JP2738645B2 - Polyethylene-2,6-naphthalate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biaxially oriented polyethylene.
For more details on the 2,6-naphthalate film,
The present invention relates to a biaxially oriented polyethylene-2,6-naphthalate film which can be recorded and reproduced for a long time and has high density and high image quality, and is particularly useful as a base film for a metal tape.

[0002]

2. Description of the Related Art Conventionally, polyethylene terephthalate films have been widely used as base films for magnetic tapes. In recent years, high-density recording has been increasingly required for magnetic tapes for downsizing and high image quality, and tape thinning and long-time recording, as represented by 8 mm video, have been required. For this reason, the surface of the magnetic layer on the magnetic layer side of the magnetic tape is required to be even smoother and thinner. Along with this, the base film is also required to have a flat and thin surface.

However, the surface of a conventional polyester film used for a magnetic tape of a home VTR is rough,
There is no product that satisfies the above-mentioned required characteristics and can be put to practical use. Therefore, for high-density recording, it is necessary to make the surface roughness extremely low. However, in general, when the surface roughness is reduced, slipperiness between the film surfaces is deteriorated, and escape of air existing between the films is deteriorated, so that it is very difficult to wind the film into a roll. The difficulty of such winding becomes more significant as the film becomes thinner.

[0004] In addition, it is necessary to make the base film thinner due to the demand for long-term recording of the magnetic tape. However, in the case of the conventional tape having a small thickness, the stiffness is reduced and the edge of the tape is damaged at the time of loading and unloading. In some cases, the tape becomes deformed when a high tensile force is applied instantaneously, and the recording is distorted.
Therefore, a high Young's modulus is required for a film serving as a base for a long-time recording magnetic tape.

Conventionally, a biaxially oriented polyethylene terephthalate film has been used as a base film of these magnetic recording tapes. In particular, a so-called supertensilized film having a high Young's modulus in the longitudinal direction for long-time recording is known. ing. However, such films have a Young's modulus in the longitudinal direction of at most 850 kg / mm ² , in which case the Young's modulus in the transverse direction is at most 450 kg / mm ² . As described above, when the Young's modulus in the vertical direction is to be increased, the Young's modulus in the horizontal direction is inevitably reduced. Therefore, when the magnetic tape is repeatedly run, the end of the tape is damaged and deformed into a wakame shape. On the other hand, if an attempt is made to increase the Young's modulus in the width (hereinafter sometimes referred to as “horizontal”) in the production of the film, in this case also, a sufficient Young's modulus in the vertical direction cannot necessarily be obtained, and the touch with the magnetic head is poor. The output fluctuates.

Further, with the recent spread of a camera-integrated VTR, the chance of using the camera outdoors and bringing it into a car has increased. Therefore, the tape is often exposed to more severe temperature conditions, and when recording and reproducing the magnetic tape in such a high temperature atmosphere, the base film, that is, the Young's modulus of the magnetic tape is reduced, and the magnetic tape is reduced. Elongation, wakame-like deformation, etc. occur, and the characteristics of the magnetic tape are impaired. For this reason, there is an increasing demand for dimensional stability of the tape so as not to cause skew distortion even when used in such a high-temperature atmosphere, and furthermore, dimensional stability of the base film. However, in a conventional base film in which the Young's modulus is increased by performing high-magnification stretching in order to reduce the thickness, distortion generated during molding remains, and dimensional stability is poor. Another drawback is that high-yield stretching reduces the product yield.

On the other hand, a film made of polyethylene-2,6-naphthalate (hereinafter sometimes referred to as “PEN”), which is a polyester having better heat-resistant dimensional stability than polyethylene terephthalate (hereinafter sometimes referred to as “PET”) Various magnetic tapes have been proposed.

For example, in JP-A-4-198328, the degree of plane orientation of a PEN film (hereinafter, sometimes referred to as "plane orientation coefficient") is specified in the range of 0.255 to 0.280 to improve slit properties and the like. Although this technique discloses a technique, this technique does not specify the main orientation direction, and does not find any improvement such as improvement of the magnetic head touch of the tape or prevention of edge damage by improving the transverse Young's modulus.

In the same publication, improvement of abrasion resistance and lubricity is improved by incorporating a particle composed of a primary particle aggregate having a specific particle size and a particle having another specific average particle size in a PEN film. Although disclosed, the surface shape of the film formed by them is not specified. For example, since there is no specific surface area or total pore volume of the particles, the particles are too hard, or too brittle, the abrasion resistance and scratch resistance are reduced, the effect of including a lubricant is There are drawbacks such as extremely small amounts. In addition, since the shape of the contained particles is not specified and the aggregated particles are used, it is expected that voids are generated in the film due to the particles, the abrasion resistance is reduced, and the effect due to the inclusion of the particles is similarly reduced. Further, in the publication, since there is no specification of the particle size distribution of the contained particles, even if the average particle size is the same, for example, if the particle size distribution is not sharp, the uniformity of the distribution of projections formed on the film surface is poor, Uniform surface projections of uniform height cannot be obtained, resulting in reduced slipperiness.

Japanese Patent Application Laid-Open No. 5-117421 discloses a technique in which the surface roughness and the like of a PEN film are specified in a specific range. In such a technique, for example, application and drying of a magnetic layer in a tape processing step are described. At this time, the base film receives a high tension load at a high temperature. At this time, there is a concern that the base film may be stretched, causing undulation, and causing application unevenness of the magnetic layer.

As described above, in the prior art, there is a demand for a base film for a magnetic recording medium, which has a small dimensional change in the vertical direction, has high strength, is excellent in flatness, and is capable of performing long-time, high-density recording. No satisfactory polyester film was found.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording tape which solves the above-mentioned drawbacks, has good electromagnetic conversion characteristics when used as a tape for high-density magnetic recording, and has both smoothness and durability. An object of the present invention is to provide a biaxially oriented PEN film for a medium.

[0013]

The present invention has the following arrangement to attain the object.

The Young's modulus [EM] in the vertical direction is 500 kg / mm
² or more, Young's modulus [ET] in the horizontal direction is 1000 kg / mm ²
And the Young's modulus in the transverse direction is greater than the Young's modulus in the longitudinal direction, the elongation in the transverse direction per 1 kg / mm ² load at 120 ° C. is in the range of 0 to 0.4%, and
A biaxially oriented polyethylene-2,6-naphthalate film having a plane orientation coefficient NS of 0.281 or more.

In the present invention, the PE constituting the film
N is a polyester composed of a dicarboxylic acid having 2,6-naphthalenedicarboxylic acid as a main acid component and a glycol having ethylene glycol as a main glycol component, and a small amount other than 2,6-naphthalenedicarboxylic acid. A small amount of a glycol component other than the dicarboxylic acid component and / or ethylene glycol may be contained as a copolymer component.

Examples of the dicarboxylic acids other than 2,6-naphthalenedicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, diphenylsulfonedicarboxylic acid, benzophenonedicarboxylic acid, and isomers of 2,6-naphthalenedicarboxylic acid. Succinic acid, adipic acid,
Examples thereof include aliphatic dicarboxylic acids such as sebacic acid and dodecanedicarboxylic acid, and alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid.

The glycol components other than ethylene glycol include, for example, 1,3-propanediol,
Examples thereof include 4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, diethylene glycol, and the like. Further, a polymer in which additives such as a stabilizer and a colorant are blended may be used.

Such a PEN film is usually produced by a known method by a melt polymerization method. At this time, additives such as a catalyst can be optionally used as needed. P
The intrinsic viscosity of EN is preferably in the range of 0.45 to 0.90, and more preferably in the range of 0.60 to 0.80.

The PEN film of the present invention has a lateral elongation of 0 to 1 kg / mm ^{2 at} 120 ° C.
It should be in the range of 0.4%, preferably 0%.
To 0.3%, more preferably 0 to 0.2%.
Range. When the elongation percentage in the transverse direction exceeds 0.4%, especially when the base film is used for a magnetic recording medium for high-density, high-quality recording, the base film is used when applying and drying a magnetic paint in a tape processing step. Is stretched in the lateral direction and the flatness of the film is deteriorated, so that it is difficult to perform precise uniform coating for a magnetic recording medium requiring high density coating.

In order to obtain a film having an elongation in the transverse direction of the present invention, it is necessary to select conditions including means for increasing the Young's modulus in the process of producing a biaxially oriented PEN film, It is preferable to consider a means for reducing the contraction rate in the vertical direction under the conditions. For example, the stretching ratio in the transverse direction is the same as or larger than the stretching ratio in the longitudinal direction, and it is necessary to select heat fixing conditions suitable for keeping the stretching ratio in the transverse direction low, if necessary. It is preferable to adjust the thermal relaxation conditions to reduce the thermal shrinkage. That is, since the elongation in the transverse direction of the present invention greatly changes depending on the stretching ratio and the heat setting temperature, the stretching ratio and the heat setting temperature are changed in advance within an appropriate condition range for obtaining the Young's modulus in the vertical and horizontal directions of the present invention. The elongation percentage in the horizontal direction of the film obtained is measured simultaneously with the Young's modulus in the vertical and horizontal directions, and the optimum stretching ratio and heat setting temperature are selected while comparing the measured values. Further, the polyester film of the present invention can be obtained by selecting a condition in which the shrinkage rate is set to a preferable range by thermal relaxation and the decrease in Young's modulus due to thermal relaxation does not deviate from the range of the transverse Young's modulus of the present invention.

The PEN film of the present invention needs to have a Young's modulus [EM] in the longitudinal direction of 500 kg / mm ² or more,
Preferably, it is 600 kg / mm ² or more, more preferably, 7 kg / mm ² or more.
00 kg / mm ² or more. Here, the vertical Young's modulus is 5
A film having a thickness of 100 to 600 kg / mm ² can maintain a high Young's modulus in the vertical direction as a tape by increasing the strength of the magnetic binder. However, the Young's modulus is 5
In the case of a film having a thickness of less than 00 kg / mm ² , in particular, the thickness of the base film is 12 μm or less, and the thickness of the tape is 16 μm
In the following magnetic tapes for long-time recording / reproduction, even if a high-strength magnetic binder is used, the Young's modulus of the tape is not sufficient, and the tape edge may be bent or the tape may be stretched while the tape is running. There is.

On the other hand, the transverse Young's modulus [ET] is 100
0 kg / mm ² or more, and preferably
1100 kg / mm ² or more, more preferably 1200 kg / mm ²
mm ² or more. This can prevent the end face of the tape from being damaged when the tape runs. When the Young's modulus in the horizontal direction is smaller than 1000 kg / mm ² , the magnetic tape is used for long-time recording and reproduction with a tape thickness of 8 μm or less and a recording and reproduction time of 180 minutes or more and high density and high image quality. In this case, even if a high-strength magnetic binder is used, damage to the tape end face cannot be prevented, and a uniform and high-precision magnetic film cannot be obtained.

It is necessary that the Young's modulus [ET] in the horizontal direction is larger than the Young's modulus [EM] in the vertical direction. If the Young's modulus in the horizontal direction is lower than the Young's modulus in the vertical direction, the familiarity (head touch) between the tape and the rotary head of the video tape recorder is poor, and a problem occurs in that the output is not sufficiently obtained during the reproduction of the recording signal, which is not preferable. . Further, if a film having a Young's modulus in the horizontal direction of 1000 kg / mm ² or more and a Young's modulus in the vertical direction is more than the Young's modulus in the horizontal direction, troubles such as cutting will occur at the time of manufacturing, and productivity will be remarkable. It is not preferable because it decreases.

As means for obtaining such a Young's modulus,
The film may be stretched simultaneously in the vertical and horizontal directions using a general roll or a stenter, or may be sequentially stretched in the vertical and horizontal directions.
The number of stretching in the vertical and horizontal directions may be one in each of the vertical and horizontal directions, and may be performed more times in multiple stages in the vertical and / or horizontal directions, but is not limited to the number of times.

For example, in the case of stretching in two steps, PEN is set to Tm
To (Tm + 70 ° C.) (where Tm is the melting point of PEN) to obtain an unstretched film having an intrinsic viscosity of 0.45 to 0.9 dl / g. Direction) (Tg-10)-(Tg + 70) ° C
(Tg: glass transition temperature of PEN).
The film is stretched at a magnification of 5 to 7.0 times, and then Tg (° C.) to (Tg + 70) ° C. in a direction perpendicular to the stretching direction (when the first-stage stretching is the longitudinal direction, the second-stage stretching is the horizontal direction). At a temperature of 4.5 to 8.0 times. In this case, the area stretching ratio is preferably 20 to 50 times, more preferably 30 to 50 times.

When the film is stretched three or more steps, the heat setting temperature of the two-step stretched film is set to (Tg + 2).
0) to (Tg + 70) ° C., and then stretched vertically or horizontally at a temperature 10 to 40 ° C. higher than the heat setting temperature, and if necessary, further stretched horizontally or 20 to 50 ° C. higher than this temperature. The film is stretched in the longitudinal direction, the total stretching ratio in the longitudinal direction is 3.0 to 6.0 times, and the total stretching ratio in the horizontal direction is 5.5 to 1
Preferably it is 2.0 times. In this case, the area stretching ratio is preferably 25 to 60 times, and more preferably 30 to 60 times.

The PEN film of the present invention has a plane orientation coefficient N
S needs to be 0.281 or more. here,
The plane orientation coefficient [NS] is a numerical value obtained by the following equation (2).

[0028]

(Equation 2)

In the equation (2), nx represents the refractive index of the biaxial film in the machine direction, ny represents the refractive index in the direction perpendicular to the machine direction, and nz represents the refractive index in the film thickness direction.

A base film having a plane orientation coefficient NS of 0.281 or more has sufficient stiffness and good thickness unevenness.
Since a uniform magnetic layer enabling high-density magnetic recording can be obtained in magnetic processing, a magnetic recording tape having a good trackability with a magnetic head when a magnetic tape is formed and having a stable output can be obtained. In the case where the plane orientation coefficient NS is less than 0.281, particularly when applied to a high-density magnetic recording tape for long-time recording / reproduction, contrary to the above, the base film is not sufficiently strong and the thickness unevenness is not sufficient. Therefore, a uniform magnetic layer that enables high-density magnetic recording cannot be obtained in magnetic processing, and a recording error or a reproduction error occurs.

In the PEN film of the present invention, the heat shrinkage in the longitudinal direction of the base film when heat-treated at 70 ° C. for 1 hour under no load is preferably 0.1% or less.
08% or less is more preferable, and 0.05% or less is particularly preferable. If the heat shrinkage is larger than 0.1%, thermal irreversible change occurs even after the magnetic tape is formed, and if the recording and reproduction temperatures of the VTR are different, skew distortion may occur on the screen, which is not preferable. . Also, if the heat shrinkage is large, an effect of set-off of the base film surface to the magnetic surface occurs, and the surface roughness of the magnetic surface tends to be rough.

As a means for lowering the heat shrinkage, it is general to raise the heat treatment temperature after stretching. However, if it is too high, the mechanical properties will deteriorate, and scratches during the magnetic tape processing step will also occur. The shavings increase, and the shavings adhere to the magnetic surface of the magnetic tape, causing dropout. For this reason, the heat shrinkage is reduced by heating the film after the heat treatment under low tension and relaxing in the longitudinal direction. As a method of relaxing in the longitudinal direction, for example, a method of relaxing in a non-contact state under heating and low tension by a floating treatment method by air force: a method of relaxing by giving a speed difference between a heating roll and a cooling roll each having a nip roll. ,
Alternatively, there is a method in which the clip is gradually relaxed in the vertical direction by gradually slowing the progress speed of the clip holding the film in the tenter, but any method can be used as long as it can relax in the vertical direction.

In any method, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° C. to Tm (° C.) after the stretching operation. For example, heat fixing is preferably performed at 190 to 250 ° C., and the heat fixing time is, for example, 1 to 60.
Seconds. Further, the film having the preferable shrinkage ratio of the present invention is obtained by thermal relaxation.

The height and the number of projections formed on the surface of the base film for a magnetic tape are within a specific range, and it is preferable that the winding characteristics of the base film, the running property when used as a magnetic tape, and the electromagnetic conversion characteristics are excellent. It was revealed. In the present invention, the number of protrusion heights h (unit: nm) of protrusions on the film surface is determined by the following formula (1).

[0035]

(Equation 3)

It is preferable to be within the range indicated by: More preferably, the following formula (1-2)

[0037]

(Equation 4)

And particularly preferably,
The following equation (1-3)

[0039]

(Equation 5)

Those satisfying the above range have good handleability of the base film, and are excellent in running property and electromagnetic conversion characteristics when used as a magnetic tape. Projection height h (unit n)
m) is 10000 / mm ² where 1 ≦ h <50
Exceeding this will cause the film to be scraped off by a roll during calendering when forming a magnetic tape. The number of protrusions whose height is 50 ≦ h <100 is 200 / mm ^2.
If the value exceeds, the electromagnetic conversion characteristics of a magnetic tape are reduced. When the number of 100 ≦ h <150 exceeds 100 pieces / mm ² , the tape running property is good, but the electromagnetic conversion characteristics are lowered and the dropout is caused. Further, when there are projections satisfying 150 ≦ h, the frequency of existence of the coarse projections increases, so that the electromagnetic conversion characteristics are remarkably reduced and dropouts frequently occur. Further, the coarse projections of 150 ≦ h promote the generation of dropouts because the projections are scraped off during tape running. The number satisfying 1 ≦ h <50 is less than 1000 pieces / mm ² , and the number satisfying 50 ≦ h <100 is 10 pieces / mm ^2.
less than mm ² and 100 ≦ h <150
If it is less than 0 pieces / mm ² , the coefficient of friction becomes large, and it becomes very difficult to handle the film and wind it up on a roll. Furthermore, the runnability when used as a tape also becomes poor. Here, the number of protrusions whose protrusion height is h <1 is not particularly limited.

In order to obtain a film having the above-mentioned film surface characteristics, for example, it is obtained by adding several kinds of inert solid fine particles having different particle size distributions to PEN. As the inert solid fine particles, preferably, (1) silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, etc.); (2) alumina; (3) silica containing 30% by weight or more of SiO ₂ component Acid salts (eg, amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), hot asbestos, zircon, fly ash, etc.); (4)
Oxides of Mg, Zn, Zr, and Ti; (5) sulfides of Ca and Ba; (6) phosphates of Li, Na, and Ca (including monohydrogen salts and dihydrogen salts); (7) Benzoates of Li, Na, and K; (8) Ca, Ba, Zn, and Mn
(9) Mg, Ca, Ba, Zn, C
titanates of d, Pb, Sr, Mn, Fe, Co, and Ni; (10) chromates of Ba and Pb; (11)
Carbon (eg, carbon black, graphite, etc.);
(12) glass (eg, glass powder, glass beads, etc.);
(13) Ca and Mg carbonates; (14) fluorite;
Fine particles composed of a polymer having high heat resistance such as (15) ZnS and (16) silicone resin, cross-linked polystyrene and the like are exemplified. More preferably, silicon dioxide, silicic anhydride, hydrated silicic acid, aluminum oxide, aluminum silicate (including calcined product, hydrate, etc.), monolithium phosphate, trilithium phosphate, sodium phosphate, calcium phosphate, barium sulfate, Titanium oxide, lithium benzoate, double salts of these compounds (including hydrates), glass powder, clay (including kaolin, bentonite, clay, etc.), talc, diatomaceous earth, calcium carbonate, silicone resin, cross-linked polystyrene, etc. And the like. Particularly preferred are titanium oxide, aluminum oxide having a crystal form of α, θ, γ type crystal form, spherical silica, spherical calcium carbonate, spherical silicon resin, and spherical cross-linked polystyrene.

When the above inert solid fine particles are added to PEN, they may be added before the polymerization of PEN, during the polymerization reaction, or may be kneaded in an extruder when pelletizing after the polymerization. It may be added when melt-extruded into a sheet and dispersed and extruded in an extruder,
It is preferable to add before polymerization from the viewpoint of dispersibility. However, the means for obtaining a film having the film surface characteristics of the present invention is not limited to the method of adding inert solid fine particles to PEN, and a phosphorus source or other necessary additives are added during polymerization to form a particle source. It is preferably used such as a method in which a polymer is formed by adding a phosphorus component at the time of polymerization and a polymer obtained by adding inert solid fine particles and polymerized.

Further, as a means for adjusting the film surface characteristics of the present invention, another surface treatment, such as a coating treatment, may be performed on the film containing no inert fine particles or on the film containing the inert fine particles. You can also.

The PEN film of the present invention is not particularly limited in its thickness, but preferably has a thickness of 12 μm or less, and is particularly used for a high-density and high-quality metal tape for long-time recording and reproduction of 180 minutes or more. In this case, the thickness is preferably 6 μm or less. The lower limit of the thickness is preferably 3 μm from the stiffness of the film.

[0045]

The present invention will be further described below with reference to examples. The various physical properties and properties in the present invention are measured and defined as follows.

(1) Number of surface protrusions Non-contact three-dimensional roughness meter (TOPO-3D) manufactured by WYKO
Measurement magnification: 40 times, measurement area: 242 μm × 239
The measurement was performed under the condition of μm (0.058 mm ² ). A histogram diagram of the height of the surface protrusions and the number of protrusions based on the average roughness of the film surface is obtained by the protrusion analysis, and the number of each protrusion height range is read from the histogram diagram, and the number of protrusions measured five times on the same film surface is calculated. Multiply and calculate the unit area (1
It was converted to the number of protrusions per mm ² ).

(2) Young's modulus A film was cut into a sample having a width of 10 mm and a length of 15 mm.
The film was pulled at a speed of 00 mm / min using an Instron type universal tensile tester. The Young's modulus was calculated from the tangent at the rising portion of the obtained load-elongation curve.

(3) Refractive index The refractive index was measured using an Abbe refractometer with sodium D line (589 nm) as a light source. Kanzaki Paper Co., Ltd.
The degree of orientation was measured using a molecular orientation meter (MOA-2001A) manufactured by Kobe Steel Co., Ltd., and the refractive index having a large value that could not be measured by the Abbe refractometer was determined by creating a correlation graph between the degree of orientation and the refractive index and from the correlation graph. .

(4) Film Elongation Using TMA (TM-3000L) manufactured by Vacuum Riko Co., Ltd., a sample having a film width of 5 mm and a length of 15 mm was used. Load conditions: 0 g (no load), 25 g, 50 g, 75 g, 10
0 g under each condition at a heating rate of 5 ° C./min.
℃ to 150 ℃, 120 ℃ for each load
Was read from a chart, and a correlation graph between the expansion and contraction rate and the load per kg of the film cross-sectional area (kg / mm ² ) was prepared, and the elongation rate (%) per 1 kg / mm ² was determined from the graph.

(5) Electromagnetic Conversion Characteristics The S / N ratio of the magnetic tape for video was measured using a noise meter manufactured by Shibasoku Co., Ltd. The VTR used was an EV-S700 manufactured by Sony Corporation.

(6) Running Durability of Magnetic Tape The running of the magnetic tape was repeated for 100 hours using an EV-S700 manufactured by Sony Corporation while repeatedly starting and stopping, and the running state was checked and the output was measured. The running durability of the magnetic tape at this time was determined as follows. <Three-step judgment> ○ The tape is not stretched, the end of the tape is not broken, and it does not become wakame. There is no output fluctuation. Δ: The tape slightly expanded, the tape edge was broken, and wakame occurred, and the output fluctuated slightly. C: The tape is remarkably stretched, broken, and wakame. In addition, the running of the tape becomes unstable, and the output fluctuates greatly.

(7) Heat Shrinkage A film having a length of about 30 cm and a width of 1 cm measured in advance in an oven set to 70 ° C. without load is heat-treated for 1 hour, and then heat-treated for 1 hour. The sample was removed and allowed to return to room temperature before reading the change in its dimensions. From the length (L0) before the heat treatment and the dimensional change (ΔL) due to the heat treatment, the heat shrinkage (%) was determined by the following equation (3).

[0053]

(Equation 6)

(8) Skew The skew characteristic is as follows. After a video tape recorded at room temperature (20 ° C.) and normal humidity is heat-treated at 70 ° C. for 1 hour, it is reproduced again at room temperature and normal humidity, and the amount of deviation at the head switching point is read. Was.

(9) Inert Particle Average Particle Size CP-50 Centrifugal Particle Size Analyzer (Centrifugal Particle S) manufactured by Shimadzu Corporation
ize Analyzer). From the cumulative curve of the particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, the particle size corresponding to 50 mass percent (mass percent) was read, and this value was defined as the above average particle size. did.

(10) Good winding rate The film is 500 mm wide and 4000 m long, and 100
The number of non-defective products obtained when this winding was performed is shown as a percentage.
At this time, the non-defective product means the following. The film is rolled up in a cylindrical shape and is not angular or sagging. There are no wrinkles on the film roll.

Example 1 An intrinsic viscosity of 0.62 dl / g containing 0.15% by weight of spherical silica particles having an average particle size of 0.15 μm and 0.03% by weight of calcium carbonate particles having an average particle size of 0.4 μm. (Measured at 25 ° C. using orthochlorophenol as a solvent)
Dried at 300 ° C., melt-extruded at 300 ° C., quenched and solidified on a casting drum kept at 60 ° C.
An unstretched film having a thickness of μm was obtained.

This unstretched film was successively biaxially stretched at 130 ° C. in the longitudinal direction by 2.2 times and then in the transverse direction at 130 ° C. by 4.2 times, followed by intermediate heat treatment at 160 ° C. The film was further stretched 2.0 times in the longitudinal direction at 170 ° C. and 2.0 times in the transverse direction, and further heat-set at 215 ° C. Next, this heat-fixed biaxially oriented PEN film is
After heating to 10 ° C., the longitudinal heat shrinkage was adjusted to 0.03% by adjusting the tension with the cooling roll.
The obtained film thickness was 6 μm.

On the other hand, the following composition 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.
A high-speed shearing dispersion was performed for 1 hour to obtain a magnetic paint. Composition of magnetic paint Needle-like Fe particles 100 parts by weight Vinyl chloride-vinyl acetate copolymer (SREC 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 Part 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 applied to one surface of the above-mentioned biaxially oriented PEN film so as to have a coating thickness of 3 μm, and then 2500
Perform orientation treatment in a Gauss DC magnetic field, heat dry at 100 ° C, and supercalender treatment (linear pressure 200kg / c
m, temperature 80 ° C) and wound up. The wound roll was left in an oven at 55 ° C. for 3 days.

Further, a paint for a back coat layer having the following composition was applied to a thickness of 1 μm, dried, and cut by 8 mm to obtain a magnetic tape. Backcoat layer coating 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

Table 1 shows the properties of the obtained films and tapes.
Shown in As is clear from this table, the good winding rate was good, there was no problem in workability, the running durability was good, the electromagnetic conversion characteristics and skew were good, and the use in a high-temperature atmosphere was good.

Example 2 An unstretched film was obtained in the same manner as in Example 1, and the unstretched film was stretched 2.2 times at 130 ° C. in the machine direction, and then 4.2 times at 130 ° C. in the transverse direction. The film was stretched and subsequently subjected to an intermediate heat treatment at 160 ° C. This film was further stretched 2.0 times in the longitudinal direction at 170 ° C. and 2.2 times in the transverse direction, and heat-treated at 215 ° C. Then, in the same manner as in Example 1, the heat shrinkage in the vertical direction was adjusted to 0.03%. Thus, a biaxially oriented film having a thickness of 6 μm was obtained. Thereafter, a tape was obtained in the same manner as in Example 1. Table 1 shows the results. Good results were obtained as in Example 1.

Comparative Example 1 0.2% by weight of spherical silica particles having an average particle diameter of 0.1 μm as small-sized particles and 0.2% by weight of calcium carbonate having an average particle diameter of 0.45 μm as large-sized particles.
A PET pellet having an intrinsic viscosity of 0.65 dl / g (measured at 25 ° C. using orthochlorophenol as a solvent) containing 05% by weight was dried at 160 ° C., and then dried at 280 ° C.
The mixture was melt-extruded at a temperature of 40 ° C. and quenched and solidified on a casting drum maintained at a temperature of 40 ° C. to obtain an unstretched film having a thickness of about 110 μm. This unstretched film is subjected to speed difference 2
The film was stretched 3.2 times in the longitudinal direction between the two rolls, further stretched 4.5 times in the transverse direction by a tenter, and further stretched 1.1 times in the transverse direction while being heat-set at 215 ° C. Then, the heat-set biaxially oriented PET film is
After heating to 0 ° C., the tension between the roll and the cooling roll was adjusted to reduce the heat shrinkage in the vertical direction, and the thickness was 7 μm.
Was obtained. Subsequently, a tape was obtained in the same manner as in Example 1. The results are shown in Table 1. The heat shrinkage was high and the skew was remarkably poor because the material was a PET material, despite the fact that the heat yield was reduced by relaxation heat treatment. The load 1 at 120 ° C.
Since the elongation rate in the lateral direction per kg / mm ² was very large, the film was sagged in the tape processing step and the flatness was poor, so that the coating unevenness of the magnetic layer occurred. Furthermore, the transverse stretching ratio was increased to increase the transverse Young's modulus, but the longitudinal Young's modulus was not able to sufficiently increase the longitudinal stretching ratio, the Young's modulus was reduced, and elongation occurred during tape running,
Poor running durability, poor electromagnetic conversion characteristics, PE
T material is inferior to PEN in total balance.

[Comparative Example 2] An unstretched film was obtained in the same manner as in Example 1, and the unstretched film was stretched 4.2 times at 130 ° C in the machine direction and 5.0 times at 135 ° C in the transverse direction. While sequentially performing biaxial stretching and further performing heat fixing at 215 ° C.
Stretched 5 times in the horizontal direction, and then in the same manner as in Example 1,
The heat shrinkage in the longitudinal direction was adjusted to 0.03% to obtain a film and a tape. Table 1 shows the results. Since the longitudinal Young's modulus was low, tape elongation occurred and running durability was poor. Also, the electromagnetic conversion characteristics were not good because the tape was weak.

Comparative Example 3 Instead of the inert particles added in Example 2, 0.2% by weight of silica particles having an average particle size of 0.1 μm as small particles and 0.2% by mass as large particles were used. 2 μm of calcium carbonate particles were added at 0.09% by weight, and an unstretched film was obtained in the same manner as in Example 1. The unstretched film was stretched 3.4 times in the machine direction at 130 ° C., and then in the transverse direction. Stretched 3.4 times at 25 ° C. and heat-treated at 255 ° C. to obtain a 7 μm-thick biaxially oriented film without any relaxation treatment for adjusting the heat shrinkage in the longitudinal direction. I got the tape. Table 1 shows the results.
The plane orientation coefficient NS of the base film is out of the range of the present invention, and the yield rate is poor due to uneven thickness and poor flatness, and the running durability is extremely poor because the Young's modulus is low in both the vertical and horizontal directions. . Furthermore, because a large number of fine projections and coarse projections are scattered on the film surface, the electromagnetic conversion characteristics are reduced,
A dropout has occurred. In addition, since coarse protrusions are scattered on the tape surface, white powder is remarkably generated due to shaving during tape running.

[0066]

[Table 1]

[0067]

According to the present invention, the winding characteristics of the base film are excellent, the coating processability of the magnetic layer is excellent, the running durability of the tape is good, the output fluctuation is small, the electromagnetic conversion characteristics are excellent, and Polyethylene-2,6 with improved skew distortion, capable of recording for a long time and capable of high-density, high-quality recording, particularly useful as a base film for metal tape.
A naphthalate film can be provided;

Continuation of the front page (56) References JP-A-7-178806 (JP, A) JP-A-5-261805 (JP, A) JP-A-5-212787 (JP, A) JP-A-5-192993 (JP) JP-A-5-162196 (JP, A) JP-A-5-117421 (JP, A)

Claims (3)

(57) [Claims] 1. A longitudinal Young's modulus [EM] of 500 kg /
mm ² or more, Young's modulus [ET] in the horizontal direction is 1000 kg / mm
² or more, and the Young's modulus in the horizontal direction is larger than the Young's modulus in the vertical direction, the elongation in the horizontal direction per 1 kg / mm ² load at 120 ° C. is in the range of 0 to 0.4%, and A biaxially oriented polyethylene-2,6-naphthalate film having a plane orientation coefficient NS of 0.281 or more. 2. The biaxially oriented polyethylene-2,6-naphthalate film according to claim 1, wherein the heat shrinkage in the longitudinal direction when heat-treated at 70 ° C. for 1 hour without load is 0.1% or less. 3. The height h of a projection formed on the film surface.
The biaxially oriented polyethylene according to claim 1 or 2, wherein the number of (unit: nm) is in a range represented by the following formula (1).
2,6-naphthalate film. (Equation 1)