JP4624932B2 - Biaxially oriented laminated polyester film - Google Patents

Description

  The present invention relates to a biaxially oriented laminated polyester film. More specifically, it can be used in applications where excellent flatness and adhesiveness are required for a base film such as a ferromagnetic metal thin film magnetic recording tape, and also recovers edge scraps and the like produced in the film manufacturing process. As a biaxially oriented laminated polyester film excellent in cost merit that can be recovered as it is, that is, self-circulating.

  A biaxially oriented polyester film represented by a polyethylene terephthalate film is widely used because of its excellent physical and chemical properties, particularly as a base film of a magnetic recording medium.

  In recent years, in magnetic recording media, higher density and higher capacity have been promoted, and accordingly, flatness of the base film and thinning of the thickness have been demanded. When rolling up, the surface of the film roll becomes uneven and the surface of the film roll becomes uneven, reducing the yield of the product, and the appropriate range of tension, contact pressure, and speed when winding up is narrowed, so it is very easy to wind up In order to solve the problem that it becomes difficult, improvement of winding property is also desired. And, as a means to achieve the contradictory properties of improving the winding property and improving the electromagnetic conversion characteristics, by using a laminated film, the surface on which the magnetic layer is applied is flattened to improve the electromagnetic conversion characteristics. Means for improving the slipperiness by roughening the surface are widely known. Specifically, on the surface of the laminated polyester film on the side where the magnetic layer side is formed (hereinafter referred to as a flat layer), a lubricant having a small particle size is used, or the amount added is reduced, and the other magnetic layer is used. A lubricant having a large particle size is used on the surface on which the surface is not formed (hereinafter referred to as a running surface), and the amount added is increased.

  Therefore, the characteristics of the lubricant used, for example, the lubricant type, particle size, addition amount, etc. are greatly different between the flat surface and the running surface, and when trying to use the recovered chip of the laminated film itself, the lubricant composition is rough. Also, since it differs from the lubricant composition of the flat layer, when it is re-introduced in the production of the laminated film, the lubricant composition of the re-introduced layer is changed and the film characteristics are hindered.

  Therefore, in Japanese Patent Application Laid-Open No. 11-34262 (Patent Document 1), it is also possible to dilute the concentration of inert particles in the self-recovered polymer and use it on a flat surface. In literature 2), it is proposed that the concentration of inert particles in the self-recovering polymer is increased and used on the running surface side.

  However, in recent years, the demand for higher density has become stricter, and laminated films having self-recoverability and high flatness required in the field of base films such as metal thin-film magnetic recording media have been developed. The fact is that it was not provided. Moreover, in a base film such as a metal thin film type magnetic recording medium, a coating layer is often formed on the surface of the base film as an easy adhesion layer in order to improve the adhesion between the metal thin film layer, which is a magnetic layer, and the base film. However, when this film layer is contained in the self-recovering polymer, there is a problem that the film becomes a foreign substance in the film layer using the self-recovering polymer and the flatness is impaired.

JP-A-11-34262 JP 2000-246857 A

  The object of the present invention can be used in applications where excellent flatness and adhesiveness are required for a base film such as a ferromagnetic metal thin film magnetic recording tape, and also recovers edge debris generated in the film manufacturing process. Another object of the present invention is to provide a biaxially oriented laminated polyester film that can be reused as a raw material, that is, can be self-circulated and recovered and has excellent cost merit.

  As a result of earnest research to achieve such an object, the present inventor has found that in a laminated film having a rough surface layer and a flat layer, the thickness of the rough surface layer is larger than that of the flat layer, and the thickness and roughness of the rough surface layer are also increased. The ratio of the average particle size of the lubricant contained in the face layer is in a specific range, and the flat layer does not substantially contain inert particles, but contains inert particles with a very small average particle size on the surface. When providing a thin film layer with a thickness of about 10 nm, the flatness and the easy adhesion required as a base film for high-density magnetic recording media are provided even if the recovered polymer is self-circulated in the production of its own film. The present inventors have found that a base film can be obtained, and have reached the present invention.

Thus, according to the present invention, the film layer A, the film layer B laminated on one surface of the film layer A, and the film layer C laminated on the other surface of the film layer A, the film layer A is Inactive particles are not included, the thickness is in the range of 0.5 to 5 μm, the film layer B is thicker than the film layer A and 9.5 μm or less, and the thickness of the film layer B ( tB) containing inert particles B having an average particle diameter of 0.01 to 0.1 times, and the coating layer C is composed of inert particles C having an average particle diameter of 5 to 50 nm and a binder resin. The thickness is in the range of 1-20 nm , and
The film layer B contains the inert particles C contained in the coating layer C, and the self-recovering polymer produced in the process of producing the biaxially oriented laminated polyester film is used for a part of the polyester constituting the film layer B. A biaxially oriented laminated polyester film used for a base film of a magnetic recording tape in which the magnetic layer is a ferromagnetic metal thin film layer is provided.

  INDUSTRIAL APPLICABILITY According to the present invention, it can be used in applications where excellent flatness and adhesiveness are required for a base film such as a ferromagnetic metal thin film magnetic recording tape, and edge scraps generated in the film manufacturing process are recovered. Thus, a biaxially oriented laminated polyester film that is reused as a raw material as it is, that is, excellent in cost merit that can be self-circulated is provided.

  In the laminated biaxially oriented laminated polyester film of the present invention, a film layer B is laminated on one surface of the film layer A, and a coating layer C is laminated on the other surface. In the case of a single-layer film having only the film layer A or a three-layer film in which the film layer B is laminated on both surfaces of the film layer A, the effects of the present invention are hardly exhibited.

  In the present invention, the film layer A needs to contain no inert particles. The term “not containing inert particles” as used herein means that inert particles are not actively added or catalyst residues are not precipitated in order to form protrusions on the surface. Specifically, the content of inert particles having a particle size of 100 nm or more is 0.03 wt% or less, preferably 0.01 wt% or less, particularly preferably 0.005 wt% or less, based on the weight of the film layer A. It means that. If the inert particles are present in the film layer A, it is difficult to sufficiently reduce the influence when the self-recovering polymer is used for the film layer B, and the flatness of the surface of the coating layer C is impaired. Moreover, the thickness of the film layer A needs to be in the range of 0.5 to 5.0 μm, preferably 1.0 to 4.0 μm, and more preferably 1.5 to 3.5 μm. When the thickness of the film layer A is within the above range, the influence when the self-recovery polymer is used for the film layer B can be sufficiently relaxed, and the flatness of the surface of the coating layer C can be highly maintained. In addition, as a usage method of a self-recovery polymer, the method shown in FIG. 2 is mentioned. FIG. 2 is a schematic diagram of the self-circulation system. In FIG. 2, reference numerals 21 to 27 respectively denote 21 an unused polymer I, 22 an unused polymer II, 23 a recovered polymer, 24 a layer A, and 25 a B The layer 26 is a commercialized laminated film, and 27 is a collected laminated film. First, the laminated film is formed by laminating and polymerizing the unused polymer I and the unused polymer II, respectively, to form a laminated film. At this time, a portion having no problem becomes a productized laminated film 26, but a portion such as an edge that cannot be used as a product (collected laminated film 27) is inevitably generated. The recovered laminated film 27 is again subjected to melt extrusion as the recovered polymer 23.

In the present invention, the film layer B needs to be thicker than the film layer A and not more than 9.5 μm, preferably 1 to 8 μm, more preferably 2 to 6 μm. When the thickness of the film layer B is in the above range, a self-recovering polymer can be used for the film layer B at a practical level, but the capacity required as a base film for a high-density magnetic recording tape can be secured. The average particle size is 0.01 to 0.1 times, preferably 0.02 to 0.09 times, more preferably 0.03 to 0.08, relative to the thickness (t _B ) of the film layer B. It is necessary to contain twice as many inert particles B. When the average particle size of the inert particles is within the above range, the resulting biaxially oriented laminated polyester film can be provided with handling properties such as flatness, winding property and running property, and further, a self-recovering polymer can be used. When used for the film layer B, for example, the deterioration of flatness due to the inert particles C and the binder resin contained in the coating layer can be alleviated.

  In the present invention, the coating layer C is composed of inert particles C having an average particle size of 5 to 50 nm and a binder resin. When the coating layer C is composed only of a binder resin or inert particles having an average particle size less than the above lower limit and a binder resin, the obtained biaxially oriented laminated polyester film is used as a base film for a metal thin film type magnetic recording medium or the like. When used, the metal thin film layer, which is a magnetic layer, cannot have runnability. On the other hand, when the average particle size exceeds the above upper limit, when the self-recovery polymer is used for the film layer B, the inert particles C form large coarse protrusions and the flatness is impaired. A preferable average particle diameter of the inert particles C is in the range of 7 to 40 nm, more preferably 10 to 30 nm. The thickness of the coating layer C needs to be in the range of 1 to 20 nm, preferably 2 to 15 nm, more preferably 3 to 10 nm. When the thickness of the coating layer is less than the lower limit, the inert particles C are likely to fall off from the coating layer C. On the other hand, when the thickness of the coating layer exceeds the upper limit, when the self-recovering polymer is used for the film layer B, large coarse protrusions are formed by the coating layer C, and the flatness is impaired.

  Thus, in the biaxially oriented laminated polyester film of the present invention, in the laminated film having a rough surface layer and a flat layer, the thickness of the rough surface layer is larger than that of the flat layer, and the thickness of the rough surface layer and the rough surface layer are as follows. The ratio of the lubricant to the average particle size of the lubricant is in a specific range, and the flat layer is substantially free of inert particles, and the surface contains thin particles containing inert particles with a very small average particle size. When a coating layer having a thickness of 20 nm is provided, even if the recovered polymer is self-circulated in the production of its own film, it can be provided with flatness and easy adhesion required as a base film for a high-density magnetic recording medium. It was made.

Furthermore, the preferable aspect of this invention is explained in full detail below.
In the present invention, the polyesters constituting the film layer A and the film layer B are preferably the same in view of using a self-recovery polymer for the film layer B. Examples of the polyester in the present invention include aromatic polyesters having an aromatic dicarboxylic acid as the main acid component and an aliphatic glycol as the main glycol component, and are substantially linear and have film-forming properties, particularly by melt molding. It is necessary to have film formability. Specific aromatic dicarboxylic acids include, for example, terephthalic acid, naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracene dicarboxylic acid, etc. Can be mentioned. Examples of the aliphatic glycol include alicyclic groups such as polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, and cyclohexanedimethanol. A diol etc. can be mentioned. Among these, those having alkylene terephthalate or alkylene naphthalate as the main constituent are preferable, and polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferable. Of course, for example, a copolymerization component known per se may be copolymerized within a range not impairing the object of the present invention.

In the present invention, the polyester constituting the film layer A and the film layer B is at least one of a sulfonic acid quaternary phosphonium salt compound, 0.02 to 45 mmol% based on the repeating unit of the polyester, It is preferable to contain 1-20 mmol%. When the content is less than the lower limit, the effect of increasing the casting speed is small, the adhesion to the casting drum is lowered, and the flatness tends to be impaired. On the other hand, if the content exceeds the upper limit, the discharge function of the discharge electrode when the film is electrostatically adhered may deteriorate over time. From these viewpoints, the polyester constituting the film layer A and the film layer B has an AC volume resistivity of 1 × 10 ⁶ Ω · cm to 9 × 10 ⁸ Ω · cm, and further 3 × 10 ⁶ Ω · cm. It is preferably in the range of ˜5 × 10 ⁸ Ω · cm. When the AC volume resistivity exceeds the upper limit, the effect of increasing the casting speed is small. On the other hand, when the AC volume resistivity is less than the lower limit, the film may break down during electrostatic adhesion in the casting process. FIG. 1 shows an apparatus for measuring AC volume resistivity. In FIG. 1, reference numerals 1 to 11 denote a polymer to be measured, 2 is a lower electrode, 3 is an upper electrode, and 4 is a charging device. 5 is a temperature detection end, 6 is an ammeter, 7 is a reading thermometer, 8 is a power source, 9 is a standard resistance, 10 is an electron meter, and 11 is a heat insulation box. AC volume resistivity can be measured.

  The AC volume resistivity of such a molten film can be adjusted by including the sulfonic acid quaternary phosphonium salt described above. Specific examples of the sulfonic acid quaternary phosphonium salt include compounds represented by the following formulae.

ここで、上記式中の、Ａは芳香族基又は脂肪族基、Ｘ₁ 及びＸ₂ はそれぞれ同一若しくは異なるエステル形成性官能基又は水素原子、Ｒ₁ 、Ｒ₂ 、Ｒ₃ 及びＲ₄ はそれぞれアルキル基及びアリール基よりなる群から選ばれた同一又は異なる基、ｎは正の整数である。

In the above formula, A is an aromatic group or aliphatic group, X ₁ and X ₂ are the same or different ester-forming functional groups or hydrogen atoms, R ₁ , R ₂ , R ₃ and R ₄ are each The same or different group selected from the group consisting of an alkyl group and an aryl group, n is a positive integer.

  Preferred examples of the sulfonic acid quaternary phosphonium salt include 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid tetraphenylphosphonium salt, 3,5-dicarbomethoxybenzene. Tetrabutylphosphonium sulfonate, tetraphenylphosphonium 3,5-dicarbomethoxybenzenesulfonate, tetrabutylphosphonium 3, carboxybenzenesulfonate, tetrabutyl 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate Phosphonium salt, 4-hydroxyethoxybenzenesulfonic acid tetrabutylphosphonium salt, bisphenol A-3,3'-di (sulfonic acid tetrabutylphosphonium salt), 2,6-dicarboxynaphthalene-4-sulfur It can be mentioned phosphate tetrabutylphosphonium like, which only may be used in combination also two or more used alone type.

In the present invention, the polyesters of the film layer A and the film layer B are preferably those using a titanium compound as a catalyst in order to improve the surface flatness. From this point of view, the polyester of the film layer A is based on the number of moles of the acid component of the polyester of the film layer A, and the amount of titanium element (Ti _A ) is in the range of 2 to 15 mmol%, and further 4 to 12 mmol%. preferable. When the ratio of the titanium compound is in the above range, coarse protrusions based on catalyst residues and deteriorated foreign matters due to thermal deterioration during melting can be suppressed, and higher flatness can be exhibited.

Further, the polyester of the film layer B has a titanium element amount (Ti _B ) of 0.2 to 0.8, more preferably 0 with respect to Ti _A , based on the number of moles of repeating units of the polyester of the film layer B. Preferably it is in the range of 3 to 0.7. By making Ti _B / Ti _A within the above range, even if a self-recovering polymer is used for the film layer B, the thermal degradation of the polymer due to the titanium catalyst, and further the generation of foreign substances consisting of the degradation product can be suppressed, and an excellent flatness Sex can be imparted.

In the biaxially oriented laminated polyester film of the present invention, the film layer A and the film layer B preferably contain a phosphorus compound as a stabilizer. The content of the phosphorus compound contained in the film layer A is based on the number of moles of the repeating unit of the polyester of the film layer A, and the phosphorus element amount (P _A , mmol%) of the phosphorus compound and the above-described titanium element amount. The ratio of (Ti _A ) (P _A / Ti _A ) is in the range of 0.1 to 3, and more preferably in the range of 0.3 to 2.5. Is also preferable because it can be suppressed. Further, when the film layer B is based on the number of moles of the repeating unit of the polyester of the film layer B, the ratio of the phosphorus element amount (P _B , mmol%) of the phosphorus compound to the titanium element amount (Ti _B ) ( (P _B / Ti _B ) is in the range of 2 to 20, more preferably 4 to 16, even when a self-recovering polymer is used, generation of foreign matters due to thermal degradation can be suppressed, and precipitation of catalyst residues and the like can be prevented on a flat surface. It is preferable because it can be suppressed to a level that does not affect the surface property. Moreover, in order to reduce the amount of the titanium compound in the film layer B as compared with the film layer A as described above, as a polymerization reaction catalyst, an antimony compound, a germanium compound, and an aluminum compound that are superior in thermal stability compared to the titanium compound. It is preferable to use as the polyester of the film layer B a polyester containing at least one catalyst selected from the group consisting of: Among these, an antimony compound is preferable because it is particularly excellent in thermal stability. Antimony compounds are prone to deposits due to catalyst residues. However, titanium compounds that are difficult to deposit catalyst residues are used together with the catalyst to complement each other, resulting in the reduction of coarse particles. It becomes easy.

  By the way, the intrinsic viscosity of the polyester constituting the film layer B may be 0.01 to 0.1 dl / g, and further 0.02 to 0.08 dl / g lower than the intrinsic viscosity of the polyester constituting the film layer A. preferable. By being in the said range, the flatness fall of the surface of the film layer C by the inert particle | grains in a film layer B, a foreign material, etc. is relieve | moderated by the film layer A, and a high flatness is obtained in the biaxially oriented laminated polyester film obtained. It becomes easy to express sex. Examples of the method for setting the intrinsic viscosity of the film layer B in the above range include a method using a self-recovery polymer for the film B layer.

In the present invention, the inert particles B contained in the above-mentioned film layer B have an average particle diameter (d _B ) of 0.05 to 0.5 μm, more preferably 0.1 to 0.4 μm, and the content thereof is From the viewpoint of the weight of the film layer B, 0.03 to 0.5 wt%, more preferably 0.05 to 0.4 wt% is preferable because flatness and running properties are easily provided. Preferred inert particles are preferably heat-resistant polymer particles and spherical silica particles because of excellent dispersibility. Examples of the heat-resistant polymer particles include crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, crosslinked polyester particles, polyimide particles, and melamine resin particles. Among these, crosslinked polystyrene resin particles and crosslinked silicone resin particles are preferable.

  In the present invention, the inert particle B contained in the film layer B may be a single component system or a multicomponent system, but preferably a multicomponent system containing at least two types of inert particles having different average particle diameters. . More preferably, the inert particles B1 having an average particle diameter of 0.2 to 0.5 μm, and more preferably 0.25 to 0.45 μm, in a range not deteriorating the electromagnetic conversion characteristics, are 0.03 based on the weight of the film layer B. Inactive particles B2 having an average particle diameter of 0.05 to 0.18 μm and further 0.08 to 0.15 μm, and a weight of the film layer B A standard containing 0.05 to 0.3 wt%, more preferably 0.08 to 0.2 wt% is preferable because it can easily provide sufficient air squeezing properties and electromagnetic conversion characteristics. In addition to these particles, considering that the self-recovering polymer is used for the film layer B, the film layer B preferably contains inert particles C in addition to the inert particles B.

In the present invention, when used as a base film for a metal thin film type magnetic recording medium or the like on the surface of the coating layer C, the average protrusion height of 3 nm or more can be easily imparted to the surface of the magnetic layer. It is preferable that fine protrusions of 50 nm or less are formed in a range of 3 × 10 ⁶ pieces / mm ² or more and 60 × 10 ⁶ pieces / mm ² or less. If the average height or frequency of the protrusions is less than the lower limit, the flatness may be impaired due to blocking or transfer of the surface shape of the film layer B to the surface on the film layer C side when stored in a film roll state or the like. Or the magnetic layer formed on the coating layer C side becomes too smooth. For example, when recording and playback are repeated with a digital video tape recorder after becoming a video tape, the magnetic layer is worn by the video head. Easy to do. On the other hand, when the average height or frequency of the protrusions exceeds the upper limit, the output characteristics may be deteriorated when the protrusions are scraped off and fallen into a magnetic recording medium.

  The inert particles C contained in the coating layer C are not particularly limited. For example, the crosslinked silicone resin, acrylic resin, polystyrene, melamine-formaldehyde resin, aromatic polyamide resin, polyamideimide resin, crosslinked polyester, wholly aromatic. Preferred examples include organic particles such as polyester, particles made of silicon dioxide (silica), calcium carbonate, and the like. 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 preferable.

  Moreover, as a binder resin which forms a membrane | film | coat layer, an aqueous polyester resin, an aqueous acrylic resin, an aqueous polyurethane resin etc. are mentioned preferably, for example, An aqueous polyester resin is especially preferable. As the aqueous polyester resin forming the coating layer, the acid component is, for example, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, From polyvalent carboxylic acids such as sebacic acid, dodecanedicarboxylic acid, succinic acid, sodium 5-sulfoisophthalate, potassium 2-sulfoterephthalate, trimellitic acid, trimesic acid, trimellitic acid monopotassium salt and p-hydroxybenzoic acid The glycol component is at least one selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, p-xylylene glycol, for example. , Dimethylo Propane, a polyester resin is at least one selected from the group consisting of polyhydroxy compounds such as ethylene oxide adduct of bisphenol A is preferably used.

  In addition, the water-based polyester resin may be a graft polymer or block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or a specific physical structure (IPN (interpenetrating polymer network)) in a micro particle of two kinds of polymers. Acrylic-modified polyester resin in which a mold, a core-shell type, or the like is formed may be used. As this aqueous polyester resin, a type that dissolves, emulsifies and finely disperses in water can be freely used, but a type that emulsifies and finely disperses in water is preferable. Moreover, since these impart hydrophilicity, for example, a sulfonate group, a carboxylate group, or a polyether unit may be introduced into the molecule.

  If desired, the coating layer C may contain other components such as surfactants, stabilizers, dispersants, UV absorbers, thickeners, release agents, etc., as long as the effects of the present invention are not impaired. You may let them.

  The time for forming the coating layer is not particularly limited and may be applied to the biaxially oriented laminated polyester film, but is preferably applied to the longitudinally uniaxially stretched polyester film. The uniaxially stretched polyester film coated with the aqueous coating liquid is dried and guided to processes such as transverse stretching, re-longitudinal stretching as desired, and then heat setting treatment. For example, a longitudinally uniaxially stretched polyester film coated with an aqueous coating solution is guided by a stenter to be stretched in the transverse direction, optionally re-longitudinally stretched, and heat-set. During this time, the coating solution dries to form a continuous film on the film. Drying is preferably carried out before transverse stretching or during transverse stretching or heat setting.

  In the biaxially oriented laminated polyester film of the present invention, the surface roughness of the coating layer C is WRa measured by WYKO, and may be in the range of 0.5 to 5.0 nm, and further 0.8 to 4.0 nm. For example, when used as a base film of a ferromagnetic metal thin film type magnetic recording medium, it is preferable because excellent handling properties and flatness are easily provided. From the same viewpoint, the biaxially oriented laminated polyester film of the present invention preferably has a surface roughness of the film layer B in the range of 5 nm or more, and further 5 to 12 nm in terms of WRa measured by WYKO. Furthermore, the biaxially oriented laminated polyester film of the present invention has a total film thickness of 2 to 10 μm, more preferably 3 to 8 μm, for example, as a base film for a ferromagnetic metal thin film type magnetic recording medium. Is preferable.

  In addition, the biaxially oriented laminated polyester film of the present invention is orthogonal to the transverse direction (sometimes referred to as the width direction), that is, the film forming direction of the film (sometimes referred to as the longitudinal direction or the longitudinal direction) and the thickness direction. It is preferable that the Young's modulus in the direction to be 8 GPa or more, further 9 GPa or more, and particularly 10 GPa or more. Thus, in order to increase the Young's modulus in the lateral direction, it is necessary to increase the stretching ratio in the lateral direction of the film. According to the study by the present inventors, the film is increased by increasing the stretching ratio in the lateral direction. The push-up due to the inert particles B and foreign matters in the layer B can be alleviated, and further excellent flatness can be easily provided on the surface of the coating layer C. Incidentally, the upper limit of the Young's modulus in the lateral direction is not particularly limited, but is preferably 20 GPa or less, and more preferably 16 GPa or less because the film forming process can be stabilized and the flatness improving effect is saturated. Further, the Young's modulus in the vertical direction is preferably 4 GPa or more, more preferably 5 GPa or more because it easily provides the required dimensional stability when a magnetic recording medium is used. Since it is easy to raise, it is 8 GPa or less, Furthermore, it is preferable that it is 7 GPa or less.

  The biaxially oriented laminated polyester film in the present invention can be produced according to a conventionally known method or a method accumulated in the art. For example, it can be manufactured by first producing an unoriented laminated film, then biaxially orienting the film, and coating the coating layer coating liquid on the surface of the film layer A. This non-oriented laminated film can be produced by a conventionally produced method for producing laminated films. For example, a method of laminating a polyester layer forming a rough surface and a polyester layer forming an opposite surface (flat surface) in a molten state or a cooled and solidified state of polyester can be used. More specifically, it can be produced by a method such as coextrusion or extrusion lamination.

  The unoriented laminated film obtained by the above method can be made into a laminated biaxially oriented film according to the production method of the biaxially oriented film accumulated conventionally. For example, polyester is melted and coextruded at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. to obtain an unstretched laminated film, and the unstretched laminated film is uniaxially (longitudinal or transverse) (Tg− 10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester) and is stretched at a magnification of 2.5 times or more, preferably 3 times or more, and then Tg to (Tg + 70) in the direction perpendicular to the stretching direction. ) It is preferable that the film is stretched at a magnification of 2.5 times or more, preferably 3 times or more at a temperature of ° C. Further, if necessary, the film may be stretched again in the machine direction and / or the transverse direction. Thus, the total draw ratio is preferably 9 times or more, more preferably 12 to 35 times, and particularly preferably 15 to 30 times as the area draw ratio. Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° C. to (Tm−10) ° C., for example, preferably heat-set at 180 to 250 ° C. The heat setting time is preferably 1 to 60 seconds.

  The biaxially oriented laminated polyester film of the present invention is preferably used as a base film for high-density magnetic recording media or high-density digital recording media (data cartridges, digital video tapes, etc.), and has particularly flatness and adhesiveness. It is suitable as a base film for required metal thin film magnetic recording media.

  Hereinafter, the present invention will be described in further detail with reference to examples. Various physical property values and characteristics in the present invention are measured and evaluated as follows.

(1) Average particle diameter of inert particles in the coating layer A platinum thin film deposition layer is provided on the surface of the coating layer of the base film with a platinum sputtering device with a thickness of 2 to 3 nm, and a scanning electron microscope (Hitachi High-Technologies S) -4700), the area equivalent circle diameter was determined for at least 100 particles, and the average value was taken as the average particle size.

(2) Average particle size (DP) of inert particles in the polyester film
The polyester is removed from the film surface by a plasma low-temperature ashing method (for example, P3-3 type manufactured by Yamato Kagaku) to expose the particles. The treatment conditions are such that the polyester is ashed but the particles are not damaged. This is observed with an SRM (scanning electron microscope), and the image of the particle (light density produced by the particle) is connected to an image analyzer, and the following numerical processing is performed with the number of particles of 5000 or more by changing the observation location. The number average particle diameter d obtained by the above is defined as the average particle diameter.

ここで、ｄｉは粒子の円相当径（μｍ）、ｎは個数である。サンプルをポリエステルは溶解するが粒子は溶解しない溶媒を用いて溶解し、溶液から粒子を遠心分離し、粒子の全体量に対する比率（重量％）をもって粒子含有量とする。

Here, di is the equivalent-circle diameter (μm) of the particles, and n is the number. The sample is dissolved using a solvent in which the polyester is dissolved but the particles are not dissolved, and the particles are centrifuged from the solution to obtain the particle content in a ratio (% by weight) to the total amount of the particles.

(3) Film thickness 10 layers of base film are removed while excluding air between layers. In accordance with JIS standard C2151, the thickness is increased by 10 sheets using Mitutoyo dial gauge MDC-25S. Measure and calculate the film thickness per sheet. This measurement was repeated 10 times, and the average value was defined as the film thickness per sheet.

  On the other hand, the thicknesses of the A layer and the B layer are obtained by fixing a small piece of film with an epoxy resin and cutting an ultrathin section (cut in parallel with the film forming direction and the thickness direction) of about 60 nm with a microtome. create. A sample of this ultrathin section is observed with a transmission electron microscope (H-800, manufactured by Hitachi, Ltd.). The layer with more inert particles is the B layer and the layer with fewer inert particles is the A layer. The thickness positions at which the abundance changes were determined at 100 locations, and the thicknesses of the A layer and the B layer were determined from their average values.

(4) Thickness of coating layer A small piece of film is fixed and molded with an epoxy resin, and an ultra-thin section (cut parallel to the film forming direction) of about 60 nm in thickness is made with a microtome, and this sample is transmitted. It was observed with a scanning electron microscope (H-800, manufactured by Hitachi, Ltd.), and the layer thickness was determined from the boundary line of the layers. In addition, the measurement of this layer thickness was performed in the part where a particle | grain does not exist.

(5) Height and frequency of protrusions Using an atomic force microscope (trade name: NanoScope III) manufactured by Digital Instruments and an AFM J-scanner, 10 areas of 2 μm × 2 μm were measured under the following conditions, and AFM images The number of protrusions having a height of 1 nm or more is counted, and the average value is calculated as the number of protrusions per piece / mm ² by area conversion. Also, the height of each counted protrusion is measured, and the average value is taken as the average height of the protrusion.
Deep needle: Single crystal silicon nitride Scanning mode: Tapping mode Area number: 256 × 256 Data points Scanning speed: 2.0 Hz
Measurement environment: room temperature, air

(6) Young's modulus The film is cut into a sample width of 10 mm and a length of 15 cm, and the distance between chucks is 100 mm, and the film is pulled with an Instron type universal tensile tester under the conditions of a tensile speed of 10 mm / min and a chart speed of 500 mm / min. The Young's modulus is calculated from the tangent of the rising part of the obtained load-elongation curve.

(7) Element amount in polymer:
The titanium element amount, phosphorus element amount, antimony element amount, germanium element amount and aluminum element amount in the A layer or the B layer were prepared by heating and melting the sample to create a circular disk, and using a fluorescent X-ray measuring apparatus 3270 manufactured by Rigaku Corporation. Measured. In addition, when titanium oxide particles, alumina particles, or the like are added as inert particles, not as a catalyst, the ratio thereof is excluded from the above element amounts.

(8) Electromagnetic conversion characteristics and dropout After a cobalt-oxygen thin film having a thickness of 180 nm is formed on one surface (A layer side) of the obtained biaxially oriented laminated polyester film by vacuum deposition, a diamond-like film is formed thereon by sputtering. A carbon protective film was formed in a conventional manner with a thickness of 10 nm, and then a fluorine-containing fatty acid ester lubricant was applied with a thickness of 3 nm. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone is provided on the surface on the B layer side with a thickness of 400 nm, slitted to a width of 6.35 mm by a slitter, and wound on a reel to form a magnetic recording tape (DVC video tape). Created.

The characteristics evaluation of the magnetic recording tape described above was performed by obtaining a video S / N ratio using a commercially available camera-integrated digital video tape recorder. For measurement of the S / N ratio, a signal was supplied from a TV test signal generator, and a commercially available DVC-LP tape (manufactured by Sony Corporation, trade name: DVM80R3) was used at 0 dB (dB) using a video noise meter. As a comparative measurement and evaluated according to the following criteria. The traveling conditions are 25 ° C. and 60% RH.
◎: +1.0 dB or more ○: −0.5 dB or more, less than +1.0 dB Δ: −2.0 dB or more, less than −0.5 dB ×: less than −2.0 dB Here, “◯” indicates vapor deposition type high density recording. As a magnetic tape application, it means an excellent level, Δ means that it can be used, and X means an insufficient level.

In addition, this magnetic recording tape is recorded and reproduced in a quiet room using the LP mode of a commercially available camera-integrated digital video tape recorder (Sony Corporation DCR-VX2100) to determine the number of dropouts (DO). I went in particular. The number of DOs was measured by recording on a prepared DVC tape with a commercially available DVC camera, playing back for 1 minute, counting the number of block-like mosaics displayed on the screen, and evaluating according to the following criteria. The traveling conditions are 25 ° C. and 60% RH.
◎: No occurrence ○: Less than 5 pieces / minute ×: More than 5 pieces / minute

(9) Surface roughness (WRa)
Using a non-contact type three-dimensional roughness meter (WYKO NT-2000) manufactured by Veeco, the number of measurements (n) is 10 or more under the conditions of a measurement magnification of 25 times and a measurement area of 247 μm × 188 μm (0.046 mm ² ). And the center plane average roughness (WRa) is obtained by surface analysis software built in the roughness meter. The center plane average roughness (WRa) is a value calculated and output by the following equation.

ここで、Ｚ_jkはＸ軸方向（２４７μｍ）、それと直行するＹ軸方向（１８８μｍ）をそれぞれＭ分割、Ｎ分割したときの各方向のｊ番目、ｋ番目の位置に於けるＸ、Ｙ平面における直行するＺ軸方向の高さである。

Here, Z _jk is in the X and Y planes at the j-th and k-th positions in the respective directions when the X-axis direction (247 μm) and the Y-axis direction (188 μm) perpendicular thereto are divided into M and N, respectively. It is the height in the Z-axis direction that goes straight.

(10) Measurement of volume resistivity The volume resistivity of the molten film is measured using the apparatus shown in FIG. The measurement sample 1 uses a film having a thickness of about 150 μm. An upper electrode 3 having a diameter of 5.6 cm and a thickness of 0.2 cm capable of holding a parallel gap of 150 μm is disposed on the upper surface of the cylindrical lower electrode 2 having a diameter of 20 cm, and the measurement sample is in close contact with the electrode in the meantime. insert.

  The lower electrode 2 has a built-in charging device 4 and a temperature detection end 5, the variation in the surface temperature measurement of the lower electrode is within 1 ° C, and the temperature difference from the detection end portion is 2 ° C at a heating rate of 8 ° C / min. Configure to be within. The detected temperature is measured with a reading thermometer 7. The entire electrode is placed in the heat insulating box 11.

  The power supply 8 applies the generated voltage between the two electrodes via the standard resistor 9, which is a power supply that generates a direct current of 100V when measuring the DC volume resistivity of the film, and the AC volume of the film. When measuring the resistivity, the power source generates 100 V and 50 Hz. The current flowing in this circuit is read by the eletron meter 10 having an internal impedance of 100 MΩ or more as a voltage generated across the standard resistor.

The AC volume resistivity of the film-like polymer is measured by the above apparatus at a temperature measurement rate of the lower electrode of 8 ° C./min, and the electrode is melted by DSC of the polymer + 30 ° C. The AC volume resistivity Z Is obtained from the applied voltage E, current I, electrode area S, and electrode interval d by the following equation.

(11) Film cost Judgment was made as follows from the ratio of the recovered polymer that can use the most recovered polymer without changing the composition with only the resin used.
○: Recovery ratio (R) is 40% or more Δ: Recovery ratio (R) is 20% or more to less than 40% ×: Recovery ratio (R) is less than 20%

[Example 1]
Preparation of Resin 1 After transesterification using 100 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester, 70 parts of ethylene glycol and titanium compound as titanium compound so that the amount of titanium element was 8 mmol%, Trimethyl phosphate was added as a phosphorus compound as a stabilizer so that the amount of phosphorus element was 13 mmol%, and the transesterification reaction was completed. Then, after adding 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt as a sulfonic acid quaternary phosphonium salt compound to 2 mmol%, a polycondensation reaction is performed under a high vacuum, so that substantially inert particles are obtained. Thus, polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.63 dl / g was obtained.

Preparation of Resin 2 After transesterification using 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol as a transesterification catalyst so that manganese acetate tetrahydrate is 30 mmol%, trimethyl phosphate is used as a stabilizer. The transesterification reaction is terminated by adding the phosphorus element amount to 40 mmol%, and then 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt is added to 2 mmol% as the sulfonic acid quaternary phosphonium salt compound. After the addition, antimony trioxide is added as a polymerization catalyst so that the amount of elemental antimony is 20 mmol%, and a polycondensation reaction is performed under high vacuum to obtain polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.63 dl / g. It was. In addition, the resin 2 has a spherical silica particle having an average particle diameter of 300 nm and a spherical silica particle having an average particle diameter of 130 nm at the stage of the transesterification reaction, each 0.19 weight based on the weight of the obtained resin. % And 0.23% by weight.

A resin 1 was prepared for the flat layer (film layer A), while a resin 1 and a resin 2 were mixed at a weight ratio of 57:43 for the rough surface layer (film layer B).
These polymers for film layer A and film layer B were each dried at 170 ° C. for 6 hours. Thus, the dried chips were supplied to the two extruder hoppers at a ratio so as to have the layer thickness configuration shown in Table 1, and melted at a melting temperature of 280 to 300 ° C., using a multi-manifold coextrusion die. The film layer B was laminated on one side of the film layer A to obtain a laminated unstretched film having a thickness of 88 μm.

This laminated unstretched film had an AC volume resistivity of 1 × 10 ⁸ Ω · cm.
The laminated unstretched film thus obtained is preheated to 120 ° C., further heated to 135 ° C. between low-speed and high-speed rolls and stretched 3.5 times, and then rapidly cooled to obtain a longitudinally stretched film. Obtained. Subsequently, the aqueous coating liquid (total solid content concentration 1.0%) of the following composition was apply | coated on the surface which consists of the film layer A of a longitudinally stretched film.

Application aqueous solution on the surface A side:
・ Binder Acrylic-polyester resin 79%
Polyester component: isophthalic acid (95 mol%), 5-sodium sulfoisophthalic acid (5 mol%) / ethylene glycol (92 mol%), diethylene glycol (8 mol%)
Acrylic resin component: methyl methacrylate (90 mol%), glycidyl methacrylate (10 mol%),
Weight ratio of polyester component / acrylic resin component = 5/5
・ Inert particles (acrylic filler (average particle size 25 nm, manufactured by Nippon Shokubai Co., Ltd., trade name: eposter)) 6%
・ Surfactant (manufactured by Sanyo Chemical Co., Ltd., trade name Sannonic SS70) 15%
Film layer thickness (after drying): 6 nm

  Then, it supplied to the stenter and extended | stretched 5.3 times in the horizontal direction at 150 degreeC. The obtained biaxially stretched film was heat-fixed with hot air at 205 ° C. for 4 seconds to obtain a biaxially oriented laminated polyester film having a thickness of 4.7 μm. The Young's modulus was 5.6 GPa in the vertical direction (film forming direction) and 11.0 GPa in the horizontal direction (film width direction).

  Subsequently, scraps such as edges produced during the production of the biaxially oriented laminated polyester film were collected and pulverized again to obtain a collected polymer. And as a polymer of the film layer B, the ratio of the recovered polymer used is the highest under the conditions that do not change the composition of the inert particles B1 and B2 without using a resin other than the resin 1 and the resin 2. The recovered polymer was used by repeating the same operation as that of the biaxially oriented laminated polyester film that did not use the recovered polymer except that the recovered polymer and the resin 2 were used in a weight ratio of 78:22. A biaxially oriented laminated polyester film was produced. The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Comparative Example 1]
The same operation as in Example 1 was repeated except that the resin of the film layer A was changed and the recovery destination of the recovered polymer was changed to the film layer A. The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1. In the film layer A, spherical silica particles having an average particle diameter of 300 nm were 0.026 wt%, and spherical silica particles having an average particle diameter of 130 nm were 0.032 wt%.

[Examples 2 and 3]
The same operation as in Example 1 was repeated except that the thickness of the coating layer was changed. The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Examples 4 and 5 Comparative Example 2]
The same operation as in Example 1 was repeated except that the thicknesses of the film layer A and the film layer B were changed and the use ratio of the recovered polymer was changed. The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Comparative Example 3]
The same operation as in Example 1 was repeated except that the coating liquid applied on the surface comprising the film layer A was changed as follows, and the thickness of the coating layer was changed to 25 nm after drying. The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.
-Total solid content: 4.2%
・ Binder: Acrylic-polyester resin 83.6%
..Polyester component: isophthalic acid (95 mol%), 5-sodium sulfoisophthalic acid (5 mol%) / ethylene glycol (92 mol%), diethylene glycol (8 mol%)
Acrylic resin component: methyl methacrylate (90 mol%), glycidyl methacrylate (10 mol%),
..Weight ratio of polyester component / acrylic resin component = 5/5
Inert particles (acrylic filler (average particle size 25 nm, manufactured by Nippon Shokubai Co., Ltd., trade name: Eposta)): 1.4%
・ Surfactant (manufactured by Sanyo Kasei Co., Ltd., trade name Sannonic SS70): 15%

  The biaxially oriented laminated polyester film of the present invention can exhibit excellent electromagnetic conversion characteristics when used as a high-density magnetic recording medium, but can also use a self-recovery polymer and has excellent characteristics in terms of cost merit. It is useful as a base film for high-density magnetic recording media, particularly as a digital recording video tape or data storage tape.

It is a schematic diagram of the apparatus which measures the volume resistivity of a molten polymer. It is a schematic diagram which shows the method of a self-circulation collection | recovery when using a collection polymer.

Explanation of symbols

1: Polymer 2: Lower electrode 3: Upper electrode 4: Electric device 5: Temperature detection end 6: Ammeter 7: Reading thermometer 8: Power source 9: Standard resistance 10: Electron meter 11: Insulation box 21: Unused polymer I
22: Unused polymer II
23: Recovery polymer 24: A layer 25: B layer 26: Commercialized laminated film 27: Collected laminated film

Claims (9)

It consists of a film layer A, a film layer B laminated on one surface of the film layer A, and a coating layer C laminated on the other surface of the film layer A,
The film layer A does not contain inert particles and has a thickness in the range of 0.5 to 5 μm;
The film layer B is thicker than the film layer A and is 9.5 μm or less, and the average particle diameter is 0.01 to 0.1 times the thickness of the film layer B (tB). Containing particles B,
Coating layer C, an average particle diameter made inactive particles C and a binder resin of 5 to 50 nm, the thickness is in the range of 1 to 20 nm, and
The film layer B contains the inert particles C contained in the coating layer C, and the self-recovering polymer produced in the process of producing the biaxially oriented laminated polyester film is used for a part of the polyester constituting the film layer B. A biaxially oriented laminated polyester film, characterized in that the magnetic layer is used as a base film of a magnetic recording tape having a ferromagnetic metal thin film layer . 2. The biaxial film according to claim 1, wherein the coating layer C has fine protrusions having an average protrusion height of 3 nm or more and 50 nm or less on a surface thereof in a range of 3 × 10 ⁶ pieces / mm ² or more and 60 × 10 ⁶ pieces / mm ² or less. Oriented laminated polyester film.   The surface roughness (WRa) of the coating layer C is in the range of 0.5 to 5 nm, the surface of the film layer B is rougher than the surface A and 5 nm or more, and the sum of both surface roughnesses is at most 12 nm. 2. A biaxially oriented laminated polyester film according to 1.   The biaxially oriented laminated polyester film according to claim 1, wherein the entire film has a thickness of 2 to 10 μm.   The biaxially oriented laminated polyester film according to claim 1, wherein the film layer B contains at least two kinds of inert particles having different average particle diameters.   The biaxially oriented laminated polyester film according to claim 1, wherein the intrinsic viscosity of the polyester constituting the film layer B is 0.01 to 0.1 dl / g lower than the intrinsic viscosity of the polyester constituting the film layer A.   The biaxially oriented laminated polyester film according to claim 1, wherein the Young's modulus in the transverse direction of the biaxially oriented laminated polyester film is 8 GPa or more.   The biaxially oriented laminated polyester film according to any one of claims 1 to 7, wherein the polymer of the film layer A and the film layer B is polyethylene terephthalate or polyethylene-2,6-naphthalate.   The biaxially oriented laminated polyester film according to claim 1, wherein the polyester constituting at least one of the film layer A and the film layer B contains 0.02 to 45 mmol% of a sulfonic acid quaternary phosphonium salt compound.

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