface of the coating layer A side at a magnification of 2.5 times (WRa _{2.5 A} ) is 0.5 to 3.0 nm, the value (WRa _25A ) measured at a magnification of 25 times is in the range of 0.3 to 1.5 nm, and the composite film is Of the surface (side B) different from the side of the coating layer A at a magnification of 2.5 times (WRa)
_2.5B ) is a composite film for a magnetic recording medium, wherein the value (WRa _25B ) measured at _2.0 to 5.0 nm and a magnification of 25 is in the range of 0.6 to 2.5 nm. 2. The composite film for a magnetic recording medium according to claim 1, wherein the polyester film is a film composed of polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate. 3. The composite film for a magnetic recording medium according to claim 1, wherein the thickness of the polyester film is less than 7 μm. 4. The composite film for a magnetic recording medium according to claim 1, which is used for a digital recording type magnetic tape. 5. A magnetic recording medium, wherein a magnetic layer is provided on the film layer A side of the composite film for a magnetic recording medium according to claim 1.