JP2006027097A - Biaxially oriented laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented laminated polyester film capable of having excellent slit properties in an obtained magnetic recording medium while suppressing occurrence of dropout due to coarse foreign matters and oligomers.
SOLUTION: A catalyst having a thickness of 2.5 μm or more is a germanium compound, and a catalyst having a thickness of 2 μm or less is composed of a titanium compound and an antimony compound on one side of a layer A made of a polyester composition A having an intrinsic viscosity of 0.62 or more. Inactive particles B having a titanium compound content of 1 to 15 ppm, an antimony compound of 40 to 160 ppm of antimony compound, a phosphorus compound of 10 to 200 ppm of phosphorus element content, and an average particle size of 50 to 1000 nm of 0. A biaxially oriented laminated polyester film in which a layer B comprising a polyester composition B having an intrinsic viscosity of 0.59 or less contained in an amount of 001 to 1% by weight and having a difference in intrinsic viscosity of 0.10 at most is 0.10.
[Selection figure] None

Description

  The present invention relates to a biaxially oriented laminated polyester film and a magnetic recording medium using the same. More specifically, the present invention relates to a biaxially oriented laminated polyester film capable of providing the obtained magnetic recording medium with few dropouts, excellent tape slitting properties and electromagnetic conversion characteristics, and a magnetic recording medium using the same.

  Digital video tapes for consumer use put into practical use in 1995 are made by depositing a Co metal magnetic thin film on a 6-7 μm thick base film by vacuum deposition, and coating the surface with a diamond-like carbon (DLC) film. In the case of a camera-integrated video using a DV mini-cassette, the basic specification (SD specification) has a recording time of 1 hour.

  This digital video cassette (DVC) is the world's first home digital video cassette, a. A small body can record a huge amount of information, b. Since the signal does not deteriorate, the image quality and sound quality will not deteriorate even after many years c. Enjoy high image quality and high sound quality because it is not affected by noise, d. It has the advantage that the video does not deteriorate even if dubbing is repeated, and the market is highly evaluated.

  Incidentally, recent magnetic recording media have a high recording density in order to record enormous information, and the surface of a support constituting the magnetic recording medium has been required to be extremely flat. In response to such a request, in Patent Document 1 (WO88 / 8437 pamphlet) and Patent Document 2 (Japanese Patent Laid-Open No. 2000-15695), each layer of the laminated film is made of polyester using a germanium compound as a polymerization catalyst. Thus, it has been proposed that coarse foreign matter can be reduced and dropout can be reduced when a magnetic recording medium is used.

  However, although these biaxially oriented laminated polyester films can reduce dropout due to coarse foreign matter, oligomers in the polyester tend to precipitate on the film surface over time after film formation, and tapes made from the base film The dropouts tended to increase. On the other hand, if the polyester constituting the base film is subjected to solid phase polymerization in order to reduce the oligomers present in the polyester, although the precipitated oligomers are reduced, the slit property at the time of tape processing is deteriorated and the productivity is deteriorated. There were drawbacks.

WO88 / 8437 pamphlet JP 2000-15695 A

  An object of the present invention is to solve the problems of the above-mentioned conventional biaxially oriented laminated polyester film, and to provide a magnetic recording medium that has not only coarse foreign matters but also less dropout due to oligomers and also has excellent slit properties. An object of the present invention is to provide a biaxially oriented laminated polyester film that can be produced.

  According to the present invention, an object of the present invention is a biaxially oriented laminated polyester film in which a polyester layer B having a thickness of 2 μm or less is laminated on one side of a polyester layer A having a thickness of 2.5 μm or more, The polyester layer A is composed of a polyester composition A having an intrinsic viscosity of 0.62 or more, in which the polycondensation reaction catalyst is a germanium compound, and the polyester layer B is composed of a titanium compound and an antimony compound, and the titanium compound Polyester having an intrinsic viscosity of 0.59 or less, containing 1 to 15 ppm in terms of titanium element, 40 to 160 ppm in terms of antimony element content, and 10 to 200 ppm in terms of phosphorus element content. Composition B, and polyester composition B has an average particle size of 50-1 based on the weight of the composition. This is achieved by a biaxially oriented laminated polyester film containing 0.001 to 1% by weight of 000 nm inert particles B and having a difference in intrinsic viscosity of 0.10 at most with the polyester composition A.

  According to the present invention, as a preferred embodiment of the present invention, the binder resin C, the inert particles C, the surfactant C, and the siloxane copolymer acrylic resin are formed on the surface of the polyester layer A that is not in contact with the polyester layer B. The polyester film B is an ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol, based on the weight of the composition. Containing 0.001 to 10% by weight, the binder resin C being at least one water-soluble or water-dispersible resin selected from the group consisting of an acrylic resin, a polyester resin and an acrylic-polyester resin, inert particles C has an average particle diameter of 5 to 100 nm and a ratio of 0.5 to 30% by weight present in the coating layer C; The ratio of the xanthene copolymer acrylic resin C present in the film layer C is 1 to 30% by weight, and the surface on the polyester layer A side has a center line average roughness WRaA of 0.5 to 2.5 nm. The polyester layer B side surface has a center line average roughness WRaB in the range of 2 to 20 nm, the polyester composition A substantially does not contain inert particles, the polyester composition A Alternatively, there is also provided a biaxially oriented laminated polyester film comprising at least one of the polyester composition B being a polyester composition comprising polyethylene terephthalate and being used as a support for a vapor deposition type magnetic recording medium.

  Furthermore, according to the present invention, there is also provided a magnetic recording medium comprising the biaxially oriented laminated polyester film of the present invention and a metal thin film provided on one surface thereof.

  Since the biaxially oriented laminated polyester film of the present invention has less precipitation of coarse foreign matter and oligomers, the resulting magnetic recording medium has less dropout, excellent electromagnetic conversion characteristics, and also has slitting properties when taped. That is, both quality and productivity are excellent, and its industrial value is extremely high.

  The biaxially oriented laminated polyester film of the present invention is a biaxially oriented laminated polyester film in which a polyester layer B made of a polyester composition B containing inert particles B is laminated on one side of a polyester layer A made of a polyester composition A. Preferably, it is a biaxially oriented laminated polyester film in which a coating layer C is provided on the surface of the polyester layer A that is not in contact with the polyester layer B.

  In the present invention, the polyester constituting the polyester compositions A and B is not particularly limited, and may be an aliphatic polyester or an aromatic polyester, and is preferably an aromatic polyester. The polyester compositions A and B may be made of the same kind of polyester or different kinds of polyester.

  Examples of the aromatic polyester include polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalate (polyethylene-2,6-naphthalenedicarboxylate). Etc. can be exemplified. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable, and polyethylene terephthalate is particularly preferable because an effect of reducing oligomers is easily produced.

  These polyesters may be homopolyesters or copolyesters. In the case of a copolyester, for example, as a copolymerization component of polyethylene terephthalate or polyethylene-2,6-naphthalate, diethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyethylene glycol, 1,4-cyclohexanedi Other diol components such as methanol and p-xylylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (in the case of polyethylene-2,6-naphthalate), 2,6-naphthalenedicarboxylic acid ( However, in the case of polyethylene terephthalate), other dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, oxycarboxylic acid components such as p-oxyethoxybenzoic acid, and the like. The amount of these copolymer components is preferably 20 mol% or less, more preferably 10 mol% or less, as long as the effects of the present invention are not impaired. Furthermore, trifunctional or more polyfunctional compounds such as trimellitic acid, pyromellitic acid and pentaerythritol can be copolymerized. In this case, the copolymer is preferably copolymerized in an amount that is substantially linear, for example, 2 mol% or less. The copolymer component in the case of polyester other than polyethylene terephthalate and polyethylene-2,6-naphthalate may be considered in the same manner as described above.

  The polyester compositions A and B are added such as pigments, dyes, antioxidants, antistatic agents, light stabilizers, light-shielding agents (for example, carbon black, titanium oxide, etc.) as long as the object of the present invention is not impaired. Agents and other resins can be included as necessary.

  In the biaxially oriented laminated polyester film of the present invention, the polyester layer A and the polyester layer B are preferably made of the same polyester, but may be made of different polyesters. For example, a laminated film in which both the polyester layer A and the polyester layer B are made of polyethylene terephthalate or polyethylene-2,6-naphthalate is preferable, but the polyester layer A (or polyester layer B) is polyethylene terephthalate and the polyester layer B (or polyester layer A). ) May be a laminated film made of polyethylene-2,6-naphthalate.

  The polyester can be produced by a conventionally known method. For example, polyethylene terephthalate can be produced by a method in which terephthalic acid and ethylene glycol are esterified, or dimethyl terephthalate and ethylene glycol are transesterified, and then the reaction product is polycondensed. In addition, when going through transesterification, the transesterification catalyst known per se can be used. Specific examples of the transesterification reaction catalyst include manganese, calcium, magnesium, titanium oxides, chlorides, carbonates, carboxylates, and the like, and particularly acetates, that is, manganese acetate, calcium acetate, magnesium acetate, titanium acetate. Is preferred.

The polyester compositions A and B in the present invention will be described in detail below.
First, the polyester composition A has an intrinsic viscosity of 0.62 or more when formed into a film. Preferably, it is 0.64 or more. When the intrinsic viscosity of the film is equal to or higher than the lower limit, there are few regenerated oligomers due to hydrolysis and thermal decomposition of the polymer during extrusion melting, and dropout (D / O) can be suppressed when the magnetic recording medium is obtained. In order to obtain such an intrinsic viscosity, for example, polyester having an intrinsic viscosity of 0.8 or more is formed into chips by solid phase polymerization, and the final polyester has a moisture content of 0.01 to 0.3 weight. %, Drying at 170 ° C. for 6 hours or more, and melt extrusion at 280 ° C. to 310 ° C. for 20 minutes or more.

  The polyester composition A is made of polyester using a germanium compound as a polycondensation reaction catalyst. That is, by using a germanium compound as a catalyst and setting the intrinsic viscosity of the polymer constituting the layer A to 0.62 or more, not only coarse foreign matters can be reduced, but also the polyester layer B as well as the surface of the polyester layer A after film formation. It is possible to reduce oligomers precipitated from the surface of the surface.

  Examples of the germanium compound used as the polycondensation reaction catalyst include those described in Japanese Patent No. 2792068. More specifically, (a) amorphous germanium oxide, (b) crystalline germanium, (c) a solution of germanium oxide dissolved in glycol in the presence of an alkali metal, an alkaline earth metal or a compound thereof, and (d) Examples thereof include a solution of germanium oxide in a solution prepared by dissolving germanium oxide in water and adding glycol thereto to distill off water. When the amount of the germanium compound is excessively large, a large amount of DEG is produced as a by-product during the reaction, and the thermal stability of the polyester composition A is lowered. Therefore, the ratio of the germanium compound contained in the polyester composition A is preferably at most 50 ppm in terms of germanium element (Ge) based on the weight of the composition A, and more preferably 45 ppm or less. On the other hand, the lower limit of the ratio of the germanium compound is preferably 20 ppm or more, and more preferably 35 ppm or more from the viewpoint of promptly proceeding the reaction.

  In the present invention, the polyester composition A preferably contains a phosphorus compound that is conventionally added in the production process of a polyester in order to maintain thermal stability. Although this phosphorus compound is not particularly limited, orthophosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate and the like are preferable.

  By the way, it is preferable that the polyester layer A does not substantially contain particles because electromagnetic conversion characteristics can be improved. However, a small amount of inert fine particles A can be contained in order to provide running durability when a magnetic recording medium is used. As the size of the fine particles at that time, the average particle size is preferably 30 to 200 nm or less, and the addition amount is 0.001 to 0.2 wt% or less (relative to the layer A) to deteriorate the electromagnetic conversion characteristics. Therefore, it is preferable because both driving durability can be achieved.

  Examples of the types of the inert particles A include (1) heat-resistant polymer particles (for example, crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, crosslinked). Particles made of polyester, etc.), (2) metal oxides (eg, aluminum oxide, titanium dioxide, silicon dioxide (silica), magnesium oxide, zinc oxide, zirconium oxide, etc. (for layer A)), (3) metal Carbonates (eg, magnesium carbonate, calcium carbonate, etc.), (4) metal sulfates (eg, calcium sulfate, barium sulfate, etc.), (5) carbon (eg, carbon black, graphite, diamond, etc.), and ( 6) Clay minerals (eg kaolin, clay, bentonite) It includes fine particles of inorganic compounds such as etc.). Among these, at least one particle selected from the group consisting of a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, a crosslinked polystyrene, aluminum oxide, titanium dioxide, silicon dioxide, kaolin, and clay is particularly preferable. Of course, particles other than the above-mentioned types may be further added as long as the film properties are not adversely affected.

  Next, the polyester composition B comprises a titanium compound having a titanium element amount of 1 to 15 ppm and an antimony element amount of 40 to 160 ppm as a polycondensation reaction catalyst, and a phosphorus compound having a phosphorus element amount of 10 to 200 ppm as a thermal stabilizer. And a polyester composition having an intrinsic viscosity of 0.59 or less. By setting the amount of titanium element and antimony element as the polycondensation reaction catalyst residue and the amount of phosphorus element as the stabilizer in the polyester composition B within the above ranges, the antimony compound is used as the polycondensation reaction catalyst. While being used, the generation of coarse foreign matter is suppressed, and even when the intrinsic viscosity is as low as 0.59 or less, the occurrence of foreign matter due to thermal degradation during melting, and the resulting protrusions, cooling during deposition Problems such as lowering the adhesion to the can and transferring to the magnetic layer surface side to lower the electromagnetic conversion characteristics can be suppressed. In addition, the difference of the specific year of the polyester composition A and the polyester composition B is 0.10 at most, and when this is exceeded, the below-mentioned slit property improvement effect and the inhibitory effect of an oligomer may not fully be expressed.

  More specifically, when the amount of titanium element is less than the lower limit, a large amount of antimony compound is required to sufficiently advance the reaction of the polyester, and as a result, coarse foreign matters due to the catalyst are likely to be generated. If it seems to exceed the upper limit, foreign matter is likely to be generated due to thermal deterioration during melting. Further, if the amount of the above-described antimony element is less than the lower limit, a large amount of a titanium compound is necessary to sufficiently advance the reaction of the polyester, and foreign matter is likely to be generated due to heat deterioration at the time of melting, while the upper limit. If it exceeds 1, coarse foreign matters resulting from the catalyst tend to be generated. Further, if the amount of phosphorus element is less than the lower limit, foreign matters are likely to be generated due to thermal deterioration during melting, while if it exceeds the upper limit, coarse foreign matters are likely to be generated due to the catalyst. From these points, the value obtained by dividing the amount of antimony element (ppm) by the amount of titanium element (ppm) is preferably in the range of 4 to 80, more preferably 5 to 70. Furthermore, if the intrinsic viscosity exceeds the upper limit, the slit cross-sectional shape becomes worse at the time of tape formation, and scraping powder is generated. As a method for adjusting the intrinsic viscosity of the film, for example, the intrinsic viscosity of the polymer used is adjusted to 0.62 or less, and the melt intrinsic temperature is 280 to 310 ° C. for 20 minutes or more to achieve the desired intrinsic viscosity. it can. The amounts of these titanium elements, antimony elements, and phosphorus elements do not have to be satisfied from the polymerization stage, and may be satisfied as a result of mixing the polyesters obtained using the respective polymerization catalysts. In addition, when a titanium compound and an antimony compound are not used as the polycondensation reaction catalyst, for example, when a germanium compound is used, the proportion of diethylene glycol present in the polyester increases, and as a result, the contained inert particles easily fall off. Thus, dropout may occur when the magnetic recording medium is used.

  Preferred examples of the antimony compound include antimony trioxide, antimony pentoxide, and antimony acetate.

  Preferred examples of the titanium compound include organic titanium compounds, such as those described in JP-A-5-298670. More specifically, titanium alcoholate, organic acid salt, reaction product of tetraalkyl titanate and aromatic polyvalent carboxylic acid or anhydride, etc. can be exemplified, and preferred examples include titanium tetrabutoxide, titanium isopropoxide, titanium oxalate. , Titanium acetate, titanium benzoate, trimellitic acid titanium, a reaction product of tetrabutyl titanate and trimellitic anhydride, and the like.

  The phosphorus compound is not particularly limited, but preferred examples include orthophosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, and tri-n-butyl phosphate.

  The polyester layer B in the present invention contains inert particles B in order to impart winding properties. The inert particles B may be one type or a combination of two or more types. The average particle diameter (dB) of the inert particles B is preferably in the range of 50 to 1000 nm, more preferably 100 to 800 nm, even more preferably 150 to 700 nm, and particularly preferably 200 to 600 nm. The content of the inert particles B is 0.001 to 1% by weight, more preferably 0.005 to 0.8% by weight, and still more preferably 0.01 to 0.6% by weight based on the weight of the polyester composition B. %, Particularly 0.01 to 0.3% by weight is preferred. As the inert particles B, those described for the inert particles A can be suitably used.

  By the way, the polyester layer B in the present invention preferably has a water contact angle of 70 degrees to 95 degrees. When the water contact angle is smaller than the above range, the effect of improving the film winding property and the blocking improving effect is poor. When the water contact angle is larger than the above range, the adhesiveness with the back coat layer and the like is lowered when the magnetic recording medium is formed. Sometimes.

  Such a water contact angle on the surface is, for example, 0.001 based on the weight of the composition of an ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol. It can be achieved by adding ˜1% by weight. Here, ester wax includes ester wax and partially saponified ester wax partially saponified. When the ratio of the wax in the polyester composition B is below the lower limit, the effect of improving the film winding property and the effect of improving blocking may be poor. On the other hand, when the ratio of the wax exceeds the above upper limit, a large amount of the wax component is transferred by bleed-out to the opposite surface that comes into contact with the film when it is wound up on a roll in the film production process. The base film may be displaced during drawing, and the base film may meander during vapor deposition. Furthermore, there may be a problem that the adhesion between the metal thin film formed by vapor deposition on the base film and the base film is hindered.

  The aliphatic monocarboxylic acid has 8 or more carbon atoms, preferably 8 to 34 carbon atoms. If the number of carbon atoms is less than 8, the resulting ester wax has insufficient heat resistance, and the ester wax is easily decomposed under heating conditions when dispersed in the polyester. .

  Examples of aliphatic monocarboxylic acids having 8 or more carbon atoms include pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, Examples thereof include pehenic acid, lignoceric acid, serotic acid, montanic acid, melissic acid, hentriacontanoic acid, petroceric acid, oleic acid, erucic acid, linoleic acid, and mixtures containing these.

  The alcohol component of the ester wax is a polyhydric alcohol having two or more hydroxyl groups. Furthermore, it is preferable that it is a polyhydric alcohol which has 3 or more of hydroxyl groups from a heat resistant viewpoint. When monoalcohol is used, the heat resistance of the produced ester wax is insufficient.

  Examples of the polyhydric alcohol having two hydroxyl groups include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,7-heptanediol. 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol and the like are preferable. Preferable examples of the polyhydric alcohol having 3 or more hydroxyl groups include glycerin, erythritol, trait, pentaerythlit, arabit, xylit, tarit, sorbit, mannitol and the like.

  Examples of the ester wax obtained from the aliphatic monocarboxylic acid and the polyhydric alcohol include monoesters, diesters, triesters and the like, depending on the number of hydroxyl groups of the polyhydric alcohol. Among these, from the viewpoint of heat resistance, a diester is preferable to a monoester, and a triester is preferable to a diester. Among these, particularly preferred ester waxes are sorbitan tristearate, pentaerythritol triphenate, glycerin tripalmitate, and polyoxyethylene distearate.

  The partially saponified ester wax composed of the aliphatic monocarboxylic acid and the polyhydric alcohol is obtained by partially esterifying the polyhydric alcohol with an aliphatic monocarboxylic acid having 8 or more carbon atoms, It is obtained by saponification. Specific examples include wax E, wax OP, wax O, wax OM, and wax FL (all trade names manufactured by Hoechst Co., Ltd.) obtained by saponifying montanic acid diol ester with calcium hydroxide. Such (partially saponified) ester wax may be used alone or in combination of two or more.

  The amount of the above (partially saponified) ester wax added to the polyester composition B is 0.001 to 1% by weight, further 0.003 to 0.5% by weight, and further 0% based on the weight of the composition. 0.005 to 0.5% by weight, particularly 0.01 to 0.3% by weight is preferable. When the amount of the (partially saponified) ester wax is less than the lower limit, the film winding property is not sufficiently improved, and the effect of improving blocking cannot be obtained. On the other hand, when the upper limit is exceeded, a large amount of the wax component is transferred by bleed-out to the opposite surface that comes into contact with the film when it is wound up on the roll in the film manufacturing process. This causes the negative effect of shifting and meandering during vapor deposition. Further, there is a problem that the adhesion between the metal thin film formed by vapor deposition on the base film and the base film is hindered.

  The biaxially oriented laminated polyester film of the present invention preferably has a center plane average roughness (hereinafter referred to as WRaA) of the surface on the polyester layer A side of 0.5 nm to 2.5 nm. When the surface roughness exceeds the upper limit, the electromagnetic conversion characteristics are likely to deteriorate, and when the surface roughness is less than the lower limit, the running property may be deteriorated. Further preferred WRaA is 0.7 nm or more and 2.2 nm or less, and particularly preferred WRaA is 0.8 nm or more and less than 1.7 nm.

  In the biaxially oriented laminated polyester film of the present invention, the center plane average roughness (WRaB) of the surface on the polyester layer B side is 2 nm or more and 20 nm or less, further 4.0 nm or more and 15 nm or less, and further 4.5 nm or more and 12 nm. In the following, it is particularly preferably in the range of 5.0 to 10 nm. When the WRaB exceeds the upper limit, the electromagnetic conversion characteristics and the like are likely to be reduced, while when the WRaB is less than the lower limit, due to the flatness, conveyance, scratching, winding, Handling properties such as unwinding may be deteriorated, and the shape (roll formation) when wound on a roll may be deteriorated, resulting in deterioration of productivity, reduction of product yield, and increase of manufacturing cost of the product. The WRaB is preferably coarser than the above-mentioned WRaA, more preferably 0.1 nm or more, and particularly preferably 0.5 nm or more.

  WRa depends on the polymerization catalyst and heat stabilizer used, the kind and particle size of the inert particles contained, the layer thickness ratio of polyester layer A and polyester layer B, the longitudinal stretching temperature and / or the transverse stretching temperature during film production. It can also be adjusted by the degree of particle protrusion and surface flattening.

  By the way, in order to adjust the above-mentioned WRaA and WRaB to a desired range, it is preferable that the average particle diameter of the inert particles B contained in the layer B and the thickness of the polyester layer A satisfy a specific relationship. . Specifically, when the inert particle B has one kind of inert particle, the average particle diameter is used. When the inert particle B is a combination of two or more kinds of inert particles, the inert particle is used. Among them, when the average particle diameter of the inert particles having the largest average particle diameter is dB (μm) and the thickness of the polyester layer A is tA (μm), dB / tA is 0.01 or more and 0.00. It is preferably 5 or less, more preferably 0.02 or more and 0.4 or less, and particularly preferably 0.03 or more and 0.1 or less.

  As for the thickness of the biaxially oriented laminated polyester film of the present invention, the thickness of the whole laminated film is preferably 3 μm or more and 8 μm or less. The thickness of the polyester layer A is 2.5 μm or more, preferably 3.5 μm or more, more preferably 4.0 μm or more. When the thickness of the polyester layer A is less than the lower limit, the effect of suppressing the precipitation of oligomers becomes poor, or the flatness of the surface on the polyester layer A side of the biaxially oriented laminated polyester film due to push-up by the inert particles B in the polyester layer B Will be damaged. Moreover, the thickness of the polyester layer B is 2.0 micrometers or less, Preferably it is 1.7 micrometers or less, More preferably, it is 1.5 micrometers or less. If the thickness of the polyester layer B exceeds the upper limit, the effect of suppressing the oligomer precipitation by the polyester layer A becomes poor, or the surface on the polyester layer A side of the biaxially oriented laminated polyester film is flattened by the inert particles B in the polyester layer B. Sexuality will be impaired. The lower limit of the thickness of the polyester layer B is preferably 0.5 μm or more, more preferably 0.8 μm or more, and particularly preferably 1.1 μm or more from the viewpoint of expressing the effect of improving the slit property at the time of tape processing by the polyester layer B. is there. From these points, it is preferable that the ratio of the thickness of the polyester layer A and the polyester layer B is in the range of 2.5 to 6, particularly 3 to 5. At this time, the layer thickness structure of the layer A forming the flat surface and the polyester layer B forming the running surface is not added to the polyester layer B so that the surface defects do not occur on the surface of the polyester layer A. It is preferable that the average particle diameter dB of the active particles and the thickness of the polyester layer A are configured to satisfy the above-described relationship. Further, regarding the relationship between the thickness of the polyester layer B and the inert particles B, it is preferable that the thickness of the polyester layer B is ½ times or more (μm) with respect to the average particle diameter dB.

  By the way, the biaxially oriented laminated polyester film of the present invention is a magnetic layer in the case of a magnetic tape, that is, adhesion improvement with a metal thin film and suppression of oligomer precipitation from the polyester layer A, etc. The coating layer C is preferably provided on the surface on the side where the magnetic layer is provided, that is, on the surface not in contact with the polyester layer B of the polyester layer A of the biaxially oriented laminated polyester film.

  The coating layer C is made of a binder resin C, inert particles C, a surfactant C, and a siloxane copolymer acrylic resin C.

  Examples of the binder resin C include water-soluble or water-dispersible resins such as polyester resins, acrylic resins, and polyurethane resins, and water-soluble or water-dispersible polyester resins are particularly preferable.

  Examples of the water-soluble or water-dispersible polyester resin include acid components such as isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and adipic acid. , Sebacic acid, dodecanedicarboxylic acid, succinic acid, sodium 5-sulfoisophthalate, potassium 2-sulfoterephthalate, trimellitic acid, trimesic acid, trimellitic acid monopotassium salt, p-hydroxybenzoic acid The glycol component is, for example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, p-xylylene glycol, dimethylol. Propane, bisphe Mainly comprising a polyester resin from one or more polyhydroxy compounds such as ethylene oxide adduct of Lumpur A is preferably used. Also, a graft polymer or block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or a specific physical configuration (IPN (interpenetrating polymer network) type, core-shell type, etc.) in the form of microscopic particles of two types of polymers It may be an acrylic-modified polyester resin formed. The water-soluble or water-dispersible herein means a type that is dissolved, emulsified and finely dispersed in water. In the present invention, a type that is emulsified and finely dispersed in water is preferred. Moreover, since these impart hydrophilicity, for example, a sulfonate group, a carboxylate group, or a polyether unit may be introduced into the molecule.

  The inert particles C are not particularly limited, but those having relatively low specific gravity that are difficult to settle in the coating liquid are preferable. For example, particles comprising organic particles such as crosslinked silicone resin, acrylic resin, polystyrene, melamine-formaldehyde resin, aromatic polyamide resin, polyamideimide resin, crosslinked polyester, wholly aromatic polyester, silicon dioxide (silica), calcium carbonate, etc. Preferably mentioned. Of these, crosslinked silicone resin particles, acrylic resin particles, silica particles, and core-shell type organic particles (core: crosslinked polystyrene, shell: polymethyl methacrylate particles, etc.) are particularly preferred.

  The average particle diameter (dC) of the inert particles C is 10 to 50 nm, preferably 12 to 45 nm, and more preferably 15 to 40 nm. If the average particle size is less than 10 nm, the slipperiness of the film may be poor. On the other hand, if it exceeds 50 nm, the electromagnetic conversion characteristics of the magnetic recording medium may be poor.

  As for the shape of the inert particles C, the volume shape factor (f) described later is preferably 0.1 to π / 6, more preferably 0.2 to π / 6, and particularly preferably 0.4 to π / 6. The shape of a particle having a volume shape factor (f) of π / 6 is a sphere (true sphere). That is, those having a volume shape factor (f) of 0.4 to π / 6 substantially include spheres, true spheres, and elliptical spheres such as rugby balls, and are preferable as the inert particles C. Particles having a volume shape factor (f) of less than 0.1, such as flaky particles, are not preferred because running durability is reduced.

  The content of the inert particles C is 0.5 to 30% by weight, preferably 2 to 20% by weight, more preferably 3 to 10% by weight with respect to the coating layer C (solid content of the coating liquid). If the content is less than 0.5% by weight, the slipperiness of the film may be poor. On the other hand, if it exceeds 30% by weight, the electromagnetic conversion characteristics of the magnetic recording medium may be poor. It is not preferable. The thickness of the coating layer C is usually 1 to 100 nm, preferably 2 to 50 nm, more preferably 3 to 10 nm, and particularly preferably 3 to 8 nm.

  The biaxially oriented laminated polyester film of the present invention can be produced according to a method conventionally known or accumulated in the art. The laminated structure of the polyester layer A and the polyester layer B is preferably produced by a coextrusion method. Furthermore, when laminating the coating layer C on the surface, the laminating method is preferably performed by a coating method.

  More specifically, the production method is exemplified by a polyester having an intrinsic viscosity in which inert particles B are finely dispersed and contained in the extrusion die or before the die (generally, the former is called a multi-manifold method and the latter is called a feed block method). A composition B (containing the (partially saponified) ester wax if necessary) and a polyester composition A having a high intrinsic viscosity subjected to solid-phase polymerization and containing inert particles A as necessary, respectively, Furthermore, after high-precision filtration, it is laminated and composited in a molten state to form a laminated structure having the above-mentioned preferred thickness ratio, and then coextruded into a film form at a temperature of melting point (Tm) to (Tm + 70) ° C. from the die. It is rapidly cooled and solidified with a cooling roll of ˜90 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film was stretched at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester) at a magnification of 2.5 to 5.0 times according to a conventional method. Preferably, the film is stretched at a magnification of 2.7 to 4.5 times, and then at a magnification of 3.0 to 7.0 times at a temperature of (Tg) to (Tg + 70) ° C. in a direction perpendicular to the stretching direction. The film is preferably stretched at a magnification of 3.5 to 5.5 times. Furthermore, you may extend | stretch again in the film forming direction and / or a horizontal direction as needed. That is, it is good to perform 2 steps | paragraphs, 3 steps | paragraphs, 4 steps | paragraphs, or multistage extending | stretching. The total draw ratio is usually 9 times or more, preferably 10 to 35 times, and more preferably 12 to 30 times.

  Moreover, it is preferable to implement heat setting in 3 zones or more. At this time, in the case of three zones, the temperature of the first zone is preferably set to a temperature intermediate between the transverse stretching temperature and the maximum heat setting temperature, and is preferably 160 to 200 ° C. The temperature of the second zone is 200 to 230 ° C, the third zone (last heat setting zone) is lower than the second zone, and the range is preferably 170 to 210 ° C. In the case of three or more zones, it is preferable to increase the temperature by providing a slope between the temperature of the first zone and the zone of the highest heat setting temperature. Moreover, it is preferable that the last heat setting zone is lower than the highest heat setting temperature, and the range is 170-210 degreeC.

  Further, in this last heat setting zone, the rail width is preferably reduced by 0.5 to 5% with respect to the film width, so that the ratio of the longitudinal heat yield to the transverse heat yield is in the range of 0.9 to 1.5. It becomes possible to set to. The heat setting time is preferably 1 to 60 seconds. Because the temperature of the cooling zone after the heat setting zone is set in the range of 80 to 130 ° C., it becomes easy to set the ratio of the longitudinal heat yield and the transverse heat yield in the range of 0.9 to 1.5. preferable.

  Moreover, since the film with few scars can be obtained by making the difference of each roll speed | rate and the actual speed of a film into 0 to 1.5% or less, it is preferable.

  The polyester composition A and the polyester composition B may contain an additive other than the inert particles, for example, a stabilizer, a coloring agent, a specific resistance adjusting agent for a molten polymer, and the like, if desired.

  The film layer C is preferably laminated on the polyester layer A in the present invention by a method of applying an aqueous coating liquid.

  The coating is preferably performed on the surface of the polyester layer A before the final stretching treatment, and after coating, the film is preferably stretched at least in a uniaxial direction. The film is dried before or during the stretching. Among them, the coating is preferably performed on an unstretched laminated film or a longitudinal (uniaxial) stretched laminated film, particularly a longitudinal (uniaxial) stretched laminated film. Although it does not specifically limit as a coating method, For example, a roll coat method, a die coat method, etc. are mentioned.

  The solid concentration of the coating liquid, particularly the aqueous coating liquid, is preferably 0.2 to 8% by weight, more preferably 0.3 to 6% by weight, and particularly preferably 0.5 to 4% by weight. In addition, other components such as other surfactants, stabilizers, dispersants, ultraviolet absorbers, thickeners and the like can be added to the aqueous coating liquid as long as the effects of the present invention are not hindered.

  Further, the crystallinity of the polyester layer A and the polyester layer B is desirably 30 to 50% when the polyester is polyethylene terephthalate and 28 to 38% when the polyester is polyethylene-2,6-naphthalate. If both are below the lower limit, the thermal shrinkage rate is increased, while if the upper limit is exceeded, the abrasion resistance of the film is deteriorated, and white powder is liable to be produced when sliding with the roll or guide pin surface.

  According to the present invention, a laminated polyester film in which a polyester layer B is laminated on one side of a polyester layer A, and a laminated polyester film in which a film layer C is laminated on a surface of the polyester layer A that is not in contact with the polyester layer B. Magnetic recording media each having a base film are also provided.

  An embodiment for producing a magnetic recording medium from the laminated polyester film of the present invention is as follows.

  The laminated polyester film of the present invention is mainly composed of iron, cobalt, chromium or the like on the surface of the polyester layer A, preferably the coating layer C, that is, the surface on the flat surface side, by a method such as vacuum deposition, sputtering, or ion plating. A ferromagnetic metal thin film layer made of an alloy or oxide as a component is formed, and a protective layer such as diamond-like carbon (DLC) or a fluorine carboxylic acid-based lubricating layer is formed on the surface as required for the purpose or application. Providing sequentially, and further providing a known backcoat layer on the surface of the layer B side, it has excellent electromagnetic conversion characteristics such as output in the short wavelength region, S / N, C / N, etc., and high dropout and low error rate It can be set as the vapor deposition type magnetic recording medium for density recording. This vapor deposition type magnetic recording medium is extremely useful as an analog signal recording Hi8, digital signal recording digital video cassette recorder (DVC), data 8 mm, mammoth, and AIT tape medium.

  In addition, the laminated polyester film of the present invention is made of iron chloride or acicular fine magnetic powder mainly composed of iron on the surface on the polyester layer A side, that is, on the flat surface side surface, such as vinyl chloride, vinyl chloride / vinyl acetate copolymer, etc. In particular, the coating layer is uniformly dispersed in the binder, the thickness of the magnetic layer is 1 μm or less, preferably 0.1 to 1 μm, and a backcoat layer is provided on the surface on the layer B side by a known method. It is also possible to provide a metal-coated magnetic recording medium for high-density recording with excellent output characteristics in a region, electromagnetic conversion characteristics such as S / N and C / N, and low dropout and error rate. Further, if necessary, a nonmagnetic layer containing fine titanium oxide particles or the like as an underlayer of the metal powder-containing magnetic layer is dispersed and coated in the same organic binder as the magnetic layer on the surface on the layer A side. You can also. This metal-coated magnetic recording medium is a tape medium for analog signal recording 8 mm video, Hi8, β cam SP, W-VHS, data 8 mm, DDS4, digital β cam, D2, D3, SX, LTO, DLT, etc. As extremely useful.

Hereinafter, the present invention will be specifically described by way of examples. Each characteristic in the present invention is measured or evaluated by the following method. In the examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
(1) Average particle diameter of inert particles A and B Measurement is performed using a CP-50 type centrifuggle particle size analyzer (Centrifugal Particle Size Analyzer) manufactured by Shimadzu Corporation. The particle size “equivalent sphere diameter” corresponding to 50 mass percent is read from the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is used as the average particle size. (See Book “Particle Size Measurement Technology” published by Nikkan Kogyo Shimbun, 1975, pages 242-247).

(2) Average particle size of inert particles C Light scattering method, that is, Nicomp Instruments Inc. It is indicated by the “equivalent sphere diameter” of the particles at a point of 50% by weight of the total particles determined by NICOMMP MODEL 270 SUBMICRON PARTICIZER manufactured by the company.

(3) Layer thickness The total thickness of the film is measured randomly at 10 points with a micrometer, and the average value is used. The layer thickness is obtained by measuring the layer thickness on the thin side by the method described below, and subtracting the layer thickness on the thick side from the layer thickness on the side thinner than the total thickness. That is, using a secondary ion mass spectrometer (SIMS), the concentration ratio of the element due to the highest concentration of particles in the film having a depth of 5000 nm from the surface layer to the carbon element of the polyester (M ⁺ / C ⁺ ) is the particle concentration, and analysis in the thickness direction is performed from the surface to a depth of 5000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, the particle concentration may once increase to a stable value 1 and then increase or decrease to reach a stable value 2, or may decrease monotonously. Based on this distribution curve, in the former case, the depth gives a particle concentration of (stable value 1 + stable value 2) / 2, and in the latter case, the depth at which the particle concentration is ½ of the stable value 1. (This depth is deeper than the depth that gives a stable value of 1), which is the layer thickness of the layer.
The measurement conditions are as follows.
1) Measuring device secondary ion mass spectrometer (SIMS): 6300 manufactured by PERKIN ELMER
2) Measurement conditions Primary ion species: O ₂ ⁺
Primary ion acceleration voltage: 12 kV
Primary ion current: 200 nA
Raster area: 400 μm
Analysis area: 30% gate
Measurement vacuum: 6.0 × 10 ⁻⁹ Torr
E-GUNN: 0.5kV-3.0A

  In the case where the most contained particles in the range of 5000 nm from the surface layer are organic polymer particles other than silicone resin, it is difficult to measure with SIMS, so FT-IR (Fourier transform infrared spectroscopy) while etching from the surface, Depending on the particle, a concentration distribution curve similar to the above is measured by XPS (X-ray high electron spectroscopy) or the like to determine the layer thickness.

(4) Center plane average roughness (WRa)
Using a non-contact type three-dimensional surface roughness meter (manufactured by WYKO: NT-2000), the measurement magnification was 25 times, and the measurement area was 246.6 μm × 187.5 μm (= 0.0462 mm ² ). The center plane average roughness WRa is obtained from the following formula using surface analysis software built in the roughness meter.

ここで、上記式中のＺｊｋは測定方法（２４６．６μｍ）、それと直行する方法（１８７．５μｍ）をそれぞれｍ分割、ｎ分割したときの各方向のｊ番目、ｋ番目の位置における２次元粗さチャート上の高さである。

Here, Zjk in the above equation is a two-dimensional coarse at the j-th and k-th positions in each direction when the measurement method (246.6 μm) and the direct method (187.5 μm) are divided into m and n, respectively. It is the height on the chart.

(5) Intrinsic viscosity Determined from a value measured at 35 ° C. in an o-chlorophenol solvent.

(6) Manufacture of magnetic tape
A cobalt-oxygen thin film having a thickness of 110 nm is formed on the surface of the obtained biaxially oriented laminated polyester film on the polyester layer A side by vacuum deposition. Next, diamond-like carbon was formed with a thickness of 10 nm on the cobalt-oxygen thin film layer by sputtering, and wound up by 15000 m. Further, a fluorine-containing carboxylic acid-based lubricant is sequentially provided. Subsequently, a back coat layer made of carbon black, polyurethane and silicone is provided on the surface opposite to the surface on which the cobalt-oxygen thin film is formed so as to have a thickness of 500 nm, and slitted to a width of 8 mm and 6.35 mm by a slitter. Then, it was wound up on a commercially available reel to produce a magnetic tape.

(7) Slit properties When manufacturing a magnetic tape in (5) above, the cut ends when slitting with a slitter, that is, both ends of the tape are observed with an optical microscope at a magnification of 975 times, and evaluated according to the following criteria: did.
○: No swell in the cross section and no slit dust is observed △: Swell in the cross section and a small amount of powdery or elongated slit waste is observed ×: There is a swell in the cross section and powdered or elongated slit dust is present Fairly clearly

(8) Electromagnetic conversion characteristics (C / N)
The C / N measurement was performed on the 6.35 mm tape created in (5) above using a commercially available Hi8 VTR (manufactured by Sony Corporation, EV-BS3000) under the condition of 7 MHz ± 1 MHz. Compare this C / N with a commercially available video tape for Hi8 (manufactured by Sony Corporation, vapor deposition type tape E6-120HME4), a tape of +3 dB or more is ◎, a tape of +1 to +3 dB is ◯, less than +1 dB to -1. Evaluation was made with a 0 db tape as Δ and a tape with less than -1.0 db as x.

(9) Dropout (DO)
Using a dropout counter manufactured by Shiba-Soku Co., Ltd., a dropout of 3 μsec / 10 dB or more is measured for 10 minutes, converted into the number per minute, and determined according to the following criteria.
◎: Dropout less than 3 / min. ○: Dropout more than 3 / min., Less than 6 / min. ×: Dropout more than 6 / min.

(10) Amount of oligomer Layer A side (the surface of the film layer C when the film layer C is present): Observation of 10 layers of the layer A side of the film heat-treated at 105 ° C. for 3 hours with an optical microscope at a magnification of 975 times. The number of oligomers having a size of 0.5 μm or more is counted and determined according to the following criteria.
◎: 200 pieces / mm ² or less ○: 200 pieces / mm ² to more than 400 pieces / mm ² or less △: 400 pieces / mm ² to more than 800 pieces / mm ² less than ×: 800 pieces / mm ² or more

Layer B side: 10 fields of view of the layer B side of the film heat-treated at 150 ° C. for 30 minutes are observed with an optical microscope at a magnification of 975 times. The number of oligomers having a size of 0.5 μm or more is counted and determined according to the following criteria.
◎: 400 pieces / mm ² or less ○: 400 pieces / mm ² to more than 800 pieces / mm ² or less △: 800 pieces / mm ² to more than 1200 / mm ² less than ×: 1200 pieces / mm ² or more

[Example 1]
<Creation of resin A1>
100 parts of terephthalic acid, 70 parts of ethylene glycol, and germanium oxide catalyst were added at 0.006 part, and a polymerization reaction was carried out by a direct weight method according to a conventional method. At the end of the reaction, 0.01 part of phosphorous acid was added as a stabilizer to obtain a prepolymer having an intrinsic viscosity of 0.55. Subsequently, this polymer was subjected to solid phase polymerization at 230 ° C. under a high vacuum of 0.5 mmHg for 10 hours to obtain a resin A1. The intrinsic viscosity of Resin A1 was 0.86.

<Creation of resin B1>
To a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol, 0.025 part of manganese acetate tetrahydrate was added as a transesterification catalyst, and the ester exchange reaction was carried out while gradually raising the internal temperature from 150 ° C. When the transesterification reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and after sufficient stirring, 0.03 part of antimony trioxide was added. After sufficiently distilling water mixed in the system, silicone particles having an average particle diameter of 300 nm and θ-type alumina having an average particle diameter of 70 nm become the contents shown in Table 1 as the inert particles B as a lubricant. Then, the reaction product was transferred to a polymerization reactor and subjected to polycondensation under high temperature vacuum (final internal temperature 295 ° C.) to obtain a polyethylene terephthalate composition having an intrinsic viscosity of 0.65. . Table 1 shows powders of sorbitan tristearate (melting point 55 ° C.) as an ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol (partially saponified) to this polyethylene terephthalate composition. It knead | mixed with the biaxial rudder with a vent so that it might become content, and the polyethylene terephthalate composition (resin B1) for the polyester layer B of the intrinsic viscosity 0.62 was obtained. The amount of antimony element that is a catalyst residue in the resin B1 was 250 ppm.

<Creation of resin B2>
To a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol, 0.018 parts of calcium acetate monohydrate and 0.060 parts of magnesium acetate tetrahydrate are added as a transesterification catalyst, and the internal temperature is increased from 150 ° C. The transesterification was carried out while gradually increasing. When the transesterification reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and after sufficient stirring, 0.8 part of trimellitic anhydride and tetrabutyl in 2.5 parts of ethylene glycol After adding 0.014 part of a solution obtained by reacting 0.65 parts of titanate (the proportion of titanium element in the liquid is 11% by weight) and stirring sufficiently, the reaction product is then transferred to a polymerization reactor and subjected to high temperature vacuum. Polycondensation was carried out at a final internal temperature of 295 ° C. to obtain a polyethylene terephthalate composition (resin B2) for polyester B having an intrinsic viscosity of 0.60. The amount of titanium element which is a catalyst residue in the resin B2 was 10 ppm.

<Creation of biaxially oriented laminated polyester film>
The obtained resin A1 was dried at 170 ° C. for 4 hours until the water content of the polymer became 0.1% by weight. Further, a mixture B of resin B1 and resin B2 having a weight ratio of 50:50 was dried at 170 ° C. for 5 hours until the moisture content of the polymer became 0.05% by weight. Then, the dried resin A1 and the mixture B are supplied to two extruders, melted at a melting temperature of 280 to 300 ° C., and subjected to high-precision filtration with a steel wire filter having an average opening of 11 μm, and then a multi-manifold type Using a coextrusion die, polyester layer B made of mixture B was laminated on one side of polyester layer A made of resin A1, and rapidly cooled to obtain an unstretched laminated polyester film having a thickness of 93 μm.

  The obtained unstretched film was preheated, further stretched 3.4 times at a film temperature of 100 ° C. between low speed and high speed rolls, and rapidly cooled to obtain a longitudinally stretched film. Next, an aqueous coating liquid (total solid content concentration: 1.0%) having the following composition (in terms of solid content) is applied to the A layer side of the longitudinally stretched film so that the thickness of the coating layer C obtained after drying becomes 8 nm. It applied by the kiss coat method.

<Solid composition of coating liquid>
Binder: Acrylic modified polyester (Takamatsu Yushi Co., Ltd., IN-170-6) 60%
Inactive particles C: Acrylic filler (average particle size 20 nm, volume shape factor 0.40, manufactured by Nippon Shokubai Co., Ltd., poster) 10%
Surfactant: (Sanyo Kasei, Nara Acty N85) 15%

  Then, it supplied to the stenter and extended | stretched 4.3 times in the horizontal direction at 110 degreeC. The obtained biaxially stretched film was heat-fixed with hot air of 200 ° C., 230 ° C., and 180 ° C. for 4 seconds in each of the three heat setting zones, and subjected to a 1.5% relaxation treatment in the width direction in the third zone. Furthermore, the temperature of the cooling zone was set to 100 ° C., and a biaxially oriented laminated polyester film having a total thickness of 6.4 μm, a polyester layer A thickness of 5.1 μm, and a polyester layer B thickness of 1.3 μm was obtained. In addition, about the thickness of the polyester layers A and B, it adjusted with the discharge amount of two extruders. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Example 2]
For the resin A1, the drying is changed to 3 hours to make the water content of the polymer 0.2% by weight. For the resin B1, the inert particles B and the ratio in the polyester layer B are as shown in Table 1. For the mixture B, the same operation as in Example 1 was repeated except that the ratio of the resin B1 and the resin B2 was changed to 25% by weight and 75% by weight. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Example 3]
The same operation as in Example 1 was repeated except that the ratio between the resin B1 and the resin B2 was changed to 75% by weight and 25% by weight. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Example 4]
The same operation as in Example 1 was repeated except that the addition amount of the inert particles C in the coating film C was 15% by weight. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Example 5]
The same operation as in Example 1 was repeated except that the average particle diameter of the inert particles C was 30 nm and the addition amount was 5 wt%. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Example 6]
Except for changing the inert particles B in the polyester layer B to silicone particles having an average particle diameter of 500 nm and θ-type alumina having an average particle diameter of 70 nm, and changing the content of each polyester layer B as shown in Table 1. The same operation as in Example 1 was repeated. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Comparative Example 1]
The same operation as in Example 1 was repeated except that the resin B2 was used instead of the resin A1. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Comparative Example 2]
Addition of silicone particles having an average particle size of 300 nm and θ-type alumina having an average particle size of 70 nm as a lubricant (inert particles B) to the resin A1 to be 0.12 wt% and 0.2 wt% in the resin, respectively. Then, a powder of sorbitan tristearate (melting point 55 ° C.) was kneaded into the resin so as to be 0.2% by weight to obtain a resin B3. Then, the same operation as in Example 1 was repeated except that the resin B3 was used instead of the mixture B. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Comparative Example 3]
Resin B2 was solid-phase polymerized according to a conventional method to obtain polymer B4 having an intrinsic viscosity of 0.8. A laminated film was obtained in the same manner as in Example 1 except that resin B4 was used instead of resin A1 used for layer A. Table 1 shows the characteristics of this laminated film, and the slit characteristics of the tape after the ferromagnetic thin film and diamond-like carbon were applied using this film, and the characteristics of the ferromagnetic thin film deposition type magnetic tape.

[Comparative Example 4]
To the resin B2, as inert particles B as a lubricant, silicone particles having an average particle size of 300 nm and θ-type alumina having an average particle size of 70 nm are added in an amount of 0.12% by weight and 0.20% by weight, respectively, and sorbitan Tristearate (melting point: 55 ° C.) powder was kneaded into the resin so as to be 0.2% by weight to obtain a resin B5. Then, the same operation as in Example 1 was repeated except that the resin B5 was used instead of the mixture B. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

[Comparative Example 5]
Resin B6 was obtained by changing the contents of inert particles B (silicone particles and θ-type alumina) and ester wax in resin B1 to 0.12% by weight, 0.20% by weight, and 0.20% by weight, respectively. It was. And the same operation as Example 1 was repeated except having used resin B6 instead of mixture B. Table 1 shows the characteristics of the obtained biaxially oriented laminated polyester film, and the characteristics of a ferromagnetic thin film vapor deposition type magnetic tape to which a ferromagnetic metal thin film and diamond-like carbon were applied using this film as a support.

  In Table 1, STS is sorbitan tristearate, C / N is electromagnetic conversion characteristics, D.I. O. Means dropout.

  As is clear from Table 1, the biaxially oriented polyester film of the present invention uses a germanium catalyst on the surface layer part A side and has an intrinsic viscosity in a certain range, and the surface layer part B contains an antimony catalyst and a titanium catalyst in a certain range. When the amount is used and the difference in intrinsic viscosity between the surface layer parts A and B is in a certain range, the slit property of the tape is good and the generation of oligomers is small. Therefore, it is possible to provide a film and tape with high tape performance. On the other hand, those not satisfying the requirements of the present invention cannot satisfy these characteristics at the same time.

Claims (8)

A biaxially oriented laminated polyester film in which a polyester layer B having a thickness of 2 μm or less is laminated on one side of a polyester layer A having a thickness of 2.5 μm or more,
The polyester layer A is composed of a polyester composition A having an intrinsic viscosity of 0.62 or more, in which the polycondensation reaction catalyst is a germanium compound,
In the polyester layer B, the polycondensation reaction catalyst is a titanium compound and an antimony compound, the content of the titanium compound is 1 to 15 ppm in terms of the amount of titanium element, and the content of the antimony compound is 40 to 160 ppm in terms of the amount of antimony element The polyester composition B containing a phosphorus compound having an phosphorus element content of 10 to 200 ppm and an intrinsic viscosity of 0.59 or less, and the polyester composition B has an average particle size of 50 to 1000 nm based on the weight of the composition A biaxially oriented laminated polyester film comprising 0.001 to 1% by weight of the inert particles B and having a difference in intrinsic viscosity of 0.10 at most with the polyester composition A.   2. A coating layer C made of a binder resin C, inert particles C, a surfactant C, and a siloxane copolymer acrylic resin C is laminated on the surface of the polyester layer A that is not in contact with the polyester layer B. Biaxially oriented laminated polyester film.   The polyester composition B contains 0.001 to 10% by weight of an ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol, based on the weight of the composition. Biaxially oriented laminated polyester film.   The biaxially oriented laminated polyester film according to claim 1, wherein the surface on the polyester layer A side has a center line average roughness WRaA in the range of 0.5 to 2.5 nm.   The biaxially oriented laminated polyester film according to claim 1, wherein the surface on the polyester layer B side has a center line average roughness WRaB in the range of 2 to 20 nm.   The biaxially oriented laminated polyester film according to claim 1, wherein the polyester composition A or the polyester composition B is a polyester composition comprising polyethylene terephthalate.   The biaxially oriented laminated polyester film according to any one of claims 1 to 6, which is used as a support for a vapor deposition type magnetic recording medium.   A magnetic recording medium comprising the biaxially oriented laminated polyester film according to claim 1 and a metal thin film provided on the surface of the polyester layer A side.