JP2005302223A - Polyester film for magnetic recording tape, and magnetic recording tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film which can be used to manufacture a magnetic tape with less dropouts through out the whole length even when manufacturing the magnetic tape by vacuum deposition from a roll of a film 25,000 m or longer. <P>SOLUTION: This is the polyester film in which the Ra of its one surface A is 1.5-5 nm and the other surface B is covered with a coating layer mainly made from a cross-linked polymer material. This polyester film for magnetic recording tapes is used by forming a thin ferromagnetic metal layer outside its surface A. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyester film for magnetic recording tape, particularly a polyester film for a ferromagnetic metal thin film magnetic recording tape suitable for digital data recording, such as for a digital video cassette tape, and a magnetic recording tape using the same.

  Digital video tapes for consumer use put into practical use in 1995 are provided with a metallic magnetic thin film of cobalt on a base film by vacuum deposition, a diamond-like carbon film is coated on the surface, and a lubricant layer is further coated thereon. A back coat layer is provided on the opposite side of the base film to ensure the running and durability of the tape in the video tape recorder. Despite the smoothness of the surface properties compared to Hi8 ME (deposition) tape, it has good durability.

As its base film,
(1) A polyester film, a discontinuous film adhered to at least one surface of the film, and a polyester film composed of fine particles present in the film and on the film surface (see, for example, Patent Document 1),
(2) A composite film in which a layer A made of a thermoplastic resin and a layer B made of a thermoplastic resin containing fine particles are laminated (see, for example, Patent Document 2),
(3) A film that is a smooth polyester film and has a nonmagnetic surface side surface formed with a lubricant-based coating layer (see, for example, Patent Document 3, Patent Document 4, Patent Document 5, etc.),
(4) The Ra value of one side surface A of the polyester film is 2 to 4 nm, the Rz value is 10 to 40 nm, the Ra value of the other side surface B is 5 to 15 nm, and the Rz value is 50 to 250 nm. There is no easy-to-slip coating layer formed by coating on the outside of the surface B, and there are 2 to 20/100 cm ² of projections having a height of 540 nm or more, and a ferromagnetic metal on the outside of the surface A. A film characterized by being used with a thin film layer (see, for example, Patent Document 6),
(5) The layer A and the layer B are laminated, the SRa value of the one-side surface A is 2 to 4 nm, the SRz value is 10 to 40 nm, and a surface protrusion is formed on the one-side surface B in the layer B. Fine particles are contained, the average particle size of the fine particles is 50 to 500 nm, the content in the layer B is 0.01 to 1.0% by weight, and formed on the outside of the surface B by coating A film characterized in that it is a polyester film in which an easy-sliding coating layer is provided with a thickness of 1 to 10 nm, and a ferromagnetic metal thin film layer is provided outside the surface A (see, for example, Patent Document 7) ,
In comparison with the Hi8ME tape base, a base film having a smaller roughness on the surface of the metal magnetic film is used.

  However, such an extremely smooth consumer digital video tape has a very large change in electromagnetic conversion characteristics due to variations in the surface properties of its magnetic surface. The tape characteristics obtained vary greatly due to the influence of foreign matter adhering to the cooling can in the vapor deposition process and the effect of heat loss due to insufficient cooling in the cooling can.

That is, when using as a base film for providing a ferromagnetic metal thin film for digital video tape by vacuum deposition,
The film of (1) gives good high-density magnetic recording properties, but has poor handling properties and is unsuitable for mass production.
The tape produced from the film of (2) has a large variation in the surface undulation of the magnetic surface of the tape, and there is a problem that the variation in electromagnetic conversion characteristics is large.
In the film of (3), the coating layer mainly composed of the lubricant on the nonmagnetic surface side surface tends to be scraped or peeled off by a vapor deposition process, particularly by a vacuum evaporation cooling can, thereby increasing the dropout of the magnetic tape produced. There are drawbacks,
The film of (4) is less likely to adhere to the cooling can in the vacuum deposition process, the surface of the magnetic tape obtained by vacuum deposition is small, the magnetic tape can be made with good electromagnetic conversion characteristics, and handling. Provides a polyester film for magnetic recording media that has good properties and is suitable for mass production, but in order to increase the production of digital video tape per day, a larger amount of Co metal thin film is provided on the surface of the base film within a certain period of time. Therefore, when a digital video tape for consumer use is manufactured at a higher deposition rate by using the base film shown in (4) above, the polyester film is formed from the surface B of the film. Of the digital video tape produced by transferring the decomposition product to the deposition surface side. There is a problem that 換特 property becomes poor.

  However, consumer digital video tapes are very popular, and it is desirable to put more tapes on the market, so they can be wound on rolls so that a larger amount of digital video tapes can be produced in a single deposition operation. The length of the base film that has been conventionally 20,000 m or less has been increased to 25,000 m or more, and further to 30,000 m or more.

The base film shown in the above (5) has a problem that it is difficult for the decomposition product of the polyester film to be deposited from the surface B, and the electromagnetic conversion characteristics of the digital video tape produced by transferring the decomposition product to the deposition surface side are poor. Had no problem when the film product winding length was 20,000 m or less. However, in the case of a product obtained by slitting and winding up 25,000 m or more using the base film shown in (5) above, dirt on the surface of the cooling can in the vapor deposition machine from the point where the winding length exceeded 25,000 m. It has become conspicuous, and the problem that the electromagnetic conversion characteristics of a digital video tape produced from a film that exceeds 25,000 m from the surface layer of the product and reaches the core portion becomes poor and the dropout increases has become apparent.
Japanese Examined Patent Publication No. 62-30105 Japanese Patent Publication No. 1-263338 JP 57-195321 A JP-B-1-49116 Japanese Examined Patent Publication No. 4-33273 Japanese Patent Laid-Open No. 10-172127 JP 2002-140812 A

  The object of the present invention is to produce a magnetic tape with good drop-out over the entire length of the polyester film even if the magnetic tape is produced by vacuum deposition from a long polyester film roll product having a length exceeding 25,000 m. It is in providing the polyester film for recording tapes.

That is, the present invention
1. A polyester film for magnetic recording tape, wherein the Ra value of one surface A is 1.5 to 5 nm, and the other surface B is provided with a coating layer containing a crosslinked polymer;
2. The polyester film for magnetic recording tape according to claim 1, wherein the crosslinked polymer is an aromatic sulfonic acid ionomer,
3. The polyester film for magnetic recording tape according to claim 1 or 2, wherein the coating layer has a thickness of 1 to 10 nm.
4). It has a laminated structure including a layer A that forms one surface A and a layer B that forms the other surface B, and particles having an average particle diameter of 0.2 μm or more and less than 1.0 μm are added to the layer B from 0.4 to 0.4 μm. The polyester film for magnetic recording tape according to any one of claims 1 to 3, which is contained by 2.0% by weight,
5). The polyester film for magnetic recording tape according to any one of claims 1 to 4, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate,
6). A magnetic recording tape comprising a ferromagnetic metal thin film layer on one surface A of the polyester film for magnetic recording tape according to claim 1,
7). The magnetic recording tape according to claim 6, wherein the ferromagnetic metal thin film layer has a thickness of 20 to 300 nm.
It is characterized by being.

  According to the present invention, as will be described below, even if the roll product exceeds 25,000 m, the cooling can in the vacuum evaporator does not become dirty even after the length exceeds 25,000 m, and the total length of the long roll product is increased. A magnetic tape with little dropout can be obtained, and is particularly effective for a recording tape for recording digital data such as a digital video tape.

  The polyester for forming the polyester film of the present invention may be any polyester as long as it can be a film having a strength suitable for practical use in magnetic recording tapes due to molecular orientation, among which polyethylene terephthalate, polyethylene-2,6-naphthalate. Is preferred. That is, 80 mol% or more of the constituent components are polyethylene terephthalate or polyethylene naphthalate which is ethylene terephthalate or ethylene naphthalate. Examples of polyester copolymer components 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, and sebacin. Examples thereof include dicarboxylic acid components such as 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.

  In addition, the above polyester may be mixed with a non-reactive sulfonic acid alkali metal salt derivative, a polyalkylene glycol substantially insoluble in the polyester, etc., as long as it does not exceed 5 mol%. Also good.

  Further, the polyester film of the present invention has a polyester layer A constituting one surface A (hereinafter sometimes referred to as layer A) and a polyester layer B constituting the other surface B (hereinafter simply referred to as layer B). A laminated structure including For layer A and layer B, the same polyester may be used, or different ones may be used.

  As for the polyester film of this invention, Ra value of one surface A is 1.5-5 nm, Preferably it is 2-4 nm. If the Ra value is less than 1.5 nm, the metal thin film layer formed by vacuum deposition on the outer surface of the surface A is too smooth, and the video thin film of the video tape is recorded by the video head during recording and reproduction in the digital video tape recorder. Will wear out. On the other hand, if the Ra value exceeds 5 nm, the metal thin film layer is too rough and the output characteristics of the video tape deteriorate, making it unsuitable for a magnetic recording medium.

  The Ra value of the surface A can be adjusted by the particle diameter and the addition amount of the particles in the polyester film layer A forming the surface A and the fine particles of the coating layer on the layer A side described later.

  A coating layer containing a cross-linked polymer is provided on the other surface B side of the polyester film. The cross-linked polymer is preferably a main component in the clothing layer. Without this coating layer, the temperature of the base film rises when the magnetic metal is vacuum-deposited on the polyester film at a high speed, and the decomposition product from the polymer in the film is deposited from the surface B made of polyester. When wound up, the decomposed product is transferred to the vapor deposition surface side, the cooling can is soiled, the dirt adheres to the vacuum-deposited film and is transferred to the vapor deposition surface side, and the electromagnetic conversion characteristics of the video tape The trouble of causing dropout is likely to occur when processing a polyester film having a length exceeding 25,000 m.

  The cross-linked polymer is a polymer material having a cross-linked structure, a polymer in which polyacrylic acid and polyvinyl alcohol are cross-linked by an ester bond, and an aromatic nylon having an epoxy group is cross-linked with an aromatic nylon having an amino group. Polymers and ionomers that are ion-containing polymers, particularly polymers partially or completely neutralized with metal ions, are used. As a result of various investigations, especially when processing a polyester film with a length of more than 25,000 m, the cooling can is soiled, or dirt is attached to the vacuum-deposited film and transferred to the deposition surface side, and the electromagnetic of the video tape. It has been found that ionomers are preferable as the cross-linked polymer in order not to cause troubles such as conversion characteristics and dropout. As an ionomer, a copolymer comprising an ethylene-methacrylic acid copolymer, an ethylene-acrylic acid copolymer, a hydrophobic matrix of a polymer such as ethylene or styrene, and an ion aggregate such as sulfonic acid, carboxylic acid or phosphate. An ionomer having intermolecular bonds between metal molecules such as sodium, zinc, lithium, and potassium ions can be used. However, an aromatic attribute polymer that can be expected to have an affinity for polyester is preferred as the hydrophobic matrix, and particularly an aromatic polymer. Group sulfonic acid ionomers are preferred.

  Aromatic sulfonic acid ionomers include sulfoisophthalic acid metal salt or a mixture of sulfoterephthalic acid metal salt and terephthalic acid (TPA) as the acid component, and a mixture of ethylene glycol (EG) and diethylene glycol (DEG) as the diol component. A copolyester obtained by polymerization using it is preferred. As an acid component, it is a mixture of a metal salt of sulfoisophthalic acid or a metal salt of sulfoterephthalic acid / terephthalic acid (TPA), and the molar ratio is 40-100 / 60-0, more preferably 50-80 / 50-20. The mixture of is preferable. As the diol component, EG / DEG is preferably a mixture having a molar ratio of 95 to 75/5 to 25. As the metal, Na, Li, K and the like are preferable, and Na or Li is particularly preferable. If the mole fraction of the acid component of the metal salt of sulfoisophthalic acid or metal salt of sulfoterephthalic acid is less than 40 mol%, the polyester decomposition product during vapor deposition tends to be deposited on the polyester surface B. The intrinsic viscosity (IV) of the aromatic sulfonic acid ionomer is preferably 0.20 to 0.50, more preferably 0.30 to 0.40. When the IV is less than 0.20, the aromatic sulfonic acid ionomer is easily decomposed during vapor deposition. When the IV exceeds 0.50, the aromatic sulfonic acid ionomer tends to be scraped off by a cooling can during vapor deposition, and the cooling can tends to be soiled.

  The coating layer has a thickness of 1 to 10 nm, more preferably 3 to 8 nm. If the thickness is less than 1 nm, the degradation product of the polyester film is likely to be deposited beyond the coating layer, and if the thickness is more than 10 nm, the coating layer is easily scraped by the cooling can and tends to contaminate the cooling can. However, it is difficult to achieve the object of the present invention.

  The cross-linked polymer content in the coating layer is preferably 40 to 90% by weight, more preferably 50 to 80% by weight. If the cross-linked polymer content is less than 40% by weight, the polyester degradation product during vapor deposition tends to precipitate on the polyester surface B. When the cross-linked polymer content exceeds 90% by weight, the coating layer tends to be fragile and is easily scraped by running with a cooling can during vapor deposition.

  Other compounds contained in the coating layer include a water-soluble polymer and / or a water-dispersible polymer, or a surfactant, or a water-soluble polymer and / or a water-dispersible polymer and a surfactant. Can be used. As the water-soluble polymer, polyvinyl alcohol, tragacanth rubber, gum arabic, casein, cellulose derivatives such as methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyester ether copolymers, water-soluble polyester copolymers, and the like can be used. As the water-dispersible polymer emulsion, polymethyl methacrylate emulsion, polyacrylate emulsion, and the like can be used. As the surfactant, an anion, a cation, or a nonionic surfactant can be used, but a nonionic surfactant is preferable. These are not particularly limited, and various types can be used. In order to improve the handling properties of the polyester film, silicone or a fluorine compound may be added to the coating layer as a lubricant. As the silicone, a polymer in which a large number of organosilicon compounds having a siloxane bond in the molecular skeleton such as polydimethylsiloxane are connected by a covalent bond can be used. As a result, traveling performance with the cooling can and wear resistance are ensured. Moreover, blocking between films when a polyester film is wound is prevented.

  The polyester film may be a polyester film in which a polyester layer A and a layer B are laminated. Particles having an average particle size of 0.2 μm or more and less than 1.0 μm in the layer B (hereinafter, sometimes referred to as inert particles) The content is preferably 0.4 to 2.0% by weight with respect to the layer B. A more preferable range of the content is 0.45 to 0.6% by weight. If the average particle size is less than 0.2 μm and the content is less than 0.4% by weight, it is difficult to wind a long roll product exceeding 25,000 m, and it is difficult to obtain a film product having a good winding shape. When the average particle size is 1.0 μm or more and the content exceeds 2.0% by weight, the roughness of the surface of the layer B is transferred to the surface of the magnetic metal, and the surface waviness of the magnetic metal layer is increased. Electromagnetic conversion characteristics tend to deteriorate and dropout tends to increase.

  The thickness of the layer B is preferably 0.4 μm to 1.0 μm. The thickness of the layer B is less than 0.4 μm. Inactive particles are more easily removed from the layer B. When the thickness of the layer B is 1.0 μm or more, the shape of the inert particles tends to affect the surface of the layer A through the layer A and tends to increase the surface roughness of the layer A, and the electromagnetic conversion characteristics of the magnetic tape are likely to deteriorate. .

  As the inert particles, for example, calcium carbonate, calcium phosphate, silica, alumina, polystyrene, alumina silicate and the like can be used. In addition to the inert particles, a surfactant, an antistatic agent, various ester components and the like may be added.

  Further, another layer may be provided between the layer A and the layer B.

  Moreover, it is also preferable that the polyester film which has said laminated structure provides the coating layer containing a fine particle and an organic compound on the surface of the layer A. FIG. By doing so, running durability with a magnetic head when it is used as a magnetic recording tape can be improved.

  As the fine particles, for example, those coated with an organic polymer using fine particle species as nuclei can be employed. Fine particle types include polyacrylic acid, polystyrene, polyethylene, polyester, polyacrylic acid ester, polymethyl methacrylate, polyepoxy resin, polyvinyl acetate, acrylic-styrene copolymer, acrylic copolymer, and various modified acrylics. Organic compound particles such as a resin, a styrene-butadiene copolymer, various modified styrene-butadiene copolymers, and inorganic particles such as silica, alumina, and calcium carbonate can be employed. Further, as the organic polymer that forms fine particles by coating fine particle seeds, self-crosslinkable ones whose end groups are modified with epoxy, amine, carboxylic acid, hydroxyl group or the like are preferable.

  Organic compounds used for the matrix of the coating layer provided on the surface A include polyvinyl alcohol, tragacanth rubber, casein, gelatin, cellulose derivatives, water-soluble polyester, polyurethane, acrylic resin, acrylic-polyester resin, isophthalic acid ester resin, methacrylic acid Polar polymers such as ester resins or blends thereof can be used.

The particle diameter (average particle diameter) of the fine particles is preferably 5 to 100 nm, more preferably 8 to 60 nm. Fine surface protrusions are formed on the surface of the coating layer by the fine particles, and the particle diameter of the fine surface protrusions is substantially the same as the particle diameter of the fine particles. The number of fine surface protrusions on the surface of the coating layer is preferably 3 million to 90 million pieces / mm ² , more preferably 5 million to 70 million pieces / mm ² . When the particle size is 5 nm or more, or the number of fine surface protrusions is 3 million pieces / mm ² or more, the metal thin film layer in the magnetic recording tape becomes too smooth and the magnetic recording tape runs with the magnetic head. It is possible to prevent the durability from decreasing. On the other hand, when the particle size is 100 nm or less, or the number of fine surface protrusions is 90 million pieces / mm ² or less, the surface of the metal thin film layer when used as a magnetic recording tape is too rough, and the magnetic tape drops. It is possible to prevent the out from increasing.

  As thickness of the polyester film of this invention, 3.0-10.0 micrometers is preferable, More preferably, it is 4.0-9.0 micrometers, More preferably, it is 4.4-8.7 micrometers. By setting the thickness to 3.0 μm or more, the bending rigidity is reduced and the output of the magnetic tape is prevented from being lowered. On the other hand, by setting the thickness to 10.0 μm or less, a thin magnetic recording tape can be obtained. For example, the recording time and storage capacity per cassette can be increased.

  As described above, the polyester film of the present invention can be suitably used as a base film for a magnetic recording tape.

  That is, the magnetic recording tape of the present invention uses the polyester film of the present invention and is provided with a metal thin film layer on the surface A side.

  For example, the metal thin film layer may be provided directly on the surface A or may be provided via the coating layer as described above.

  The metal thin film layer is preferably made of a ferromagnetic material such as iron, cobalt, nickel, or an alloy thereof.

  The thickness of the metal thin film layer is preferably 20 to 300 nm. By setting the thickness to 20 nm or more, it is possible to prevent the reproduction output signal from the magnetic tape from being too weak to read the recorded signal. By setting the thickness to 300 nm or less, it is possible to prevent the reproduction output signal from being too strong and the head reading signal intensity from being saturated and the reading of the recording from becoming impossible.

  Moreover, it is also preferable that a diamond-like carbon film having a thickness of about 10 nm is coated on the metal thin film, and a lubricant is further coated thereon.

  In the magnetic recording tape of the present invention, it is also preferable to provide a backcoat layer on the layer B side of the polyester film. The back coat layer is composed of solid fine particles and a binder, and various additives may be added as necessary, and various types can be used. The back coat layer can be formed by applying a solution of the above material. The thickness of the back coat layer is preferably about 0.3 to 1.5 μm.

  The magnetic recording tape of the present invention is particularly suitable for digital video tape use and data storage tape use.

  Hereinafter, the example of the film of a laminated structure is demonstrated about an example of the manufacturing method of the polyester film and magnetic recording tape of this invention. A film having a single layer structure can be produced according to the method described below.

  The polyester film of the present invention is a normal plastic film manufacturing process consisting of melting, sheet molding, biaxial stretching, and heat setting, a polyester A layer that does not contain fine particles and the like, and the fine particles in the polyester. The contained polyester B layer can be produced by extruding as a sheet on which the A / B layer is laminated by using a coextrusion technique. The extruded sheet was uniaxially stretched in the longitudinal direction or the width direction, and the A / B layer was laminated on one side surface A of the layer A, and on the opposite side surface B of the A layer in the case of a single film layer. In the case of a sheet, the following coating solution is applied to the outside of the B layer and dried, and then stretched and oriented in a direction perpendicular to the previous uniaxial direction to perform heat setting. As a coating solution to be applied, a predetermined amount of fine particles having an average particle diameter of 10 to 30 nm is added to an aqueous solution in which a water-soluble polymer and / or a water-dispersible polymer is dissolved or dispersed on the surface A side. A liquid can be used, and a coating liquid mainly composed of the cross-linked polymer can be used on the surface B side. The production method is not limited to this method.

  Biaxial stretching can be performed, for example, by sequential biaxial stretching or simultaneous biaxial stretching, but if desired, before stretching, it can be stretched again in the longitudinal or transverse direction or longitudinal and transverse directions to increase mechanical strength. It can also be a so-called strengthening type.

In order to form the coating layer on the surface A, as described above, a method of applying a coating solution having a predetermined composition and concentration on the base film after completion of stretching in the uniaxial direction may be employed.
The application method may be any of a doctor blade method, a gravure method, a reverse roll method, and a metering bar method. Ra of the surface A can be adjusted by adjusting fine particles and components of the coating layer. A similar method may be used for forming the coating layer on the layer B, and the coating layer thickness can be adjusted to a desired value by adjusting the solid content concentration of the coating solution and the coating solution thickness.

  The polyester film of the present invention is suitable for use as a base film of a magnetic recording medium, particularly for digital video tape applications, because excellent results can be obtained. In addition, it is preferable because excellent results can be obtained even when used for data storage tape.

  Biaxial stretching may employ a simultaneous biaxial stretching method in addition to the sequential biaxial stretching method as described above. Further, the film may be re-stretched in the longitudinal and / or transverse direction before heat setting, whereby the mechanical strength of the film can be increased.

  As a method for applying the coating liquid, a doctor blade method, a gravure method, a reverse roll method, a metering bar method, or the like can be employed.

  In the magnetic tape of the present invention, a ferromagnetic metal thin film such as Co is formed on the surface A of the polyester base film of the present invention to a film thickness of 100 to 300 nm by vacuum deposition, and diamond-like carbon having a thickness of about 10 nm is formed on the metal thin film. By coating the film and further applying a lubricant to a thickness of about 5 nm, on the other hand, by applying a solution consisting of solid fine particles and a binder with various additives added as necessary on the surface B coating layer It can be manufactured by providing the backcoat layer with a thickness of about 0.3 to 1.5 μm and cutting it to a predetermined width.

[Measuring method]
(1) Intrinsic viscosity of polyester (IV)
Measurement was performed at 25 ° C. using orthochlorophenol as a solvent.

(2) Particle size of inert particles / fine particles The particle powder is dispersed on the test bench of the transmission electron microscope so that the particles do not overlap as much as possible. Observed, the area equivalent circle diameter was determined for at least 100 particles, and the number average value was taken as the particle size (average particle size).

  In addition, when calculating | requiring this particle size from a film, it calculates | requires by the following methods a) and b).

a) Particle size of inert particles in layer B The surface of layer B of the film is subjected to argon ion etching using, for example, an ion coater IB-3 manufactured by Eiko Engineering, and the polyester around the inert particles is ashed. , The inert particles are exposed, and a gold thin film deposition layer is provided on the surface thereof with a gold sputtering device at 20 to 30 nm (χ nm), and observed with a scanning electron microscope at a magnification of about 100,000 times. At least about 100 particles The area circle equivalent diameter is obtained, and the value obtained by subtracting 2χ nm from the number average value is defined as the particle diameter.

b) Particle size of fine particles in the coating layer on the layer A side A gold thin film deposition layer is provided on the surface of the coating layer of the film with a gold sputtering device at 20 to 30 nm (χ nm), and an electron microscope (preferably a scanning electron microscope) ), The area equivalent circle diameter is obtained for at least 100 particles, and the value obtained by subtracting 2χ nm from this number average value is taken as the particle size.

(3) Coating Layer Thickness The coating layer thickness is obtained by multiplying the coating solution thickness at the time of coating the coating solution by the solid content concentration and dividing by the solid content density and the stretch ratio after coating. In addition, when calculating | requiring the thickness of this coating layer from a film, it calculates | requires by the following a) method.

  a) A small piece of film is fixed with a resin, cut parallel to the longitudinal direction of the film to make an ultrathin section of the film cross section, and observed with a transmission electron microscope at a magnification of about 100,000 times or more. The coating layer thickness is determined from the distance between the film and the coating layer / resin interface.

(4) Ra value It measured using the atomic force microscope (scanning probe microscope). Using a desktop small probe microscope (Nanopics 1000) manufactured by Seiko Instruments Inc., the surface of the film is scanned in an atomic force microscope in the range of 5 μm square in the damping mode, and the obtained surface profile curve is JIS B0601 Ra. Ra value was calculated | required from the corresponding arithmetic mean roughness. The magnification in the in-plane direction was 20,000 times, and the magnification in the height direction was about 1 million times. The measurement direction was the film width direction, and the number of measurements was 256. The unit is expressed in nm.

(5) Characteristics of magnetic recording tape Recorded DVC tape using a commercially available camera-integrated digital video tape recorder (Canon FV200), played back for 1 minute, and counted the number of block mosaics displayed on the screen. The dropout (DO) was measured. The DO was examined for initial characteristics after tape production and characteristics after running 100 times for 60 minutes at room temperature and normal humidity (25 ° C., 60% RH). A smaller value of DO is better.

(Example 1)
Polyethylene terephthalate (inherent viscosity 0.66) substantially free of inert particles was prepared as a raw material for the polyester film (raw material A).

  The raw material A was melt-extruded, formed into a sheet, and longitudinally stretched 3.3 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 surface A of the film on one side and the surface B on the opposite side thereof with a coating thickness of 4.0 μm and 3.5 μm.

Polyester surface A:
Methylcellulose 0.12% by weight
(Methoxyl group substitution degree 1.8, weight average molecular weight 18,000)
Water-soluble polyester 0.28% by weight
(1: 1 copolymer of 70 mol% terephthalic acid, 30 mol% 5-sodium sulfoisophthalic acid and ethylene glycol)
Aminoethylsilane coupling agent 0.01% by weight
(3-aminopropyltrimethoxysilane)
Ultrafine silica with an average particle size of 12 nm 0.03% by weight
(Standard deviation 0.3 nm)
Polyester surface B:
Surfactant 0.002% by weight
(Propylene glycol stearate)
Aromatic sulfonic acid ionomer 0.28% by weight
(Copolymer of 5-sodium sulfoisophthalic acid 75 mol% / terephthalic acid 25 mol% acid component and EG 90 mol% / DEG 10 mol% diol component 1: 1)
0.01% by weight of silicone
(Amino-terminated polydimethylsiloxane weight average molecular weight 1,500)
Thereafter, the film was stretched 3.3 times at 98 ° C. in the transverse direction with a stenter, heat-treated at 200 ° C., wound around an intermediate spool, slit into a small width with a slitter, wound into a roll around a cylindrical core, and a thickness of 6. A polyester film in which a 3 μm film was wound in a roll shape with a length of 27,000 m was obtained.

A ferromagnetic metal thin film layer having a thickness of 110 nm was formed on the surface A of this polyester film by vacuum deposition. Next, a diamond-like carbon film having a thickness of 10 nm was formed on the cobalt-oxygen thin film layer by sputtering. Subsequently, on the surface B, carbon black (particle diameter 23 nm, specific surface area 130 m ² / mg), copolymer polyester resin (urethane-modified copolymer polyester, weight average molecular weight 40,000, Tg 80 ° C.), silicone (with a degree of polymerization of 100). A back coat layer made of dimethylpolysiloxane (202 of 202 methyl groups replaced with amino groups) was provided at a thickness of 400 nm, slitted to a width of 6.35 mm by a slitter, and wound on a reel to form a magnetic tape. .

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

(Example 2)
In the production of the base film of Example 1, as raw material B, spherical silica particles having an average particle diameter of 0.3 μm (particles 1, standard deviation 0.01 μm) are 0.50% by weight and average polystyrene particle diameter is 0.8 μm. A polyethylene terephthalate (inherent viscosity 0.66) containing 0.05% by weight of (particle 2, crosslinkable curable polystyrene, standard deviation 0.03 μm) is prepared, and the thickness ratio of raw material A and raw material B is 91: 9. In the same manner as in Example 1, except that the outer surface of the layer made of the raw material A is the polyester surface A, and the outer surface of the layer made of the raw material B is the polyester surface B. A composite polyester film roll in which a 3 μm film was wound up with a length of 30,000 m was obtained. Further, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show properties of the obtained composite polyester film and magnetic tape.

(Example 3)
In the production of the base film of Example 1, the aromatic sulfonic acid ionomer sodium used for the coating solution on the surface B was replaced with lithium, and the rest was the same as in Example 1 except that the film having a thickness of 6.3 μm was long. A polyester film roll wound up at 27,000 m was obtained. Further, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the properties of the obtained polyester film, slit winding shape and magnetic tape.

Example 4
In the production of the base film of Example 1, the coating thickness of the coating solution on the surface B was changed to 1.0 μm, and the rest was the same as in Example 1 except that a 6.3 μm thick film was wound at a length of 27,000 m. A polyester film roll was obtained. Further, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the properties of the obtained polyester film, slit winding shape and magnetic tape.

(Example 5)
In the production of the base film of Example 1, the coating thickness of the coating solution on the surface B was changed to 8.0 μm, and the rest was the same as in Example 1 except that a 6.3 μm thick film was wound at a length of 27,000 m. A polyester film roll was obtained. Further, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the properties of the obtained polyester film, slit winding shape and magnetic tape.

(Example 6)
In the production of the base film of Example 2, the amount of silica added to the raw material B was changed to 0.30% by weight. Others tried to obtain a composite polyester film roll having a thickness of 6.3 μm and a length of 30,000 m in the same manner as in Example 1. However, the film was lost when slitting, and a product having a length of 30,000 m was obtained. It was not possible to collect it, and only a product with a winding length of 27,000 m was obtained. Otherwise, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show properties of the obtained composite polyester film and magnetic tape.

(Example 7)
In the production of the base film of Example 2, the amount of silica added to the raw material B was changed to 2.5% by weight. Other than that, a composite polyester film roll having a thickness of 6.3 μm and a length of 30,000 m was obtained in the same manner as in Example 1. Otherwise, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show properties of the obtained composite polyester film and magnetic tape.

(Example 8)
In the production of the base film of Example 2, the particle diameter of the silica contained in the raw material B was changed to 0.10 μm. Others tried to obtain a composite polyester film roll having a thickness of 6.3 μm and a length of 30,000 m in the same manner as in Example 1. However, the film was lost when slitting, and a product having a length of 30,000 m was obtained. It was not possible to collect it, and only a product with a winding length of 27,000 m was obtained. Otherwise, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show properties of the obtained composite polyester film and magnetic tape.

Example 9
In the production of the base film of Example 2, the particle diameter of the silica contained in the raw material B was changed to 1.2 μm. Other than that, a composite polyester film roll having a thickness of 6.3 μm and a length of 30,000 m was obtained in the same manner as in Example 1. Otherwise, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show properties of the obtained composite polyester film and magnetic tape.

(Example 10)
In the production of the base film of Example 1, the polyester used was changed to polyethylene-2,6-naphthalate (intrinsic viscosity IV 0.70). The coating thickness of the coating solution on the surface A and the surface B is changed to 8.0 μm and 7.0 μm, the longitudinal stretching temperature and magnification are set to 135 ° C. and 5.0 times, and the transverse stretching temperature and magnification are set to 135 ° C., 6 The polyester film roll was obtained in the same manner as in Example 1 except that a 4.2 μm thick film was wound up to a length of 27,000 m. Further, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

(Example 11)
In the production of the base film of Example 1, the concentration of the aromatic sulfonic acid ionomer in the aqueous coating solution on the surface B was 0.12% by weight. Otherwise, a polyester film roll having a length of 27,000 m was obtained in the same manner as in Example 1, and a magnetic tape having a width of 6.35 mm was prepared.

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

(Example 12)
In the production of the base film of Example 1, the concentration of the aromatic sulfonic acid ionomer in the aqueous coating solution on the surface B was 0.62% by weight. Otherwise, a polyester film roll having a length of 27,000 m was obtained in the same manner as in Example 1, and a magnetic tape having a width of 6.35 mm was prepared.

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

(Example 13)
In the production of the base film of Example 1, the molar ratio of 5-sodium sulfoisophthalic acid / terephthalic acid in the acid component of the aromatic sulfonic acid ionomer of the coating aqueous solution on the surface B was changed to 30/70. Otherwise, a polyester film roll having a length of 27,000 m was obtained in the same manner as in Example 1, and a magnetic tape having a width of 6.35 mm was prepared.

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

(Comparative Example 1)
In the production of the base film of Example 1, the coating thickness of the aqueous solution coating on the surface A was changed to 2.0 μm. Otherwise, a polyester film roll having a thickness of 6.3 μm and a length of 27,000 m was obtained in the same manner as in Example 1, and a magnetic tape having a width of 6.35 mm was further produced.

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

(Comparative Example 2)
In the production of the base film of Example 1, the methylcellulose concentration of the aqueous coating solution on the surface A was changed to 0.15% by weight. Other than that, a polyester film roll having a thickness of 6.3 μm and a length of 30,000 m was obtained in the same manner as in Example 1, and a magnetic tape having a width of 6.35 mm was prepared.

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

(Comparative Example 3)
In the production of the base film of Example 1, the sodium ion of the aromatic sulfonic acid ionomer in the aqueous coating solution on the surface B was replaced with a hydrogen ion to make a non-ionomer, and the rest was 27,000 m in the same manner as in Example 1. A polyester film roll was obtained, and a magnetic tape having a width of 6.35 mm was prepared.

  Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

  As is apparent from the tape characteristics shown in Table 2, from the 30,000 m long polyester film product of the present invention, even with a winding length of 27,000 m or more, it has excellent electromagnetic conversion characteristics and durability with little dropout. Could be a digital video tape.

  The present invention creates a durable digital video tape that is excellent in electromagnetic conversion characteristics, low in DO, and durable even when the base film passes 25,000 m or more even if it is longer than 27,000 m. Therefore, although a suitable polyester film for magnetic tape is provided, it can be used not only as a vapor deposition type magnetic tape but also as a polyester film for coating type magnetic tape.

Claims (7)

A polyester film for a magnetic recording tape, wherein the Ra value of one surface A is 1.5 to 5 nm, and the other surface B is provided with a coating layer containing a crosslinked polymer. The polyester film for magnetic recording tape according to claim 1, wherein the crosslinked polymer is an aromatic sulfonic acid ionomer. The polyester film for magnetic recording tapes according to claim 1 or 2, wherein the coating layer has a thickness of 1 to 10 nm. It has a laminated structure including a layer A that forms one surface A and a layer B that forms the other surface B, and particles having an average particle diameter of 0.2 μm or more and less than 1.0 μm are added to the layer B from 0.4 to 0.4 μm. The polyester film for magnetic recording tape according to any one of claims 1 to 3, which is contained in an amount of 2.0% by weight. The polyester film for magnetic recording tape according to any one of claims 1 to 4, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. A magnetic recording tape comprising a ferromagnetic metal thin film layer on one surface A of the polyester film for a magnetic recording tape according to claim 1. The magnetic recording tape according to claim 6, wherein the ferromagnetic metal thin film layer has a thickness of 20 to 300 nm.