JP2954792B2 - Polyester film for magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a magnetic recording medium, and more particularly to the running property of a magnetic layer .
The present invention relates to a polyester film useful for manufacturing a magnetic recording medium having excellent electromagnetic conversion characteristics and storage durability, particularly a magnetic recording medium capable of recording for a long time.

[0002]

2. Description of the Related Art As a high-density magnetic recording medium, a ferromagnetic metal thin film magnetic recording medium in which a ferromagnetic metal thin film is formed on a nonmagnetic support by a physical deposition method such as vacuum evaporation or sputtering or a plating method is known. . For example, a magnetic tape on which Co is deposited (JP-A-54-147010),
Perpendicular magnetic recording medium using Co-Cr alloy
-134706) is known. The metal thin film formed by such thin film forming means as vapor deposition, sputtering, or ion plating has a very small thickness of 1.5 μm or less.
There is an advantage that performance equal to or higher than that of a coating type magnetic recording medium having a thickness of not less than μm (a magnetic recording medium obtained by mixing a magnetic substance powder into an organic polymer binder and coating on a non-magnetic support) can be obtained.

[0003] By the way, it is considered that the magnetic characteristics such as the coercive force Hc or the squareness ratio of the hysteresis loop, which are static characteristics of the magnetic recording medium, do not depend much on the surface condition of the non-magnetic support used. As an example based on this idea, U.S. Pat. No. 3,787,327 discloses a multilayer structure of Co--Cr by vacuum evaporation.

However, in a metal thin film type magnetic recording medium, the metal thin film formed on the surface of the non-magnetic support is thin, and the surface state (surface irregularities) of the non-magnetic support manifests itself as irregularities on the surface of the magnetic recording layer. However, it is a disadvantage that it causes noise.

[0005] From the viewpoint of noise, it is preferable that the surface state of the nonmagnetic support is as smooth as possible. On the other hand, from the viewpoint of handling such as winding and unwinding of the base film, if the film surface is smooth, the slipperiness between the film and the film is poor, and a blocking phenomenon occurs, making it impossible to produce a product. It is required that the film surface be rough. As described above, the surface of the non-magnetic support is required to be smooth from the viewpoint of electromagnetic conversion characteristics, and is required to be rough from the viewpoint of handling properties. Therefore, it is necessary to simultaneously satisfy these two conflicting properties.

Further, a serious problem of the metal thin film magnetic recording medium when it is actually used is the running property of the metal thin film surface. In the case of a coating type magnetic recording medium in which a conventional magnetic powder is mixed with an organic polymer binder and applied to a base film, a lubricant is dispersed in the binder to improve the runnability of the magnetic surface. However, in the case of a metal thin-film magnetic recording medium, such measures cannot be taken, and it is very difficult to maintain a stable running property.
In particular, it has disadvantages such as poor running performance at high temperature and high humidity.

For the purpose of improving this drawback, Japanese Patent Publication No. Sho 62
Japanese Patent No. 30105 proposes forming fine projections on a film surface using fine particles, a water-soluble resin and a silane coupling agent. In addition, Tokiko 62-301
No. 06 and JP-A-59-229316 propose forming minute projections on the film surface using fine particles and a water-soluble resin. However, all of them have fine particles present in the trapezoidal protrusions of the water-soluble resin, and do not have fine particles uniformly present on the film surface. Japanese Patent Publication No. 34456/1989 proposes that a discontinuous film of a water-soluble polymer and fine particles forming higher projections are independently adhered to the film surface. However, this is inferior in uniformity on the film surface because the projections are discontinuous films and are due to fine particles that are not uniformly dispersed. In addition, Japanese Unexamined Patent Publication No.
Japanese Patent No. 30231 proposes forming at least 1,000 resin particles / mm ² having a particle height of 30 to 500 angstroms with thermoplastic resin fine particles at the core. However, this is also a discontinuous film in which the plastic film is exposed between the protrusions, and is inferior in the effect of preventing the precipitation of oligomer microcrystals on the film surface. Further, Japanese Patent Publication No. 1-35766 discloses a fine particle-like projection having fine particles made of a metal alkoxide hydrolysis product as a nucleus and a resin as a binder, and having a height of 30 to 500.
It has been proposed that angstrom, fine particles having a width of the protrusions of 1 to 20 times the height be present on the surface of the plastic film in an amount of 1000 / mm ² or more. However, such fine particles that can reduce the height of the projections are very undesirably easily aggregated in the coating film and form large projections.

Further, as described in Japanese Patent Publication No. 27733/1990, a metal thin film type magnetic recording medium has a structure in which the base film has the energy of vapor such as metal ions, the evaporation source, and other high temperature parts when the metal thin film is formed. The temperature rises by receiving radiation energy from the substrate, thereby causing oligomer precipitation.
When the amount of this oligomer is too large, the flatness of the film surface is impaired, which is not preferable.
It is preferred that an appropriate amount be precipitated as described in the publication. However, the polyamide resin, cellulose resin, epoxy resin, urethane resin and silicone resin exemplified in Japanese Patent Publication No. Hei 2-27733 have difficulty in ensuring the flatness of the coating film, and particularly, the stretching step during the production of a polyester film. If a crosslinked polymer thin film is formed on the film surface in the middle and a surface having a liquid or granular pattern is formed in the subsequent stretching step, the resulting film surface may have a wavy wrinkle surface or a worm-like surface. And the flatness is impaired.

On the other hand, in order to increase the recording / reproducing time, it is general to reduce the thickness of the tape and increase the amount of tape that can be wound on a cassette of a fixed size. Such a base film for a magnetic recording tape has a stress at the time of 5% elongation in the longitudinal direction (longitudinal direction) of 18 kg / mm ² or more, a Young's modulus in the longitudinal direction of 800 kg / mm ² or more, and a width direction. Young's modulus of (lateral direction) is 500kg / mm ²
It has been proposed to use the above polyethylene-2,6-naphthalate film. This magnetic recording tape can certainly increase the coercive force of magnetic recording.

However, even with a tape using such a film, there is a problem in running property and durability when the thickness of the tape is reduced to increase the recording / reproducing time. That is, when the magnetic recording tape is run repeatedly, there is a problem that the end portion of the tape is damaged and deformed into a wrinkle-like shape, thereby deteriorating the characteristics of the tape. When a metal thin film is formed on the film support, the support film curls, and the tape curves when the tape is wound into a cassette or used in a subsequent magnetic recording tape process. There is a problem in that the magnetic head does not come into contact with the magnetic head and no output is produced, and the running of the tape becomes unstable.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art, and to provide a magnetic layer having excellent magnetic properties, such as excellent running properties (especially still characteristics and shuttle characteristics) and electromagnetic conversion characteristics , especially on a metal thin film surface. An object of the present invention is to provide a polyester film useful for producing a recording medium, particularly a metal thin film magnetic recording medium suitable for long-time recording.

[0012]

The present invention has the following configuration to attain the above object.

A polyester film having a surface coated with a primer layer for a magnetic layer composed of a continuous thin film, wherein the continuous thin film has a surface having a height of 5 nm or less and a fine protrusion made of only a resin forming the thin film. Is 5.0 × 10 ⁷ or more
5.0 in a proportion of × 10 ¹³ pieces / mm ^2, very small surface roughness Ra ^s of the portion that does not include microprotrusions of the continuous film is 1.5
0 nm or less, and the surface roughness Ra of the continuous thin film is 1 to 1
0 nm, and the continuous thin film is heated to 160 ° C.
A polyester film for a magnetic recording medium, wherein the precipitation rate of polyester oligomer microcrystals on a thin film can be suppressed to 0.8% or less when heated in air for 5 minutes.

The polyester constituting the film of the present invention is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Preferred specific examples of such a polyester include polyethylene terephthalate,
Examples thereof include polyethylene isophthalate, polytetramethylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), polyethylene-2,6-naphthalenedicarboxylate, and the like, and copolymers of these or other resins with a small proportion thereof And the like. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferred.

[0015] Such a polyester can be produced by a conventionally known method. For example, polyethylene-2,6-naphthalate undergoes an esterification reaction of 2,6-naphthalenedicarboxylic acid and ethylene glycol or a transesterification reaction of 2,6-naphthalenedicarboxylic acid dimethyl ester and ethylene glycol, followed by a reaction product. Can be produced by a polycondensation method. In that case, a known catalyst can be used, but it is preferable to use an organic titanium compound as a catalyst for the polycondensation reaction from the viewpoint of film characteristics.

As the organic titanium compound, there can be mentioned, for example, those described in JP-A-63-278927. To further explain, an alcoholate or an organic acid salt of titanium, a reaction product of a tetraalkyl titanate with an aromatic polycarboxylic acid or an anhydride thereof, and the like can be exemplified. Preferred specific examples include titanium tetrabutoxide, titanium isopropoxide, and titanium oxalate. , Titanium acetate, titanium benzoate, titanium trimellitate, and a reaction product of tetrabutyl titanate and trimellitic anhydride. The amount of the organic titanium compound used is preferably such that the titanium atom accounts for 3 to 12 mg atom% based on the acid component constituting the polyester.

In the polyester, roughening materials well known in the art, such as calcium carbonate, kaolinite, titanium dioxide, silica alumina, etc., and other additives may be contained in the polyester within a range not to impair the object of the present invention. Can be contained.

The polyester film of the present invention comprises:
Young's modulus in the longitudinal direction (E_MD) Is 550kg / mm^TwoAbove, good
Preferably 650 kg / mm^TwoAnd the Young's modulus in the width direction
(E _TD) Is 550kg / mm^TwoAbove, preferably 650 kg /
mm^TwoAnd the sum of the Young's moduli in both directions (E_MD+
E_TD) Is 1150kg / mm^TwoAbove, preferably 1200kg
/ Mm^TwoIt is desirable that this is the case. This longitudinal yang
550kg / mm^TwoIf it is less than
Sometimes the tape stretches and deforms under strong stress
It is not preferable. The Young's modulus in the width direction is 550kg /
mm^TwoIf it is less than this, repeat the running of the magnetic tape,
The ends of the loop are damaged and wrinkled
Not good.

The polyester film according to the present invention comprises:
Further, the heat shrinkage in the width direction when treated at 105 ° C. for 30 minutes is 1.0 to 3.5%, more preferably 1.0 to 3.0.
%. If the heat shrinkage is less than 1.0% or more than 3.5%, the curl of the magnetic tape becomes remarkable, which is not preferable.

Such a polyester film can be manufactured by using a known method. For example, polyethylene-2,6-naphthalate is melt-extruded, preferably melt-extruded at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C., and solidified by cooling to obtain an unstretched film. (Tg-10) ~
(Tg + 70) ° C (Tg: polyethylene-
(Glass transition temperature of 2,6-naphthalate) at a predetermined magnification, and then Tg in a direction perpendicular to the above-mentioned stretching direction (when the first-stage stretching is a longitudinal direction, the second-stage stretching is a transverse direction).
It can be manufactured using a method of stretching at a predetermined magnification at a temperature of (° C.) to (Tg + 70) ° C. and further heat setting. At this time, the stretching ratio, stretching temperature, heat setting conditions, etc. are selected and determined from the characteristics of the film. The area stretching ratio is preferably 9 to 22 times, more preferably 12 to 22 times.
The heat setting temperature may be determined in the range of 190 to 250 ° C., and the processing time may be determined in the range of 1 to 60 seconds.

In addition to the sequential biaxial stretching method, a simultaneous biaxial stretching method can be used. In the sequential biaxial stretching method, the number of stretching in the longitudinal direction and the transverse direction is not limited to one, and the longitudinal-lateral stretching can be performed by stretching several times,
The number of times is not limited. For example, when it is desired to further improve the mechanical properties, the heat setting temperature of the biaxially stretched film before the heat setting treatment is set to (Tg + 20) ° C.
(Tg + 70) ° C., heat-set, stretched in the vertical or horizontal direction at a temperature higher by 10 to 40 ° C. than this heat-setting temperature, and then further stretched in the horizontal or vertical direction by a temperature higher by 20 to 50 ° C. than this temperature And a total stretching ratio of 5.0 to 6.
9 times, and the total stretching ratio in the transverse direction can be 5.0 to 6.9 times. The film thickness after stretch orientation is generally 2
To 100 μm, preferably 3 to 50 μm.

In order to adjust the heat shrinkage of the high Young's modulus film, a method in which the heat-treated film is further heated under low tension and relaxed in the longitudinal direction can be used.
As a method of relaxing in the longitudinal direction, for example, a method of relaxing in a non-contact state under heating and low tension by a floating treatment method by air force; a method of relaxing by giving a speed difference between a heating roll and a cooling roll each having a nip roll. Alternatively, a method may be used in which a clip holding a film in a tenter is gradually relaxed by gradually slowing the advancing speed of the clip.

In the present invention, a continuous thin film is applied as a primer layer for a magnetic layer on the surface of a polyester film. Then, a magnetic layer, in particular, a ferromagnetic metal thin film layer is formed on this thin film.

The thin film is formed on the surface of the continuous thin film.
5.0 × 10⁷~ 5.0x
10¹³Pieces / mm^Two, Preferably 5.0 × 10⁷~ 5.0x
10 ¹²Pieces / mm^Two, More preferably 5.0 × 10⁸~ 5.
0x10¹¹Pieces / mm^TwoOf the microprojections
The thickness is 5 nm (50 angstroms) or less, preferably
40 Å or less. Furthermore, the continuous thin film
Micro surface roughness Ra of the portion not including the micro projections^sIs
1.50 nm or less, preferably 1.35 nm or less
You. And the surface roughness of the continuous thin film (total surface roughness)
Ra is 1 to 10 nm (0.001 to 0.010 μm),
Preferably 1 to 7 nm (0.001 to 0.007 μm)
It is. Further, the thickness of the continuous thin film is such that the film
On continuous thin film when continuously heated in air at 60 ° C for 5 minutes
0.8% precipitation rate of polyester oligomer microcrystals
Or less, preferably 0.75% or less, more preferably
It is necessary that the thickness can be suppressed to 0.6% or less.

In the present invention, the resin forming the continuous thin film of the primer for the magnetic layer includes alkyd resin, unsaturated polyester resin, saturated polyester resin, phenol resin, amino resin, vinyl acetate resin, vinyl chloride-vinyl acetate resin, acrylic resin Resin, acrylic-polyester resin and the like can be exemplified. These resins may be a homopolymer, a copolymer, or a mixture.

The acrylic resin may be, for example, an acrylate ester (alcohol residues include methyl, ethyl, n-propyl, isopropyl, n-butyl,
Isobutyl group, t-butyl group, 2-ethylhexyl group,
Examples thereof include a cyclohexyl group, a phenyl group, a benzyl group and a phenylethyl group); methacrylic acid esters (alcohol residues are the same as described above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
Hydroxy-containing monomers such as -hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-dimethylol Amide group-containing monomers such as acrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-phenylacrylamide; amino group-containing monomers such as N, N-diethylaminoethyl acrylate and N, N-diethylaminoethyl methacrylate; Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; styrene sulfonic acid, vinyl sulfo Monomers containing sulfonic acid groups or salts thereof, such as acids and salts thereof (eg, sodium salts, potassium salts, ammonium salts, etc.); crotonic acid, itaconic acid, acrylic acid, maleic acid, fumaric acid, and Monomers containing a carboxyl group or a salt thereof such as a salt (eg, sodium salt, potassium salt, ammonium salt, etc.); monomers containing an anhydride such as maleic anhydride or itaconic anhydride; other vinyl isocyanate, allyl isocyanate, styrene , Vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester,
Alkyl fumaric acid monoester, acrylonitrile,
(Meth) acrylic monomers such as acrylic acid derivatives and methacrylic acid derivatives, which are made from a combination of monomers such as methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate and vinyl chloride Is preferably contained in an amount of 50 mol% or more, particularly preferably a component containing a methyl methacrylate component.

Such an acrylic resin can be self-crosslinked with a functional group in the molecule, or can be crosslinked with a crosslinking agent such as a melamine resin or an epoxy compound.

The acid components constituting the polyester resin include, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-
Naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2
—Polyvalent carboxylic acids such as potassium sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, and monopotassium trimellitic acid salt. Examples of the hydroxy compound component include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol,
-Xylylene glycol, ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate, etc. May be exemplified. A polyester resin can be prepared from these compounds by a conventional method. When preparing an aqueous coating liquid, it is preferable to use a polyester resin containing a 5-sodium sulfoisophthalic acid component or a carboxylate group. Such a polyester resin can be a self-crosslinking type having a functional group in the molecule, or can be crosslinked using a curing agent such as a melamine resin or an epoxy resin.

Further, the acryl-polyester resin is used to mean an acryl-modified polyester resin and a polyester-modified acryl resin. An acryl-polyester resin and a polyester resin component are bonded to each other. Type, block type, etc. Acrylic-polyester resin, for example, adds a radical initiator to both ends of the polyester resin to polymerize the acrylic monomer, or attaches a radical initiator to the side chain of the polyester resin to polymerize the acrylic monomer. Alternatively, it can be produced by attaching a hydroxyl group to the side chain of the acrylic resin and reacting it with a polyester having an isocyanate group or a carboxyl group at a terminal to obtain a comb polymer. The polyester resin used at that time preferably does not contain a sulfonyloxy group in the molecule.

In the present invention, the formation of the primer layer for the magnetic layer (a continuous thin film having fine protrusions made of only resin) is carried out by applying a resin coating solution containing emulsion resin particles, preferably an aqueous coating solution, to a biaxially oriented polyester film production process. Among them, the method can be carried out by applying and drying the film surface, preferably on the film surface before the completion of the crystal orientation, or by applying and drying the resin coating solution on the biaxially oriented polyester film. Is preferred.

Here, the polyester film before the completion of the crystal orientation means an unstretched film obtained by extruding polyester into a film as it is, and orienting the unstretched film in either the longitudinal direction or the transverse direction. A uniaxially stretched film, or a biaxially stretched film that is stretched in a biaxial direction, but is stretched in at least one direction at a low magnification, and further needs to be stretched in that direction (finally in a longitudinal direction and / or a transverse direction). (A biaxially stretched film) before re-stretching in the direction to complete orientation crystallization.

The aqueous coating solution may contain a surfactant for facilitating the application. Such a surfactant can increase the surface tension of the aqueous coating solution by 40.
dyne / cm or less, which promotes wetting of the polyester film. Examples thereof include polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate, Examples thereof include anionic and nonionic surfactants such as alkyl sulfonates and alkyl sulfosuccinates. Further, other additives such as, for example, an antistatic agent, an ultraviolet absorber, and a lubricant can be mixed within a range in which the effects of the present invention are not lost.

As described above, the resin coating solution contains emulsion resin particles having an appropriate size, and the size of the emulsion resin particles is 20 to 120 nm as measured by a light scattering method. Preferably has an average particle size of 25 to 80 nm.

As a coating method, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method, or the like may be applied alone or in combination.

In the various methods described above, the fine surface roughness of the continuous thin film is controlled within a predetermined value.
From the viewpoint of forming a predetermined number of microprojections of Angstroms or less and further suppressing the precipitation of oligomers, an acrylic resin and a polyester resin or an aryl-polyester resin are used as a resin component for forming a thin film, and a solution is formed by a roll coating method. Is preferred.

In the present invention, the solid content of the coating liquid, especially the aqueous coating liquid, is usually 30% by weight or less, preferably 15% by weight or less. The viscosity of the coating solution is usually 100 centipoise (cps) or less, preferably 20 cps or less.
The amount of coating is about 0.5 to ² per square meter of running film.
0 g, even about 1~10g is preferred. In other words, in the finally obtained biaxially oriented film, about 0.001 to 1 g per m ² ,
Preferably, the solid content is between 5 and 0.3 g.

When a magnetic layer, particularly a metal thin film magnetic layer, is provided on a continuous thin film of a base film having a continuous thin film formed in this way, noise is drastically reduced, the noise level is remarkably improved, and Running performance (for example, still
Properties, shuttle properties) , with excellent storage durability,
In addition, a magnetic recording medium suitable for long-time recording can be obtained.

In the present invention, it is preferable to coat a continuous thin film for forming a smooth surface on the other surface of the polyester film, that is, the surface opposite to the surface on which the continuous thin film serving as a primer for the magnetic layer is provided. The thin film contains a cellulose resin and fine particles having an average particle size of 0.15 μm or less, preferably 0.01 to 0.1 μm, and has a surface roughness Ra of 2 to 10 nm (0.002 to 0.01 μm).
m), preferably 3-9 nm (0.003-0.009
μm) is desirable.

Examples of the cellulose resin include ethyl cellulose, methyl cellulose, acetyl cellulose, acetoacetyl cellulose, nitrocellulose, carboxylated cellulose, carboxymethyl cellulose, and cellulose acetate butyrate.
By using this cellulosic resin, many minute folds can be formed on the surface of the coating film.

The fine particles include polystyrene,
Organic fine particles such as polymethyl methacrylate, methyl methacrylate copolymer, methyl methacrylate copolymer crosslinked product, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine resin, silica, alumina, titanium dioxide, kaolin, talc, graphite Any of inorganic fine particles such as calcium carbonate, feldspar, molybdenum disulfide, carbon black, barium sulfate and the like may be used. These may be in the form of an aqueous dispersion using an emulsifier or the like,
Further, those which can be added to the aqueous liquid in the form of fine powder may be used.

The cellulosic resin and the fine particles have an effect of promoting uniform formation of minute projections of the coating film itself and a function of reinforcing the coating film by the fine particles themselves. Combined with the effect on the reduction and the like, and the improvement of the scratch resistance due to the synergistic action of the two, it gives the film excellent slipperiness.

The resin forming the thin film having a smooth surface is preferably excellent in blocking resistance, frictional force reducing property and the like, and examples thereof include acrylic resin, polyester resin and acryl-polyester resin. In the description of these resins, the description of the acrylic resin, polyester resin, and acryl-polyester resin described above as the resin used for forming the primer for the magnetic layer can be used as it is.

The proportion of the components forming the smooth surface, that is, the thin film-forming resin (component a), the cellulose resin (component b) and the fine particles (component c) is preferably determined by designing the surface characteristics. Component a is 30 to 80% by weight, component b is 1 to 50% by weight, component c is 5 to 40% by weight
It is preferred that If the amount of the component a is too small, the adhesion of the coating film to the polyester film is reduced. On the other hand, if the amount is too large, the blocking resistance and the slipperiness are reduced. If the amount of the component b is too small, the folds of the coating film are reduced and the processability is reduced, while if it is too large, the surface is too rough. If the amount of the component c is too small, the lubricity is reduced, while if it is too large, the particles are liable to fall off from the coating film.

The formation of the slippery coating film in the present invention may be carried out after the production of the polyester film or during the production of the polyester film, but is preferably carried out during the production of the polyester film. For example, it is preferable to apply an aqueous coating solution to the surface of the polyester film before the completion of the crystal orientation. Furthermore, it is preferable to apply an aqueous coating solution having the above composition to a film that has not been stretched or stretched in a uniaxial direction, and then apply longitudinal stretching and / or transverse stretching and heat fixing, that is, a so-called in-line coating method. . At that time, in order to smoothly apply the coating film on the surface of the polyester film before the completion of the oriented crystal, a corona discharge treatment is performed on the film surface as a preliminary treatment, or together with the coating composition, It is preferable to use a chemically inert surfactant in combination. Such a surfactant can lower the surface tension of the aqueous coating solution to 40 dyne / cm or less, and promotes wetting of the polyester film. Examples of the surfactant include polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester,
Examples of the surfactant include anionic and nonionic surfactants such as glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate, alkyl sulfonate, and alkyl sulfosuccinate. Further, other additives such as, for example, an antistatic agent, an ultraviolet absorber, and a lubricant can be mixed within a range in which the effects of the present invention are not lost.

In the present invention, a coating liquid for forming a slippery coating film, especially
The solid content concentration of the aqueous coating liquid is usually 30% by weight or less,
It is preferably at most 15% by weight. The viscosity of the coating liquid is usually 100
Not more than an inchpoise (cps), preferably not more than 20 cps
It is. Coating amount is 1m of running film^TwoAbout
0.5-20 g, more preferably about 1-10 g, is preferred. Paraphrase
Then, in the finally obtained biaxially oriented film,
1m on one surface of film ^TwoAbout 0.001-1 g per
Preferably have a solids content of about 0.005 to 0.3 g.
New

As a coating method, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method, or the like may be applied alone or in combination.

According to the preferred production method of the present invention,
The aqueous coating liquid is applied to the film immediately after the longitudinal uniaxial stretching, and the film is guided to a tenter for transverse stretching and heat setting. At that time, the coated material is expanded in the state of an unsolidified coating film as the film is stretched, and the area thereof is expanded and heated to evaporate water, and a thin solid continuous coating layer is formed on the surface of the biaxially stretched film. The film is converted and firmly fixed to the biaxially stretched film surface. The above heat treatment is preferably carried out at a temperature of about 80 ° C to about 250 ° C, usually for about 1 to about 6 ° C.
Performed for 0 seconds.

The production of a metal thin film magnetic recording medium using the polyester film of the present invention can be carried out by a method known per se,
For example, JP-A-54-147010, JP-A-52-147010
The method can be performed by the method described in 134706, specifically, a vacuum deposition method, an ion plating method,
A sputtering method can be preferably used.

The polyester film of the present invention can form a magnetic layer, particularly a metal thin film magnetic layer, which is smooth and excellent in running property and storage durability, has a remarkable reduction in noise, has a remarkably excellent noise level, and has a magnetic layer. The present invention is useful for manufacturing a magnetic recording medium suitable for long-time recording excellent in running property on a surface, particularly a metal thin film surface, particularly a metal thin film magnetic recording medium.

The various properties herein are measured as follows.

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

(2) Particle Size of Emulsion Resin Particle The particle size of the emulsion resin particles in the coating liquid is represented by the “equivalent spherical diameter” of the particles at 50% by weight of all the particles determined by the light scattering method. .

(3) Number of Projections The measurement of minute projections on the surface of the continuous thin film is performed by a scanning electron microscope. That is, evaluation is performed at a magnification of 50,000 to 200,000.

(4) Height of Microprojections The height of microprojections on the surface of the continuous thin film is measured by a three-dimensional roughness meter (scanning tunnel microscope) using a tunnel current. That is, using a sample in which gold having a thickness of 200 Å was uniformly deposited on the film surface, the voltage applied between the surface to be measured and the metal probe was 0.8 V, and the set tunnel current was 0.5 nA. The height of each microprojection is measured by measuring a range of 2 μm × 2 μm in the atmosphere, and the average value of 10 microprojections is defined as the height of the microprojections.

[0055] (5) Measurement length in the direction of the micro surface roughness Ra ^s above its center line by selecting a portion having no microprotrusions from the film surface roughness curve in the range of 2 microns × 2 microns as measured on the same sample When the roughness curve is represented by Y = f (x) with the center line of the extracted portion taken as the X axis and the direction of the vertical magnification as the Y axis, the value given by the following equation is obtained. Expressed in nm.

[0056]

(Equation 2)

Actually, this measurement is performed on a portion without fine projections.
The value obtained for the length of 0.4 to 1.2 microns in
And the average value of 10 measurements is the fine surface roughness
Ra ^sAnd

(6) Surface Roughness According to JIS B0601, using a high-precision surface roughness meter SE-3FAT manufactured by Kosaka Laboratory Co., Ltd., the radius of the needle is 2 μm.
m, load 30mg, magnification 200,000, cut off 0.0
Under the condition of 8 mm, the chart is drawn, a portion of the measured length L is extracted from the film surface roughness curve in the direction of the center line, the center line of the extracted portion is set as the X axis, and the direction of the vertical magnification is set as the Y axis. When the roughness curve is represented by Y = f (x),
The value given by the following equation is expressed in μm.

[0059]

(Equation 3)

This measurement is performed for four pieces with the reference length set to 1.25 mm, and the average value is represented.

(7) Coefficient of friction (film slippery) The coefficient of static friction (μs) is measured using a slippery measuring device manufactured by Toyo Tester Co. according to ASTM D1894-63. However, the thread plate is a glass plate and the load is 1
kg.

The film slippery is determined based on the following criteria. ：: good (less than μs 0.6) Δ: slightly poor (μs 0.6 to 0.8) ×: bad (μs 0.8 or more)

(8) Deposition rate of oligomer The film was fixed on a wooden frame, kept in a hot air circulating (air) type dryer at 160 ° C. for 5 minutes, and then aluminum was vapor-deposited on the film surface. Take a photo of the film surface with. On this photograph, the oligomer precipitation rate is evaluated by the percentage of the total area occupied by the oligomers (appearing as white spots) with respect to the entire area of the photograph.

(9) Young's Modulus The film was cut into a sample having a width of 10 mm and a length of 15 cm, and a chuck speed of 100 mm, a pulling speed of 10 mm / min and a chart speed of 5 mm.
It is pulled by an Instron type universal tensile tester at 00 mm / min. The Young's modulus is calculated from the tangent at the rising portion of the obtained load-elongation curve.

(10) Heat Shrinkage A film is cut out into a 10 mm-wide and 600 mm-long sponge shape, and mark points are provided at intervals of 500 mm. The sample is treated under a non-tension condition with a gear open at 105 ° C. for 30 minutes, and then cooled to room temperature. The heat shrinkage is calculated from the dimensional change before and after the heat treatment. Dimensions are measured using the MITUTOYO micro-size measuring device (PROFILE PROJECTOR MODEL PJ321
Use F).

(11) Electromagnetic conversion characteristics Co-Cr (Cr: 23 wt%) was set by using a vacuum evaporation apparatus to place a film along a cylindrical can having a diameter of 1 m, and setting the angle of incidence of the film of evaporated atoms to 20 ° to 70 °. Contained)
The alloy is obliquely deposited to a film thickness of about 1400 angstroms,
Forming a first magnetic layer; Further, the second magnetic layer is formed on the first magnetic layer.
The magnetic layer of Co—Ni—O (Ni content relative to Co: 20) in oxygen of 7 × 10 ⁻⁵ Torr, where the incident angle of the evaporated atoms to the first magnetic layer is 10 ° or more and 50 ° or less.
(wt%, containing 25 wt% of oxygen atoms during film formation) An oblique vapor deposition of an alloy is performed to a thickness of 500 Å to form a sample tape.

This tape was processed into a width of 8 mm to form a vapor deposition tape, and a white peak of 0.45 μm and a bandwidth of 9 (MH) were obtained using an amorphous head having a gap length of 0.18 μm.
z) C / N (initial value) is compared.

From this C / N, determination is made according to the following criteria. ：: +0.0 dB or more relative to the reference value Δ: 〃 -0.5 dB to +0.0 dB ×: 未 満 less than -0.5 dB

After recording and reproduction were repeated at a tape running speed of 85 cm / min at 40 ° C. and 80% RH, the 250th C
/ N (durability).

From this C / N, a determination is made according to the following criteria. ：: +0.0 dB or more relative to the reference value Δ: 〃 -1.0 dB to +0.0 dB ×: 未 満 less than -1.0 dB

(12) Still Characteristics A 4.2 MHz video signal is recorded on the above-mentioned vapor-deposited tape, and the time required for the reproduced output to attenuate to 50% is measured. Based on this time, determination is made based on the following criteria. ：: Decay time at 50% is 100 minutes or more △: 〃 50 minutes to 100 minutes ×: 未 満 Less than 50 minutes

(13) Shuttle Characteristics A 4.2 MHz video signal was recorded on the above-described vapor-deposited tape, and the tape traveling speed was 41 m at 25 ° C. and 50% RH.
/ Min, a run at a rewind speed of 41 m / min is defined as one run, and the output fluctuation after a total of 200 runs is examined. Judgment is made based on the output fluctuation based on the following criteria. ：: output fluctuation after 200 repetitions is 0 dB to -0.3
dB ○: Output fluctuation after 200 repetitions is −0.3 dB to −
0.6 dB Δ: The output fluctuation after 200 repetitions is −0.6 dB to −.
1.5 dB ×: output fluctuation after 200 repetitions is −1.5 dB or more

(14) Curl A 500 × 500 mm square sample is cut out from the magnetic recording tape raw material, and the curl state is determined according to the following criteria. XX: Completely cylindrical shape ×: Part of the tube is open Δ: Opening is wider than above,
The longest part of the side can be made the diameter of a circle. ○: The opening is wider than the above, and the longest part of the side cannot be made the diameter of a circle. ◎: The curl has no or almost no curl.

[0074]

EXAMPLES The present invention will be further described below with reference to examples. "Parts" in the examples are parts by weight.

[0075]

Example 1 0.025 part of manganese acetate tetrahydrate and 0.003 part of potassium acetate were added to a mixture of 100 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester and 60 parts of ethylene glycol, and the internal temperature was raised to 150 ° C. The ester exchange reaction was carried out while gradually increasing the temperature. When the transesterification rate reaches 95%, 0.069 of a glycol solution of a phosphorus compound in which 25 parts of trimethyl phosphate and 75 parts of ethylene glycol have been reacted in advance as a stabilizer.
After stirring sufficiently, a solution prepared by reacting 0.8 parts of trimellitic anhydride with 0.65 parts of tetrabutyl titanate in 2.5 parts of ethylene glycol (titanium content: 11 parts)
0.014 parts by weight). Next, the reaction product was transferred to a polymerization reactor and subjected to a polycondensation reaction under a high-temperature vacuum (final internal temperature: 295 ° C.) to obtain polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.58.

The polyethylene-2,6-naphthalate was melt-extruded according to a conventional method, quenched to prepare an unstretched film having a thickness of 160 μm, and then unstretched at 130 ° C. in the longitudinal direction (longitudinal direction). A biaxially oriented film having a thickness of 6.3 μm was prepared by performing sequential biaxial stretching at 135 ° C. and 5.2 times at 135 ° C. in the width direction (horizontal direction) and further performing heat setting at 200 ° C. for 5 seconds.

At this time, a coating solution having the following composition was applied to the uniaxially stretched film before the transverse stretching by the roll coating method to obtain the surface (A) of the film.
And (B). The surface (A) is the surface on the side on which the magnetic layer is formed, and the surface (B) forms a smooth surface.

Composition of coating solution applied to film surface (A): 85.0 parts of a 1.4 wt% solution of an aqueous emulsion prepared by the following method: polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF Corporation) 15.0 parts of a 1.4 wt% solution of the above) The coating amount is 2.7 g / m ² in a wet state.

[Synthesis of Aqueous Emulsion] The acid components were terephthalic acid (45 mol%) and isophthalic acid (55 mol%).
%), And 100 parts of a polyester (having an intrinsic viscosity of 0.40 measured in o-chlorophenol at 35 ° C.) having a glycol component of diethylene glycol was dissolved in 900 parts of tetrahydrofuran while heating at 64 ° C. under normal pressure. Thereafter, 900 parts of deionized water was gradually added with high-speed stirring. After the addition of the entire amount, the mixture was heated again to 80 ° C. to remove the tetrahydrofuran by evaporation to obtain a 10 wt% aqueous dispersion of polyester.

This aqueous dispersion was heated to 60 ° C. under normal pressure, and 1 part of ammonium persulfate was added. Thereafter, the mixture was heated to 80 ° C., and a mixture of 50 parts of methyl methacrylate, 70 parts of ethyl acrylate, 29 parts of methacrylic acid, and 1 part of t-dodecyl mercaptan was gradually added. Then, 100 parts of deionized water containing 1 part of ammonium persulfate and 2 parts of sodium hydrogen carbonate were gradually added. After the addition was completed, the reaction was further continued for 3 hours and then cooled to room temperature.

This reaction product has a solid content of 20 wt.
%, A stable aqueous emulsion having a particle size of 35 nm.

Composition of the coating liquid applied to the film surface (B): 2.5 wt% solution of the above-mentioned aqueous emulsion 63.0 parts 2.5 wt% of cellulose resin (Methylcellulose SM-15 manufactured by Shin-Etsu Chemical Co., Ltd.) Solution 18.0 parts Polymethyl methacrylate fine particles (Nippon Shokubai Co., Ltd., Eposter MA) 2.5 wt% solution 9.0 parts (However, the average particle diameter of these fine particles is 0.040 μm) Polyoxyethylene nonyl 10.0 parts of a 2.5 wt% solution of phenyl ether (NS208.5 manufactured by NOF Corporation) 10.0 parts The coating amount is 4.0 g / m ² in a wet state.

Table 1 shows the properties of the obtained polyester film and a magnetic recording medium having a magnetic layer provided on the surface (A) side of this film.

[0084]

Example 2 A biaxially oriented film having a thickness of 6.3 μm was obtained in the same manner as in Example 1 except that the coating solution applied to the film surface (A) was changed as follows.

Composition of coating liquid applied to film surface (A): 90.0 parts of a 1.5 wt% solution of acrylic-polyester resin (Pesthresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 90.0 parts of polyoxyethylene nonylphenyl ether (Nippon Yushi ( 10.0 parts of a 1.5 wt% solution of NS208.5) manufactured by K.K. Co., Ltd. The coating amount is 3.6 g / m ² on a wet basis.

Table 1 shows the properties of the obtained polyester film and a magnetic recording medium having a magnetic layer provided on the surface (A) side of the film.

[0087]

Example 3 Silicon dioxide having an average particle size of 0.15 μm was added.
Silicon dioxide-containing polyethylene-2, similar to Example 1, except that 10 parts were added after the transesterification reaction was completed.
6-Naphthalate was obtained.

The polyethylene-2,6 obtained in Example 1
-Naphthalate and the silicon dioxide-containing polyethylene-
2,6-Naphthalate was co-extruded at a thickness ratio of 7: 3 to prepare a laminated unstretched film having a thickness of 185 μm.

Next, the unstretched film is vertically stretched for 14 hours.
Sequential biaxial stretching at 4.2 ° C at 0 ° C and 4.0 times at 135 ° C in the transverse direction was performed, followed by heat setting at 205 ° C for 5 seconds to obtain a thickness of 10.
A 2 μm biaxially oriented film was produced. At this time, a coating liquid having the following composition was applied to the outer surface (A) having a thickness ratio of 7 and the outer surface (B) having a thickness ratio of 3 (silicon dioxide-containing polyethylene-2,6-naphthalate layer) by a roll coating method. Applied.

Composition of coating liquid applied to film surface (A): 0.6 wt% solution of polyester resin (WR901 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 35.0 parts Polyester resin (Dainippon Ink Chemical Industry Co., Ltd.) 35.0 parts of a 0.6 wt% solution of FINETEX ES-520) 30.0 parts of a 0.6 wt% solution of polyoxyethylene nonyl phenyl ether (NS208.5, manufactured by NOF Corporation) 30.0 parts 7 g / m ² .

Composition of coating liquid applied to film surface (B): 32.0 parts of a 2.5 wt% solution of polyester resin (FINETEX ES-520 manufactured by Dainippon Ink and Chemicals, Inc.) acrylic resin (Dainippon Ink Chemical 40.0 parts of a 2.5 wt% solution of VONCOAT AC-503 manufactured by Kogyo Co., Ltd. 10.0 parts of a 2.5 wt% solution of a cellulose resin (methyl cellulose SM-15 manufactured by Shin-Etsu Chemical Co., Ltd.) 10.0 parts 8.0 parts of a 2.5 wt% solution of colloidal silica having a thickness of 05 μm 8.0 parts of a 2.5 wt% solution of polyoxyethylene nonyl phenyl ether (NS208.5 manufactured by NOF Corporation) 10.0 parts The coating amount is 4.4 g / wet. m ² .

Table 1 shows the properties of the obtained polyester film and the magnetic recording medium having the magnetic layer provided on the surface (A) side of the film.

[0093]

Example 4 A polyester film was obtained in the same manner as in Example 1 except that the coating liquid applied to the film surface (A) side was changed as follows.

Composition of coating liquid applied to film surface (A): 0.2 wt% solution of acrylic resin (Dulima AT-613, manufactured by Nippon Pure Chemical Co., Ltd.) 50.0 parts Polyoxyethylene nonyl phenyl ether (Nippon Oil & Fats) 50.0 parts of a 2.5 wt% solution of NS208.5 (manufactured by Co., Ltd.) The applied amount is 3.0 g / m ² on a wet basis.

Table 1 shows the characteristics of the obtained polyester film and a magnetic recording medium having a magnetic layer provided on the surface (A) side of this film.

[0096]

COMPARATIVE EXAMPLE 1 An unstretched film having a thickness of 40 μm was prepared in Example 1, and the unstretched film was then vertically stretched by one.
Sequential biaxial stretching of 2.1 times at 30 ° C. and 2.0 times at 130 ° C. in the transverse direction is performed, and heat setting is further performed at 230 ° C. for 30 seconds to form a biaxially oriented film having a thickness of 9.0 μm. A polyester film was obtained in exactly the same manner as in Example 1, except that the coating solution applied to the film surface (A) side was changed as follows.

Composition of coating liquid applied to film surface (A): 1.5 wt% solution of acrylic resin (Primal AC-61 manufactured by Nippon Acrylic Chemical Co., Ltd.) 80.0 parts Polyoxyethylene nonyl phenyl ether (Nippon Oil & Fats) 20.0 parts of a 1.5 wt% solution of NS240 (manufactured by Co., Ltd.) The coating amount is 3.0 g / m ² in a wet state.

Table 1 shows the properties of the obtained polyester film and the magnetic recording medium having a magnetic layer provided on the surface (A) side of the film.

[0099]

Comparative Example 2 A polyester film was obtained in the same manner as in Example 1, except that the coating liquid applied to the film surface (A) side was changed as follows.

Composition of coating liquid applied to film surface (A): 95.0 parts of a 15 wt% solution of acrylic-polyester resin (Pesthresin SH551A manufactured by Takamatsu Oil & Fat Co., Ltd.) 95.0 parts Polyoxyethylene nonylphenyl ether (Nippon Oil & Fat Co., Ltd.) 5.0 parts of a 15 wt% solution of NS208.5) (manufactured by NS208.5). The coating amount is 10.0 g / m ² in a wet state.

Table 1 shows the properties of the obtained polyester film and a magnetic recording medium having a magnetic layer provided on the surface (A) side of the film.

[0102]

[Table 1]

[0103]

According to the present invention, it is possible to provide a polyester film useful for producing a magnetic recording medium having excellent magnetic layer surface running properties and electromagnetic conversion characteristics, particularly a metal thin film magnetic recording medium suitable for long-time recording. it can.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuhiro Saeki 3-37-19 Koyama, Sagamihara-shi, Kanagawa Teijin Limited Sagamihara Research Center (58) Field surveyed (Int. Cl. ⁶ , DB name) B32B 1 / 00-35/00 C08J 7/04-7/06 B05D 1/00-7/26 G11B 5/704

Claims (8)

(57) [Claims] 1. A polyester film having a surface coated with a primer layer for a magnetic layer made of a continuous thin film, wherein the surface of the continuous thin film is made of only a resin having a height of 5 nm or less and forming the thin film. 5.0 × 10 ⁷ micro-projections
5.0 in a proportion of × 10 ¹³ pieces / mm ^2, very small surface roughness Ra ^s of the portion that does not include microprotrusions of the continuous film is 1.5
0 nm or less, and the surface roughness Ra of the continuous thin film is 1 to 1
0 nm, and the continuous thin film is heated to 160 ° C.
A polyester film for a magnetic recording medium, characterized in that the rate of precipitation of polyester oligomer microcrystals on a thin film can be suppressed to 0.8% or less when heated for 5 minutes. 2. A longitudinal yan of a polyester film.
Rate (E_MD: Kg / mm ^Two) And the Young's modulus in the width direction (E_TD:
kg / mm^Two) Is expressed by the following formulas (1) to (3)._MD ≧ 550kg / mm^Two ... (1) E_TD ≧ 550kg / mm^Two ... (2) (E_MD+ E_TD) ≧ 1150kg / mm^Two ... (3) is satisfied, and further processed at 105 ° C. in the width direction for 30 minutes.
Heat shrinkage (%) is in the range of 1.0 to 3.5%
The polyester film for a magnetic recording medium according to claim 1,
M 3. The polyester film for a magnetic recording medium according to claim 1, wherein the resin forming the continuous thin film of the magnetic layer primer layer is at least one resin selected from an acrylic resin, a polyester resin and an acryl-polyester resin. 4. A continuous thin film for forming a smooth surface is coated on another surface of the polyester film, the continuous thin film contains a cellulose resin and fine particles having an average particle diameter of 0.15 μm or less, and The polyester film for a magnetic recording medium according to claim 1 or 2, wherein the roughness Ra is 2 to 10 nm. 5. The polyester film for a magnetic recording medium according to claim 3, wherein the binder of the fine particles is at least one resin selected from an acrylic resin, a polyester resin, and an acryl-polyester resin. 6. The polyester film for a magnetic recording medium according to claim 1, wherein the polyester is a polyester produced using an organic titanium compound as a polymerization catalyst. 7. Polyester is polyethylene-2,6-
7. The polyester film for a magnetic recording medium according to claim 1, which is naphthalate. 8. The polyester film for a magnetic recording medium according to claim 1, wherein the polyester is polyethylene terephthalate.