JP3545435B2 - Base film for magnetic recording tape - Google Patents

Description

【００４７】
表１から、本発明のベースフイルム及びこれを用いた磁気テープは優れた特性を示すことがわかる。
【００４８】
【発明の効果】
本発明によれば、長時間の記録再生のためにフイルムの厚みを薄くしても、テープの伸縮変形が少なく、電磁変換特性が良好であり、テープの変形、損傷も発生しない極めて安定な磁気記録テープ用のポリエチレン―２，６―ナフタレート系二軸配向ベースフイルムを提供することができる。また、ベースフイルムを磁気テープに加工する際にダイコータによる削れや、カレンダー工程における削れを極めて小さく抑えることができるベースフイルムを提供することがきる。[0001]
[Industrial applications]
The present invention relates to a base film for a magnetic recording tape, and more particularly to a biaxially oriented polyethylene-2,6-naphthalate film useful as a magnetic recording tape for high-density recording, particularly a metal tape.
[0002]
[Prior art]
As a base film for a magnetic recording tape, a biaxially oriented polyethylene terephthalate film has been widely used. However, in such a conventional base film for a magnetic recording tape, when a magnetic recording tape is used, the coercive force of magnetic recording is small, and the length of the tape wound around the cassette is lengthened to increase the recording / reproducing time. When the thickness of the tape is reduced, there arises a problem that the running property and durability of the tape are deteriorated.
[0003]
In order to solve such problems of the polyethylene terephthalate film, many proposals have been made to use a biaxially oriented polyethylene-2,6-naphthalate film having a high Young's modulus as a base film for a magnetic recording tape.
[0004]
However, even with such a magnetic recording tape using a polyethylene-2,6-naphthalate film having a high Young's modulus and a low heat shrinkage, if the thickness of the base film is reduced in order to extend the recording / reproducing time, some The problem of becoming apparent.
[0005]
That is, (1) in the running of the tape, expansion and contraction and deformation of the tape due to the fluctuation of the tension at the time of start and stop, and the distortion of the recording caused by the expansion and contraction of the tape occur. Troubles such as wrapping occur. This problem can be remedied to some extent by properly allocating and controlling the mechanical properties (Young's modulus) and the thermal properties (thermal shrinkage) of the base film in the vertical and horizontal directions. However, as is well known, if the tape is to be made thinner for a longer time, it is necessary to increase the Young's modulus to prevent the tape from deforming. However, there is a problem that the performance as a tape is impaired due to the fact that it does not occur or it takes a long time even if it recovers.
[0006]
Also, (2) voids may be formed between the lubricant and the polymer, or the lubricant and the peeled portion of the polymer may fall off the film due to insufficient affinity with various kinds of lubricant fine particles added for imparting slipperiness. There still remains a problem that the base film is shaved in a die coater or a calendering process during the production of a magnetic tape.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems, to enable long-time recording, to reduce expansion and contraction and deformation of the tape due to tension fluctuation at start / stop, to reduce recording distortion and output fluctuation, and to improve electromagnetic conversion characteristics. An object of the present invention is to provide a good base film for a magnetic recording tape. Another object of the present invention is to provide a base film for a magnetic recording tape, which is extremely unlikely to be scraped by a die coater or a calendering process during processing into a magnetic tape.
[0008]
[Means for Solving the Problems]
The present invention has the following configuration to achieve the above object.
[0009]
What is claimed is: 1. A base film for a magnetic recording tape comprising a biaxially oriented polyester film, wherein the polyester has a crystallization heating value of 16 to 25.5 joules (g) / g, that is, 4,4'- A modified polyethylene-2,6-naphthalate obtained by copolymerizing a diphenyldicarboxylic acid component with 1 to 5 mol% with respect to the total acid component, and having a Young's modulus of 650 kg / mm ² or more in the longitudinal or transverse direction of the film. A base film for a magnetic recording tape.
[0010]
In the present invention, the modified polyethylene-2,6-naphthalate constituting the film has ethylene-2,6-naphthalate as a main repeating unit and a 4,4'-diphenyldicarboxylic acid component in addition to the 2,6-naphthalenedicarboxylic acid component. It is a copolymerized polyester. The copolymerization ratio of the 4,4'-diphenyldicarboxylic acid component is such that the heat of crystallization of the polyester becomes 16 to 25.5 joules (J) / g, preferably 20 to 25.5 J / g. It is preferably from 1 to 5 mol% based on the total acid component, and more preferably from 1 to 3.5 mol% based on the total acid component.
[0011]
As the acid component constituting the modified polyethylene-2,6-naphthalate, a dicarboxylic acid other than 2,6-naphthalenedicarboxylic acid and 4,4'-diphenyldicarboxylic acid can be used in a small proportion. Specifically, aromatic dicarboxylic acids such as 1,5-naphthalenedicarboxylic acid, terephthalic acid, isophthalic acid, diphenylsulfone dicarboxylic acid, and benzophenone dicarboxylic acid; Alicyclic dicarboxylic acids such as dicarboxylic acid, hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid can be exemplified. Further, as the glycol component, a glycol other than ethylene glycol can be used in a small proportion. Specifically, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol and the like can be exemplified. .
[0012]
As described above, the modified polyethylene-2,6-naphthalate in the present invention needs to have a crystallization calorific value in the range of 16 to 25.5 J / g. If the heat of crystallization is more than 25.5 J / g, the voids around the lubricant become large, and the base film is liable to be cut off by a die coater or a calendering process. On the other hand, if the heat of crystallization is smaller than 16 J / g, the voids around the lubricant become small, but it is extremely difficult to carry out stretching orientation, and a film having a high Young's modulus cannot be obtained.
[0013]
Further, the modified polyethylene-2,6-naphthalate in the present invention may contain additives such as a stabilizer, a colorant and an antistatic agent. Further, various kinds of inert solid fine particles can be blended in the polymer in order to roughen the film surface and improve the slipperiness of the film.
[0014]
The inert solid fine particles preferably include (1) silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, etc.); (2) alumina; and (3) at least 30% by weight of a SiO ₂ component. (E.g., amorphous or crystalline clay minerals, aluminosilicates (including calcined and hydrated products), hot asbestos, zircon, fly ash, etc.); (4) Mg, Zn, Zr, and Ti (5) Ca and Ba sulfides; (6) Li, Na and Ca phosphates (including mono- and di-hydrogen salts); (7) Li, Na and K Benzoates; (8) terephthalates of Ca, Ba, Zn, and Mn; (9) titanates of Mg, Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co, and Ni; (10) chromates of Ba and Pb; (11) carbon (for example, (12) glass (eg, glass powder, glass beads, etc.); (13) carbonates of Ca and Mg; (14) fluorite and (15) ZnS. More preferably, silicon dioxide, silicic anhydride, hydrated silicic acid, aluminum oxide, aluminum silicate (including calcined products, hydrates, etc.), monolithium phosphate, trilithium phosphate, sodium phosphate, calcium phosphate, barium sulfate, Examples include titanium oxide, lithium benzoate, double salts of these compounds (including hydrates), glass powder, clay (including kaolin, bentonite, clay, etc.), talc, diatomaceous earth, calcium carbonate, and the like. Particularly preferred are silicon dioxide, titanium oxide and calcium carbonate.
[0015]
The average particle size of the inert solid fine particles is preferably 0.02 to 0.6 μm, and the blending amount is preferably 0.005 to 0.5% by weight.
[0016]
The modified polyethylene-2,6-naphthalate in the present invention can be produced by a known method. For example, a predetermined amount of 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid and ethylene glycol are mixed, and the esterification reaction is directly performed under normal pressure or under pressure, and the melt polycondensation reaction is further performed under reduced pressure. To produce modified polyethylene-2,6-naphthalate. At that time, additives such as a catalyst can be optionally used as needed. The intrinsic viscosity of the modified polyethylene-2,6-naphthalate is preferably in the range of 0.45 to 0.90.
[0017]
The base film of the present invention is a biaxially oriented film composed of the above-mentioned modified polyethylene-2,6-naphthalate. The film preferably has a Young's modulus in the longitudinal direction of 650 kg / mm ² or more. Thus, permanent expansion and contraction of the tape at the time of electronic editing of the tape and at the time of start / stop can be prevented, and the distortion of the tape can be quickly recovered. Further, when the Young's modulus in the vertical direction is less than 650 kg / mm ² , the stiffness of the tape is reduced, so that the touch with the reproducing head is deteriorated, the output fluctuates greatly, and the sound quality is deteriorated. From these points, the Young's modulus in the longitudinal direction is preferably 700 kg / mm ² or more, more preferably 750 kg / mm ² or more.
[0018]
The base film of the present invention preferably has a Young's modulus in the lateral direction of 650 kg / mm ² or more. This improves the touch with the recording / reproducing head. When the Young's modulus is less than 650 kg / mm ² , the touch with the head becomes poor, the output fluctuates greatly, and the sound quality also deteriorates. From these points, the transverse Young's modulus is preferably 700 kg / mm ² or more, and more preferably 750 kg / mm ² or more.
[0019]
A known method can be used as a means for imparting each of the above properties to the base film. For example, a dried modified polyethylene-2,6-naphthalate is melt-extruded at a melting point of + 70 ° C. and solidified by cooling to obtain an unstretched film. Next, the unstretched film is stretched in the machine direction, and then stretched in the transverse direction, a so-called longitudinal and transverse sequential stretching method or a transverse and longitudinal sequential stretching method in which the order is stretched in reverse, a simultaneous biaxial stretching method, and The ordinary biaxially stretched film is stretched by a method of re-stretching or the like. The stretching temperature, stretching ratio, and the like are selected from known conditions that satisfy the above characteristics. The heat setting conditions are also appropriately selected and determined according to the characteristics of the film. In this case, in the longitudinal and transverse sequential stretching method, the stretching ratio and the stretching temperature are 3.5 to 6.0 times in the first longitudinal stretching, the stretching temperature is 130 ° C to 160 ° C, and the second stage is In the stretching in the transverse direction, the stretching ratio is preferably 3.5 to 5.5 times, the stretching temperature is 130 ° C. to 155 ° C., and then heat set at a temperature of 180 ° C. to 250 ° C. under tension or limited shrinkage. In the horizontal and vertical stretching successive stretching method, the film is first stretched in the transverse direction by 3.5 to 5.5 times by a stenter. At this time, the stretching temperature is 130 ° C to 160 ° C. Next, the obtained film is stretched in the longitudinal direction between rolls having different peripheral speeds. At this time, the stretching ratio is 3.5 to 6.0 times, and the temperature is 150 to 170 ° C. Next, it is preferable to heat-set at a temperature of 180 ° C to 250 ° C. In the method of re-stretching the biaxially stretched film, the film is first stretched 1.8 to 2.8 times in the longitudinal direction at 130 ° C. to 150 ° C., and then 3.8 to 5.2 times in the transverse direction by the stenter. The film is stretched at 115 ° C to 130 ° C and heat-set at 150 ° C to 170 ° C under tension or limited shrinkage. Further, the film is stretched again in the longitudinal direction by 1.5 to 3.5 times at 150 ° C. to 190 ° C., and further stretched in the transverse direction by 1.1 to 2.4 times at 170 ° C. to 200 ° C. It is preferable to heat-set at 180 ° C. to 250 ° C. under tension or limited shrinkage. The heat setting time is preferably 5 to 20 seconds.
[0020]
The effect of the base film of the present invention is remarkable when the film thickness is reduced for long-time recording and reproduction. The thickness of this film is preferably 7 μm or less.
[0021]
The base film of the present invention is a high-grade magnetic recording medium, for example, an ultra-thin object for long-time recording such as audio and video, a high-density recording magnetic film, a magnetic recording film for high-quality image recording / reproducing, for example, metal or vapor-deposited magnetic film. It is suitable as a recording material.
[0022]
The base film of the present invention can be provided with a magnetic layer on one or both sides.
[0023]
The magnetic layer and the method of providing the magnetic layer on the base film are known per se, and the present invention can employ a known magnetic layer and a method of providing the same.
[0024]
For example, when the magnetic layer is provided by a method of applying a magnetic paint on the base film, the ferromagnetic powder used for the magnetic layer may be γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , or Co-containing Well-known ferromagnetic materials such as γ-Fe ₃ O ₄ , CrO ₂ , and barium ferrite can be used.
[0025]
Examples of the binder used together with the magnetic powder include known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof. Specific examples of these resins include a vinyl chloride-vinyl acetate copolymer, a polyurethane elastomer and the like.
[0026]
The magnetic paint further includes an abrasive (for example, α-Al ₂ O ₃ ), a conductive agent (for example, carbon black), a dispersant (for example, lecithin), a lubricant (for example, n-butyl stearate, reticic acid, etc.), It may contain a curing agent (eg, an epoxy resin) and a solvent (eg, methyl ethyl ketone, methyl isobutyl ketone, toluene, etc.).
[0027]
Other methods for forming the magnetic layer include wet vacuum deposition using electroless plating or electrolytic plating, and a dry method using sputtering or ion plating.
[0028]
When a magnetic layer is formed on one side of the film support, a coating of an organic polymer containing a lubricant is applied to the surface on the side where the magnetic layer is not formed in order to maintain the running property as a tape. You may.
[0029]
【Example】
Hereinafter, the present invention will be further described with reference to examples.
[0030]
The various physical properties and characteristics in the present invention are measured and defined as follows.
[0031]
(1) A Young's modulus film was cut into a sample having a width of 10 mm and a length of 150 mm, and was pulled with an Instron type universal tensile tester at a pulling speed of 10 mm / min and a chart speed of 500 mm / min with a chuck of 100 mm. The Young's modulus was calculated from the tangent at the rising portion of the obtained load-elongation curve.
[0032]
(2) Heating value for crystallization 10 mg of a biaxially oriented film or a non-stretched film was placed in a sample pan, and heated to 300 ° C. at a rate of 10 ° C./min using an SSC / 580 thermal analyzer manufactured by Seiko Denshi Kogyo. Then, it was kept at this temperature for 10 minutes. Thereafter, the sample was taken out from the DSC, put into ice water, and rapidly cooled. Further, this sample was heated in a DSC at a heating rate of 10 ° C./min to obtain a DSC curve.
[0033]
In this curve, an exothermic peak due to crystallization is generated around 225 ° C. From the area of the exothermic peak, the crystallization exotherm (joule / g) was determined.
[0034]
(3) Electromagnetic conversion characteristics The S / N ratio of the video magnetic tape was measured using a noise meter manufactured by Shibasoku Co., Ltd. Further, the difference in S / N ratio with respect to the tape of Comparative Example 1 shown in Table 1 was determined.
[0035]
The VTR used was an EV-S700 manufactured by Sony Corporation.
[0036]
(4) Durability of Magnetic Tape The vehicle was run for 100 hours while repeatedly starting and stopping running on an EV-S700 manufactured by Sony Corporation, and the running state was checked and the output was measured. When all of the following items were satisfied in this traveling, the traveling performance was determined to be good, and when not, the traveling performance was determined to be poor.
(1) The end of the tape does not break or wakame.
(2) There is no tape squeal during running.
(3) The tape does not tear or break.
[0037]
(5) A single-blade is vertically pressed against a tape obtained by cutting the scrapable film into a tape having a width of 1/2 inch, and the film is further pushed in by 1.5 mm and run for 50 m (running tension: 60 g, running speed: 1 m / sec). ). At this time, the evaluation was made by the adhesion width of the shavings on the film surface adhering to the single blade.
[0038]
(6) Void area ratio The film surface is ion-etched to expose the lubricant in the film, aluminum is vacuum-deposited uniformly to a thickness of 400 to 500 angstroms or less, and 3500 to 5000 times with a normal scanning electron microscope. The surface of the sample was observed, and the area of voids around the lubricant was measured with an image analyzer Luzex. The area of the lubricant was determined in the same manner. Then, the area ratio of voids was determined by dividing the area of the lubricant.
[0039]
The ion etching was performed, for example, using a JFC-1100 type ion sputtering apparatus manufactured by JEOL Ltd. at 500 V, 12.5 mA for 15 minutes. The degree of vacuum was about 10 ⁻³ Torr. Particles were measured for particles as large as about 0.3 μm or more.
[0040]
Examples 1 and 2 and Comparative Example 1
An intrinsic viscosity of 0.62 dl / g containing 0.2% by weight of silica fine particles having an average particle size of 0.1 μm and 0.014% by weight of calcium carbonate fine particles having an average particle size of 0.6 μm (using orthochlorophenol as a solvent, Polyethylene-2,6-naphthalate (a value measured at 25 ° C.) (homopolymer) was prepared by a conventional method.
[0041]
Further, modified polyethylene-2,6-naphthalate was prepared by copolymerizing 4,4'-diphenyldicarboxylic acid in the amount shown in Table 1 as a copolymer component. The lubricant concentration, intrinsic viscosity, and the like were adjusted so as to be equivalent to the above-mentioned homopolymer.
[0042]
Each of the obtained polymer pellets was dried at 170 ° C., melt-extruded at 300 ° C., and quenched and solidified on a casting drum maintained at 40 ° C. to obtain an unstretched film.
[0043]
This unstretched film is stretched 4.85 times in the machine direction at a temperature of 125 ° C. between two rolls having a speed difference, further stretched 5.15 times in a transverse direction by a tenter, and then heat-treated at 215 ° C. for 10 seconds. Did. Thus, a biaxially oriented polyester film having a thickness of 7 μm was wound.
[0044]
On the other hand, the composition shown below was put into a ball mill, kneaded and dispersed for 16 hours, and then 5 parts by weight of an isocyanate compound (Desmodur L manufactured by Bayer AG) was added, followed by high-speed shearing and dispersion for 1 hour to obtain a magnetic paint.
Composition of magnetic paint:
Acicular Fe particles 100 parts by weight Vinyl chloride-vinyl acetate copolymer (Slec 7A manufactured by Sekisui Chemical)
15 parts by weight thermoplastic polyurethane resin 5 parts by weight chromium oxide 5 parts by weight carbon black 5 parts by weight lecithin 2 parts by weight fatty acid ester 1 part by weight toluene 50 parts by weight methyl ethyl ketone 50 parts by weight cyclohexanone 50 parts by weight This magnetic paint is biaxially oriented as described above. One side of the polyester film is coated to a coating thickness of 3 μm, then subjected to an orientation treatment in a DC magnetic field of 2500 gauss, dried by heating at 100 ° C., and then subjected to a super calender treatment (linear pressure 200 kg / cm, temperature 80 ° C.). And wound up. The wound roll was left in an oven at 55 ° C. for 3 days.
[0045]
Further, a backcoat layer paint having the following composition was applied to a thickness of 1 μm on the surface of the film on which the magnetic paint was not applied, dried, and further cut by 8 mm to obtain a magnetic tape.
Backcoat layer paint composition:
Carbon black 100 parts by weight Thermoplastic polyurethane resin 60 parts by weight Isocyanate compound (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) 18 parts by weight Silicone oil 0.5 parts by weight Methyl ethyl ketone 250 parts by weight Toluene 50 parts by weight Properties of the obtained film and magnetic tape Are shown in Table 1.
[0046]
[Table 1]

[0047]
Table 1 shows that the base film of the present invention and the magnetic tape using the same have excellent characteristics.
[0048]
【The invention's effect】
According to the present invention, even when the thickness of the film is reduced for long-term recording and reproduction, the tape has little expansion and contraction deformation, has good electromagnetic conversion characteristics, and has extremely stable magnetic properties without tape deformation and damage. A polyethylene-2,6-naphthalate-based biaxially oriented base film for a recording tape can be provided. Further, it is possible to provide a base film capable of minimizing abrasion by a die coater and an abrasion in a calendering step when processing the base film into a magnetic tape.

Claims (2)

What is claimed is : 1. A base film for a magnetic recording tape comprising a biaxially oriented polyester film, wherein the polyester is a modified polyethylene obtained by copolymerizing a 4,4'-diphenyldicarboxylic acid component with 1 to 5 mol% with respect to all acid components. A base film for a magnetic recording tape, which is 2,6-naphthalate and has a Young's modulus of 650 kg / mm ² or more in the vertical or horizontal direction of the film. ^{2. The} base film for a magnetic recording tape according to claim 1, wherein the Young's modulus in the longitudinal direction and the transverse direction of the film are each 650 kg / mm ² or more.