KR19990070959A - Biaxially Oriented Polyester Film - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester film. Biaxially oriented polyester film according to the present invention, which has an average particle diameter of 0.1 to 3.0 µm in polyester resin, and 0.1 to 2.0% by weight of cubic magnesium oxide particles are added to the polyester resin to form protrusions on the surface thereof. It is suitable for magnetic recording media because it has the advantages of winding and abrasion resistance as well as electronic characteristics and running characteristics.

Description

Biaxially Oriented Polyester Film

The present invention relates to a polyester film, and more particularly to a biaxially oriented polyester film for a magnetic recording medium excellent in running, winding and wear resistance.

Polyester, represented by polyethylene terephthalate (PET), has a stable chemical structure and mechanical strength, and is excellent in heat resistance, durability, chemical resistance, and the like, and is used for capacitors, medical, industrial, packaging, photo film, labels, and magnetic. It is used for various purposes, such as a base film of a recording medium.

However, the polyester film has a problem in post-processing or product characteristics due to wear of the surface due to the roll, etc., as the processes such as the printing process for packaging, the magnetic material application process for the magnetic recording medium, the calendering process, and the slitting process are accelerated. Occurs. In particular, in the case of the magnetic recording medium, in order to improve the runability and processability, inorganic particles such as calcium carbonate, silica, kaolin, and alumina are added to roughen the polyester surface, but the runability is not sufficiently improved.

In addition, as the production speed of the film is increased, there is a demand for a polyester film having excellent winding properties and wear resistance as well as running performance.

Accordingly, the technical problem to be achieved by the present invention is to provide a biaxially oriented polyester film for a magnetic recording medium having excellent runability as well as winding and abrasion resistance.

In order to achieve the above technical problem, the present invention is a polyester resin; And 0.1 to 2.0% by weight of cubic magnesium oxide, with respect to the polyester resin, having an average particle diameter of 0.1 to 3.0 µm, and providing projections on the surface thereof.

In this invention, it is preferable that the average surface roughness of the said biaxially-oriented polyester film is 0.005-0.050 micrometer.

In the present invention, the projection angle of the projection formed on the biaxially oriented polyester film is preferably 50 to 70 degrees.

Since the polyester film according to the present invention has sharp projections formed on the surface of the film, the contact area of the surface is reduced when traveling on a roll, etc., so that the polyester film is not only excellent in running and abrasion resistance but also in winding property.

Hereinafter, the biaxially oriented polyester film for magnetic recording medium according to the present invention will be described in more detail.

Polymeric raw materials used in the preparation of the polyesters according to the present invention are terephthalic acid (or dimethyl terephthalate), isophthalic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-dicarboxyl diphenyl as dicarboxylic acid components. , 4,4'-dicarboxylbenzophenone, bis (4-carboxydiphenyl) ethane, adipic acid, sebacic acid and 5-sodium sulfoisophthalic acid and ethylene glycol, propylene glycol, butanediol, neo as diol components Pentyl glycol, diethyl glycol, cyclohexanedimethanol and the like. In addition, hydroxycarboxylic acids such as parahydroxybenzoic acid, para-methahydroxyethoxybenzoic acid and the like can also be used.

The polyester according to the present invention uses terephthalic acid and ethylene glycol as the main raw materials and uses them by 80 mol% or more on the basis of polyester, respectively. And as other copolymerization components, it can be used arbitrarily selected from the said dicarboxylic acid component, a diol component, and hydroxycarboxylic acid individually or in combination of 2 or more.

The polyester according to the present invention can be produced by any of the transesterification method and the direct polymerization method, and any of batch and continuous processes can be employed in the process configuration.

In the case of using the transesterification method, there is no particular limitation on the transesterification catalyst, and any conventionally known one can be used. For example, alkali earth metal compounds such as magnesium compounds, zirconium compounds, sodium compounds, potassium compounds, calcium compounds and barium compounds, and cobalt compounds, zinc compounds, and manganese compounds may be used that are soluble in the reaction system.

The polymerization catalyst is also not limited, but it is preferable to use an appropriately selected from antimony compounds, germanium compounds, and titanium compounds.

The polyester film according to the present invention contains magnesium oxide particles that are inert to the polyester film in order to form sharp protrusions on the surface of the film to improve running and wear resistance as well as winding properties. The average particle diameter of the magnesium oxide is in the range of 0.1 to 3.0 mu m, preferably 0.3 to 2.0 mu m, the shape is cubic, and the content is in the range of 0.1 to 2.0 wt%, preferably 0.01 to 1.0 wt%. . The average surface roughness produced by magnesium oxide having the above conditions is in the range of 0.005 to 0.050 mu m, and the projection angle is 50 to 70 degrees.

On the other hand, if the shape of the magnesium oxide particles are not cubic, the projection angle of the surface is smooth and the contact area with the roll is increased, so that the running and abrasion resistance are not remarkable. At this time, when the projection angle is less than 50 degrees, the improvement effect of running and abrasion resistance is insufficient, and when the projection angle exceeds 70 degrees, the projections are easily dropped and become a factor that lowers the wear resistance. That is, only when the projection angle is 50 to 70 degrees, the effect of improving runability and wear resistance was noticeable.

In addition, when the average particle diameter of magnesium oxide is 0.1 µm or less, the surface roughness of the film decreases and the friction coefficient becomes large, and thus the running performance deteriorates. When the average particle diameter is 3.0 µm or more, the running and wear resistance is good, but the electronic characteristics deteriorate, which is not preferable. When the magnesium oxide content is 0.1% by weight or less, roughening of the film is insignificant, and the running and abrasion resistance is not improved. When the content is 2% by weight or more, coarse particles are produced due to the aggregation of magnesium oxide particles, and thus the magnetic tape manufactured using the same The so-called drop-out phenomenon of data loss is undesirable.

The production method of the polyester film in the present invention is not particularly limited, but a polyester having a molecular weight of about 20,000, including the above additives, is prepared from a melt-extruded sheet that has been melt-extruded by a tee-die method or the like, and then It is preferable to biaxially stretch.

The extending | stretching method is the same as the case of the manufacturing method of a normal polyester film, and a process change is not specifically requested | required by said additive. The stretching temperature is preferably in the range of glass transition temperature to cold crystallization temperature, and the stretching ratio is preferably 2.5 to 5.0 times in the longitudinal direction and 3.0 to 5.0 times in the transverse direction. The heat treatment temperature is 180 to 230 캜, preferably 190 to 220 캜.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

In Examples and Comparative Examples of the present invention, various performance evaluation of the produced polyester film was performed by the following method.

(1) Average particle size of particles

After the particles were dispersed in an ethylene glycol solvent using a centrifugal sedimentation particle size analyzer (SACP-II) manufactured by Shimadzu Corporation (Japan), the volume average particle diameter was measured.

(2) Average surface roughness

Surface roughness was measured using a contact surface roughness meter (SURFCORDER SE-30D) of Kosaka Research Institute (Japan). The measurement conditions were the needle diameter of 2㎛, cutoff 0.08mm, and the measuring length of 5mm. After measuring at 7 points, the values at 5 points were averaged except for the maximum and minimum values.

(3) Winding property

After the film was slitted to a width of 1/2 inch and a length of 2000 m to make a film reel, the cross section of the film reel was visually or photographed to evaluate the winding property.

Class A: When there is no delamination at all

Class B: When a layer of less than 0.1 mm is observed throughout the cross section

Class C: When a small number of layers of 0.3 mm or more are observed throughout the cross section

Class D: When multiple layers of more than 0.5mm are observed throughout the cross section

(4) wear resistance

After slitting the film to 1/2 inch width, using a tape running tester (TBT 300D) of Yokohama Systems Research Institute (Japan), friction running on the tape guide pin at a running speed of 3.3 cm / sec, Abrasion resistance was evaluated by visual observation or photographic observation of the occurrence of white powder.

A grade: when no minute powder occurs on the guide pin

Class B: 100% of the guide pin has 1/5 of the guide pin area.

C class: If the guide pin has half of the guide pin area

Class D: When a minute occurs in the whole guide pin

(5) runability

Using the tape running tester (TBT-300D) of the Yokohama System Research Institute (Japan), the running friction coefficient k is driven by running a film slitting 1/2 inch wide at 20 ° C and 60 RH% atmosphere. Obtained.

k = ln (T _out / T _in )

Where T _in is the inlet tension and T _out is the outlet tension.

A) slow speed

After fixing the guide pin, the film was tested under the condition that the contact angle of the film was 180 degrees, the running speed was 3.3 cm / sec, and the inlet tension was 30 g. Then, the exit tension was determined. It was. The k value thus obtained was good if it was 0.35 or less, and bad if it was 0.35 or more.

B) High speed driving

After fixing the guide pin, the film was tested under the condition that the contact angle of the film was 180 degrees, the running speed was 50 cm / sec, and the inlet tension was 300 g. Then, the exit tension was determined. . The k value thus obtained was good if it was 0.10 or less, and bad if it was 0.10 or more.

(6) Average projection angle

The projection angle was determined by measuring the surface profile using a contact surface roughness meter (SURFCORDER SE-30D) of Kosaka Research Institute (Japan). Here, the projection angle is defined as the angle between the tangent drawn on the projection and the interface between the film and the projection at the contact point of the film with the projection. The measuring conditions were stylus diameter 2㎛, measuring length 1mm, vertical magnification 100,000 times, horizontal magnification 1,000 times, and averaged after measuring the projection angle at 10 points.

Example 1

In the presence of 0.2% by weight of cubic magnesium oxide particles having an average particle diameter of 0.9 µm, 0.0224% by weight of zinc acetate as a transesterification catalyst, and 0.0404% by weight of calcium acetate, 7500 g of dimethyl terephthalate and 4780 g of ethylene glycol were transesterified in a batch reactor. Reacted.

The product of the transesterification reaction was polycondensed in the presence of 0.0444% by weight of antimony trioxide as a polycondensation catalyst to prepare a polyester polymer having a molecular weight of about 20,000. Subsequently, it was dried at 180 ° C. for 8 hours, and then melt-extruded by a T-die method to prepare an unstretched sheet in a conventional manner. Subsequently, the unoriented sheet was stretched 3.1 times in the longitudinal direction and 3.7 times in the transverse direction at 90 ° C., and then heat-treated at 210 ° C. to prepare a biaxially oriented polyester film having a thickness of 14 μm. The projection angle of the thus produced film was 62 degrees as shown in Table 1. As such, the large projection angle has become a driving force for excellent winding, wear resistance, and running performance.

Examples 2 to 3

The physical properties of the polyester film prepared in the same manner as in Example 1, except that the type and crystal form, the average particle diameter, and the input amount of the additive was changed as shown in Table 1, it is shown in Table 1 . The projection angles of the films thus produced were all in the range of 50 to 70 degrees, as shown in Table 1. Therefore, both the winding property, the wear resistance, and the running property were excellent (Table 1).

Comparative Examples 1 to 3

The physical properties of the films prepared in the same manner as in Example 1 were measured and shown in Table 1, except that the type and crystal form, the average particle diameter, and the amount of the additives were as shown in Table 1. The projection angles of the films thus produced were all less than 50 degrees as shown in Table 1. Therefore, winding property, abrasion resistance, and running property were bad (Table 1).

division Inclusion Properties Kinds Particle diameter (㎛) Input amount (% by weight) Crystalline form Average surface roughness Turning angle Winding Wear resistance Run Example 1 Magnesium oxide 0.9 0.2 Cubic 0.019 62 A A Good Example 2 Magnesium oxide 0.3 0.3 Cubic 0.013 51 B B Good Example 3 Magnesium oxide 0.5 0.3 Cubic 0.018 57 B A Good Comparative Example 1 Magnesium oxide 0.5 0.3 Block 0.017 43 C B Bad Comparative Example 2 Silica 0.5 0.3 rectangle 0.018 48 C D Good Comparative Example 3 Calcium carbonate 0.5 0.3 Block 0.017 40 C D Bad

As described above, the biaxially oriented polyester film according to the present invention is excellent in winding properties and wear resistance as well as in electronic properties and running properties, and is suitable as a film for magnetic recording media.

Claims (3)

Polyester resins; And A biaxially oriented polyester film having an average particle diameter of 0.1 to 3.0 µm and containing 0.1 to 2.0% by weight of cubic magnesium oxide with respect to the polyester resin, wherein protrusions are formed on a surface thereof. The biaxially oriented polyester film according to claim 1, wherein the average surface roughness of the biaxially oriented polyester film is 0.005 to 0.050 mu m. The biaxially oriented polyester film according to claim 1, wherein the average projection angle of the projections formed on the biaxially oriented polyester film is 50 degrees to 70 degrees.