JPH05212786A - Base film for magnetic recording tape - Google Patents

Abstract

PURPOSE:To improve the electromagnetic conversion properties of magnetic recording tapes with reduced recording distortion and output variation by specifying the values of the properties of a polyethylane-2,6-naphthalate film including the Young's modulus and thermal shrinkage. CONSTITUTION:A base film for magnetic recording tapes is obtained by arranging the properties of a polyethylene-2,6-naphthalate film as: the longitudinal Young's modulus is 850kg/mm<2> or more; the transverse Young's modulus is 550kg/mm<2> or more; the thermal shrinkage after treatment at 100 deg.C for 30min. is 1.0% or less for both longitudinal and transverse directions; the saturated thermal shrinkage at 70 deg.C is 0.1% or less for both longitudinal and transverse directions; the thermal shrinkage after storage at relative humidity of 65% (40 deg.C) for 1hr is 0.01% or less. The magnetic recording tapes have distinguished properties of electromagnetic conversion, without generating image distortion at starting and skipping and skew after storage at around room temperature.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to polyethylene-2,6-
The present invention relates to a base film for a magnetic recording tape made of a naphthalate film, and more particularly to a base film for a magnetic recording tape which is excellent in dimensional stability when left at room temperature.

[0002]

2. Description of the Related Art Biaxially oriented polyethylene terephthalate film has been widely used as a base film for magnetic recording tapes. However, in such a conventional base film for a magnetic recording tape, when used as a magnetic recording tape, the coercive force of magnetic recording is small, and the length of the tape wound around the cassette is lengthened to lengthen the recording and reproducing time. When the thickness of the tape is reduced, the running property and durability of the tape deteriorate.

Therefore, in order to solve the problems of the polyethylene terephthalate film, it has been proposed to use a high Young's modulus biaxially oriented polyethylene-2,6-naphthalate film as a base film for a magnetic recording tape. ing.

It has also been proposed to reduce the heat shrinkage of the film when heat-treated at 70 ° C. for 1 hour under no load in order to prevent the occurrence of skew when the tape is formed.

However, even in a magnetic recording tape using such a polyethylene-2,6-naphthalate film having a high Young's modulus and a low heat shrinkage, the thickness of the base film is thin in order to prolong the recording and reproducing time. Then, when the tape is run, expansion and contraction and deformation of the tape due to tension fluctuations at the start and stop, and distortion of recording due to this occur, and further, the tape end face is stretched and bent, and the running tape is wound around the guide. Such troubles will occur.

Further, since the thickness of the base film becomes thin, relaxation of the molecular orientation occurs in both the vertical and horizontal directions in the magnetic coating process, causing wrinkles on the coated web to deteriorate the electromagnetic characteristics, or the Young's modulus to decrease. There arises a problem that it is lowered and easily deformed. Further, in the process of processing the tape, a skew removing process for further reducing the heat shrinkage rate is required, which causes an increase in manufacturing cost.

Further, when the thickness of the base film is reduced as described above, it is apparent that the magnetic recording tape shrinks even during storage at room temperature, which causes skew and track deviation. It has become clear that this tendency is influenced not only by temperature but also by humidity.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above drawbacks, to enable long-time recording, and to
An object of the present invention is to provide a base film for a magnetic recording tape, which has a small expansion / contraction of a tape due to a change in tension at the time of stop, a distortion in recording and a change in output, and has a good electromagnetic conversion characteristic of the tape.

Another object of the present invention is to prevent wrinkles and Young's modulus from being reduced in the magnetic coating process and to eliminate the need for skew removal in the process of forming the tape. To provide a base film for use.

Further, another object of the present invention is to provide an extremely stable film for magnetic recording tape, which does not cause shrinkage of the tape even when it is stored at a temperature near room temperature and does not cause skew or track deviation. To provide.

[0011]

The present invention comprises polyethylene-2,6-naphthalate and has a Young's modulus in the longitudinal direction of 850 kg / mm ² or more and a Young's modulus in the lateral direction of 550 k.
g / mm ² or more, thermal shrinkage when treated at 100 ° C. for 30 minutes is 1.0% or less in both the longitudinal and lateral directions, and saturated thermal shrinkage at 70 ° C. is 0.1 in both the longitudinal and lateral directions. %, And a shrinkage rate of 0.01% or less when kept at 40 ° C. and 65% relative humidity for 1 hour, the magnetic recording tape base film.

In the present invention, the polyethylene-2,6-naphthalate constituting the film has naphthalene dicarboxylic acid as the main acid component, but may be copolymerized with a small amount of other dicarboxylic acid component, or ethylene glycol. Is the main glycol component, but may be copolymerized with a small amount of another glycol component. Examples of dicarboxylic acids other than naphthalenedicarboxylic acid include terephthalic acid, isophthalic acid, diphenylsulfone dicarboxylic acid, aromatic dicarboxylic acids such as benzophenone dicarboxylic acid, and aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid. And alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid. Examples of glycol components other than ethylene glycol include 1,3-propanediol, 1,4-butanediol,
1,6-hexanediol, neopentyl glycol,
Examples include 1,4-cyclohexanedimethanol and p-xylylene glycol. Further, the polymer may be mixed with additives such as a stabilizer, a colorant and an antistatic agent.

Further, in order to roughen the film surface and improve the slipperiness of the film, various inert solid fine particles may be blended in the polymer.

Such polyethylene-2,6-naphthalate is usually produced by a known method by a melt polymerization method. At this time, additives such as catalysts can be optionally used.

The intrinsic viscosity of polyethylene-2,6-naphthalate is preferably in the range of 0.45 to 0.90.

The base film of the present invention must have a Young's modulus in the longitudinal direction of 850 kg / mm ² or more. As a result, expansion and contraction and permanent deformation 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 recovered promptly. The Young's modulus in the vertical direction is 850
If it is less than kg / mm ² , the stability when used as a tape is also lowered, so that the touch with the reproducing head is bad, the output fluctuation is large, and the sound quality is bad. From these points, the Young's modulus in the longitudinal direction is preferably 900 kg / mm.
² or more, more preferably 950 kg / mm ² or more.

The base film of the present invention must also have a lateral Young's modulus of 550 kg / mm ² or more. This improves the recording / reproducing head and touch. When the Young's modulus is less than 550 kg / mm ² , the touch with the head becomes poor and the output fluctuation is large.
The sound quality also deteriorates. From these points, the Young's modulus in the lateral direction is preferably 600 kg / mm ² or more, more preferably 650 kg / mm ² or more.

The base film of the present invention further comprises
Both the heat shrinkage in the longitudinal direction and the heat shrinkage in the horizontal direction in the free length treatment at 100 ° C. for 30 minutes must be 1.0% or less.
This heat shrinkage rate is preferably 0.5% or less. If this heat shrinkage ratio exceeds 1.0%, shrinkage occurs during magnetic coating processing, which causes wrinkles on the coated web and a large decrease in Young's modulus, which is unsuitable.

Further, the base film of the present invention has a temperature of 70 ° C.
It is necessary that the saturated heat shrinkage ratio in 0.1 is 0.1% or less in both the vertical and horizontal directions. This saturation heat shrinkage ratio is preferably 0.05% or less. This saturation heat shrinkage ratio is 0.
If it exceeds 1%, a skew is generated when formed into a tape, and therefore a skew removing step for reducing heat shrinkage is required in the processing step for the tape, which causes an increase in manufacturing cost.
Here, the saturated heat shrinkage means the heat shrinkage at the time when shrinkage no longer occurs even if heating is continued.

The base film of the present invention is 40
Shrinkage rate when held at ℃, relative humidity 65% for 1 hour,
It should be 0.01% or less. The shrinkage behavior of the film at low temperatures near room temperature depends not only on temperature but also on humidity, and the base film of the present invention is
The shrinkage rate under a specific temperature and humidity is specified. 0.01% shrinkage when held at 40 ° C and 65% relative humidity for 1 hour
When it exceeds, the magnetic recording tape shrinks during normal storage at a temperature near room temperature, causing skew and track deviation.

The base film of the present invention having each of the above characteristics can be manufactured by a known method. For example, polyethylene-2,6-naphthalate is melt extruded at a melting point to a melting point of + 70 ° C. and cooled and solidified to obtain an unstretched film. Then, the unstretched film is stretched in the machine direction and then stretched in the transverse direction, that is, a so-called longitudinal-transverse sequential stretching method, or a transverse-longitudinal sequential stretching method in which the order is reversed and the simultaneous biaxial stretching method, Is stretched by a method of re-stretching these ordinary biaxially stretched films.

The stretching temperature, the stretching ratio and the like are selected from known conditions so as to satisfy the above-mentioned characteristics. The heat setting conditions are also appropriately selected and determined according to the characteristics of the film.

The magnetic recording tape base film of the present invention generally has a specific gravity of 1.340 to 1.353. The base film of the present invention has a thickness of 7 μm particularly when the film is thin for long-term recording and reproduction.
The effect becomes remarkable when it is m or less.

The base film of the present invention is a high-grade grade magnetic recording medium, for example, an ultra-thin film for long-time recording of audio and video, a high-density recording magnetic film, a magnetic recording film for recording and reproducing high-quality images, such as metal. It is also suitable as a vapor-deposited magnetic recording material.

The base film of the present invention may be provided with a magnetic layer on one side or both sides thereof.

The magnetic layer and the method for providing the magnetic layer on the base film are known per se, and the known magnetic layer and the method for providing the magnetic layer can be adopted in the present invention.

For example, when the magnetic layer is provided by a method of applying a magnetic coating on a base film, the ferromagnetic powder used for the magnetic layer is γ-Fe ₂ O ₃ and Co-containing γ-Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , CrO ₂ ,
Known ferromagnetic materials such as barium ferrite can be used.

The binder used together with the magnetic powder is a known thermoplastic resin, thermosetting resin, reactive resin or a mixture thereof. Examples of these resins include vinyl chloride-vinyl acetate copolymers and polyurethane elastomers.

The magnetic paint may further include an abrasive (eg α-Al).
₂ O ₃ etc.), conductive agent (eg carbon black etc.), dispersant (eg lecithin etc.), lubricant (eg n-butyl stearate, lecithin acid etc.), curing agent (eg epoxy resin etc.) and solvent (eg Methyl ethyl ketone, methyl isobutyl ketone, toluene, etc.) and the like.

As the method for forming the magnetic layer, other methods such as wet vacuum deposition by electroless plating or electrolytic plating, and a dry method by sputtering or ion plating can be used.

When a magnetic layer is formed on one side of the film support, the surface of the side where the magnetic layer is not formed is coated with an organic polymer film containing a lubricant to maintain the running property as a tape. May be applied.

The present invention will be further described below based on examples. Various physical property values and characteristics in the present invention are measured and defined as follows.

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

(2) Heat Shrinkage Rate when Treated at 100 ° C. for 30 Minutes The film is cut out into a square shape having a width of 10 mm and a length of 600 mm, and marked points at intervals of 500 mm are attached. The sample is treated in a 100 ° C. air oven for 30 minutes under no tension and then cooled to room temperature. The heat shrinkage rate is calculated from the dimensional change before and after the heat treatment.

(3) Saturation Shrinkage Ratio at 70 ° C. In the same manner as in (2) above, marking marks were put on the tuna-shaped film, left in an air oven at 70 ° C. under no tension, and sampled at regular intervals. Remove and track heat shrinkage. Then, the thermal shrinkage at the time when the thermal shrinkage does not change any more is defined as the saturated shrinkage. In general, a heat shrinkage rate of almost saturation is reached in about 20 hours.

(4) Shrinkage rate when kept at 40 ° C. and relative humidity of 65% for 1 hour In the same manner as in the above (2), the tartar-shaped film was marked with a mark, and air at 40 ° C. and relative humidity of 65% was used. After leaving it in the oven under no tension for 1 hour, it is cooled to room temperature. The shrinkage rate is calculated from the dimensional change before and after the treatment.

(5) Electromagnetic conversion characteristics Using a noise meter manufactured by Shibasoku Co., Ltd., the S / N ratio of the magnetic tape for video is measured. Further, the difference in S / N ratio for the tape of Comparative Example 3 shown in Table 1 is obtained. The VTR used is EV-S700 manufactured by Sony Corporation.

(6) Image Distortion at Start and Stop The first image distortion when the tape running is stopped and restarted is performed by the following evaluations 1, 2, and 3. 1 ... Disturbance is not recognized 2 ... Disturbance is slightly recognized, but there is no problem in practical use 3 ... Disturbance is large and unusable.

(7) Skew The skew characteristic is that the video tape recorded at room temperature (20 ° C.) and normal humidity is left at 30 ° C. and 65% RH for 24 hours, and then reproduced again at room temperature and normal humidity to produce the head. Read the shift amount at the switching point.

[0040]

Examples 1 to 8 and Comparative Examples 1 to 7 Pellets of polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.65 containing 0.15% by weight of spherical silica particles having an average particle size of 0.3 μm, It was dried at 170 ° C. for 4 hours. This pellet
An unstretched film having a thickness such that a biaxially oriented film having a thickness of 5 μm was obtained when melt-extruded by a conventional method, rapidly cooled, and biaxially stretched under the conditions shown in Table 1 and heat set was prepared.

Under the conditions shown in Table 1, this unstretched film was
The film was subjected to a first-stage longitudinal stretching, a transverse stretching and a heat setting, a second-stage longitudinal stretching, a lateral stretching and a heat setting and a relaxation heat treatment to obtain a biaxially oriented film having a thickness of 5 μm.

[0042]

[Table 1]

On the other hand, the composition shown below was placed in a ball mill, kneaded and dispersed for 16 hours, and then 5 parts by weight of an isocyanate compound (Desmodur L manufactured by Bayer Co.) was added to the mixture.
A high speed shear dispersion was performed to obtain a magnetic paint.

Composition of magnetic paint: Needle-like Fe particles 100 parts by weight Vinyl chloride-vinyl acetate copolymer (Eslek 7A manufactured by Sekisui Chemical Co., Ltd.) 15 parts by weight Thermoplastic polyurethane resin 5 parts by weight Chromium oxide 5 parts by weight Carbon black 5 parts by weight Parts 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 coating was applied to the above-mentioned polyethylene-2.
6-Naphthalate film is coated on one side to a coating thickness of 3 μm, then subjected to orientation treatment in a direct current magnetic field of 2500 Gauss, dried by heating at 100 ° C., and supercalendered (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.

Further, a back coat layer coating material having the following composition was applied to a thickness of 1 μm, dried, and further cut into 8 mm,
I got a magnetic tape.

Composition of coating for back coat layer: 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 The characteristics of the obtained film and magnetic tape are shown in Table 2.

[0048]

[Table 2]

As is clear from this table, the magnetic recording tape using the base film of the present invention is excellent in electromagnetic conversion characteristics, has no image disturbance at the time of start and stop, and is stored at a temperature near room temperature. No skew was observed. Of course, the skew removal process was unnecessary.

[0050]

According to the present invention, even if the thickness of the film is thinned for long-term recording and reproduction, the tape is less likely to expand and contract and is deformed, and the electromagnetic conversion characteristics are good. Occurrence, deterioration of electromagnetic characteristics due to decrease in Young's modulus, expansion / contraction of the tape, deformation of the tape, no need for skew removal during tape processing, and even when stored at a temperature near room temperature, skew and track deviation It is possible to provide an extremely stable base film for magnetic recording tape which does not occur.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B29L 7:00 4F C08L 67:00 (72) Inventor Yashiro Saeki 3-37 Oyama, Sagamihara City, Kanagawa Prefecture No.19 inside Sagamihara Research Center, Teijin Limited

Claims (3)

[Claims] 1. A polyethylene 2,6-naphthalate having a Young's modulus in the longitudinal direction of 850 kg / mm ² or more,
Young's modulus in the lateral direction is 550 kg / mm ² or more, 100 ° C
The heat shrinkage when treated for 30 minutes in the longitudinal direction and the transverse direction is 1.0% or less, and the saturation heat shrinkage at 70 ° C is 0.1% or less in the longitudinal direction and the transverse direction, and 40 ° C. , 0.01% shrinkage when kept at 65% relative humidity for 1 hour
A base film for a magnetic recording tape, characterized in that: 2. The specific gravity of the film is 1.340 to 1.35.
The base film for a magnetic recording tape according to claim 1, which is 3. 3. The base film for a magnetic recording tape according to claim 1, wherein the film has a thickness of 7 μm or less.