KR19990003749A - Biaxially Oriented Polyester Film for High Density Magnetic Recording Media - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester film for high-density magnetic recording media having excellent running properties and winding properties when the film surface is extremely smooth and made of magnetic tape. The technical composition is 80 mol% or more of the resin. 0.05 to 1.0% by weight of spherical silica particles having an average particle diameter of 0.05 to 0.5 µm were added by adding 0.05 to 10 wt% of cumylphenyl acetate ester as the first component in a polyester having a chemical structural repeating unit of ethylene terephthalate, As a second component, 0.005 to 0.5 wt% of calcitic hexahedral calcium carbonate particles having an average particle diameter of 0.1 to 2.0 µm surface treated with a polymer polycarboxylic acid copolymer composed of polyacrylic acid, polyacrylic acid ammonium salt, and polymethaglylate salt Where the content of the first component is added within the range of 2 to 20 times the content of the second component. FIG biaxially oriented polyester film for magnetic recording medium being.

Description

Biaxially Oriented Polyester Film for High Density Magnetic Recording Media

The present invention relates to a polyester film having excellent runability and winding ability when the film surface is extremely smooth and made of magnetic tape. More specifically, the chemical structural repetition unit of 80 mol% or more of the resin is ethylene tere. In the polyester consisting of phthalates, spherical silica particles are used as the first component, and calcitic hexagonal calcium carbonate particles are used as the second component, and the content of the first component is added in a range of 2 to 20 times the content of the second component. The present invention relates to a biaxially oriented polyester film for a high density magnetic recording medium having low coarseness on the surface and having excellent electron conversion characteristics as a magnetic tape.

Polyester films are excellent in physical and chemical properties, and are currently widely used as industrial base materials. Of these, biaxially oriented polyethylene terephthalate films have superior planarity, dimensional stability, and mechanical strength, compared to other films, such as base films for magnetic recording media of video and audio, films for condensate and electrical insulation, packaging, and graphics. It is mainly used as an industrial film.

On the other hand, in recent years, the improvement of the magnetic recording medium has been made rapidly, which naturally requires the improvement of the foam quality of the base film. For example, in order to be used in magnetic tape such as video tape, a high density recording is required and a base film having a high smooth surface has been required. However, in order to improve the process runability, diactivity and abrasion resistance of the film, external particles such as calcium carbonate, silica, alumina, zirconia, tartan dioxide, and crosslinked polymer particles are added to the film, and the particles can be precipitated by any catalyst deposition in the film. The internal particle method in which is generated is well known. For this reason, the surface roughness of the film due to the particles used must be maintained at an appropriate level. Otherwise, if the surface roughness of the film is lowered to an appropriate level by using particles of too small particle size, the electronic conversion of the tape when used as magnetic tape The characteristics can be improved, but the running property in the film manufacturing process is poor and a large amount of powder and scratches may occur due to frictional wear between the film and the film. And when using too large particles can improve the running properties of the film, but the large projections generated by the large particles in the film may increase the surface roughness of the film may deteriorate the electron conversion characteristics such as dropout of magnetic tape.

In order to improve the electron conversion characteristics, smoothness of the surface of the nonmagnetic support is required, and appropriate roughness is required to improve the handing and running properties. Therefore, for high-density magnetic rock media, a film that can satisfy these two opposite characteristics at the same time is required.

As a method of manufacturing a specific polyester film that can satisfy the above two properties simultaneously, a method of forming a discontinuous coating structure by applying a coating of a characteristic on the film surface (Japanese Patent Laid-Open No. 3-80410, Japanese Patent Laid-Open No. 60) -180837, SO 60-180838, SO 60-180839), and when the polyester film is used as a magnetic tape, when the magnetic tape is made of magnetic tape by changing the surface design of the film surface on which the magnetic material is applied or deposited and the opposite side thereof, A method of forming a laminated polyester film having improved conversion characteristics and runability in a film manufacturing process (Japanese Patent Laid-Open Publication No. 1-26337, Japanese Patent Laid-Open No. 1-26338, Japanese Patent Application Laid-open Publication No. 57-36340, Japanese Patent Laid-Open Publication No. 325674) is known.

However, such a film may cause blocking, abrasion and scratches due to friction with the metal roll in the film manufacturing process due to extremely low surface roughness of the film surface on which the magnetic material is applied or deposited, and such abrasion and scratches Despite the low surface roughness of the film, when made of magnetic tape, it can deteriorate the electron conversion characteristics such as dropout. In order to improve wear resistance of the film, a method of adding high-hardness microparticles such as alumina oxide (Japanese Patent Laid-Open No. Hei 6-64034, 6-143409) is known.

However, the polyethylene terephthalate film obtained by the conventional technique described above can obtain a good elastic modulus, heat resistance, mechanical strength, and chemical properties, but can produce a film having sufficient surface smoothness for high-density magnetic recording, and excellent running and winding properties. There was no. Therefore, an object of the present invention is to provide a biaxially oriented polyethylene terephthalate film for a high density magnetic recording medium which can satisfy both running and brittleness as well as excellent surface smoothness when producing a polyethylene terephthalate film.

The present inventors have studied to solve these problems. Substantially spherical silica having an average particle diameter of 0.05-0.5 탆 dispersed by adding 0.05-10% by weight of cumylphenylacetate ester as the first component in a polyester in which at least 80 mol% of the chemical structural repeating unit is made of ethylene terephthalate. Calsite having an average particle diameter of 0.1-2.0 μm by adding 0.05-1.0 wt% of particles and surface-treated with a high molecular polycarboxylic acid copolymer composed of polyacrylic acid, ammonium polyacrylate, and ammonium polymethacrylate as a second component A biaxially oriented polyester film made of a polyester resin was prepared by adding 0.005-0.5% by weight of hexahedral calcium carbonate particles, wherein the content of the first component is between 2 and 20 times the content of the second component. In this case, the silica particles as the first component are those dispersed by cumyl phenyl acetate ester represented by the following formula,

The calcitic hexagonal calcium carbonate particles as the second component are surface-treated with a polymer polycarboxylic acid copolymer represented by the following formula,

By using the following formula

(D25, D50, and D75 are the percentages of the cumulative weight, respectively, and mean the particle diameters (μm) when they correspond to 25%, 50%, and 75% of the total.)

The centerline average roughness (SRa) of the produced film is 0.005-0.015µm, the number of projections having a height of 0.05µm or more per unit area (mm ² ) is 100-1,000, and the height of the unit area (mm ² ) is 0.01- The present invention was completed by satisfying that the number of protrusions having a thickness of 0.05 μm was 2,000-6,000.

Hereinafter, the present invention will be described in detail.

The polyester used in the present invention is made mainly from aromatic dicarboxylic acids such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, or esterification thereof and ethylene glycol as starting materials, but may include another third component. have. At this time, the dicarboxylic acid component of the starting material of the present invention is isophthalic acid. Terephthalic acid, 2,6-naphthalenedicarboxylic acid, phthalic acid, adipic acid, sebacic acid. Such acid components may be used alone or in combination of two or more. In the present invention, polyester having 80% or more of the repeating structural units composed of ethylene terephthalate is better.

The polyester in the present invention may include additives such as heat stabilizers, antiblocking agents, antioxidants, antistatic agents, ultraviolet absorbers, and the like.

The biggest feature of the present invention is that by adding a specific amount of small silica having excellent dispersibility to the polyester film, there is no coarseness due to the aggregation of particles, and fine protrusions are formed on the surface of the film, so that the film When rubbing with a metal roll to prevent the blocking phenomenon and adhesion shape due to the increase of the friction coefficient, it is possible to exhibit excellent electron conversion characteristics when made of a low-light film made of magnetic tape. In addition, the high projection formed from the calcitic hexahedral calcium carbonate particles having a uniform particle size distribution exhibits excellent running properties in the film manufacturing process, and can solve problems such as wrinkles and cross-sections, which are problems in winding a low-light film.

In order to improve the properties of the polyester film or magnetic tape described above, 0.05-1.0% by weight of substantially spherical silica particles having an average particle diameter of 0.05-0.5 µm was added as the first component in the polyester, but the average particle diameter was smaller than 0.05 µm. If it is difficult to form fine protrusions on the film surface, coarse protrusions are aggravated by aggregation. In addition, when the average particle diameter is larger than 0.5 mu m, it is difficult to control the surface roughness of the film to 0.015 mu m or less, which is not suitable for use as a high density magnetic recording medium. Preferably the average particle diameter is in the range of 0.1-0.4 탆. If the content of the first component is less than 0.05% by weight, a sufficient number of small protrusions may not be formed. If the content of the first component is more than 1.0% by weight, the surface roughness is increased to decrease the electron conversion characteristics. It is preferable to add 0.005-0.5% by weight of calcitic hexahedral calcium carbonate particles having an average particle diameter of 0.5-2.0 μm as the second component, and when the average particle diameter is smaller than 0.5 μm, it is difficult to form large protrusions on the film surface. When running property worsens and an average particle diameter is larger than 2.0 micrometers, surface roughness improves.

Preferably the average particle diameter is in the range of 0.6-1.2 μm. When the content of the second component is less than 0.005% by weight, it is impossible to form a large number of protrusions, resulting in poor running characteristics, and when the content of the second component is less than 0.5% by weight, surface roughness is increased to decrease the electron conversion characteristics. The content of the first component is preferably between 2 and 20 times the content of the second component, and more preferably between 5 and 10 times. If it is less than 2 times, the ratio of the larger projection becomes larger and the electronic characteristic is lowered. If it is 20 times or more, the ratio of the larger projection becomes smaller and the running performance is poor.

Silica particles as the first component is used by dispersing by adding 0.05-10% by weight cumylphenyl acetate ester represented by the following formula,

In the silica dispersion treatment method, 5-30% by weight of silica having an average particle diameter of 0.05-0.5 μm is added to ethylene glycol, and 0.05-10% by weight of cumylphenyl acetate ester is added to the silica. If the amount of cumylphenyl acetate ester to silica is less than 0.05% by weight, the dispersibility of the silica is not exerted. If the amount is more than 10% by weight, the resulting poly-polymer is produced due to side reactions. Change the color of the ester. If the silica dispersion treatment temperature is less than 40 ° C, it does not mix well with ethylene glycol and cumylphenyl acetate ester, and thus the silica dispersibility is not improved, and if it exceeds 150 ° C, it is economically disadvantageous. The mechanism of improving dispersibility of cumylphenyl acetate ester in the present invention is not clearly known, but the silanol group is blocked by silanol group, cumylphenyl acetate ester, which is a hydroxyl group present on the surface of silica particles, thereby blocking the hydrophilicity of the surface of silica particles. It is expected that the reduction will improve the dispersibility of the silica. The silica-ethylene glycol slurry thus treated is excellent in dispersibility even when added at any point in the esterification reaction or transesterification reaction during the polymerization of polyester.

As the second component, the calcitic hexahedral calcium carbonate particles are surface-treated with a polymer polycarboxylic acid copolymer represented by the following formula,

In general, the surface treatment method has sufficient surface treatment for a new surface having high surface energy generated by grinding by adding a surface treatment agent or grinding during the process of grinding the calcium carbonate particles synthesized by the carbonation reaction to a specific particle size. In this way, the surface treating agent is effectively attached to the whole particle. Although the addition amount of a surface treating agent does not have a restriction | limiting in particular, 0.1-5 weight% is preferable with respect to a particle total amount. Less than 0.1% by weight is often insufficient for the surface treatment effect, and when it is more than 5% by weight, aggregation between particles and aggregation of the surface treatment itself are likely to occur.

If the particle size distribution ratio (D25 / D75) of the calcium carbonate particles as the second component is less than 2.0, preferably between 1.1-1.9 is more preferable. When the distribution ratio is 2.0 or more, coarse protrusions exceeding 0.50 μm in height appear on the surface of the film, and the magnetic material is applied or deposited on the film roll, and the surface roughness is increased to increase the surface roughness. Becomes

The centerline average roughness of the film according to the invention is preferably in the range of 0.005 µm to 0.015 µm, and more preferably in the range of 0.007 µm to 0.013 µm. If the average roughness is less than 0.005㎛, the coefficient of friction of the film becomes high, and when used as a magnetic recording tape, the running characteristics become poor. If the average roughness exceeds 0.015㎛, the smoothness of the surface of the film is deteriorated. When this happens, the electron conversion characteristics deteriorate. In order to satisfy the smoothness and the activity of the film at the same time, the average surface roughness of the film satisfies the above range, and the distribution of the projections should be appropriate. In the present invention, the number of projections having a height of 0.05 μm or more per 1 mm 2 of the film surface (SP1) ) Is from 100 to 1,000. Although the surface roughness of the film satisfies the range of 0.005-0.015 µm, the object of the present invention cannot be achieved if the number of protrusions per unit area does not satisfy the above range. That is, when the number of SP1 is less than 100, if the film activity becomes poor, when the number exceeds 1,000, the smoothness decreases. In addition, the polyester film of the present invention is such that the number (SP2) of the projections having a height of 0.01-0.05㎛ is 2,000-6,000. Small projections serve to improve the driving performance that large projections do not sufficiently satisfy. When SP2 exceeds 6,000, surface roughness rises and the electronic conversion characteristics are poor when used as a magnetic recording medium.

In the present invention, the measurement of each property and various physical properties was measured by the following method.

(1) particle size

The average particle diameter of the particle slurry was measured using a particle size distribution analyzer (ZETASIZER 4 manufactured by MALVERN Co., Ltd.), and the particle size on the film was measured by using an electron microscope. In this case, the average particle diameter of the particles was 50% of the volume fraction of the particles. It was made.

(2) Film's center line average surface roughness: SRa

Centerline average roughness was measured using a 3D surface roughness meter manufactured by KOSAKA, Japan.

(3) Number of protrusions (mm2) per unit area: SPI and SP2

The number of protrusions was measured on the basis of the center line per unit area of film (mm 2) from the three-dimensional surface roughness curve obtained when the center line average surface roughness (SRa) of the film was measured.

(4) runability of film

The film cut to 1/2 inch in width is brought into contact with a commercially available guide pin at a 150 ° angle and travels at a speed of 7.5 cm per second. The tension T0 of the inlet is adjusted to 50 g, and the film detects the 1 m string tension T1, and the coefficient of friction of the film is obtained according to the following equation.

UK = (2.303 / θ) LOG (T0 / T1)

Then, after the film was reciprocated 100 times, the friction coefficient was measured in the same manner, and ΔUK, which is a difference from the initial friction coefficient, was calculated as follows.

Level 1: △ UK0.05 or less Level 2: △ UK0.05∼0.10

Level 3: △ UK 0.10 to 0.15 Level 4: △ UK 0.15 to 0.20

Level 5: △ UK 0.20 or higher

(5) bifunctional

The polyester film was made of a roll tape of a predetermined width, and then fixed and contacted with a metal guide roll for running for a long time. Then, the degree of scratching on the surface of the film was observed under a microscope, and the percentage produced on the guide roll was visually observed to determine as follows.

Level 1: Almost no scratch on the film surface after friction with the 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) Evaluation of coarse protrusion on film surface

Using the multiple interference microscope, the film surface was counted as the number of coarse protrusions (number within a measurement area of 1 mm 2) exceeding 1 micrometer in height, and determined as follows.

1st class: 1-3, 2nd class: 4-6

Level 3: 7 ~ 9 Level 4: 10 or more

(7) winding

The polyester film was slit to a certain width, wound on a bobbin, and then wound state was visually inspected and determined as follows.

1st class: No cross section

2nd level: Slight phenomenon

Level 3: Severe cross-sectional phenomenon

(8) dropout

Using a conventional method, the magnetic film is coated on the surface of a biaxially oriented polyester film to produce a video tape, and then the optimum current is recorded as a five-step disparity signal on the video tape. A duration of 15 µsec or more was regarded as a dropout, measured continuously for 30 minutes, and averaged per minute, divided into grades A to D for evaluation.

A: less than 10 / min

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

C: 30 or more / min-less than 50 / min

D: 50 or more per minute

(9) VTR head output

The signal output using Songha Electric's NV-3700 type video deck was measured at a frequency of 4MHz with a synchroscope, and the relative value of 0dB of the blank was measured.

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

Examples 1-3

100 parts of dimethyl terephthalic acid, 0.03 parts of antimony trioxide dissolved in ethylene glycol and 0.03 parts of trimethyl phosphate were added to 70 parts of ethylene glycol, and the particles of the first and second components uniformly dispersed in ethylene glycol (the spherical silica as the first component particles were cumyl After dispersing with phenyl acetate ester and calcitic hexagonal calcium carbonate particles as second component particles, surface treated with polymer polycarboxylic acid copolymer), a predetermined amount was added according to the contents shown in Table 1, Methanol was distilled off and transesterification was performed.

Next, the condensation reaction was carried out to obtain a polyester chip. After drying, the resultant was extruded through an extruder to obtain an unstretched film. The stretched film was stretched 4.0 times in a longitudinal direction at 130 ° C., stretched 3.5 times in a transverse direction at 140 ° C., and thermally cured at 230 ° C. for 40 seconds to achieve thickness 14. A μm film was obtained. The physical properties of this oriented film were evaluated and the results are shown in Table 1, and the physical properties such as runability, active activity, coarsening, dropout, and VTR head output were excellent.

Comparative Examples 1 to 3

Except having changed the particle | grains of a 1st, 2nd component as shown in Table 1, it carried out by the same method as Example 1, and obtained the film, and the film physical property is shown in Table 1.

Table 1

As described above, in the present invention, when the polyester film is produced, a specific amount of silica particles and calcium carbonate particles having excellent dispersibility and specific particle diameters are added to form protrusions, and the average surface roughness and unit area of the film By adjusting the number and ratio of the projections to satisfy the appropriate range conditions, the conventional limitation is overcome, and when the film surface is extremely smooth and made of magnetic tape, it shows a polyester film that exhibits electronic conversion characteristics and has excellent running and winding properties. Can be.

Claims (5)

Substantially spherical silica having a mean particle size of 0.05-0.5 탆 dispersed by adding 0.05-10% by weight of cumylphenyl acetate acetate as the first component in a polyester composed of ethylene terephthalate having at least 80 mol% of the resin A calcitic form having an average particle diameter of 0.1-2.0 μm added with 0.05-1.0% by weight of particles and surface-treated with a polymer polycarboxylic acid copolymer composed of polyacrylic acid, polyammonium ammonium salt and polymethacrylate as a second component Biaxially oriented polyester for high-density magnetic recording medium made of polyester resin, characterized by adding 0.005-0.5% by weight of hexahedral calcium carbonate particles, wherein the content of the first component is between 2 and 20 times the content of the second component. film. The biaxially oriented polyester film according to claim 1, wherein the silica particles as the first component are dispersed with cumylphenyl acetate ester represented by the following formula. The biaxially oriented polyester film according to claim 1, wherein the calcitic hexahedral calcium carbonate particles as the second component are surface treated with a polymer polycarboxylic acid copolymer represented by the following formula. The biaxially oriented polyester film of claim 1, wherein the calcium carbonate particles as the second component satisfy the following formula. (D25, D50, and D75 are the percentages of the cumulative weight, respectively, and mean the particle diameters (μm) when they correspond to 25%, 50%, and 75% of the total.) The method according to claim 1, the center line average roughness (SRa) of the made film is 0.005-0.15㎛, the number of projections (SP1) having a height of 0.05㎛ or more per unit area (mm ² ) is 100-1,000 pieces, per unit area (mm ² ) Biaxially oriented polyester film, characterized in that the number (SP2) of the projections having a height of 0.01-0.05㎛ 2,000-6,000.