JPH0911429A - Polyester film for metal coating type magnetic medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film, the shape as wound of which is favorable and which prevents the surface of which from being abraded even when a magnetic layer is coated at a high speed by a method wherein the content of particle in a laminated part is set to be below a specified value, the surface projection interval of the film is below a specified value at both the sides of the film and the surface roughness of the film is above a specified value at both the sides of the film made by laminating a polyester onto both the sides of a polyester. SOLUTION: A polyester film for a metal coating type magnetic medium is made by laminating a polyester onto both the sides of a polyester. In the film, the content of particle in the laminated parts on both the sides is set to be below 0.5wt.%. If the content of particle exceeds the above-mentioned value, poor abrasion resistance results. Further, the surface projection interval is below 15μm at the sides of the film. If the surface projection interval even at one side of the film exceeds the above- mentioned value, the output as the both metal coating type magnetic medium lowers and poor shape as wound and abrasion resistance result. Furthermore, the average surface roughness is above 10nm at both the sides of the film. If the surface roughness even at one side of the film is below the above-mentioned value, poor shape as wound and abrasion resistance result and the durability of the magnetic surface as the metal coating type magnetic medium tends to fail.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film used for a support of a metal-coated magnetic medium, that is, a magnetic recording medium coated with a metal magnetic powder which is not an oxide together with a binder.

[0002]

2. Description of the Related Art As a polyester film for a metal-coated magnetic medium, a smooth film in which the number of protrusions and the number of particles on the surface opposite to the surface used on the magnetic surface side are limited is known (see, for example, No. 6-325349). Further, as a support film used for high-density recording such as a metal-coated magnetic medium, a co-extruded composite film in which one surface is smooth and the other surface is considerably larger is known (for example, a special film). Kaisho 60-20253
No. 0).

[0003]

However, the above-mentioned conventional smooth film has a problem that wrinkles are formed when slitting is performed due to recent enlargement of product width and increase of slitting speed, and roll appearance is deteriorated. With the increase in the speed of the coating process of the magnetic layer, the problem that the film surface on the magnetic surface side is shaved when the film comes into contact with a die coater and powder is generated has recently become apparent.

The present invention solves the above-mentioned problems, and a film roll having a good winding shape can be obtained even when wound at a high speed (hereinafter referred to as a good winding shape). The present invention aims to provide a film that does not scrape (hereinafter referred to as good abrasion resistance).

[0005]

The present invention is a film obtained by laminating polyester on both sides of polyester, wherein the content of particles in the laminating part is 0.5% by weight or less,
A metal-coated polyester film for magnetic media, characterized in that the surface protrusion spacing Sm of the film is 15 μm or less on both sides and the surface average roughness Ra is 10 nm or more on both sides.

The polyester constituting the present invention is not particularly limited, but ethylene terephthalate, ethylene 2,6-naphthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate It is desirable to use at least one structural unit selected from the group G as a main constituent because the abrasion resistance, the winding shape, and the output characteristics of the metal-coated magnetic medium are further improved. In addition, the polyester used in the laminated part of the present invention has the following properties when magnesium acetate, a phenyl ring-containing phosphorus compound, or antimony oxide (or germanium oxide) is present as a catalyst / heat stabilizer during transesterification or polymerization. It is desirable because the surface morphology of the invention is easily obtained. In particular, a polyester containing 85 mol% or more of ethylene terephthalate as a repeating unit is desirable because the abrasion resistance, winding shape, and output characteristics as a metal-coated magnetic medium are further improved.

However, when the film thickness is less than 6 μm, the film containing polyethylene terephthalate as a main component may lack the stiffness. In such a case, by laminating a film containing polyethylene terephthalate as a main component on both sides of a film containing polyethylene naphthalate as a main component by coextrusion, the rigidity of the film is high and the surface morphology of the present invention is obtained. It is desirable because it is easy to get caught.

[0008] The film of the present invention comprises the above composition as a main component, but may blend other polymers as long as the object of the present invention is not impaired, and may contain an antioxidant, a heat stabilizer, a lubricant, Additives for ultraviolet absorbers and antistatic agents may be added.

Further, it is effective to obtain the surface of the present invention by adding or copolymerizing a small amount of a flexible movable component to the polyester used in the laminated portion of the present invention. Here, the movable component refers to a component having a long flexible chain in the main chain and having high affinity or copolymerization with polyester, such as long-chain aliphatic dicarboxylic acid, long-chain aliphatic diol, and polyalkylene glycol. It is particularly effective to use a polyalkylene glycol such as polyethylene glycol and hexamethylene glycol. Among them, particularly, the number average molecular weight is 1,000 to 50,000, preferably 200
0 to 40000, more preferably 3000 to 3000
0 to 10% by weight, preferably 0.1 to 8% by weight of polyethylene glycol,
More preferably, it is desirable to use it in the range of 1 to 5% by weight.

In the film of the present invention, the content of the particles in the laminated portion laminated on both sides is 0.5% by weight or less, preferably 0.4% by weight or less, more preferably 0.3% by weight.
It must be: If the content of the particles is more than the above range, the abrasion resistance becomes poor, which is not preferable.

The film S of the present invention has a surface protrusion spacing Sm of 15 μm or less, preferably 13 μm or less, on both sides.
More preferably, it should be 10 μm or less. If Sm is larger than the above range on only one side,
The output as a metal-coated magnetic medium is insufficient, and the winding shape and abrasion resistance are also poor, which is not preferable. The lower limit of Sm is not particularly limited, but usually about 1 μm is a manufacturing limit.

The film of the present invention must have a surface average roughness Ra of 10 nm or more on both sides, preferably 15 nm or more, and more preferably 17 nm or more. If Ra is smaller than the above range on only one surface, the winding shape and abrasion resistance will be poor, and the durability of the magnetic surface of the metal-coated magnetic medium will be insufficient, which is not preferable.
The upper limit of the surface average roughness Ra is not particularly limited, but 100
When the thickness is less than or equal to nm, the output characteristics of the metal-coated magnetic medium are further improved, which is desirable.

The thickness of the laminated portion of the film of the present invention is not particularly limited, but the thickness is 0.05 to 3 μm, and further 0.1.
When the thickness is in the range of up to 2 μm, the abrasion resistance and the winding shape are further improved, and the side coated with the film is magnetic by the undercoat effect and the opposite side is magnetic by the show-through effect on the tape coated with the metal-coated magnetic layer. This is desirable because the surface of the magnetic layer is affected and the surface of the magnetic layer having a dense structure is formed, high output as a metal-coated magnetic medium is easily achieved, and durability of the surface of the magnetic layer is easily improved.

Further, the film of the present invention has an interlayer air flow time of 8000 seconds or less, which is measured by stacking two films,
Preferably 6000 seconds or less, more preferably 5000 seconds
If the time is less than a second, the side of the film applied to the tape coated with the metal-coated magnetic layer will have an effect on the magnetic surface due to the underlayer effect, and the opposite side will have an effect on the magnetic surface due to the show-through effect, forming a magnetic layer surface with a dense structure. This is desirable because a high output as a metal-coated magnetic medium can be easily achieved and the durability of the magnetic layer surface can be easily improved.

The polyester film laminated on both sides by coextrusion has a crystallization index ΔTcg of 10 to 10.
When the temperature is in the range of 60 ° C., preferably 20 to 50 ° C., the surface morphology of the present invention is easily obtained, and the abrasion resistance is further improved.

Further, the film of the present invention is desirable when at least 80%, and preferably at least 90%, of the projections on the surface of both surfaces are formed of polyester crystals, since the abrasion resistance is further improved. .

In recent digital recording, the recording wavelength is 0.
As a result, the thickness of the magnetic layer of the coating type magnetic recording medium is reduced. This magnetic layer has a thickness of 1.
When the thickness is 0 μm or less, the surface shape of the base film tends to affect the surface of the magnetic layer due to the underlying effect. In such a case, if a surface is formed by crystals, a dense surface with few coarse protrusions can be obtained, so that the spacing loss between the head and the magnetic layer surface can be reduced and the friction coefficient can be reduced, so that high output can be achieved. And the error rate can be reduced.

Among digital type tape recorders, there are a tape recorder that does not have a fixed head and uses a rotary head for recording and reproduction, and a tape recorder that uses only a fixed head for recording and reproduction. Examples of the former include Digital Data Storage (DDS), Digital Video Cassette (DVC) Betacam SX, etc.
An example of the latter is a digital linear tape (DL
T) and the like.

As a characteristic required for a base film used for digital, there are few coarse protrusions. Coarse protrusions with a height of 200 nm or more are 5 per 1 mm ^2.
Less than or equal to is desirable. In order to further reduce such coarse protrusions, the filter used in the extruder at the time of film formation preferably has a cut of 1 μm or less, more preferably a cut of 0.5 μm or less.

For recording and reproducing with a fixed head, a film having high rigidity in the longitudinal direction is preferable. Young's modulus (EMD) in the longitudinal direction is 5 (GPa / mm ² ).
The above is desirable, and when a film containing polyethylene terephthalate as the main component is used, the Young's modulus in the longitudinal direction (EMD) is 2 (GPD) compared to the Young's modulus in the width direction (ETD).
It is preferable that the value is higher than a / mm ² ) because the running property of the tape becomes good.

For recording / reproducing with a rotary head, a film having high rigidity in the width direction is preferable from the viewpoint of head touch, and the ETD value in this case is 5 (GPa / m).
m ² ) or more is desirable. When a film containing polyethylene terephthalate as the main component is used, the Young's modulus in the width direction (ETD) is 2 times that of the Young's modulus in the longitudinal direction (EMD).
If it is higher than (GPa / mm ² ), the output characteristics of the tape will be good.

Further, the film of the present invention, on both sides, when the ratio of the maximum surface height Rt to Ra, Rt / Ra, is 10 or less, winding shape, abrasion resistance, high output as a metal-coated tape, The magnetic surface durability is further improved, which is desirable.

Further, the film of the present invention has an average surface roughness R
The difference between the large and small planes of a is less than 5 nm, and further 4
When the thickness is less than 3 nm, particularly less than 3 nm, the winding shape, abrasion resistance, high output as a metal-coated tape, and magnetic surface durability are further improved, which is desirable.

The film of the present invention has a total thickness of 3-1.
When the thickness is 5 μm, and more preferably in the range of 4 to 12 μm, the winding form, the abrasion resistance, the high output as a metal-coated tape, and the durability of the magnetic surface are further improved, and it is easy to cope with a long tape. So desirable.

The film of the present invention, if necessary,
On at least one side thereof, a coating layer may be provided after the film forming step or during the film forming step for the purpose of improving adhesion and imparting antistatic properties.

Next, the method for producing the film of the present invention will be described.

First, in order to obtain polyester A having a crystallization index in a desirable range, which is a raw material for the laminated portion, lithium acetate, magnesium acetate, potassium acetate, phosphorous acid, phosphonic acid, phosphinic acid are used during transesterification and polymerization. Alternatively, it is effective to allow their derivatives, antimony oxide, and germanium oxide to be present. A particularly desirable combination is magnesium acetate and phosphonic acid (or a derivative thereof) and antimony oxide, and preferable examples of the phosphonic acid (or a derivative thereof) include, but are not limited to, phenylphosphonic acid and dimethylphenylphosphonate. However, the crystallization index may be within a desired range by adding a crystallization accelerator such as barium stearate to polyester produced by a commonly known method.

This polyester A is laminated on both sides of polyester B produced by a known method. After drying the polyester pellets, the polyester pellets are supplied to the known melt extruder 1 and the polyester B pellets produced by the known method and having a crystallization index larger than A by 10 ° C. or more are dried. The polyester A is laminated on both sides of the polyester B by using a three-layer manifold or a merging block, and A is fed through a slit-shaped die.
An extruded film is prepared by extruding a three-layer sheet having a / B / A configuration and cooling with a casting roll. in this case,
The method of stacking using a merging block having a rectangular merging cross section is always stable and effective for obtaining the surface morphology of the present invention.

Next, this unstretched film is heat-treated.
The method of heat treatment is not particularly limited, but it is performed using a roll made of a non-adhesive material such as Teflon or silicone before longitudinal stretching or after slightly stretching in the range of 1.01 to 2 times. Is effective for obtaining the surface of the present invention, and at this time, 0.02 to 5% is obtained by using at least two or more rolls, preferably three or more rolls.
It is extremely effective to heat treat while imparting elongation to the values of Ra on both surfaces within the range of the present invention and the difference between Ra on the front and back sides within the desired range. The heat treatment temperature and time are such that the surface temperature of the film is 120 to 230 ° C., preferably 130 to
220 ° C, more preferably 140-220 ° C,
Treatment for 0.1 to 10 seconds, preferably 0.2 to 8 seconds is extremely effective for obtaining a surface within the range of the present invention and for controlling the difference in Ra between the front and back sides within a desired range.

Next, the heat-treated film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used.
However, a sequential biaxial stretching method of first stretching in the longitudinal (longitudinal) direction and then in the width (transverse) direction is used, and either the stretching temperature in the longitudinal direction or the stretching temperature in the width direction is performed at a glass transition temperature or lower. That is, a special stretching method, in particular, a method in which the stretching temperature in the width direction is not more than the glass transition temperature is extremely effective for obtaining the surface within the range of the present invention and for controlling the difference in Ra between the front and back sides within a desired range.

Stretching in the longitudinal direction is carried out by utilizing the peripheral speed difference of the roll, the stretching ratio is 3 to 5 times, and the stretching speed is 10000.
A range of -50,000% / min is effective.

The stretching in the width direction is generally performed by using a stenter, and the stretching speed is 1000 to 20000.
% / Min is preferred. At this time, after stretching in a stenter, while being relaxed by 2 to 10%, preferably 3 to 8% with respect to the original length, 150 to 200 ° C, particularly 160 to 190 ° C,
The heat treatment for 0.5 to 60 seconds is extremely effective for obtaining the surface within the range of the present invention and for making the difference in Ra between the front and the back within a desirable range.

Further, the biaxially stretched film is further subjected to 1.3 ° C. in the longitudinal direction at a temperature higher than the above heat treatment temperature.
Stretching up to 2 times and heat-treating at a higher temperature are extremely effective for obtaining the surface within the range of the present invention and for controlling the difference in Ra between the front and back surfaces within a desirable range.

[0034]

[Method for measuring physical properties and method for evaluating effects] The method for measuring characteristic values and the method for evaluating effects according to the present invention are as follows.

(1) Average surface roughness Ra, maximum height Rt,
Projection spacing Sm The average surface roughness Ra, the maximum height Rt (peak to valley), and the projection spacing Sm were measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was determined as the average value of 20 measurements.

-Stylus tip radius: 0.5 μm-Stylus load: 5 mg-Measurement length: 1 mm-Cutoff value: 0.08 mm The definitions of Ra, Sm, Rt, etc. are given, for example, by Jiro Nara "Surface". Roughness measurement / evaluation method "(General Technology Center, 1983).

(2) Particle Content A solvent in which the polyester is dissolved but the particles are not dissolved is selected, and the particles are centrifuged from the polyester to determine the weight percentage of the particles. The particle content of the laminated portion may be obtained by peeling only the laminated portion or separated by scraping to obtain the above method, or in a secondary ion mass spectrometer, the specific element of the portion corresponding to the laminated portion It can also be determined by comparing the intensity of the secondary ion with the intensity of the secondary ion of a sample in which the concentration of the specific element is known. It is also possible to identify the type of particles by an X-ray microanalyzer or microscopic infrared spectroscopy on the cross section of the film and obtain the concentration from the detection intensity and the calibration curve of the particle concentration in each method using the particles.

(3) Thickness of Laminated Portion Generally, a method of observing a cross section of a film with an electron microscope such as a transmission electron microscope and recognizing an interface from the difference in contrast to obtain the laminated thickness, However, the present invention is not limited to this, and after the laminated portion is peeled off, the laminated thickness can be obtained using a thin film step measuring machine.

(4) Number of Protrusions Formed by Crystals A cross section of an ultrathin section was observed with a transmission electron microscope, and a black lizard portion present under the protrusions was identified by JEM2000F manufactured by JEOL.
Using X-2, acceleration voltage 100-200kV, temperature -1
A low temperature electron diffraction image was observed at 10 ° C. Total 10 at this time
The percentage of those in which the low-temperature electron diffraction image could be observed during the measurement of the 100 projections was expressed in%.

(5) Young's modulus According to the method specified in JIS-Z-1702,
Using an Instron type tensile tester, 25
It measured at 65 degreeC and 65% RH.

(6) Interlayer air flow time It was measured using a Beck smoothness tester manufactured by Toyo Seiki. Two films are placed one on top of the other, and a vacuum pump is used to reduce the pressure to 377 mmHg from the hole provided in the lower film, and the film is stopped.
At this time, air flows in between the two films and the atmospheric pressure rises. The change in the atmospheric pressure was traced, and the time from 379 mmHg to 381 mmHg was defined as the interlayer air flow time.

(7) Crystallization index ΔTcg It was measured using DSC (Differential Scanning Calorimeter) Model II manufactured by Perkin-Elmer. The measurement conditions of DSC are as follows. That is, 10 mg of a sample is set in a DSC device,
After melting at a temperature of 00 ° C. for 5 minutes, it is rapidly cooled in liquid nitrogen. The quenched sample is heated at a rate of 10 ° C./min, and the glass transition point Tg is detected. The temperature was further increased, and the crystallization exothermic peak temperature from the glassy state was defined as the cold crystallization temperature Tcc. The temperature was further increased, and the heat of fusion was determined from the melting peak. Here, the difference between Tcc and Tg (Tcc−Tg) is defined as a crystallization parameter ΔTcg.

(8) Scraping resistance The film was slit into a tape with a width of 8 mm,
Push a single blade (razor) vertically, and further 0.5mm
The film is run for a length of 200 m while being pushed in (running speed: 500 m / min, running tension: 100 g). At this time, the height of the shaved material on the film surface adhering to the tip of the single blade was read with a microscope and was taken as the shaved amount. When the amount of shaving is less than 50 μm on both sides, the abrasion resistance: excellent, 50 μm or more and 1
When it was less than 00 μm, the abrasion resistance was determined to be good, and when it exceeded 100 μm, it was determined to be defective. This value corresponds to whether or not the scraping of the magnetic surface side by a die coater or the like in the coating process causes a trouble in the process or product performance, and a defective product cannot be used.

(9) Winding shape The film after film formation is slit into a width of 1500 mm and wound on a 6-inch core. The slit speed is 500m / min,
The winding length was 10,000 m. This roll is heated at 25 ° C.
After being left for 72 hours in an atmosphere of 65% RH, the roll shape was determined according to the following criteria.

There are vertical wrinkles on the surface of the roll, or
Wrinkles on core part: × ・ Weak wrinkles on core part: △ ・ No wrinkles on roll surface or core part: ○ ○ is desirable, but △ is practically usable.

(10) Number of coarse protrusions Using a three-dimensional surface roughness meter ET-30HK manufactured by Kosaka Laboratory,
The number of protrusions having a height of 200 nm or more was measured under the following conditions, with the level of the height at which the load curve was 70% as a reference (zero).

Stylus diameter: 2 μm Measurement area: 0.1 mm ² Cutoff: 0.08 mm This measurement was repeated 10 times to obtain the number of coarse protrusions per 1 mm ² .

(11) Output characteristics (C / N) On the surface of the film of the present invention, a magnetic coating material and a non-magnetic coating material having the following compositions are multilayer coated by an extrusion coater (the upper layer is a magnetic coating material having a coating thickness of 0.1 μm, The thickness of the magnetic lower layer is appropriately changed), magnetically oriented, and dried. Then, a back coat layer having the following composition is formed on the opposite surface by a known means, and then, with a small test calender (steel / steel, 5 steps), temperature: 85 ° C., linear pressure: 20
After calendering at 0 kg / cm, it is cured at 60 ° C. for 48 hours. The raw tape was slit into a width of 8 mm to prepare a pancake. Next, a length of 200 m from this pancake was incorporated into a cassette to form a cassette tape.

On this tape, a commercially available Hi8 VTR (S
7MHz using ONY EV-BS3000)
C / N at ± 1 MHz was measured.

(Composition of magnetic paint) -Ferromagnetic metal powder: 100 parts by weight-Na sulfonic acid modified vinyl chloride copolymer: 10 parts by weight-Na sulfonic acid modified polyurethane: 10 parts by weight-Polyisocyanate: 5 parts by weight- Stearic acid: 1.5 parts by weight Oleic acid: 1 part by weight Carbon black: 1 part by weight Alumina: 10 parts by weight Methyl ethyl ketone: 75 parts by weight Cyclohexanone: 75 parts by weight Toluene: 75 parts by weight (non-magnetic lower layer) Composition of paint) Titanium oxide: 100 parts by weight Carbon black: 10 parts by weight-Na sulfonate modified vinyl chloride copolymer: 10 parts by weight Na sulfonate modified polyurethane: 10 parts by weight Methyl ethyl ketone: 30 parts by weight Methyl Isobutyl ketone: 30 parts by weight Toluene: 30 parts by weight Composition) ・ Carbon black (average particle size 20 nm): 95 parts by weight ・ Carbon black (average particle size 280 nm): 5 parts by weight ・ α alumina: 0.1 parts by weight ・ Zinc oxide: 0.3 parts by weight ・ Sulfone Acid Na-modified polyurethane: 20 parts by weight-Na sulfonate-modified vinyl chloride copolymer: 30 parts by weight-Cyclohexanone: 200 parts by weight-Methyl ethyl ketone: 300 parts by weight-Toluene: 100 parts by weight

(12) Travelability A tape slit to 1/2 inch was loaded into a DLT cassette, loaded into a DLT drive, and the entire length of reproduction and rewinding was repeated 100 times. Check if is occurring. Cassette 1
The number of windings in which these troubles occurred for 00 windings was defined as the defective rate.

[0052]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments.

Examples 1 to 8 and Comparative Examples 1 to 5 As polyester A, a transesterification catalyst was 0.1% by weight of magnesium acetate, and a polymerization catalyst was 0.1% by weight of antimony trioxide.
Polyethylene terephthalate (PE) having a crystallizing index of 35 to 50 ° C., containing 0.3% by weight of a heat stabilizer and 0.35% by weight of dimethylphenylphosphonate as a heat stabilizer, and containing substantially no particles.
T) was produced. The crystallization index was adjusted by changing the intrinsic viscosity. (Crystallization index 35 ° C: Intrinsic viscosity 0.6
5, crystallization index 50 ° C .: intrinsic viscosity 0.70).

Further, spherical silica (Example 3, Comparative Example 2) and calcium carbonate (Comparative Example 3) were also contained in predetermined amounts.

As polyester B, PET having an intrinsic viscosity of 0.65 and a crystallization index of 75 ° C. and PEN having a crystallization index of 100 ° C. were prepared by a known method. PET having the intrinsic viscosity of 0.65 and the crystallization index of 75 ° C. was used for both the laminated portion and the base layer portion of Comparative Example 4.

Each of these polymers was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours to obtain a laminated portion (polyester A),
As a base layer (polyester B), each was fed to two extruders and melted at 290 ° C.
Layers are combined and laminated by a rectangular confluent block (feed block), extruded into a sheet using an electrostatically applied casting method, cooled and solidified on a cast roll whose surface temperature is changed, and having an A / B / A configuration, An unstretched film having a three-layer structure was produced so that the layer A has a predetermined laminated thickness by changing the discharge amount.

This film is made of silicone rubber with a wall thickness of 1.
Roll heat treatment machine consisting of rolls wound at 0 mm,
The treatment temperature was changed within the range of 120 to 180 ° C. and the heat treatment was performed for 3 seconds. In Comparative Example 1, heat treatment was performed using only one roll.

These unstretched films were stretched 3.5 times in the longitudinal direction at a temperature of 100 ° C. This stretching is done with two sets of rolls.
It was done with the peripheral speed difference of Le. This uniaxially stretched film was stretched 3.5 times in the width direction at 70 ° C., which is a temperature not higher than the glass transition point, at a stretching speed of 5000% / min using a stenter, and was relaxed in the width direction at 150 ° C. Heat treated for seconds. At this time, Example 6 was heat-treated without relaxation.

Further, the biaxially oriented polyester film having different thicknesses is stretched 1.2 to 1.8 times in the longitudinal direction by utilizing the peripheral speed difference between two sets of rolls and heat-treated at 200 ° C. for 1 second. Got

In Example 1 and Comparative Example 1,
The stretching ratio in the longitudinal direction was 3.0 times, and after heat setting, the film was drawn 1.5 times in the width direction at a drawing temperature of 105 ° C. at a drawing speed of 5000% / min, and heat set at 200 ° C. for 2 seconds (each was carried out. Example 7, Comparative Example 5).

Similarly, in Example 1, in Example 1, the film forming speed was increased and the heat treatment time before stretching was 2.5 seconds.

Here, the manufacturing points of each experimental example are summarized.

[0063]

[Table 1] The surface properties of these films are as shown in Tables 2 to 5, and when the requirements of the present invention are satisfied, a film excellent in both abrasion resistance and winding form can be obtained, but otherwise, abrasion resistance is obtained. It turns out that a film that does not satisfy both the winding style is not available.

[0064]

[Table 2]

[Table 3]

[Table 4]

[Table 5] Further, the magnetic layer and the back coat layer were applied to the films of Examples 2, 4, and 7 by using a known extrusion coater, dried, cured, and then slit into a width of 8 mm and a width of 1/2 inch, respectively. The cassette was loaded and various characteristics were evaluated. However, the output characteristics were measured using a Hi8 cassette and a deck.
Table 6 shows the results.

[0065]

[Table 6]

[0066]

INDUSTRIAL APPLICABILITY According to the present invention, the surface morphology of both surfaces is set to a specific range by a special crystallization treatment and biaxial stretching under specific conditions. Therefore, it will be necessary for future support films for metal coating type magnetic recording media. A polyester film that has both abrasion resistance and winding appearance was completed. In the present invention, the film is a metal-coated magnetic medium such as 8 mm video tape, broadcast video tape, high performance audio tape,
It is useful for digital video / audio tapes, high density floppy disks, computer tapes, etc.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location // B29K 67:00

Claims (15)

[Claims] 1. A film obtained by laminating polyester on both surfaces of polyester, wherein the content of particles in the laminating portion is 0.5% by weight or less, and the surface protrusion spacing S of the film is S.
A metal-coated polyester film for magnetic media, wherein m is 15 μm or less on both sides, and surface average roughness Ra is 10 nm or more on both sides. 2. The polyester film for a metal coated magnetic medium according to claim 1, wherein an interlayer air flow time measured by stacking the films is 8000 seconds or less. 3. The crystallization index ΔTcg of polyester laminated on both sides by coextrusion is 10-6.
3. The polyester film for a metal coated magnetic medium according to claim 1 or 2, wherein the temperature is in the range of 0 ° C. 4. The metal coated polyester film for a magnetic medium according to claim 1, wherein the laminated portion has a thickness in the range of 0.05 to 3 μm. 5. The metal coated polyester film for magnetic media according to claim 1, wherein 80% or more of the surface protrusions on both sides of the film are formed of polyester crystals. 6. The metal-coated magnetic medium according to claim 1, wherein the ratio of the maximum height Rt to Ra of the film surface and Rt / Ra is 10 or less on both surfaces. Polyester film. 7. The polyester for metal coated magnetic media according to claim 1, wherein the difference between the surface having a large average surface roughness Ra and the surface having a small average surface roughness Ra of the film is less than 5 nm. the film. 8. The polyester film for a metal coated magnetic medium according to claim 1, wherein the total film thickness is in the range of 3 to 15 μm. 9. The Young's modulus EMD in the longitudinal direction is 5 (GPa / m
polyester film for metal coating type magnetic medium according to claim 1, wherein m ²⁾ or more. 10. A magnetic layer having a thickness of 1.0 μm or less provided on at least one surface of the film, and is used as a magnetic medium for recording / reproducing with a fixed head. The metal-coated polyester film for a magnetic medium according to. 11. The polyester film for metal coated magnetic media according to claim 10, wherein the Young's modulus in the longitudinal direction (EMD) and the Young's modulus in the width direction (ETD) satisfy the following formula. EMD-ETD ≧ 2 (GPa / mm ² ) EMD ≧ 5 (GPa / mm ² ) 12. A magnetic layer having a thickness of 1.0 μm or less provided on at least one side of a film, and is used as a magnetic medium for recording / reproducing with a rotary head. The metal-coated polyester film for a magnetic medium according to. 13. The polyester film for metal coated magnetic media according to claim 12, wherein the Young's modulus in the longitudinal direction (EMD) and the Young's modulus in the width direction (ETD) satisfy the following formula. ETD-EMD ≧ 2 (GPa / mm ² ) ETD ≧ 5 (GPa / mm ² ) 14. The polyester film for metal coated magnetic media according to claim 1, wherein the polyester contains 85 mol% or more of ethylene terephthalate as a repeating unit. 15. The metal-coated magnetic material according to claim 1, wherein a film containing polyethylene terephthalate as a main component is laminated on both sides of a film containing polyethylene naphthalate as a main component. Polyester film for media.