KR950004156B1 - Multilayer polyester film and methof of manufacturing the same - Google Patents

Abstract

A method for manufacturing the biaxial oriented polyester lamination film comprises: respectively extruding the polyster without inorganic filler and the polyester with inorganic filler in each extruder; forming two extruded polyester layers to a laminated sheet through a slit of dia; solidifing the laminated sheet on a roll for rapid-cooling; and heat-treating after biaxially stretching the solidified sheet. Specially, the ratio (An/An+B) of total thickness (An) of polyester layers without inorganic filler to that (B) of polyester with inorganic filler is adjusted in a range of 1-50%.

Description

Polyester multilayer film for magnetic recording medium and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester multilayer film for a magnetic recording medium and a method for manufacturing the same, and more particularly to magnetic recording using a ferromagnetic thin film such as magnetic tape, video, audio, and magnetic disk, which has improved slip and electronic properties. A base film for a medium and a manufacturing method thereof.

Among the polyesters, polyethylene terephthalate (hereinafter, abbreviated as PET) has good mechanical and chemical properties such as tensile strength, elastic modulus and impact strength, as well as physical and chemical properties such as heat resistance, durability, chemical resistance, and electrical insulation. Manufactured by biaxially oriented film, it is widely used in all fields of packaging, photographic film, magnetic recording media, and industrial use.

Particularly, these polyester films are widely used as base films for various magnetic recording media. However, since the surface is very smooth and the coefficient of friction is high, slipperiness is poor, so that blocking, scratching and static electricity are generated in the film manufacturing process, post-processing process, and magnetic material fixing process. Cause problems such as.

Therefore, as a method for imparting slip property to a polyester film, a method of coating or filling inert inorganic particles into a polymer as a lubricant has been used. However, in the case of coating, problems such as technical problems and productivity are lowered, and thus, protrusions are formed on the surface of the film by adding inert inorganic particles, thereby providing slip properties. The larger the size of the inorganic particles added here, the better the slip performance is, but the dropout of the magnetic recording medium is caused, resulting in poor electronic properties. If the size of the inorganic particles is too small, the electronic properties are good but the slip properties are not improved. In addition, when the inorganic particles are present in the polymer, when the fibers are stretched orientated, voids are formed around the particles. If the voids are generated near the surface of the film, some of the voids are destroyed during the production of the magnetic recording medium, and the particles stick out. Since it adheres to the surface, it not only degrades the performance of the magnetic recording medium, but also deteriorates the quality of the image due to contamination of the deck head with particles released by the voids generated by friction during driving of the magnetic recording medium.

As a method for simultaneously improving slip and electronic properties of the magnetic recording medium base film while preventing contamination by the dropped inorganic particles, there is a method using a laminated film having different surface roughness of both sides of the base film. For the production of such laminated peeling, a method using coextrusion is preferable. In other words, different polymers were melt-extruded from different extruders at 265 to 300 ° C, joined together, discharged onto sheets through a die on a sled, and rapidly amorphous-formed sheets obtained by quenching on a cooling roll at 10 to 50 ° C. Stretching at least 3 times in the longitudinal direction at ℃ and stretching at least 3 times in the orthogonal direction in the direction already stretched at 80 to 160 ℃, and then heat-treated at 160 to 250 ℃ for 2 to 10 seconds to give a biaxially oriented coextruded laminated film It can manufacture.

As a conventional technique using a laminated film, a film stretched by co-extrusion lamination of a polyester containing no inorganic filler and a polyester containing an inorganic filler (two layers having no different surface roughness) Layer A layer, layer B layer containing an inorganic filler). The surface roughness of the B layer is 50 kPa to 200 kPa depending on the particle size and the amount of the inorganic filler, the particle size of the inorganic filler is 10 to 300 nm, the amount of the additive is 0.01 to 1% by weight, and the thickness of the B layer is 5 times the particle diameter (day 62-290535), the thickness ratio of A and B two layers, A method of making x100 (%) less than 5% (Japanese Patent Laid-Open No. 62-502456) is disclosed. In addition, the thickness ratio of the layer A and layer B is drawn to the sheet (A, B is 11) of the layer B layer does not affect the surface roughness of the layer A, and then 50-1000 nm thick on the surface of the layer A with an inline coater. And a method of improving the slip properties of the A layer surface by applying a resin such as methyl cellulose and heat treatment (Japanese Patent Application Laid-Open No. 58-153640, 58-155940).

However, in the above-described vertical technology, since the A layer is very thick compared to the B layer, the A layer has a very low surface roughness and a flat surface regardless of the B layer, causing various problems in the film manufacturing process and the magnetic coating process. That is, in the stretching and winding process during the film manufacturing process, the slipperiness with the roll is poor, and problems such as scratching occur. In the winding process, the slipperiness of the film and the film is insufficient, so that the blocking problem occurs. It becomes bad. In addition, in the case of applying a specific resin on the surface of the layer A, the surface of the layer A may be bent to improve slip performance, but the inline coating process is complicated, and the production rate and yield are reduced, resulting in a decrease in productivity. .

On the other hand, when the inorganic filler is added to the A layer as in the B layer, the surface roughness of the A layer may be increased to solve some of the problems caused by the lack of slippage, but the added inorganic material may be used in the film forming and coating process. Dropping may contaminate the magnetic layer, and the dropped inorganic filler may contaminate the head while driving the magnetic tape, making it difficult to obtain good image and sound quality.

SUMMARY OF THE INVENTION The present invention provides a polyester laminated film for a magnetic recording medium having improved electronic properties by improving slipperiness by preventing surface dropping and preventing dropping of inorganic particles from the surface in view of the above problems, and a method of manufacturing the same. For the purpose of

In order to achieve the above object, in the present invention, polyester which does not contain an inorganic filler and polyester which contains an inorganic filler are melt-extruded in each extruder to be joined and discharged onto a sheet through a die on a slut, and cooled. A method for producing a biaxially oriented polyester laminated film by biaxially stretching an amorphous sheet obtained by rapid freezing on a roll and then heat-treating it, wherein the discharge amount of the polyester is controlled from each extruder so that at least one inorganic filler is not included. Polyester layer An layer (n is 1 or 2) and thickness ratio of one polyester layer B containing inorganic filler, (An layer thickness) / (An layer thickness + B layer thickness) of 1 to 45%, respectively And the draw ratio in each direction is 3 to 7 times. Provided.

That is, when co-extrusion and fusion lamination of two A / B sheets consisting of one polyester layer A layer without inorganic filler and one polyester layer B layer with inorganic filler as one aspect of the present invention, Unlike the conventional method, the thickness of the A layer is thinner than the B layer, that is, the thickness ratio, (A layer thickness) / (A layer thickness + B layer thickness) is 1 to 45%, unlike the conventional method by controlling the discharge amount by adjusting the rotation speed of the extruder. When the sheet is molded so as to be in the range of, and stretched at an appropriate ratio, the thin A layer exerts the effect of beating the surface of the thicker inorganic filler particles of the thicker B layer, thereby preventing the inorganic filler particles from being detached from the surface. Due to the influence of the inorganic filler particles aggregated on the surface of the A layer, a relatively gentle discontinuous curvature is formed, so that the surface roughness of the A layer is lower than that of the B layer, and the conventional A layer (when the thickness of the A layer is thicker than the thickness of the B layer). Than It can be obtained at a high level to improve the slip.

In another aspect of the present invention, A ₁ / B / A _{2 is} a form in which one polyester layer B layer including an inorganic filler is inserted between _two polyester layers A ₁ and A ₂ without the inorganic filler. In the case of co-extrusion melt lamination of the three-layer sheet, the thickness of both surfaces A ₁ and A ₂ is made thinner than the B layer by adjusting the number of rotations of each extruder to adjust the discharge amount, that is, the thickness ratio (A ₁ layer thickness) / Form the sheet so that (A1 layer thickness + B layer thickness) and (A ₂ layer thickness) / (A ₂ layer thickness + B layer thickness) are in the range of 1 to 45%, respectively, and adjust the draw ratio to achieve the desired surface roughness. It can be obtained, since in the effect that both surfaces of the polyester layer (B) layer contains the inorganic filler a ₁ layer and a ₂ layer is covered with the inorganic filler particles in the B layer surface is to be eliminated by the friction with the rotating rolls during running Can be prevented.

Here, the draw ratio may vary depending on the thickness of the A layer, but needs to be 3 to 7 times to obtain the effect of the present invention. When the draw ratio is less than three times, the thickness of the layer A is so thick that the aggregated particles of the layer B have little force to push the layer A, so that the surface roughness is low and the slipperiness cannot be improved as desired. Low strength and high elongation cause deformation due to the tension applied to the tape. On the other hand, when the draw ratio is greater than seven times, the thickness of the layer A becomes thinner, and the force of pushing the aggregated particles of the layer B into the layer A increases, causing the excessively protruding voids to be ruptured easily by friction, and the inorganic filler particles are released out of the contamination. In addition to the risk of stiffness, high-strength stretching results in high strength but high heat shrinkage, resulting in poor dimensional stability.

That is, the thickness ratio of the A layer and the B layer, (A layer thickness) / (A layer thickness + B layer thickness) should be in the range of 1 to 45%, preferably 5 to 35%, the draw ratio of 3 to 7 times It should be in the range and 3.5 to 5 times is preferred.

Inorganic fillers included in the B layer may be added one or two or more kinds, and inert inorganic metal oxides, sulfides, hydrates such as titanium dioxide, silicon dioxide, synthetic calcium carbonate, aluminum hydroxide, kaolin, talc, barium sulfate, etc. Compound particles may be included. The addition amount of these inorganic fillers is preferably 0.001 to 2.0% by weight of the total weight of the B layer, and the particle size of the particles is preferably 300 to 1000 nm. When the particle size is smaller than 300 nm, the effect of particles is insignificant, and it is difficult to bend the surface of the A layer even when stretching at high magnification.In the case of the two-layer film of A _l / B, the B surface where the magnetic body is coated causes adhesion to the head when driving. . On the other hand, when the particle size is larger than 1000 nm, it is easy to bend the surface of the A layer, but the bend itself becomes too wide and large, resulting in an increase in the contact area of the film, resulting in poor film-to-film and film-to-roll slippage, and A ₁ / B In the case of the two-layer film, the surface roughness of the B surface on which the magnetic material is coated is so high that the electronic characteristics of the magnetic tape are deteriorated and dropout phenomenon occurs.

Among the polyesters of the present invention, PET is ideally a PET obtained by polycondensation of at least 80% by weight of dimethyl terephthalate and ethylene glycol, and may be a homopolyester or a copolyester. In the case of copolyester, it may be copolymerized with diol components such as dimethylene glycol, propylene glycol, neopentylene glycol, polyethylene glycol, 1,4-cyclohexanedimethanol, and the copolymerization ratio is preferably 25% or less. The polycondensed polyester has a limit of 0.4 to 1.0 dl / g, more preferably 0.5 to 8 dl / g, of 0.3g concentration sample at 25 ° C. per 25 m1 of orthochlorophenol.

Polyester A without an inorganic filler and Polyester B with an inorganic filler are melt-extruded from each extruder at 265 ° to 300 ° C., then joined before the die on the slits to form a sheet through the die, or It is also possible to join in the die and discharge the sheet.

The discharged sheet was quenched and solidified on a cooling roll at 100 to 50 ° C. to obtain an amorphous sheet, which was stretched 3 to 7 times in the longitudinal direction at 80 ° to 160 ° C., and then stretched in the direction already stretched at 80 ° to 160 ° C. After stretching 3 to 7 times in the orthogonal direction, heat treatment is performed at 160 to 250 ° C. for 2 to 10 seconds to obtain a biaxially cultured polyester laminated film.

The stretching method may be either successive biaxial stretching or simultaneous biaxial stretching. In order to obtain a desired surface roughness on the surface of the A layer, proper adjustment of the draw ratio according to the amount and particle size of the inorganic filler particles added and the thickness ratio of the A layer and the B layer becomes an important factor.

By the above method, the film thickness 6-16㎛, longitudinal and lateral strength of 25kg / ㎜ or more, elongation 200% or less, the average roughness (Ra) value in the surface roughness of A / B two layers, A base film for magnetic recording media of three layers of A ₁ / B / A ₂ was prepared.

According to the manufacturing method of the present invention as described above, in the laminated stretched film of the polyester containing no inorganic filler and the polyester containing the inorganic filler, at least one polyester layer An layer (n) containing no inorganic filler The thickness ratio of 1 or 2) silver and one layer of the polyester layer containing the inorganic filler, (An layer thickness) / (An layer thickness + B layer thickness) is characterized in that in the range of 1 to 45%, respectively A polyester ester laminated film for a recording medium is provided.

One aspect of the polyester laminated film of the present invention, one polyester layer A layer containing no inorganic filler and one polyester layer B layer containing inorganic filler A / B two layer polyester In the laminated film, the average roughness of the center line of the surface of the layer A was 0.01 to 0.025 µm, the number of peaks of the surface projections was 3x102 to 3x103./mm2, and the centerline flat roughness of the surface of the layer B was 0.025 to 0.15 µm. It is characterized by the number of peaks of 3 x 10 < 3 >

Does not contain a poly-S, another aspect of the Der laminated film, the inorganic filler of the present invention two of the polyester layer A _l, A consisting of a polyester layer B layer comprising a A ₂ layer and the inorganic filler, ₁ / in the B / a three layer ₂ of the polyester laminate film (provided that where a ₁ and a ₂ are the same or may be different), a center line average roughness of 0.01 to 0.025㎛ of the _first layer 3 and the surface number of a surface protrusion peaks It is characterized by having a size of 102 x 3 to 10 3 / mm ₂ , a center line average roughness of the surface of the A ₂ layer of 0.015 to 0.09 µm, and a number of peaks of the surface projections of 1 x 10 3 to 1 x 10 5 / mm 2.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

Each measurement in an Example and a comparative example is measured according to the following measuring method.

(How to measure)

The center line average roughness Ra of the surface roughness was measured with a three-dimensional roughness meter. The measurement method is a value obtained by shooting a light ray on the surface of a film sample and measuring the shape of the measurement surface with light rays reflected from the surface, and calculating the centerline average of the measured bends. The number of peaks (pieces / mm 2) is a value obtained by measuring the number of protrusions of the bend 1 nm or more higher than the average height of the surrounding four points within 1 mm 2 of the sample surface measured by the same method as above.

The measurement of the scratch is a value obtained by winding a film prepared by stretching and heat setting the coextruded sheet, slitting the sample slightly, taking a sample, and measuring a scratch generated in a 100 cm 2 area by a polarizing optical microscope. In other words, the film surface is damaged due to the lack of slip with the roll during the roll manufacturing process. The S / N ratio and dropout of the magnetic tape characteristics are signals from the TVE test signal generator. And measured using a video noise meter dropout counter. The video S / N ratio was measured using a commercially available 8MM video metal tape at zero level (db). Dropout is measured based on a change in playback signal of 20 db or more and a length of 5 microns or more.

In the present invention, the thickness measurement of each layer of the coextruded film was measured by an electron microscope after cutting the film cross section with a microtome. And the size of the inorganic filler particles is a value measured using a Coulter counter.

The examples are carried out separately for A / B two layers of polyester laminated film (1) and A ₁ / B / A _two three layers of polyester laminated film (2).

(1) A / B two layer polyester laminated film

(Example 1)

Polyester A, which does not contain an inorganic filler, and Polyester B, in which 0.05 wt% of an inorganic filler having a particle size of 500 nm were added, were melt-extruded at 290 ° C. from different extruders, respectively, merged in a die, and discharged from a die. Was quenched on a 35 ° C. chill roll to form a sheet. The sheet is stretched 3.5 times in the longitudinal direction at 85 ° C., then cooled to 30 ° C., and then stretched 4.2 times in the transverse direction at 90 ° C. After heat treatment at 230 ° C. for 5 seconds, the sheet is wound and wound up to A layer thickness of 2 μm and B layer thickness. A total of 12 μm, a total of 14 μm, a coextruded polyester laminate is obtained.

Cobalt and an iron alloy thin film were apply | coated to this polyester base film A layer surface, and the silicon protective film layer was formed on it. And carbon black was apply | coated to the surface of B layer with an epoxy resin, the back coat layer was formed, and the magnetic tape was produced.

The characteristics of the base film and the magnetic tape of the two A / B layers are shown in Table 1.

(Example 2)

Perform the same method as in Example 1, but by controlling the discharge amount of each extruder to form a sheet by controlling the thickness of the temporary layer and stretched 4 times in the longitudinal direction, 4.5 times in the transverse direction to the thickness of the layer A 3㎛ B A total of 14 μm base films with 11 μm thickness were made.

The characteristics of the base film and the magnetic tape of the two A / B layers are shown in Table 1.

(Example 3)

A base film was prepared by the same method as Example 2, but adding 0.1 wt% of an inorganic filler having a particle size of 350 nm.

The characteristics of the base film and the magnetic tape of the two A / B layers are shown in Table 1.

(Example 4)

A base film was prepared by the same method as Example 1, but adding 0.1 wt% of an inorganic filler having a particle size of 350 nm.

The characteristics of the base film and the magnetic tape of the two A / B layers are shown in Table 1.

(Comparative Example 1)

Perform the same method as in Example 1, but by controlling the discharge amount of each extruder to form a sheet by controlling the thickness of each layer and stretched 3.5 times in the longitudinal direction, 4.2 times in the transverse direction to the thickness of the layer A 7㎛ B A total of 14 μm base films with 7 μm thickness of layers were made.

The characteristics of the base film and the magnetic tape of this A / B free layer are shown in Table 1.

(Comparative Example 2)

Perform the same method as Comparative Example 1 except that by controlling the discharge amount of each extruder to control the thickness of each layer to form a sheet and stretched 4 times in the longitudinal direction, 4.5 times in the transverse direction to the thickness of the layer A 7㎛, A total of 14 µm base films having a thickness of B layer of 7 µm were made.

The characteristics of the base film and the magnetic tape of the two A / B layers are shown in Table 1.

(Comparative Example 3)

Perform the same method as Comparative Example 2, but by controlling the discharge amount of each extruder to form a sheet by controlling the thickness of each layer and stretched 4 times in the longitudinal direction, 4.5 times in the transverse direction to the thickness of the layer A 12㎛, A total of 14 µm of base film having a thickness of B layer of 2 µm was made.

The characteristics of the base film and the magnetic tape of the two A / B layers are shown in Table 1.

(Comparative Example 4)

Perform the same method as Comparative Example 1, but by controlling the discharge amount of each extruder to form a sheet by controlling the thickness of each layer and stretched 3.5 times in the longitudinal direction, 4.2 times in the transverse direction l4㎛, A total of 14.5 μm of base film having a thickness of B layer of 0.5 μm was made.

The characteristics of the base film and the magnetic tape of the two A / B layers are shown in Table 1.

(2) Polyester laminated film of A ₁ / B / A ₂ three layers

(Example 1)

Polyester A ₁ containing no inorganic filler, Polyester B containing 0.05% by weight of inorganic filler having a particle size of 500 nm, and polyester A ₂ identical to polyester A ₁ containing no inorganic filler were respectively added from different extruders. ℃ standing after melt extrusion was joined in the die before quenching the polymer of the ronghae discharge, a ₁ / B / a ₂ three layer die from the top of a 35 ℃ cooling roll to form a sheet.

The sheet is stretched 3.5 times in the longitudinal direction at 85 ° C., then cooled to 30 ° C. and stretched 4.2 times in the transverse direction at 90 ° C. again. After a heat treatment at 230 ℃ 5 chogan wine Turning to A _l 2㎛ thickness of layers and obtain the co-extrusion of the polyester laminate film layer having a thickness of B layer 14㎛ the 11㎛, A is 1㎛ ₂ layer thickness.

Cobalt and an iron alloy thin film were apply | coated on the surface of this polyester base film A layer, and the silicon protective film layer was formed on it. And by applying the epoxy resin to the carbon black to the surface of the layer A ₂ to form a back coat layer was fabricated in a magnetic tape.

The base film and the characteristics of the magnetic tapes of _l A / B / A _2, three layers are shown in Table 2.

(Example 2)

Perform the same method as in Example 1, but by controlling the discharge amount of each extruder to form a sheet by controlling the thickness of each layer and stretched 4 times in the longitudinal direction, 4.5 times in the transverse direction to the thickness of the A ₁ layer 3㎛ , he made a base film of the total thickness of the 14㎛ that 1㎛ 10㎛, a ₂ layer to the thickness of the B layer.

The base film and the characteristics of the magnetic tapes of _l A / B / A _2, three layers are shown in Table 2.

(Example 3)

A base film was prepared by the same method as Example 2, but adding 0.1 wt% of an inorganic filler having a particle size of 350 nm.

The characteristics of the base film and the magnetic tape of the A ₁ / B / A 2 three guns are shown in Table 2.

(Example 4)

A base film was prepared by the same method as Example 1, but adding 0.1 wt% of an inorganic filler having a particle size of 350 nm.

The base film and the characteristics of the magnetic tapes of _l A / B / A _2, three layers are shown in Table 2.

(Comparative Example 1)

Example 1 The synthesis was carried out as then to adjust the thickness of each layer by adjusting the discharge amount of each extruder, molding the sheet 3.5 times in a longitudinal direction, the 7㎛ 4.2 times stretched in the transverse direction thickness of the layer A _l The base film of 14 micrometers in total which made thickness of B layer 5 micrometers and A2 layer ₂ micrometers was created.

The base film and the characteristics of the magnetic tape ₁ in the A / B / A three layer ₂ is shown in Table 2.

(Comparative Example 2)

Perform the same method as Comparative Example 1, but by controlling the discharge amount of each extruder to control the thickness of each layer to form a sheet and stretched 4 times in the longitudinal direction, 4.5 times in the transverse direction to the thickness of the A ₁ layer 7㎛ The base film of 14 micrometers in total which made thickness of B layer 5 micrometers and A2 layer ₂ micrometers was created.

The base film and the characteristics of the magnetic tape ₁ in the A / B / A three layer ₂ is shown in Table 2.

(Comparative Example 3)

The comparative example 2 The synthesis was carried out as in A _l and dukkye layer by adjusting the thickness of each layer by adjusting the discharge amount of each extruder 10㎛, the thickness of the B layer 3㎛, A in the 1㎛ dukkye a _two-layer A base film of 14 μm in total was made.

The base film and the characteristics of the magnetic tape ₁ in the A / B / A three layer ₂ is shown in Table 2.

(Comparative Example 4)

Comparative Example 1 The synthesis was carried out as the layer thickness of the A _l by adjusting the thickness of each layer by adjusting the discharge amount of each extruder 3㎛, the thickness of the B layer was 11㎛, 0.1㎛ the thickness of the layer A ₂ A total of 14.1 μm of base film was made.

The base film and the characteristics of the magnetic tape ₁ in the A / B / A three layer ₂ is shown in Table 2.

TABLE 1

TABLE 2

The polyester base film and the magnetic tape prepared through the above examples showed excellent base film properties and magnetic properties in the case of two layers of A / B and three layers of A ₁ / B / A _{2 as a} result of performance measurement.

That is, the polyester laminated film of the present invention exhibits the effect of covering the thick B layer including the inorganic filler particles with A / B or A ₁ / B / A ₂ with a thin A layer containing no inorganic filler particles. When the sheet is stretched, the inorganic filler aggregated particles of the B layer affect the A layer to form relatively gentle discontinuous bends on the surface of the A layer, and the height of the bend depends on the thickness ratio and the draw ratio of the A / B layer. Can be adjusted to obtain the desired surface roughness. Therefore, in the present invention, since the surface of the A layer does not contain an inorganic filler, it is possible to prevent various contaminations due to the dropping of the inorganic filler, and to give the surface a controllable degree of curvature, thereby increasing the film size in the film manufacturing process and the coating process. Slip and film-to-film slip properties can be improved to prevent scratches and blocking and to prevent static buildup.

Claims (12)

The polyester sheet containing no inorganic filler and the polyester containing inorganic filler are melt-extruded in each extruder, joined together, discharged onto a sheet through a die of a slitter form, and the amorphous sheet obtained by rapid freezing on a cooling roll is biaxially stretched. In the method for producing a biaxially oriented polyester laminated film by a soft treatment, at least one polyester layer An layer (n is 1 or 1) containing no inorganic filler by adjusting the discharge amount of the polyester from each extruder 2) and (A layer thickness) / (An layer thickness + B layer thickness) of one polyester layer B layer containing an inorganic total agent, respectively, in the range of 1 to 45%, A method for producing a polyester laminated film for magnetic recording media, characterized by a draw ratio of 3 to 7 times. The method of claim 1, wherein the A / B two-test polyester laminated film, characterized in that composed of one polyester layer A layer not containing an inorganic charger and one polyester layer B layer containing an inorganic filler. Way. According to claim 1, being configured for a polyester comprising two polyester layers A _l, A ₂ layer and inorganic filler does not contain the inorganic filler in the layer B-layer, it characterized Ma A _l / B / A2 Process for producing three layers of polyester laminated film, where A ₁ and A ₂ may be the same or different (A middle thickness) / (An layer thickness + B layer thickness) are 5 to 35% of range, respectively, The manufacturing method of the polyester film of any one of Claims 1-3 characterized by the above-mentioned. The method of claim 4, wherein the draw ratio is 3.5 to 5 times. The polyester laminated film according to any one of claims 1 to 3, wherein the amount of the inorganic filler included in the polyester layer B layer containing the inorganic filler is 0.001 to 2.0% by weight of the total weight of the B layer. Manufacturing method. The method for producing a polyester laminated film according to claim 6, wherein the particle diameter of the inorganic filler particles included in the polyester layer B layer containing the inorganic filler is 300 to 1000 nm. In the laminated stretched film of polyester not containing an inorganic filler and polyester comprising an inorganic filler, at least one polyester layer An layer 하지 not containing an inorganic filler is 1 or 2) and one containing an inorganic filler. The thickness ratio of the polyester layer B layer of (A layer thickness) / (An layer thickness + B layer thickness) is 1 to 45% of each, The polyester laminated film for magnetic recording media characterized by the above-mentioned. The polyester laminated film of claim 8, wherein the polyester laminate film A / B is composed of one polyester layer A layer not containing an inorganic filler and one polyester layer B layer containing an inorganic filler. 9. A ₁ / B / A ₂ according to claim 8, characterized in that it is composed of two polyester layers A ₁ , A ₂ layers not containing inorganic filler and one polyester layer B layer containing inorganic filler. Three layers of polyester laminated film, where A ₁ and A ₂ may be the same or different. 10. The method according to claim 9, wherein the center line Ping coarse roughness of the A ₁ layer surface is 0.01 to 0 025 µm and the number of peaks of the surface projections is 3 × 10 ² to 3 × 10 ³ / mm 2, and the center line average roughness of the B layer surface is 0.025 to A polyester laminated film of two layers A / B, characterized in that 0.15㎛ and the number of peaks of the surface projections 3 × 10 ³ ~ 1 × 10 ⁶ / ㎣. 11. The method of claim 10, A _l center line average roughness of the surface layer. The number of 0.01 and a surface protrusion peaks 0.025㎛ 3 × 10 ² to ³ × 10 3 gae, / ㎟ said, A is the center line average roughness of the _second layer is greater 0.015 0.09 占 퐉 and the number of surface projection peaks is 1 × 10 ³ to 1 × 10 ⁵ / mm ₂ A ₁ / B / A ₂ three-layer polyester laminated film characterized by the above-mentioned.