KR0167131B1 - Biaxial orientation polyester film for magnetic recording medium - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester base film for magnetic recording media, wherein aluminum melt particles having an appropriate hardness and low melt specific resistance are used to improve the adhesion of the melt to the casting drum during extrusion, and have excellent running and abrasion resistance. It is to provide a biaxially oriented polyester film for the recording medium, its technical configuration contains 0.03 to 1.0% by weight of aluminum silicate (SiO ₂ -Al ₂ O ₃ -Na ₂ O) particles having an average particle diameter of 0.005 to 1㎛, A biaxially oriented polyester film for magnetic recording media, characterized by containing 0.15 to 0.8% by weight of inorganic particles having an average particle diameter of 0.3 to 1.2 mu m.

Description

Biaxially Oriented Polyester Film for Magnetic Recording Media

1 is a schematic diagram of a traveling system that is a device for evaluating running, abrasion and scratch resistance of a film.

* Explanation of symbols for main parts of the drawings

1: fixed pin (diameter 6mm) 2: tension meter

3: Tension measuring device (theta): It is 180 degree as a winding angle.

The present invention relates to a biaxially oriented polyester film for a magnetic recording medium, and more particularly, has excellent wear resistance and runability, excellent electronic conversion characteristics when made of magnetic tape, and wear and tear by friction. The present invention relates to a biaxially oriented polyester film for high-density magnetic recording media with less scratches.

Conventionally, the polyester film is very excellent compared to other substrates in terms of mechanical properties, chemical resistance, heat resistance, and weather resistance, and thus has been widely used as a base material in various industrial fields.

In particular, polyethylene terephthalate films are indispensably used as base films for magnetic recording media, and in addition, they are used in various industrial films such as capacitor films, electrical insulation films, and graphics.

On the other hand, in recent years, the improvement of the magnetic recording medium has been made rapidly. For example, the magnetic recording tape has been rapidly progressed in high performance for high density recording and miniaturization of media. Therefore, the surface of the base film should be more smooth.

In general, in order to improve the diactivation, running and wear resistance of the film surface, methods of adding external particles such as calcium carbonate, silica, alumina, zirconia, titanium dioxide, and inert polymer particles are well known. The surface roughness of the film due to the particles should be maintained at an appropriate level. When the surface roughness of the film is lowered to an appropriate level by using particles of too small particle size, the electron conversion property of the tape is improved when used as a magnetic tape, but the running performance in the film manufacturing process is poor and frictional wear between the film and the film This results in a large amount of white powder and scratches. And when using too large particles, the running performance of the film is improved, but the large projection generated by the large particles in the film increases the surface roughness of the film, worsening the electron conversion characteristics such as drop out of the magnetic tape. . Therefore, Japanese Patent Application Laid-Open No. 2-120329, Hei 3-172319, Hei 4-216031 and the like improve the running and wear resistance of a film by mixing a fine particle with a larger particle size and a particle having a larger particle size. Polyester base films have been used. However, alumina, which is an external particle used in such a film, has a problem of causing great damage to hardware because of its high hardness.

It is an object of the present invention to improve adhesion to casting drums during film formation by using particles having an appropriate hardness and low melt resistivity, and to have excellent running performance, abrasion resistance, scratch resistance, and magnetic recording without damaging hardware when formed with magnetic tape. It is to provide a biaxially oriented polyester film for the medium.

In order to achieve this object, the present inventors use an aluminum silicate (SiO ₂ -Al ₂ O ₃ -Na ₂ O) having an average particle diameter of 0.005 to 1 μm, and having at least 25 to 70 wt% of aluminum and at least 10 wt% of sodium as a component. Provided is a biaxially oriented polyester film for a magnetic recording medium characterized by containing 0.03 to 1.0% by weight of polyester and 0.15 to 0.8% by weight of inorganic particles having a particle size of 0.3 to 1.2 μm. The use of aluminum silicate particles with less than 25% by weight of aluminum and less than 10% by weight of sodium does not result in adequate hardness and low melt-resistance values.In the case of more than 70% by weight of aluminum, high hardness will damage the hardware. Is given.

Hereinafter, the present invention will be described in detail.

In the present invention, the polyester may contain an aromatic dicarboxylic acid such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, or a polyester obtained by using the ester and ethylene glycol as a main starting material, or another third component. have. In this case, the dicarboxylic acid component is, for example, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, phthalic acid, adipic acid, sebacic acid, and oxycarboxylic acid component such as P-oxyethoxybenzoic acid. Species or two or more kinds may be used. Moreover, 1 type, or 2 or more types, such as ethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, can be used as a glycol component.

It is preferable that 80 mol% or more of the repeating structural unit of the polyester of this invention is polyester which has an ethylene terephthalate or an ethylene 2,6-naphthalene structure.

Moreover, the polyester of this invention may contain arbitrary additives, for example, a heat stabilizer, anti-broking agent, antioxidant, a coloring agent, antistatic agent, an ultraviolet absorber, etc.

The main feature of the present invention is to provide a biaxially oriented polyester film which improves the adhesiveness of the melt during extrusion and improves the wear resistance, scratch resistance and runability of the film by using aluminum silicate particles having appropriate hardness and low melt specific resistance as fine particles. Is in. In addition, the polyester film of the present invention includes the aluminum silicate microparticles and inorganic particles of calcium carbonate.

In the present invention, aluminum silicate (SiO ₂ -Al ₂ O ₃ -Na ₂ O) particles containing an appropriate amount of sodium and aluminum are used in order to improve the adhesion to the casting drum, running and electron conversion characteristics, the average particle diameter of 0.005 To 1 μm, the content of which should be in the range of 0.03 to 1.0 wt% based on the polyester.

If the average particle size is less than 0.005㎛ or the content is less than 0.03% by weight, the scratch resistance is inferior. On the other hand, if the average particle size is more than 1㎛ or the content is more than 1.0% by weight, the surface smoothness of the polyester is significantly decreased. The signal recording characteristic of the magnetic recording medium due to the transfer or the like becomes poor.

In particular, the average particle diameter of the aluminum silicate is preferably 0.01 to 0.1 µm, and its content is preferably 0.08 to 0.5% by weight, more preferably in the range of 0.1 to 0.4% by weight.

Inorganic particles used with the aluminum silicate in the polyester film of the present invention is an average particle diameter of 0.3 to 1.2㎛, such as calcium carbonate or silica, the content should be in the range of 0.15 to 0.8% by weight. If the average particle diameter of the added inorganic particles is less than 0.3 mu m, the running and abrasion resistance is hardly improved. If the average particle diameter is larger than 1.2 mu m, the surface roughness of the polyester film is too large, and the magnetic recording characteristics are degraded by transfer or the like. Moreover, preferably the average particle diameter of an inorganic particle is 0.4-1.0 micrometer, Especially preferably, the range of 0.5-0.8 micrometer is suitable.

When the content of the inorganic particles is less than 0.15% by weight, the surface uniformity, running and abrasion resistance are not improved. When the content of the inorganic particles is more than 0.8% by weight, the surface roughness is increased, resulting in poor signal recording characteristics. The content of the inorganic particles is particularly preferably in the range of 0.2 to 0.6% by weight.

The particle | grains used for this invention are mix | blended with polyester by operation, such as crushing and filtration as needed. For example, a grinding mill, a ball mill, a vibrating rod mill, a vibrating ball mill, a roller mill, an impact mill, a stirring mill, a liquid energy mill and the like can be used. As a method for incorporating the particles into the polyester, a method of adding the particles to the reaction system in the initial stage of polyester production using the particles as an ethylene glycol slurry is generally preferred in view of dispersibility. In this case, the method of directly blending into polyester before film forming is generally used.

In the present invention, in order to produce a polyester film, a polyester polymer containing each particle is synthesized and mixed at a predetermined ratio, and then melt-extruded to 270 to 300 ° C., cooled to 40 to 70 ° C., and solidified to produce amorphous film. A new film is obtained, which is 3.0 to 4.9 times longitudinally stretched at 90 to 140 ° C., followed by 4.0 to 5.2 times transverse stretching at 110 to 170 ° C. and heat treatment at 160 to 240 ° C. to obtain a polyester film. In addition, in the present invention, the transverse draw ratio is increased than the conventional draw ratio to lower the transverse refractive index, thereby making it possible to prevent scratches and cuts of the film.

As described above, the present invention is a polyaxially oriented polyester film for a magnetic recording medium, which has been particularly difficult to improve wear resistance and scratch resistance. The problem can be improved by blending the ester, and finally, the base film excellent in the magnetic signal recording property can be obtained by using the polyester film according to the present invention.

EXAMPLE

Hereinafter, the present invention will be described in more detail with reference to Examples.

In the examples and comparative examples, parts represent parts by weight '. In addition, the measurement of various physical properties used in the present invention was carried out according to the following method.

(1) Average particle size of particles

The average particle diameter of the slurry of the particles was measured using a particle size distribution analyzer (Granulometer HR-850), and the particle size on the film was measured by using an electron microscope. In this case, a particle diameter of 50% of the volume fraction of the particles in terms of a sphere was measured. It was set as the average particle diameter.

(2) runability

As shown in the drawing, the angle of the winding portion of the film contacts the metal roll plated with hard chrome (diameter: 6 mm) fixed at 180 °, and a load of 50 g (T ₂ ) is applied at one end and at a speed of 1.1 m / sec. When driving, the resistance (T ₁ ) at the other end was measured, and the friction coefficient (μk) during driving was obtained according to the following equation.

_{μk = 1 / θln (T 1} / T 2) = 0.318ln (T 1/50)

(3) wear resistance

Using the film traveling meter as shown in the drawing, contact the metal fixing pin (diameter: 6mm, surface roughness: 3S) coated with hard chrome at a winding angle of 180 ° and a tension of 50g, and travel 66m at a traveling speed of 1.1m / sec. At that time, the percentage of metal fixation pins was visually determined and classified into the following grades.

Class A: No powder occurs

Class C: Very small amount of powder, no problem in actual use

C grade: Some powder occurs, and there is a problem when using it for a long time

D grade: It generates a lot of powder and is difficult to use.

(4) scratch resistance

The film is cut into a tape of 1/2 inch width, and a tape running tester (TBT-300D / H tester, manufactured by Yokohama Test Laboratory, Inc., Japan) is run at 20 ° C and 60% RH for 50g of tension. An optical microscope is used to determine the amount of scratches generated by driving the tape guide pin of a video cassette (stainless guide pin having surface roughness Ra of 50 nm and Rt of 2500 nm) 50 times at a winding angle of 180 ° at a speed of 1.1 m / sec. .

Class A: No scratch

Class B: Slight scratch

Class C: Many scratches

(5) Surface roughness (Ra)

Using a high precision surface roughness meter (ET-10) manufactured by Kosaka Institute, Japan, the measurement was made 20 times under the following conditions and evaluated as an average value.

-Tip tip radius: 0.5㎛

Probe load: 5 mg

-Touch Length: 1mm

-Cut-up value: 0.08㎛

(6) magnetic disk characteristics

The electromagnetic characteristics of the magnetic tape were measured using the NV-3700 type video deck of Song-Ha Electric.

-VTR head output

Measured at a frequency of 4 MHz with a Syncroscope, it was rated as follows compared to a reference tape (high quality video tape with backside coating). A grade is preferred.

A: much better than standard tape

B: worse than standard tape

C: Remarkably worse than standard tape, not usable

Dropout Count

When the video tape recorded 4.4 MHz was played back, the dropout count was evaluated every 20 minutes by a dropout counter manufactured by Okura Industries, Ltd., made in Japan.

(6) Melt resistivity measurement

The method described in the British Applied Physics Journal (Brit. J. Appl. Phys), Vol. 17, pp. 1149-1154 (1966), except that the temperature is the specific resistance after applying the DC voltage of 1000 V to the molten polymer at 295 ° C. did.

Example 1

100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, 0.09 parts of magnesium acetate tetrahydrate and 0.04 parts of antimony trioxide were heated in a reactor, and methanol was discharged to perform transesterification. After the reaction mixture was transesterified over 4 hours, 0.03% by weight of phosphoric acid was added to prepare a reaction product. The content of aluminum silicate particles in the reaction mixture was silicon, aluminum, sodium content ratio of 59.2: 25.4: 15.4, and the average particle diameter of 0.05 μm aluminum silicate was added to the reaction product in the form of ethylene glycol slurry and polycondensation was carried out for 4 hours. It carried out and obtained polyester (A) of intrinsic viscosity 0.620. The reaction was carried out in the same manner as in the polyester (A), and polycondensation reaction was carried out by adding calcium carbonate particles having an average particle diameter of 0.6 µm in 1.0 part to the reaction mixture instead of aluminum silicate to obtain a polyester (B). Except not adding the inorganic particles, the same transesterification reaction and polycondensation reaction as in the production of the polyester (A) were carried out to obtain a polyester (C) having an intrinsic viscosity of 0.610.

The polyesters (A), (B), and (C) synthesized above were mixed in a weight ratio of 25:30:45, and melt-extruded and cooled to solidity at 290 ° C to form an amorphous unstretched film, which was then heated at 120 ° C. A biaxially stretched polyester film having a thickness of 14.5 μm was prepared by stretching 4 times in the longitudinal direction and 4.5 times in the transverse direction at 130 ° C. and performing heat treatment at 200 ° C. for about 3 seconds.

Thereafter, a magnetic layer was coated on the obtained polyester film to prepare a magnetic tape, and the overall physical properties of the polyester film and the magnetic tape were evaluated.

Example 2

The reaction was carried out in the same manner as the polyester (A), and polycondensation reaction was carried out by adding silica particles having an average particle diameter of 0.6 mu m to 1.0 parts instead of aluminum silicate to prepare a polyester (D) (A), (D) and (C) were mixed in a weight ratio of 25:30:45, and evaluated after film production in the same manner as in Example 1.

Comparative Example 1

In preparing polyester (A), the average particle diameter was 0.05 μm, and high-hardness alumina particles were added to the reaction product to prepare polyester (E), thereby preparing polyester (E), (B), and (C) by weight ratio 25: After mixing to 30:45, it evaluated after film manufacture by the method similar to Example 1.

Comparative Example 2

When preparing polyester (A), aluminum silicate particles having an average particle diameter of 0.05 mu m and containing sodium: aluminum: silica = 1: 49: 51 were added to the reaction product to prepare polyester (F), thereby obtaining polyester (F). (B) and (C) were mixed in a weight ratio of 25:30:45, and evaluated after film production in the same manner as in Example 1.

The film of the present invention has excellent casting adhesion, running property, abrasion resistance and electron conversion characteristics, and can be applied to various applications such as base films for metal deposition or magnetic recording media, and its industrial value is very high.

Claims (3)

0.03 to 1.0 wt% of aluminum silicate (SiO ₂ -Al ₂ O ₃ -Na ₂ O) particles having an average particle diameter of 0.005 to 1 µm, and 0.15 to 0.8 wt% of inorganic particles having an average particle diameter of 0.3 to 1.2 µm. A biaxially oriented polyester film for a magnetic recording medium, characterized in that. 2. The biaxially oriented polyester film for magnetic recording media according to claim 1, wherein the aluminum silicate particles comprise 25 to 70 wt% or more of aluminum and 10 wt% or more of sodium as its constituents. The biaxially oriented polyester film for magnetic recording media according to claim 1, wherein the inorganic particles are composed of one or two of calcium carbonate and silica.