JP2011204334A - Polyester film and data storage using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film which exhibits excellent electromagnetic conversion characteristics even when used for a base film of a data storage having storage capacity of 0.8 TB or more, and also to provide a data storage using the same.SOLUTION: The polyester film is the base film used for the data storage having storage capacity of 0.8 TB or more, wherein a polyester A layer of the side for forming a magnetic layer contains inert particles a, a ratio of contact of the inert particles a is 0-25%, the number of coarse and large projections originating from the inert particles a is 0-10/100 cmor less, and the polyester film contains a Ti compound in the range of 5 to 100 ppm in terms of an amount of Ti element.

Description

  The present invention relates to a polyester film used as a base film for data storage having a storage capacity of 0.8 TB or more.

In Patent Documents 1 to 5, a specific type of catalyst is used to reduce coarse protrusions, or particles having few coarse particles are used as particles to be contained in the film, and coarse protrusions subjected to such treatment are used. A film with less is proposed.
However, the demand for high-density recording in recent years is tremendous, especially for data storage in which the recording capacity exceeds 0.8 TB per volume, even with the films described in Patent Documents 1 to 5 described above that do not have coarse protrusions. It has become impossible.

JP 2004-114492 A JP 2003-291288 A JP 2002-36311 A JP 2002-363310 A JP 2002-059520 A

  An object of the present invention is to provide a polyester film that can exhibit excellent electromagnetic characteristics even when used as a base film for data storage having a storage capacity of 0.8 TB or more.

In order to solve the above-mentioned problems, the present inventors first removed an external foreign matter (so-called contamination) component, but that was not sufficient. Specifically, even if it is prevented from entering foreign matter or removed by a filter or the like, if it exists in a state where the inert particles to be included as a lubricant are in contact with each other, it depends on the inert particles to be originally formed. Protrusions that are larger in diameter and height than the protrusions, especially in data storage applications with a storage capacity of 0.8 TB or more, can cause large errors, and it is necessary to further control the contact between the inert particles. I found out. And when the protrusions due to the contact between the inert particles are reduced to 10/100 cm ² or less, the electromagnetic conversion is excellent even when used for a data storage base film having a storage capacity of 0.8 TB or more. The inventors have found that the characteristics can be expressed, and have reached the present invention.

Thus, according to the present invention, the polyester film A used for data storage having a storage capacity of 0.8 TB or more, on the side of forming the magnetic layer, contains the inert particles a, and the inert particles a polyester film containing 0 to 25% of the contact ratio of a, 0 to 10 coarse protrusions due to the inert particles a / 100 cm ² or less, and a Ti compound in the range of 5 ppm to 100 ppm in terms of the amount of Ti element Is provided.

  Further, as a preferred embodiment of the present invention, the polyester constituting the polyester A layer further comprises ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate as a main repeating unit, and the polyester film magnetic layer forming side is formed. The surface has a surface roughness (RaA) in the range of 1 to 3 nm, the surface on which the magnetic layer is not formed has a surface roughness (RaB) in the range of 3 to 10 nm, and the average particle size of the inert particles a The diameter is in the range of 0.05 μm or more and 0.2 μm or less, and the content thereof is at least one of the range of 0.01 wt% or more and less than 0.5 wt% based on the weight of the polyester A layer. There is also provided a polyester film comprising:

  Furthermore, as a magnetic recording medium using the above-described polyester film of the present invention, a storage capacity comprising the above-described polyester film of the present invention and a magnetic layer formed on the surface of the polyester A layer side is 0.8 TB or more. In particular, data storage in which a magnetic layer is formed by coating and the recording method is a linear recording method is also provided.

  According to the present invention, since the coarse projections caused by the inactive particles that cause an error when used for the base film of the data storage having a storage capacity of 0.8 TB or more are reduced, the data having excellent electromagnetic conversion characteristics. Storage can be provided.

Hereinafter, the present invention will be described in detail.
In the polyester film of the present invention, the polyester A layer on the surface forming the magnetic layer contains the inert particles a, and the contact ratio of the inert particles a is 0 to 25%, preferably 0 to 15 %, More preferably 0 to 10%. If the contact rate exceeds the upper limit, the height of the protrusion becomes high and an error occurs, and even if no error occurs, the distance between the head and the tape becomes long, and the electromagnetic conversion characteristics deteriorate. On the other hand, the lower limit is not particularly limited and is preferably as small as possible, but is preferably 3% or more from the viewpoint of productivity.

  The contact rate in the present invention is, as explained in the measurement of contact rate described later, when the individual inert particles a are observed, the smallest unit that cannot be further divided is the primary particle, The number of primary particles is counted, among which the boundary between the other inert particles a cannot be confirmed, that is, the number of primary particles in the contact state is counted, and the number of primary particles in the contact state The value divided by the number of particles.

In addition, the polyester A layer on the surface of the polyester film of the present invention on the side on which the magnetic layer is formed has 0 to 10 coarse protrusions due to inert particles a measured by measurement of coarse protrusions described later / 100 cm ^2. It is. Coarse protrusions are preferably 0 to 7 pieces / 100 cm ² , more preferably 0 to 4 pieces / 100 cm ² . When the coarse protrusion exceeds the upper limit, errors increase or electromagnetic conversion characteristics deteriorate. On the other hand, the lower limit is not particularly limited and is preferably as small as possible, but is preferably 1 piece / 100 cm ² or more from the viewpoint of productivity.

  By the way, as long as the polyester A layer in the surface on the side which forms a magnetic layer has the above-mentioned contact rate and the number of coarse protrusions, the manufacturing method in particular is not restrict | limited. However, it is difficult only by selecting inert particles which are difficult to aggregate as described in Patent Documents 1 to 5 mentioned above, or by enhancing dispersibility by melt kneading. Therefore, a preferred method for satisfying the above-described contact rate and the number of coarse protrusions will be described below.

  First, as the inactive particles a, inactive particles that have a sharp particle size distribution and are likely to exist as primary particles are selected. The specific inert particles a are preferably at least one particle selected from the group consisting of organic polymer particles such as silicone resin, crosslinked acrylic resin, crosslinked polyester, crosslinked polystyrene, and spherical silica, and particularly silicone. It is preferably at least one particle selected from the group consisting of a 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.

  A preferable average particle diameter of the inert particles a is 0.05 μm or more and 0.2 μm or less, and the content of the inert particles a is 0.01% by weight or more and 0.5% based on the weight of the polyester A layer. Less than% by weight. When the average particle size is smaller than the lower limit, the inert particles a are easily brought into contact with each other. On the other hand, when the average particle size is larger than the upper limit, the height of the protrusion is increased and the electromagnetic conversion characteristics are likely to be deteriorated. Further, if the content of the inert particles a is less than 0.01% by weight, the slipperiness becomes poor and winding becomes difficult. On the other hand, if the content exceeds the upper limit, the contact between the inert particles a tends to increase. Conversion characteristics are likely to deteriorate. Further, the average particle diameter of the inert particles a is preferably 0.07 to 0.15 μm, and the content is in the range of 0.03 to 0.15% by weight.

  In addition, as a method of adding the inert particles a to the polyester, ethylene is added to the polyester polymerization stage, particularly at an earlier stage such as a transesterification reaction or an esterification reaction, than the inert particles a are added to the polyester by melt kneading. It is preferable to add in the state of a glycol slurry. In that case, it is preferable that a titanium compound is used as a polymerization catalyst for the polyester, and that the ethylene glycol slurry contains a small amount of water.

  This is because when inert particles a are added in the form of an ethylene glycol slurry during polymerization, particles are collected and aggregated around the catalyst by using a Ti compound as a catalyst in the transesterification or esterification reaction. This is to prevent them from doing. The content of the Ti compound is a Ti element, and needs to be 5 to 100 ppm, preferably 7 to 50 ppm, more preferably 10 to 30 ppm based on the weight of the polyester A layer. When the amount of Ti element is less than the lower limit, the polymerization time becomes long and the contact rate becomes high. On the other hand, if the upper limit is exceeded, the amount of catalyst is too large, and contact of the inert particles a around the catalyst tends to occur. Surprisingly, the contact between the inert particles a during the polymerization can be suppressed by adjusting the water content of the ethylene glycol slurry to a specific range. From such a viewpoint, the water content of the preferred ethylene glycol slurry is 0.5 to 10.0 wt%, more preferably 1.5 to 5.0 wt%, based on the weight of the ethylene glycol slurry. The addition method includes a method of adding a predetermined amount of ion-exchanged water after dispersing a lubricant in an ethylene glycol slurry, but other methods can be used as long as a desired moisture content can be achieved.

  In more detail, an example of the manufacturing method of the polyester film of this invention is demonstrated based on a manufacturing process. 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. As described above, in order to reduce foreign substances derived from raw materials, it is preferable to repeat purification of the raw materials such as aromatic dicarboxylic acid or its ester-forming derivative and alkylene glycol to reduce foreign substances. If there are many foreign substances here, foreign substances may not be removed even by filtration described later, and coarse protrusions may increase.

  The raw material thus purified becomes a polyester precursor by the first reaction described above. Here, before starting the second reaction, the polyester precursor is filtered with a first filter having a 95% filtration accuracy of 10 μm or less to break the contact state of the inert particles a or not It is preferable to remove the active particles a. By reducing the amount of inactive particles a in the contact state in this way, it becomes easier to reduce the inactive particles a in the contact state by filtration after the second reaction described later. The filtration with the first filter is not limited to one time. If necessary, the filtration may be repeated further, or the filters may be used in multiple layers. Therefore, the filtration accuracy of the first filter performed between the first reaction and the second reaction is preferably as small as possible from the viewpoint of reducing fly specs, and the 95% filtration accuracy is preferably 8 μm or less, and more preferably 5 μm or less. On the other hand, the lower limit of the 95% filtration accuracy of the first filter is not particularly limited. However, since the replacement cycle becomes shorter as the filter becomes smaller, it is preferably 3 μm or more, and more preferably 4 μm or more from the viewpoint of productivity. . In addition, the first filter has a structure in which metal fiber nonwoven fabrics are laminated, and the porosity of the laminated metal nonwoven fabrics is usually in the range of 40 to 80%. It is preferable because it can withstand. Although it is preferable to reduce the amount of such insoluble coarse foreign matter as much as possible from the raw material stage, it is difficult as described above, and it is simple and extremely effective to remove it by filter filtration after the first reaction.

  Further preferable conditions for the first reaction will be described. The first reaction may be performed under normal pressure, but is preferably performed 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 a 1st reaction in the range of 210 to 270 degreeC. By making the reaction pressure within the above range, the progress of the reaction can be facilitated, the contact of the inert particles a can be more easily suppressed, and the generation of by-products can be suppressed.

Moreover, in order to increase the reaction rate of the first reaction and prevent the contact of the inert particles, a Ti compound is used as a catalyst as described above. Even when the reaction is performed under pressure, the Ti compound is excellent in terms of the ease 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 the catalyst to be added is preferably in the range of the above-mentioned content, and 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 Examples include acid monomethyl ester, phosphoric acid dimethyl ester, phenylphosphonic acid, phenylphosphonic acid dimethyl ester, phenylphosphonic acid diethyl ester, ammonium phosphate, triethylphosphonoacetate, methyldiethylphosphonoacetate, and these phosphorus compounds May use 2 or more types together. The phosphorus compound is preferably added during the initial stage of the polycondensation reaction, which is the second reaction, after the first reaction is substantially completed. 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. When the pressure during the polycondensation reaction is higher than the upper limit, the time required for the polycondensation reaction becomes long, the contact rate of the inert particles a increases, and it becomes difficult to obtain a polyester having a high degree of polymerization. As the polycondensation catalyst, metal compounds such as Ti, Al, Sb and Ge known per se can be preferably used. Among them, the Ti compound added to the first reaction described above can be used continuously depending on the catalyst residue. It is preferable because generation of insoluble coarse foreign matters can be suppressed.

  By the way, as described above, from the viewpoint of reducing the proportion of the inactive particles a in a contact state, a polyester having a desired molecular weight obtained by a polycondensation reaction has a 95% filtration accuracy of 1.5 μm or less in a molten state. It is preferable to filter with the second filter. By such filtration, it is possible to remove or crush the inactive particles a that have not been removed by the filtration performed between the first reaction and the second reaction described above, or are in a contact state generated thereafter. The 95% filtration accuracy of the preferred second filter is 1 μm or less, and the smaller the value, the more preferable in terms of fly specs, but from the viewpoint of productivity, it is preferably 0.2 μm or more, and more preferably 0.3 μm or more. The second filter has a structure in which metal nonwoven fabric media is laminated, and the porosity of the laminated metal nonwoven fabric is usually in the range of 40 to 80%, so that it can withstand the filtration pressure while maintaining the filtration speed. This is preferable.

  In this way, it is possible to obtain a polyester containing inactive particles a with little contact state, but the inactive particles a are used in an amount of 0.02 to 1.0% by weight rather than using the polyester as the polyester of the polyester A layer as it is. In order to further reduce the contact state of the inert particles a, it is preferable that the master polyester is contained in the range of 1 and the master polyester is diluted with a polyester containing no particles.

  The polyester thus obtained is further copolymerized with other copolymerization components known per se within a range not impairing the effects of the present invention, for example, 10 mol% or less, further 5 mol based on the number of moles of repeating units. % May be copolymerized in the range of not more than%, other thermoplastic resins, etc. may be blended in the range of, for example, not more than 20% by weight, further not more than 10% by weight, and stabilizers such as UV absorbers. Antioxidants, plasticizers, lubricants, flame retardants, mold release agents, and nucleating agents may be blended as necessary.

  Next, the polyester containing the inactive particles a having a small contact state obtained in this way is placed so as to be a polyester A layer positioned on the surface on the side where the magnetic layer is to be formed, and in a molten state, the die is formed. Then, the sheet is extruded into a sheet shape, brought into contact with the surface of a rotating cooling drum and cooled to obtain an unstretched film. In addition, since the polyester film of the present invention is used as a base film for data storage, it is preferably a biaxially oriented film obtained by stretching the unstretched film in a film forming direction and a width direction of the film by a method known per se. . In addition, since the filtration of the second filter described above can remove or crush the particles in contact with the inert particles a in a state closer to the final stage just before the film formation, the melt extrusion at the time of film formation It is preferable to use in the process. In addition, as described above, the polyester film of the present invention may be a polyester layer that is such that the polyester A layer on the surface on which the magnetic layer is formed has little contact with the aforementioned inert particles a. It may be a laminated polyester film in which a layer made of other polyester is formed on the surface on the side on which no film is formed.

  Hereinafter, the laminated biaxially oriented polyester film will be described in detail. First, in the extrusion die or before the die (generally, the former is called a multi-manifold method and the latter is called a feed block method), the polyester forming the above-mentioned polyester A layer and the other polyester B are optionally combined. After filtering with a high-precision filter as described above, it is laminated and composited in a molten state to form a laminated structure with a desired thickness ratio, and then in a film form at a temperature from the melting point (Tm) to (Tm + 70) ° C. of the polyester from the die And then co-extruded and rapidly solidified with a cooling roll of 30 to 70 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is 2.5 to 8.0 times in a uniaxial direction (longitudinal direction or transverse direction) at a temperature of (polyester glass transition temperature (Tg) -10) to (Tg + 70) ° C. according to a conventional method. The film is stretched at a magnification of 3.0 to 7.5, and preferably in a direction perpendicular to the stretching direction (when the first-stage stretching is the longitudinal direction, the second-stage stretching is the transverse direction). (Tg) to (Tg + 70) at a temperature of 2.5 to 8.0 times, preferably 3.0 to 7.5 times. Furthermore, you may extend | stretch again in the vertical direction and / or a horizontal direction as needed. That is, it is good to perform 2 steps, 3 steps, 4 steps, or multi-stage stretching. The total draw ratio is usually 9 times or more, preferably 10 to 35 times, and more preferably 12 to 30 times.

  Further, the biaxially oriented film is imparted with excellent dimensional stability by heat-set crystallization at a temperature of (Tg + 70) to (Tm-10) ° C., for example, 180 to 250 ° C. in the case of a polyethylene terephthalate film. The At that time, the heat setting time is preferably 1 to 60 seconds.

  As described above, the polyester film thus obtained has a data storage with less errors because the polyester A layer in which contact between particles is extremely suppressed is arranged on the surface on the side where the magnetic layer is formed. It can be used as a suitable base film.

Next, preferred embodiments of the present invention will be described in detail below.
As the polyester used in the polyester film of the present invention, a polyester known per se 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 preferably exemplified. Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4 6,6 ′-(alkylenedioxy) di-2-naphthoic acid such as 4,4′-diphenyldicarboxylic acid, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, and the diol component Examples thereof 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.

  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 ′-( Examples include those obtained by copolymerizing a trimethylenedioxy) di-2-naphthoic acid component and a 6,6 ′-(butylenedioxy) di-2-naphthoic acid component.

  Among these, the polyester used for the above-described polyester A layer is a polyester mainly composed of ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate, while achieving the strength required for data storage applications. It is preferable because it is easy to suppress contact of the inert particles a.

  In addition, as described above, the polyester film of the present invention only needs to have the polyester A layer disposed on the surface on the side where the magnetic layer is formed, and other polyester on the surface of the polyester A layer where the magnetic layer is not formed. The layer which consists of (henceforth a polyester B layer) may be formed. It is preferable to use the same polyester as the polyester of the polyester A layer as the polyester constituting the polyester B layer, and among the dimensional stability required for data storage with a capacity of 0.8 TB or more, dimensional stability against humidity expansion. The ratio of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component to the total acid component of the acid component of the polyester is 5 mol% or more and less than 25 mol% because it is easy to improve the properties. It is also preferable to use a copolyester. When the ratio of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component to the total acid component in the copolymerized polyester is less than the lower limit, the effect of lowering the humidity expansion coefficient is poor, while the upper limit If it exceeds the upper limit, mechanical properties such as strength tend to decrease.

  In addition, the polyester film in this invention should just be the polyester A layer surface on the side which forms a magnetic layer, (a) The two-layer film in which the polyester B layer was formed in one surface of the polyester A layer, ) A three-layer film in which a polyester A layer is formed on both sides of a polyester B layer, (c) a polyester A layer, a polyester B layer and a polyester C layer (a third polyester layer different from the polyester A layer and the polyester B layer) Any laminated structure, such as a formed three-layer film, (D) a multilayer film in which a polyester A layer and a B layer (also a polyester C layer as necessary) are alternately laminated, may be employed.

  The thickness of the polyester film of the present invention is preferably in the range of 3 to 6 μm from the point of use for data storage. When the polyester film is a laminated film, it is formed on the outermost surface on the side on which the magnetic layer is formed. The thickness of the polyester A layer to be applied is preferably 0.5 μm or more, and more preferably 1 μm or more in order to suppress the influence of protrusions and the like caused by other polyester layers.

  The intrinsic viscosity of the polyester in the present invention is preferably 0.40 dl / g or more, and 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 intrinsic viscosity was measured at 35 ° C. in o-chlorophenol when the polyester was completely dissolved in o-chlorophenol, and P-chlorophenol / 1,1 when it was not completely dissolved. , 2,2-tetrachloroethane (40/60 weight ratio) in a mixed solvent at 35 ° C.

  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 at the time of melting and kneading will be very high, which is likely to cause thermal deterioration, etc. Become.

  By the way, the surface of the polyester film of the present invention on the side where the magnetic layer is formed preferably has a surface roughness (RaA) in the range of 1 to 3 nm. When the surface roughness (RaA) exceeds the upper limit, even if the contact ratio of the inert particles a is suppressed, the electromagnetic conversion characteristics are likely to deteriorate. On the other hand, if the surface roughness (RaA) is less than the lower limit, it is too flat and winding becomes difficult.

  In addition, the polyester film of the present invention can easily improve the transportability and winding property if the magnetic layer side has the same surface roughness, and the surface roughness on the magnetic layer side becomes flatter if the same transportability and winding property. Therefore, the surface roughness on the side where the magnetic layer is not formed is preferably 1 nm or more larger than the surface roughness on the side where the magnetic layer is formed.

  From such a viewpoint, the surface on which the magnetic layer is not formed preferably has a surface roughness (RaB) that is 1 nm or more larger than the surface roughness (RaA) on the magnetic layer side and is in the range of 3 to 10 nm. Preferred RaB is in the range of 4-9 nm, more preferably 5-9 nm. If RaB is less than the lower limit or smaller than RaA, the effect of improving the transportability and winding property is hardly exhibited, and if the upper limit is exceeded, the surface on the magnetic layer side may be roughened by pushing up or transferring.

  In order to provide the above-described surface roughness on the surface on which the magnetic layer is not formed, inert particles may be contained, and the average particle size and content of the inert particles contained therein may be adjusted. The average particle size of the inert particles contained on the surface on the side where the magnetic layer is not preferably formed is preferably 0.2 to 0.5 μm, more preferably 0.2 to 0.4 μm, and the content thereof forms the surface. The range of 0.01 to 0.5% by weight, more preferably 0.02 to 0.4% by weight, based on the weight of the polyester to be used. Furthermore, in addition to the above-mentioned inert particles, the surface on the side where the magnetic layer is not formed has 0.05 to 0.15 μm, more preferably 0.06 to 0.14 μm of inert particles. -0.5% by weight, further containing 0.06-0.4% by weight, that is, by using two or more kinds of inert particles in combination, further improving the transportability and winding property, This is preferable because the surface on the layer side can be easily maintained flat.

  The inert particles contained on the surface on which the magnetic layer is not formed are not particularly limited as long as they can stably exist in the polymer, and those known per se can be adopted. Inert particles similar to the inert particles a described on the surface on the side to be formed are particularly preferable.

  The polyester film of the present invention thus obtained can be used as data storage by forming a magnetic layer on the surface of the polyester A layer side. The magnetic layer is preferably a coating type magnetic layer formed by applying a coating containing a ferromagnetic metal. From the viewpoint of using the running property of the coating type magnetic layer, the data storage is a linear recording method. Is preferred.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the characteristic of the polyester in this invention, the polyester film, and data storage was measured and evaluated by the following method.

(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) Number of coarse protrusions Two polyester films obtained are prepared, and the surface on the side on which the magnetic layer is to be formed and the opposite surface are brought into close contact with each other to eliminate air. And, marking the points corresponding to one or more of the interference fringes (Newton rings) generated when irradiated using NaD rays (wavelength 589 nm), and etching using a plasma reactor to remove the polyester The cause of coarse protrusions is dug out, platinum (Pt) is sputtered, and form observation is performed at 10,000 times using FE-SEM (FE300 manufactured by Shimadzu Corporation). And it was discriminate | determined whether it was a coarse protrusion by the contact of the inert particle a, and the number of the coarse protrusion by the contact of the inert particle a was counted as a coarse protrusion. In addition, about the visual field with an area of 25 cm <2>, the measurement was performed at 10 locations by changing the measurement location, and the average value was used.

(3) Contact rate of inert particles a First, the surface of the obtained polyester film on which the magnetic layer is to be formed is etched using a plasma reactor. The surface is sputtered with platinum (Pt), and 20 fields of view are randomly checked at 5,000 times with FE-SEM (FE-3000 manufactured by Shimadzu Corporation) in the same manner as (2) above. Then, the smallest particles that look like particles are regarded as primary particles, the number of all primary particles is counted, and the particles that cannot see the boundary with other primary particles are counted as primary particles that are in contact with each other. The number is counted, and the number of primary particles in contact with each other divided by the total number of primary particles is calculated as the contact rate. The calculation results were displayed at a rate of 100 minutes.

(4) Center plane average roughness (Ra)
Using a non-contact type three-dimensional surface roughness meter (manufactured by ZYGO: New View 5022), measurement was performed under the conditions of a measurement magnification of 25 times and a measurement area of 283 μm × 213 μm (= 0.0603 mm 2). The center surface average roughness (Ra) was determined by the surface analysis software Metro Pro.

(5) Average particle diameter of inert particles The average particle diameter and relative standard deviation of the inert particles to be added are the average particle diameter obtained from the particle size distribution obtained by the centrifugal sedimentation method according to JIS Z8823-1. It was.

(6) Glass transition point and melting point The glass transition point and the melting point were measured by DSC (TA Instruments Co., Ltd., trade name: Thermal lyst 2920) at a heating rate of 20 ° C / min.

(7) Young's modulus The obtained film was cut out with a sample width of 10 mm and a length of 15 cm, and a universal tensile testing apparatus (trade name: manufactured by Toyo Baldwin, under conditions of 100 mm between chucks, a tensile speed of 10 mm / min, and a chart speed of 500 mm / min. Pull with Tensilon). The Young's modulus is calculated from the tangent of the rising portion of the obtained load-elongation curve.

(8) Creation of data storage (magnetic tape)
A polyester film slit to a width of 1 m is conveyed at a tension of 20 kg / m, and a magnetic coating and a non-magnetic coating of the following composition are applied to the surface of the flat side of the film by an extrusion coater (the upper layer is a magnetic coating and the coating thickness is 0.1 μm and the thickness of the non-magnetic lower layer was 1.0 μm), magnetically oriented, and dried at a drying temperature of 100 ° C. Next, a back coat having the following composition was applied to the opposite surface so that the solid content had a thickness of 0.5 μm, and then a small test calender (steel / nylon roll, 5 steps) at a temperature of 85 ° C. and a linear pressure of 200 kg / cm. Calendar and roll up. The original tape was slit into a 1/2 inch width and incorporated into an LTO case to produce a data storage cartridge having a length of 850 m and a magnetic recording capacity of 0.8 TB.
(Composition of magnetic paint)
・ Ferromagnetic metal powder: 100 parts by weight
-Modified vinyl chloride copolymer: 10 parts by weight
・ Modified polyurethane: 10 parts by weight
・ Polyisocyanate: 5 parts by weight
・ Stearic acid: 1.5 parts by weight
・ Oleic acid: 1 part by weight
・ Carbon black: 1 part by weight
・ Alumina: 10 parts by weight
・ Methyl ethyl ketone: 75 parts by weight
・ Cyclohexanone: 75 parts by weight
・ Toluene: 75 parts by weight
Composition of non-magnetic paint
・ Titanium dioxide fine particles: 100 parts by weight
・ Sleek A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight
・ Nipporan 2304 (Japanese polyurethane polyurethane elastomer): 10 parts by weight Coronate L (Japanese polyurethane polyisocyanate): 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 (backcoat composition)
Carbon black (average particle size 20 nm): 95 parts by weight
Carbon black (average particle size 280 nm): 10 parts by weight
・ Α alumina: 0.1 parts by weight
・ Modified polyurethane: 20 parts by weight
-Modified vinyl chloride copolymer: 30 parts by weight
・ Cyclohexanone: 200 parts by weight
・ Methyl ethyl ketone: 300 parts by weight
・ Toluene: 100 parts by weight

(9) 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. The relative value with the noise N ratio as C / N ratio and Example 1 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

(10) Dropout (DO)
The data storage cartridge created in (8) above was loaded into an IBM LTO4 drive (recording head equipped with an inductive head and playback head equipped with an MR head) to record a data signal of 14 GB and reproduce it. 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

[Reference Example 1] Preparation of Resin 1 100 parts and 70 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester and ethylene glycol, each of which was repeatedly purified by distillation, were prepared and provided with a stirrer, a rectifying column, and a cooler. The reaction vessel was charged and heated to 150 ° C. Thereafter, titanium trimellitic acid as Ti element amount was added so as to be 7 mmol% (14 ppm as Ti element) with respect to the number of moles of all dicarboxylic acid components, and the whole reaction vessel was added with nitrogen under a pressure of 0.25 MPa. The temperature inside the reaction vessel was raised to 240 ° C. by heating. As the reaction progressed, the internal temperature was increased to 250 ° C. with the pressure kept constant. Then, the pressure in the reaction vessel was slowly returned to normal pressure, and trimethyl phosphate was added so that the amount of phosphorus element was 12 mmol% (9 ppm as P element) with respect to the number of moles of all dicarboxylic acid components. Ethylene glycol was driven off to complete the transesterification reaction.
The obtained reaction product was transferred to a polymerization reaction tank. At this time, filtration was performed through a metal fiber filter (first filter) with 95% filtration accuracy of 5 μm during transfer. In the polymerization reaction tank, the polycondensation reaction is carried out while slowly raising the temperature from 250 ° C. while reducing the pressure, and finally the polycondensation is carried out at 290 ° C. and 30 Pa until a predetermined polymerization degree is obtained. Thus, polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.6 dl / g was obtained.

Reference Example 2 Preparation of Resin 2 True spherical silica particles prepared by a water glass method having an average particle size of 0.1 μm and a relative standard deviation of 0.13 were added to ethylene glycol so that the amount was 10% by weight. After adding ion-exchanged water so that the water content becomes 2.5 wt%, it is circulated so as to pass through a metal fiber filter (first filter) with a 95% filtration accuracy of 5 μm. An ethylene glycol slurry having a content of 10% by weight was prepared. Then, after adding the trimellitic acid titanium catalyst to the ethylene glycol slurry at the stage of the transesterification reaction, the content of true spherical silica particles is 0.3% by weight with respect to the weight of the obtained polyester. Except for the addition, the same operation as in Reference Example 1 was repeated to prepare Resin 2.

[Reference Example 3] Preparation of Resin 3 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 60 parts of ethylene glycol, which were repeatedly purified by distillation, were prepared and charged into a reaction vessel equipped with a stirrer, rectification column, and cooler. The temperature was raised to 150 ° C. Thereafter, manganese acetate tetrahydrate was added as Mn element amount so as to be 30 mmol% (68 ppm as Mn element) with respect to the number of moles of all dicarboxylic acid components, and the temperature was gradually raised from 150 ° C. to 240 ° C. The transesterification reaction was carried out. On the way, when the reaction temperature reached 170 ° C., antimony trioxide was used as the amount of Sb element, and 20 mmol% (201 ppm as Sb element) was added to the number of moles of all dicarboxylic acid components, and then reached 220 ° C. 3,5-Dicarboxybenzenesulfonic acid tetrabutylphosphonium salt was added as P element amount so as to be 2 mmol% (2.6 ppm as P element) with respect to the number of moles of all dicarboxylic acid components. Subsequently, a transesterification reaction was performed, and after completion of the transesterification reaction, trimethyl phosphate was used as a P element amount, and 40 mmol% (51 ppm as a P element) was added with respect to the number of moles of all dicarboxylic acid components. The obtained reaction product was transferred to a polymerization reaction tank. At this time, filtration was performed through a metal fiber filter (first filter) with 95% filtration accuracy of 5 μm during transfer. In the polymerization reactor, the polycondensation reaction is carried out while slowly raising the temperature from 250 ° C. and reducing the pressure, and finally the polycondensation is carried out at 290 ° C. and 30 Pa until a predetermined polymerization degree is obtained, and 25 ° C. o-chlorophenol. A polyethylene-2,6-naphthalate (PEN) polymer with an intrinsic viscosity of 0.61 dl / g measured in solution was obtained.

[Reference Example 4] Preparation of Resin 4 True spherical silica particles prepared by an alkoxide method having an average particle size of 0.1 μm and a relative standard deviation of 0.13 were added to ethylene glycol so as to be 10% by weight, It was circulated so as to pass through a metal fiber filter (first filter) having a 95% filtration accuracy of 5 μm to prepare an ethylene glycol slurry having a true spherical silica particle content of 10% by weight. Then, after the addition of manganese acetate / tetrahydrate catalyst to the ethylene glycol slurry at the stage of the transesterification reaction, the content of true spherical silica particles becomes 0.3% by weight with respect to the weight of the obtained polyester. A resin 4 was prepared by repeating the same operation as in Reference Example 3 except that the addition was performed as described above.

[Reference Example 5] Preparation of Resin 5 True spherical silica particles prepared by an alkoxide method having an average particle size of 0.3 μm and a relative standard deviation of 0.13 were added to ethylene glycol so as to be 10% by weight, It was circulated so as to pass through a metal fiber filter (first filter) having a 95% filtration accuracy of 5 μm to prepare an ethylene glycol slurry having a true spherical silica particle content of 10% by weight. Then, after the addition of manganese acetate / tetrahydrate catalyst to the ethylene glycol slurry at the stage of the transesterification reaction, the content of true spherical silica particles is 1.0% by weight with respect to the weight of the polyester obtained. Except for the addition, the same operation as in Reference Example 3 was repeated to prepare Resin 5.

Reference Example 6 Preparation of Resin 6 As the dicarboxylic acid component, except that 20 parts of dimethyl 2,6-naphthalenedicarboxylate and 80 parts of 6,6 ′-(ethylenedioxy) di-2-naphthoic acid are used, The same operation as in Reference Example 1 was repeated to prepare Resin 6. The composition of the resin 6 is such that 29 mol% of the acid component is 2,6-naphthalenedicarboxylic acid component, 71 mol% of the acid component is 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, glycol component 98 mol% was an ethylene glycol component, and 2 mol% of the glycol component was a diethylene glycol component. The melting point was 240 ° C and the glass transition temperature was 117 ° C.

[Example 1]
Resins 1 and 2 are prepared as the polymer for the A layer so as to have the ratio of the inert particles in Table 1, and Resins 1, 2, and 5 are prepared as the polymer for the B layer in the ratio of the inert particles in Table 1. And dried at 170 ° C. for 6 hours. Thus, the dried chips are supplied to the two extruder hoppers at a ratio so as to have the layer thickness configuration shown in Table 1, and melted at a melting temperature of 310 ° C., and the A layer is formed using a multi-manifold coextrusion die. A layer B was laminated on one side of the film to obtain a laminated unstretched film. The polymer for the A layer and the polymer for the B layer were each filtered through a metal fiber filter (second filter) having a 95% filtration accuracy of 1 μm before being supplied to the die.
The laminated unstretched film thus obtained was supplied to the two extruder hoppers in such a ratio that the dry chip had the layer thickness configuration shown in Table 1, and melted at a melting temperature of 310 ° C. The layer B was laminated on one side of the layer A using a multi-manifold coextrusion die to obtain a laminated unstretched film. The polymer for the A layer and the polymer for the B layer were each filtered through a metal fiber filter (second filter) having a 95% filtration accuracy of 1 μm before being supplied to the die.
The laminated unstretched film thus obtained is preheated to 120 ° C., further heated to 130 ° C. between low-speed and high-speed rolls, stretched 4.8 times, and then rapidly cooled to obtain a longitudinally stretched film. Obtained.
Then, it supplied to the stenter and extended | stretched 5.1 times in the horizontal direction at 150 degreeC. The obtained biaxially stretched film was stretched by 10% in the transverse direction while being heat-fixed with hot air at 200 ° C. for 3 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 4.7 μm. The Young's modulus of this film was 6.4 GPa in the vertical direction and 8.5 GPa in the horizontal direction. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Example 2]
The same operation as in Example 1 was repeated except that the ratio of Resin 1 and Resin 2 was changed as the polymer for the A layer. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Example 3]
Titanium trimellitic acid used for Resin 1 of Reference Example 1 and Resin 2 of Reference Example 2 is 2.5 Timol (5 ppm as Ti element) with respect to the number of moles of the total dicarboxylic acid component as the amount of Ti element. To obtain resins 1-1 and 2-1, respectively.
And operation similar to Example 1 except having prepared resin 1-1 and 2-1 so that it might become the ratio of the inert particle of Table 1 instead of resin 1 and resin 2 as a polymer for A layers. Was repeated. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Example 4]
Titanium trimellitic acid used in Resin 1 of Reference Example 1 and Resin 2 of Reference Example 2 is added so that the amount of Ti element is 50 mmol% (100 ppm as Ti element) with respect to the number of moles of all dicarboxylic acid components. Resins 1-2 and 2-2 were obtained, respectively.
And instead of resin 1 and resin 2 as the polymer for layer A, resin 1-2 and 2-2 were prepared so as to have the ratio of inactive particles in Table 1, and as the polymer for layer B, resin In addition to 1, 2 and 5, the ratio of the resin 6 based on the number of moles of the total acid component of the 6,6 ′-(ethylenedioxy) di-2-naphthoic acid component is 15 mol%. In addition, the same operation as in Example 1 was repeated except that the ratio of the resins 1, 2, and 5 was changed so as to be the ratio of the inert particles shown in Table 1. Table 1 shows the properties of the obtained biaxially oriented multilayer laminate film and the magnetic recording tape.

[Example 5]
Resins 1 and 2 are prepared as the polymer for the A layer so as to have the ratio of the inert particles shown in Table 1, and resins 1, 2, 5, and 6 are used as the polymer for the B layer as 6,6 ′-(ethylene Prepared so that the ratio based on the number of moles of all acid components of the dioxy) di-2-naphthoic acid component is 15 mol% and the ratio of the inert particles shown in Table 1, Each was dried at 170 ° C. for 6 hours. Then, after melt extrusion in the same manner as in Example 1, a multilayer feedblock device is used in which the A layer polyester is branched into 25 layers, the B layer polyester is branched into 25 layers, and the A layer and B layer are alternately laminated. Then, it is led to a die while maintaining its laminated state, extruded into a sheet on a cooling drum rotating at a temperature of 50 ° C. in a molten state, and a total of 50 layers in which A layer and B layer are alternately laminated. A stretched multilayer laminated film was prepared. The polymer for layer A and the polymer for layer B are melted and then filtered through a metal fiber filter (second filter) with a 95% filtration accuracy of 1 μm before being supplied to the multilayer feed block. did. The ejection ratio of the A layer and the B layer was 2: 3. Otherwise, the same operation as in Example 1 was repeated. The obtained biaxially oriented multilayer laminated film has a surface layer A layer thickness of 1100 nm, an inner layer A layer thickness of 37 nm, a surface layer B layer thickness of 120 nm, and an inner layer B layer thickness of 120 nm. Table 1 shows the characteristics of the recording tape.

[Comparative Examples 1 and 2]
As in the case of Example 1, except that the resin 3 of Reference Example 3 and the resin 4 of Reference Example 4 were prepared so as to have the ratio of the inert particles shown in Table 1 instead of the resin 1 and the resin 2 as the polymer for the A layer. Repeated operations. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Comparative Example 3]
Resin 4-1 was obtained in the same manner as in Reference Example 4 except that 2.5 wt% of ion-exchanged water was added to a 10% ethylene glycol slurry prepared by the alkoxide method for Resin 4 of Reference Example 4. The same operation as in Comparative Example 1 was repeated except that the resin 4-1 was prepared instead of the resin 4 as the polymer for the A layer. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

  In Table 1, PEN is polyethylene-2,6-naphthalene dicarboxylate, and copolymerization is polyethylene-2 obtained by copolymerization of 15 mol% of 6,6 ′-(ethylenedioxy) di-2-naphthoic acid component. , 6-Naphthalenedicarboxylate.

  The polyester film of the present invention can be suitably used as a base film for data storage having a storage capacity of 0.8 TB or more, since even the minute and coarse protrusions are reduced.

Claims (6)

A base film used for data storage having a storage capacity of 0.8 TB or more,
The polyester A layer on the side forming the magnetic layer contains inert particles a, the contact ratio of the inert particles a is 0 to 25%, and the number of coarse protrusions due to the inert particles a is 0 to 10 / 100 cm < ² > or less, and a polyester film characterized by containing a Ti compound in the range of 5 ppm to 100 ppm in terms of the amount of Ti element.   The polyester film according to claim 1, wherein the polyester constituting the polyester A layer contains ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate as a main repeating unit.   The average particle diameter of the inert particles a is in the range of 0.05 μm or more and 0.20 μm or less, and the content of the inert particles a is 0.01% by weight or more and 0.5% based on the weight of the polyester A layer. The polyester film according to claim 1, which is less than% by weight.   The polyester film according to claim 1, wherein the surface of the polyester A layer has a surface roughness (RaA) of 1 to 3 nm.   A data storage having a storage capacity of 0.8 TB or more comprising the polyester film according to claim 1 and a magnetic layer formed on one surface thereof.   6. The data storage according to claim 5, wherein the magnetic layer is formed by coating and the recording method is a linear recording method.