JP2771356B2 - Polyethylene-2,6-naphthalate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biaxially oriented polyethylene.
The present invention relates to a 2,6-naphthalate film, and more particularly to a biaxially oriented polyethylene 2,6-naphthalate film useful as a magnetic recording medium for high-density recording, particularly 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. 2. Description of the Related Art In recent years, magnetic tapes have been required to have higher density recording for miniaturization and higher image quality, and thinner tapes such as 8 mm video have been required. For this reason, the surface of the magnetic tape on the side of the magnetic layer 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, a polyester film used for a conventional home magnetic tape of a VTR has a rough surface, and there is no film which 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, the slipperiness between the film surfaces is deteriorated, and the escape of the air existing between the films is deteriorated, and it becomes very difficult to wind the film on a roll. Also, the difficulty becomes more significant as the film becomes thinner. Further, as the film becomes thinner, a higher Young's modulus is required. On the other hand, the higher the Young's modulus,
Generally, not only the heat shrinkage is large and the dimensional stability after forming a magnetic tape is inferior, but also the set-off phenomenon in the heat treatment process after applying the magnetic layer and smoothing the surface (roll-like winding) In the heat treatment step of thermosetting the magnetic tape, the finished magnetic surface and the base film surface are tightly wound relative to each other, so that the finished magnetic surface is roughened, which deteriorates the electromagnetic conversion characteristics. . Therefore,
Heretofore, no polyester film that sufficiently satisfies the requirements for a polyester film used for such a high-density recording tape has been found.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks and to provide a magnetic recording medium which has good electromagnetic conversion characteristics when used as a high-density magnetic recording tape and is easy to wind up in a roll. An object of the present invention is to provide a biaxially oriented polyethylene-2,6-naphthalate film.

[0004]

The present invention has the following arrangement to attain the object. Monodisperse silica having an average particle size of 0.05 to 0.3 μm is used as a small particle size in the film, 0.05 to 0.4% by weight, and an inert particle having an average particle size of 0.3 to 1.0 μm. 0.005 to 0.05% by weight of solid particles as large-diameter particles, and the difference between the average diameter of the large-diameter particles and the small-diameter particles is 0.2 μm or more;
The thickness of the film is 2 to 12 μm, the surface roughness Ra of the film is 0.003 to 0.010 μm, the Young's modulus (EM) in the vertical direction is 650 kg / mm ² or more, and the Young's modulus in the horizontal direction (E _T ) Is not less than 600 kg / mm ² , their ratio (EM / ET) is in the range of 0.9 to 1.5, and the heat shrinkage in the longitudinal direction when heat-treated at 70 ° C. for 1 hour without load. Is biaxially oriented polyethylene having a content of not more than 0.08%
2,6-naphthalate film.

In the present invention, the polyethylene-2,6-naphthalate constituting the film contains naphthalenedicarboxylic acid as a main acid component, but may use a small amount of another dicarboxylic acid component, or ethylene glycol as a main component. The polymer is a glycol component, but may be used in combination with a small amount of another glycol component. Examples of dicarboxylic acids other than naphthalenedicarboxylic acid include terephthalic acid, isophthalic acid, diphenylsulfonedicarboxylic acid,
Examples include aromatic dicarboxylic acids such as benzophenone dicarboxylic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecane dicarboxylic acid, and alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantane dicarboxylic acid. be able to. As glycol components other than ethylene glycol, for example, 1,
3-propanediol, 1,4-butanediol, 1,
6-hexanediol, neopentyl glycol, 1,
4-cyclohexanedimethanol, p-xylylene glycol and the like can be mentioned. Further, a polymer in which additives such as a stabilizer and a colorant are blended may be used. Such polyethylene-2,6-naphthalate 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.

[0006] The intrinsic viscosity of polyethylene-2,6-naphthalate is preferably in the range of 0.45 to 0.90.

In the present invention, the above polyethylene-2,
As the inert solid particles contained in 6-naphthalate, preferably, (1) silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, monodispersed silica, etc.); (2) alumina; (3) Silicates containing 30% by weight or more of SiO ₂ (eg, amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), hot asbestos, zircon, fly ash, etc.); ) Mg, Zn, Z
(5) Ca and Ba sulfates; (6) Li, Na, and Ca phosphates (including mono- and di-hydrogen salts); (7) Li, Na And (8) terephthalates of Ca, Ba, Zn, and Mn; (9) Mg, Ca, Ba, Zn, Cd, Pb;
Titanates of Sr, Mn, Fe, Co, and Ni; (1
0) chromates of Ba and Pb; (11) carbon (eg, carbon black, graphite, etc.); (12) glass (eg, glass powder, glass beads, etc.); (13) C
a and Mg carbonates; (14) fluorite and (15)
ZnS is exemplified. More preferably, silicon dioxide,
Silicic anhydride, hydrous silicic acid, alumina, aluminum silicate (including calcined products, hydrates, etc.), 1 lithium lithium phosphate, 3 lithium phosphate, sodium phosphate, calcium phosphate, barium sulfate, titanium oxide, lithium benzoate, etc. (Including hydrates), glass powder, clay (including kaolin, bentonite, clay, etc.), talc, diatomaceous earth, calcium carbonate and the like. Particularly preferably,
Monodisperse silica, titanium oxide, alumina, and calcium carbonate are exemplified.

[0008] In the present invention, among such inert solid particles, the average particle diameter of the small-diameter particles is from 0.05 to 0.05.
0.3 [mu] m, preferably 0.10 to 0.3 [mu] m, in an amount of 0.05 to 0.4% by weight, preferably 0.1 to 0.3% by weight, and As the large-diameter particles, those having an average particle diameter of 0.3 to 1.0 μm, preferably 0.5 to 0.8 μm, and the added amount of 0.005 to 0.05% by weight, preferably 0.1 to 0.05% by weight. 01 ~
It is used in a range satisfying 0.03% by weight. It is desirable not to add a large amount of particles in terms of electromagnetic conversion characteristics, but if not added, winding becomes difficult. Therefore, it is preferable to add a very small amount of large-diameter particles to improve the winding property. However, adding more than 0.05% by weight is not preferable because the electromagnetic conversion characteristics deteriorate. On the other hand, small particle size
Unless it is added in an amount of 0.05% by weight or more, winding is difficult even if large-diameter particles are added. If it is added in an amount of more than 0.4% by weight, it is not preferable in terms of electromagnetic conversion characteristics. At this time, the difference between the average particle diameter of the large particle and the average particle diameter of the small particle is required to be 0.2 μm or more, and preferably 0.3 μm or more. If this difference is smaller than 0.2 μm, a material satisfying both the winding property and the electromagnetic conversion characteristics cannot be obtained.

The polyethylene-2,6-naphthalate film of the present invention comprises polyethylene-2,6-naphthalate containing the above-mentioned two large and small inert solid particles, and further has a film surface roughness (Ra). Is 0.003 ~
It needs to be 0.010 μm. Ra is 0.0
If it is larger than 10 μm, it is difficult to maintain the required electromagnetic conversion characteristics as a magnetic tape for high-density recording. If Ra is smaller than 0.003 μm, the coefficient of friction increases, and the film is easily handled and rolled up into a roll. It becomes very difficult.

The polyethylene-2,6-naphthalate film further has a Young's modulus (EM) in the longitudinal direction of 650 kg.
/ Mm ² or more, Young's modulus (ET) in the lateral direction is 600 kg / mm
² or more, and their ratio (EM / ET) is 0.9 to
It must be in the range of 1.5. In particular, when the thickness of the base film is 12 μm or less and the thickness of the tape is 16
With a magnetic tape of μm or less, the longitudinal direction is lower than 650 kg / mm ² , and if the lateral direction is lower than 600 kg / mm ² , the tape edge may be bent or the tape may be stretched during the running of the tape. On the other hand, when the Young's modulus is low, the pressing of the tape against the video rotary head becomes weak, and the electromagnetic conversion characteristics deteriorate. If the Young's modulus ratio (EM / ET) is not in the range of 0.9 to 1.5, the electromagnetic conversion characteristics deteriorate.

As means for obtaining such a Young's modulus, a general roll or a stenter may be used to simultaneously stretch in the longitudinal and transverse directions, may be sequentially stretched in the longitudinal and transverse directions, or may be stretched two or more steps in the longitudinal and transverse directions. May be used.

The polyethylene-2,6-naphthalate film must further have a longitudinal heat shrinkage of 0.08% or less when heat-treated at 70 ° C. for 1 hour under no load. . Preferred heat shrinkage is 0.04%
It is as follows. If this heat shrinkage is greater than 0.08%,
Thermal irreversible change occurs even after the tape is formed, and VTR
If the recording and reproducing temperatures are different, skew distortion occurs on the screen. 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 becomes rough. As a means for reducing the heat shrinkage rate at 70 ° C. for one hour, it is general to increase the heat treatment temperature after stretching. However, if it is too high, the mechanical properties are deteriorated. Scratches and scratches increase, and the shavings adhere to the magnetic surface of the magnetic tape.
Cause dropout. As a means for solving this problem, there is a method in which a film is passed between two rolls having a difference in speed, and a relaxation treatment is performed by applying a temperature higher than the glass transition temperature (Tg) of polyethylene-2,6-naphthalate. However, the present invention is not limited to this.

The polyethylene-2,6-naphthalate film of the present invention has a thickness of 2 to 12 μm.

The biaxially oriented polyethylene of the present invention-2,6-
When a magnetic recording tape is made using a naphthalate film, the surface roughness of the magnetic surface is low, and the pressing pressure between the tape and the head in the VCR increases, so that the electromagnetic conversion characteristics required for high-density magnetic recording are obtained. Can be Further, there are few abnormalities such as breakage of the tape edge and tape elongation which occur during the running of the VCR, and the thermal stability is good, so that the skew distortion is small. Therefore, the biaxially oriented polyethylene of the present invention-
2,6-Naphthalate films are useful as base films for high-density magnetic recording tapes, especially metal tapes.

[0015]

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) Young's modulus A film was cut into a sample having a width of 10 mm and a length of 15 cm.
It was pulled at 00 mm / min by 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.

(2) Film Surface Roughness (Ra) Using a stylus type surface roughness meter (Surfcoder 30C) manufactured by Kosaka Laboratory Co., Ltd., a chart with a needle radius of 2 μm and a stylus pressure of 30 mg. (Film surface roughness curve). From the film surface roughness curve, a portion of the measured length L is extracted in the direction of the center line, the center line of the extracted portion is set as the X axis, the direction of the vertical magnification is set as the Y axis, and the roughness curve is expressed as Y = f.
When represented by (x), R given by the following equation (Equation 1)
a (μm) is defined as the film surface roughness.

[0018]

(Equation 1) In the present invention, the measurement length was 1.25 mm, the cutoff value was 0.08 mm, and the average value measured five times was Ra.

(3) Electromagnetic Conversion Characteristics The S / N ratio of the magnetic tape for video 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 3 shown in Table 1 was determined. The VTR used was an EV-S700 manufactured by Sony Corporation.

(4) Durability of Magnetic Tape The vehicle was run for 100 hours while repeatedly running and stopping with an EV-S700 manufactured by Sony Corporation, 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 end of the tape is not broken or wakame. Also, there is no scraping and no white powder adhesion. Δ: Slight breakage of the tape end or wakame occurs, and a small amount of white powder adhered. X: The breakage of the tape and the occurrence of seaweed are remarkable. Further, the tape is sharply scraped and a large amount of white powder is generated.

(5) Heat shrinkage A film having a length of about 30 cm and a width of 1 cm, which has been measured accurately in advance, is placed in an oven set at 70 ° C. with no load, and heat-treated for 1 hour. The sample was removed and allowed to return to room temperature before reading its dimensional change. From the length (L ₀ ) before the heat treatment and the dimensional change (ΔL) due to the heat treatment, the heat shrinkage is calculated by the following equation (Equation 2).

[0022]

(Equation 2)

(6) 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.

(7) Non-defective 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 on a cylinder and is not square or sagging. There are no wrinkles on the film roll.

(8) 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 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. did.

[0026]

Example 1 An intrinsic viscosity of 0.62 dl / g containing 0.2% by weight of monodispersed silica particles having an average particle size of 0.1 μm and 0.014% by weight of calcium carbonate particles having an average particle size of 0.6 μm.
Polyethylene-2,6-naphthalate (measured at 25 ° C. using orthochlorophenol as a solvent) was dried at 170 ° C., melt-extruded at 300 ° C., and quenched and solidified on a casting drum maintained at 60 ° C. 1
An unstretched film having a thickness of 80 μm was obtained.

This unstretched film is stretched 4.85 times in the machine direction at a temperature of 125 ° C. between two rolls having a difference in speed, further stretched 5.15 times in the transverse direction by a tenter, and then at 215 ° C. Heat treatment was performed for 10 seconds. One more
A floating heat treatment was performed in an oven heated to 10 ° C., thereby performing a 0.3% relaxation treatment.

Thus, a biaxially oriented polyethylene-2,6-naphthalate film having a thickness of 7 μm was wound.

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.

[0030]

[Table 1]

This magnetic paint was treated with the above polyethylene-2,
One side of the 6-naphthalate film is coated so as to have a coating thickness of 3 μm, then subjected to an orientation treatment in a DC magnetic field of 2500 gauss, heated and dried 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.

Further, a backcoat paint having the following composition was applied to a thickness of 1 μm, dried, and cut into 8 mm to obtain a magnetic tape.

[0033]

[Table 2]

The characteristics of the obtained film and tape are
It is shown in the table (Table 3). As is clear from this table, the good winding rate was good, and the electromagnetic conversion characteristics, running durability, and skew were also good.

[0035]

Example 2 An unstretched film was obtained in the same manner as in Example 1. The unstretched film was stretched 2.3 times in the machine direction at 130 ° C., and then 4.0 times in the transverse direction at 130 ° C. Subsequently, an intermediate heat treatment was performed at 160 ° C. This film was further stretched 2.4 times in the longitudinal direction at 170 ° C. and 1.5 times in the transverse direction, and heat-treated at 215 ° C. Thus, a biaxially oriented film having a thickness of 7 μm was obtained. Thereafter, a tape was obtained in the same manner as in Example 1. The results are shown in Table 1 (Table 3). Good results were obtained as in Example 1.

[0036]

Example 3 Instead of the inert particles added in Example 1, 0.35% by weight of monodispersed silica particles having an average particle size of 0.1 μm as small particles and 0.3% by weight as large particles were used.
An unstretched film was obtained in the same manner as in Example 1 except that 0.01% by weight of 8 μm of calcium carbonate particles was added, and then a biaxially oriented film having a thickness of 7 μm was obtained in the same manner as in Example 2. Thereafter, a tape was obtained in the same manner as in Example 1. The results are shown in Table 1 (Table 3). Good results were obtained as in Example 1.

[0037]

Example 4 Instead of the inert particles in Example 3, 0.3% by weight of monodispersed silica particles having an average particle size of 0.25 μm and 0.0% of calcium carbonate particles having an average particle size of 0.5 μm were used.
A film and a tape were obtained in the same manner as in Example 3 except that 15% by weight was used. The results are shown in Table 1 (Table 3). Good results were obtained as in Example 3.

[0038]

Comparative Example 1 A biaxially oriented film having a thickness of 7 μm was prepared in the same manner as in Example 1 except that 0.05% by weight of monodisperse silica having an average particle size of 0.02 μm was used instead of the inert particles added in Example 1. However, winding was impossible due to poor slippage of the base film, and a magnetic tape could not be obtained.

[0039]

COMPARATIVE EXAMPLE 2 Instead of the inert particles added in Example 1, 0.3% by weight of monodispersed silica having an average particle size of 0.15 .mu.m as small particles and 0.2 .mu.m as large particles were used.
A film and a tape were obtained in the same manner as in Example 1 except that 0.03% by weight of calcium carbonate was added. The results are shown in Table 1 (Table 3). The electromagnetic conversion characteristics of the tape are also deteriorated, and the yield ratio of the wound product is 50%, which is worse than that of the first embodiment.

[0040]

Comparative Example 3 In Example 1, the longitudinal stretching ratio was 3.7 times.
The film and tape were obtained by stretching the film to a transverse stretching ratio of 4.0 times (the stretching temperature was the same as in Example 1 for both the length and width). The results are shown in Table 1 (Table 3). The running durability was poor due to the low Young's modulus. Also, the electromagnetic conversion characteristics were not good due to the weakness of the tape.

[0041]

Comparative Example 4 A film and a tape were obtained in the same manner as in Example 1 except that the relaxation treatment was omitted.
The results are shown in Table 1 (Table 3). The skew was large due to the high heat shrinkage, and the magnetic surface was roughened due to the set-off effect, and the electromagnetic conversion characteristics were somewhat poor.

[0042]

Comparative Example 5 Instead of the inert particles added in Example 2, 0.2% by weight of monodisperse silica having an average particle diameter of 0.35 μm was used as the small particle, and the average particle diameter was 1.2 μm as the large particle.
A film and a tape were obtained in the same manner as in Example 2 except that 0.01% by weight of m calcium carbonate was added. The results are shown in Table 1 (Table 3). Since the surface roughness (Ra) of the base film is large, the magnetic surface is roughened and the electromagnetic conversion characteristics are poor. In addition, since the large-diameter particles have a large particle size and coarse projections are scattered on the tape surface, a slight shaving occurs when the tape runs, and the running durability is slightly poor.

[0043]

Comparative Example 6 Instead of the inert solid particles added in Example 1, 0.35% by weight of monodispersed silica having an average particle diameter of 0.1 μm was used as small-sized particles, and 0.3% by weight was used as large-sized particles.
An unstretched film was obtained in the same manner as in Example 1 except that 0.01% by weight of 8 μm calcium carbonate particles were added, and the unstretched film was stretched 2.3 times in the machine direction at 130 ° C., and then in the transverse direction. Stretched 4.0 times at 130 ° C.
1. Intermediate heat treatment at 60 ° C, and then longitudinally at 170 ° C.
After heat treatment at 215 ° C. 6 times, the same film and tape as in Example 1 were obtained. The results are shown in Table 1 (Table 3). Since the Young's modulus of the tape in the lateral direction is low and weak, edge damage is caused and running durability is somewhat poor. Further, since the ratio of the Young's modulus to the width is large, the familiarity with the VTR head is poor and the electromagnetic conversion characteristics are not good.

[0044]

COMPARATIVE EXAMPLE 7 Instead of the inert particles added in Example 2, 0.5% by weight of monodispersed silica having an average particle diameter of 0.1 μm as small-sized particles and 1.2 μm as large-sized particles.
A film and a tape were obtained in the same manner as in Example 2 except that 0.07% by weight of calcium carbonate particles was added. The results are shown in Table 1 (Table 3). The surface roughness (Ra) of the base film is very large, and the magnetic surface is rough, so that the electromagnetic conversion characteristics are poor, and the generation of white powder due to shaving is remarkable.

[0045]

[Table 3]

[0046]

According to the present invention, polyethylene-2,6-naphthalate having excellent electromagnetic conversion characteristics, running durability, skew distortion, winding characteristics, etc., and useful as a base film for high-density magnetic recording media, especially metal tapes. A film can be provided.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 67/02 C08L 67/02 // B29K 67:00 B29L 7:00 (72) Inventor Masami Etsuna 3 Oyama, Sagamihara City, Kanagawa Prefecture No. 37-19, Teijin Limited Sagamihara Research Center (56) References JP-A-62-143938 (JP, A) JP-A-2-202924 (JP, A) JP-A-63-235335 (JP, A)

Claims (2)

(57) [Claims] 1. A film having an average particle size of 0.05 to 0.1.
3 μm monodisperse silica is used as small particle
0.4% by weight, and inert solid particles having an average particle size of
5% by weight, and the difference between the average particle size of the large particle size and the small particle size is 0.2 μm or more, and the thickness of the film is 2 to 2.
12 μm, and the surface roughness Ra of the film is 0.003.
０．０0.010 μm, Young's modulus (EM) in the vertical direction is 650 kg / mm ² or more, and Young's modulus (ET) in the horizontal direction is 60
0 kg / mm ² or more, these ratios (E M / E T) are in the range of 0.9 to 1.5, and the heat shrinkage in the longitudinal direction when heat-treated at 70 ° C. for 1 hour without load is 0%. 0.08%
The following biaxially oriented polyethylene-2,6-naphthalate film. 2. A biaxially oriented polyethylene-2,6-naphthalate fill beam according to claim 1, wherein the inert solid particles are of calcium carbonate as large particles.