KR0181382B1 - Biaxial orientational polyester film for highly intensive magnetic writing material - Google Patents

Abstract

The present invention uses a small amount of germanium dioxide or antimony trioxide as a polycondensation catalyst, and contains 0.01-1.0 wt% of inert particle concave silica having an average particle size of 0.01-2.0 μm, and an average particle size of 0.1-3.0 μm particles. An unstretched film is made of polyethylene terephthalate resin having a refractive index of 1.5 and 0.01 to 1.0% by weight of inert particle calcium phosphate having fine unevenness on the surface having a density of 2.6 and an intrinsic viscosity of 0.45 or more and 0.70 or less. Biaxial orientation for high density magnetic recording media, which is performed in the longitudinal direction at 2.0 to 5.0 times, followed by stretching at 2.0 to 5.0 times at 90-140 ° C. and thermal curing at 180-230 ° C. for 1 second to 10 minutes. a polyester film, the tensile stress (hereinafter referred to as F-5 value quot;) the longitudinal and lateral directions all 10kg / mm ³ or higher Young's modulus in the longitudinal and lateral directions all 400kg / mm ³ or more, the heat shrinkage at 5% elongation Less than 2% in both longitudinal and transverse directions, centerline average roughness SRa is between 0.05μm and 0.012μm, 10-point average roughness SRz meets 0.010μm to 0.250μm, centerline maximum roughness SRmax is 0.05μm to 0.40μm A biaxially oriented polyester film for a magnetic recording medium.

Description

Biaxially Oriented Polyester Film for High Density Magnetic Recording Media

The present invention has high mechanical strength and good dimensional stability, and exhibits excellent electron conversion properties when made of magnetic tape due to the extremely smooth film surface with almost no dropout. The present invention relates to a polyester film having excellent runability. More specifically, the present invention relates to a biaxially oriented polyester film for a high density magnetic recording medium composed of polyethylene terephthalate having good smoothness and smoothness, thin thickness, and excellent mechanical strength.

Currently, polyester film is widely used as a basic material in the industrial field due to its excellent physical and chemical properties. Among these, biaxially stretched polyethylene terephthalate film has excellent dimensional stability and mechanical strength compared to other films, so It is widely used as an industrial film for base films for magnetic recording media, capacitors and films for electrical insulation, packaging and graphics.

A dual magnetic recording medium is obtained by forming a magnetic layer on the surface layer of the base film using magnetic particles together with a binder, or by coating the surface of the base film with a magnetic metal by vacuum deposition, sputtering or plating.

Recently, the demand for high density recording is increasing in magnetic recording media. As the demand for high density recording increases, the importance of increasing heat resistance, physical properties, and smoothing of the film surface has been important. Polyethylene terephthalate films have long been used as magnetic recording films, and much effort has been made to improve the properties of these films in order to meet the demands of high density magnetic recording media.

High smoothness of the support is required in order to improve the electron conversion properties during the production of the polyester base film, and easy activity is required to improve the processability of the film. Therefore, efforts have been made to satisfy these conflicting requirements simultaneously. However, it is difficult to control the coarse protrusion protruding from the surface of the film by adding various inorganic particles and additives in the polyester film, so solving this problem is the most important technology in the base film for high density magnetic recording media. .

The method of satisfying the high smoothness and the diactivity of the base film described above (Japanese Patent Application Laid-Open No. 3-80410, Japanese Patent Application Laid-Open No. 56-16937, Small 58-68223, Small 60-180838, Small 60-180839) and two or more polymers Method of manufacturing a double roughness film by laminating the surface (Japanese Patent Application Laid-Open No. 57-36341, Small 57-38762, Small 573863, Japanese Laid-Open Patent Publication 1-26337, Flat 1-26338) and internal precipitation generated inside the polyester. Control methods for particles (Japanese Patent Publication No. 62-106305) and the like are known.

Polyethylene terephthalate obtained by such a conventional technology has excellent heat resistance, dimensional stability, mechanical strength and chemical properties, but it is difficult to produce the internal precipitated particles by the additives added during the condensation reaction in an extremely small state.

Accordingly, an object of the present invention is to provide a biaxially oriented polyethylene terephthalate film for a high density magnetic recording medium which satisfies both workability and runability as well as excellent surface smoothness in manufacturing a polyethylene terephthalate film.

In the present invention, as a result of the study to solve this problem, as the polycondensation catalyst of polyethylene terephthalate resin having an extreme viscosity of 0.45 or more and 0.70 or less, germanium dioxide is used alone or mixed with germanium dioxide and antimony trioxide, but the amount of antimony trioxide is minimized. By minimizing the amount of internally precipitated particles due to the residue of the catalyst, and using a specific amount of particles having a specific particle diameter in the polyester resin, the centerline average roughness, the ten-point average roughness, and the maximum maximum centerline roughness of the film are satisfied. By adjusting, the polyester film is excellent in both smoothness and deactivation at the same time, and stretched under specific film forming conditions, thereby obtaining a polyester film having high mechanical strength and good dimensional stability and excellent physical properties with little dropout, but with improved productivity.have.

Thus, since the film is manufactured under the specific manufacturing conditions described above, it is possible to produce a film that can improve productivity by improving film production yield while maintaining properties such as high mechanical strength and dimensional stability of polyethylene terephthalate.

The present invention uses a small amount of germanium dioxide or antimony trioxide as a polycondensation catalyst, and contains 0.01-1.0 wt% of inert particle concave silica having an average particle size of 0.01-2.0 μm, and an average particle size of 0.1-3.0 μm particles. A non-stretched film is made of polyethylene terephthalate resin having a refractive index of 1.5 and 0.01 to 1.0% by weight of inert particle calcium phosphate having fine irregularities on the surface having a density of 2.6 and an intrinsic viscosity of 0.45 or more and 0.70 or less. Biaxial orientation for high-density magnetic recording media made by calculating 2.0 to 5.0 times in the longitudinal direction at 0 ° C., followed by stretching 2.0 to 5.0 times in the transverse direction at 90 to 140 ° C., and heat curing at 180 to 230 ° C. for 1 second to 10 minutes. Polyester film, tensile stress (hereinafter referred to as F-5 value) at 5% elongation, 10kg / mm ³ or more in both the longitudinal and transverse directions Young's modulus is 400kg / mm ^{3 and} more in the longitudinal and transverse directions, thermal shrinkage 2% or less in both longitudinal and transverse directions, centerline average roughness SRa is between 0.05μm and 0.012μm, 10-point average roughness SRz satisfies 0.010μm to 0.250μm, and centerline maximum roughness SRmax is between 0.05μm and 0.40μm A biaxially oriented polyester film for a high density magnetic recording medium, characterized by the above-mentioned.

Hereinafter, the present invention will be described in more detail.

The polyethylene terephthalate produced in the present invention is prepared using dicarboxylic acid and glycol as the main starting materials, but may also include another third component. At this time, as dicarboxylic acid component, 1 type, or 2 or more types can be mixed and used out of isophthalic acid, terephthalic acid, 2, 6- naphthalenedicarboxylic acid, phthalic acid, adipic acid, and sebacic acid. As a glycol component, 1 type, or 2 or more types can be mixed and used out of ethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, and neopentyl glycol.

As a method for minimizing the presence of catalyst residue in polyester as a polycondensation catalyst, the present invention minimizes the amount of antimony trioxide and uses a germanium compound as a substitute, thereby causing a catalyst residue that causes high smoothness of the polyester base film. By minimizing the effects of, the dropout, which is an important property of the magnetic tape, was minimized after the formation of the ferromagnetic thin film.

In the present invention, the polyester may also include additives of colorants, flame retardants, stabilizers, antiblocking agents, antioxidants, antistatic agents, ultraviolet absorbers and other materials to improve the pinning properties of the sheet. As the germanium-based compound, oxides of germanium, organic acid salts, alkyl and aryl compounds, etc. may be used. Specific examples thereof may include germanium oxide, germanium tetraacetate, germanium hydroxide, germanium stannate, and the like. The addition amount of germanium dioxide (a) is 10-50 ppm with respect to polyester, More preferably, 25-50 ppm is good, The addition amount of antimony trioxide (b) is 50 ppm or less, and it adds in the range which satisfy | fills the following formula. good.

When the total amount of the germanium compound and the antimony trioxide is less than 35 ppm, the progress of the condensation reaction may be difficult, and when the addition amount of the antimony trioxide is 50 ppm or more, the film is prepared by the internal precipitate remaining in the polyester after the condensation reaction. It may be present as a defect on the surface of the seam base film may cause dropout when manufacturing magnetic tape. As the input form of the condensation catalyst, a form dispersed in water, a form dispersed in ethylene glycol, or a form dispersed in a mixture of water and ethylene glycol can be used.

In the preparation of the polyester using the above method, inert inorganic fine particles are added to improve the running property of the biaxially oriented film, and as the fine particles, the inorganic fine particles are calcium phosphate, MgO, ZnO, MgO ₃ , SiO ₂ , CaSO ₄ , CaCO It is possible to improve the running property of the base film by using at least one of ₃ , BaSO ₄ , Al ₂ O ₃ , and the like.

The average particle diameter of the inert particle concave silica used in the present invention is 0.01-2.0 μm, more preferably 0.10-10 μm, and the average particle diameter of the inert particle calcium phosphate is 0.1-3.0 μm, more preferably 0.4 -1.0 μm is suitable. If two or more kinds of inert particles are not used, it is difficult to satisfy high smoothness and runability at the same time. Therefore, the selection of optimal inert particles is one of the important technical elements.

The average particle diameter of the inorganic fine particles can be easily observed from the scanning electron microscope limbs of the particles or the transmission electron micrographs of the particles in the film. If the size of inorganic fine particles exceeds 2.0μm, the surface roughness is increased and coarse particles are generated, and many defects such as dropouts occur when using magnetic tape, and if the particle size is smaller than 0.01μm, it is difficult to give surface projections to the film. The poor activity and runability cause problems in the production of the film.

Here, the inert particle calcium phosphate for improving runability has an infinite number of pores on the surface of the particles, so it is most suitable as a runability improver that can suppress the occurrence of falling particles and improve runability. The total amount of particles added is 0.01-1.0% by weight relative to the resulting polymer, preferably 0.05-0.8% by weight. If it is less than 0.01% by weight, the activity and runability are poor, and if it exceeds 1.0% by weight, the centerline average roughness is increased, and coarse particles are generated by particle aggregation, which causes the dropout. The input form of the particles may be a form dispersed in water, a form dispersed in ethylene glycol, or a form dispersed in a mixture of water and ethylene glycol.

The biaxially-oriented polyester film which consists of polyethylene terephthalate using the polyester manufactured by the above method can be obtained by the following method.

Polyethylene terephthalate polymer containing particles was prepared by the above method, made into chips and dried in the usual manner, and then the polymer was extruded at 280-300 ° C. through an extruder and cooled to 20-50 ° C. on a cooling drum. After that, an amorphous unstretched sheet was obtained. This unstretched sheet was stretched 2.0 to 5.0 times in the longitudinal direction at 90-130 ° C., and then stretched 2.0 to 5.0 times in the transverse direction at 90-140 ° C., preferably relaxing to 1% to 30% in the transverse direction. A biaxially oriented polyester film for high density magnetic recording medium was prepared by thermal curing at 180-230 ° C. for 1 second to 10 minutes.

The biaxially stretched polyester film according to the present invention obtained by the above-described method has a F-5 value of 10 kg / mm ³ or more in the longitudinal direction and the transverse direction, and a Young's modulus of 400 kg / mm ³ or more in the longitudinal direction and the transverse direction, 2% or less in both directions and transverse directions, centerline average roughness SRa is between 0.05μm and 0.012μm, 10-point average roughness SRz drops out while satisfying 0.010μm to 0.250μm and centerline maximum roughness SRmax is 0.05μm to 0.40μm It is suitable as a biaxially oriented polyester film for high-density magnetic recording media without surface defects of the base film which may cause the

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Measurement of various physical properties of the obtained polyester film was performed by the following method.

(1) F-5 value

This value represents the tensile stress measured when a 10 mm wide film sample was stretched 5% with a tensile tester at a temperature of 25 ° C., a distance of 100 mm between chucks, and a tensile speed of 20 mm / min.

(2) Young's modulus

Young's modulus is represented by the initial Young's modulus at the time of tension when the film sample of 10 mm width is extended | stretched at the temperature of 25 degreeC, the distance between chucks, 100 mm, and 20 mm / min.

(3) heat shrinkage

Heat shrinkage was measured after leaving the film specimen in the oven for 30 minutes in 105 ℃. Thermal shrinkage is calculated as [(I ₀ / I) / I ₀ ] × 100 (%), where I ₀ is the original length and I is the length measured after heat treatment.

(4) Film centerline roughness (SRa), 10-point average roughness (SRz) and centerline maximum roughness (SRmax)

SRa, SRz, and SRmax were measured using a three-dimensional surface roughness meter manufactured by Kosaka, Japan.

(5) bifunctional

The polyester film was made of a roll tape of a predetermined width, and then fixed to a metal guide roll and run while contacting for a long time. The degree of scratching on the surface of the film was observed under a microscope, and the amount of white matter generated on the guide roll was visually observed. .

Level 1: Almost no scratch on film surface after friction with guide roll.

Level 2: Small scratches on the film surface after friction with the guide roll.

Level 3: Scratches on the film surface after friction with the guide roll.

(6) dropout

The surface of the biaxially oriented polyester film was coated with a magnetic layer with a thickness of 4 μm using a conventional method to prepare a video tape, and then the optimum current was recorded on the video tape with a five-step disparity signal, and the attenuation of the video head output was 20 dB. A dropout of 15 μsec or more was considered as a dropout, measured continuously for 30 minutes, and averaged per minute to be divided by AD grade.

A: 10 less than / min

B: 10 or more / minute-less than 30 / minute

C: More than 30 / minutes-less than -50 / minute

D: more than 50 / min

Example 1

A mixture of 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, 0.09 parts of manganese acetate tetrahydrate, 0.004 parts of germanium dioxide, and 0.002 parts of antimony trioxide was heated in a reactor, and methanol was discharged to carry out transesterification. The reaction mixture was completed transesterification over 4 hours. 0.03 parts of trimethyl phosphate and two kinds of inorganic fine particles (calcium phosphate, concave silica) were added to the reaction mixture, followed by a condensation reaction for 4 hours to obtain a polyester chip. It is dried and then extruded through an extruder to obtain an unstretched film, the unstretched sheet is stretched 4.7 times longitudinally at 120 ° C., then stretched 4.7 times at 110-130 ° C. in the transverse direction, and from 1% to transverse direction. The film was thermosetted at 210 ° C. for 30 seconds while relaxing to 30%, yielding a film having a thickness of 14.2 μm. As a result of evaluating the physical properties of the oriented film, as shown in the following table, it was possible to obtain a high smooth base film having excellent reactivity and high smoothness, which hardly caused dropout when manufactured with magnetic tape. Physical properties are shown in the following table.

Example 2

Except for the addition of 0.010 parts of the amount of antimony trioxide was carried out in the same manner as in Example 1 to obtain a film, the physical properties of the film are shown in the following table.

Comparative Example 1

A film was obtained by the same method as in Example 1 except that antimony trioxide was used alone as a condensation catalyst, and the film properties thereof are shown in the following table.

Comparative Example 2

A film was obtained by the same method as in Example 1 except that the added inorganic fine particles were used alone in spherical silica, and the film properties thereof are shown in the following table.

Comparative Example 3

A film was obtained by the same method as described in Example 1 except that the amount of antimony trioxide added was 100 ppm, and the film properties thereof are shown in the following table.

Claims (11)

In a polyester resin containing 90 mol% or more of dimethyl terephthalate units and an intrinsic viscosity of 0.45 or more and 0.70 or less, germanium dioxide is used as a condensation catalyst at 10-50 ppm or less with respect to polyester to carry out a condensation reaction. Inert particles containing 0.01-1.0 wt% of concave silica with an average particle diameter of 0.01-2.0 μm, an inert particle calcium phosphate having fine irregularities on the surface having a refractive index of 1.5 and a density of 2.6 with an average particle diameter of 0.01-3.0 μm A biaxially oriented polyester film for a high density magnetic recording medium, characterized by continuously biaxially stretching an unoriented film containing 0.01-1.0% by weight and heat setting at 180-230 ° C. for 1 second to 10 minutes. 2. The biaxially oriented polyester film for magnetic recording media according to claim 1, wherein germanium dioxide and antimony trioxide are mixed and used as a catalyst for condensation of the polyester resin. The method of claim 1, wherein manganese acetate or magnesium acetate is used as a catalyst for transesterification drops. 2. A biaxially oriented polyester film for magnetic recording media according to claim 1, wherein spherical silica or concave silica is added as particles (A) to be used, and calcium carbonate or calcium phosphate particles are used as particles (B). . The biaxially oriented polyester film for a high density magnetic recording medium according to any one of claims 1 to 4, wherein the physical properties of the film satisfy the following conditions. [F-5 value is tensile stress at 5% elongation, SRa is center line average roughness (μm), SRz is 10 point average roughness (μm), SRmax is center line maximum roughness (μm)] A biaxially oriented polyester film for a high density magnetic recording medium according to claim 1, wherein a thickness of the film is 10-15 µm or less. The biaxially oriented polyester film for a high density magnetic recording medium according to claim 1, which comprises at least one colorant, flame retardant, stabilizer, antiblocking agent, antioxidant, antistatic agent or ultraviolet absorber. A biaxially oriented polyester film for a high density magnetic recording medium according to claim 1, wherein the amount of germanium dioxide (a) and the amount of antimony trioxide (b) are satisfied. The biaxial high density magnetic recording medium according to claim 1 or 2, wherein the expansion / condensation catalyst is used in the form of dispersed in water, dispersed in ethylene glycol, or dispersed in a mixture of water and ethylene glycol. Oriented polyester film. 2. The biaxially oriented polyester for high density magnetic recording medium according to claim 1, wherein the irrational particle calcium phosphate is used in the form of dispersed in water, dispersed in ethylene glycol, or dispersed in a mixture of water and ethylene glycol. film. The biaxially oriented polyester film for a high density magnetic recording medium according to claim 1, wherein the Young's modulus of the film is 40 kg / mm ³ or more in the longitudinal direction and the transverse direction, and the heat shrinkage is 2% or less in both the longitudinal direction and the transverse direction.