JP5749504B2 - Laminated polyester film and coated magnetic recording tape using the same - Google Patents

Description

  The present invention relates to a laminated polyester film used for a base film of a coating type magnetic recording tape such as data storage.

  Polyester films have been used as base films for 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 applying a magnetic layer to a polyester film, a uniform magnetic layer cannot be efficiently produced if the winding property and running property of the base film are unstable. It is required that the polyester film contains a lubricant such as inert particles to form protrusions on the surface. These two requirements are contradictory, and in order to satisfy these requirements, Patent Documents 1 to 5 include specific types of catalysts for reducing surface defects and particles included in the film. The use of a film having few coarse particles and a film with few surface defects subjected to such treatment have been proposed. Patent Documents 6 to 7 propose a biaxially oriented polyester film that is excellent in the stability of the original fabric shape and the electromagnetic conversion characteristics as a magnetic recording medium by reducing the undulation component of the base film focusing on the spatial frequency. Has been made.

  However, the demand for high-density recording in recent years is tremendous. In particular, in the coating type magnetic recording tape such as data storage having a recording capacity exceeding 1.5 TB per volume, there is no surface defect in the above-mentioned Patent Documents 1 to 5. Even films that have been found to be less undulated in Patent Documents 6 to 7 have been unable to respond sufficiently.

  In addition, in data storage that performs magnetic recording at high density, the track has become very small, so there are slight thermal and mechanical dimensional changes during tape running and storage, and when data is recorded and read. A difference in temperature and humidity environment has caused a problem that data reproduction is poor. For this reason, coating-type magnetic recording tapes that support high-density recording require high dimensional stability against stresses such as changes in temperature and humidity environments and heat and tape tension. Especially in linear recording data storage, the tape High dimensional stability is required in the width direction.

JP 2004-114492 A JP 2003-291288 A JP 2002-36311 A JP 2002-363310 A JP 2002-059520 A JP 2001-341265 A JP 2004091753 A

  An object of the present invention is to provide a polyester film which can exhibit excellent electromagnetic conversion characteristics and good error rate performance when used as a base film of a coating type magnetic recording tape.

  The present inventors have intensively studied to solve the above-mentioned problems, paying attention to the undulation component generated when the projection on the rough surface layer side protrudes toward the flat layer side, and reducing this, thereby reducing the storage capacity to 1. The inventors have found that excellent electromagnetic conversion characteristics can be exhibited even when used for a base film of a data storage of 5 TB or more, and have reached the present invention.

Thus, according to the present invention, it is a base film used for a coating-type magnetic recording tape, and the surface has an ungeli index of 0.1 μm at a wavelength of 10 μm measured at a measurement magnification of 25 times using a non-contact type three-dimensional surface roughness meter . On the other hand, the surface on the side not forming the magnetic layer has a surface roughness in the range of 4 to 10 nm, and the polyester forming the surface on the side not forming the magnetic layer has a particle size of 0.3 μm or more. The content of the active particles is less than 0.05% by weight, and the inert particles having a particle size of 0.05 μm or more and less than 0.14 μm and the inert particles having a particle size of 0.14 μm or more and less than 0.28 μm are each 0.1%. There is provided a laminated polyester film containing in the range of less than 1 to 0.5% by weight and in the range of 0.01 to 0.3% by weight and having a temperature expansion coefficient in the width direction of -5 to 1 ppm.

Further, as a preferred embodiment of the present invention, the polyester further bets repeating units mainly of ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate, and the Unery index at a wavelength of 10 μm on the surface on which the magnetic layer is not formed is 0.00. in the range of from 15 to 0.35, it polyester to form the surface on the side forming the magnetic layer, the content of the inert particles above a particle size 0.15μm is less than 0.005 wt% The polyester forming the surface on the side on which the magnetic layer is formed contains at least the content of inert particles having a particle size of 0.05 to 0.15 μm in the range of 0.05 to 0.4% by weight. The laminated polyester film comprising any of the above, and the laminated polyester film according to any of the above, and the surface on the side on which the magnetic layer is formed Coating type magnetic recording tape comprising a magnetic layer formed by set are also provided.

  If the polyester film of the present invention is used, it has excellent dimensional stability, and even if it is used for a data storage base film having a storage capacity of 1.5 TB or more, even a minute surface defect that causes an error is reduced. Therefore, it is possible to provide data storage having excellent electromagnetic conversion characteristics.

Hereinafter, the present invention will be described in detail.
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 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 preferred (alkylenedioxy) di-2-naphthoic acid component is in the range of 5 to 40 mol% based on the number of moles of all dicarboxylic acid components.

  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.

  By the way, although the laminated polyester film of the present invention can be produced from the above-mentioned polyester, it maintains a high level of electromagnetic conversion characteristics when data storage is performed while maintaining characteristics such as conveyance and winding within a practically acceptable range. From the viewpoint, the surface on the side on which the magnetic layer is formed needs to have a surface roughness (RaA) of less than 4 nm. Furthermore, since it is easy to make winding property and electromagnetic conversion characteristics compatible with each other to a higher degree, preferable RaA is in the range of 1 to 3.7 nm, and more preferably in the range of 2 to 3.5 nm.

  Further, from the viewpoint of providing the above-mentioned surface roughness (RaA), the polyester forming the surface on which the magnetic layer is formed does not contain or contains inert particles in the laminated polyester film of the present invention. The content of the inert particles having a particle size of more than 0.15 μm is preferably less than 0.005% by weight, and the inert particles having a particle size of 0.05 to 0.15 μm, further 0.07 to 0.14 μm, It is preferable to contain in the range of 0.005 to 0.4% by weight, more preferably 0.007 to 0.3% by weight, particularly 0.01 to 0.2% by weight, based on the weight of the polyester forming the. The term “not containing inert particles” as used herein means that the content of inert particles having a particle size of 0.05 μm or more is less than 0.005% by weight.

In the case where the inert particles are contained, the inert particles to be contained are preferably very few inert particles even if they do not originally contain coarse particles or contain them.
Inert particles that tend to have a sharp particle size distribution and are likely to exist in the form of primary particles include organic polymer particles such as silicone resin, crosslinked acrylic resin, crosslinked polyester, crosslinked polystyrene, and spherical silica. It is preferably at least one kind of particles selected from the group consisting of at least one kind selected from the group consisting of silicone resin, crosslinked polystyrene and spherical silica. Of course, when these inert particles are contained, in order to further eliminate coarse particles, filtration with a filter, treatment of the surface of the inert particles with a dispersant, and strengthening of kneading with an extruder are performed. Is preferred.

  In the laminated polyester film of the present invention, the surface on which the magnetic layer is not formed needs to have a surface roughness (RaB) in the range of 4 to 10 nm, and more preferably in the range of 4 to 7 nm. In order to achieve the RaB described above and the waviness index described later, it is preferable that the inert particles having a particle size of 0.3 μm or more be less than 0.05% by weight based on the weight of the polyester forming the surface. Further, the content of inert particles having a preferable particle diameter of 0.3 μm or more is 0.03% by weight or less.

  Further, the surface on the side where the magnetic layer is not formed has inactive particles having a particle size of 0.05 μm or more and less than 0.14 μm and inactive particles having a particle size of 0.14 μm or more and less than 0.28 μm, 0.1 to 0. It is preferable to contain in less than 5 weight% and 0.01 to 0.3 weight%, and also in less than 0.1 to 0.3 weight% and 0.01 to 0.2 weight%. By using such two or more kinds of inert particles in combination, it is easy to keep the surface on the magnetic layer side flat while further improving the transportability and the winding property.

  The inert particles to be contained on the surface on the side where the magnetic layer is not formed are not particularly limited as long as they can be stably present in the polymer, and those known per se can be adopted, and preferably the above-mentioned magnetic particles are used. Inactive particles similar to those explained on the surface on the layer-forming side, with a sharp particle size distribution, and as inert particles that tend to exist in the form of primary particles, silicone resin, cross-linked acrylic resin, cross-linked It is preferably at least one particle selected from the group consisting of organic polymer particles such as polyester and crosslinked polystyrene and spherical silica, and particularly at least one particle selected from the group consisting of silicone resin, crosslinked polystyrene and spherical silica. It is preferable that The inert particles to be included are preferably those containing no coarse particles or very few inert particles even if they are contained. In order to eliminate coarse particles, filtration with a filter or treatment of the surface of the inert particles with a dispersant is performed. It is preferable to strengthen the kneading in the extruder.

  Below, the manufacturing method of a polyester film 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 Ti compound is preferable because it can be used as a polycondensation reaction catalyst, and the catalyst residue is less precipitated. The titanium compound used in the present invention is preferably an organic titanium compound that is soluble in polyester from the viewpoint of suppressing the generation of insoluble coarse particles due to precipitation of catalyst residues. Particularly preferable examples of the titanium compound include titanium tetraisopropoxide, titanium tetrapropoxide, titanium tetrabutoxide, titanium tetraethoxide, titanium tetraphenoxide, and trimellitic acid titanium.

  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, and among them, it is a catalyst that the titanium compound added at the time of esterification reaction or transesterification reaction is used continuously. This is preferable because generation of insoluble coarse foreign matters due to the residue can be suppressed.

  In addition, for the method of containing inert particles, as an alkylene glycol slurry state, coarse particles are further reduced by a filter or the like, and added in a polymerization step, whereby the particle content is 0.02 to 1.0% by weight. In order to reduce coarse protrusions due to aggregation of inert particles, it is preferable to prepare a particle-containing master polyester and dilute the master polyester with a polyester not containing 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. From the viewpoint of reducing the waviness index on the surface on which the magnetic layer is formed, other thermoplastic polymers, pigments, fillers, glass fibers, carbon fibers, layered silica that are incompatible with polyesters that tend to increase the waviness index. It is preferable not to contain acid salts.

By the way, the Uneri index of the surface which forms the magnetic layer of the laminated polyester film of the present invention is 0.25 or less. Furthermore, it is preferable that it is 0.20 or less. This undele index indicates the undele size (nm) at a wavelength of 10 μm after frequency analysis of the surface roughness in a measurement area of 283 μm × 213 μm (= 0.0603 mm ² ). It is one of the features of the present invention that it has been found that the Uneri index at a wavelength of 10 μm is closely related to the electromagnetic conversion characteristics and the error rate after storage of the tape cartridge.

  In order to make the undele index to be 0.25 or less, it is effective to add the inert particles on the rough surface layer side within the above-mentioned range. It is also extremely effective to stretch the film under the conditions described below.

  Moreover, it is preferable that the Unery index of the surface of the side which does not form the magnetic layer of the laminated polyester film of this invention is 0.15-0.35. Furthermore, it is more preferable that it is 0.20-0.30. When the surface undulation index on the side not forming the magnetic layer exceeds the upper limit, the surface undulation component on the side forming the magnetic layer tends to increase. On the other hand, when the lower limit is not reached, the film transportability is remarkably inferior, and the productivity at the time of film production and in the magnetic coating process tends to decrease. In order to bring the ungeli index of the surface on the side where the magnetic layer is not formed into the above range, the same means as the method of setting the surface undulation component on the side where the magnetic layer is formed within the desired range is effective.

  The laminated polyester film of the present invention is prepared, for example, by preparing a polymer for the polyester A layer and a polymer for the polyester B layer forming the opposite surface, and laminating these in a molten state and coextruding them from a die into a sheet. It can manufacture by extending | stretching the process of making a lamination | stacking unstretched polyester film and the obtained lamination | stacking unstretched polyester film in a film forming direction and the width direction by cooling and solidifying the obtained sheet-like material. 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. Next, for stretching, the laminated unstretched polyester film is uniaxially (longitudinal or transverse) (polyester glass transition temperature (Tg) −10) ° C. to (Tg + 70) ° C. at a temperature of 2.5 times or more. It is preferable that the film is stretched at a magnification of 3 times or more, and then stretched at a temperature of Tg to (Tg + 70) ° C. at a temperature of 2.5 times or more, preferably at a magnification of 3 times or more in the direction orthogonal to the stretching direction. At this time, in order to keep the above-described surface undulation component within a desired range, it is desirable that the transverse stretching temperature is stretched in the range of (Tg + 10) to (Tg + 50 ° C.). At the same time, it is desirable to stretch in the transverse direction at a magnification of 5 times or more. If the transverse stretching temperature is too high or too low with respect to Tg, excessive stretching stress concentrates on the inert particles, and as a result, the voids around the particles become large and the protrusions are high and large. The present invention cannot be achieved. 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. The total draw ratio when stretched in this way is preferably 9 times or more, more preferably 12 to 35 times, and particularly preferably 15 to 30 times as an area draw ratio (longitudinal draw ratio x transverse draw ratio). . Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) to (Tg-10) ° C., for example, preferably heat-set at 180 to 250 ° C. The heat setting time is preferably 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.

  The laminated polyester film of the present invention has a longitudinal Young's modulus of 3 to 10 GPa, more preferably 3.5 to 9 GPa, particularly in order to develop excellent dimensional stability when used as a base film of a high-density magnetic recording medium. It is preferably 4 to 8 GPa. On the other hand, the Young's modulus in the width direction is 4 to 15 GPa, more preferably 5 to 14 GPa, particularly 6 to 13 GPa, most preferably 7 to 11 GPa, from the viewpoint of easily setting the temperature expansion coefficient of the base film to the range described later. It is preferable. If the Young's modulus in the width direction is less than the lower limit, it is difficult to reduce the temperature expansion coefficient when the magnetic recording tape is used. On the other hand, if the upper limit is exceeded, the temperature expansion coefficient when the magnetic recording tape is used becomes excessively small. End up.

  The laminated polyester film of the present invention needs to have a temperature expansion coefficient in the width direction of 1 ppm / ° C. or lower and −5 ppm / ° C. or higher in order to cope with an increase in capacity of the magnetic recording tape. A more preferable temperature expansion coefficient in the width direction of the laminated polyester film has an upper limit of 0.5 pm / ° C. or lower, a lower limit of −4 ppm / ° C. or higher, and further −3 ppm / ° C. or higher. Generally, the temperature expansion coefficient of a magnetic head used in a magnetic recording apparatus is around 7 ppm / ° C. When the temperature expansion coefficient in the width direction of the laminated polyester film exceeds the upper limit, the temperature expansion in the width direction of the magnetic recording tape is too large than the temperature expansion of the magnetic head, so that magnetic data is recorded / reproduced. When the environment changes from a low temperature to a high temperature, the tape expands relative to the magnetic head in the width direction of the tape and easily causes a reproduction failure. Also, if the temperature expansion coefficient in the width direction of the laminated polyester film is smaller than the lower limit, the temperature expansion of the film is too small than the temperature expansion of the magnetic head, so when the temperature changes from low to high, It contracts relative to the magnetic head and tends to cause reproduction failure.

  By the way, if the temperature expansion coefficient in the width direction of the biaxially oriented laminated polyester film is set within the above-described range, the conventional technique increases the surface undulation component on the side on which the magnetic layer is formed, and the undele index exceeds the upper limit. . However, in the present invention, as described above, by adjusting the inert particle composition on the rough surface layer side and the stretching temperature condition to a preferable range, the surface undulation component on the side on which the magnetic layer is formed is reduced and the temperature expansion coefficient in the width direction. Found that both can be achieved.

  The total thickness of the laminated polyester film of the present invention is preferably 2.0 to 8 μm. More preferably, it is 2.5-7 micrometers, More preferably, it is 3-6 micrometers, Most preferably, it is 3.5-5.5 micrometers. When the thickness is smaller than the lower limit, the tape becomes dull and electromagnetic conversion characteristics deteriorate. 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.

  Moreover, the laminated polyester film of the present invention has a thickness of 10 to 90% with respect to the thickness of the laminated polyester film when the polyester layer forming the surface on the flat layer side forming the magnetic layer is an A layer. Further, it is preferably in the range of 20 to 80%, particularly 30 to 70%. When the A layer is less than the lower limit with respect to the total thickness, undulation due to the push-up of particles contained in the polyester layer (B layer) on the rough surface layer side that does not form the magnetic layer occurs, and the electromagnetic conversion characteristics are likely to deteriorate. . On the other hand, by making the thickness of the A layer not more than the upper limit, it is possible to collect a part that does not become a product, which is generated when the laminated polyester film is formed, and use it for the B layer, and to reduce the manufacturing cost and the like. Can do.

  The 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 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-described laminated polyester film. In addition, on the surface of the laminated polyester film of the present invention, in order to improve the adhesiveness with a magnetic layer or the like, a coating layer having a well-known easy-adhesion function, etc., as long as the effect of the present invention is not impaired. It 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 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. .

  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 for data use such as data 8 mm, DDSIV, DLT, S-DLT, LTO and the like.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The characteristics of the polyester, laminated polyester film and 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 of particles in the film
The polyester on the film surface layer is removed by a plasma low temperature ashing method (for example, PR-503, 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 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 inert particle to add was measured similarly, the particle diameter of each particle | grain was calculated | required, and the number average was made into the average particle diameter.

(3) Particle content
(3-1) Total content of particles in each layer
100g of each polyester A layer and polyester B layer are sampled from the laminated biaxially oriented polyester film and sampled. Select a solvent that dissolves the polyester and does not dissolve the particles. Dissolve the sample, and then centrifuge the particles from the polyester. The ratio of particles to the sample weight (% by weight) is defined as the total content of particles in each layer.

(3-2) Total content of inorganic particles in each layer
If inorganic particles are present in the laminated polyester film, the polyester A layer and the polyester B layer are each scraped and sampled for about 100 g, and this is burned in a platinum crucible for about 3 hours in a furnace at about 1,000 ° C. Then, the combustion product in the crucible is mixed with terephthalic acid (powder) to make a 50 gram tablet plate. This plate is converted using a wavelength-dispersed fluorescent X-ray to calculate the count value of each element from a calibration curve for each element that has been prepared in advance, and the total content of inorganic particles in each layer is determined. 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.

(3-3) Content of various particles in each layer (when no inorganic particles are present)
When inorganic particles are not present in the layer, the weight ratio of the particles present in each peak region is calculated from the number ratio of each particle constituting the peak determined by the above (2), the average particle diameter, and the density of the particles, From this and the total content of particles in each layer determined in (3-1) above, the content (% by weight) of particles present in each peak region is determined.
The typical fine particle density is as follows.
Density of crosslinked silicone resin: 1.35 g / cm ³
Cross-linked polystyrene resin density: 1.05 g / cm ³
Cross-linked acrylic resin density: 1.20 g / cm ³
The resin density is further determined by separating the particles centrifuged from the polyester by the method (3-1), and measured by a method described in “Fine Particles Handbook: Asakura Shoten, 1991 edition, page 150”, for example, with a pycnometer. be able to.

(3-4) Content of various particles in each layer (when inorganic particles are present)
When inorganic particles are present in the layer, the layer is determined from the total content of particles in each layer determined in (3-1) and the total content of inorganic particles in each layer determined in (3-2). The content of the organic particles and the inorganic particles in each is calculated, the content of the organic particles is the method (3-3), and the content of the inorganic particles is the method (3-2). (Wt%) is determined.

(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
Measurement degree of vacuum: 0.8 Pa (6.0 × 10 ⁻³ Torr)
E-GUN: 0.5KV-3.0A
In addition, when the most contained particles in the range from the surface layer to a depth of 3000 nm are organic polymer particles, it is difficult to measure by SIMS, so XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy) while etching from the surface. The depth profile similar to the above may be measured by the method) to obtain the surface layer thickness.

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

(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 MetroPro, 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). The surface roughness of the flat side (A layer side) of the laminated polyester film was RaA, and the surface roughness of the rough side (B layer side) was RaB.

(7) Surface undulation index 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 ), Frequency analysis was performed by the surface analysis software Metro Pro built in the roughness meter, and each frequency and the undele intensity were plotted, and the undele intensity at a circumference of 10 μm was obtained as the underi index referred to in the present invention. In addition, the measurement was performed 10 times by changing the measurement location, and the average value thereof was taken as the Uneri index.

(8) Temperature expansion coefficient (αt)
The obtained film was cut into a length of 20 mm and a width of 4 mm so that the width direction of the film would be the measurement direction, set in EXSTAR6000 manufactured by SII, and pretreated at 80 ° C. for 30 minutes in a nitrogen atmosphere (0% RH). Then, the temperature is lowered to room temperature. Thereafter, the temperature is raised from 30 ° C. to 70 ° C. at 2 ° C./min, the sample length at each temperature is measured, and the temperature expansion coefficient (αt) is calculated from the following equation. In addition, the measurement direction is the longitudinal direction of the sample cut out, the measurement was performed 5 times, and the average value was used.
αt = {(L60−L40)} / (L40 × ΔT)} + 0.5
Here, L40 in the above formula is a sample length (mm) at 40 ° C., L60 is a sample length (mm) at 60 ° C., ΔT is 20 (= 60-40) ° C., and 0.5 is quartz. It is a temperature expansion coefficient (ppm / ° C.) of glass.

(9) Coefficient of static friction of film A glass plate fixed on the lower side of two films obtained by superimposing the surface on the polyester A layer side and the surface on the polyester B layer side is placed, and the lower side of the superposed film (glass plate The film in contact with the film) with a low-speed roll (about 10 cm / min), and the detector is fixed to one end of the upper film (the opposite end to the direction of the lower film). Detect the tensile force at the start of. The thread used at that time has a weight of 1 kg and a lower area of 100 cm ² .
The static friction coefficient (μs) was obtained from the following equation.
μs = (Tensile force kg at start) / (Load 1kg)
When the static friction coefficient of the film exceeds 1.0, the slipperiness is extremely lowered, and when the film is rolled up, wrinkles and defects are likely to occur, which is not preferable.

(10) Preparation of magnetic tape A back coat layer paint having the following composition was applied to the surface of the rough surface layer (A layer) of the laminated biaxially oriented polyester film having a width of 1000 mm and a length of 1000 m obtained in each of Examples and Comparative Examples. After coating and drying with a die coater (tension during processing: 20 MPa, temperature: 120 ° C., speed: 200 m / min), a non-magnetic paint or magnetic paint having the following composition on the surface of the flat layer (B layer) side of the film Is applied at the same time with a die coater while changing the film thickness, magnetically oriented and dried. Further, after calendering with a small test calender (steel roll / nylon roll, 5 stages) at a temperature of 70 ° C. and a linear pressure of 200 kg / cm, curing is performed at 70 ° C. for 48 hours. The tape was slit to 12.65 mm and incorporated into a cassette to obtain a magnetic recording tape. The coating amount was adjusted so that the thicknesses of the dried backcoat layer, nonmagnetic layer and magnetic layer were 0.5 μm, 1.2 μm and 0.1 μm, respectively.

<Composition of non-magnetic paint>
-Titanium dioxide fine particles: 100 parts by weight-Esreck A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight-Nipponran 2304 (Nippon Polyurethane Polyurethane Elastomer): 10 parts by weight-Coronate L (Nippon Polyurethane Poly Isocyanate): 5 parts by weight, lecithin: 1 part by weight, methyl ethyl ketone: 75 parts by weight, methyl isobutyl ketone: 75 parts by weight, toluene: 75 parts by weight, carbon black: 2 parts by weight, lauric acid: 1.5 parts by weight <magnetic Composition of paint>
Iron (length: 0.3 μm, needle ratio: 10/1, 1800 oersted): 100 parts by weight Eslek A (vinyl chloride / vinyl acetate copolymer made by Sekisui Chemical: 10 parts by weight) Nipponan 2304 (Nippon Polyurethane Polyurethane elastomer): 10 parts by weight, Coronate L (polyisocyanate made by Nippon Polyurethane): 5 parts by weight, lecithin: 1 part by weight, methyl ethyl ketone: 75 parts by weight, methyl isobutyl ketone: 75 parts by weight, toluene: 75 parts by weight, carbon Black: 2 parts by weight ・ Lauric acid: 1.5 parts by weight <Composition of back coat layer paint:>
Carbon black: 100 parts by weight Thermoplastic polyurethane resin: 60 parts by weight Isocyanate compound: 18 parts by weight (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.)
Silicone oil: 0.5 parts by weight Methyl ethyl ketone: 250 parts by weight Toluene: 50 parts by weight

(11) Electromagnetic conversion characteristics For measuring the electromagnetic conversion characteristics, a 1/2 inch linear system with a fixed head was used. Recording was performed using an electromagnetic induction head (track width 25 μm, gap 0.1 μm), and reproduction was performed using an MR head (8 μm). The relative speed of the head / tape is 10 m / sec, a signal with a recording wavelength of 0.2 μm is recorded, the reproduced signal is analyzed with a spectrum analyzer, the output C of the carrier signal (wavelength 0.2 μm), and the integration over the entire spectrum. A relative value with the noise N ratio as C / N ratio and Example 4 as 0 dB was determined and evaluated according to the following criteria.
◎: +1 dB or more ○: −1 dB or more, less than +1 dB ×: less than −1 dB

(12) Error rate
The original tape produced in the above (10) was slit to a width of 12.65 mm (1/2 inch), and incorporated into an LTO case to produce a data storage cartridge having a magnetic recording tape length of 850 m. This data storage was recorded using an IBM LTO4 drive in an environment of 23 ° C. and 50% RH (recording wavelength 0.55 μm), and then the cartridge was stored in an environment of 50 ° C. and 80% RH for 7 days. After the cartridge was stored at room temperature for one day, the full length was reproduced, and the error rate of the signal at the time of reproduction was measured. The error rate is calculated from the error information (number of error bits) output from the drive by the following formula. The dimensional stability is evaluated according to the following criteria.
Error rate = (number of error bits) / (number of write bits)
A: Error rate is less than 1.0 × 10 ⁻⁶ ○: Error rate is 1.0 × 10 ⁻⁶ or more, less than 1.0 × 10 ⁻⁴ ×: Error rate is 1.0 × 10 ⁻⁴ or more

(13) Dropout (DO)
The data storage cartridge whose error rate was measured in the above (12) was loaded into an IBM LTO4 drive, a data signal was recorded at 14 GB, and it was reproduced. A signal having an amplitude (PP value) of 50% or less with respect to the average signal amplitude was detected as a missing pulse, and four or more consecutive missing pulses were detected as dropouts. In addition, dropout evaluates 1 volume of 850m, converts into the number per 1m, and determines by the following references | standards.
◎: Dropout less than 3 pieces / m ○: Dropout of 3 pieces / m or more, less than 9 pieces / m ×: Dropout of 9 pieces / m or more

[Example 1]
Polyethylene 2, 6 for polyester A layer having an intrinsic viscosity of 0.62, containing 0.10% by weight of true spherical silica particles (particle A) having an average particle size of 0.12 μm as inert particles added to the flat layer side -True spherical silica particles having an average particle diameter of 0.10 wt% and an average particle diameter of 0.05 μm as inert particles to be added to the naphthalate pellets and the rough surface layer side Polyethylene-2,6-naphthalate pellets for polyester B layer containing 0.20% by weight of (Particle B2) and having an intrinsic viscosity of 0.62 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 = 1: 2 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, the sheet is fed into a stenter heated to 135 ° C., stretched 5.3 times in the transverse direction (first stage), then fed into a stenter heated to 160 ° C. and again 1. After stretching twice, it was heat-fixed with hot air at 210 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 5.0 μm. The Young's modulus of the obtained laminated biaxially oriented polyester film was 6.0 GPa in the vertical direction and 9.1 GPa in the horizontal direction. The temperature expansion coefficient (αt) was −2.0 ppm / ° C. Furthermore, the undele index of the polyester A layer was 0.18, and the undelli index of the polyester B layer was 0.25.
Table 1 shows the characteristics of the obtained laminated biaxially oriented polyester film.

[Examples 2-7 and Comparative Examples 1-7]
The same operation as in Example 1 was repeated except that the particles A, particles B1, B2 and transverse stretching conditions to be contained were changed as shown in Table 1.
Table 1 shows the characteristics of the obtained laminated biaxially oriented polyester film.

  ND in Table 1 means that the content of inert particles is 0.001% by weight or less.

  The biaxially oriented laminated polyester film of the present invention has few errors and dropouts when used as a magnetic recording medium, and can exhibit excellent electromagnetic conversion characteristics, so that it can be used for high-density magnetic recording media, particularly digital recording magnetic recording tapes. It can be suitably used as a base film.

Claims (6)

A base film used for a coating type magnetic recording tape,
The surface on which the magnetic layer is to be formed has a surface roughness of less than 4 nm and an ungeli index at a wavelength of 10 μm , measured at a measurement magnification of 25 times using a non-contact type three-dimensional surface roughness meter, of 0.25. And
On the other hand, the surface on the side where the magnetic layer is not formed has a surface roughness in the range of 4 to 10 nm,
The polyester that forms the surface on which the magnetic layer is not formed has a content of inert particles having a particle size of 0.3 μm or more of less than 0.05% by weight, and a particle size of 0.05 μm or more and less than 0.14 μm. Containing inert particles and inert particles having a particle size of 0.14 μm or more and less than 0.28 μm in the range of less than 0.1 to 0.5 wt% and 0.01 to 0.3 wt%, respectively , A laminated polyester film having a temperature expansion coefficient in the range of -5 to 1 ppm.   The laminated polyester film according to claim 1, wherein the polyester comprises ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate as a main repeating unit.   2. The laminated polyester film according to claim 1, wherein the surface on the side where the magnetic layer is not formed has a Unery index at a wavelength of 10 μm within a range of 0.15 to 0.35.   2. The laminated polyester film according to claim 1, wherein the polyester forming the surface on which the magnetic layer is formed has a content of inert particles having a particle size of more than 0.15 μm and less than 0.005 wt%. Polyester, the content of the inert particles having a particle size 0.05~0.15μm is, according to claim 4 which contains in the range of 0.05 to 0.4% by weight to form a surface on which a magnetic layer is formed Laminated polyester film. A coated magnetic recording tape comprising the laminated polyester film according to any one of claims 1 to 5 and a magnetic layer formed by coating on a surface on a side on which the magnetic layer is formed.