JPS583289B2 - Oriented polyester film for magnetic tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester film for magnetic tape with improved abrasion resistance and running stability.

More specifically, the present invention relates to an oriented polyester film for magnetic tape having excellent abrasion resistance, fatigue resistance, and running stability.

Polyethylene terephthalate film, polyethylene
Polyester films such as 2,6-naphthalate films are widely used in various applications including magnetic tapes and electrical applications due to their excellent properties.

One use of these polyester films is as a base for tapes used in electronic applications.

When a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, wrinkles and scratches must not occur on the surface of the film.

This is because if the film surface is scratched or wrinkled during film manufacturing, magnetic layer coating, or other handling, it is unsuitable as a base film, and even if used, the product yield will be extremely poor. It is from.

Furthermore, after being processed into a magnetic tape or the like, good abrasion resistance is also required when the tape is pulled out from a reel, cassette, etc., or wound up.

In order to improve the abrasion properties of the film, it is sufficient to improve the slipperiness by adding irregularities to the film surface. For example, inorganic fine particles may be added to the polymer used as the film raw material, or insoluble catalyst may be added to the polymer. or cause residue to be generated.

However, base films for magnetic tapes, especially base films used for video tapes, etc., are required not only to have such excellent slip properties, but also to have stable running properties.
It must also have excellent wear resistance so that it can withstand long-term use.

Magnetic tapes often come into contact with recording devices and playback devices when recording on the tape or reproducing recordings, and this contact tends to cause tape wear.

Therefore, it is desirable to provide tapes with significantly superior abrasion resistance.

The problem of wear in magnetic tapes can be broadly divided into two types.

The first is the fatigue wear type and the second is the friction wear type.

The former is caused by continuous running of a magnetic tape based on polyester film.

A magnetic layer is applied to the side of the magnetic tape where information is stored.

On the opposite side, which is not coated with a magnetic layer, contact with the equipment caused by running the tape generates powdered polyester fragments, causing temporary or permanent errors in reading the information stored in the magnetic layer.

This occurs as a result of winding the tape, and debris from the uncoated surface of the magnetic layer settles on the surface coated with the magnetic layer, causing separation from the information reading head.

This debris can be removed by cleaning operations, etc., so it appears to be only a temporary error, but in many cases,
During winding, debris enters the magnetic layer and creates dents in the tape surface, and these dents cause the read head to separate from the magnetic layer coating, causing loss of information.

On the other hand, frictional wear occurs during the film manufacturing process, when processes prior to the magnetic layer coating process are exposed to considerable frictional resistance during information reproduction, such as when the film is run between rolls rotating at different speeds, stationary roll,
When a film is run on a guide roll or the like, polyester fragments are generated in the form of white powder on the surface of the film that is not coated with a magnetic layer.

For example, when applying a magnetic layer, if the coated surface contains debris, the magnetic layer will not be applied to the portions of the film surface covered with the debris, but will remain coated on the debris.

This creates an uneven tape surface.

When a magnetic layer is applied to debris adhering to a surface that should be smooth, bumps occur, causing loss of recorded information.

In short, fatigue loss wear and friction wear must be reduced.

A film with excellent abrasion resistance is preferred because of its stable running properties.

Furthermore, when a magnetic layer is applied to the surface of the oriented polyester film to form a magnetic recording tape, it must have excellent electromagnetic properties.

In recent years, efforts and technological innovations have been made to improve the recording density per unit volume of magnetic recording tapes.

For example, these methods include reducing the thickness of the base film, reducing the thickness of the coated magnetic layer, or slowing down the running speed of the magnetic tape.

However, if the applied magnetic layer is made thinner in order to increase the magnetic recording density per unit volume, the unevenness on the film surface cannot be completely coated, resulting in deterioration of the electromagnetic properties.

It is difficult to simultaneously satisfy these conflicting properties of slipperiness, wear resistance, and electromagnetic properties.

The present inventor has arrived at the present invention as a result of intensive research into films that do not cause such problems.

That is, the present invention provides: (a) an inert substance of aluminum silicate, calcium phosphate, or silica with an average particle size of 0.8 μm or less (A) 0.01 μm or less;
~0.28% by weight; (b) 0.002% calcium carbonate (B) having an average particle size larger than that of the inert substance (A) and 1.8 μm or less;
-0.019% by weight of the oriented polyester film.

Films made of polyester containing such inert substances and stretched and oriented are characterized by extremely excellent slip properties, abrasion resistance, and running stability.

The oriented polyester film of the present invention is characterized in that the dynamic friction coefficient μk of its rough surface is in the range of 0.05≦μk≦0.18.

The polyester referred to in the present invention refers to a polymer composed of an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, etc. and a glycol such as ethylene glycol, diethylene glycol, tetramethylene glycol, neopentylene glycol, etc. It is a polymer that can be obtained by condensation.

The polyester is a polymer that can be obtained by directly polycondensing an aromatic dicarboxylic acid and a glycol.

The polyester may be obtained by directly polycondensing an aromatic dicarboxylic acid and a glycol, or may be obtained by transesterifying an aromatic dicarboxylic acid dialkyl ester and a glycol, followed by polycondensation.

Alternatively, it can also be obtained by a method such as polycondensation of diglycol ester of aromatic dicarboxylic acid.

Typical examples of such polymers include polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate.

The polymer may be a non-copolymerized homopolymer, and up to 15 mol% of the dicarboxylic acid component is a non-aromatic dicarboxylic acid component and/or up to 15 mol% of the diol component is a non-aliphatic glycol. A copolymerized polyester having a diol component may also be used.

Further, the polyester may contain additives such as stabilizers, colorants, and antioxidants, if necessary.

The oriented polyester film of the present invention has two (or more) types of inert substances added thereto in specific amounts having specific average particle diameters, and has the characteristic that the particle sizes of the two types of inert substances are different from each other.

In other words, by combining a specific combination of inert material particles in a specific amount, a film can be produced that has significantly superior slipperiness, abrasion resistance, and running stability that cannot be achieved with inert materials alone or with other combinations. The surprising fact is that it can be obtained.

Inert substances (A) include aluminum silicate, calcium phosphate and silica.

Aluminum silicate may be a fired product or a hydrated product.

Examples of the calcined aluminum silicate include calcined clay.

Examples of the hydrated aluminum silicate include waxite, kaolinite made of kaolinite crystals, kaolin, and clay.

Moreover, silica may be crystalline or amorphous.

The average particle size of the inert substance (a) is 0.8 μm or less, preferably 0.55 μm or less, more preferably 0.43 μm
The following is good.

The lower limit of the average particle size is not particularly limited, but is usually 0.1 μm.

The maximum particle size of the inert substance (A) is about 2.5 μm, and the particle size [
d (unit: μm)] The ratio preferably satisfies the following range.

2.5≧d>1.5...0~8%1.5≧d>
0.5...20-50%0.5≧d...
-40-80% At this time, the amount of the inert substance (A) added is 0.01-0.
The content is preferably 28% by weight, preferably 0.03% by weight or more, more preferably 0.05% by weight or more, and the upper limit is preferably 0.25% by weight or less.

If it deviates from these ranges, slipperiness, wear resistance and running stability will not be improved.

The average particle size of the inert substance (B) must be larger than that of the inert substance (A) and must be in the range of 1.8 μm or less.

Preferably 1.7 μm or less, more preferably 1.6 μm
m or less.

The lower limit of the average particle size is not particularly limited, but is usually 0.3 μm.

The average particle size of the inert substance (B) is preferably larger than the average particle size of the substance (A), and the average particle size ratio (B)/(
The ratio of A) is not particularly limited, but is preferably 2 to 8.

The maximum particle size of the inert substance (B) is about 10 μm, and the particle size [d
(Unit: μm)] The ratio preferably satisfies the following range.

10≧d>5...0 to 5% by weight 5≧d>
2.5・・・・・・ 2～30〃2.5≧d・・・・・・
・65-98 In this case, the amount of the inert substance (B) added is 0.002-0.019% by weight, preferably 0
．． 0.004% by weight or more, more preferably 0.006% by weight or more, and the upper limit addition amount is preferably 0.018% by weight or less.

If the amount of the inert substance (B) added is less than 0.002% by weight, the slipperiness, abrasion resistance and running stability of the film will be poor.

On the other hand, when a magnetic layer is coated on the surface of the oriented polyester film and used as a magnetic tape for video, the particle size is 1.
It is desirable that the proportion of 0≧d>5 is 3% by weight or less.

If the amount of the inert substance (B) added exceeds 0.019% by weight, the electromagnetic properties (C/N ratio) will be poor and the tape will not be suitable for use as a video magnetic tape.

As the thickness of the applied magnetic layer becomes thinner, to 10 μm or less, especially 8 μm or less, and even 6 μm or less, the inert substance (B)
The influence of the particle size distribution and amount of addition occurs significantly, and the electromagnetic properties deteriorate.

Therefore, when used as a video magnetic tape, the amount of inert substance (B) added should be 0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000.
The content is preferably 0.019% by weight or less, more preferably 0.018% by weight or less.

The base film made of polyester of the present invention can be used at low tape feed speeds (0.5 to 4
0 cm/sec) and low tension (5 to 5
Excellent slipperiness, abrasion resistance, and running stability especially under 0g).

In addition, the low tension range (5 to 50g
) refers to the tension range shown by the running system inlet tension T1 (see FIG. 1), and is based on the film width of 1/2 inch.

Therefore, if the film width is 1 inch, the low tension range is (10 to 100 g).

The width of the film used in the present invention is not particularly limited, but is usually 3/20 inch (3.8 m).
Films having a width in the range of 5 inches (127 mm) to 5 inches (127 mm) are preferably used.

When the friction coefficient μk of the base film is in the range of 0.05 to 0.25 in the low speed and low tension range as described above,
Especially when μk is in the range of 0.05 to 0.18,
It is preferable because there is little change in inlet tension and outlet tension when the film is running, and it has particularly excellent slip properties and running stability, as well as excellent abrasion resistance.

The amounts of inert substances (A) and (B) added may satisfy the conditions specified above, but it is preferable that the amount of inert substances (A) added is greater than the amount of inert substances (B) added. .

As the inert substance (A), it is also possible to use a mixture of two or three types of inert substances within a range that satisfies the conditions defined above.

The film of the present invention is characterized by inert substances (A) and (B).
) is contained in the film satisfying the conditions specified above, the abrasion resistance is dramatically improved.

Among these, films whose volumetric shape coefficients of the inert substances (A) and (B) satisfy the following range are particularly excellent in slipperiness, abrasion resistance, and running stability.

The volume shape factor fA of the inert substance (A) is less than 0.08,
It is preferable that the volume shape factor fB of the inert substance (B) is 0.08 or more.

However, the volumetric shape factor f is expressed as f=u/D3 where the maximum diameter D (μm) of the husband's inert material particle on the projection plane and the particle volume u (um3).

The lower limit of fA is not particularly limited, but is usually 0.003.

fB is preferably 0.10 or more, and its upper limit is 0.
．． It is about 4.

The inert material can be obtained in a variety of ways that can be performed by those skilled in the art, including milling and mixing operations of the additives.

For example, in the case of calcium carbonate, silica, and aluminum silicate, a slurry of ethylene glycol is prepared using a classification device (e.g., Tomoe Kogyo P-660 Super Decanter).
It can be obtained by classifying using etc.

For calcium phosphate, prepare a commercially available phosphate dispersion and grind the dispersed phosphate in a sand mill.

The dispersion can be obtained by repeating the milling operation one or more times to reduce the particle size of the additive in the slurry to the desired particle size.

In addition, the Stokes diameter is adopted as the particle size in the present invention (
(described later).

To determine the average particle size, calculate the composition ratio of the particle size (Stokes diameter), create an integration curve, and calculate the particle size shown at an integration rate of 50% as the average particle size (Stokes diameter).
μm) (described later).

In addition, it is believed that the object of the present invention can be achieved even if a small amount of inert substances (A) and (B) have particle sizes exceeding the aforementioned maximum particle diameters of 2.5 μm and 10 μm, respectively. When preparing a slurry of an inert substance industrially, it is not practical to prepare the slurry so that particles of such a particle size are not present.

The resulting inert substances (A) and (B) are added to the polyester.

It may be added before polyester polymerization or during the polymerization reaction, or it may be kneaded in an extruder when pelletizing after polymerization, or it may be added during melt extrusion into a sheet and dispersed in the extruder. However, it is preferable to add it before polymerization.

The polyester film that is the object of the present invention is a biaxially oriented film.

The film is stretched in two axial directions (for example, longitudinal and transverse directions) at a stretching temperature of (70 to 120)°C and a stretching ratio of (3 to 5).
Stretched at an area magnification of (8 to 22) times, (190 to 23
It is obtained by heat fixing at 0)°C for (1 to 30) seconds.

The stretching ratios in the biaxial directions may or may not be equal, and include methods such as longitudinal stretching, transverse stretching, re-longitudinal stretching, transverse stretching, and longitudinal stretching.

Film thickness is 3-100μm, preferably 4-50μm
A film having a film thickness of 8 to 25 μm is most preferably used.

In addition, when only one side of the film comes into contact with the metal roll, only the contacting surface contains the inert substances (A) and (B) of the present invention, and the other side contains the inert substance depending on the purpose. It is also possible to add it without adding it.

Since the oriented polyester film of the present invention has excellent abrasion resistance, it can be used in all applications for conventional polyester films, but it is most suitable for magnetic tapes that run at low speeds.

From the viewpoints of abrasion resistance, runnability, and electromagnetic properties, it is preferably used as a base film for magnetic tapes, particularly for data cartridges in computer mass storage systems, VTRs, and the like.

The method for measuring physical properties in the present invention is shown below.

1. Particle size and composition ratio of inert substance Using a Shimadzu automatic sedimentation balance, use the Stokes equation, where T: sedimentation time (sec) η: viscosity of the medium (g/cm・sec=poise) h=
Sedimentation distance (cm) G: Acceleration of gravity (980 cm/sec2) ρ: Density of inert substance (g/cm3) ρo Density of medium (g/cm3) d: Particle size of inert substance (diameter/cm) Calculate the sedimentation time corresponding to each particle size using the method, find the sedimentation time range corresponding to each particle size range, calculate the weight of inert material within that sedimentation time range, and calculate the total inert material weight. The ratio to that amount is expressed as a percentage and is used as a composition ratio.

2. Determine the composition ratio using the method described in Average Particle Size Measurement Method 1, create an integration curve that integrates the particles in order from larger to smaller (100% at particle size 0 μm), and calculate the particle size shown at an integration rate of 50%. is the average particle size (μm).

3. Volume shape factor f This is an arithmetic average value calculated based on actual values of particles taken from microscopic photographs.

The volumetric shape factor f is calculated according to the following formula.

"D = Maximum diameter on particle projection plane (μm) U: Volume of particle (μm8)" 4. Coefficient of dynamic friction μk As shown in Figure 1, the surface of a polyester film roughened at 25°C and 60% relative humidity was
27 Fixed rod (surface roughness 0.3S) angle θ = (152)
/ (180) π radians (152°) per second
Move and rub at a speed of 5cm/sec.

The dynamic friction coefficient μk is calculated using the following formula from the exit tension T2 (detected by the exit tension detector 10) g when the tension controller 2 is adjusted so that the inlet tension T1 is 30 g. μk).

At this time, θ=152° (=(152)/(180)π radians) was used.

The smaller μk is, the better the sliding property is.

5. Dynamic friction coefficient fluctuation Δμk is expressed as Δμk=μk (dynamic friction coefficient when traveling 30 m)−μk (dynamic friction coefficient at initial traveling stage), and it is assumed that the smaller Δμk is, the more stable the running performance is.

6. The abrasion evaluation film was slit into 1/2" width, then passed through a winder and rubbed against a metal guide roll installed in the middle.
The depth and width of scratches that occur on the film during running are visually judged with the naked eye using an aluminum vapor-deposited sample, and are expressed in the following ranks.

1 There are no scratches on the film surface and it exhibits excellent frictional resistance.

2 Slight scratches occur, but it can withstand use.

3 More scratches and deeper than 2, but still usable (normal).

4 A lot of scratches occur (slightly bad).

5 The scratches are deep and numerous and cannot be used.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples for any reason.

The oriented polyester film that is the base material of the magnetic tape of the present invention has particularly excellent running performance when the magnetic tape is fed at low speed (0.5 to 40 cm/sec) under extremely low tension (5 to 50 grams). It has the unique properties of being soft and slippery.

However, it is not necessarily suitable as a base film for magnetic tapes for storage tapes of electronic computers that are transported at high speeds.

This seems to be because the slipperiness of the film, which is based on minute protrusions and irregularities on the film surface, changes considerably with the running speed of the tape.

Protrusions of about 1 μm or more on the film surface have the effect of reducing the coefficient of dynamic friction when running at high speeds, but conversely make the film difficult to slip when running at low speeds.

Example 1 Manganese acetate 40 mmol%, antimony trioxide 20 mmol%, as a catalyst based on dimethyl terephthalate,
40 mmol% of phosphorous acid was added to carry out the transesterification reaction, and then the particle size [d (unit: μm)] was obtained as an inert substance (A).
] Kaolinite whose ratio is shown below d≦0.5μm...62.4% 0.5μm<d≦1.5μm...34.7%1
．． 5μm<d≦2.5μm・・・2.9% (average particle size 0.43μm, volume shape coefficient fA=0.063) as 0.15% by weight and inert substance (B) particles Diameter [d
(Unit: μm)] Heavy calcium carbonate (calcite crystal) whose ratio is shown below d≦2.5μm...86
．． 2% 2.5μm<d≦5μm・・・11.0%5μm
<d≦10μm・・・2.8% (average particle size 1.6
μm, volumetric shape coefficient fB = 0.24) by 0.015% by weight and polycondensation reaction, polyethylene terephthalate with [η] 0.65 (value measured at 25°C using O-chlorophenol as a solvent) I got it.

Dry this polyethylene terephthalate at 160°C,
The mixture was melt-extruded at 280°C and rapidly solidified on a casting drum kept at 40°C to obtain an unstretched film.

The unstretched film was sequentially biaxially stretched at a longitudinal stretch ratio of 3.5 times and a transverse stretch ratio of 4.0 times, and then a biaxially oriented film with a thickness of 25 μm was obtained at a heat treatment temperature of 215° C.

In this example, the polyester film contained an inert substance (
A) average particle diameter 0.43 μm, volume shape coefficient fA=
The film contains 0.063 kaolinite and calcium carbonate particles having an average particle size of 1.6 μm and a volume shape coefficient fB=0.24 as an inert substance (B), and thus satisfies the present invention.

Table 1 shows the dynamic friction coefficient μk and Δμk at this time.

It is clear from the table that the running performance and running stability are extremely good.

Next, the abrasion resistance of the film was evaluated, and as shown in Table 1, it was at the highest level of rank 1, indicating that the film had excellent abrasion resistance.

Examples 2 to 5, Comparative Examples 1 to 4 In Example 2, 0.15% by weight of the kaolinite used in Example 1 was used as the inert substance (A), and as the inert substance (B), Precipitated calcium carbonate (aragonite crystal) whose particle size ratio is shown below d≦2.5 μm...
...88.3% 2.5μm<d≦5μm...1.05%5μm
<d≦10μm・・・1.2% (average particle size 1.5
5μ, volumetric shape coefficient fB=0.08) was added in an amount of 0.015% by weight.

Example 3 is a precipitated calcium carbonate (aragonite crystal) whose particle size ratio is shown below using 0.15% by weight of kaolinite as the inert substance (A) used in Example 1 and as the inert substance (B). ≦2.5μm...87.6% 2.5μm<d≦5μm...10.3%5μm
<d≦10μm・・・2.1% (average particle size 1.6
μ, volumetric shape factor fB=0.07) 0.015% by weight
Added.

In Example 4, 0.015% by weight of calcium carbonate as the inert substance (B) used in Example 1 was used as it was, and calcium phosphate d≦0. 5μm・・・63.3% 0.5μm<d≦1.5μm・・・34.9%1
．． 5 μm<d≦2.5 μm 1.8% (average particle diameter 0.41 μm, volume shape coefficient fA=0.060) is added in an amount of 0.15% by weight.

In Example 5, 0.015% by weight of calcium carbonate as the inert substance (B) used in Example 1 was used as is, and silica d≦0.5 μm having a particle size ratio shown below as the inert substance (A) was used as the inert substance (A). ...64.2% 0.5μm<d≦1.5μm ...33.9%1
．． 5 μm<d≦2.5 μm 1.9% (average particle size 0.42 μm, volume shape coefficient fA=0.061) was added in an amount of 0.15% by weight.

In Comparative Examples 1 and 2, only 0.1% by weight and 0.25% by weight of kaolin, the inert substance (A), was added alone without adding the inert substance (B) of Example 1. be.

In Comparative Examples 3 and 4, the inert substance (A) of Example 1 was not added, and only the inert substance (B) calcium carbonate was added at 0.0
0.08% by weight and 0.015% by weight were added individually.

Furthermore, Examples 2 and 3 contained the inert substance (B), and Example 4
Polyethylene terephthalate oriented films were obtained using the same additive amounts and manufacturing methods as in Example 1, except that the inert substance (A) and No. 5 were changed.

Examples 1 to 3 are combinations in which the inert substances (A) are the same but the inert substances (B) have different volume shape coefficients.

As shown in Table 1, the friction evaluation results are as follows: Example 1 was ranked 1, Example 2 was ranked 2, Example 3 was ranked 3, and Example 3 was ranked 3.
Examples 4 and 5 were ranked 1.

Moreover, Comparative Examples 1 to 4 were ranked 5, and it was found that Examples 1 to 5 were superior in abrasion resistance compared to Comparative Examples 1 to 4.

As can be understood from these results, the oriented polyester film of the present invention has excellent slip properties, running stability, and abrasion resistance.

In particular, when the inert material (A) has a volume shape coefficient of less than 0.08 and the inert material (B) has a volume shape coefficient of 0.08 or more, excellent wear resistance, slipperiness, and running stability are achieved. You can obtain a film.

Examples 6 to 11, Comparative Examples 5 to 6 In Examples 6 to 11, Example 1 was used as the inert substance (A).
The amount of kaolinite used in was 0.01, 0.03,
0.05, 0.10, 0.25 and 0.28% by weight, respectively, and the heavy calcium carbonate (calcite crystal, average Particle size 1.6μm, volume shape factor fB=0.2
4) was added in an amount of 0.015% by weight, and a polyethylene terephthalate oriented film was obtained in the same manner as in Example 1.

In Comparative Examples 5 and 6, Example 1 was used as the inert substance (A).
Or the added amount of kaolinite used in 6 to 11 is 0.0
A polyethylene terephthalate oriented film was obtained in the same manner as in Examples 1 or 6 to 11, except that the same amount of calcium carbonate as the inert substance (B) was added.

Table 1 shows the running performance and wear performance evaluation results.

As is clear from Examples 6 to 11 and Comparative Examples 1 to 4, the film of the present invention in which two kinds of inert substances were added together has abrasion resistance that could not be achieved with conventional films containing inert substances. , has excellent effects on slipperiness and running stability.

Also, from comparison with Comparative Examples 5 and 6, it is necessary that the amount of the inert substance (A) added is 0.01 to 0.28% by weight, and if it deviates from this range, no improvement in wear resistance can be expected. .

The runnability and abrasion evaluation results in Table 1 were evaluated together, and ◎ was very good, ○ was good, ``fair'' was enough to withstand use, and △ was slightly inferior to normal. and those that cannot be used at all are indicated as X in the evaluation column.

Examples 12 to 17, Comparative Examples 7 to 9 In Examples 12 to 17, the amount of the inert substance (B) added in Example 1 was 0.002, 0.004, 0.006, and 0.01.
The amounts were changed to 0, 0.018, and 0.019% by weight, respectively.

Comparative Examples 7 to 9 were prepared in the same amount and method as in Example 1, except that the amount of inert substance (B) added in Example 1 was changed to 0.0015, 0.020, and 0.025% by weight. A polyethylene terephthalate oriented film was obtained.

Table 2 shows the running properties, abrasion performance evaluation results, and overall evaluation of these films.

Next, the magnetic powder coating shown below was applied using a gravure roll, and the magnetic coating layer was smoothed using a doctor knife to form magnetic layers of various thicknesses (10 μm to 6 μm).

While the magnetic paint was still dry, it was magnetically oriented using a conventional method, and then placed in an oven for drying and curing.

Furthermore, the coating surface was made uniform by calendar processing, and 1/2
An inch-wide videotape was wound on a reel using an HR3300 deck manufactured by Victor Corporation of Japan, and various electromagnetic conversion characteristics were examined using a synchroscope at normal speed.

The number of dropouts was counted using an IDC2 model manufactured by Japan Automatic Control Co., Ltd., with the range set to a width of 1.5 μsec and a depth of 18 dB.

We also considered color noise by adding a color bar.

Composition of magnetic paint - γ-Fe2O3 powder 100 parts by weight - Eslec A (manufactured by Sekisui Chemical, salt-vinyl acetate copolymer) 16 - Hiker 1432J (manufactured by Nippon Zeon, butadiene acrylonitrile copolymer) 11 - Lecithin
1. Carbon
8〃・MEK
100 parts by weight・MIBK 100〃
・Additives (lubricant, silicone resin) 0.15〃Example 12~
17 and Comparative Examples 7 to 9, when the amount of the inert substance (B) added is in the range of 0.002 to 0.019% by weight, the slipperiness, running stability, abrasion resistance, and electromagnetic properties of the film are improved. [VTR head output (frequency characteristics), color noise (C/N ratio), and dropout (D/0 number)] can be obtained.

The films of Comparative Examples 8 and 9 have excellent slip properties, running stability, and abrasion resistance, but have poor electromagnetic properties and cannot be used as magnetic tapes.

At the end of Table 2, base film evaluation (slip properties, running stability, abrasion resistance) and magnetic tape evaluation (electromagnetic properties, color noise, dropout) were evaluated and entered in the overall evaluation column.

Here, the evaluation marks are ◎ for very good, ○ for good, fair for use (fair), △ for slightly worse than average, and × for not at all usable.

For Examples 1 to 11 and Comparative Examples 1 to 6, a magnetic layer was coated as described above and evaluated as a magnetic tape, and a comprehensive evaluation was performed in conjunction with the evaluation as a base film.As a comprehensive evaluation, Examples 1, 4, 5, 8 to 10 were ⊚, Examples 2, 7, and 11 were ◯, and Examples 3 and 6 were ◯ to ◯, indicating that the film of the present invention was sufficiently usable.

On the other hand, Comparative Examples 1 to 4 were rated x, and Comparative Examples 5 to 6 were rated Δ, meaning they were unusable.

Examples 18-21, Comparative Examples 10-12 Average particle size 0 used as the inert substance (A) in Example 1
．． Instead of kaolinite with a volume shape factor fA of 43 μm and 0.063, average particle diameters of 0.31, 0.40, and 0.55 were used.
, 0.8 μm, volumetric shape factor fA=0.05-0.07
The same procedure as in Example 1 was conducted except that kaolinite was used.

Comparative Examples 10 to 12 have an average particle size of 1 as the inert substance (A).
．． 0, 1.2 and 1.5 μm, volumetric shape factor fB=0.
06 to 0.075.

As shown in Examples 18 to 21 and Comparative Examples 10 to 12 in Table 3, the average particle size of the inert substance (A) must be 0.8 μm or less, and if it exceeds 0.8 μm, it becomes abrasive. I can understand being inferior.

In the same manner as Examples 1 to 11 or Comparative Examples 1 to 6, a magnetic layer was coated and evaluated as a magnetic tape, and the evaluation as a base film (slip properties, running properties, abrasion resistance) and overall When evaluated, Examples 18 to 20 were evaluated as ◎, Example 21 was evaluated as positive, Comparative Examples 10 and 11 were evaluated as △, and Comparative Example 12 was evaluated as ×.

Examples 22 to 26, Comparative Examples 13 to 14 Heavy calcium carbonate (calcite crystal) with an average particle diameter of 1.6 μm and a volume shape coefficient fB = 0.24 used as the inert substance (B) in Example 1 Instead of, the average particle size is 0.9
, 1.2, 1.6, 1.7, 1.8 μm, volume shape coefficient fB = 0.15 to 0.20. went.

Comparative Examples 13 to 14 have average particle diameters of 2.0 and 3.0 μm as the inert substance (B), and volume shape coefficient fB = 0.18 to 0.
．． This is the case of 20.

As shown in Examples 22 to 26 and Comparative Examples 13 to 14 in Table 4, the average particle size of the inert substance (B) must be 1.8 μm or less, and if it exceeds 1.8 μm, it is abrasive. It is understood that it is inferior to

From the above results, the oriented polyester film of the present invention has excellent abrasion resistance.

In addition, a magnetic layer was coated in the same manner as Examples 1 to 11 and Comparative Examples 1 to 6, and evaluation as a magnetic tape was performed, and a comprehensive evaluation was performed including the evaluation as a base film: Examples 22 to 24 were ◎ , Example 25 was evaluated as ○, Example 26 was evaluated as positive, Comparative Example 13 was evaluated as △, and Comparative Example 14 was evaluated as ×.

From the above results, it was revealed that the film of the present invention is an oriented polyester film for magnetic tapes that has excellent slip properties, running stability, abrasion resistance, and electromagnetic properties.

Note: The volumetric shape factor f varies depending on the manufacturing method and production area of the inert material, but generally falls within the following value range.

(1) Aluminum silicate [calcinated aluminum silicate (
calcined clay), hydrated aluminum silicate (silicate, kaolinite, kaolin clay)] silica, etc. f=0.0
Approximately 05 to 0.12 (2) Calcium phosphate f=0.0
Approximately 03 to 0.20 (3) Calcium carbonate Precipitated calcium carbonate Minimum (aragonite crystal) f = 0.005 to 0.10 Precipitated calcium carbonate (paterite crystal) f = 0.15 to 0.30 Precipitated calcium carbonate (calcite crystal) f=0.18~0.40 Therefore
f = 0.005-0.40 Heavy calcium carbonate (crude limestone) f = 0.08-0.30 Heavy calcium carbonate (chalk) Light calcium carbonate f = 0.01-0.30

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a tape base inspection machine that measures the coefficient of dynamic friction μk of a film rough surface. In the figure, number 1 is the unwinding reel, 2 is the tension controller, 3, 5, 6, 8, 9, 11 are the free rollers, 4
is the tension detector (inlet), 7 is the SUS27 fixing rod (
20mmφ outer diameter), 10 is a tension detector (outlet),
Reference numeral 12 indicates a guide roller, and reference numeral 13 indicates a take-up reel.

Claims (1)

[Claims] 1. (a) An inert substance of aluminum silicate, calcium phosphate, or silica having an average particle size of 0.8 μm or less (A) 0.
01 to 0.28% by weight; (b) the average particle size is larger than the inert substance (A);
and 0.002 to 0 calcium carbonate with a size of 1.8 μm or less
．． An oriented polyester film for magnetic tape containing 0.019% by weight. 2. The oriented polyester film for magnetic tape according to claim 1, wherein the dynamic friction coefficient μk of the film surface is 0.05≦μk≦0.18.