JP6301711B2 - Oriented laminated polyester film - Google Patents

Description

  The present invention relates to an oriented laminated polyester film having an extremely flat surface such as a base film used for an ultra-high density recording medium of 1.5 TB or more and having a good film handling and excellent workability even though it is a thin film. .

  Polyester films have been used for base films such as magnetic recording tapes because they are relatively inexpensive and have excellent mechanical properties. And when using for the base film of a magnetic-recording tape, it is calculated | required that a polyester film has a flat surface without a rough protrusion and a fault. On the other hand, in a coating type magnetic recording tape formed by coating a magnetic layer on a polyester film, a uniform magnetic layer is efficiently produced if the winding property of the base film and handling properties in the coating process are unstable. I can't. Therefore, even if the polyester film contains particles as a lubricant and forms protrusions on the surface to improve the winding property or the base film thickness is reduced to improve the recording capacity, it can be handled well. It has been studied to improve the mechanical properties of the polyester film as possible.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-41019) proposes that mechanical strength and the like can be increased by containing a large amount of plate-like inorganic particles at 10 to 90% by weight. Further, Patent Document 2 (Japanese Patent Laid-Open No. 2008-69227) proposes a smooth surface that can withstand practical use while increasing Young's modulus by dispersing 0.5 to 3% by weight of acicular boehmite particles. ing. Furthermore, by adjusting the film forming conditions at the time of stretching, even if inorganic particles are contained at a high concentration of 0.2 to 3% by mass, the breakage is suppressed, and the number of surface protrusions of the finally obtained film is increased. Patent Document 3 (Japanese Patent Laid-Open No. 2011-173258) proposes improving crystallinity.
However, even with the techniques proposed in these patent documents 1 to 3, the handling required as the film thickness is reduced while forming an extremely flat surface as required for the base film of an ultra-high density recording medium of 1.5 TB or more. Therefore, further improvement has been desired.

JP 2003-41019 A JP 2008-69227 A JP 2011-173258 A

  An object of the present invention is an oriented laminated polyester film having a high surface property required for an ultra-high density magnetic recording medium having a capacity exceeding 1.5 TB, an electromagnetic conversion characteristic associated therewith, and a workability associated with thinning. May provide.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have adopted a layer structure of a laminated film, and in a thin film layer therein, highly inert particles having a very small particle size are highly concentrated. The present inventors have found that the above problems can be solved by making them exist in a dispersed state, and have reached the present invention.

Thus, according to the present invention, two layers in which the film layer B is laminated on one side of the film layer A, or a three-layer laminated film further having the film layer C on the surface not contacting the film layer A of the film layer B There,
The film layer A contains 4 to 20% by weight of spherical inorganic particles A having a particle size of 10 nm to 80 nm, and the degree of dispersion of the inorganic particles A is 80% or more,
In the case of the three-layer laminated film having the film layer C, the film layer B does not contain inorganic particles having a particle size of 10 nm or more, or even if contained, the content of the inorganic particles B having a particle size of 10 nm or more is 0.05 mass. % In the case of a two-layer laminated film having no film layer C, the inorganic particles B having an average particle size of 10 to 80 nm are 0.01 to 0.1 mass based on the mass of the film layer B. % Containing ,
The ratio (tA / tB) of the thickness (tA) of the film layer A to the thickness (tB) of the film layer B is in the range of 0.02 to 0.25, and
The ratio (tA / DA) of the thickness (tA) of the film layer A and the average particle diameter (D) of the inorganic particles A is in the range of 5-25.
The film layer C contains 1 to 20% by weight of inorganic particles C having a particle size of 10 nm to 80 nm, the dispersion degree of the inorganic particles C is 80% or more, and the thickness (tC) of the film layer C and the average particle size of the inorganic particles C The ratio of (D) (tC / DC) is in the range of 0.1-2 ;
The film layers A, B and C are provided with an oriented laminated polyester film in which the proportion of inorganic particles having a particle size of more than 80 nm is 100 or less in all 5000 measured particles .

According to the present invention, as a preferred embodiment of the present invention, the surface roughness (Ra1) of the surface of the oriented laminated polyester film on the film layer A side is in the range of 4 to 10 nm, and the surface roughness (Ra2) of the other surface. ) Is in the range of 0.3 to 1.5 nm, the sum of the Young's modulus (YMD1) in the main orientation direction of the oriented laminated film and the Young's modulus (YMD2) in the direction perpendicular thereto is 15 GPa or more, Layer A and film layer C are made of the same resin composition, polyester has ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate as a main repeating unit, and spherical particles whose inorganic particles are mainly composed of silica An oriented laminated polyester fiber having at least one of a thickness of 2.0 μm or more and 6.0 μm. Lum is also provided.
Furthermore, according to the present invention, a magnetic recording medium comprising the above-described oriented laminated polyester film of the present invention and a recording layer formed on the surface on the side different from the film layer A, and the recording layer is a coating type magnetic layer A recording medium is also provided.

  The biaxially oriented laminated polyester film of the present invention has a very flat surface, such as a base film used for an ultra-high density recording medium of 1.5 TB or more, and is easy to handle even though it is a thin film. Therefore, it can be suitably used for a coating type magnetic recording tape, particularly a data storage base film.

  Hereinafter, the present invention will be described in detail. For convenience of explanation, the film forming direction of the film may be referred to as a mechanical axis direction, a vertical direction, a longitudinal direction, and an MD direction, and a direction orthogonal to the film forming direction and the thickness direction is referred to as a width direction, a lateral direction, Sometimes referred to as TD direction.

<Polyester>
As the polyester in the present invention, a known polyester can be adopted as long as it can be formed into a film. For example, an aromatic polyester obtained by polycondensation of a diol component and an aromatic dicarboxylic acid component is preferable. Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, and the like. 6,6 ′-(alkylenedioxy) di-2-naphthoic acid. Examples of the diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol.

  Among these, ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate is the main repeating unit from the viewpoint of dimensional stability during processing at high temperature, and ethylene-2,6-naphthalene is particularly preferable. Those having carboxylate as the main repeating unit are preferred. The term “main” as used herein means preferably 60 mol% or more, 70 mol% or more, 80 mol% or more, and more preferably 90 mol% or more.

  Further, from the viewpoint of further improving the dimensional stability against environmental changes, the 6,6 ′-(ethylenedioxy) di-2-naphthoic acid component described in International Publication No. 2008/096612 pamphlet, 6,6 ′-( 6,6 ′-(alkylenedioxy) di-2-naphthoic acid components such as trimethylenedioxy) di-2-naphthoic acid component and 6,6 ′-(butylenedioxy) di-2-naphthoic acid component The thing copolymerized is also mentioned. The copolymerization amount of the (alkylenedioxy) di-2-naphthoic acid component is preferably in the range of 5 to 40 mol%, more preferably in the range of 6 to 35 mol%, particularly 7 to 7 mol, based on the number of moles of the total dicarboxylic acid component. It is in the range of 30 mol%. In the case of copolymerizing the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, an ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate component and 6,6 ′-(alkylenediene) The total amount of the (oxy) di-2-naphthoic acid component is preferably 90 mol% or more of the total acid component.

  When the polyester in the present invention does not contain a 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, it is 6,6 ′-(alkylenedioxy) di- in o-chlorophenol at 35 ° C. When the 2-naphthoic acid component is contained, the intrinsic viscosity when measured in a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (40/60 weight ratio) at 35 ° C. is 0. It is preferably 40 dl / g or more, more preferably 0.40 to 1.0 dl / g. If the intrinsic viscosity is less than 0.4 dl / g, cutting may occur frequently during film formation, or the strength of the product after forming may be insufficient. On the other hand, when the intrinsic viscosity exceeds 1.0 dl / g, productivity during polymerization is lowered.

The melting point of the polyester in the present invention is preferably 200 to 300 ° C, more preferably 210 to 290 ° C, and particularly preferably 220 to 280 ° C. If the melting point is less than the lower limit, the heat resistance of the biaxially oriented film may be insufficient, and if the melting point exceeds the upper limit, the temperature during melt kneading becomes very high, which tends to cause thermal degradation.
The polyester in the present invention is further copolymerized with other copolymer components known per se within a range not impairing the effects of the present invention, for example, 10 mol% or less, further 5 mol% with respect to the number of moles of repeating units. Copolymerization may be carried out in the following range, and other thermoplastic resins and the like may be blended in a range of, for example, 20% by weight or less, and further 10% by weight or less.

<Oriented laminated polyester film>
The oriented laminated polyester film of the present invention is a two-layer laminate in which a film layer B is laminated on one side of the film layer A, or a three-layer laminate having a film layer C on the surface of the film layer B that is not in contact with the film layer A. It is a film. Each film layer can be produced from the polyester described above. Hereinafter, the film layer A, the film layer B, and the film layer C will be described.

[Film layer A],
From the viewpoint of maintaining high electromagnetic conversion characteristics when data storage is performed while maintaining excellent processing characteristics, the film layer A may contain spherical inorganic particles A having a particle diameter in the range of 10 to 80 nm. is necessary. The average particle diameter of the inorganic particles A is 15 nm to 80 nm, more preferably 20 nm to 78 nm, and particularly preferably 30 nm to 75 nm. When the average particle size is in the above range, it is easy to highly improve the strength and maintain the surface smoothness.

  The content of the spherical inorganic particles A is preferably 4 to 20% by mass based on the mass of the film layer A. More preferably, it is 4.5-19 mass%, Most preferably, it is 5-18 mass%. If the content of the inorganic particles A is less than the lower limit, the surface property of the surface of the A layer becomes too smooth, causing a problem in film transport, and the effect of improving the strength of the film by the inorganic particles A is not sufficient. On the other hand, if the content exceeds the upper limit, a large amount of inorganic particles are present in the film layer A, which causes a problem that the surface roughness becomes excessively large or the lubricant is dropped during film transport.

  As described above, even if the inorganic particles A have a high concentration, the inorganic particles A to be used need to have a dispersity of 80% or more in order to have sufficient surface properties. More preferably, it is 81% or more, More preferably, it is 82% or more, Most preferably, it is 85% or more. If the dispersibility is less than this, the ratio of the aggregated particles present increases, so that the surface properties of the film are deteriorated particularly when a large amount of particles are contained.

  Furthermore, it is preferable that ratio (tA / DA) of the thickness (tA) of the film layer A of this invention and the average particle diameter (DA) of the inorganic particle A which the film layer A contains is 5-25. More preferably, it is 6-23, Most preferably, it is 7-22. When the ratio of tA / DA is less than the lower limit, the surface formed by the film layer A is too flat, and thus the conveyance of the film is likely to be hindered. On the other hand, when the upper limit is exceeded, the smoothness of the surface formed by the film layer A becomes insufficient.

<Film layer B>
The film layer B in the present invention does not contain inorganic particles having a particle size of 10 nm or more, or even if contained, the content of the inorganic particles B having a particle size of 10 nm or more is 0.1 mass based on the mass of the film layer B. % Or less. Particularly preferably, in the case of a three-layer laminated film having a film layer C described later, the content of inorganic particles B having a particle size of 10 nm or more is 0 even if it contains no inorganic particles having a particle size of 10 nm or more. .05% by mass or less, more preferably 0.02% by mass or less, and in the case of a two-layer laminated film having no film layer C described later, inorganic particles B having an average particle size of 10 to 80 nm, It is preferable to contain in the range of 0.01-0.1 mass%, and also 0.03-0.1 mass% on the basis of the mass of the film layer B. This is to make the surface formed by the film layer B very smooth, especially when used as a base film when making a magnetic tape, the surface on the side different from the film layer A forms a magnetic layer. From the viewpoint of use as a surface to be used.

  Further, in order to smooth the surface, the ratio of the thickness (tA) of the film layer A to the thickness (tB) of the film layer B (tA /) so that the influence of the film layer A is not affected on the surface formed by the film layer B. tB) is preferably 0.02 to 0.25. More preferably, it is 0.03-0.24, Most preferably, it is 0.04-0.23. When the ratio of tA / tB is below the lower limit, the film layer A has inorganic particles at a high concentration in a state where the thickness of the film layer A is not sufficient, so that the lubricant is easily dropped during film transport. On the other hand, if the upper limit is exceeded, the inorganic particles contained at a high concentration will affect the film layer B side, and the surface smoothness on the film layer B side will be deteriorated.

<Film layer C>
When the oriented laminated polyester film of the present invention is a three-layer laminated film having a film layer C on the side of the film layer B that is not in contact with the film layer A, the film layer C contains inorganic particles C having a particle size of 10 to 80 nm. . The preferable average particle diameter of the inorganic particles C is 20 to 80 nm, and further 30 to 78 nm. Since the film layer C becomes the surface of the magnetic layer when a coating type magnetic recording medium is prepared, a very smooth surface is required. When the particle size is larger than the above, the smoothness cannot be formed. It is preferable that the film layer C is made of the same resin composition as the film layer A so as not to be complicated in terms of equipment.

  Since the film layer C has excellent smoothness, the ratio (tC / DC) of the thickness (tC) of the film layer C to the average particle diameter (DC) of the inorganic particles C contained in the film layer C is 0. A range of 1 to 2 is preferable. More preferably, it is 0.2-1.9, Most preferably, it is 0.4-1.8. When the ratio of tC / DC is lower than the lower limit, slipping off of the lubricant during film conveyance becomes significant. On the other hand, when the upper limit is exceeded, the surface roughness as the surface on which the magnetic layer is formed cannot be achieved.

  From such a viewpoint, even if the inorganic particles C also have a high concentration, the inorganic particles C used preferably have a dispersity of 80% or more in order to have sufficient surface properties. More preferably, it is 81% or more, More preferably, it is 82% or more, Most preferably, it is 85% or more. If the dispersibility is less than this, the ratio of the aggregated particles present increases, so that the surface properties of the film are deteriorated particularly when a large amount of particles are contained.

<Inorganic particles>
In the inorganic particles A, B, and C in the present invention, the relative standard deviation of the particle size of all particles when viewing the particle size distribution curve of each particle is preferably 20% or less, more preferably 15% or less. From such a viewpoint, it is preferable to have a single peak when viewing the particle size distribution curve. Whether or not there is a single peak is determined by creating a particle size distribution curve with the particle diameter on the horizontal axis and the particle frequency on the vertical axis, and when the measurement pitch of the particle diameter on the horizontal axis is 0.01 μm, there is only one peak. Even if there are a plurality of peaks, it means that there is no dent that is 50% or less with respect to the height of the lower peak between the peaks.

In addition, the inorganic particles A, B, and C, particularly the inorganic particles A in the present invention are preferably spherical. Although the effect of improving the strength by particles having a shape such as a needle shape or a plate shape is recognized, there is a concern that the strength of the film may be anisotropic or the surface property may be deteriorated. Use of spherical particles having an isotropic effect on strength is preferred.
The spherical shape in the present invention means that having an aspect ratio of 1.0 to 1.5 constituted by the ratio of the major axis to the minor axis of the particles, preferably 1.0 to 1.3, more preferably Means 1.0 to 1.2.

  By the way, as the inorganic particles to be contained in the oriented laminated polyester film of the present invention, very few inorganic particles are preferable even if they do not originally contain or contain coarse particles. From such a viewpoint, the proportion of the inorganic particles having a particle diameter exceeding 80 nm is 100 or less, further 50 or less, especially 25 or less in all 5000 measurement particles as described in the measurement method described later. preferable. Therefore, the inorganic particles to be contained are preferably particles having a sharp particle size distribution curve, and are preferably present in the form of primary particles. In addition, because of the necessity of having a reinforcing effect, inorganic particles having a high elastic modulus are used. Is suitable. In particular, spherical silica particles are preferred. Of course, when spherical silica particles are contained, it is preferable to filter with a filter, treat the surface of the particles with a dispersant, or strengthen kneading with an extruder in order to eliminate coarse particles. The oriented laminated polyester film of the present invention may contain organic particles as long as the effects of the present invention are not impaired, but preferably 0.1% by mass or less based on the mass of the oriented laminated polyester film, It is preferably 0.05% by mass or less, particularly 0.01% by mass or less.

  By the way, as a method of achieving dispersibility at a high concentration, a method of increasing the affinity with polyester by treating the surface of the particles with a surface treatment agent is preferable. For example, silica is used for inorganic particles. In this case, treatment with a silane coupling agent is effective. By heat treating the silane coupling agent or by graft polymerization, the silica surface can be modified and the affinity with the polyester can be increased. As a result, even if it contains inorganic particles at a high concentration, it can be dispersed. It becomes possible to produce polyester having excellent properties. By using polyester with excellent dispersibility while containing inorganic particles in such a high concentration, and strengthening filtration with a fine filter until the desired degree of dispersion is achieved, or by increasing the shear stress during melt kneading The dispersibility of the particles in the film can be increased.

<Others>
The oriented laminated polyester film of the present invention preferably has the following surface roughness so that good electromagnetic conversion characteristics can be obtained when it is formed into a coating type magnetic recording medium.
First, the surface roughness (Ra1) on the film layer A side of the oriented laminated polyester film of the present invention is 4 to 10 nm, preferably 4.2 to 9.5 nm, and particularly preferably 4.4 to 9.0 nm. . If the surface roughness (Ra1) is below the lower limit, the surface of the film layer A becomes too smooth, so that the transportability of the film tends to be lowered. On the other hand, if the surface roughness exceeds the upper limit, the surface of the film layer A becomes too rough. For this reason, when a coating type magnetic recording medium is produced, it tends to cause deterioration of electromagnetic conversion characteristics due to transfer to the magnetic layer side.

  On the other hand, the other surface of the oriented laminated polyester film of the present invention is different from the film layer A side (in the case of a two-layer laminated film comprising film layer A and film layer B, the surface of film layer B, film layer A and film layer). In the case of a three-layer laminated film composed of B and film layer C, the surface of film layer C) has a surface roughness (Ra2) of 0.3 to 1.5 nm, preferably 0.3 to 1.4 nm. More preferably, it is 0.3 nm-1.3 nm. When the surface roughness (Ra2) is larger than the upper limit, in a high-capacity magnetic recording medium having 1.5 TB or more, it becomes difficult to obtain a magnetic tape capable of obtaining sufficient electromagnetic conversion characteristics. The frictional force at the time of contact with the roll at the time of conveyance is remarkably increased, so that the productivity of the base film is remarkably lowered. The other surface, which is different from the film layer A, can be said to be a surface on the side on which the recording layer is formed.

  The total thickness of the oriented laminated polyester film of the present invention is preferably 2.0 μm or more and 6.0 μm or less. The lower limit of the preferable total thickness is 2.5 to 5.5 μm, more preferably 3.0 to 5.0 μm, and particularly 4.0 to 4.5 μm. When the thickness is smaller than the lower limit, the tape loses its elasticity, so that the electromagnetic conversion characteristics are deteriorated and wrinkles are easily formed in the coating process. When the thickness exceeds the upper limit, the tape length per one tape is shortened, so that it is difficult to reduce the size and increase the capacity of the magnetic tape.

  From the viewpoint of imparting excellent workability, the oriented laminated polyester film of the present invention is preferably a biaxially oriented laminated polyester film, and has a Young's modulus (YMD1) in the main orientation direction and a Young's modulus (YMD1) in a direction perpendicular thereto. The sum of YMD2) is preferably 15 GPa or more. More preferably, it is 15.5 GPa or more, More preferably, it is 16 GPa or more. If the Young's modulus is less than this, in the production of high-capacity magnetic recording media that require more smoothness, the film loses rigidity due to heat in the transport process, or the film may be cut by friction due to smoothness. I'm sorry. The upper limit of the sum of Young's moduli is not particularly limited, but if it is attempted to be in an area that is not practically reachable in the biaxial film forming process, there is a possibility that the productivity may be significantly reduced or the substance cannot be reached. Or In particular, as long as there is no problem, a higher Young's modulus is better.

<Method for producing oriented laminated polyester film>
The manufacturing method of the oriented polyester film of this invention is demonstrated. First, the polyester production method of the present invention includes, for example, a first reaction in which an aromatic dicarboxylic acid or an ester-forming derivative thereof and an alkylene glycol are esterified or transesterified to synthesize a polyester precursor, and the precursor It consists of a second reaction in which the product is polycondensed, and a method known per se can be adopted.

  The preferable first reaction condition may be performed under normal pressure, but it is preferable to perform the reaction under a pressure of 0.05 MPa to 0.5 MPa because the reaction rate can be easily increased. Moreover, it is preferable to perform the temperature of 1st reaction in the range of 210 to 270 degreeC. By making the reaction pressure within the above range, it is possible to suppress the generation of by-products typified by dialkylene glycol while facilitating the progress of the reaction. At this time, the alkylene glycol component is preferably used in an amount of 1.1 to 6 moles relative to the acid component present in the reaction system in which the first reaction is carried out from the viewpoint of maintaining the reaction rate and the physical properties of the resin. More preferably, it is 2-5 mol times, More preferably, it is 3-5 mol times.

  Further, in order to increase the reaction rate of the first reaction, it is preferable to use a catalyst known per se, for example, a metal compound having a metal component such as Li, Na, K, Mg, Ca, Mn, Co, and Ti. Among these, when performing under pressure, Mn and Ti compounds are preferable from the viewpoint of easy progress of the reaction. In particular, a Mn compound is preferable because it can easily improve the dispersibility of the inorganic particles to be contained.

  The amount of catalyst to be added is preferably in the range of 10 to 150 mmol%, more preferably 20 to 100 mmol%, especially 30, in terms of metal elements, based on the number of moles of all acid components present in the first reaction. It is preferable to be in the range of ˜70 mmol% because the reaction rate can be promoted, the formation of coarse insoluble foreign matters due to the catalyst can be suppressed, and the heat resistance of the resulting copolymerized aromatic polyester can be maintained at a high level. In addition, when adding a titanium compound, it is preferable to add so that it may exist from the time of the esterification reaction start of a 1st reaction, and as above-mentioned, it uses continuously as a polycondensation reaction catalyst. Of course, it may be added in two or more times for the purpose of controlling the polycondensation reaction rate.

Next, the second reaction in which the precursor obtained in the first reaction is polycondensed will be described.
In the present invention, for the purpose of imparting a high degree of thermal stability to the obtained polyester, it is preferable to add a thermal stabilizer composed of a phosphorus compound to the reaction system before the start of the polycondensation reaction in the second reaction. The specific phosphorus compound is not particularly limited as long as it has a phosphorus element in the compound. For example, phosphoric acid, phosphorous acid, phosphoric acid trimethyl ester, phosphoric acid tributyl ester, phosphoric acid triphenyl ester, phosphorus Acid monomethyl ester, phosphoric acid dimethyl ester, phenylphosphonic acid, phenylphosphonic acid dimethyl ester, phenylphosphonic acid diethyl ester, ammonium phosphate, triethylphosphonoacetate, methyldiethylphosphonoacetate, etc., and these phosphorus compounds May use 2 or more types together. The addition timing of the phosphorus compound is preferably performed during the initial stage of the polycondensation reaction, which is the second reaction after the first reaction is substantially completed, and the addition may be performed at one time or two or more times. You may divide into.

  By the way, the polycondensation reaction is preferably performed at a temperature in the range of 270 ° C. to 300 ° C., and the pressure during the polycondensation reaction is preferably performed under a reduced pressure of 50 Pa or less. If the pressure during the polycondensation reaction is higher than the upper limit, the time required for the polycondensation reaction becomes long and it becomes difficult to obtain a copolymerized aromatic polyester having a high degree of polymerization. As the polycondensation catalyst, known metal compounds such as Ti, Al, Sb and Ge can be suitably used. Among these, when Mn—Sb is used, it is preferable because the dispersibility of the particles can be improved.

  As for the method of containing particles, in the state of an alkylene glycol slurry, coarse particles are further reduced by a filter or the like and added in the polymerization step to prepare a particle-containing master polyester having a particle content of 20% by weight. It is preferable to dilute the master polyester with a polyester not containing particles in order to reduce coarse protrusions due to aggregation of particles.

  The polyester thus obtained contains a stabilizer such as an ultraviolet absorber, a lubricant such as an antioxidant, a plasticizer, and a wax, a flame retardant, a release agent, and a nucleating agent as long as the effects of the present invention are not impaired. You may mix | blend as needed. In addition, from the viewpoint of making the background index on the surface on the side where the magnetic layer is formed into a desired range, other thermoplastic polymers that are incompatible with polyester, pigments, fillers, glass fibers, carbon fibers, layered silicates, etc. Is preferably not contained.

  The oriented laminated polyester film of the present invention is prepared, for example, by preparing a polyester polymer for the film layer A, a polyester polymer for the film layer B, and a polyester polymer for the film layer C as necessary, and laminating them in a molten state. Then, the step of co-extrusion from the die into a sheet, the step of cooling and solidifying the obtained sheet-like material to form a laminated unstretched polyester film, and the resulting laminated unstretched polyester film in the film forming direction and the width direction Can be produced by stretching. The temperature in the process of extruding in a molten state is not particularly limited as long as there is no unmelted material and the temperature of the polyester does not excessively deteriorate. For example, the melting point of the polyester (Tm: ° C.) to (Tm + 70) ° C. It is preferable to carry out at temperature.

  Next, for cooling, in order to reduce the thickness unevenness while maintaining the flatness of the obtained laminated unstretched polyester film, a rotating cooling drum installed below the die along the film forming direction is used. It is preferable to cool the sheet-like material in close contact with it. Subsequently, for stretching, the laminated unstretched polyester film is uniaxially (longitudinal or transverse) (polyester glass transition temperature (Tg) −10) ° C. to (Tg + 60) ° C. to 2.5 times or more. The film is preferably stretched at a magnification of 3 times or more, and then preferably stretched at a temperature of Tg to (Tg + 60) ° C. at a temperature of 2.5 times or more, preferably at a magnification of 3 times or more in a direction perpendicular to the stretching direction. preferable. At this time, in order to further improve the flatness of the surface and satisfy the above-described Ra1 and Ra2, it is desirable that the transverse stretching temperature is stretched in the range of (Tg + 25) to (Tg + 60 ° C.). More preferred is (Tg + 30) to (Tg + 60 ° C.), particularly preferred is (Tg + 30) to (Tg + 55 ° C.), and most preferred is a range of (Tg + 35) to (Tg + 55 ° C.). At this time, the transverse stretching temperature is preferably increased stepwise, and any temperature is preferably within the above range. If the transverse stretching temperature is too low with respect to Tg, excessive stretching stress concentrates on the particles, and as a result, the voids around the particles become larger and the protrusions are higher and larger. On the other hand, when mildly stretched in the temperature range described above, the rough surface layer side can be flattened by simultaneously increasing the transverse stretch ratio higher than usual, and as a result, it has a desired height and size. Protrusions can be formed.

  Further, if necessary, the film may be stretched again in the machine direction and / or the transverse direction. In the case of a biaxially oriented film, the stretch ratio when stretched in this way is preferably 9 times or more, more preferably 12 to 35 times, as the area stretch ratio (longitudinal stretch ratio x lateral stretch ratio), 15 ˜30 times is particularly preferable. Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tm-70) to (Tm-10) ° C., and is preferably heat-set at, for example, 180 to 250 ° C. The heat setting time is preferably 0.1 to 60 seconds. Moreover, although the above-mentioned extending | stretching was demonstrated by sequential biaxial stretching, you may use simultaneous biaxial stretching which extends | stretches simultaneously in the vertical direction and a horizontal direction.

  Further, the oriented laminated polyester film of the present invention may be relaxed in the width direction while being heat-set or after heat-set. By relaxing in the width direction in this way, the heat shrinkage rate in the width direction of the film can be maintained in an appropriate range. This relaxation itself can also take place in the longitudinal direction. On the other hand, if relaxation is performed, the Young's modulus of the film is lowered, and a desired Young's modulus cannot be ensured, and tension may not be applied during processing. Therefore, the appropriate relaxation rate strongly depends on the polymer type of the film and the film forming conditions. For example, in the case of forming a polyethylene-2,6-naphthalate film, the relaxation temperature is set to 190 ° C., and the relaxation rate is 0. It is preferable to form a film at 3%.

<High-density magnetic recording>
The oriented laminated polyester film of the present invention is preferably used as a base film of a high-density magnetic recording tape, particularly a digital recording magnetic recording tape. Therefore, the magnetic recording medium using the oriented laminated polyester film of the present invention will be further described.
The magnetic recording medium of the present invention can be produced by forming a magnetic layer on the above-mentioned oriented laminated polyester film. In addition, on the surface of the oriented laminated polyester film of the present invention, in order to improve the adhesion with a magnetic layer, etc., a coating layer having a well-known easy adhesion function, etc., as long as the effects of the present invention are not impaired. May be formed.

  The magnetic layer in the magnetic recording tape of the present invention is prepared by uniformly dispersing iron or acicular fine magnetic powder or barium ferrite in a binder such as polyvinyl chloride or a vinyl chloride / vinyl acetate copolymer. As described above, by using the oriented laminated polyester film of the present invention, a magnetic recording tape excellent in dimensional stability, electromagnetic conversion characteristics and error rate performance can be obtained. it can.

  By the way, as described above, in order to increase the recording density, it is necessary to make the magnetic material finer. Therefore, it becomes difficult to remove the solvent from the coating liquid, and if the workability is maintained, drying or the like is performed at a higher temperature. It was necessary to do in. In addition, it is excellent in electromagnetic conversion characteristics such as output in a short wavelength region, S / N, C / N, etc., particularly when the magnetic layer is applied so that the thickness is 1 μm or less, and further 0.1 to 1 μm. This is preferable from the viewpoint of a coating type magnetic recording tape for high density recording with low dropout and error rate. If necessary, it is also preferable to disperse and coat a nonmagnetic layer containing fine titanium oxide particles or the like in the same organic binder as that of the magnetic layer as the underlayer of the coating type magnetic layer.

Further, a protective layer such as diamond-like carbon (DLC) and a fluorine-containing carboxylic acid-based lubricating layer are sequentially provided on the surface of the magnetic layer as required, and a known backcoat layer is provided on the other surface. May be provided.
The coating type magnetic recording tape thus obtained is extremely useful as a magnetic tape in which a thin film for data use such as an ultra-high density recording medium having a recording capacity exceeding 1.5 TB is essential.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The characteristics of the polyester, the oriented laminated polyester film and the data storage in the present invention were measured and evaluated by the following methods.

(1) Intrinsic viscosity As described above, the intrinsic viscosity of the obtained polyester is measured at o-chlorophenol at 35 ° C. When it is difficult to dissolve uniformly with o-chlorophenol, p-chlorophenol / It was determined by measurement at 35 ° C. using a mixed solvent of 1,1,2,2-tetrachloroethane (40/60 weight ratio).

(2) Particle size and dispersity of particles in the film and number density of particles having a particle size other than 80 nm Polyester on the film surface layer is removed by a plasma low-temperature ashing method (for example, PR-503, manufactured by Yamato Kagaku). And expose the particles. The treatment conditions are such that the polyester is ashed but the particles are not damaged. This is observed with a SEM (scanning electron microscope) at a magnification of about 10,000 times, and an image of the particle (light density produced by the particle) is connected to an image analyzer (for example, QTM900, manufactured by Cambridge Instrument) The observation area is changed, and the area equivalent circle diameter (Di) of at least 5,000 particles is obtained. From this result, a particle size distribution curve of the particles was prepared. The identification of the particle type can be performed using SEM-XMA, quantitative analysis of metal elements by ICP, or the like. Moreover, the average particle diameter of the inorganic particle to add was measured similarly, the particle diameter of each particle | grain was calculated | required, the particle | grains with a particle size of 10-80 nm were extracted, and the number average was made into the average particle diameter.
Further, 5000 particles were counted with the obtained SEM, and particles having a particle size of 10 nm or more were extracted, and the ratio of the particles that were exposed as one spherical particle and did not form an aggregate was defined as the degree of dispersion. Further, among 5000 particles counted, the number of particles having a particle diameter exceeding 80 nm was counted to confirm the number concentration.

(3) Content of particles (3-1) Total content of inorganic particles in each layer When inorganic particles of the oriented laminated polyester film are present, the polyester A layer, the polyester B layer, and the polyester C layer are each scraped off. About 100 g was sampled and burned in a platinum crucible in a furnace at about 1,000 ° C. for 3 hours or more. Next, the combustion product in the crucible was mixed with terephthalic acid (powder) to form a 50 gram tablet. Create a plate. Using this wavelength dispersion type fluorescent X-ray, the count value of each element is converted from the calibration curve for each element, and the total content of inorganic particles in each layer is determined. Based on the particle size distribution described above, The contents of inorganic particles A, B, and C were calculated. The X-ray tube for measuring fluorescent X-rays is preferably a Cr tube and may be measured with an Rh tube. The X-ray output is set to 4 kW, and the spectral crystal is changed for each element to be measured. When there are a plurality of types of inorganic particles of different materials, the content of the inorganic particles of each material is determined by this measurement.

(4) Thickness of film and each polyester layer (4-1) Thickness of film 10 films are stacked so that dust does not enter, the thickness is measured with a dot-type electronic micrometer, and the film thickness per sheet is calculated. To do.

(4-2) Thickness of each polyester layer Using a secondary ion mass spectrometer (SIMS), an element caused by the highest concentration of particles in the film ranging from the surface layer to a depth of 3,000 nm The concentration ratio (M + / C +) of the carbon element in the polyester is defined as the particle concentration, and analysis in the thickness direction is performed from the surface to a depth of 3,000 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. And the particle concentration once reached the maximum value starts to decrease again. Based on this concentration distribution curve, a depth at which the surface layer particle concentration is ½ of the maximum value (this depth is deeper than the depth at which the maximum value is reached) is determined, and this is defined as the surface layer thickness. Then, the thickness of each layer is calculated from the thickness of the film and the thickness of the surface layer.
The conditions are as follows.
(A) Measuring device: secondary ion mass spectrometer (SIMS)
(B) Measurement conditions Primary ion species: O ²⁺
Primary ion acceleration voltage: 12KV
Primary ion current: 200 nA
Raster area: 400 μm
Analysis area: 30% gate
Measuring degree of vacuum: 0.8 Pa (6.0 × 10 ⁻³ Torr)
E-GUN: 0.5KV-3.0A

(5) Young's modulus A film is cut into a sample width of 10 mm and a length of 15 cm, and the distance between chucks is set to 100 mm. The Young's modulus is calculated from the tangent of the rising portion of the obtained load-elongation curve. The main orientation direction can be confirmed by measuring the refractive index in the in-plane direction of the film, and in each of the examples described later, the width direction of the film was the main orientation direction.

(6) Surface roughness (Ra)
Measured using a non-contact type three-dimensional surface roughness meter (manufactured by ZYGO: New View 5022) at a measurement magnification of 25 times and a measurement area of 283 μm × 213 μm (= 0.0603 mm ² ), and incorporated in the roughness meter The center surface average roughness (Ra) was determined by the surface analysis software Metro Pro, which was defined as the surface roughness (Ra). The measurement was performed 10 times while changing the measurement location, and the average value thereof was defined as the center plane average roughness (Ra). Further, the surface roughness of the flat side (the surface of the film layer B or the film layer C) of the laminated polyester film was Ra2, and the surface roughness of the rough side (the surface of the film layer A) was Ra1.

[Example 1]
As the inorganic particles A contained in the film layer A, 10 spherical silica particles (particles A) having an average particle size of 0.01 μm (particle size: relative standard deviation: 10%) subjected to silane coupling treatment to improve dispersibility are used. Polyethylene-2,6-naphthalate pellets (glass transition temperature: 119 ° C., melting point: 263 ° C.) for polyester A layer having an intrinsic viscosity of 0.62 added by weight%, and inorganic particles B contained in the film layer B, The intrinsic viscosity is 0% by adding 0.1% by weight of true spherical silica particles (particles B) having an average particle size of 0.01 μm (particle size: relative standard deviation: 10%), which has also been subjected to silane coupling treatment to improve dispersibility. .62 polyethylene-2,6-naphthalate pellets (glass transition temperature: 122 ° C., melting point: 264 ° C.) for polyester B layer were prepared. Each pellet was dried at 170 ° C. for 6 hours, and then supplied to two extruder hoppers, respectively, at a melting temperature of 310 ° C., and a thickness ratio of A layer: B layer = 4: 96 from the die onto the cooling drum. The sheet was coextruded to obtain a laminated unstretched polyester film.

The laminated unstretched polyester film thus obtained was preheated to 120 ° C. and heated from above with an IR heater so that the film surface temperature was 140 ° C. Stretching in the film direction) was performed. Subsequently, it is supplied into a stenter heated to 155 ° C., and is stretched 5.3 times in the lateral direction (first stage) while being gradually increased to 165 ° C. and 170 ° C., and further heated to 180 ° C. After being fed into the stenter and stretched 1.2 times in the transverse direction, it was heat-fixed with hot air at 215 ° C for 4 seconds, and then relaxed in the width direction at 190 ° C and a relaxation rate of 0.27%. Thus, an oriented laminated polyester film having a thickness of 4.2 μm was obtained. The Young's modulus of the obtained oriented laminated polyester film was 7 GPa in the vertical direction and 10 GPa in the horizontal direction.
Table 1 shows the properties of the obtained oriented laminated polyester film.

[Examples 2-6, Comparative Examples 1-6]
The particle size and concentration of the inorganic particles contained were changed as shown in Table 1, and a film was formed in the same manner as in Example 1 to obtain an oriented laminated polyester film having a thickness of 4.2 μm.
Table 1 shows the properties of the obtained oriented laminated polyester film.
Since Comparative Example 5 is only inorganic particles having a particle size exceeding 80 nm, the average particle size and particle content are shown in Table 1 including those having a particle size exceeding 80 nm.

  The oriented laminated polyester film of the present invention is a coated magnetic recording tape, particularly a data storage base, which has processing characteristics and transportability when thinned, and has excellent electromagnetic conversion characteristics and reduced error rate and dropout. It can use suitably for a film.

Claims (9)

Two layers of film layer B laminated on one side of film layer A, or a three-layer laminated film further having film layer C on the surface of film layer B that is not in contact with film layer A,
The film layer A contains 4 to 20% by weight of spherical inorganic particles A having a particle size of 10 nm to 80 nm, and the degree of dispersion of the inorganic particles A is 80% or more,
In the case of the three-layer laminated film having the film layer C, the film layer B does not contain inorganic particles having a particle size of 10 nm or more, or even if contained, the content of the inorganic particles B having a particle size of 10 nm or more is 0.05 mass. % In the case of a two-layer laminated film having no film layer C, the inorganic particles B having an average particle size of 10 to 80 nm are 0.01 to 0.1 mass based on the mass of the film layer B. % Containing ,
The ratio (tA / tB) of the thickness (tA) of the film layer A to the thickness (tB) of the film layer B is in the range of 0.02 to 0.25, and
The ratio (tA / DA) of the thickness (tA) of the film layer A and the average particle diameter (D) of the inorganic particles A is in the range of 5-25.
The film layer C contains 1 to 20% by weight of inorganic particles C having a particle size of 10 nm to 80 nm, the dispersion degree of the inorganic particles C is 80% or more, and the thickness (tC) of the film layer C and the average particle size of the inorganic particles C The ratio of (D) (tC / DC) is in the range of 0.1-2 ;
The film layers A, B, and C are oriented laminated polyester films characterized in that the proportion of inorganic particles having a particle size of more than 80 nm is 100 or less in all 5000 measured particles . The surface roughness of the film layer A-side surface of the oriented polyester film (Ra1) is 4~10nm range Claim surface roughness of the other surface (Ra2) is in the range of 0.3~1.5nm 1. An oriented laminated polyester film according to 1.   The oriented laminated polyester film according to claim 1, wherein the sum of the Young's modulus (YMD1) in the main orientation direction of the oriented laminated film and the Young's modulus (YMD2) in the direction perpendicular thereto is 15 GPa or more.   The oriented laminated polyester film according to claim 1, wherein the film layer A and the film layer C are made of the same resin composition.   The oriented laminated polyester film according to any one of claims 1 to 4, wherein the polyester comprises ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate as a main repeating unit.   The oriented laminated polyester film according to claim 1, wherein the inorganic particles are spherical particles containing silica as a main component.   The oriented laminated polyester film according to claim 1, wherein the thickness is 2.0 μm or more and 6.0 μm.   A magnetic recording medium comprising the oriented laminated polyester film according to claim 1 and a recording layer formed on the surface on the side different from the film layer A.   9. The recording medium according to claim 8, wherein the recording layer is a coating type magnetic layer.