JPH05261808A - Manufacture of biaxially oriented polyethylene-2, 6-naphthalate film - Google Patents

Abstract

PURPOSE:To manufacture stably a biaxially oriented polyester-2, 6-naphthalate film with high Young's modulus, thin thickness and small unevenness in its thickness, without rupture. CONSTITUTION:The manufacture of a biaxially oriented polyethylene-2, 6- naphthalate film is such that a substantially non-oriented polyethylene-2, 6- naphphthalate film is stretched in the longitudinal direction, and the difference (nM-nT) between the refractive index in the longitudinal direction (nM) and the refractive index in the transverse direction (nT) is made 0.05-0.18, and next, it is stretched in the transverse direction and then is heat-fixed intermediately at 150-170 deg.C under tension and transversely limited contraction, in order to allow the difference (nM-nM) between the refractive index (nM) in the transverse direction (NT) and the refractive index (nM) in the longitudinal direction to be 0.3-0.10, and further to make it extend 1.8-2.4 times in the longitudinal direction. After that, it is extended 1.4-2.4 times in the transverse direction at 170--190 deg.C, and then, it is thermally fixed at 190-250 deg.C.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a biaxially oriented polyethylene
More specifically, it relates to a method for producing a 2,6-naphthalate film, and more specifically, a biaxially oriented polyethylene having a high Young's modulus and less deformation and damage of the tape even though the thickness is small and the thickness is thin. The present invention relates to a method for producing a naphthalate film without cutting.

[0002]

2. Description of the Related Art As a magnetic recording tape, a biaxially oriented polyethylene terephthalate film having a magnetic layer formed on its surface has been widely used. However, in such a conventional magnetic recording tape, the coercive force of the magnetic recording is small, and if the tape is thinned in order to lengthen the length of the tape wound around the cassette and to lengthen the recording and reproducing time, However, there is a problem in that the running performance and durability are deteriorated.

Therefore, in order to solve the problems of the magnetic recording tape using such a polyethylene terephthalate film, a biaxially oriented polyethylene-2,6-naphthalate film having a high Young's modulus and a low heat shrinkage is used as a support. The magnetic recording tape used has been proposed.

However, in recent years, the diversification of magnetic recording tapes has been remarkable, and various high-performance magnetic recording tapes have been developed. Further, since they are often used under severe conditions, The advent of thinner magnetic recording tape films with high Young's modulus is desired.

Generally, in order to obtain a film having a high Young's modulus, a high-magnification multi-stage drawing is carried out, but the film is easily broken during the drawing, and it is difficult to produce the film in a stable state. This tendency becomes more prominent when attempting to produce thin films of.

Further, when such high-stretching is carried out, the thickness unevenness of the obtained film becomes large, and the magnetic recording tape using this film also has a problem that the fluctuation of the electromagnetic characteristics becomes large.

Therefore, a film for a magnetic recording tape having a high Young's modulus, a thin thickness and a small thickness unevenness has not been obtained so far.

[0008]

The object of the present invention is to obtain a high Young's modulus, a thin thickness, and
Another object of the present invention is to provide a method for stably producing a biaxially oriented polyethylene-2,6-naphthalate film having a small thickness unevenness without breaking the film.

[0009]

According to the present invention, a substantially non-oriented polyethylene-2,6-naphthalate film is stretched in the longitudinal direction to obtain a longitudinal refractive index (nM) and a lateral refractive index. The difference (nM-nT) of (nT) is 0.05 to 0.18.
Then, after being stretched in the transverse direction, it is subjected to intermediate heat fixation at a temperature of 150 to 170 ° C. under tension or under lateral transverse contraction to obtain a transverse direction refractive index (nT) and a longitudinal direction refractive index (nM).
(NT-nM) of 0.03 to 0.10, and then again stretched in the machine direction at 150 to 190 ° C by 1.8 to 2.4 times, and then in the transverse direction at 170 to 190 ° C again at 1 to 1. .4 ~
Biaxially oriented polyethylene-2,6-, characterized in that it is stretched 2.4 times and then heat-set at 190-250 ° C.
This is a method for producing a naphthalate film.

In the present invention, the polyethylene-2,6-naphthalate constituting the film has naphthalene dicarboxylic acid as the main acid component, but a small amount of other dicarboxylic acid component may be copolymerized, and ethylene glycol as the main component. It is a polymer that has a 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 surface of the film 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.

Biaxially oriented polyethylene of the present invention-2,6-
The naphthalate film has a Young's modulus in the longitudinal direction (EM) of 650 kg / mm ² or more and a Young's modulus in the transverse direction (ET) of 900 kg / m ² or more, and the difference between them (ET-EM).
Is preferably 200 kg / mm ² or more.

Young's modulus (EM) in the longitudinal direction is 650 kg /
If it is less than mm ² , the magnetic recording tape is not suitable because the tape is stretched and deformed when a strong stress is applied to the tape. A more preferable Young's modulus (EM) in the longitudinal direction is 700 kg / mm ² or more.

The Young's modulus (ET) in the lateral direction is 900.
Less than kg / mm ² , or Young's modulus in the longitudinal direction (EM)
And the Young's modulus (ET) in the lateral direction (ET-EM) is 2
If it is less than 00 kg / mm ² , if the tape is repeatedly run under special conditions or harsh conditions, the edges of the tape will elongate and deform into a seaweed shape. The end of the tape may be bent and the characteristics of the tape may be impaired. Further, the contact of the tape with the magnetic head becomes defective, and the electromagnetic output is reduced. A more preferable value of Young's modulus (ET) in the lateral direction is 950 kg / mm ² or more, and a more preferable value of ET-EM is 250 kg / mm ² or more.

Further, the biaxially oriented polyethylene-2,6-naphthalate film of the present invention has a thickness variation of 15%.
Is preferred. If the thickness unevenness exceeds 15%, the fluctuation of the electromagnetic characteristics of the tape increases, which is not suitable.
Thickness unevenness is preferably 10% or less, more preferably 5%
It is below.

Biaxially oriented polyethylene in the present invention
The 2,6-naphthalate film preferably has a thickness of 12 μm or less, more preferably 7 μm or less in order to increase the length of the tape stored in the cassette and increase the recording / reproducing time.

The biaxially oriented polyethylene-2,6-naphthalate film of the present invention has a surface roughness Ra of 5 to 1 in order to obtain good electromagnetic characteristics and roll-up properties.
It is preferably 0 nm.

Biaxially oriented polyethylene-2 as described above
In the present invention, the 6-naphthalate film is produced by the following method.

That is, the polyethylene-2,6-naphthalate is melt-extruded at a melting point to a melting point of + 70 ° C. and cooled and solidified to obtain a substantially non-oriented polyethylene-2,6-naphthalate film. Next, this substantially non-oriented polyethylene-2,6-naphthalate film was treated with the difference (nM) between the longitudinal refractive index (nM) and the lateral refractive index (nT).
-NT) is 0.05 to 0.18, and is stretched in the machine direction. When nM-nT is outside this range, the desired Young's modulus cannot be obtained, the thickness unevenness of the film becomes large, and the film is frequently cut during the final stretching in the lateral direction. n
To keep M-nT within the above range, it is usually Tg + 10 ° C.
It may be stretched 1.5 to 3.0 times in the machine direction at a temperature of Tg + 50 ° C (where Tg is the glass transition point of polyethylene-2,6-naphthalate).

After being stretched in the longitudinal direction as described above, the difference (nT-) between the refractive index (nT) in the lateral direction and the refractive index (nM) in the longitudinal direction.
It is stretched in the transverse direction so that the nM) becomes 0.03 to 0.10. Further, intermediate heat setting is performed at 150 to 170 ° C.
When nT-nM is out of this range, the desired Young's modulus cannot be obtained, the thickness unevenness of the film becomes large, and the film is frequently cut during the final stretching in the transverse direction. In order to make nT-nM within the above range, it is usually stretched at a temperature of 115 to 130 ° C by a factor of 3.7 to 5.2 in the transverse direction, and further 150 to 170 ° C.
It should be heat fixed with.

After this, the film was stretched again in the longitudinal direction at 150 to 190 ° C. by a factor of 1.8 to 2.4, and then in the transverse direction again to 170 to
It is stretched 1.4 to 2.4 times at 190 ° C.

By stretching under these conditions, the polyethylene-2,6-naphthalate film having a high Young's modulus and small thickness unevenness specified in the present invention can be manufactured with good productivity without cutting.

Next, heat setting is performed at 190 to 250 ° C. Heat fixation is usually performed under a fixed length, but if necessary,
It may be performed under restricted contraction or elongation. When heat setting is performed under limited shrinkage, it is necessary to consider the shrinkage rate so that the Young's modulus does not fall below the range specified in the present invention.

Biaxially oriented polyethylene in the present invention
2,6-naphthalate film is a high-grade magnetic recording medium, for example, ultra-thin film for long-time recording of audio and video, high-density recording magnetic film, magnetic recording film for high-quality image recording / reproducing, such as metal or It is suitable as a vapor-deposited magnetic recording material. Particularly, it is suitable for use in a magnetic recording film having a particular shape and used under severe conditions.

Biaxially oriented polyethylene in the present invention
The 2,6-naphthalate film can 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 the base film, the ferromagnetic powder used for the magnetic layer is γ-Fe ₂ O ₃ and Co-containing γ-Fe ₂ O _3. , Co-containing γ-Fe ₃ O ₄ , CrO
_2. Known ferromagnetic materials such as barium ferrite can be used.

Examples of the binder used together with the magnetic powder include known thermoplastic resins, thermosetting resins, reactive resins and mixtures 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, letisic 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, an organic polymer coating film containing a lubricant is added to the surface on the side where the magnetic layer is not formed in order to maintain the running property as a tape. May be applied.

[0034]

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 having a width of 10 mm and a length of 15 cm, and the distance between chucks is 100 mm, and the film is pulled at a pulling speed of 10 mm / min and a chart speed of 500 mm / min using an Instron type universal tensile tester. Young's modulus is calculated from the close battle at the rising part of the obtained load-elongation curve.

(2) Thickness unevenness A sample having a length of 2 m is taken from the film wound in a roll shape, and the thickness is continuously measured over the entire length in the machine direction and the transverse direction by using a film continuous thickness measuring device manufactured by Anritsu Corporation. Measured and recorded on the chart. The average value (x), the maximum value (Max) and the minimum value (Min) of the thickness are obtained from the measurement chart, and the thickness unevenness is calculated by the following formula.

[0037]

[Equation 1]

(3) Refractive index: Measured using an Abbe type refractometer manufactured by Atago Co., Ltd.
If the refractive index is too large to be measured with this refractometer, it was measured with a microwave molecular orientation meter MOA-200IA manufactured by Kanzaki Paper Co., Ltd. and prepared in advance between the measured value with an Abbe type refractometer. The optical refractive index is determined according to the calibration curve.

(4) S / N ratio (electromagnetic output fluctuation) Sony Corporation video tape recorder EV-S700
The S / N ratio of the magnetic recording tape recorded in 1. is measured using a noise meter manufactured by Shibasoku Co., Ltd.

(5) Running property of magnetic recording tape A tape is set on the above video tape recorder EV-S700, and running is repeated at a high speed of 26 m / min for 300 hours while repeating running start and stop, and the running state is checked. The state of the tape at this time is judged in three stages as follows. ○: The end of the tape is not broken or wakame. Δ: Some bending or wrinkling of the tape edge occurs. X: The edge of the tape is significantly bent or wrinkled.

[0041]

Examples 1 to 10 and Comparative Examples 1 to 7 Average particle size 0.1 μ
0.3% by weight of spherical silica fine particles having an average particle size of 0.
Pellets of polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.62 and containing 0.02% by weight of calcium carbonate fine particles of 6 μm were dried at 170 ° C. for 4 hours.
The pellets were melt-extruded by a conventional method and rapidly cooled to prepare a substantially non-oriented film.

This non-oriented film was subjected to the conditions shown in Table 1 in order of the first stage longitudinal stretching, the first stage transverse stretching, intermediate heat setting, the second stage longitudinal stretching, the second stage transverse stretching and It was subjected to tension heat fixation to obtain a biaxially oriented film having a thickness of 5 μm.

[0043]

[Table 1]

[0044]

[Table 2]

The properties of the obtained film and the number of times the film was cut per hour during stretching were as shown in Table 3.

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 thereto.
A high-speed shearing dispersion was carried out for a time to obtain a magnetic paint.

[0047] This magnetic paint was applied to one side of the polyethylene-2,6-naphthalate film described above so as to have a coating thickness of 3 μm, then subjected to orientation treatment in a direct current magnetic field of 2500 Gauss, heated and dried at 100 ° C. A calendar treatment (linear pressure 200 kg / cm, temperature 80 ° C.) was performed and the film was wound. 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 to obtain 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 S / N ratio and tape running property of the obtained magnetic recording tape were measured. The results are shown in Table 3.

[0050]

[Table 3]

[0051]

Examples 11 to 19 and Comparative Examples 8 to 15 In Example 2, the second stage drawing conditions were changed as shown in Table 4.
Table 4 shows the Young's modulus and thickness unevenness of the obtained film, and the number of times the film was cut during stretching.

[0052]

[Table 4]

As is clear from these results, in the magnetic recording tape using the biaxially oriented polyethylene-2,6-naphthalate film produced by the method of the present invention, S /
The N ratio was low, the electromagnetic output fluctuation was small, the running property was excellent, and the tape was not deformed or damaged.

Further, according to the production method of the present invention, a biaxially oriented polyethylene having a high Young's modulus and being thin and having less thickness unevenness
The 2,6-naphthalate film could be stably manufactured without cutting.

[0055]

INDUSTRIAL APPLICABILITY According to the present invention, a biaxially oriented polyethylene having a high Young's modulus, a small thickness, and a small thickness unevenness, which can be used as a magnetic recording tape with less fluctuation, deformation and damage of electromagnetic conversion characteristics, It is possible to provide a method for stably producing a 2,6-naphthalate film without breaking the film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ieyasu Kobayashi 3-37-19 Koyama, Sagamihara-shi, Kanagawa Teijin Limited Sagamihara Research Center

Claims (1)

[Claims] 1. A substantially non-oriented polyethylene-2,6
-A naphthalate film is stretched in the longitudinal direction, and the difference between the longitudinal refractive index (nM) and the lateral refractive index (nT) (nM-
nT) is 0.05 to 0.18, and then, after being stretched in the transverse direction, 150 to 150% under tension or under lateral contraction.
Refractive index in the lateral direction (n
The difference (nT-nM) between the refractive index (nM) in the vertical direction and that in the vertical direction is set to 0.03 to 0.10.
It is characterized in that it is stretched 1.8 to 2.4 times at 190 ° C., then stretched laterally again at 170 to 190 ° C. at 1.4 to 2.4 times, and then heat set at 190 to 250 ° C. And a method for producing a biaxially oriented polyethylene-2,6-naphthalate film.