JP2005271246A - Laminated polyester film and magnetic recording tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for a digital video tape in which the occurrence of longitudinal wrinkles with the passage of time after slit winding is prevented even when its length exceeds 20,000 m, to which high speed vacuum vapor deposition can be applied, and which is excellent in electromagnetic conversion characteristics, reduced in DO (drop out), and good in durability. <P>SOLUTION: The polyester film includes a layer A and a layer B. The layer B contains inert particles β, α2, and α1 per 100 wt.% of the polyester. In the particles β, the content of particles at least 0.1 μm and below 0.22 μm in particles size is 0.2-1.6 wt.%. In the particles α2, the content of particles at least 0.22 μm and below 0.4 μm in particle size is 0.01-0.7 wt.%. In the particles α1, the content of particles at least 0.4 μm and below 1.0 μm in particle size is 0.0005-0.01 wt.%. The content of particles β, α2, and α1 in total is 0.4-2.0 wt.%. A covering layer 1.5-5 nm in arithmetic average roughness Ra and 10-60 nm in ten-point average roughness is provided on the side of the layer A. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laminated polyester film, particularly a laminated polyester film suitable for magnetic recording tape applications. The present invention also relates to a ferromagnetic metal thin film type magnetic recording tape suitable for recording digital data, such as a magnetic recording tape, particularly for a digital video cassette tape.

  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 comprising 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 smooth polyester film with a non-magnetic surface-side surface formed with a lubricant-based coating layer (for example, Patent Document 3, Patent Document 4, Patent Document 5, etc.) is used, compared to a base for Hi8ME tape. Furthermore, a base film having a small 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 made 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 lubricant-based coating layer on the non-magnetic surface side tends to be scraped or peeled off by a vapor deposition process, particularly by a vacuum evaporation cooling can. There is a disadvantage that increases.

There is little dirt adhering to the cooling can in the vacuum deposition process, the surface waviness of the magnetic tape obtained by vacuum deposition is small, it can be made a magnetic tape with good electromagnetic conversion characteristics, and the handling property is good, mass production For the purpose of providing a polyester film for magnetic recording media suitable for
(4) Ra value of one side surface A of the polyester film is 2-4 nm, Rz value is 10-40 nm, Ra value of the other side surface B is 5-15 nm, Rz value is 50-250 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 polyester film for magnetic recording media (see Patent Document 6), which is characterized by being used with a thin film layer, has been proposed.

However, consumer digital video tapes have been well received, and it is desirable to introduce more tapes into the market, so that a larger amount of digital video tapes can be produced in a single vapor deposition operation. It has been practiced to increase the length from what was conventionally 10,000 m or less to 20000 m or more, and further to 30000 m or more. When the base film shown in (4) is used for slitting and winding up 20000m or more along with the lengthening of such a base film, the roll entrainment air is removed over time (about 24 hours) and the product It has been found that vertical wrinkles occur. When the product in which the vertical wrinkles are generated is vacuum-deposited, the adhesiveness with the cooling can is lowered, the cooling efficiency is lowered, the polyester degradation product is deposited from the surface B of the film, and the degradation product is transferred to the deposition surface. It has become apparent that the digital video tape produced has poor electromagnetic conversion characteristics and a large dropout. Also, when putting such a long product into a vacuum evaporator and evacuating the air to make a vacuum, the amount of air present between the film and the film layer is large, so the evacuation time becomes long and sufficient time It has been found that there is a large amount of residual air in the vacuum vapor deposition device unless it is taken.
Japanese Examined Patent Publication No. 62-30105 Japanese Patent Publication No. 1-263338 JP-A-57-195321 JP-B-1-49116 Japanese Examined Patent Publication No. 4-33273 Japanese Patent Laid-Open No. 10-172127

  The object of the present invention is that even if a polyester film of a long roll product exceeding 20000 m is slit and wound, no wrinkle is generated over time (about 24 hours), the evacuation time is not prolonged, and the handling property is good. Another object of the present invention is to provide a polyester film for a magnetic recording medium capable of producing a digital video tape with high productivity.

That is, the present invention is a laminated polyester film comprising layer A and layer B which are two polyester layers,
In layer B,
The content of the inert particles β having a particle size of 0.1 μm or more and less than 0.22 μm is 0.2 to 1.6% by weight with respect to the layer B,
The content of the inert particles α2 having a particle size of 0.22 μm or more and less than 0.4 μm is 0.01 to 0.7% by weight with respect to the layer B,
The content of the inert particles α1 having a particle size of 0.4 μm or more and less than 1.0 μm is 0.0005 to 0.01% by weight with respect to the layer B,
The total content of the inert particles α1, α2 and β is 0.4 to 2.0% by weight based on the layer B;
A coating layer is provided on the layer A side,
And the arithmetic mean roughness Ra value of the surface of the said coating layer is 1.5-5 nm, and 10 points | pieces average roughness Rz value is 10-60 nm, It is a laminated polyester film characterized by the above-mentioned.

  The present invention also provides a magnetic recording tape comprising the laminated polyester film of the present invention and a metal thin film layer provided on the layer A side.

  The laminated polyester film of the present invention is a long roll product exceeding 20000 m, and does not generate aging wrinkles over 24 hours after the slit winding process, and the air escape rate in the vapor deposition device is high, and the magnetic tape Can produce a magnetic tape with good cooling performance, good electromagnetic conversion characteristics and low dropout, especially for recording tapes that record digital data such as digital video tapes. .

  The laminated polyester film of the present invention comprises layer A and layer B, which are two polyester layers.

  The polyester for forming the layer A and the layer B may be any polyester that can be used as a film having a strength suitable for practical use in magnetic recording tape by molecular orientation. Among them, polyethylene terephthalate, polyethylene-2,6-naphthalate Is preferred. It is also preferred that 80% or more of the constituent components are ethylene terephthalate or ethylene naphthalate.

  Further, polyethylene terephthalate or polyethylene-2,6-naphthalate may be copolymerized with each other, or may be copolymerized with other copolymer components. Examples of other copolymer components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, and 1,4-cyclohexanedimethanol, adipic acid, sebacic acid, phthalic acid, and isophthalic acid. And dicarboxylic acid components such as 5-sodiumsulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid.

  In addition, the above-mentioned polyester is 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% by weight. Also good.

  The layers A and B may be made of the same polyester or different ones.

  In the laminated polyester film of the present invention, the content of the inert particles β having a particle size of 0.1 μm or more and less than 0.22 μm in the layer B is 0.2 to 1.6% by weight with respect to the layer B. It is important that it is 0.2 to 1.0% by weight, more preferably 0.3 to 0.8% by weight. If it is less than 0.2% by weight, the air existing between the polyester films wound when vacuum-deposited on the laminated polyester film becomes difficult to move, the evacuation time becomes longer, and the speed to reach the vacuum state The residual air tends to remain in the vacuum vapor deposition device. On the other hand, when the content exceeds 1.6% by weight, the roughness of the surface of the layer B is transferred to the surface of the magnetic metal, the surface waviness of the magnetic metal layer increases, the electromagnetic conversion characteristics of the magnetic recording tape deteriorate, and the dropout Tend to increase.

  In the laminated polyester film of the present invention, the content of the inert particles α2 having a particle diameter of 0.22 μm or more and less than 0.4 μm in the layer B is 0.01 to 0.7% by weight with respect to the layer B. It is important that it is 0.02 to 0.4% by weight, more preferably 0.03 to 0.2% by weight. When it is less than 0.01% by weight, when slitting and winding a long roll product exceeding 20000 m, the film is lost, the end face of the roll product is likely to be disturbed, and a product with a good winding shape is hardly collected. On the other hand, if it exceeds 0.7% by weight, the roughness of the surface of the layer B is transferred to the surface of the magnetic metal, the surface waviness of the magnetic metal layer increases, the electromagnetic conversion characteristics of the magnetic recording tape deteriorate, and dropout Tend to increase.

  In the laminated polyester film of the present invention, the content of the inert particles α1 having a particle size of 0.4 μm or more and less than 1.0 μm in the layer B is 0.0005 to 0.01% by weight with respect to the layer B. It is important that it is 0.0007 to 0.007% by weight, more preferably 0.0007 to 0.005% by weight. In the case of less than 0.0005% by weight, in a long roll product exceeding 20000m that has been slit and wound, the air existing in the film layer escapes unevenly over a period of about 24 hours or more, and a vertical wrinkle defect occurs. Tend to. When the content exceeds 0.01% by weight, the roughness of the surface of layer B is transferred to the surface of the magnetic metal, the surface undulation of the magnetic metal layer increases, the electromagnetic conversion characteristics of the magnetic recording tape deteriorate, and the dropout increases. Tend to.

  In the laminated polyester film of the present invention, it is important that the total content of the inert particles α1, α2, and β in the layer B is 0.4 to 2.0% by weight with respect to the layer B. Is 0.4 to 1.3% by weight, more preferably 0.4 to 1.0% by weight. When the content is less than 0.4% by weight, the film is too smooth, and when the polyester film is produced, particularly when the film is slit into a predetermined width in a slitting process using a slitter, the film is rolled into a roll. It gets lost in the horizontal direction and cannot be rolled up. On the other hand, when the content exceeds 2.0% by weight, the surface of the layer B has a roughness of the surface of the magnetic metal when the magnetic metal is vacuum-deposited on the polyester film and then the film having the magnetic metal thin film layer in a roll shape is left unrolled. The surface undulation of the magnetic metal thin film layer increases, the electromagnetic conversion characteristics of the magnetic recording tape deteriorate, and the dropout increases.

  As the particle size distribution of the inert particles α1, α2, and β, for example, one gentle peak is 0.1 μm or more and less than 1.0 μm even if the particle size range does not have a sharp distribution peak. Even if it exists in the range of (alpha), as long as (alpha) 1, (alpha) 2, and (beta) defined by each particle size range satisfy | fill the above-mentioned prescription | regulation.

  On the other hand, it is also preferable that the inert particle α1 has a sharp particle size distribution, so that air escape over time is uniform, and the particle size is abscissa and the number of particles is ordinate (particle size resolution is 0.005 μm). The half value width is preferably 0.2 μm or less, more preferably 0.16 μm or less. More preferably, it is 0.14 μm or less.

  In addition, it is preferable that the particle size distribution of the inert particles α2 is sharp so that it is difficult to get lost during product slitting, and the half width is preferably 0.16 μm or less, more preferably 0.14 μm or less, and still more preferably 0. It is 12 μm or less.

  In addition, it is preferable that the inert particle β has a sharp particle size distribution, and the evacuation time in vacuum deposition is shortened, and the half width is preferably 0.14 μm or less, more preferably 0.12 μm or less, More preferably, it is 0.1 μm or less.

  Further, as long as the effects of the present invention are not hindered, inert particles having a particle size outside the range defined by α1, α2, and β (hereinafter referred to as inert particles γ) may be contained. However, it is preferable that inert particles having a particle diameter of 1.0 μm or more are not included. Further, the inactive particles γ having a particle size of less than 0.1 μm can be ignored even if they are ignored.

  As the inert particles, α1, α2, and β, for example, calcium carbonate, silica, alumina, polystyrene, alumina silicate, and the like can be used. α1, α2, and β may be the same material. Moreover, it is preferable that α1 and α2 are the same organic particle type because the dropout of particles from the polyester film is reduced.

  In addition to the inert particles, a surfactant, an antistatic agent, various ester components and the like may be added.

  The thickness of the layer B is preferably 3 to 20%, more preferably 4 to 12%, based on the total thickness of the laminated polyester film of the present invention. The thickness of the layer A and the layer B is dominant with respect to the thickness of the entire laminated polyester film, but by making the thickness of the layer B 3% or more of the total thickness, the inactive particles in the layer B are removed. Can be prevented. On the other hand, by setting it to 20% or less, it is possible to prevent the shape of the inert particles in the layer B from causing a protrusion-like deformation on the A-side surface through the layer A.

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

  The laminated polyester film of the present invention is provided with a coating layer on the layer A side. Here, the “layer A side” means that the layer A and the layer B are positioned on the layer A side instead of the layer B side, that is, the covering layer is provided on the layer A side. , Layer B / layer A / coating layer. By providing the coating layer on the layer A side, it is possible to improve running durability with the magnetic head when the magnetic recording tape is formed.

  From the viewpoint of improving running durability, the coating layer preferably contains fine particles and an organic compound.

  Examples of the fine particles include polyacrylic acid, polystyrene, polyethylene, polyester, polyacrylic ester, polymethyl methacrylate, polyepoxy resin, polyvinyl acetate, acrylic-styrene copolymer, acrylic copolymer, and various modified acrylics. Organic compound particles such as resin, styrene-butadiene copolymer, various modified styrene-butadiene copolymers, and inorganic particles such as silica, alumina, calcium carbonate, etc. can be employed. In addition, it is also possible to employ those obtained by coating these fine particles as nuclei and further coated with an organic polymer. The organic polymer that forms the fine particles by covering the nuclei of the fine particles is preferably a self-crosslinkable one in which the terminal group is modified with epoxy, amine, carboxylic acid, hydroxyl group or the like.

  The particle size of the fine particles is preferably 5 to 100 nm, more preferably 8 to 60 nm. By setting the thickness to 5 nm or more, it is possible to prevent the metal thin film layer in the magnetic recording tape from becoming too smooth and lowering the running durability of the magnetic recording tape with the magnetic head. On the other hand, when the thickness is 100 nm or less, it is possible to prevent the surface of the metal thin film layer from being too rough when the magnetic recording tape is used, and an increase in the dropout of the magnetic tape.

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

  The thickness of the coating layer is preferably 4 to 25 nm, more preferably 6 to 15 nm.

Fine surface protrusions are formed by fine particles on the surface of the coating layer, 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 of the coating layer is preferably 3 million to 90 million pieces / mm ^{2, and} more preferably 5 million to 70 million pieces / mm ² . By setting it to 3 million pieces / mm ² or more, it is possible to prevent the metal thin film layer in the magnetic recording tape from becoming too smooth and lowering the running durability of the magnetic tape with respect to the magnetic head. On the other hand, by setting it to 90 million pieces / mm ² or less, it is possible to prevent the dropout of the magnetic tape from increasing due to the surface of the metal thin film layer being too rough when used as a magnetic recording tape.

  In the laminated polyester film of the present invention, it is important that the arithmetic average roughness Ra value of the surface of the coating layer provided on the layer A side is 1.5 to 5 nm, and preferably 2 to 4 nm. Further, it is important that the 10-point average roughness Rz value of the surface of the coating layer is 10 to 60 nm, and preferably 20 to 40 nm.

  When the Ra value is less than 1.5 nm, the metal thin film layer formed by vacuum deposition on the surface of the coating layer is too smooth, and the video thin film is formed by the video head during recording and reproduction in the digital video tape recorder. It 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.

  When the Rz value is less than 10 nm, the metal thin film layer is too smooth, and the durability of the ferromagnetic thin film of the video tape against repeated recording and reproduction by the digital video tape recorder is lowered. On the other hand, if the Rz value exceeds 60 nm, the metal thin film layer becomes too rough and the number of small dropouts (DO) of the video tape increases, making it unsuitable for magnetic recording media.

  The Ra value and Rz value of the surface of the coating layer can be adjusted by adjusting the particle size and addition amount of the fine particles of the coating layer.

  Moreover, it is preferable to provide a slippery coating layer on the surface of the layer B. The slippery coating layer has a function of exhibiting slipperiness between the cooling can and being hard to be scraped, and not allowing degradation products from the polyester film to pass through.

  The slippery coating layer is preferably composed mainly of a water-soluble polymer and / or a water-dispersible polymer and a slippery agent. In the present invention, “and / or” means, for example, that either one of a water-soluble polymer and a water-dispersible polymer may be employed, or both of them may be employed. . The slipperiness of the coating layer is improved by the slippery agent, and traveling with the cooling can and wear resistance are ensured. Moreover, blocking between films when a polyester film is wound is prevented.

  Examples of water-soluble polymers include polyvinyl alcohol, natural rubber such as tragacanth gum and gum arabic, casein, cellulose derivatives such as methylcellulose, hydroxyethylcellulose and carboxymethylcellulose, and water-soluble polyester copolymers such as polyester ether copolymers. Etc. can be used. Among these, a blend of a cellulose derivative and a water-soluble polyester copolymer is particularly preferable. The water-soluble polyester copolymer contributes to increase the adhesion between the cellulose derivative and the polyester film surface, and the cellulose derivative contributes to prevent precipitation of the polyester degradation product.

  As the water-soluble polyester copolymer, for a polyester obtained by polycondensation of a dicarboxylic acid component and a glycol component, for example, a functional acid component such as a dicarboxylic acid component having a sulfonic acid group is added to 5 mol% of the total carboxylic acid component. Water-soluble ones can be preferably employed by copolymerization as described above or by copolymerizing 2 to 70% by weight of a polyalkylene ether glycol component as a glycol component. As the dicarboxylic acid having a sulfonic acid group, 5-sulfoisophthalic acid, 2-sulfoterephthalic acid and the like, metal salts thereof, phosphonium salts and the like can be preferably used, and 5-sodium sulfoisophthalic acid is particularly preferable. As the other dicarboxylic acid component when 5-sodium sulfoisophthalic acid is copolymerized, isophthalic acid, terephthalic acid and the like are preferable, and as the glycol component, ethylene glycol, diethylene glycol and the like are preferable.

  As the water dispersible polymer, polymethyl methacrylate, polyacrylic acid ester, and the like can be used.

  Silicone and fluorine compounds can be used as the lubricant. Further, as the silicone, a polymer such as polydimethylsiloxane in which a large number of organic silicon compounds having a siloxane bond in the molecular skeleton are connected by a covalent bond can be used.

  When silicone is employed as the slippery agent, the slippery coating layer preferably further contains a silane coupling agent. The silane coupling agent contributes to preventing the silicone from being released from the lubricant layer, and further contributes to improving the adhesion between the coating layer and the polyester. Examples of the silane coupling agent include organosilicon monomers having two or more different reactive groups in the molecule. The reactive group is selected from those which bind to the side chain, terminal group and polyester of the water-soluble polymer. One of the reactive groups is a methoxy group, an ethoxy group, a silanol group, and the other reactive group is vinyl. Group, epoxy group, methacryl group, amino group, mercapto group and the like. Examples of the silane coupling agent include 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.

  Cellulose derivative / water-soluble polyester copolymer when a water-soluble polymer blended with a cellulose derivative and a water-soluble polyester copolymer is combined with silicone and a silane coupling agent to form a slippery coating layer The weight ratio of / silicone / silane coupling agent is preferably 100 / (100 to 500) / (1 to 20) / (10 to 50).

  In order to make the slippery coating layer difficult to scrape, it is preferable that particles are not substantially present in the slippery coating layer. In the film forming process, even if particles having a particle size up to about 3 times the thickness of the slippery coating layer are contained in an amount of about 20% by weight with respect to the slippery coating layer, problems such as scraping hardly occur. The slippery coating layer may be substantially free of particles in order to prevent falling off due to scraping with the cooling can and preventing scraping with various transport rolls in the magnetic tape processing process. preferable. However, it is permissible to include particles having a particle diameter equal to or less than the thickness of the easy-slip coating layer. The particles are effective in reinforcing the slippery coating layer.

  The thickness of the easy-slip coating layer is preferably 1 to 10 nm, more preferably 2 to 6 nm. By setting it to 1 nm or more, precipitation of decomposition products from the polyester film can be prevented. Moreover, by setting it as 10 nm or less, it is possible to prevent the slippery coating layer from being scraped or peeled off.

  The arithmetic average roughness Ra value of the surface on the layer B side (hereinafter also referred to as “B-side surface”) is preferably 2 to 30 nm, more preferably 5 to 20 nm. The thickness Rz value is preferably 100 to 400 nm, more preferably 150 to 350 nm. Here, the B side surface indicates the surface of the slippery coating layer when the slippery coating layer is provided.

  Arithmetic average roughness Ra value on the B side surface is 2 nm or more, which means that the shape of protrusions by inert particles on the B side surface of the polyester film during the period when the polyester film is manufactured, slit to 20000 m and left as a product. However, especially in the core part near the bobbin, it is prevented from being transferred to the surface on the A side and giving a dent-like deformation to the surface on the A side, and after vacuum deposition, the dent-like deformation remains in the ferromagnetic metal thin film layer. This is preferable for preventing the electromagnetic conversion characteristics from deteriorating and the dropout from increasing. Further, setting the arithmetic average roughness Ra value of the B side surface to 30 nm or less means that during the standing period as described above, the roughness of the B side surface of the polyester film is transferred to the A side surface and the surface undulation of the A side surface is caused. It is preferable to prevent the increase and the surface waviness of the ferromagnetic metal surface layer is increased after the vacuum deposition, thereby preventing the electromagnetic conversion characteristics of the digital video tape from deteriorating and increasing the dropout.

  Setting the Rz value on the B-side surface to 100 nm or more is preferable for preventing the film from straying in the lateral direction. Moreover, it is preferable that the Rz value on the B side surface is 400 nm or less in order to prevent the roughness of the B side surface from being transferred to the magnetic metal surface.

  As the total thickness of the laminated film of the present invention formed by laminating the layer A, the layer B, the coating layer on the layer A side, etc., preferably 3.0 to 10.0 μm, more preferably 4.0 to 9.0 μm, More preferably, it is 4.4-8.7 micrometers. By setting the thickness to 3.0 μm or more, it is possible to prevent the bending rigidity from being lowered and the output of the magnetic recording tape 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 capacity per cassette can be increased.

  The laminated polyester film of the present invention can be suitably used as a base film for magnetic recording tape.

  That is, the magnetic recording tape of the present invention is obtained by using the laminated polyester film of the present invention and providing a metal thin film layer on the coating layer on the layer A side.

  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, more preferably 80 to 200 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 laminated polyester film. The back coat layer is composed of solid fine particles and a binder, and various additives may be added as necessary, and known ones 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, an example of a method for producing the laminated polyester film and the magnetic recording tape of the present invention will be described.

  The material of the inert particles such as calcium carbonate, silica, alumina, polystyrene, and alumina silicate used for the B layer of the laminated polyester film of the present invention may be a natural product or a synthetic product, but has a sharp particle size distribution. In order to obtain inert particles having a uniform diameter, a synthetic product is preferable. For example, commercially available inert particles may be used. The alumina silicate particles can be produced, for example, by a reaction between sodium silicate and sodium aluminate. The polystyrene particle is preferably a cross-linkable curable type, and the particle is mainly composed of styrene or a derivative thereof. The seed particle is synthesized by soap-free emulsion polymerization of styrene and has a molecular weight of about an oligomer. Spherical crosslinked polystyrene particles having a sharp particle size distribution can be preferably employed by swelling with a swelling aid and absorbing and polymerizing styrene and divinylbenzene. Silica can be prepared by neutralizing or decomposing a sodium silicate aqueous solution with an acid or alkali metal salt.

  The above inert particles used for the B layer of the laminated polyester film of the present invention can be added to and mixed with the polyester by various known methods. Among these, it is particularly preferable from the viewpoint of particle dispersibility that it is added before the start of polymerization of the polyester at a stage during the polymerization reaction. The addition of the particles in the precursor stage or polycondensation stage for producing the polyester composition is preferably carried out as an ethylene glycol slurry. The slurry concentration is preferably about 0.5 to 20% by weight. For dispersion in a dispersion medium such as ethylene glycol, for example, a high-speed disperser, a sand mill, a roll seal, or the like may be used. When dispersed, phosphorus atom-containing compounds such as phosphoric acid, phosphorous acid, sodium hexametaphosphate, nitrogen atom-containing compounds such as tetraethylammonium hydroxide, hydroxylamine, alkali compounds, cations, anions, amphoteric or nonionic The use of a dispersant such as a surfactant or a water-soluble polymer is particularly preferred because the dispersibility of the inert particles in the slurry and polymer is further improved.

  For example, the raw material for layer A from which contained particles are removed as much as possible, and the raw material for layer B in which the inert particles α1, α2, and β are added in accordance with a desired content within the specified range. Are co-extruded and cooled and solidified on a casting drum to form an unstretched film sheet in which layers A and B are laminated. This is uniaxially stretched in the longitudinal direction or the width direction of the process, and a coating solution for forming a slippery coating layer is applied to the surface of the B layer, and preferably a coating solution for forming a coating layer is applied to the surface of the A layer. Then, the film is dried and then stretched and oriented in a direction perpendicular to the previous uniaxial stretching direction and heat-set. In such a production process, the laminated polyester film of the present invention can be produced by adjusting the production conditions so as to satisfy the characteristics of the laminated polyester film of the present invention.

  As the coating liquid applied on the layer B, the aqueous liquid of the material for the easy-sliding coating layer described above can be used.

  In order to form the coating layer on the layer A side, the following operation may be performed. A coating solution containing 0.1 to 6.0% by weight, preferably 0.3 to 3.0% by weight, of the solid content of the coating layer is applied to the surface of layer A side of the smooth polyester film after being stretched in one direction. To do. By doing so, a coating layer having fine surface protrusions on the layer A side can be formed.

The number of fine surface protrusions and the like of the coating layer can be adjusted by adjusting the kind of fine particles, average particle diameter, addition concentration, solid content coating concentration, and the like. For example, in order to set the number of fine surface protrusions to 3 million to 90 million pieces / mm ² , the content of fine particles having the above average particle diameter is 1.0 to 15.0% by weight with respect to the coating liquid, Preferably it is good to set it as 3.0 to 10.0 weight%.

  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 coating method of the coating liquid, a doctor blade method, a gravure method, a reverse roll method, a metering bar method, an air knife method, or the like can be employed.

  In the production of the magnetic recording tape of the present invention, the metal thin film can be provided by vacuum deposition.

  The backcoat layer can be provided by applying a solution comprising solid fine particles and a binder to which various additives are added as necessary.

  And it can be set as a magnetic recording tape by cut | disconnecting to predetermined tape width.

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

(2) Particle size a) Particle size of inert particles and fine particles in the state of powder before being added to the film The particle size was determined for each type of particle. Disperse the powder of particles on the transmission electron microscope test stand so that the particles do not overlap as much as possible, and observe with a transmission electron microscope at a magnification of about 1 million times. At least 100 particles are equivalent to an area circle The diameter was determined, and the number average value was used as the particle diameter. The standard deviation of the equivalent circle diameter was also determined.

  When determining the particle size from the film, the inert particles in the layer B can also be determined by the following method b), and the fine particles in the coating layer on the layer A side are determined by the following method. It has been empirically confirmed that it can be assumed that the particle diameter of the surface protrusion obtained by c) is equal.

b) 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 Co., and the polyester around the inert particles is ashed. Inactive particles are exposed, and a gold thin film deposition layer is provided on the surface thereof with a gold sputtering apparatus at 20 to 30 nm, and observed with a scanning electron microscope at a magnification of about 100,000 times. At least 100 particles have an area circle The equivalent diameter is obtained and used as the particle diameter of the inert particles in the layer B. The area circle equivalent diameter is plotted on the horizontal axis, and the number of detected particles corresponding to each area circle equivalent diameter is plotted on the vertical axis, and the particle size distribution of the inert particles is obtained by histogram every 0.01 μm. β, α2, and α1 are classified.

  The content is the cube of the area equivalent circle diameter from the above histogram, converted to volume, the density is converted into volume fractions of α1, α2, and β using the representative values of each particle, and the total particle content is calculated. The weight fraction of α1, α2, and β is calculated by fluorescent X-ray or the like.

c) Particle size of surface protrusion of coating layer on 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 a magnification of about 100,000 times with a scanning electron microscope. The area equivalent circle diameter is determined for at least 100 particles, and the value obtained by subtracting 2χ nm from the number average value is defined as the particle size.

(3) Arithmetic average roughness Ra value, 10-point average roughness Rz value Measured using an 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. The Ra value is calculated from the corresponding arithmetic average roughness, and the ten-point average surface roughness corresponding to JIS B0601 Rz, that is, the average surface of the portion extracted from the roughness curved surface by the reference area is used as the reference surface, from the highest to the fifth. Rz value was calculated | required from the distance of the average value of the altitude of a mountain, and the average value of the depth of the valley bottom from the deepest. 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.

(4) Number of fine surface protrusions on the film The surface of the film was observed with a scanning electron microscope at a magnification of 50,000 times over 10 views (the area of one view is 2 × 2 μm ² ). The number was counted and converted to the number per 1 mm ² .

(5) Time roll of product roll After slitting a roll of 20000 m or more, it was allowed to stand at room temperature for 24 hours, and the core was destructively inspected, and the presence or absence of vertical wrinkle generation in the longitudinal direction of the film roll was evaluated according to the following criteria.
XX: Vertical wrinkles occurred over the entire length from the surface layer to the core over half the film width.
X: Vertical wrinkles were generated from the surface layer to a part of the core over half of the film width.
Δ: Vertical wrinkles were generated from the surface layer to a part of the core in a portion less than half of the film width.
○: No vertical wrinkle from the surface layer to the core.

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

[Example 1]
As a raw material of layer A (raw material A), polyethylene terephthalate (inherent viscosity 0.66) containing substantially no inert particles was prepared.

  As the raw material of layer B (raw material B), spherical particles having an average particle diameter of 450 nm (standard deviation 16 nm) as inert particles α1 (0.001 wt% of spherical particles of crosslinkable curable polystyrene) and inert particles α2 0.05% by weight of spherical particles of crosslinkable curable polystyrene having an average particle size of 320 nm (standard deviation 15 nm), and aluminum silicate having an average particle size of 190 nm (standard deviation 10 nm) as inert particles β (Si: 27% by weight, Polyethylene terephthalate (intrinsic viscosity 0.66) to which 0.41 wt% of particles of Al: 15 wt% and Na: 5 wt% was added was prepared.

Further, an aqueous solution having the following composition and concentration was prepared as a coating liquid (coating liquid C) for forming a coating layer on the layer A side.
Methyl cellulose (methoxyl group substitution degree 1.8, molecular weight 20000)
: 0.10% by weight
Water-soluble polyester (1: 1 copolymer of 70 mol% terephthalic acid, 30 mol% 5-sodium sulfoisophthalic acid and ethylene glycol)
: 0.30% by weight
Aminoethylsilane coupling agent (3-aminopropyltrimethoxysilane)
: 0.01% by weight
Fine particles (silica with an average particle size of 12 nm (standard deviation 0.3 nm))
: 0.03% by weight
Raw material A and raw material B were coextruded at a thickness ratio of 11: 1. The total discharge amount of A and B was finely adjusted so that the total thickness of the laminated polyester film became a target value (6.3 μm) described later.

  This was cooled and solidified on a casting drum, and longitudinally stretched 3.0 times at 110 ° C. by a roll stretching method.

  Subsequently, the coating liquid C was apply | coated to the surface of A layer by the metal ring bar system with the application | coating thickness of 4.0 micrometers.

  Thereafter, the film was stretched 3.3 times in the transverse direction at 98 ° C. with a stenter, heat-treated at 200 ° C., wound around an intermediate spool, slit into a width of 620 mm with a slitter, wound into a roll around a cylindrical core, thickness 6 A laminated polyester film of the present invention was obtained in which a 3 μm film was wound into a roll having a length of 20000 m.

A cobalt-oxygen thin film having a thickness of 110 nm was formed on the surface of the polyester film on the layer A side as a ferromagnetic metal thin film layer by vacuum deposition. The pressure in the vacuum oven after evacuation for 1 hour was 10 ⁻⁵ Pa.

  Next, a diamond-like carbon film having a thickness of 10 nm was formed on the cobalt-oxygen thin film layer by sputtering.

Subsequently, carbon black (particle diameter 23 nm, specific surface area 130 m ² / mg), copolymer polyester resin (urethane modified copolymer polyester, molecular weight 40,000, Tg 80 ° C.), silicone (with a polymerization degree of 100) are formed on the surface on the layer B side. A backcoat layer having a weight ratio of 100: 50: 2 (dimethylpolysiloxane, one in which 202 of 202 methyl groups were replaced with amino groups) was provided at a thickness of 400 nm.

  This was slit with a slitter to a width of 6.35 mm, wound on a reel, and the magnetic tape of the present invention was produced.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Further, the Ra value and Rz value of the surface on the layer B side of the laminated polyester film were 8 nm and 190 nm.

[Example 2]
In the production of the laminated polyester film of Example 1,
The raw materials A and B were changed from polyethylene terephthalate to polyethylene-2,6-naphthalate (inherent viscosity IV0.70),
The coating thickness of the coating liquid C on the surface of the layer A is 8.0 μm,
The longitudinal stretching temperature and magnification are 135 ° C. and 5.0 times,
The transverse stretching is a two-stage stretching at a temperature and a magnification of 135 ° C, 6.0 times and 160 ° C, 1.2 times,
Otherwise, a film having a thickness of 4.2 μm was obtained in the same manner as in Example 1.
Further, a magnetic recording tape was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Further, the Ra value and Rz value of the surface on the layer B side of the laminated polyester film were 7 nm and 170 nm.

[Example 3]
In the production of the laminated polyester film of Example 1, 0.02% by weight of silica having an average particle diameter of 60 nm (standard deviation 3 nm) was added to the raw material A, and the others having the thickness of 6.3 μm were the same as in Example 1. An inventive laminated polyester film was obtained.
Further, a magnetic recording tape was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 190 nm.

[Example 4]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles β to the raw material B was 0.50% by weight, and the others were the same as in Example 1 except that the laminated polyester of the present invention having a thickness of 6.3 μm was used. A film was obtained.
Further, a magnetic recording tape was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Further, the Ra value and Rz value of the surface on the layer B side of the laminated polyester film were 8 nm and 190 nm.

[Example 5]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α2 with respect to the raw material B was 0.10% by weight, and the others were the same as in Example 1 to obtain a laminated polyester film having a thickness of 6.3 μm. It was.
Further, a magnetic recording tape was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. The Ra value and Rz value of the surface B on the layer B side of the laminated polyester film were 10 nm and 190 nm.

[Example 6]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α1 to the raw material B was 0.002% by weight, and the others were the same as in Example 1 and the laminated polyester film of the present invention having a thickness of 6.3 μm. Got.
Further, a magnetic recording tape was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. The Ra value and Rz value of the surface on the layer B side of the laminated polyester film were 9 nm and 290 nm.

[Example 7]
In the production of the laminated polyester film of Example 1, the thickness ratio of the coextrusion of the raw material A and the raw material B was 8: 1, and the others were the same as in Example 1, and the laminated polyester film of the present invention having a thickness of 6.3 μm. Got.
Further, a magnetic recording tape was prepared in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. The Ra value and Rz value of the surface B on the layer B side of the laminated polyester film were 9 nm and 190 nm.

[Comparative Example 1]
In the production of the laminated polyester film of Example 1, the coating thickness of the coating liquid C was 2.0 μm, and the others were the same as in Example 1 to obtain a laminated polyester film having a thickness of 6.3 μm.
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 190 nm.

[Comparative Example 2]
In the production of the laminated polyester film of Example 1, the addition amount of methylcellulose with respect to the coating liquid C was 0.15% by weight, and a laminated polyester film having a thickness of 6.3 μm was obtained in the same manner as in Example 1.
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 190 nm.

[Comparative Example 3]
In the production of the laminated polyester film of Example 1, the amount of fine particles (silica) added to the coating liquid C was 0.02% by weight, and the others were the same as in Example 1 except that a laminated polyester film having a thickness of 6.3 μm was obtained. Obtained.
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 190 nm.

[Comparative Example 4]
In the production of the laminated polyester film of Example 1, 0.03% by weight of silica having an average particle size of 24 nm (standard deviation 0.5 nm) was added as fine particles for the coating liquid C instead of those of Example 1. Otherwise, a laminated polyester film having a thickness of 6.3 μm was obtained in the same manner as in Example 1.
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 190 nm.

[Comparative Example 5]
In the production of the laminated polyester film of Example 1, in place of the inert particles α1 added to the raw material B, 0.001% by weight of spherical particles of crosslinkable curable polystyrene having an average particle size of 380 nm (standard deviation 0.5 nm). Added. Otherwise, a laminated polyester film having a thickness of 6.3 μm was obtained in the same manner as in Example 1.
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 190 nm.

[Comparative Example 6]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α1 with respect to the raw material B was 0.0003 wt%, and the others were obtained in the same manner as in Example 1 to obtain a laminated polyester film having a thickness of 6.3 μm. .
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 80 nm.

[Comparative Example 7]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α1 with respect to the raw material B was 0.015% by weight, and the others were the same as in Example 1 to obtain a laminated polyester film having a thickness of 6.3 μm. .
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 430 nm.

[Comparative Example 8]
In the production of the laminated polyester film of Example 1, in place of the inert particles α1 added to the raw material B, 0.001% by weight of spherical particles of crosslinkable curable polystyrene having an average particle diameter of 1100 nm (standard deviation 50 nm) was added. . Otherwise, a laminated polyester film having a thickness of 6.3 μm was obtained in the same manner as in Example 1.
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 37 nm and 590 nm.

[Comparative Example 9]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α2 to the raw material B was 0.006% by weight, and the others were the same as in Example 1 except that the laminated polyester film having a thickness of 6.3 μm and the magnetic recording were used. I tried to manufacture the tape, but the film was lost at the slit and the end face was uneven.

  Table 1 shows the characteristics of the obtained laminated polyester film. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 6 nm and 80 nm.

[Comparative Example 10]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α2 with respect to the raw material B was 0.75% by weight, and the others were obtained in the same manner as in Example 1 to obtain a laminated polyester film having a thickness of 6.3 μm. .
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 24 nm and 590 nm.

[Comparative Example 11]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles β with respect to the raw material B was 0.15% by weight, and the others were the same as in Example 1 to obtain a laminated polyester film having a thickness of 6.3 μm. .
Further, a magnetic recording tape was obtained in the same manner as in Example 1. However, the pressure in the vacuum oven after evacuation for 1 hour was 10 ⁻⁴ Pa, and a longer evacuation time was required than in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 8 nm and 170 nm.

[Comparative Example 12]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles β to the raw material B was 1.65% by weight, and the others were the same as in Example 1 to obtain a laminated polyester film having a thickness of 6.3 μm. .
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 34 nm and 340 nm.

[Comparative Example 13]
In the production of the laminated polyester film of Example 1, in place of the inert particles β added to the raw material B, aluminum silicate having an average particle diameter of 80 nm (standard deviation 1.5 nm) (the composition is that employed in Example 1) The same) was added at 1.00% by weight. Otherwise, a laminated polyester film having a thickness of 6.3 μm was obtained in the same manner as in Example 1.
Further, a magnetic recording tape was obtained in the same manner as in Example 1. However, the pressure in the vacuum oven after evacuation for 1 hour was 10 ⁻⁴ Pa, and a longer evacuation time was required than in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 17 nm and 240 nm.

[Comparative Example 14]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α2 to the raw material B was 0.04% by weight, the addition amount of the inert particles β was 0.30% by weight, and the others were the same as in Example 1. Then, production of a laminated polyester film and a magnetic recording tape having a thickness of 6.3 μm was attempted, but the deposition was abandoned because the film was greatly lost due to slits and the end faces were uneven.

  Table 1 shows the characteristics of the obtained laminated polyester film. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 6 nm and 110 nm.

[Comparative Example 15]
In the production of the laminated polyester film of Example 1, the addition amount of the inert particles α1 to the raw material B is 0.01% by weight, the addition amount of the inert particles α2 is 0.60% by weight, and the addition amount of the inert particles β is A laminated polyester film having a thickness of 6.3 μm was obtained in the same manner as in Example 1 except that the amount was 1.50% by weight.
Further, a magnetic recording tape was obtained in the same manner as in Example 1.

  Tables 1 and 2 show the characteristics of the obtained laminated polyester film and magnetic recording tape. Moreover, Ra value and Rz value of the B side surface of a laminated polyester film were 34 nm and 440 nm.

  In Table 1, [α1], [α2], and [β] are those added as inert particles corresponding to α1, α2, and β defined in the present invention in the examples and some comparative examples. In other comparative examples, those added in place of α1, β, etc. in Example 1 are shown. The total content is the total content of [α1], [α2], and [β].

  In the examples, the laminated polyester film of the present invention does not generate vertical wrinkles over time, and the evacuation time does not increase. We were able to.

  The present invention can be used for a magnetic recording tape such as a vapor deposition type and a coating type, and can be suitably used particularly for a vapor deposition type magnetic recording tape such as a digital video tape.

Claims (9)

A laminated polyester film comprising layer A and layer B which are two polyester layers,
In layer B,
The content of the inert particles β having a particle size of 0.1 μm or more and less than 0.22 μm is 0.2 to 1.6% by weight with respect to the layer B,
The content of the inert particles α2 having a particle size of 0.22 μm or more and less than 0.4 μm is 0.01 to 0.7% by weight with respect to the layer B,
The content of the inert particles α1 having a particle size of 0.4 μm or more and less than 1.0 μm is 0.0005 to 0.01% by weight with respect to the layer B,
The total content of the inert particles α1, α2 and β is 0.4 to 2.0% by weight based on the layer B;
A coating layer is provided on the layer A side,
And the arithmetic mean roughness Ra value of the surface of the said coating layer is 1.5-5 nm, and 10-point average roughness Rz value is 10-60 nm, The laminated polyester film characterized by the above-mentioned. The laminated polyester film according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. The laminated polyester film according to claim 1 or 2, wherein at least one of the inert particles α1, α2, and β contains organic particles. The laminated polyester film according to any one of claims 1 to 3, wherein the coating layer provided on the layer A side contains fine particles and an organic compound. The laminated polyester film according to claim 4, wherein the average particle diameter of the fine particles in the coating layer is 5 to 100 nm. The laminated polyester film according to any one of claims 1 to 5, which is used for a magnetic recording tape. A magnetic recording tape using the laminated polyester film according to claim 1, wherein a metal thin film layer is provided on the coating layer on the layer A side. The magnetic recording tape according to claim 7, wherein the metal thin film layer is a ferromagnetic metal thin film layer. The magnetic recording tape according to claim 7 or 8, wherein the metal thin film layer has a thickness of 20 to 300 nm.