JPS61112629A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To enhance the running characteristics and electromagnetic conversion characteristics of a magnetic recording material by specifying the surface roughness (TAR) value of a film as well as projection number (PCC) value per unit area at the center of the film. CONSTITUTION:Additive for a magnetic tape base material of polyester are selected according to uses in such a way that TAR value (in mum) for surface roughness and projection number (PCC) value (number/mm<2>) are within ranges to meet the relationships TAR<0.015 and PCC>=800. The magnetic tape base material comes to have excellent processability and excellent running characteristics. Therefore, even when it is repeatedly used as high-grade magnetic tape for video, the increase in frictional coefficient is very small. Biaxially oriented polyester films having electromagnetic conversion characteristics can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to biaxially oriented polyester films. More specifically, the present invention relates to a biaxially oriented polyester film that has excellent running characteristics and electromagnetic conversion characteristics, especially in magnetic recording materials.

(Prior Art) Polyesters such as polyethylene terephthalate are generally used for textiles, molded products, and other applications due to their excellent physical and chemical properties.

It is widely used in a variety of applications, including magnetic tape, photography, capacitors, and film for mounting.

When these films are used, their slipperiness and abrasion customization are major factors that determine the workability of the film manufacturing process and processing process in each application, as well as the quality of the product. In particular, when applying a magnetic layer to the surface of a polyester film and using it as a magnetic tape, friction and abrasion between the coating roll and the film surface during application of the magnetic layer are extremely severe.
Wrinkles and scratches on the film surface are likely to occur. In addition, the film after applying the magnetic layer is slit to create an audio
Even after being processed into video or computer tapes, significant friction and abrasion occurs between the guide parts, playback heads, etc. when pulling out from a reel or cassette, winding it up, or performing other operations, resulting in scratches and distortion. Further, white powdery substances are deposited due to scratching of the surface of the polyester film, which is often a major cause of missing magnetic recording signals, that is, dropouts. In addition, when used repeatedly as a magnetic tape, the coefficient of friction between it and the metal guide roller increases with the number of times it is used. and the guide roller,
The so-called squeal may occur, and the driving characteristics may deteriorate.

Generally, in order to improve the running characteristics of a film such as slipperiness and abrasion resistance, a method is adopted in which the contact area between the film and guide rolls etc. is reduced by adding unevenness to the surface of the film. The formation method includes a method in which all insoluble particles are precipitated from the polymer catalyst residue used for film thickness, titanium dioxide, kaolinite, etc.
talc.

A method is used in which particles insoluble and inert to polyester, such as silica and carbonic acid, are added. Generally, the larger the particle size of these raw polymer particles, the greater the effect of improving slipperiness, but for precision applications such as magnetic tape, especially video, it is important that the particles are large. The unevenness on the surface of the film needs to be as fine as possible because it itself can cause defects such as dropouts. However, it is currently extremely difficult to satisfy all of these contradictory characteristics at the same time.

(Problems to be Solved by the Invention) It is an object of the present invention to particularly aim at the processability of Kf12 when a biaxially oriented polyester film is used as a base material for a magnetic tape.
Another object of the present invention is to provide a two-wheel oriented polyester film that has extremely good running properties even after repeated use many times, and has good electromagnetic conversion characteristics.

(Means for Solving the Problems) As a result of intensive research on polyester films that satisfy the above-mentioned objectives, the present inventors have found that the surface roughness TAR value (unit: μm) in a specific range and the surface roughness Number of protrusions per unit area on the center plane PCC value (unit value/-)
A biaxially oriented polyester film that satisfies the following two formulas (%) at the same time has excellent electromagnetic conversion characteristics and special running characteristics,
We have arrived at the present invention by discovering that it is particularly suitable for use in video ring-opening high-grade magnetic tapes.

The surface roughness TAR value and protrusion count PCC value referred to in the present invention are each measured by the following methods.

TAR value: The film surface was measured using a stylus type three-dimensional surface roughness meter (SE-3AK) manufactured by Koita Research Institute, with a needle radius of 2 μm.
, under a load of 70 g, with a cutoff value of 0.25 Ell in the longitudinal direction of the film, measured over a reference length of 1 my, and data gold quantization width of 0.0 in the height direction every 2 μm.
0312 μm and is imported into an external storage device. Such measurements were carried out 150 times continuously at 2 μm intervals in the lateral direction of the film, and 0.3 fl in the lateral direction of the film was measured.
Measure across the width. The data in the height direction at this time is h (i, j) (i = 1 ~ 500. j = 1 ~ 150)
When the time comes, we calculate the linear equation and express the result in μm units.
@Average Roughness].

(IV) PCC value: The number of protrusions with a height of 0.00625 μm or more from the reference surface having the reference height SH when calculating the TAR value expressed by the following formula is 1 - The symbolic symbol of this place is FCC [Heater Count Tatami At Betsu Center Working Plane].

Polyester film 'fttlt composition in the present invention
The polyester is one in which 807 points or more of its repeating units consist of ethylene terephthalate, and other copolymerized components include isophthalic acid, p-β-oxVethynebenzoic acid, and 2,6-naphthalene. dicarboxylic acid, 4.
4'-Shika〃Poke S//l/diphenyl, 4.4'
-Cicapoxy~benzophenone, bis(4-capboxyVlvphenyp)ethane, adipic acid, sepacic acid,
Examples include carbon i components such as 5-sodium sulfoisophthalic acid. Maku Glyco μ component is propylene glycol.

Butanedio-〃, neopentyl glycol, diethylene glyco-A/, S/chlorhexanedimethanol-/I/.

Ethylene oxide adducts of bispheno-1vA and the like can be arbitrarily selected and used. In addition, there are small amounts of amide bonds and urethane bonds as copolymer components.

It may contain an ether bond, a carbonate bond, etc.

The method for producing the polyester includes a so-called direct polymerization method in which aromatic cicaN-bonic acid and glycol are directly reacted;
Any method of brewing can be applied, such as the so-called transesterification method in which dimethyl ester of an aromatic dicarboxylic acid and glycol are transesterified.

By selecting additives and the like so that the TAR value and PCC value determined by the above measurement method fall within the range of the present invention, processability and running customization are extremely excellent.

In particular, it is possible to obtain a biaxially oriented polyester film that exhibits extremely small increase in friction coefficient even when used nine times as a high-grade magnetic tape for video and has good occupancy conversion characteristics.

Generally, as the TAR value of the bulk surface roughness increases, p
The cc value also tends to increase, but the trends are not necessarily consistent and may be reversed. When the surface roughness TAR value of the film is greater than 0.015,
It is relatively easy to set the PCC value to 800 or more,
Although it is easy to obtain sufficient runnability, when used for a magnetic tape and a video ring-opening high-quality tape, the signal-to-noise ratio (S/N) is not good. On the other hand, TAR value is 0.0
Even if it is less than 15, if the PCC value is less than 8oo, the electromagnetic conversion characteristics are good, but sufficient running characteristics cannot be obtained.

On the other hand, although there is no particular lower limit to the TAR value, if the TAR value is about 0.003 or less, it is practically difficult to increase the PCC value to 800 or more.

There is no particular upper limit set for the PCC value either.

If the TAR value is less than 0.015, it is practically difficult to set it to 3000 or more.

From this point of view, the TAR value is less than 0.015 and the PCC value is 800 or more, preferably the TAR value is 0.0.
Therefore, when using a polyester film as a magnetic tape substrate, the TAR value (unit: μnt) indicating the surface roughness and the protrusion number PCC value (unit: pieces/-) are of the first order. A range that simultaneously satisfies the two formulas (%) has excellent running characteristics and good electromagnetic conversion characteristics. More preferably TAR value and PC
The range in which the C value and the following two formulas (1) are satisfied at the same time is determined.

The rough surface referred to here refers to a surface that is more rough between the front and back of the film. Therefore, only the rougher surface satisfies the range specified in the claims, and the other surface does not satisfy the nine ranges specified in the claims. In any case, the surface roughness may be equal to or smoother than that of the rough surface.

The method for producing the polyester film in the present invention is not particularly limited and may be arbitrary; for example, the TAR value is adjusted by the average particle diameter of the added inert inorganic or organic particles and the amount added, The FCC value can be adjusted by adjusting the shape of the added particles, the amount added, the particle size distribution, etc. In addition, in order to arbitrarily adjust the TAR value and PCC value, if necessary, two or more types of inert inorganic or organic particles may be made to exist simultaneously, or insoluble particles may be added from the polymer catalyst residue used as the film raw material. It is also possible to use the method of precipitating the particles alone or to co-exist them with inert inorganic or organic particles.

In the method of adding inert inorganic or organic particles to a polyester in the present invention, they can be added at any stage in the polyester manufacturing process, but it is particularly preferable to add them before the initial condensation is completed. The fine particles may be added to the polyester/L' manufacturing process either in the form of a slurry or in the form of a powder, but the scattering of a single particle must be prevented.

From the viewpoint of improving supply accuracy and uniformity, it is preferable to add ethylene glycol-A/(
EG) It is preferable to add it as a slurry containing t- as the main component. When fractionating the slurry, it is necessary to perform uniform fractionation so as to reproduce the original primary particles of each particle as much as possible. Also to obtain particles of a given average particle size.

It is also possible to adopt pulverization treatment or classification operation of commercially available fine particles.

In addition, when adding the inert inorganic or organic particles as a slurry to the polyester control process, two types of inert inorganic or organic particles may be added at the same time,
It may also be added separately.

If they are added at the same time, they may be added from separate supply ports, or both slurries may be mixed uniformly before being added to the polyester manufacturing process.

The polyester film that is the object of the present invention is a biaxially oriented film. The film is preferably stretched in biaxial directions (for example, longitudinal and transverse directions) at a stretching ratio of 2 times or more.

If the film is used in such a way that only one side of the film comes into contact with the metal roll, inert inorganic or organic particles are contained only on the contacting surface to achieve the surface shape of the present invention, and the other side is used for the purpose. Depending on the situation, inert inorganic or organic particles may be included.

It may be a separate layer that does not contain it.

As mentioned above, the film of the present invention is particularly preferably used as a base film for magnetic tapes, but is not limited thereto, and can be widely applied to other fields such as electrical applications and deposition films. be able to.

(Example) Next, Examples and Comparative Examples of the present invention will be shown. All parts in the examples mean parts by weight unless otherwise specified.

In addition, the measurement method used is shown below.

(1) Processability of the film A tape roll made by slitting the film into narrow widths is rubbed against a metal guide row at high speed.

When running for a long time, the magnitude of the tape tension after rubbing against the guide roll and the amount of white powder generated on the guide roll surface are evaluated on a five-point scale for a constant supply tension, and the following rankings are used.

(a) Smoothness Grade 1: High tension (many scratches) Grade 2: Slightly high tension (quite a lot of scratches) Grade 3...
Medium tension (scratches and scuffs) Grade 4... Tension is slightly low (no scratches) Grade 5...
・Low tension (no scratches at all) (B) Abrasion resistance 1st grade...very white powder generation 2nd grade...a lot of white powder generation 3rd grade...some white powder generation 4th grade...no white powder generation Grade 5: No white powder generation.In an atmosphere of 65%, the rough side of the polyester film was placed in the guide bin of a commercially available home VTR at an angle of 3/4π (
(Unit: Fujian), apply a constant load of 50 grams of tension, and move the crank at an angular velocity (3) Average particle size The value of the cumulative 50 points in the equivalent sphere diameter distribution obtained using a centrifugal sedimentation type particle size distribution measuring device manufactured by Ifr manufactured by Shimadzu. Use.

(4) Magnetic paint polyester A/Ji Jl! with the following composition on one side of the polyester film with electromagnetic conversion characteristics. 30 parts Polyurethane resin 30 # Vinyl chloride vinyl acetate copolymer resin III 4ON magnetic powder 400 Dispersant 4I Antistatic agent 20 parts by weight Lubricant 10 Apply N, make the surface mirror-like by calendering, 1 A videotape was obtained by slitting the tape to a width of /2 inches. To measure the signal-to-noise ratio, we used a Kikushibaku TG-7/1 type NTSC TV test signal generator and a 925D/1 type NTSC cuff video noise measuring device.
N is evaluated in three stages and expressed as a first-order ranking.

1st class: OdB or less 2nd class: 0 to +2 dB 3rd class: +2 dB or more Example 1 Process of directly esterifying terephthalic acid and ethylene glycol by a conventional method, firstly performing polycondensation, and producing polyethylene terephthalate. Odor, silica particles with an average particle size of 0.04 μm - 0 for the polyethylene terephthalate
．． 25% by weight of calcium carbonate and 0.05% by weight of calcium carbonate having an average particle size of 0.45 μm) t-IC was added to obtain polyester # containing fine particles. The obtained polyethylene terephthalate was then extruded at 285°C, and
Longitudinal stretching at a stretching ratio of 3.5 times at 95°C, and 3.5x at a stretching ratio of 3.
A biaxially stretched polyester film having a thickness of 15 μm was obtained by transverse stretching at 6@ and heat treatment at 220° C. for 10 seconds. Table 1 shows the physical properties of the obtained film. The obtained film has extremely excellent running properties and good electromagnetic conversion properties, and is a highly desirable product for magnetic tapes, especially for video ring-opening high-grade magnetic tapes. .

Example 2 The fine particles to be added were 0.15% by weight of kaolinite particles with an average particle size of 0.2 μm and 0.45 μm in average particle size.
A polyethylene terephthalate film was obtained in exactly the same manner as in Example 1, except that the amount of 7n calcium carbonate particles was changed to 0.03% by weight. The physical properties of the obtained film are shown in Table 1.

The obtained film has extremely excellent running characteristics and good electromagnetic conversion characteristics, and is suitable for use in magnetic tapes.

It can be seen that the film has very desirable qualities, especially as a film for video ring-opening high-grade magnetic tapes.

Comparative Example 1 A polyethylene terephthalate film was obtained in exactly the same manner as in Example 1, except that the fine particles to be added were changed to 0.20 weight percent of calcium carbonate particles having an average particle size of 0.15 μm. Table 1 shows the physical properties of the obtained letter film. Although the obtained film has good electromagnetic conversion characteristics, its running durability is extremely poor due to its low PCC value, and it does not have sufficient quality as a film for video ring-opening high-grade magnetic tapes.

Comparative Example 2 The fine particles to be added were kaolina with an average particle size of 0.7 μm)
A polyethylene terephthalate film was obtained in exactly the same manner as in Example 1 except that the amount was changed to 20% by weight. Table 1 shows the physical properties of the obtained film. The obtained film did not satisfy both running characteristics and electromagnetic conversion characteristics, and did not satisfy sufficient quality as a film for high-grade magnetic tape.

Comparative Example 3 The fine particles to be added were 25% by weight of kaolinite tO with an average particle size of 0.35 μm and an average particle size of 0.60 μm.
A polyethylene terephthalate film was obtained in exactly the same manner as in Example 1, except that the carbonate power of m was changed to 0.10% by weight.

Table 1 shows the physical properties of the obtained film. Although the resulting film exhibits good running properties, it has poor electromagnetic conversion properties due to its large TAR value, and does not have sufficient quality as a film for high-grade magnetic tapes such as those for videos.

(Effects of the Invention) As described above, the nine films obtained according to the present invention have extremely excellent running characteristics, in particular, the amount of white powder generated and the occurrence of scratches in the magnetic tape manufacturing process are extremely small, and even after repeated use, it does not cause abrasion. This has the effect that the increase in coefficients is very small, and the electromagnetic conversion characteristics can also have a high signal-to-noise ratio (S/N).

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a tape tester for measuring the running performance of a film on a rough surface. Each part will be briefly explained below. 1: Crank 2.4.6.8: Free roll 3.7: Tension detection device 9: Load 5: Commercially available VTR guide pin

Claims (3)

[Claims] (1) A biaxially oriented polyester film having at least one surface roughened, the surface roughness TAR value (unit: μm) of the roughened surface and the number of protrusions per unit area PCC on the center surface of the surface roughness. The value (unit piece/mm^2) is the following two formulas TAR<0.015・・・・・・・・・・・・・・・(
I) PCC≧800・・・・・・・・・・・・・・・
A biaxially oriented polyester film that satisfies (II) at the same time. (2) TAR value (unit: μm) and PCC value (unit: piece/
mm^2) is the following two formulas TAR≦0.012・・・・・・・・・・・・・・・(
I)'PCC≧1200・・・・・・・・・・・・
The biaxially oriented polyester film according to claim 1, which satisfies (II)' at the same time. (3) The biaxially oriented polyester film according to claim 1 or 2, wherein the biaxially oriented polyester film is a magnetic recording material.