JP2004039145A - Polyester film for magnetic recording medium, and magnetic recording tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for a magnetic recording medium which is used for manufacturing a digital video tape having high electromagnetic conversion characteristic and reduced in its dropout, in which a low molecular weight substance or the like is prevented from being deposited on the surface of a base film and a cooling can is made dirty even when evaporation is applied on a long rolled polyester film product whose winding length exceeds 10,000m while increasing the evaporation speed. <P>SOLUTION: The polyester film for the magnetic recording medium is a film consisting of a polyester film with two layers A, B laminated and a coat layer C formed on the outside of the layer B. The Ra value of an outer surface on the layer A side is 1-5nm, the Ra value of the outer surface of the coat layer C is 10-50nm, the coat layer C consists of high molecules whose soluble parameter [δ] is ≤ 10 or ≥ 11 and has 0.2-20 nm thickness, and a ferromagnetic metallic thin film layer is formed on the outside of the outer surface of the layer A side. <P>COPYRIGHT: (C)2004,JPO

Description

【００６０】
表１の結果から明らかなように、フィルム表面Ｂ側に特定の高分子からなる被覆層Ｃを設けた本発明のポリエステルフィルムの場合、フィルム表面Ａに強磁性金属薄膜を設けてＤＶＣテープを製造する際の蒸着工程における冷却キャン汚れがなく、しかも、得られたＤＶＣテープはドロップアウト発生のない優れた特性のものであった。
【００６１】
【発明の効果】
本発明によると、巻き長さが１０，０００ｍを越える長尺ロール製品のポリエステルフィルムを蒸着速度を増して蒸着し、ベースフィルムへかかる熱負荷が増してもベースフィルム表面Ｂからのポリエステル低分子量物や分解物の析出がなく、冷却キャンも汚れず、しかも、電磁変換特性が良好でドロップアウトの少なくエラーレートの低いデジタルビデオテープを製造することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polyester film suitable for a magnetic recording medium, particularly a base film for a ferromagnetic metal thin film type magnetic recording medium such as a digital recording type magnetic recording tape.
[0002]
[Prior art]
The consumer digital video tape put into practical use in 1995 is formed by depositing a metal magnetic thin film of cobalt on a base film by vacuum evaporation and further providing a diamond-like carbon film on the surface thereof. In spite of the smoothness of the surface properties, it has good durability. As the base film, a film having a small surface roughness on which a metal magnetic thin film is formed as described in JP-B-62-30105, JP-B-1-26338, JP-B1-49116, JP-B-4-33273 and the like can be used. It's being used.
[0003]
Digital video tapes for consumer use are very popular because of their features of small size, light weight and high image quality, and it is desired to introduce more tapes to the market at a low cost. In addition, the characteristics have been rapidly expanded to data storage and broadcasting applications, and further improvement in tape characteristics (electromagnetic conversion characteristics, dropout) has been required.
[0004]
In order to achieve this requirement, it is advantageous to be able to produce more digital video tapes in a single vapor deposition operation, so that the winding length of the base film is conventionally less than 10,000 m. Has become longer than 12,000 m and even 30,000 m. Also, the deposition rate has been increased.
[0005]
[Problems to be solved by the invention]
In order to increase the deposition rate, it is necessary to provide more cobalt metal magnetic thin film on the base film surface within a certain period of time, and to increase the amount of heat escaping from the base film to the cooling can during vacuum deposition. Since it is not easy to release a sufficient amount of heat to the cooling can, the temperature of the base film itself tends to rise. As a result, a low molecular weight product or a decomposition product of the polyester film is easily precipitated from the base film surface (surface B) in contact with the cooling can. Further, when the winding of the film becomes longer, more precipitates from the film accumulate on the surface of the cooling can, which leads to a decrease in productivity such as a longer cleaning time. Furthermore, it has become clear that these precipitates are finally transferred to the deposition surface side of the film, and that the digital video tape has more electromagnetic conversion characteristics and poor dropout.
[0006]
Accordingly, the present invention solves the above-mentioned problems of the prior art, and increases the vapor deposition rate of a polyester film of a long roll product having a winding length exceeding 10,000 m, thereby increasing the heat load applied to the base film. Also, it is possible to produce a digital video tape having no low molecular weight or decomposed products of polyester from the base film surface B, no contamination of the cooling can, good electromagnetic conversion characteristics, low dropout and low error rate. An object of the present invention is to provide a polyester film for a magnetic recording medium.
[0007]
[Means for Solving the Problems]
As a result of intensive studies on a polyester film for a magnetic recording medium in order to achieve such an object, the present invention described below has been achieved.
[0008]
That is, the present invention
1. A film comprising a laminated polyester film of a layer A and a layer B and a coating layer C outside the layer B, wherein the Ra value of the outer surface on the layer A side is 1 to 5 nm, and the Ra value of the outer surface of the coating layer C is The coating layer C is a layer having a thickness of 0.2 to 20 nm made of a polymer having a solubility parameter [δ] of 10 or less or 11 or more, and the coating layer C has a thickness of 0.2 to 20 nm. A polyester film for a magnetic recording medium, which is used for a magnetic recording medium used by providing a ferromagnetic metal thin film layer on the outer surface.
[0009]
2. 2. The polyester film for a magnetic recording medium as described in 1 above, wherein the layer B contains 0.05 to 1.0% by weight of wax and / or soap.
3. 3. The polyester film for a magnetic recording medium according to the above or 2, wherein a smooth coating layer containing a water-soluble and / or water-dispersible polymer as a main component is provided outside the layer A.
4. 4. The polyester film for a magnetic recording medium according to any one of the above items 1 to 3, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate.
[0010]
5. The polyester film for a magnetic recording medium according to any one of the above items 1 to 4, which is used for a magnetic recording tape of a digital recording system.
6. After applying the coating liquid for forming the coating layer C on the layer A side of the composite extruded composite film, the polyester film for a magnetic recording medium according to any one of the above 1 to 5 is stretched by a simultaneous biaxial stretching method. A method for producing a polyester film for a magnetic recording medium to be produced.
7. 6. A magnetic recording tape comprising a polyester film according to any one of the above 1 to 5, wherein a ferromagnetic metal thin film layer is provided on the outer surface on the layer A side.
It is assumed that.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
[0012]
The polyester used in the laminated film of the present invention may be a polyester which becomes a high-strength film depending on the molecular orientation, and it is preferable that 80% or more of its constituent components be ethylene terephthalate or ethylene naphthalate, particularly polyethylene terephthalate or polyethylene. -2,6-Naphthalate is more preferred. Further, as a copolymer component, diol components such as diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, 1,4-cyclohexanedimethanol, adipic acid, sebacic acid, Dicarboxylic acid components such as phthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, succinic acid, and oxalic acid, polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid can also be used. Further, at least one kind of alkali metal salt derivative of sulfonic acid which is non-reactive with polyester or substantially insoluble polyalkylene glycol may be mixed and used so as not to exceed 5% by weight. The intrinsic viscosity of such a polyester is preferably from 0.4 to 2.0, more preferably from 0.5 to 1.0, as measured in o-chlorophenol at 25C.
[0013]
In the polyester film of the present invention, the laminated film is a film in which the layer A and the layer B are laminated, and another layer is provided between the layer A and the layer B as long as the object of the present invention is not impaired. The above may be stacked.
[0014]
The total thickness of the film is not particularly limited, but is preferably 3 to 12 μm, and more preferably 4 to 8 μm. The thickness of the layer B is preferably 3 to 30% of the total thickness, more preferably 5 to 15%. When the thickness of the layer B is less than 3% of the total thickness, the fine particles in the layer B easily fall off, which is not preferable. If the thickness of the layer B exceeds 30% of the total thickness, the irregularities due to the fine particles in the layer B are transmitted to the outer surface through the layer A, and it is easy to form a projection-like deformation on the outer surface of the layer A, which is not preferable.
[0015]
In the polyester film of the present invention, the Ra value of the outer surface on the layer A side (hereinafter referred to as surface A) is 1 to 5 nm, preferably 2 to 4 nm, more preferably 2 to 3 nm. When the Ra value is less than 1 nm, it is difficult to make the film into a long roll, and the productivity is reduced. Also, the ferromagnetic metal thin film layer formed on the surface A by vacuum evaporation is too smooth, and the digital video Running property is poor in the tape recorder. If the Ra value exceeds 5 nm, the ferromagnetic metal thin film layer formed on the surface A is too rough, and the electromagnetic conversion characteristics of the video tape deteriorate.
[0016]
The layer A contains 0.01 to 1.0% by weight, preferably 0.03% by weight of fine particles having an average particle diameter of 30 to 150 nm, preferably 40 to 80 nm, in order to improve the durability of the ferromagnetic metal thin film layer. To 0.8% by weight. As the fine particles, conventionally known fine particles can be applied, and examples thereof include silica, alumina, a silica-alumina composite, crosslinked polystyrene particles, polyacryl copolymer particles, and calcium carbonate.
[0017]
Outside the layer A, it is preferable to provide a slippery coating layer to improve the durability of the ferromagnetic metal thin film layer and to cope with long winding of the film roll. The slippery coating layer is a layer containing a water-soluble and / or water-dispersible polymer as a main component. As the polymer that is dissolved or dispersed in water, a conventionally known polymer can be used. Specifically, acrylic resin, polyester resin, urethane resin, vinyl resin, styrene resin, epoxy resin, urea resin, polyamide resin, cellulose resin, olefin resin, fluorine resin, silicon resin Resins, polyvinyl alcohol, casein, gelatin, gum arabic and copolymers and blends thereof. Particularly preferred are acrylic resins, urethane resins, polyester resins, epoxy resins, and cellulose resins. is there. Further, if necessary, various crosslinking agents such as melamine, epoxy, isocyanate, urea and the like and silane coupling agents may be used in combination.
[0018]
In the present invention, the thickness of the slippery coating layer made of a water-soluble and / or water-dispersible polymer is not particularly limited as long as it is within a range that satisfies the Ra value of the surface A. , 0.2 to 100 nm, preferably 0.5 to 50 nm, and more preferably 1 to 25 nm. When the thickness is less than 0.2 nm, the effect of improving slipperiness is reduced, and when the thickness is more than 100 nm, moisture resistance and blocking properties tend to be slightly deteriorated.
[0019]
To the slippery coating layer made of a water-soluble and / or water-dispersible polymer, fine particles having an average particle diameter of 1 to 60 nm, preferably 5 to 40 nm are added for the purpose of further improving slipperiness. Can be. As the fine particles, conventionally known fine particles can be used, for example, colloidal silica, alumina, silica-alumina composite, crosslinked polystyrene particles, polyacryl copolymer particles, crosslinked polystyrene / polyacryl copolymer core / shell particles, and the like. Can be mentioned.
[0020]
In the polyester film of the present invention, the Ra value of the other outer surface, that is, the outer surface of the coating layer C (hereinafter, referred to as surface B) is 10 to 50 nm, preferably 12 to 35 nm, more preferably 15 to 30 nm. is there. When the Ra value is less than 10 nm, it becomes difficult to make the film into a long roll, and wrinkles are apt to be formed in the magnetic recording tape manufacturing process, leading to a decrease in productivity. If the Ra value exceeds 50 nm, the roughness of the surface B is transferred to the surface of the ferromagnetic metal thin film layer when the film is wound in a roll after the ferromagnetic metal thin film layer is provided in a vacuum, causing undulating deformation. This deteriorates the electromagnetic conversion characteristics of the digital video tape.
[0021]
The layer B on the surface B side has an average particle diameter of 50 to 800 nm, preferably 70 to 500 nm, and more in order to achieve the above-mentioned desired Ra value and to improve the handling property in the film and digital video tape production process. Preferably, fine particles of 100 to 300 nm are contained in an amount of 0.01 to 1.5% by weight, preferably 0.03 to 1.0% by weight. Conventionally known fine particles can be used, and examples thereof include silica, alumina, a silica-alumina composite, crosslinked polystyrene particles, polyacryl copolymer particles, and calcium carbonate.
[0022]
Further, in the present invention, in the layer B, for the purpose of preventing the precipitation of low molecular weight polyester from the polyester film due to the residual solvent in the back coat layer of the digital video tape, or to adjust the triboelectric charge of the film. , Wax and / or soap are contained in an amount of 0.05 to 1.0% by weight, preferably 0.1 to 0.7% by weight. If the content is less than 0.05% by weight, the above effect is reduced, and if it exceeds 1.0% by weight, the adhesion between the back coat layer and the film tends to decrease, which is not preferable. Examples of the wax used include, but are not limited to, carnauba wax, whale wax, beeswax, china wax, lanolin and the like. Examples of the soap include metal salts of higher fatty acids and aromatic fatty acids and esters thereof, but are not limited thereto.
[0023]
When a magnetic recording medium is manufactured using a conventional polyester film for a magnetic recording medium, when a ferromagnetic metal is vacuum-deposited at a high speed on the surface A of the polyester film, the temperature of the base film rises and comes into contact with the cooling can. Polyester low molecular weight products and decomposition products precipitate from the film surface B, contaminate the cooling can, and the contaminants further adhere to the vacuum-deposited film surface and are transferred to the vapor-deposited surface, and the electromagnetic conversion characteristics of the digital video tape are transferred. However, in the present invention, in order to prevent such troubles, a polymer having a solubility parameter [δ] formed of a polymer having a solubility parameter [δ] of 10 or less or 11 or more is provided in the present invention. It is necessary that the coated layer C is provided with a thickness of 0.2 to 20 nm, preferably 0.3 to 10 nm. .
[0024]
If the thickness of the coating layer C is less than 0.2 nm, it is difficult to prevent the deposition of low molecular weight polyesters and decomposed products from the film surface B. When the thickness of the coating layer C exceeds 20 nm, the effect of preventing precipitation of low molecular weight polyesters and decomposed products of the polyester is reduced, and the moisture resistance and the blocking property tend to be slightly deteriorated. Therefore, there is a problem that the dropout is increased and the Ra value of the surface B easily exceeds 50 nm.
[0025]
It is necessary that the polymer constituting the coating layer C has a solubility parameter [δ] of 10 or less or 11 or more, that is, out of the range of 10 <[δ] <11. It is preferably at most 9.5 or at least 11.5, more preferably at most 9.0 or at least 12.0. If the solubility parameter [δ] is in the range of 10 <[δ] <11, the effect of preventing precipitation of low molecular weight polyester or decomposed product from the film surface B cannot be obtained. The lower limit and the upper limit of the solubility parameter [δ] are not particularly limited, but from the viewpoint of practically usable polymers, the lower limit of the [δ] is about 8 and the upper limit is about 13.
[0026]
Here, the solubility parameter [δ] is defined as the molar attractive constant (ΔF) of an atomic group in a polymer by the method described in “Adhesion Handbook (3rd Edition), p330 (published by Nikkan Kogyo Shimbun)”. It is a value calculated from the values such as the above, and relates to the solubility, compatibility and adhesiveness of the polymer. As described in the above literature, the solubility parameter [δ] of the polymer is generally calculated from the value of the molar attraction constant (ΔF) and the like by the following equation (A).
[0027]
[Δ] = ΣΔF / V (A)
Here, [δ] = solubility parameter, ΔF = molar attraction constant of atomic group, V = molar volume of polymer (= M / d), M = molecular weight of polymer, d = density (25 ° C).
[0028]
Further, the value of the molar attractive constant (ΔF) of an atomic group in a polymer and the value of its molar volume (Δv) are known as described on page 332 of the above literature, and the solubility parameter [δ ] Can also be obtained from the equation [δ] = ΣΔF / ΣΔv. Therefore, from the atomic groups in the polymer, the solubility parameter [δ] of the polymer may be obtained by calculation using the known values of the molar attractive constant (ΔF) and the molar volume (Δv) for each atomic group. .
[0029]
When two or more polymers are used for the coating layer C, the value (weighted average value) obtained by summing the product of the solubility parameter value of each polymer and its mixing ratio is referred to as the weight of the coating layer. What is necessary is just to let it be the solubility parameter [delta] of the polymer which comprises C. The reason why such a weighted average value can be used as the solubility parameter [δ] in the case of two or more polymers is not clear, but it is common sense to use polymers that form a phase-separated structure. However, it is presumed that the extremely thin film thickness of 20 nm or less is in the homogeneous dispersion phase region.
[0030]
For the polymers used in Examples and Comparative Examples described later, the values of the solubility parameter [δ] were determined by the above calculation method. For example, in the case of the styrene-methyl methacrylate copolymer used in Example 1 described later, the value of the solubility parameter [δ] was calculated as follows.
[0031]
The copolymerization ratio of styrene and methyl methacrylate in the styrene-methyl methacrylate copolymer used in Example 1 was 87% by weight to 13% by weight. The solubility parameter [δ polystyrene] of polystyrene is 9.15 (as described in the aforementioned “Adhesion Handbook (Third Edition)”, page 331), and the solubility parameter [δ polymethyl methacrylate] of polymethyl methacrylate is , 9.53 (according to the description in the aforementioned “Adhesion Handbook (Third Edition)”, page 333). From these values, the solubility parameter [δ] of the copolymer is calculated to be 9.2 by the following equation.
[Δ] = [δ polystyrene] × 0.87 + [δ polymethyl methacrylate] × 0.13 = [9.15] × 0.87 + [9.53] × 0.13 = 9.2
[0032]
Examples of the polymer that can achieve the solubility parameter [δ] range (10 or less or 11 or more) specified in the present invention include acrylic resins, polyester resins, urethane resins, vinyl resins, styrene resins, and epoxy resins. -Based resin, urea-based resin, polyamide-based resin, cellulose-based resin, olefin-based resin, fluorine-based resin, silicon-based resin, polyvinyl alcohol, casein, gelatin, gum arabic, etc., and / or their copolymers and blends Particularly preferred are simple substances and / or blends of acrylic resins, urethane resins, polyester resins, epoxy resins, and cellulose resins. Further, if necessary, various crosslinking agents such as melamine, epoxy, isocyanate, urea and the like and silane coupling agents may be used in combination. In order to stably produce the polyester film of the present invention at low cost, it is preferable that the above polymer is applied to the film surface in a state of being dispersed and / or dissolved in water.
[0033]
Fine particles having an average particle diameter of 1 to 60 nm, preferably 5 to 40 nm can be added to the coating layer C for the purpose of improving the lubricity. As the fine particles, conventionally known fine particles can be applied, for example, colloidal silica, alumina, silica-alumina composite, crosslinked polystyrene particles, polyacryl copolymer particles, crosslinked polystyrene / polyacryl copolymer core / shell particles, and the like. Can be mentioned.
[0034]
Next, an example of a method for producing the polyester film of the present invention will be described, but the present invention is not limited thereto.
[0035]
The polyester film of the present invention is obtained by extruding a resin having an A / B layer laminated thereon into a sheet by using a co-extrusion technique in a usual film melting and film forming process including melting, molding, biaxial stretching and heat setting. It can be manufactured by providing a coating layer C outside the layer B of the sheet by means of coating or the like, forming a film, and winding the film.
[0036]
More specifically, the contained particles are removed as much as possible, or if necessary, fine particles having an average particle diameter of 30 to 150 nm, preferably 40 to 80 nm are contained in an amount of 0.01 to 1.0% by weight, preferably 0.1 to 1.0% by weight. A raw material for layer A containing from 03 to 0.8% by weight, and 0.01 to 1.5% by weight of fine particles having an average particle diameter of 50 to 800 nm, preferably 70 to 500 nm, more preferably 100 to 300 nm; Preferably, a raw material for layer B containing 0.03 to 1.0% by weight is melt-coextruded and cooled and solidified on a casting drum to form an unstretched film sheet. After stretching 5.5 to 5.5 times, an aqueous dispersion and / or aqueous solution of a desired polymer is applied to provide a coating layer C, and dried at 80 to 120 ° C, and then 70 to 1 in the film width direction. The film is stretched 2.5 to 6.0 times at 0 ° C. and relaxed at 170 to 250 ° C. for a predetermined time, if necessary, in the width direction in the range of 0 to 30% and in the longitudinal direction in the range of 0 to 5%. It can be manufactured by heat setting while performing. Further, if necessary, the film may be stretched again in the longitudinal direction and / or the width direction before the heat-setting treatment to obtain a so-called high-strength film. A conventionally known method can be applied to the coating, and specific examples include a gravure coating method, a reverse coating method, a kiss coating method, a die coating method, and a bar coating method. In the present invention, after the stretching in the longitudinal direction, an aqueous dispersion and / or aqueous solution of a desired polymer may be applied to the outside of the layer A of the film sheet to form a slippery coating layer.
[0037]
Biaxial stretching can be performed by a simultaneous biaxial stretching method in addition to the sequential biaxial stretching method described above.
[0038]
In the case of stretching by the simultaneous biaxial stretching method, after melt co-extrusion and cooling and solidifying on a casting drum to form an unstretched film sheet, an aqueous dispersion of a desired polymer is formed in order to provide the coating layer C described above. And / or an aqueous solution is applied and dried at 80 to 110 ° C., and then stretched 2.5 to 6.0 times at 90 to 140 ° C. simultaneously in the longitudinal direction and width direction of the film, respectively, at 170 to 250 ° C. for a predetermined time, If necessary, it can be manufactured by performing a heat-setting treatment while performing a relaxation treatment in the width direction in the range of 0 to 30% and in the longitudinal direction in the range of 0 to 5%. A conventionally known method can be applied to the coating, and specific examples include a gravure coating method, a reverse coating method, a kiss coating method, a die coating method, and a bar coating method. In the case where a slippery coating layer is provided on the outer side of the layer A, after forming the unstretched film sheet, an aqueous dispersion and / or aqueous solution of a desired polymer is also applied on the outer side of the layer A of the film sheet. do it. The simultaneous biaxial stretching method is preferable because there is no contact with various rolls in the longitudinal stretching in the case of the sequential biaxial stretching method, and therefore, minute defects due to roll contact can be prevented. In particular, the present invention is effective for further improving the electromagnetic conversion characteristics of a digital recording type magnetic recording tape provided with a ferromagnetic metal thin film layer and further reducing dropout.
[0039]
The magnetic recording tape of the present invention is obtained by providing a ferromagnetic metal thin film on the surface A (the outer surface on the layer A side) of the polyester base film of the present invention by vacuum evaporation. The ferromagnetic metal thin film is preferably made of a ferromagnetic material of iron, cobalt, nickel or an alloy thereof. The thickness of the ferromagnetic metal thin film is preferably from 100 to 300 nm. On this ferromagnetic metal thin film, a diamond-like carbon (DLC) film is provided as a protective film with a thickness of about 5 to 20 nm for protection, and a fluorine-based lubricant is further provided thereon with a thickness of about 2 to 10 nm for protection. It is preferably formed as Since the ferromagnetic metal thin film, the DLC protective film and the lubricating layer are extremely thin at 107 to 330 nm, the surface of the ferromagnetic metal thin film reflects the unevenness of the base film surface as it is. The magnetic recording tape is made of solid fine particles and a binder on the surface B of the base film in order to secure the running property and durability when the magnetic recording tape comes into contact with various guide pins in the video tape recorder and runs. To form a back coat layer formed by applying a slurry liquid containing various additives. As the solid fine particles, the binder, and the additive, conventionally known ones such as carbon black, polyurethane resin, and silicone can be used, and there is no particular limitation. The thickness of the back coat layer may be about 0.3 to 1.5 μm.
[0040]
[Measurement method]
(1) Surface roughness (Ra) value of the film surface
The surface roughness (Ra) value was measured using an atomic force microscope (scanning probe microscope). That is, using a scanning probe microscope (SPI3800 series) manufactured by Seiko Instruments Inc., the film surface is scanned with an atomic force microscope in a dynamic force mode in a range of 30 μm square, and JIS B0601 is obtained from the profile curve of the obtained surface. From the arithmetic average roughness corresponding to 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.
[0041]
(2) Thickness of coating layer C
It can be determined by multiplying the WET thickness of the coating liquid by the solid concentration of the coating liquid and dividing by the stretching ratio after coating. In the case of Examples and Comparative Examples described later, a small piece of the film was fixed with a resin, and an ultrathin section of the film cross section cut in parallel to the longitudinal direction of the film was prepared. The thickness of the coating layer C was determined by observation.
[0042]
(3) Contamination of cooling can in vapor deposition process
The dirt condition of the cooling can when vacuum-depositing the ferromagnetic metal thin film on the surface of the base film is determined based on the following criteria. From the dirt condition, the amount of low molecular weight polyester or the deposition of decomposition products from the surface B of the base film is determined. It was judged. In the case of ◎ and ○, there is no problem in the process and the tape characteristics.
[0043]
In this vacuum deposition step, the winding length of the base film (the length of the film that passed before the determination of the contamination of the cooling can) was 20,000 m, the film traveling speed was 90 m / min, the temperature of the cooling can was set to minus 25 degrees, and -An oxygen thin film was formed with a thickness of 110 nm.
No dirt ... ◎
The entire surface is uniformly and thinly stained (blue) ・ ・ ・ ○
Dirt uniformly on the entire surface (white) ・ ・ ・ △
Powdery substance adheres to the whole surface or part ・ ・ ・ ×
[0044]
(4) Magnetic tape (DVC tape) characteristics
Recording and playback were performed in a quiet room using the LP mode of a commercially available digital video tape recorder with a built-in camera, and the number of dropouts was determined. The number of dropouts was measured by recording the produced DVC tape with a commercially available digital video tape recorder with a built-in camera, playing it back for one minute, and counting the number of block mosaics that appeared on the screen. The initial characteristics after tape production and the number of dropouts after 100 runs were measured. Good without dropouts.
[0045]
【Example】
Next, the present invention will be described based on examples, but the present invention is not limited to the examples.
[0046]
[Example 1]
A polyethylene terephthalate raw material A containing substantially no inert particles and a polyethylene terephthalate containing substantially no inert particles contained 0.3% by weight of spherical aluminum silicate particles having an average particle diameter of 200 nm and spherical styrene having an average particle diameter of 300 nm. Raw material B containing 0.03% by weight of divinylbenzene copolymer particles was co-extruded at a thickness ratio (A layer: B layer) of 5: 1 and roll-stretched at 112 ° C. in the longitudinal direction at 3.degree. It was stretched by a factor of one.
[0047]
After stretching in the longitudinal direction, a polymer aqueous solution having the following composition and concentration was applied to the outside of the layer A, and a polymer emulsion having the following composition and concentration was applied to the outside of the layer B by bar coating.
(1) Outer layer A
0.10% by weight of water-soluble polyester
0.30% by weight of methylcellulose
Aminoethylsilane coupling agent 0.01% by weight
0.03% by weight of colloidal silica having an average particle diameter of 18 nm
(2) Layer B outside (coating layer C)
Styrene-methyl methacrylate copolymer (copolymerization ratio 87:13) 0.10% by weight
[0048]
Thereafter, the coating solution was dried with a tenter, stretched 4.1 times in the horizontal direction at 105 ° C., then heat-set at 210 ° C., and wound up as a film intermediate product having a thickness of 6.3 μm. Further, the film was slit to a width of 620 mm with a slitter to obtain a film roll having a length of 20,000 m.
[0049]
Cobalt was deposited on the surface A side of the polyester film by a vacuum deposition method to form a ferromagnetic metal thin film layer having a thickness of 110 nm. Next, a diamond-like carbon film was formed with a thickness of 10 nm by a sputtering method, and a fluorine-based lubricant layer was further provided with a thickness of 6 nm. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone was provided on the surface B with a thickness of 400 nm, and slit to 6.35 mm using a slitter to produce a DVC tape.
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0050]
[Example 2]
In the production of the film of Example 1, a polyester film and a DVC tape were produced in the same manner as in Example 1 except that the coating composition applied to the outside of the layer B was changed to the following composition and concentration.
(1) Layer B outside (coating layer C)
Hydroxypropyl-methylcellulose 0.09% by weight
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0051]
[Example 3]
In the production of the film of Example 1, a polyester film and a DVC tape were produced in the same manner as in Example 1 except that the coating composition applied to the outside of the layer B was changed to the following composition and concentration.
(1) Layer B outside (coating layer C)
Hydroxypropyl-methylcellulose 0.07% by weight
0.03% by weight of copolyester (*)
*: Monomer composition is terephthalic acid, sulfoisophthalic acid, ethylene glycol, diethylene glycol (molar ratio 70: 30: 55: 45)
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0052]
[Comparative Example 1]
In the production of the film of Example 1, a polyester film and a DVC tape were produced in the same manner as in Example 1 except that the colloidal silica in the aqueous polymer solution applied to the outside of the layer A was changed to one having an average particle diameter of 4 nm. .
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0053]
[Comparative Example 2]
In the production of the film of Example 1, a polyester film and a DVC tape were produced in the same manner as in Example 1 except that the colloidal silica in the aqueous polymer solution applied to the outside of the layer A was changed to one having an average particle diameter of 60 nm.
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0054]
[Comparative Example 3]
In the production of the film of Example 2, a polyester film and a DVC tape were produced in the same manner as in Example 2, except that the coating composition applied to the outside of the layer B was changed to the following composition and concentration.
(1) Layer B outside (coating layer C)
Hydroxypropyl-methylcellulose 0.25% by weight
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0055]
[Comparative Example 4]
In the production of the film of Example 1, a polyester film and a DVC tape were produced in the same manner as in Example 1 except that the coating composition applied to the outside of the layer B was changed to the following composition and concentration.
[0056]
(1) Layer B outside (coating layer C)
0.10% by weight of copolymerized polyester (*)
*: Monomer composition is terephthalic acid, sulfoisophthalic acid, ethylene glycol, diethylene glycol (molar ratio 70: 30: 55: 45)
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0057]
[Comparative Example 5]
In the production of the film of Example 1, a polyester film and a DVC tape were produced in the same manner as in Example 1 except that the coating composition applied to the outside of the layer B was changed to the following composition and concentration.
(1) Layer B outside (coating layer C)
Styrene-methyl methacrylate copolymer (copolymerization ratio 87:13) 0.01% by weight
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0058]
[Comparative Example 6]
In the production of the film of Example 2, instead of allowing the raw material B to contain 0.03% by weight of spherical styrene-divinylbenzene copolymer particles having an average particle diameter of 300 nm, spherical styrene-divinylbenzene copolymer particles having an average particle diameter of 450 nm A polyester film and a DVC tape were produced in the same manner as in Example 2 except that 0.3% by weight was contained.
Table 1 shows the properties of the obtained polyester film and DVC tape.
[0059]
[Table 1]

[0060]
As is clear from the results in Table 1, in the case of the polyester film of the present invention in which the coating layer C made of a specific polymer is provided on the film surface B side, a DVC tape is manufactured by providing a ferromagnetic metal thin film on the film surface A. There was no cooling can contamination in the vapor deposition step, and the obtained DVC tape had excellent characteristics without dropout.
[0061]
【The invention's effect】
According to the present invention, a polyester film of a long roll product having a winding length of more than 10,000 m is vapor-deposited at an increased vapor deposition rate, and the polyester low molecular weight product from the base film surface B even when the heat load on the base film increases. It is possible to produce a digital video tape having no electromagnetic waves and no decomposition products, no contamination of the cooling can, good electromagnetic conversion characteristics, low dropout and a low error rate.

Claims (7)

A film comprising a laminated polyester film of layer A and layer B and a coating layer C outside layer B, wherein the Ra value of the outer surface on the layer A side is 1 to 5 nm, and the Ra value of the outer surface of coating layer C is The coating layer C is a layer having a thickness of 0.2 to 20 nm made of a polymer having a solubility parameter [δ] of 10 or less or 11 or more, and has a thickness of 0.2 to 20 nm. A polyester film for a magnetic recording medium, wherein the polyester film is for a magnetic recording medium used by providing a ferromagnetic metal thin film layer outside the surface. The polyester film for a magnetic recording medium according to claim 1, wherein the layer B contains 0.05 to 1.0% by weight of wax and / or soap. The polyester film for a magnetic recording medium according to claim 1 or 2, wherein a slippery coating layer containing a water-soluble and / or water-dispersible polymer as a main component is provided outside the layer A. . The polyester film for a magnetic recording medium according to any one of claims 1 to 3, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. The polyester film for a magnetic recording medium according to any one of claims 1 to 4, which is used for a magnetic recording tape of a digital recording system. The polyester film for a magnetic recording medium according to any one of claims 1 to 5, wherein a coating liquid for forming the coating layer C is applied to the layer A side of the composite extruded composite film and then stretched by a simultaneous biaxial stretching method. And a method for producing a polyester film for a magnetic recording medium. A magnetic recording tape comprising a ferromagnetic metal thin film layer provided on the outer surface of the polyester film according to claim 1 on the layer A side.