JP2002183935A - Method for manufacturing polyester film for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyester film for a magnetic recording medium which is suitable for manufacturing a DVC tape having little DO(drop out) with high productivity even when vapor deposition is carried out with an increased vapor deposition rate. SOLUTION: By the method for manufacturing the polyester film for a magnetic recording medium, after coating liquids to form coating layers on both surfaces (A), (B) of a film stretched in one direction are applied and dried, the film is stretched in the direction perpendicular to the above stretching direction and if necessary further stretched and then heat treated, and a ferromagnetic metal thin film is to be formed in the surface (A) side of the film. A water-based coating liquid containing a water-soluble polymer or water-dispersible polymer and fine particles having 5 to 50 nm average particle size as the main component is applied on the surface (A) by 3 to 100 mg/m2 concentration in terms of the solid content, whereas a water-based coating liquid containing a water-soluble polymer or water-dispersible polymer as the main component is applied on the surface (B) by [0.1×S to 30×S] mg/m2 concentration in terms of the solid content (wherein S is the stretching rate (magnification) after coating).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferromagnetic metal thin-film type magnetic recording medium for recording digital data, such as a digital video cassette tape, with high productivity and high quality. The present invention relates to a method for producing a suitable polyester film for a magnetic recording medium.

[0002]

2. Description of the Related Art Consumer digital video tapes put into practical use in 1995 are provided with a metal magnetic thin film of Co on a base film having a thickness of 6 to 7 .mu.m by vacuum deposition, and the surface thereof is coated with a diamond-like carbon film. Furthermore, a lubricant layer is provided thereon by coating, and on the opposite side of the base film, a back coat layer for securing the running property of the tape in the video tape recorder, durability is provided. In the case of a camera-integrated video using a digital video mini-cassette, the basic specifications (S
D specification) and has a recording time of one hour.

[0003] This digital video cassette (DVC)
Is the world's first digital video cassette tape for home use. A large body of information can be recorded despite its small body. B. Since the signal does not deteriorate, the image quality and sound quality do not deteriorate even after many years, c. Enjoys high image quality and high sound quality because it is not disturbed by noise. D. It has such advantages that the image does not deteriorate even after repeated dubbing, and is highly evaluated in the market.

[0004] As a method of manufacturing the base film,
As shown in Japanese Patent Publication No. 3-80410, a water-soluble polymer and an aqueous solution mainly composed of fine particles having an average particle diameter of 5 nm or more are coated on a surface of a unidirectionally stretched polyester film on which a metal magnetic thin film is formed. 3 to 1000 mg / m ²
After applying and drying, stretching in the direction perpendicular to the stretching direction,
A manufacturing method of performing a heat treatment to form a film is used.

[0005]

However, consumer digital video tapes are very popular, and it is desired to put more tapes on the market, and a larger amount of digital video tapes can be produced by one vapor deposition operation. The length of the base film wound on a roll, which has conventionally been 10,000 m or less, has been increased to 12,000 m or more, and further 15,000 m or more, so that the film can be manufactured.

[0006] In addition, the deposition rate during the production of magnetic tapes has been increased, and the production of digital video tapes per day has been increasing. In order to increase the deposition rate, a larger amount of Co metal thin film must be provided on the base film surface within a certain period of time, and accordingly, the amount of heat escaping from the base film to the cooling can during vacuum deposition must be increased. However, it is difficult in industrial production to sufficiently increase the amount of heat that escapes to the cooling can. Therefore, the temperature of the base film tends to increase as the deposition rate increases.

For this reason, various problems have arisen when a conventional polyester film for a magnetic recording medium according to the production method described in Japanese Patent Publication No. 3-80410 or the like is used as a base film. That is, when a film is formed on the non-magnetic surface side surface of the base film,
There is a problem in that abrasion is caused by the contact running with a cooling can of a vapor deposition process, particularly a vacuum vapor deposition, thereby increasing DO. Also,
If a film is not formed on the non-magnetic surface side of the base film, the non-magnetic surface of the film is used when manufacturing a consumer digital video tape by further increasing the deposition rate using the base film. There is a problem that the decomposition product of the polyester film tends to precipitate from the side surface, the decomposition product is transferred to the vapor deposition surface side, and the manufactured digital video tape has poor electromagnetic conversion characteristics and increases dropout.

In view of the above, the present invention has been made so that the non-magnetic surface side surface of the base film is not shaved by a cooling can in a vacuum evaporator even when a polyester film of a long roll product exceeding 12000 m is evaporated at an increased evaporation speed. Furthermore, even when the heat load applied to the base film is increased, there is no precipitation of polyester decomposition products from the non-magnetic surface side surface, so that the cooling can is not stained, and the produced digital video tape has good electromagnetic conversion characteristics. It is another object of the present invention to provide a method for producing a polyester film for a magnetic recording medium capable of producing a digital video tape with little dropout.

[0009]

In order to achieve the above object, a method for producing a polyester film for a magnetic recording medium according to the present invention comprises: After applying a coating solution for forming a coating layer on both surfaces A and B of the polyester film which has been melt-extruded, cooled and stretched in one direction, and after drying or while drying, a direction perpendicular to the stretching direction. A method for producing a polyester film for a magnetic recording medium in which the surface A side is a ferromagnetic metal thin film forming surface by performing a heat treatment after performing a further stretching in a necessary direction as necessary, On the surface A side, an aqueous coating solution containing a water-soluble polymer or a water-dispersible polymer and fine particles having an average particle size of 5 to 50 nm as main components is applied at a solid content concentration of 3 to 100 mg / m ^2.
On the surface B side, an aqueous coating solution containing a water-soluble polymer or a water-dispersible polymer as a main component is applied at a solid application concentration [0.1 × S to 30 × S] mg / 1. A method for producing a polyester film for a magnetic recording medium to be applied at m ² (S is the stretching ratio (times) after application). 6. The thickness of the polyester film for a magnetic recording medium is 7.
1. The above-mentioned item 1. 2. The method for producing a polyester film for a magnetic recording medium according to the above, The above-mentioned 1., wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. Or 2. 3. The method for producing a polyester film for a magnetic recording medium according to the above, The coating thickness of the coating solution applied to the surface B side is 0.1 to
(1) characterized in that it is 30 μm. ~ 3. 4. The method for producing a polyester film for a magnetic recording medium according to any one of the above, The above-mentioned 1., wherein the magnetic recording medium is a digital recording type magnetic recording tape. ~ 4. 5. The method for producing a polyester film for a magnetic recording medium according to any one of the above, The above-mentioned 1., wherein the magnetic recording medium is a magnetic recording tape having a ferromagnetic metal thin film layer provided on a film surface. ~ 5. The method for producing a polyester film for a magnetic recording medium according to any one of the above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
Any polyester can be used as long as it can form a high-strength film by molecular orientation, and among them, polyethylene terephthalate or polyethylene-2,6-naphthalate is preferable. The term “polyethylene terephthalate” or “polyethylene-2,6-naphthalate” as used herein means that 80% or more of its constituent components are ethylene terephthalate or ethylene naphthalate. Examples of the polyester copolymer component other than ethylene terephthalate and ethylene naphthalate include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, and 1,4-cyclohexanedimethanol, adipic acid, Examples include dicarboxylic acid components such as sebacic acid, phthalic acid, isophthalic acid, and 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid.

Further, the above polyester does not exceed 5% by weight of at least one of an alkali metal salt derivative of sulfonic acid which is not reactive with the polyester and a polyalkylene glycol which is substantially insoluble in the polyester. It may be mixed in the degree.

In the method of the present invention, the coating liquid for forming the coating layer is applied to both surfaces A and B of the polyester film at the stage of being melt-extruded, cooled, and stretched in one direction. This is a film at the time when the polyester is melted, extruded into a sheet or a cylindrical shape, cooled and stretched in one direction, and the stretching direction is usually the longitudinal direction. The stretching temperature is 90 to 130 ° C., and the stretching ratio is preferably 2 times or more, and the upper limit is not particularly limited, but is about 6 times. The polyester film uses a raw material for the layer A forming the surface A side and a raw material for the layer B forming the surface B side and positively containing fine particles,
It is preferred to extrude and obtain an A / B laminated film.

On the surface A side, an aqueous coating solution containing a water-soluble polymer or a water-dispersible polymer and fine particles having an average particle size of 5 to 50 nm as main components is used.
Apply in ² . Here, the aqueous coating liquid is a coating liquid using water as a solvent, that is, an aqueous coating liquid or a water-dispersed liquid coating liquid.

The water-soluble polymer used by being dissolved in the aqueous coating solution is a polar polymer such as polyvinyl alcohol, tragacanth rubber, casein, gelatin, cellulose derivative, water-soluble polyester, polyurethane, and a blend thereof. Can be used, but is not limited to these. Examples of the water-dispersible polymer include polymethyl methacrylate emulsion, polyacrylate emulsion, and the like, but are not limited thereto.

[0015] The fine particles contained in the aqueous coating solution are as follows:
Average particle size is 5 to 50 nm, more preferably 10 to 30 n
m, fine particles of silica, calcium carbonate, inorganic compounds such as alumina, polyacrylic acid spheres, organic compounds such as polystyrene spheres, silica, alumina, inorganic particles such as calcium carbonate as a core, organic Particles coated with a polymer or the like can be used, but are not limited thereto.

If the average particle size of the fine particles is less than 5 nm, the surface of the ferromagnetic metal thin film layer formed by vacuum deposition on the surface A of the polyester film produced by the method of the present invention becomes too smooth, It is not preferable because the ferromagnetic metal thin film layer is worn by the magnetic head during recording and reproduction in the DVC video tape recorder. If the average particle size of the fine particles exceeds 50 nm, the ferromagnetic metal thin film layer formed on the surface A is too rough, and the output characteristics of the magnetic recording tape are undesirably deteriorated.

The amount of the fine particles contained in the aqueous coating solution is preferably 0.5 to 12.0% by weight, more preferably 0.6 to 10.0% by weight, based on the solid content. Solid content concentration of 3 to 100 mg / m ² , more preferably 3 to 6
It is applied in a range of 0 mg / m ² . The application surface is the surface A on the side on which the ferromagnetic metal film is formed.
Is preferably made of polyester from which the polyester film-containing particles have been removed as much as possible.

If the amount of the aqueous coating solution applied to the surface A is less than 3 mg / m ² in terms of the solid content, it is formed by vacuum evaporation on the surface A of the polyester film produced by the method of the present invention. However, such a ferromagnetic metal thin film layer is not suitable because it causes poor durability in repeated recording and reproduction many times in a DVC tape recorder. If the coating amount exceeds 100 mg / m ² in terms of the solid content, the ferromagnetic metal thin film layer formed on the surface A becomes rough and the dropout of the DVC tape increases.

On the surface B side opposite to the surface A, an aqueous coating liquid containing a water-soluble polymer or a water-dispersible polymer as a main component is coated with a solid content concentration of 0.1 × S to 30 × S ] Mg /
m ² , more preferably [0.3 × S to 15 × S] mg /
It applied in m ^2. Here, S is the magnification at which the film is stretched after the application of the coating solution.

The water-based coating liquid applied to the surface B is mainly composed of a water-soluble polymer and / or a water-dispersible polymer. And a silane coupling agent.

It is preferable that fine particles are not substantially present in the coating liquid. Even if the coating solution contains fine particles of about 20% by weight based on the solid content of the coating solution, the problem of abrasion of the film formed on the surface B hardly occurs in the film forming process. The fine particles are substantially present in the coating liquid applied to the front surface B side because it is liable to fall off due to the shaving between various types of transport rolls in the magnetic tape processing step. Preferably not.

Examples of the water-soluble polymer used in the coating solution for the surface B include polyvinyl alcohol, cellulose derivatives such as tragacanth gum, gum arabic, casein, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyester ether copolymers, and water-soluble polymers. A polyester copolymer or the like can be used. In addition, as the water-dispersible polymer, polymethyl methacrylate emulsion, polyacrylate emulsion and the like can be used. Among them, a polymer blend of a cellulose derivative and a water-soluble polyester copolymer is particularly preferred. The water-soluble polyester copolymer is a polyester in which a dicarboxylic acid component and a glycol component are polycondensed,
For example, a functional acid component such as a dicarboxylic acid component having a sulfonic acid group is copolymerized in an amount of 5 mol% or more of all carboxylic acid components, and / or a polyalkylene ether glycol component is used as a glycol component in an amount of 2 to 70% by weight. It is preferable that the polymer is polymerized to have water solubility, but the present invention is not limited thereto.

As the dicarboxylic acid having a sulfonic acid group, preferably, 5-sulfoisophthalic acid, 2-sulfoterephthalic acid and the like, metal salts and phosphonium salts thereof can be used, and 5-sodium sulfoisophthalic acid is particularly preferred. . As the other dicarboxylic acid component when copolymerizing 5-sodium sulfoisophthalic acid, isophthalic acid, terephthalic acid and the like are preferable, and as the glycol component, ethylene glycol and diethylene glycol are preferable. The cellulose derivative contributes to prevent precipitation of the polyester decomposition product, and the water-soluble polyester copolymer contributes to increasing the adhesiveness between the cellulose derivative and the polyester film surface.

As the silicone, a polymer in which a large number of organic silicon compounds having a siloxane bond in the molecular skeleton, such as polydimethylsiloxane, are connected by a covalent bond can be used.
As the silicone, those modified with a functional group such as an epoxy group, an amino group, a methacryl group, or a hydroxyl group on the side chain and at the terminal are more preferable. The smoothness of the coating layer is improved by the silicone, and the running property with the cooling can and the abrasion resistance are secured. In addition, blocking between films when the polyester film is wound is prevented. Note that a fluorine compound may be used as the lubricant.

Examples of the silane coupling agent include organosilicon monomers having two or more different reactive groups in the molecule. One of the reactive groups is a methoxy group, an ethoxy group, a silanol group, or the like. Yes, another reactive group is a vinyl group, an epoxy group, a methacryl group, an amino group, a mercapto group, or the like. As the reactive group, those which bind to the side chain, terminal group and polyester of the water-soluble polymer are selected. As the silane coupling agent, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-
Methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ- Aminopropyltriethoxysilane and the like can be applied. The silane coupling agent contributes to prevent the silicone from being released from the coating layer, and also contributes to improving the adhesion between the coating layer and the polyester.

If the amount of the aqueous coating solution applied to the surface B is less than [0.1 × S] mg / m ^{2 in} terms of the solid content, the thickness of the coating layer on the surface B becomes too thin. When a consumer digital video tape is manufactured by further increasing the deposition rate by using the obtained polyester film as a base film, it becomes difficult to prevent the decomposition product of the polyester film from being precipitated from the surface B. , The decomposition product is surface B
, And the decomposed product is transferred to the vapor deposition surface side, and the electromagnetic conversion characteristics of the manufactured DVC tape are poor and dropout is increased.

When the amount of the aqueous coating liquid applied to the surface B side exceeds [30 × S] mg / m ² in solid content concentration,
The coating layer formed on the surface B is easily removed by the cooling can and is unfavorable because the cooling can tends to be stained.

As described above, the aqueous coating liquid applied to the surface B is preferably an aqueous liquid obtained by adding a silicone and a silane coupling agent to a water-soluble polymer and / or a water-dispersible polymer. As the water-soluble polymer, as described above, a blend of a cellulose derivative and a water-soluble polyester copolymer is particularly desirable. The blend ratio is 100 / [60-250] / [5-2] by weight ratio of cellulose derivative [A] / water-soluble polyester copolymer [B] / silicone / silane coupling agent.
0] / [5 to 40] is preferred.

When the coating liquid is applied to the surface B side, the coating thickness is 0.1 to 30 μm, more preferably 0.5 to 15 μm
It is desirable that If the coating thickness is less than 0.1 μm, coating streaks tend to occur, which is not desirable. If the coating thickness exceeds 30 μm, subsequent drying becomes difficult, which is not desirable.

The coating method is a doctor blade method,
Any of a gravure method, a reverse roll method, a metaling bar method, and an air knife method may be used, but the coating on the surface A side is preferably a metaling bar method in which the applied amount is easily kept constant. The application to the surface B side is preferably an air knife method in which a low concentration coating solution can be easily applied uniformly.

After the application of the water-based coating liquid, the coating liquid is dried. After or during the drying, the coating liquid is stretched in a direction perpendicular to the preceding stretching direction. Thereafter, the film is further stretched if necessary. Stretching in the perpendicular direction is usually performed by stretching in the transverse direction, and is preferably 90 to 145 ° C.
The stretching is performed at 3.0 to 7.0 times (= S ₁ ), and the re-longitudinal stretching, which is performed as necessary, is performed at 100 to 150 ° C. and 1.1 to 1.1 times.
It is preferable to stretch in the longitudinal direction at a magnification of 3.0 times (= S ₂ ). Thereafter, heat treatment is performed at a temperature of 190 to 220C. Next, at a temperature of 130 to 190 ° C, 0.2 to 2.
A relaxation treatment in the transverse direction of about 5% is preferably performed to reduce the heat shrinkage of the film. When it is necessary to further increase the lateral strength, it is preferable to perform stretching (re-lateral stretching) of 1.1 to 2.0 times (= S ₃ ) in the transverse direction simultaneously with heat fixing. In the “stretching ratio after application” in the present invention, S means S ₁ × S ₂ × S ₃ . S ₂ = 1, S ₃ = 1 when re-longitudinal stretching or re-lateral stretching is not performed
Consider It is desirable that the thickness of the coating on the surface B is finally 0.1 to 30 mg / m ² in terms of the solid content concentration.

It is preferable to extrude the A / B laminated film using the raw material for the layer A and the raw material for the layer B containing fine particles positively. In order to further increase the durability of the magnetic recording tape by the magnetic head, the average particle diameter in the polyester film layer A forming the surface A side of the polyester film is 50 to 150 nm, more preferably 55 to 100 nm.
The fine particles of nm may be contained in an amount of 0.01 to 1.0% by weight, more preferably 0.02 to 0.8% by weight. Examples of the fine particles used in the layer B include calcium carbonate, silica, alumina, and polystyrene. The fine particles preferably have an average particle diameter of 100 to 100.
A material having a thickness of 0 nm, more preferably 150 to 900 nm is used, and the amount of addition is preferably 0.05 to 1.0% by weight, more preferably 0.08 to 0.8% by weight.

The Ra value of the surface A of the manufactured polyester film for a magnetic recording medium is determined so as to minimize the abrasion of the ferromagnetic metal thin film layer formed on the surface A by the magnetic head during recording and reproduction. And 2 to 5 nm, more preferably 2 to 4 nm in order to keep the output characteristics of the magnetic tape good. When the Ra value is less than 2 nm,
The surface of the ferromagnetic metal thin film formed by vacuum evaporation on the surface A is too smooth, and the DVC tape is worn by the magnetic head during recording and reproduction in the DVC video tape recorder, which is not preferable. When the Ra value exceeds 5 nm,
Since the ferromagnetic metal thin film layer on the surface A is too rough, the output characteristics of the DVC tape deteriorate, which is not preferable. The Ra value of the surface B is preferably 5 to 30 nm, more preferably 6 to 20 nm. When the Ra value is less than 5 nm, the film is too smooth, and in the production of a polyester film, particularly in the slitting process using a slitter after film formation, the film is slit into a predetermined width and rolled into a roll to produce wrinkles. It is not preferable because it cannot be rolled. When the Ra value exceeds 30 nm, the roughness of the surface B increases and the roughness of the surface B of the polyester film is transferred to the surface A during a period in which the polyester film is manufactured, slit to 10,000 m or more, and left as a product. Then, the surface undulation of the surface A increases, and after the vacuum deposition, the surface undulation of the ferromagnetic metal surface layer increases,
It is not preferable because the electromagnetic conversion characteristics of the DVC tape deteriorate and dropout increases.

The thickness of the polyester film produced by the method of the present invention is preferably 7.0 μm or less, more preferably 3.0 to 6.8 μm. 7.
If it exceeds 0 μm, the DVC tape to be produced becomes too thick and cannot be accommodated in a specified cassette, which is not preferable.

When producing a DVC tape, a ferromagnetic metal thin film layer is provided by vacuum evaporation on the surface A of the polyester film produced by the production method of the present invention. Although it is possible and not particularly limited, a ferromagnetic material of iron, cobalt, nickel, or an alloy thereof is preferable. The thickness of the metal thin film layer is preferably from 100 to 300 nm. 1 on the metal thin film layer
It is preferable that a diamond-like carbon film having a thickness of about 0 nm is coated, and further a lubricant treatment is performed thereon. Further, on the surface B, it is preferable to provide a back coat layer formed by applying a solution composed of solid fine particles and a binder to which various additives are added as necessary. Can be used, and is not particularly limited. The thickness of the back coat layer is about 0.3 to 1.5 μm.

[0036]

EXAMPLE The measuring method used in this example is shown below.

(1) Average Particle Size of Fine Particles (d) Fine particle powders are scattered on an electron microscope (electron microscope) test table so that the particles do not overlap as much as possible. (Microscope) at a magnification of about 1,000,000, the area circle equivalent diameter was obtained for at least 100 particles, and the number average value was used as the particle diameter.

When the particle size is determined from the film, it can be determined by the following method a).

A) A gold thin film deposition layer is provided on the surface of the film A with a thickness of 20 to 30 nm (χ nm) by a gold sputtering apparatus, and observed at an magnification of about 100,000 by an electron microscope (preferably a scanning electron microscope). The area circle equivalent diameter is determined for each particle, and 2χn
The value obtained by subtracting m is used as the particle size.

(2) Concentration of solid content at the time of application of the aqueous coating solution (unit: mg / m ² ) When applying the aqueous coating solution to the surface of the film, the weight of the aqueous coating solution consumed by application within a certain time Ask for. The area where the aqueous coating solution was applied within the fixed time is calculated from the application width, the film speed, and the application time. The amount of the aqueous coating solution at the time of the application is divided by the application area, and the solid content concentration (unit: mg / m ² ) at the time of the application of the aqueous coating solution is calculated from the solid content ratio in the applied aqueous coating solution. . This solid content concentration is a value indicating how many mg of solid content is applied per 1 m ² of the application area.

(3) Coating thickness (unit: μm) at the time of application of the water-based coating liquid The weight of the coating liquid consumed at the time of application obtained in (2) above is divided by the coating area, and the density of the applied water-based coating liquid is obtained. And calculate the coating thickness (μm).

(4) Ra value of surface roughness Ra value of the surface of the film was measured by using an atomic force microscope (scanning probe microscope). Using a scanning probe microscope (SPI3800 series) manufactured by Seiko Instruments Inc., the surface of the film is subjected to an atomic force microscope measurement scan in a dynamic force mode in a range of 30 μm square, and JIS B is obtained from a profile curve of the obtained surface.
It was determined from the arithmetic average roughness corresponding to 0601 Ra. The magnification in the in-plane direction was 10,000 to 50,000 times, and the magnification in the height direction was about 1 million times.

(5) Characteristics of Magnetic Tape Evaluation was made by observing drop-out (DO) using a commercially available digital video tape recorder (DVC) with a built-in camera. Record on the created DVC tape with a commercially available digital video tape recorder with camera,
The DO was measured by counting the number of block-shaped mosaics that appeared on the screen after playing for a minute. DO
Was tested for initial properties after tape production at normal temperature and normal humidity (25 ° C., 60% RH). Further, DO after running 100 times repeatedly was also measured. The smaller the value of DO, the better.

Next, the present invention will be described based on examples.

Example 1 Raw material A containing 0.02% by weight of silica having an average particle diameter of 60 nm in polyethylene terephthalate substantially free of inert particles, and polyethylene terephthalate substantially free of inert particles Aluminum silicate having an average particle size of 190 nm and a particle size of 32
0.36% by weight each with 0 nm polystyrene spheres,
Raw material B containing 0.05% by weight was co-extruded at a thickness ratio of 5: 1 and longitudinally stretched 3.0 times at 110 ° C. by a roll stretching method.

In the step after the longitudinal stretching, an aqueous solution having the following composition and concentration was applied to the outside of the layer A at a coating concentration (solid content concentration) of 30 mg /
It was coated using a metering bar at m ^2. An aqueous solution having the following composition and concentration was applied to the outside of the layer B at an application concentration (solid content concentration) of 9.4 mg / m ² and an application thickness of 3.0 μm by an air knife method. Outside layer A: methyl cellulose 0.10% by weight Water-soluble polyester 0.30% by weight Aminoethylsilane coupling agent 0.01% by weight Ultrafine silica having an average particle diameter of 12 nm 0.03% by weight Layer B outside: methyl cellulose 0.10 % By weight Water-soluble polyester 0.13% by weight Aminoethylsilane coupling agent 0.01% by weight Polydimethylsiloxane (modified at both terminal amino groups) 0.02% by weight The film is stretched 5 times, heat-treated at 210 ° C., wound on an intermediate spool, slit into a small width by a slitter, wound up in a roll on a cylindrical core, and has a thickness of 6.3 μm, a width of 600 mm and a length of 15000.
m of polyester film roll. The Ra value of the surface A / B of the polyester film is 3.0 / 17.0.
nm.

A 110-nm thick ferromagnetic metal thin film layer of a cobalt-oxygen thin film was formed on the surface A of the polyester film by vacuum evaporation. The deposition rate of cobalt was 50% higher than the conventional rate. Next, a diamond-like carbon film having a thickness of 10 nm was formed on the cobalt-oxygen thin film layer by a sputtering method. Then, surface B
A back coat layer made of carbon black, polyurethane, and silicone was provided thereon with a thickness of 400 nm, slit to a width of 6.35 mm with a slitter, and wound on a reel to produce a DVC tape. Table 1 shows the properties of the obtained polyester film and magnetic tape.

Example 2 A 6.3 μm thick film was prepared in the same manner as in Example 1 except that silica having an average particle diameter of 60 nm was removed from the raw material A in the production of the base film of Example 1.
A polyester film roll having a width of 600 mm and a length of 15000 m was manufactured to prepare a DVC tape having a width of 6.35 mm. Table 1 shows the properties of the obtained polyester film and DVC tape. The Ra value of the surface A / B of the polyester film was 3.0 / 17.0 nm.

Example 3 In the production of the base film of Example 2, the polyethylene terephthalate was changed to polyethylene-2,6-naphthalate, the content of aluminum silicate in the raw material B was set to 1.1% by weight, and The stretching temperature and magnification were set to 5.0 times at 135 ° C., the aqueous solution application concentration (solid content concentration) outside the A layer was set to 40 mg / m ^2, and the aqueous solution application concentration (solid content concentration) outside the B layer was 17.5 mg / m ^2. m
^{2. The} coating was applied at a coating thickness of 5.6 μm. The transverse stretching temperature and magnification were 135 ° C and 6.5 times, and the heat treatment was changed at 200 ° C.
m, a polyester film roll having a length of 15000 m was obtained. The Ra value of the surface A / B of the polyester film was 3.2 / 17.9 nm. Otherwise, a DVC tape having a width of 6.35 mm was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained polyester film and DVC tape.

Example 4 In the production of the base film of Example 1, the composition of the aqueous solution outside the layer B was changed as follows, the coating concentration (solid content concentration) was 8.0 mg / m ² , and the coating thickness was 0. 0.08 μm. Outside of layer B: methyl cellulose 3.8% by weight Water-soluble polyester 4.9% by weight Aminoethylsilane coupling agent 0.38% by weight Polydimethylsiloxane 0.76% by weight .3 μm width 6
A polyester film roll having a length of 00 mm and a length of 15000 m was produced. The Ra value of the surface A / B of the polyester film was 3.0 / 17.0 nm. The viscosity of the coating solution outside the layer B was high, the coating thickness was thin, and coating streaks occurred in the longitudinal direction. When the coating streaks occurred on a film roll, wrinkles occurred in the longitudinal direction. Using this film roll, a DVC tape having a width of 6.35 mm was prepared in the same manner as in Example 1. However, a DVC tape could not be prepared from a portion where longitudinal wrinkles occurred, and the yield was about 80%. Met. Table 1 shows the properties of the obtained polyester film and DVC tape.

Example 5 In the production of the base film of Example 1, the composition of the aqueous solution outside the layer B was changed as follows, the coating concentration (solid content concentration) was 9.9 mg / m ² , and the coating thickness was 41 μm. Was applied. Layer B outer side: methylcellulose 0.007% by weight Water-soluble polyester 0.009% by weight Aminoethylsilane coupling agent 0.001% by weight Polydimethylsiloxane 0.002% by weight .3 μm width 6
An attempt was made to produce a polyester film roll having a thickness of 00 mm and a length of 15000 m. However, it was difficult to dry the coating liquid on the outside of the layer B, and the film was liable to be broken when stretched in the transverse direction. Of polyester film roll was obtained. The Ra value of the surface A / B of the polyester film was 3.0 / 17.0 nm. Using this film roll, a DVC tape having a width of 6.35 mm was produced in the same manner as in Example 1. Table 1 shows the properties of the obtained polyester film and DVC tape.

Comparative Example 1 In the production of the base film in Example 1, the average particle diameter of silica in the aqueous solution outside the layer A was 4 n.
m. Otherwise, the thickness is 6.3 μm as in Example 1.
A polyester film roll having a width of 600 mm and a length of 15000 m was manufactured to prepare a DVC tape having a width of 6.35 mm. Obtained polyester film and DVC
Table 1 shows the properties of the tape. The Ra value of the surface A / B of the polyester film was 3.0 / 17.0 nm.

Comparative Example 2 In the production of the base film of Example 1, the average particle diameter of silica in the aqueous solution outside the layer A was 60
nm. Otherwise, the thickness is 6.3 as in Example 1.
A polyester film roll having a width of 600 μm and a length of 15000 m was produced to prepare a DVC tape having a width of 6.35 mm. Obtained polyester film and DV
Table 1 shows the characteristics of the C tape. The Ra value of the surface A / B of the polyester film was 3.0 / 17.0 nm.

[Comparative Example 3] In the production of the base film of Example 1, the coating concentration (solid concentration) of the aqueous solution outside the layer A was 2 mg / m ² . Others are the same as in Example 1 and have a thickness of 6.3 μm and a width of 600 mm and a length of 15000 m
Of polyester film roll of width 6.35m
m DVC tapes were prepared. Table 1 shows the properties of the obtained polyester film and DVC tape. The Ra value of the surface A / B of the polyester film is 3.0 / 17.0.
nm.

[Comparative Example 4] In the production of the base film of Example 1, the solid concentration of the aqueous solution applied outside the layer A was 150.
mg / m ² . Otherwise, a polyester film roll having a thickness of 6.3 μm and a width of 600 mm and a length of 15000 m was manufactured in the same manner as in Example 1, and a DV of 6.35 mm in width was produced.
C tape was made. Table 1 shows the properties of the obtained polyester film and DVC tape. The Ra value of the surface A / B of the polyester film was 3.0 / 17.0 nm.

[Comparative Example 5] In the production of the base film of Example 1, the coating concentration (solid content concentration) of the aqueous solution outside the layer B was set to 0.03 mg / m ² . Others are the same as in Example 1 and have a thickness of 6.3 μm, a width of 600 mm and a length of 150.
5. A polyester film roll having a width of 6 m was manufactured.
A 35 mm DVC tape was made. The cooling can of the deposition process was white and dirty. Table 1 shows the properties of the obtained polyester film and DVC tape. The Ra value of the surface A / B of the polyester film was 3.0 / 17.0 nm.

[Comparative Example 6] In the production of the base film in Example 1, the coating concentration (solid content concentration) of the aqueous solution coating on the outside of the layer B was set to 120 mg / m ² . Others are the same as in Example 1 and have a thickness of 6.3 μm, a width of 600 mm and a length of 1500.
0 m polyester film roll, width 6.3
A 5 mm DVC tape was made. The cooling can of the deposition process was white and dirty. Table 1 shows the properties of the obtained polyester film and DVC tape. The Ra value of the surface A / B of the polyester film was 4.0 / 20.0 nm.

[0058]

[Table 1] As is clear from the characteristics shown in Table 1, D produced by using the polyester film produced by the production method of the present invention.
The VC tape was low in DO and was excellent, and its productivity was also excellent.

[0059]

According to the manufacturing method of the present invention, 12000
Magnetic recording that can produce DVC tape with low DO and good electromagnetic conversion characteristics with high productivity even when the polyester film of a long roll product having a length of more than m is deposited at an increased deposition rate. A polyester film for a medium can be obtained. As described above, the method of the present invention is effective for obtaining a polyester film for a magnetic recording medium for producing a high quality DVC tape with high productivity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 67:00 B29K 67:00 B29L 9:00 B29L 9:00 C08L 67:02 C08L 67: 02F Term (reference) 4D075 BB07Z BB21Z BB92Z CA02 CA09 CA18 CA24 CA48 DA04 DB48 DC28 EA07 EA13 EB19 EB22 EB35 EC02 EC03 EC07 EC24 EC45 EC53 EC54 4F071 AA45 AA46 AF36 AH14 BA01 BB06 BB08 BC01 AD12 A03A03 A03A03 A03A03 QD08 QG01 QG15 QG18 QW05 5D006 CB01 CB05 CB07 CB08

Claims (6)

[Claims] After applying a coating liquid for forming a coating layer on both surfaces A and B of a polyester film which has been melt-extruded, cooled and unidirectionally stretched, the stretched film is dried or dried. The film is stretched in a direction perpendicular to the direction, and if necessary, further stretched in the required direction, and then heat-treated to produce a polyester film for a magnetic recording medium in which the surface A is the surface on which the ferromagnetic metal thin film is formed. In the method, on the surface A side, an aqueous coating liquid containing a water-soluble polymer or a water-dispersible polymer and fine particles having an average particle diameter of 5 to 50 nm as main components has a solid coating concentration of 3 to 10.
Coated at 0 mg / m ^2, and the surface B side, an aqueous coating liquid containing as a main component a water-soluble polymer or water-dispersible polymer, solid coating concentration [0.1 × S~30 × S] mg /
A method for producing a polyester film for a magnetic recording medium, wherein the method is applied at m ² (S is a stretching ratio (times) after application). 2. The method according to claim 1, wherein the thickness of the polyester film for a magnetic recording medium is 7.0 μm or less. 3. The method for producing a polyester film for a magnetic recording medium according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. 4. The coating liquid applied on the surface B has a coating thickness of 0.1 to 30 μm.
3. The method for producing a polyester film for a magnetic recording medium according to any one of 3. 5. The method for producing a polyester film for a magnetic recording medium according to claim 1, wherein the magnetic recording medium is a digital recording type magnetic recording tape. 6. The method for producing a polyester film for a magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic recording tape having a ferromagnetic metal thin film layer provided on a film surface.