JPH069809A - Polyester film for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a polyester film having excellent traveling property, electromagnetic conversion characteristics, storage durability and especially useful for production of a metallic thin film magnetic recording medium suitable for long time recording. CONSTITUTION:In the polyester film for the magnetic recording medium, a primer (continuous thin film) for a magnetic layer is provided on the surface of a polyester film having >=1350kg/mm<2> sum of Young's modulus in biaxial directions and 1-3.5% thermal shrinkage at 105 deg.C and minute projections (A) consisting of fine particles having <=0.1mum average particle diameter as a nucleus and a resin as a binder and minute projections (B) consisting only the resin are formed in the thin film and the minute projections (A) have height of <=13nm and exists in a ratio of 1.0X10<4> to 1.0X10<8>/mm<2> and the minute projections (B) have >=0.30mum maximum long diameter and exists in a ratio of >=1.0X10/mm<2> and <1.0X10<4>/mm<2> and minute surface roughness RaS of continuous thin film part by the only resin is <=1.50nm and surface roughness Ra of the continuous thin film is 1-10nm.

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 a magnetic recording medium excellent in running properties, electromagnetic conversion characteristics, storage durability, etc. The present invention relates to a polyester film useful for manufacturing.

[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 non-magnetic support by a physical deposition method such as vacuum deposition or sputtering or a plating method is known. . For example, a magnetic tape on which Co is vapor-deposited (Japanese Patent Laid-Open No. 54-147010),
Perpendicular magnetic recording medium using Co--Cr alloy
-134706) and the like are 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, and nevertheless the magnetic recording layer has a thickness of 3 μm.
There is an advantage that performance equal to or higher than that of a coating type magnetic recording medium having a thickness of μm or more (a magnetic recording medium obtained by mixing a magnetic substance powder with an organic polymer binder and coating it on a non-magnetic support) is obtained.

By the way, it is thought that the magnetic properties such as the coercive force Hc or the squareness ratio of the hysteresis loop, which are the static properties of the magnetic recording medium, do not depend much on the surface state of the non-magnetic support used. As an example of such an idea, US Pat. No. 3,787,327 discloses a Co—Cr multilayer structure formed by vacuum deposition.

However, in the metal thin film type magnetic recording medium, the thickness of 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 is as it is. It is considered to be a disadvantage that it causes noise.

From the viewpoint of noise, it is preferable that the surface state of the non-magnetic 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 will be poor, and the blocking phenomenon will occur, and it will not be a product. The film surface is required to be rough. Thus, the surface of the non-magnetic support is required to be smooth from the viewpoint of electromagnetic conversion characteristics, while it is required to be rough from the viewpoint of handleability. Therefore, it is necessary to satisfy both of these contradictory properties at the same time.

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

In order to improve this defect, Japanese Patent Publication No. 62-62
No. 30105 discloses that fine projections are formed on the film surface using fine particles, a water-soluble resin and a silane coupling agent. In addition, Japanese Examined Japanese Patent Publication Sho 62-301
No. 06 and JP-A-59-229316 propose that fine projections are formed on the film surface using fine particles and a water-soluble resin. However, in all of these, the fine particles are present in the trapezoidal projections of the water-soluble resin, and the fine particles are not uniformly present on the film surface. In addition, Japanese Patent Publication No. 1-344456 proposes that a discontinuous film of a water-soluble polymer and fine particles that form protrusions higher than that are independently adhered to the film surface. However, this is inferior in the uniformity on the film surface because the projections are discontinuous films and the fine particles are not uniformly dispersed.

Further, as described in Japanese Patent Publication No. 27733/1990, the metal thin film type magnetic recording medium has a base film in which the energy of vapor such as metal ions, an evaporation source and other high temperature parts in the base film are formed. The temperature rises by receiving radiant energy and the like, and evaporation and precipitation of the oligomer occurs. If the amount of this oligomer is too large, the flatness of the film surface is impaired, which is not preferable.
It is preferable that the oligomer is appropriately precipitated as described in JP-A No. 33-33. However, the polyamide resin, the fibrous resin, the epoxy resin, the urethane resin and the silicon resin, which are exemplified in Japanese Patent Publication No. 27733/1990, are difficult to secure the flatness of the coating film, and particularly the stretching step in the production of the polyester film. When a cross-linked polymer thin film is formed on the film surface on the way and a surface having a liquid or granular pattern is not formed in the subsequent stretching step, the obtained film surface becomes a wavy wrinkled surface or an earthworm-shaped surface. It becomes a surface having protrusions, and flatness is impaired.

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

However, even with a tape using such a film, when the tape thickness is reduced to increase the recording / reproducing time, problems occur in running property and durability. That is, when the magnetic recording tape is repeatedly run, there is a problem that the end portion of the tape is damaged and deformed into a wakame shape to impair the characteristics of the tape. Also, when a metal thin film is formed on this film support, the support film curls and the tape bends when the tape is used in the subsequent magnetic recording tape forming process or cassette. There is a problem that the magnetic head does not come into contact well, output is not output, and tape running becomes unstable.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the drawbacks of the prior art and to manufacture a magnetic recording medium excellent in running property, electromagnetic conversion characteristics, etc., particularly a metal thin film magnetic recording medium suitable for long-time recording. To provide a useful polyester film.

[0012]

The present invention has the following constitution in order to achieve the above object. A polyester film having a magnetic layer primer made of a continuous thin film coated on the surface thereof, wherein the polyester film has a Young's modulus (E _MD : kg / mm ² ) in the longitudinal direction and a Young's modulus (E _{MD in the} width direction). _TD : kg / mm ² ) is the following equations (1) to (3) E _MD ≧ 550 kg / mm ² (1) E _TD ≧ 550 kg / mm ² (2) E _MD + E _TD ≧ 1350 kg / mm ² ( 3) is satisfied, the heat shrinkage percentage (%) in the width direction when treated at 105 ° C. for 30 minutes is in the range of 1.0 to 3.5%, and the continuous thin film has an average grain size of 0. A microprojection (A) having fine particles of 1 μm or less as a nucleus and a resin as a binder and a microprojection (B) of only the resin are formed, and the microprojection (A) has a height of 13 nm or less, 1.0 x 1
It exists in a ratio of 0 ^{4 to} 1.0 × 10 ⁸ pieces / mm ² , and the fine protrusions (B) have a maximum major axis of 0.30 μm or less and 1.0.
It exists in a ratio of × 10 pieces / mm ² or more and 1.0 × 10 ⁴ pieces / mm ^{2 or} less, and the fine surface roughness Ra of the continuous thin film portion made of only the resin is 1.50 nm or less. The surface roughness Ra is 1 to 10 nm, and when the film is heated in air at 160 ° C. for 5 minutes, the deposition rate of polyester oligomer microcrystals on the film surface can be suppressed to 0.8% or less. A polyester film for a magnetic recording medium, which is characterized in that

The polyester constituting the film of the present invention is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. Preferred specific examples of such polyesters include polyethylene terephthalate,
Examples include polyethylene isophthalate, polytetramethylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), polyethylene-2,6-naphthalene dicarboxylate, and the like. Copolymers of these or other resins with a small proportion thereof. Also includes blends with. Of these, polyethylene-2,6-naphthalate is particularly preferable.

The polyester can be produced by a conventionally known method. For example, polyethylene-2,6-naphthalate is obtained by subjecting 2,6-naphthalenedicarboxylic acid and ethylene glycol to an esterification reaction, or 2,6-naphthalenedicarboxylic acid dimethyl ester and an ethylene glycol by transesterification reaction, and then a reaction product. Can be produced by a polycondensation method. At that time, a known catalyst can be used, but it is preferable to use an organotitanium compound as a catalyst for the polycondensation reaction from the viewpoint of film characteristics.

Examples of the organic titanium compound include those described in JP-A-63-278927. More specifically, titanium alcoholate or organic acid salt, a reaction product of a tetraalkyl titanate and an aromatic polyvalent carboxylic acid or an anhydride thereof, and the like can be exemplified, and preferable specific examples include titanium tetrabutoxide, titanium isopropoxide, and titanium oxalate. , Titanium acetate, titanium benzoate, titanium trimellitate, a reaction product of tetrabutyl titanate and trimellitic anhydride, and the like. The amount of the organic titanium compound used is preferably such that the titanium atom is 3 to 12 mg atom% with respect to the acid component constituting the polyester.

In the polyester, a surface-roughening substance well known in the art, such as calcium carbonate, kaolinite, titanium dioxide, silica-alumina, etc., and other additives are included within a range not impairing the object of the present invention. Can be included.

The polyester film of the present invention is
Young's modulus in the longitudinal direction is 550 kg / mm ²Or more, preferably
650 kg / mm²Above, Young's modulus in the width direction is 550
kg / mm²Above, preferably 650kg / mm²Is over,
And the sum of Young's modulus in both directions is 1350kg / mm²that's all,
Preferably 1400 kg / mm²It must be above. This
Young's modulus in the longitudinal direction is 550 kg / mm²If less than
When the magnetic tape is instantly subjected to strong stress, the tape
It is not preferable because it stretches and deforms. In addition, Young in the width direction
Rate is 550kg / mm²If less than, run the magnetic tape
Repeatedly, the end of the tape was damaged and turned into a seaweed.
It is not preferable because it forms.

The polyester film of the present invention is
Further, the heat shrinkage rate when treated at 105 ° C in the width direction for 30 minutes is 1.0 to 3.5%, preferably 1.0 to 3.0.
Must be%. If this heat shrinkage ratio is less than 1.0% or more than 3.5%, curling when formed into a magnetic tape becomes significant, which is not preferable.

The polyester film can be manufactured by 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, cooled and solidified to obtain an unstretched film, and the unstretched film is uniaxially (lengthwise). (Tg-10) ~
Temperature of (Tg + 70) ° C (however, Tg: polyethylene-
2,6-naphthalate (glass transition temperature) at a predetermined ratio, and then Tg in a direction perpendicular to the above-mentioned stretching direction (when the first stage stretching is the longitudinal direction, the second stage stretching is the transverse direction).
It can be produced by a method of stretching at a predetermined ratio at a temperature of (° C) to (Tg + 70) ° C and then heat-setting. At that time, the draw ratio, the draw temperature, the heat setting conditions and the like are selected and determined from the characteristics of the film. The area draw 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 treatment 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 machine direction and the transverse direction is not limited to once, and the machine direction-transverse stretching can be carried out by several times,
The number of times is not limited. For example, in order to further improve the mechanical properties, the heat setting temperature of the biaxially stretched film before the heat setting treatment is (Tg + 20) ° C.
Heat setting at (Tg + 70) ° C., further stretching in the machine or transverse direction at a temperature 10 to 40 ° C. higher than this heat setting temperature, and then further stretching in the transverse or longitudinal direction at a temperature 20 to 50 ° C. higher than this temperature. In the case of the longitudinal direction, the draw ratio is 5.0 to 6.
The overall draw ratio in the transverse direction can be set to 9 times and 5.0 to 6.9 times. The film thickness after stretch orientation is generally 2
˜100 μm, preferably 3 to 50 μm.

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

In the present invention, a continuous thin film is applied as a primer for the magnetic layer on the surface of the polyester film. Then, a magnetic layer, particularly a ferromagnetic metal thin film layer, is formed on this thin film. On the surface of this continuous thin film, there are 1.a microprotrusions (A) having fine particles having an average particle size of 0.1 μm or less, preferably 0.05 μm or less as a nucleus and a resin as a binder.
0 × 10 ^{4 to} 1.0 × 10 ⁸ pieces / mm ² , preferably 1.
It exists at a rate of 0 × 10 ^{5 to} 8.0 × 10 ⁷ pieces / mm ² . The height of the fine protrusions (A) is 13 nm or less, preferably 12 nm or less. Further, the surface of the continuous thin film has a background microprotrusion (B) of 1.0 × 10 4 pieces / mm ² or more and less than 1.0 × 10 ⁴ pieces / mm ² , preferably 1.0 due to the binder resin alone. X 10 pieces / mm ^{2 to} 5.0 x 10 ³
It exists in the ratio of individual pieces / mm ² . The maximum length of the minute protrusions (B) is 0.30 μm or less, preferably 0.20 μm.
m or less.

In the present invention, the fine surface roughness Ra of the continuous thin film portion (background portion) made of only the resin of the continuous thin film is 1.
It is 50 nm or less, preferably 1.40 nm or less. Then, the surface roughness (total surface roughness) Ra of the continuous thin film.
Should be 1 to 10 nm (0.001 to 0.010 μm), preferably 1 to 7 nm (0.001 to 0.007 μm). Further, when this film was continuously heated in air at 160 ° C. for 5 minutes, the precipitation rate of the polyester oligomer microcrystals on the surface of the polyester film was 0.8%.
Hereafter, it is necessary to apply a continuous thin film capable of being suppressed to preferably 0.75% or less, more preferably 0.6% or less.

The fine particles in the present invention include polystyrene, polymethylmethacrylate, methylmethacrylate copolymer, methylmethacrylate copolymer crosslinked product,
Organic fine particles such as polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, and benzoguanamine resin, silica, alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, barium sulfate, etc. Any of such inorganic fine particles may be used. These may be made into an aqueous dispersion using an emulsifier or the like, or may be fine powders which can be added to the aqueous liquid.

As the resin (binder) for bonding the fine particles to the surface of the polyester film, alkyd resin, unsaturated polyester resin, saturated polyester resin, phenol resin, amino resin, vinyl acetate resin, vinyl chloride-vinyl acetate Examples thereof include polymer resins, acrylic resins, acrylic-polyester resins, and the like. These resins may be a homopolymer, a copolymer, or a mixture.

The acrylic resin is, for example, an acrylic acid ester (as the alcohol residue, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group,
Isobutyl group, t-butyl group, 2-ethylhexyl group,
Examples thereof include cyclohexyl group, phenyl group, benzyl group and phenylethyl group); methacrylic acid ester (alcohol residue is the same as above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2
-Hydroxy-containing monomers such as hydroxypropyl acrylate and 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-dimethylol Amide group-containing monomers such as acrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, and 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, allyl glycidyl ether; styrene sulfonic acid, vinyl sulfo Monomers containing sulfonic acid groups or salts thereof such as acids and salts thereof (eg sodium salt, potassium salt, ammonium salt, etc.); crotonic acid, itaconic acid, acrylic acid, maleic acid, fumaric acid, and their Monomers containing carboxyl groups such as salts (eg sodium salts, potassium salts, ammonium salts etc.) or salts thereof; monomers containing anhydrides such as maleic anhydride, 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,
It is made from a combination of monomers such as methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate, vinyl chloride, and (meth) acrylic monomers such as acrylic acid derivatives and methacrylic acid derivatives. Those containing 50 mol% or more of the above component are preferable, and those containing the component of methyl methacrylate are particularly preferable.

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

Examples of the acid component constituting the polyester resin include terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid and 2,6-
Naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2
Examples include polyvalent carboxylic acids such as potassium sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid and trimellitic acid monopotassium 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, p
-Xylylene glycol, ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, dimethylolpropionic acid A polyvalent hydroxy compound such as potassium can be exemplified. A polyester resin can be prepared from these compounds by a conventional method. When making an aqueous coating solution, 5
-It is preferable to use a polyester resin containing a 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.

Furthermore, the acrylic-polyester resin is used in the sense of including an acrylic-modified polyester resin and a polyester-modified acrylic resin, and the acrylic-resin component and the polyester-resin component are bonded to each other. Type, block type, etc. are included. For the acrylic-polyester resin, for example, a radical initiator is added to both ends of the polyester resin to polymerize the acrylic monomer, or a radical initiator is attached to the side chain of the polyester resin to polymerize the acrylic monomer. It can be produced by, for example, adding a hydroxyl group to the side chain of an acrylic resin and reacting it with a polyester having an isocyanate group or a carboxyl group at the end to form a comb polymer. The polyester resin used in that case preferably does not contain a sulfonyloxy group in the molecule.

As a method for forming fine projections (A) having fine particles as cores and a resin as a binder on the surface of a polyester film, a resin coating liquid containing fine particles, preferably an aqueous coating liquid, is used to produce the polyester film. A method of applying and drying and solidifying the film surface in the inside, or a method of applying and drying and solidifying a resin coating liquid containing fine particles in a biaxially oriented polyester film can be adopted.
The former is preferable. It is all right to include a surfactant for facilitating the application in these coating solutions.

The ratio of the fine particles to the resin (binder) is preferably determined by designing the above-mentioned surface characteristics, the fine particles are 1 to 40% by weight, and the binder resin is 20 to 40% by weight based on the total solid content. It is preferably 95% by weight. When the amount of the fine particles is too small, it is not possible to uniformly apply a predetermined amount of protrusions to the coating film, while when the amount of the fine particles is too large, the dispersibility is deteriorated and it is difficult to uniformly impart a predetermined amount of protrusions. When the amount of the binder resin is too small, the adhesion of the coating film to the polyester film is lowered, while when the amount is too large, the blocking resistance is lowered.

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.

Among the methods described above, from the viewpoint that the effect of suppressing the precipitation of the oligomer is large while ensuring the flatness of the background portion of the continuous thin film, the binder is acrylic resin and polyester resin or aryl- A method of applying the resin solution containing fine particles by a roll coating method using a polyester resin is preferable.

When a magnetic layer, particularly a metal thin film magnetic layer, is provided on the continuous thin film of the base film having the continuous thin film thus formed, the noise is drastically reduced and the noise level is remarkably excellent. It is possible to obtain a magnetic recording medium having excellent running property and storage durability and suitable for long-time recording.

In the present invention, it is preferable to coat a continuous thin film for forming a slippery 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 the primer for the magnetic layer is provided. This thin film has a cellulosic resin and an average particle size of 0.15 μm or less, preferably 0.0
It contains fine particles of 1 to 0.1 μm and has a surface roughness Ra.
Is 2 to 10 nm (0.002 to 0.01 μm), preferably 3 to 9 nm (0.003 to 0.009 μm).

Examples of the cellulose resin include ethyl cellulose, methyl cellulose, acetyl cellulose, acetoacetyl cellulose, nitrocellulose, carboxylated cellulose, carboxymethyl cellulose, cellulose acetate butyrate and the like.
By using this cellulose-based resin, it is possible to form a large number of fine pleats on the surface of the coating film.

The fine particles are polystyrene,
Organic fine particles such as polymethylmethacrylate, methylmethacrylate copolymer, methylmethacrylate 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 and barium sulfate may be used. These may be made into an aqueous dispersion using an emulsifier or the like,
It may also be a fine powder that can be added to the aqueous liquid.

The cellulosic resin and the fine particles have a function of promoting uniform formation of fine protrusions of the coating film itself and a reinforcing action of the coating film by the fine particles themselves, and further have a blocking resistance and a frictional force of the coating film forming resin. Excellent slipperiness is given to the film in combination with the effect on the reduction property and the improvement of scratch resistance by the synergistic effect of both.

The resin forming the thin film having a smooth surface is preferably one having excellent blocking resistance, frictional force reduction property and the like, and preferred examples thereof include acrylic resin, polyester resin and acrylic-polyester resin. For the description of these resins, the description of the acrylic resin, the polyester resin, and the acrylic-polyester resin described above as the resin used for forming the magnetic layer primer can be used as they are.

The composition ratio of the components forming the easy-sliding surface, that is, the thin film forming resin (component a), the cellulosic resin (component b) and the fine particles (component c) is preferably determined by designing the surface characteristics, and the total solid content. Per component a is 30 to 80% by weight, component b is 1 to 50% by weight, and component c is 5 to 40% by weight
Is preferred. If the amount of the component a is too small, the adhesion of the coating film to the polyester film will decrease, while if it is too large, the blocking resistance and slipperiness will decrease. If the amount of component b is too small, the pleats of the coating film are reduced and the workability is lowered, while if it is too large, the surface is too rough. If the amount of component c is too small, the slipperiness decreases, while if it is too large, the particles tend to fall off from the coating film.

The formation of the coating film in the present invention may be carried out after the polyester film is produced or during the production of the polyester film, but it is preferably carried out in the process of producing the polyester film. For example, it is preferable to apply an aqueous coating liquid to the surface of the polyester film before the crystal orientation is completed.

Here, the polyester film before the crystal orientation is completed is an unstretched film obtained by melt-extruding polyester into a film as it is, and the unstretched film is oriented in either the longitudinal direction or the transverse direction. Uniaxially stretched film, and further biaxially stretched film, but a biaxially stretched film (finally in the longitudinal direction and / or the transverse direction) that has a low-magnification stretch in at least one direction and requires a stretch orientation in that direction. Biaxially stretched film) before re-stretching in the direction to complete the oriented crystallization.

The film of the present invention is preferably an unstretched or at least uniaxially stretched film before completion of crystal orientation, and the aqueous coating solution of the above composition is applied to the film.
Then, it is manufactured by a so-called in-line coating method in which longitudinal stretching and / or transverse stretching and heat setting are performed. At that time, in order to enable the coating film to be smoothly applied to the surface of the polyester film before the oriented crystals are completed, the film surface is subjected to corona discharge treatment as a pretreatment, or together with the coating composition, this It is preferable to use a chemically inert surfactant together. Such a surfactant can lower the surface tension of the aqueous coating solution to 40 dyne / cm or less and accelerates wetting of the polyester film. For example, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, Examples thereof 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 an antistatic agent, an ultraviolet absorber and a lubricant can be mixed in a range that does not eliminate the effects of the present invention.

In the present invention, the solid content concentration of the coating liquid, especially the aqueous coating liquid is usually 30% by weight or less, preferably 15% by weight or less. This viscosity is usually 100 centipoise (cp)
s) or less, preferably 20 cps or less. The coating amount is preferably about 0.5 to 20 g, more preferably about 1 to 10 g per 1 m ² of the running film. In other words, in the finally obtained biaxially oriented film, about 0.001 to 1 g, more preferably about 0.005 to 1 g / m ^{2 on} one surface of the film.
A solids content of 0.3 g is preferred.

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 above aqueous coating solution is applied to a film immediately after being longitudinally uniaxially stretched, and then the film is guided to a tenter for transverse stretching and heat setting. At that time, the coating material is expanded in its area in the state of an unsolidified coating film as it is stretched, and is heated to volatilize water to form a thin solid continuous coating layer on the biaxially stretched film surface. It is converted and firmly fixed to the biaxially stretched film surface. The above heat treatment is preferably about 1 to about 6 at a temperature of about 80 ° C to about 250 ° C.
It is performed for 0 seconds.

The production of a metal thin film magnetic recording medium using the polyester film of the present invention is carried out by a method known per se,
For example, JP-A-54-147010 and JP-A-52-52
It can be carried out by the method described in Japanese Patent No. 134706, specifically, a vacuum vapor deposition method, an ion plating method,
The sputtering method can be preferably used.

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

Various properties herein are measured as follows.

(1) Intrinsic viscosity [η] Obtained from a value measured at 35 ° C. in an orthochlorophenol solvent.

(2) Average particle diameter Particles having an average particle diameter of less than 0.1 μm are indicated by the “equivalent spherical diameter” of the particles at a point of 50% by weight of all particles determined by the light scattering method.

Particles having an average particle size of 0.1 μm or more are indicated by the “equivalent spherical diameter” of particles at a point of 50% by weight of all particles, which is determined by the light transmission centrifugal sedimentation method.

(3) Number of protrusions The number of protrusions on the film surface is measured by a scanning electron microscope. That is, the fine projections having fine particles as the core have a magnification of 20,000 to 50,000 times, and the fine projections made of resin alone have a magnification of 5,000 to 2 times.
Evaluate at 10,000 times.

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

(5) Minute surface roughness Ra ^{s A} portion without minute projections is selected from the range of 2 μm × 2 μm measured on the same sample as described above, and a measurement length is measured from the film surface roughness curve in the direction of its center line. When the roughness curve is represented by Y = f (x) with the center line of this portion being the X axis and the direction of the vertical magnification being the Y axis, the value given by the following equation Expressed in nm.

[0056]

[Equation 1]

In practice, this measurement is based on the value obtained for the length of 0.4 to 1.2 μm in the part where there are no fine protrusions as 1.
The average value of the measured values of 10 times is defined as the fine surface roughness Ra.

(6) Surface Roughness Ra (Center Line Average) According to JIS B0601, a high precision surface roughness meter SE-3FAT manufactured by Kosaka Laboratory Ltd. is used to measure the needle Radius 2μ
m, load 30 mg, magnification 200,000 times, cutoff 0.0
A chart is placed under the condition of 8 mm, and a portion having a measurement length L is extracted from the film surface roughness curve in the direction of its center line. The center line of this extracted portion is taken as the X axis and the longitudinal magnification direction is taken 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 2]

This measurement was carried out four times with a reference length of 1.25 mm, and is represented by the average value.

(7) Coefficient of Friction (Film Slippery) According to ASTM D1894-63, the coefficient of static friction (μs) is measured using a slippery measuring device manufactured by Toyo Tester. However, the thread plate is a glass plate and the load is 1
kg. Film slippers are judged according to the following criteria. ◯: Good (μs less than 0.6) Δ: Slightly bad (μs 0.6 to 0.8) ×: Bad (μs 0.8 or more)

(8) Precipitation rate of oligomer After fixing the film on a wooden frame and holding it in a hot air circulation (air) type dryer at 160 ° C. for 5 minutes, aluminum was vapor-deposited on the surface of the film, and a differential interference optical microscope was used. Take a photo of the film surface with. The oligomer deposition rate is evaluated as a percentage of the total area occupied by oligomers (imaged in white spots) on this photograph with respect to the total area of the photograph.

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

(10) Heat shrinkage rate The film is cut into a strip shape having a width of 10 mm and a length of 600 mm, and marking points at intervals of 500 mm are attached. This sample is subjected to gear open at 105 ° C. for 30 minutes under no tension and then cooled to room temperature. The heat shrinkage rate is calculated from the dimensional change before and after the heat treatment. Dimension measurement is done by MITUTOYO's micro dimension measuring device (PROFILE PROJECTOR MODEL PJ321).
F) is used.

(11) Electromagnetic conversion characteristics Using a vacuum vapor deposition device, a cylindrical can having a diameter of 1 m was filled with a film.
5 × 10 ^-Five(Torr) oxygen minimum input
Co-Ni (containing 20 wt% Ni) alloy at an elevation angle of 43 degrees
Is obliquely vapor-deposited to a film thickness of about 1300 Å,
Create pull tape.

This tape was processed to a width of 8 mm to form a vapor deposition tape, and an amorphous head having a gap length of 0.2 μm provided a white peak of 0.45 μm and a bandwidth of 9 (MHz).
C / N (initial value) are compared.

Judgment is made from this C / N according to the following criteria. ◯: +0.0 dB or more with respect to the reference value Δ: 〃 −0.5 dB to +0.0 dB ×: 〃 less than −0.5 dB

After repeating recording / reproducing at a tape running speed of 85 cm / min at 40 ° C. and 80% RH, 250th C
/ N (durability) is compared.

Judgment is made from this C / N according to the following criteria. ◯: +0.0 dB or more relative to the reference value Δ: 〃 −1.0 dB to +0.0 dB ×: 〃 less than −1.0 dB

(12) Still characteristics A video signal of 4.2 MHz is recorded on the above vapor deposition tape, and the time until the reproduction output is attenuated to 50% is measured. Judgment is made according to the following criteria by this time. ◯: Attenuation time of 100% or more at 50% Δ: 〃 50 minutes to 100 minutes ×: 〃 less than 50 minutes

(13) Shuttle characteristic A video signal of 4.2 MHz was recorded on the above vapor deposition tape, and the tape running speed was 41 m under the conditions of 25 ° C. and 50% RH.
/ Min and the rewind speed of 41 m / min are set as one time, and the output fluctuation is examined after repeating a total of 200 times. Judgment is made according to the following criteria from this output fluctuation. A: Output fluctuation after repeating 200 times is 0 dB to -0.3.
dB ◯: Output fluctuation after repeating 200 times is −0.3 dB to −
0.6 dB Δ: Output fluctuation after repeating 200 times is −0.6 dB to −
1.5 dB ×: Output fluctuation after repeating 200 times is −1.5 dB or more.

(14) Curl A 500 × 500 mm square sample was cut out from a magnetic recording tape stock, and the curl was judged according to the following criteria. XX: Completely cylindrical shape ×: Part of the cylinder is open Δ: The opening is wider than the above,
The diameter of the circle can be the longest part of the side surface ○: The opening is wider than the above, and the longest part of the side surface cannot be the diameter of the circle ◎: No curl or almost no curl

[0073]

EXAMPLES The present invention will be further described below with reference to examples. In addition, "part" in an example is a weight part.

[0074]

Example 1 To a mixture of 100 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester and 60 parts of ethylene glycol, 0.025 part of manganese acetate / tetrahydrate and 0.005 part of sodium acetate / trihydrate were added. The transesterification reaction was carried out while gradually raising the temperature from 150 ° C. When the transesterification rate reached 95%, a glycol solution of a phosphorus compound prepared by previously reacting 25 parts of trimethyl phosphate and 75 parts of ethylene glycol as a stabilizer was prepared.
After adding 069 parts and sufficiently stirring, 0.84 parts of trimellitic anhydride and 0.65 parts of tetrabutyl titanate were reacted in 2.5 parts of ethylene glycol (titanium content is 11% by weight) 0.014 Parts were added. Then, the reaction product was transferred to a polymerization reactor and subjected to high temperature vacuum (final internal temperature 29
Polycondensation reaction was performed at 5 ° C.) to obtain polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.57.

This polyethylene-2,6-naphthalate was melt-extruded according to a conventional method and rapidly cooled to prepare an unstretched film having a thickness of 160 μm. Then, the unstretched film was lengthwise (longitudinal) at 130 ° C. 4. Sequential biaxial stretching of 9 times and 5.2 times at 135 ° C. in the width direction (transverse direction) was performed, and heat setting was further performed at 200 ° C. for 6 seconds to prepare a biaxially oriented film having a thickness of 6.3 μm. At this time, the following composition and coating liquid were applied to the uniaxially stretched film before transverse stretching on the surfaces (A) and (B) of the film by a roll coating method. The surface (A) is the surface on the side where the magnetic layer is formed, and the surface (B) is a slippery surface.

Composition of coating liquid applied on the film surface (A): 1.5 wt% solution of aqueous emulsion prepared by the following method 82.4 parts Polymethylmethacrylate fine particles (Nippon Shokubai Kagaku Kogyo Co., Ltd. Eposter MA) 1.5 parts by weight of a 1.5 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 15 parts by weight The coating amount is 2.7 g / m ^{2 when} wet.

[Synthesis of Aqueous Emulsion] The acid components are terephthalic acid (45 mol%) and isophthalic acid (55 mol).
%) And the glycol component is diethylene glycol (100 parts of intrinsic viscosity 0.40 measured in o-chlorophenol at 35 ° C.) were dissolved in 900 parts of tetrahydrofuran while heating at 64 ° C. under normal pressure. Then, 900 parts of deionized water was gradually added with high speed stirring. After the total amount was added, the mixture was heated to 80 ° C. again to evaporate and remove tetrahydrofuran, to obtain a 10 wt% polyester aqueous dispersion. This aqueous dispersion is subjected to 6 under normal pressure.
Heat to 0 ° C. and add 1 part ammonium persulfate. Then, the mixture was heated to 80 ° C., and a mixture of 90 parts of methyl methacrylate, 39 parts of ethyl acrylate, 20 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 was gradually added. After the addition was completed, the reaction was continued for another 3 hours and then cooled to room temperature.

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

Composition of coating liquid applied to the film surface (B): 2.8 wt% solution of the above aqueous emulsion 61.0 parts Cellulose resin (methyl cellulose SM-15 manufactured by Shin-Etsu Chemical Co., Ltd.) 2.8 wt% Solution 20.0 parts Polymethylmethacrylate fine particles (Nippon Shokubai Kagaku Kogyo Co., Ltd. Eposta-MA) 2.8 wt% solution 9.0 parts (However, the average particle diameter of these fine particles is 0.035 μm) Polyoxy 2.8 wt% solution of ethylene nonyl phenyl ether (NS208.5, manufactured by NOF CORPORATION) 10.0 parts Wet coating amount is 3.4 g / m ² .

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

[0081]

[Example 2] The transesterification rate in Example 1 was 9
At the time of 0%, an ethylene glycol slurry of silicon dioxide having an average particle size of 0.10 μm (10% of silicon dioxide
wt% / ethylene glycol slurry) (0.20 part) and the coating liquid applied to the film surface (A) was changed as follows, to obtain a polyester film.

Composition of coating liquid applied to film surface (A): 1.5 wt% solution of polyester resin (Polyester WR961 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 40.0 parts Acrylic resin (Nippon Pure Chemical Co., Ltd. ) DULIMER AT613) 1.5 wt% solution 42.0 parts Silicon dioxide 1.5 wt% solution having an average particle size of 0.01 μm 3.0 parts Polyoxyethylene nonyl phenyl ether (NS 208.5 manufactured by NOF CORPORATION) 2) 1.5 wt% solution of 1) 15.0 parts Wet coating amount is 2.7 g / m ² .

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

[0084]

Example 3 The unstretched film obtained in Example 1 was sequentially biaxially stretched 4.0 times in the longitudinal direction at 130 ° C. and 6.5 times in the lateral direction at 135 ° C., and further applied to the film surface (A). A biaxially oriented film having a thickness of 6.1 μm was obtained in exactly the same manner as in Example 1 except that the coating liquid was changed as follows.

Composition of coating liquid applied to the film surface (A): 1.6 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 89.0 parts Silicon dioxide having an average particle diameter of 0.01 μm 1.6 wt% liquid 1.0 part 1.6 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 10.0 parts Coating amount is 2.7 g / m ² by wet.

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

[0087]

[Embodiment 4] In Embodiment 1, at a thickness ratio of 6: 4,
And the average particle size is 0.25μ on the polyester with the thickness ratio 4
An unstretched film having a thickness of 160 μm was prepared in exactly the same manner as in Example 1 except that 0.10 parts of m of calcium carbonate was kneaded using a biaxial extruder.

Then, the unstretched film is longitudinally stretched at 140 ° C.
At 6.0 ° C. and laterally at 135 ° C. at 4.3 × by sequential biaxial stretching and heat setting at 210 ° C. for 10 seconds to obtain a thickness of 6.
A 3 μm biaxially oriented film was prepared. At this time, on the outer surface (A) on the thickness ratio 6 side and the outer surface (B) on the thickness ratio 4 side,
A coating liquid having the following composition was applied by a roll coating method.

Composition of coating liquid applied to the film surface (A): 1.5 wt% solution of polyester resin (Plus Coat Z-461 manufactured by Kyokai Chemical Industry Co., Ltd.) 84.95 parts Dioxide having an average particle diameter of 0.01 μm 1.5 wt% solution of silicon 0.05 part Polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 1.5 wt% solution 15.0 parts Coating weight is 2.7 g / m ² is there.

Composition of coating liquid applied to film surface (B): 2.5 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 63.0 parts Cellulose resin (manufactured by Shin-Etsu Chemical Co., Ltd.) 2.5 wt% solution of methylcellulose SM-15) 18.0 parts Polymethylmethacrylate fine particles (Nippon Shokubai Chemical Co., Ltd. Eposta MA) 2.5 wt% solution 9.0 parts (however, the average of these fine particles The particle size is 0.03 μm) A 2.5 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 10.0 parts The coating amount is 3.4 g / m ² by wet.

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

[0092]

COMPARATIVE EXAMPLE 1 An unstretched film having a thickness of 45 μm was prepared in Example 1, and then the unstretched film was vertically stretched 1
Sequential biaxial stretching of 2.3 times at 30 ° C and 2.1 times at 120 ° C in the transverse direction was performed, and heat setting was further performed at 240 ° C for 30 seconds to prepare a biaxially oriented film with a thickness of 9.3 µm. A polyester film was obtained in exactly 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 on the film surface (A): 1.6 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 42.0 parts Silicon dioxide having an average particle diameter of 0.01 μm 1.6 wt% liquid 48.0 parts 1.6 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 10.0 parts Coating amount is 2.7 g / m ² by wet.

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

[0095]

Comparative Example 2 In Example 3, after obtaining polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.57, the internal temperature was 30.
A biaxially oriented film with a thickness of 6.1 μm was obtained in exactly the same manner as in Example 3 except that the film was melted and held at 0 ° C. under atmospheric pressure for 30 minutes. Further, the composition of the coating liquid applied to the film surface (A) was changed as follows.

Composition of coating liquid applied to film surface (B): 10.0 wt% solution of acrylic-polyester resin (Pesresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 88.8 parts Silicon dioxide having an average particle diameter of 0.01 μm 10.0 wt% liquid 1.2 parts 10.0 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 10.0 parts Coating amount is 2.7 g / m ² by wet.

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

[0098]

Comparative Example 3 A polyester film was obtained in exactly the same manner as in Example 3, except that the composition of the coating liquid applied to the film surface (A) in Example 3 was changed as follows.

Composition of coating liquid applied to the film surface (A): 3.0 wt% solution of polyester resin (Plus Coat Z-461 manufactured by Kyowa Kagaku Co., Ltd.) 85.0 parts Silicon dioxide having an average particle diameter of 0.10 μm 3.0 wt% solution of 5.0 parts Polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 10.0 wt% solution of 10.0 parts Coating amount is 2.7 g / m ² wet. .

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

[0101]

[Table 1]

[0102]

According to the present invention, there is provided a polyester film useful for producing a magnetic recording medium excellent in running properties, electromagnetic conversion characteristics, storage durability, etc., particularly a metal thin film magnetic recording medium suitable for long-time recording. be able to.

[Procedure amendment]

[Submission date] September 14, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

The present invention has the following constitution in order to achieve the above object. A polyester film having a magnetic layer primer made of a continuous thin film coated on its surface, the polyester film having a Young's modulus in the longitudinal direction (E _MD : kg / mm ² ) and a Young's modulus in the width direction (E _MD ). _TD : kg / mm ² ) is the following formula (1)
To (3) E _MD ≧ 550 kg / mm ² (1) E _TD ≧ 550 kg / mm ² (2) E _MD + E _TD ≧ 1350 kg / mm ² (3), and the width direction is 105 ° C. The heat shrinkage (%) when treated for 30 minutes at 1.0 to 3.5%, and the continuous thin film has fine particles having an average particle diameter of 0.1 μm or less as a core and a resin as a binder. The fine protrusions (A) and the fine protrusions (B) made of only the resin are formed, and the height of the fine protrusions (A) is 13 nm or less.
Exists at a rate of 0 ^{4 to} 1.0 × 10 ⁸ pieces / mm ² ,
Further, the minute protrusions (B) have a maximum major axis of 0.30 μm or less and 1.0 × 10 pieces / mm ² or more and 1.0 × 10 ⁴ pieces / mm.
Existence in a ratio of less than ^2, the fine surface roughness Ra ^s of the continuous thin film portion made of only the resin is 1.50 nm or less, the surface roughness Ra of the continuous thin film is 1 to 10 nm, and the continuous thin film Is a polyester film for magnetic recording media, which is capable of suppressing the deposition rate of polyester oligomer microcrystals on the film surface to 0.8% or less when the film is heated in air at 160 ° C. for 5 minutes.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

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 machine direction and the transverse direction is not limited to once, and the machine direction-transverse stretching can be carried out by several times,
The number of times is not limited. For example, in order to further improve the mechanical properties, the heat setting temperature of the biaxially stretched film before the heat setting treatment is (Tg + 20) ° C.
Heat setting at (Tg + 70) ° C., further stretching in the machine or transverse direction at a temperature 10 to 40 ° C. higher than this heat setting temperature, and then further stretching in the transverse or longitudinal direction at a temperature 20 to 50 ° C. higher than this temperature. Then, the total draw ratio in the machine direction is 5.0 to 6.
The overall draw ratio in the transverse direction can be set to 9 times and 5.0 to 6.9 times. The film thickness after stretch orientation is generally 2
˜100 μm, preferably 3 to 50 μm.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

In the present invention, the fine surface roughness Ra ^s of the continuous thin film portion (background portion) of only the resin of the continuous thin film is 1.50 nm or less, preferably 1.40 nm or less. The surface roughness (total surface roughness) Ra of the continuous thin film is 1 to 10 nm (0.001 to 0.010 μm).
m), preferably 1 to 7 nm (0.001 to 0.007)
μm). Furthermore, this film is 160
When continuously heated in air at 5 ° C. for 5 minutes, the precipitation rate of polyester oligomer microcrystals on the surface of the polyester film can be suppressed to 0.8% or less, preferably 0.75% or less, and more preferably 0.6% or less. It is necessary to apply a continuous thin film.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

Among the various methods described above, acrylic resin and polyester resin or acrylic resin are used as the binder from the viewpoint that the effect of suppressing oligomer precipitation is great while securing the flatness of the background portion of the continuous thin film. A method of applying the resin solution containing fine particles by a roll coating method using a polyester resin is preferable.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0057

[Correction method] Change

[Correction content]

Actually, this measurement is performed on a portion without microprojections.
The value obtained for the length of 0.4 to 1.2 microns is 1
Fine surface roughness based on the average of 10 measurements
Ra ^s And

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0075

[Correction method] Change

[Correction content]

This polyethylene-2,6-naphthalate was melt-extruded according to a conventional method and rapidly cooled to prepare an unstretched film having a thickness of 160 μm. Then, the unstretched film was lengthwise (longitudinal) at 130 ° C. 4. Sequential biaxial stretching of 9 times and 5.2 times at 135 ° C. in the width direction (transverse direction) was performed, and heat setting was further performed at 200 ° C. for 6 seconds to prepare a biaxially oriented film having a thickness of 6.3 μm. At this time, a coating solution having the following composition was applied to the uniaxially stretched film before transverse stretching by a roll coating method on the surfaces (A) and (B) of the film. The surface (A) is the surface on the side where the magnetic layer is formed, and the surface (B) is a slippery surface.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0096

[Correction method] Change

[Correction content]

Composition of coating liquid applied on film surface ( A ): 10.0 wt% solution of acrylic-polyester resin (Pesresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 88.8 parts Silicon dioxide having an average particle size of 0.01 μm 10.0 wt% liquid 1.2 parts 10.0 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 10.0 parts Coating amount is 2.7 g / m ² by wet.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0099

[Correction method] Change

[Correction content]

[0099] Coating liquid composition coated on the film surface (A): dioxide 3.0 wt% solution 85.0 parts average particle size 0.10μm polyester resin (GOO Chemical Co., Ltd. PLAS COAT Z-461) 3.0 wt% solution of silicon 5.0 parts 3.0 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 10.0 parts Coating amount is 2.7 g / m ² wet. is there.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B29L 7:00 4F (72) Inventor Sadami Miura 3-37-19 Koyama, Sagamihara City, Kanagawa People Sagamihara Research Center Co., Ltd.

Claims (5)

[Claims] 1. A polyester film having a surface coated with a primer for a magnetic layer comprising a continuous thin film, the polyester film having a Young's modulus in the longitudinal direction (E _MD : kg / mm ² ) and a width direction. Young's modulus ( _ETD : kg /
mm ² ) satisfies the following formulas (1) to (3) E _MD ≧ 550 kg / mm ² (1) E _TD ≧ 550 kg / mm ² (2) E _MD + E _TD ≧ 1350 kg / mm ² (3) Further, the heat shrinkage (%) in the width direction when treated at 105 ° C. for 30 minutes is in the range of 1.0 to 3.5%, and the continuous thin film has an average particle size of 0.1 μm or less. A fine projection (A) having fine particles as a nucleus and a resin as a binder, and a fine projection (B) made of only the resin are formed, and the fine projection (A) has a height of 13 nm or less and 1.0 ×. 1
It exists in a ratio of 0 ^{4 to} 1.0 × 10 ⁸ pieces / mm ² , and the fine protrusions (B) have a maximum major axis of 0.30 μm or less and 1.0.
It exists in a ratio of × 10 pieces / mm ² or more and 1.0 × 10 ⁴ pieces / mm ^{2 or} less, and the fine surface roughness Ra ^s of the continuous thin film portion made of only the resin is 1.50 nm or less. Has a surface roughness Ra of 1 to 10 nm, and the continuous thin film suppresses the precipitation rate of polyester oligomer microcrystals on the film surface to 0.8% or less when the film is heated in air at 160 ° C. for 5 minutes. A polyester film for a magnetic recording medium, which is characterized by being capable of being produced. 2. A continuous thin film for forming a smooth surface is coated on the other surface of the polyester film, and the continuous thin film contains a cellulosic resin and fine particles having an average particle size of 0.15 μm or less, and this surface. The polyester film for a magnetic recording medium according to claim 1, wherein the roughness Ra is 2 to 10 nm. 3. The polyester film for a magnetic recording medium according to claim 1, wherein the binder of the fine particles is at least one resin selected from acrylic resins, polyester resins and acrylic-polyester resins. 4. The polyester film for a magnetic recording medium according to claim 1, wherein the polyester is a polyester produced by using an organic titanium compound as a polymerization catalyst. 5. The polyester is polyethylene-2,6-
The polyester film for a magnetic recording medium according to claim 1, which is naphthalate.