JPH05287101A - Polyester film for magnetic recording media - Google Patents

Abstract

PURPOSE:To provide polyester film which is useful in production of electromagnetic recording film excellent in its traveling properties, electromagnetic transduction properties and storage durability. CONSTITUTION:A magnetic recording polyester film where the base polyester film is coated on its surface with a continuous thin film (the primer for the magnetic layer) containing fine particles of less than 0.1mum average diameter, thus the surfaces have the fine projections caused by some of the fine particles at a rate of 1 X10<4> to 1X10<8>/mm<2> and the fine projections by only the binder resin at 1X10 to 1X10<4>/mm<2>, the overall surface roughness of 1 to 10nm and the surface roughness in the thin film of only the resin of less than 1.1nm, and the oligomer deposition can be depressed lower than 0.8 %, when the thin film is heated at 160 deg.C for 5 minutes.

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 polyester film useful for producing a magnetic recording medium excellent in running properties, electromagnetic conversion characteristics, storage durability and the like.

[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. There is. For example, a magnetic tape on which Co is vapor-deposited (Japanese Patent Laid-Open No. 54-147010), Co
-Perpendicular magnetic recording medium using Cr alloy (JP-A-52-1
34706) and the like are known. The metal thin film formed by such a thin film forming means as vapor deposition, sputtering or ion plating has a very thin thickness of 1.5 μm or less, and nevertheless the magnetic recording layer has a thickness of 3 μm or more. There is an advantage that performance equal to or higher than that of a magnetic recording medium (a magnetic recording medium obtained by mixing a magnetic substance powder with an organic polymer binder and coating it on a non-magnetic support) can be obtained.

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 the static characteristics of the magnetic recording medium, do not depend so 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. Is caused, and it is a drawback 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 film-film mutual slipperiness is poor, and a blocking phenomenon occurs,
It cannot be a product, which requires that the base 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, 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 running performance at high temperature and high humidity.

In order to improve this drawback, 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
No. 106 and Japanese Patent Application Laid-Open No. 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. 34456/1989 proposes that a discontinuous film of a water-soluble polymer and fine particles forming projections higher than the water-soluble film 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, a 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 are contained in a base film. The temperature rises by receiving radiant energy and the like, and oligomers evaporate and precipitate. 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 silicone resin, which are exemplified in Japanese Patent Publication No. 27733/1990, are difficult to secure the flatness of the coating film, and in particular, the stretching step during 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 wrinkle surface or an earthworm-shaped surface. It becomes a surface having protrusions, and flatness is impaired.

[0009]

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

[0010]

In order to achieve such an object, the present invention has the following constitution.

A continuous thin film is formed on the surface of the polyester film.
The continuous thin film coated with a primer for the magnetic layer
Is made of fine particles with an average particle size of 0.1 μm or less
Fine protrusions (A) used as a mixture and fine protrusions formed only from the resin
(B) is formed, and the height of the fine protrusion (A) is
Is less than 13 nm, 1.0 × 10^Four~ 1.0 x 10 ⁸
Pieces / mm²Exist in the ratio of
1.0 × 10 pieces / mm when the major axis is 0.30 μm or less²that's all
1.0 x 10^FourPieces / mm²Present in a proportion less than the above resin
Fine surface roughness Ra of continuous thin film part^sIs 1.10
nm or less, and the surface roughness Ra of the continuous thin film is
1 to 10 nm, and the continuous thin film is a film
Film surface when heated in air at 160 ° C for 5 minutes
The precipitation rate of the above polyester oligomer microcrystals is 0.8%
Magnetic recording characterized by being able to suppress the following
Polyester film for media.

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 terephthalate is particularly preferable.

Such polyester can be manufactured by a conventionally known method. For example, polyethylene terephthalate can be produced by a method of esterifying terephthalic acid and ethylene glycol or transesterifying dimethyl terephthalate and ethylene glycol, and then polycondensing the reaction product.
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 polycarboxylic 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 becomes 3 to 10 mg atom% with respect to the acid component constituting the polyester.

Further, in the polyester, roughening substances well known in the art, such as calcium carbonate, kaolinite, titanium dioxide, silica, alumina and the like, and other additives are added within a range not impairing the object of the present invention. Agents can be included.

The above polyester is melt-extruded by a conventional method, stretched and oriented biaxially, and heat-set to obtain a film. The biaxial stretching can be performed by a biaxial stretching method such as a sequential biaxial stretching method or a simultaneous biaxial stretching method. This biaxially oriented polyester film usually has a crystal orientation property such that the heat of fusion is 4 cal / g or more as determined by a differential scanning calorimeter in a nitrogen atmosphere at a temperature rising rate of 10 ° C./min. The film thickness after stretch orientation is generally 3 to 100 μm.
m, preferably 4 to 50 μm.

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, especially a ferromagnetic metal thin film layer is formed on this thin film. On the surface of this continuous thin film, there are 1. microprotrusions (A) having fine particles having an average particle diameter 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 , and preferably 1.0 due to only the binder resin. 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 ^s of the continuous thin film portion (background portion) of only the resin of the continuous thin film is 1.10 nm or less, preferably 1.00 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
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 when continuously heated in air at 5 ° C for 5 minutes. It is necessary to apply a continuous thin film.

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, 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, 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-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, 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 their salts (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 with 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, 2,6-
Naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2
Examples thereof include potassium sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic acid anhydride, phthalic acid 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, dimethylolethylsulfonic acid sodium salt, dimethylolpropionic acid Examples thereof include polyvalent hydroxy compounds such as potassium. A polyester resin can be produced 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. Acrylic-polyester resin is used, for example, to add a radical initiator to both ends of the polyester resin to polymerize the acrylic monomer, or to attach a radical initiator 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 is preferably one which does not contain a sulfonyloxy group in its molecule.

As a method for forming fine projections (A) having fine particles as a core 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 in the production process of the polyester film. A method of coating and drying and solidifying on the surface of the film, or a method of coating and drying and solidifying a resin coating solution containing fine particles on a biaxially oriented polyester film can be adopted, but 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 based on the total solid content, and the resin to be a binder is 20 to 20% by weight. 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. On the other hand, 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 resin used as the binder is too small, the adhesion of the coating film to the polyester film is lowered, while when it 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 various methods described above, acrylic resin and polyester resin or acrylic resin is 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.

When a magnetic layer, particularly a metal thin film magnetic layer, is provided on the continuous thin film thus formed, noise is dramatically reduced, the noise level is excellent, and the running property and preservation of the metal thin film surface are improved. Performance with excellent durability can be obtained.

In the present invention, it is preferable to coat a continuous thin film 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 of 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 include polystyrene,
Organic fine particles such as polymethylmethacrylate, methylmethacrylate copolymer, crosslinked methylmethacrylate copolymer, 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 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 in scratch resistance due to 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, etc., 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.

It is preferable that the mixing ratios 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) be 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 component a is too small, the adhesion of the coating film to the polyester film will decrease, while if it is too large, blocking resistance and slipperiness will decrease. If the amount of component b is too small, the creases in the coating film will decrease and the workability will decrease, while if it is too large, the surface will be too rough. If the amount of component c is too small, the slipperiness is reduced, while if it is too large, 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 to form 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 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 stretching orientation in that direction. Biaxially stretched film before re-stretching in the direction to complete the oriented crystallization) and the like.

The film of the present invention is preferably an unstretched film or a film stretched at least uniaxially before the 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 with the coating composition, 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 accelerate the 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 in which the effects of the present invention are not lost.

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 per 1 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 aqueous coating solution is applied to the film immediately after the longitudinal uniaxial stretching, and then the film is introduced into a tenter for lateral stretching and heat setting. At that time, the coating material is expanded in its area with the stretching of the film in the state of an unsolidified coating film and heated to volatilize water, thereby forming 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 stretching and heat treatment are preferably carried out at temperatures of about 80 to about 240 ° C. The heat treatment is usually performed for about 1 to about 20 seconds.

Conditions for oriented crystallization of polyester film,
For example, the conditions such as stretching and heat setting can be performed under the conditions conventionally accumulated in the art.

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 has excellent running properties and storage durability, particularly a metal thin film magnetic layer, which dramatically reduces noise and has a remarkably excellent noise level and magnetic surface. Particularly, it is useful for producing a magnetic recording medium excellent in running property on a metal thin film surface, 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 size It is indicated by the "equivalent spherical diameter" of the particles at the point of 50% by weight of all the particles, which is determined by the light transmission type 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 only 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 a tunnel current. That is, using a sample in which gold having a thickness of 200 angstroms was uniformly vapor-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 microprotrusion is measured by measuring a range of 2 microns × 2 microns in the atmosphere, and the average value of 10 microprotrusions is taken as the height of the microprotrusion.

(5) Fine surface roughness Ra ^{s A} portion without fine protrusions is selected from the range of 2 μm × 2 μm measured with the same sample as described above, and the 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 vertical magnification direction being the Y axis, the value given by the following equation It is expressed in nm.

[0051]

[Equation 1]

In practice, this measurement is for a part without microprotrusions.
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 ^sAnd

(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, a portion of the 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.

[0054]

[Equation 2]

This measurement was carried out for four pieces 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.

The film slippery is judged according to the following criteria.

◯: Good (μs less than 0.6) Δ: Slightly bad (μs 0.6 to 0.8) X: Bad (μs 0.8 or more)

(8) Running Durability FIG. 1 attached is a schematic view of an apparatus for evaluating the film running property. In the drawing, 1 is a feeding reel, 2 is a tension controller, 3, 5, 6, 8, 9, 11 are free rollers, 4 is a tension detector (entrance), 7 is a chrome-plated fixing pin (5 mmφ), and 10 is tension. A detector (outlet), 12 is a guide roller, and 13 is a take-up reel.

As shown in FIG. 1, in a 20 ° C., 60% RH atmosphere, the film is attached to a fixing pin having an outer diameter of 5 mm at an angle θ = (15
2/180) π radians (152 °) are contacted, and they are moved and rubbed at a speed of 3.3 cm / sec. Adjust the tension controller 2 so that the inlet tension (T ₁ ) is 30g, run for 10m, rewind, and repeat running again. This round trip is one time.

1) Scrapability It is evaluated whether or not there is a substance deposited on the fixed pin after repeatedly running 30 times, and evaluated according to the following level.

◯: Almost no deposit was observed Δ: Some evidence of adhesion was found ×: Many

2) Scratch resistance The state of abrasion of the film surface (degree of occurrence of scratches) after repeatedly running 30 times is observed and evaluated according to the following criteria.

◯: Almost no scratches were observed x: Significant occurrence

(9) Electromagnetic conversion characteristics 10 KBPI S / N (dB) ratio during recording and reproduction and 10 K
High-density recording characteristics, particularly the magnitude of noise level, are evaluated by the rate of decrease in output during 50 KBPI recording / reproduction with respect to output during BPI recording / reproduction.

S / N (dB) at 10 KBPI recording / reproduction ◯: 40 dB or more ×: less than 40 dB Output reduction rate A = (output at 10 KBPI recording / reproduction) / (50 KBP
I Output during recording / reproduction) ◯: A is less than 10 x: A is 10 or more.

(10) Tape running property A commercially available 8 mm VT under two conditions of normal temperature and normal humidity and high temperature and high humidity.
Using R, the fluctuation of the screen due to the disturbance of tape running when recording and reproducing were repeated was observed. The evaluation criteria are as follows.

◯: The running evaluation was smooth and there was no fluctuation in the playback evaluation. ×: The running was slow in some places, and the playback screen fluctuated.

(11) Scratch Resistance (Adhesiveness) The scratch resistance was observed by observing scratches on the tape thin film after repeatedly running 100 times under normal temperature and normal humidity and high temperature and high humidity conditions. The evaluation criteria are as follows.

⊚: Almost no scratches were found on the tape thin film surface. ◯: Very weak scratches were found on the tape thin film surface. ×: Tight scratches were found on the tape thin film surface. Occur.

The normal temperature and normal humidity means 25 ° C. and 60% RH.
The high temperature and high humidity are 40 ° C. and 80% RH conditions.

(12) 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 film surface and a micrograph of the surface was taken. To do. The oligomer deposition rate is evaluated by the percentage of the total area occupied by oligomers (imaged in white spots) on this photograph, based on the total area of the photograph.

[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 1 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, manganese acetate / tetrahydrate 0.019
And 0.013 parts of sodium acetate trihydrate were charged to the reactor, and the transesterification reaction was carried out while gradually increasing the internal temperature from 145 ° C. When the transesterification rate reached 95%, 0.044 parts of a glycol solution of a phosphorus compound prepared by previously reacting 25 parts of trimethyl phosphate with 75 parts of ethylene glycol was added as a stabilizer, and ethylene glycol 2 was added as a polymerization catalyst. 0.8 parts trimellitic anhydride and 0.6 parts tetrabutyl titanate in 0.5 parts
Liquid obtained by reacting 5 parts (titanium content is 11% by weight)
0.011 part was added. Next, the reaction product was transferred to a polymerization reactor and subjected to polycondensation reaction under high temperature vacuum (final internal temperature of 290 ° C.) to obtain polyethylene terephthalate having an intrinsic viscosity of 0.60.

This polyethylene terephthalate was melt extruded according to a conventional method and rapidly cooled to prepare an unstretched film having a thickness of 131 μm.
Sequential biaxial stretching was performed at 0 ° C. for 3.6 times and at 105 ° C. for 3.7 times in a transverse direction, and heat setting was further performed at 240 ° C. for 8 seconds to prepare a biaxially oriented film having a thickness of 9.8 μm. ..

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

Composition of coating liquid applied to film surface (A): 1.4 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 83.5
Part, 1.5 parts of 1.4 wt% solution of polymethylmethacrylate fine particles (Nippon Shokubai Kagaku Kogyo Co., Ltd. Eposter MA) (however, the average particle size of these fine particles is 0.03 μm) Polyoxyethylene nonylphenyl 15 parts of 1.4 wt% solution of ether (NS208.5 manufactured by NOF CORPORATION) The coating amount is 2.7 g / m ² by wet.

Composition of coating liquid applied to the film surface (B): 2.1 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 54.7
Part, 2.1 wt% solution of cellulose resin (methyl cellulose SM-15 manufactured by Shin-Etsu Chemical Co., Ltd.) 24.3 parts, 2.1 wt% of polymethyl methacrylate fine particles (Eposter MA manufactured by Nippon Shokubai Chemical Co., Ltd.) Solution 9.0 parts 2.1 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 12.0
The wet coating amount is 4.0 g / m ² .

Using a vacuum vapor deposition device, the polyester film was placed along a cylindrical can having a diameter of 1 m to obtain 5 × 10.
^-5 (Torr) oxygen with a minimum incident angle of 43 degrees Co-N
i (containing 20 wt% of Ni) was obliquely vapor-deposited so as to have a film thickness of about 1500 Å, and then slit into a width of 8 mm to obtain a magnetic tape.

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

[0081]

Example 2 In Example 1, when the internal temperature during the transesterification reaction reached 190 ° C., an ethylene glycol slurry of silicon dioxide having an average particle diameter of 0.09 μm (10 wt% of silicon dioxide / ethylene glycol slurry) was prepared. Three
A polyester film and a magnetic recording medium were obtained in the same manner as in Example 1 except that 0 part was added and the coating liquid applied to the film surface (A) was changed as follows. These characteristics are shown in Table 1.

Composition of coating liquid applied to the film surface (A): 36.0 parts of a 1.5 wt% solution of polyester resin (Plus Coat Z-461 manufactured by Kyosho Chemical Co., Ltd.), acrylic resin (Nippon Pure Chemical 34.0 parts of a 1.5 wt% solution of Julimer AT613) manufactured by K.K. Co., Ltd. 15.0 wt% solution of polymethylmethacrylate microparticles (Eposter MA manufactured by Nippon Shokubai Chemical Co., Ltd.) 15.0 parts
Parts (however, the average particle size of the fine particles is 0.03 μm) 1.5% by weight solution of polyoxyethylene nonylphenyl ether (NS240 manufactured by NOF CORPORATION) 15.0 parts Coating amount is 2.7 g wet / M ² .

[0083]

Example 3 A mixture of 100 parts of bis-β-hydroxyethyl ester of terephthalic acid, 65 parts of terephthalic acid and 29 parts of ethylene glycol was subjected to an esterification reaction at a temperature of 210 to 230 ° C. The reaction is terminated when the amount of water produced by the reaction reaches 13 parts, and the reaction product 1
0.0067 parts of titanium acetate was added per 00 parts. Then, the reaction product is transferred to a polymerization reactor and subjected to polycondensation reaction under high temperature vacuum (final internal temperature 285 ° C.) to obtain an intrinsic viscosity of 0.6.
0 polyethylene terephthalate was obtained.

This polyethylene terephthalate was melt-extruded by a conventional method and rapidly cooled to prepare an unstretched film having a thickness of 131 μm.
Sequential biaxial stretching was performed at a temperature of 3.6 ° C. and a transverse direction of 105 ° C. of 3.7 times, and heat setting was further performed at 238 ° C. for 10 seconds to prepare a biaxially oriented film having a thickness of 9.8 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 (A).
And (B). This surface (A) is the surface on the side where the magnetic layer is formed, and the surface (B) forms a slippery surface.

Composition of coating liquid applied to film surface (A): 1.5 wt of aqueous emulsion prepared by the following method
% Solution 69.9 parts Polymethylmethacrylate fine particles (Nippon Shokubai Kagaku Kogyo Co., Ltd. Eposter MA) 0.1 wt% solution 0.1 parts (however, the average particle diameter of the fine particles is 0.03 μm) Poly 30.0 parts of 1.5 wt% solution of oxyethylene nonyl phenyl ether (NS240 manufactured by NOF CORPORATION) The coating amount was 1.9 g / m ^{2 when} wet.

[Synthesis of Aqueous Emulsion] The acid components are terephthalic acid (50 mol%) and isophthalic acid (50 mol%).
And 100 parts of a polyester in which the glycol component is diethylene glycol (intrinsic viscosity 0.35) was 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, thereby obtaining a 10 wt% polyester aqueous dispersion. The aqueous dispersion was heated to 60 ° C. under normal pressure and 1 part of ammonium persulfate was added. After that, it is heated to 80 ° C. and methyl methacrylate 19 is added.
A mixture of 0 parts, 150 parts of ethyl acrylate, 48 parts of methacrylic acid and 2 parts of t-dodecyl mercaptan was gradually added. Then, 560 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 continued for another 3 hours and then cooled to room temperature.

This reaction product has a solid content of 25 wt.
%, A stable aqueous emulsion with a particle size of 40 nm. This aqueous emulsion is diluted to 1.5 wt%,
It was a 3.0 wt% solution.

Composition of coating liquid applied to film surface (B): 3.0 wt% solution of the above aqueous emulsion 63.
0 parts 3.0 wt% solution of cellulosic resin (methyl cellulose SM-15 manufactured by Shin-Etsu Chemical Co., Ltd.) 18.0 parts 3.0 wt% solution of polymethylmethacrylate fine particles (Eposter MA manufactured by Nippon Shokubai Chemical Co., Ltd.) 9.0 parts (however, the average particle size of the fine particles is 0.035 μm) A 3.0 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF Corporation) 10.0
The wet coating amount is 3.0 g / 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 in the same manner as in Example 1.

[0091]

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 in Example 1 was changed as follows.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating solution applied to the film surface (A): 83.5 parts of 5.0 wt% solution of polyester resin (Polyester WR961 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.),
1.5 parts of 5.0 wt% solution of polymethylmethacrylate fine particles (Eposter MA manufactured by Nippon Shokubai Chemical Co., Ltd.) (However, the average particle diameter of the fine particles is 0.06 μm)
15.0 parts of a 6.0 wt% solution of polyoxyethylene nonyl phenyl ether (NS240 manufactured by NOF CORPORATION) The coating amount was 4.0 g / m ^{2 when} wet.

Composition of coating liquid applied to film surface (B): A coating liquid having the same composition as the coating liquid applied to the film surface (B) in Example 3. 3.0 g wet weight
/ M ² .

[0095]

Comparative Example 1 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) in Example 1 was changed as follows.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating liquid applied to film surface (A): 1.4 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 83.5
Part, 1.4 parts by weight solution of polymethylmethacrylate fine particles (Eposter MA manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) 1.5 parts (however, the average particle diameter of the fine particles is 0.06 μm) Polyoxyethylene nonylphenyl 15.0 parts of 1.4 wt% solution of ether (NS240 manufactured by NOF CORPORATION) The coating amount is 2.7 g / m ² by wet.

[0098]

Comparative Example 2 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) in Example 1 was changed as follows.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating liquid applied to film surface (A): 5.5 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 83.5
Parts, polymethylmethacrylate fine particles (Nippon Shokubai Kagaku Kogyo Co., Ltd. Eposter MA) 5.5 wt% solution 1.5 parts (however, the average particle diameter of the fine particles is 0.03 μm) Polyoxyethylene nonylphenyl 15.0 parts of a 5.5 wt% solution of ether (NS240 manufactured by NOF CORPORATION) The coating amount is 2.7 g / m ^{2 when} wet.

[0101]

[Comparative Example 3] Example 3 except that the heat setting condition after the biaxial stretching was changed to 190 ° C. for 25 seconds and the coating liquid applied to the surface of the film was changed as follows. A polyester film was obtained in exactly the same manner as in 1.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating liquid applied to the film surface (A): Acrylic-polyester resin (Pesresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 1.3 wt% solution 83.0
Part, 2.0 parts of a 1.3 wt% solution of polymethylmethacrylate fine particles (Eposter MA manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd. (however, the average particle size of the fine particles is 0.03 μm)) Polyoxyethylene nonylphenyl 15 parts of 1.3 wt% solution of ether (NS208.5 manufactured by NOF CORPORATION) The coating weight is 2.7 g / m ² .

Composition of coating liquid applied to the film surface (B): 2.1 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 59.0
Part, 2.1 wt% solution of cellulose resin (methyl cellulose SM-15 manufactured by Shin-Etsu Chemical Co., Ltd.) 20.0 parts, 2.1 wt% of polymethyl methacrylate fine particles (Eposter MA manufactured by Nippon Shokubai Chemical Co., Ltd.) Solution 9.0 parts (however, the average particle size of the fine particles is 0.03 μm) 2.1 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF Corporation) 12.0
The wet coating amount is 4.0 g / m ² .

[0105]

Comparative Example 4 A polyester film was obtained in exactly the same manner as in Example 2 except that the coating liquid applied to the film surface (A) in Example 2 was changed as follows.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating liquid applied to film surface (A): 1.6 wt% solution of acrylic resin (Primal AC-604 manufactured by Rohm and Haas Co.) 85.0 parts Polymethylmethacrylate fine particles (Nippon Shokubai Kagaku Kogyo 1.6 parts by weight of 1.6 wt% solution of Eposter MA) manufactured by Co., Ltd. 10.0 parts of 1.6% by weight solution of polyoxyethylene nonyl phenyl ether (NS240 manufactured by NOF CORPORATION) Coating amount is 2.7 g / wet m ² .

[0108]

Comparative Example 5 A polyester film was obtained in exactly the same manner as in Example 2 except that the coating liquid applied to the film surface (A) in Example 2 was changed as follows.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating liquid applied to the film surface (A): 5.0 parts of 0.8 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.),
Acrylic resin (Rohm and Haas Primal AC
-64) 0.8 wt% solution 10.0 parts Polymethyl methyl methacrylate fine particles (Nippon Shokubai Kagaku Kogyo Co., Ltd. Eposter MA) 0.8 wt% solution 70.0
Parts (however, the average particle diameter of the fine particles is 0.03 μm) 0.8 wt% solution of polyoxyethylene nonylphenyl ether (NS208.5 manufactured by NOF CORPORATION) 15.0
The wet coating amount is 2.7 g / m ² .

[0111]

[Comparative Example 6] In Example 2, an average particle size of 0.09 added when the internal temperature during the transesterification reaction reached 190 ° C.
0.30 part of ethylene glycol slurry of silicon dioxide (10 wt% of silicon dioxide / ethylene glycol slurry) having a particle size of 200 μm was used at an internal temperature of 200 during the transesterification reaction.
When the temperature reached ℃, an ethylene glycol slurry of calcium carbonate having an average particle size of 0.75 μm (calcium carbonate
(0 wt% / ethylene glycol slurry) A polyester film was obtained in exactly the same manner as in Example 2, except that the content was changed to 1.3 parts.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

[0113]

Comparative Example 7 A polyester film was obtained in exactly the same manner as in Example 1 except that the film surface (A) in Example 1 was not coated.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

[0115]

Comparative Example 8 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) in Example 1 was changed as follows.

Composition of coating liquid applied on film surface (A): 1.4 wt% solution of acrylic-polyester resin (Pethresin SH551A manufactured by Takamatsu Yushi Co., Ltd.) 85.0
Part, 1.4 wt% solution 1 of polyoxyethylene nonyl phenyl ether (NS208.5 manufactured by NOF CORPORATION)
5.0 copies. The coating amount is 2.7 g / m ^{2 when} wet.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) side of the film in the same manner as in Example 1.

[0118]

Comparative Example 9 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) in Example 1 was changed as follows.

Composition of coating liquid applied to the film surface (A): 0.7 wt% solution of polyester resin (Polyester WR901 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 82.1 parts Polymethylmethacrylate fine particles (Nippon Catalysis Chemical Co., Ltd.) 2.9 parts of 0.7 wt% solution of Eposter MA manufactured by Kogyo Co., Ltd. (however, the average particle size of the fine particles is 0.03 μm) Polyoxyethylene nonyl phenyl ether (NS208.5 manufactured by NOF Corporation) 15 parts of 0.7 wt% solution of). The 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 formed on the surface (A) of the film in the same manner as in Example 1.

[0121]

Comparative Example 10 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) in Example 1 was changed as follows.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating liquid applied to film surface (A): 1.0 wt% solution of acrylic resin (Primal AC-604 manufactured by Rohm and Haas Company) 83.0 parts Polymethylmethacrylate fine particles (Nippon Shokubai Kagaku Kogyo ( 2.0 parts by weight of 1.0 wt% solution of Eposter MA manufactured by Co., Ltd. (however, the average particle size of the fine particles is 0.03 μm) 1. Polyoxyethylene nonylphenyl ether (NS240 manufactured by NOF Corporation) 15.0 parts of 0 wt% solution The coating amount is 2.7 g / m ^{2 when} wet.

[0124]

Comparative Example 11 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) in Example 1 was changed as follows.

Table 1 shows the characteristics of the obtained polyester film and the magnetic recording medium having a magnetic layer formed on the surface (A) of the film in the same manner as in Example 1.

Composition of coating liquid applied to film surface (A): acrylic resin (Jurimer AC1 manufactured by Nippon Pure Chemical Co., Ltd.)
0L) 0.8 wt% solution 65.0 parts Colloidal silica (Catalo manufactured by Catalytic Chemical Industry Co., Ltd.)
id-SI-350) 0.8 wt% solution 5.0 parts Polyoxyethylene nonylphenyl ether (Nippon Yushi Co., Ltd. NS240) 0.8 wt% solution 30.0 parts Coating amount is 2.7 g / wet m ² .

[0127]

[Table 1]

[0128]

INDUSTRIAL APPLICABILITY The polyester film of the present invention can form a magnetic layer which is smooth and has excellent running property, particularly a metal thin film magnetic layer, which dramatically reduces noise and provides a magnetic recording medium having excellent noise levels. It can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for measuring a dynamic friction coefficient for evaluating film running property.

[Explanation of symbols]

 1 Feeding reel 2 Tension controller 3,5,6,8,9,11 Free roller 4 Tension detector (entrance) 7 Fixing pin 10 Tension detector (exit) 12 Guide roller 13 Take-up reel

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[Procedure amendment]

[Submission date] September 11, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0068

[Correction method] Change

[Correction content]

◯: Running screen is smooth and there is no fluctuation in the playback screen . ×: Running is slow in some places, and fluctuations in the playback screen occur.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0093

[Correction method] Change

[Correction content]

Composition of coating solution applied to the film surface (A): 83.5 parts of 5.0 wt% solution of polyester resin (Polyester WR961 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.),
1.5 parts of 5.0 wt% solution of polymethylmethacrylate fine particles (Eposter MA manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd. (however, the average particle diameter of the fine particles is 0.06 μm)) Polyoxyethylene nonylphenyl ether ( 15.0 parts of a 5.0 wt% solution of NS240 manufactured by Nippon Oil & Fats Co., Ltd. The coating amount is 4.0 g / m ^{2 when} wet.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0126

[Correction method] Change

[Correction content]

Composition of coating liquid applied to film surface (A): acrylic resin (Jurimer AC1 manufactured by Nippon Pure Chemical Co., Ltd.)
0L) 0.8 wt% solution 65.0 parts Colloidal silica (Catalyst Kasei Co., Ltd., Catalo
id-SI-350) 0.8 wt% solution 5.0 parts Polyoxyethylene nonylphenyl ether (Nippon Yushi Co., Ltd. NS240) 0.8 wt% solution 30.0 parts Coating amount is 2.7 g / wet m ² .

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masato Sato Inventor, Sagamihara Research Center, Teijin Ltd. 3-37-19 Koyama, Sagamihara-shi, Kanagawa

Claims (5)

[Claims] 1. A polyester film having a surface coated with a primer for a magnetic layer comprising a continuous thin film, wherein the continuous thin film has fine protrusions having a mean particle size of 0.1 μm or less as a core and a resin as a binder. (A) and minute protrusions (B) made of only the resin are formed, and the height of the minute protrusions (A) is 13 nm or less and 1.0 × 10 ^{4 to} 1.0 × 10 ⁸
Present in a proportion of pieces / mm ^2, further microprojection (B) is present in a proportion of less than the maximum major axis of 1.0 × 10 or below 0.30 .mu.m / mm ² or more 1.0 × 10 ⁴ cells / mm ² However, the fine surface roughness Ra ^s of the continuous thin film portion made of only the resin is 1.10.
nm or less, and further, the surface roughness Ra of the continuous thin film is 1 to 10 nm, and the continuous thin film deposits polyester oligomer microcrystals on the surface of the film when the film is heated in air at 160 ° C. for 5 minutes. Rate 0.8%
A polyester film for a magnetic recording medium, which can be suppressed as follows. 2. A continuous thin film for forming an easily sliding surface is coated on the other surface of the polyester film, and the continuous thin film contains a cellulose 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, which has a roughness Ra of 2 to 10 nm. 3. 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. 4. The polyester film for a magnetic recording medium according to claim 1, 2 or 3, wherein the polyester is polyethylene terephthalate. 5. 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.